JP2016164557A - Surface shape measurement device and surface shape measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface shape measurement device and a surface shape measurement method with which it is possible to measure the surface shape (three-dimensional shape) of a surface to be measured with high sensitivity and with high accuracy even when reflective indices are not uniform as in the case where the surface to be measured of a measurement object has a complex shape.SOLUTION: A surface shape measurement device 1 acquires each of at least a first interference image whose luminous energy is relatively large and a second interference image whose luminous energy is relatively small from an image-capturing unit 16 by controlling the operation of a light source unit 12, finds a plurality of interferograms for each point of the surface to be measured on the basis of each of the first interference image and the second interference image, selects an interferogram within a preset measurement range for each point from the plurality of interferograms, and detects the position in the optical axial direction of each point on the surface to be measured on the basis of the selected interferogram for each point.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface shape measuring apparatus and a surface shape measuring method, and in particular, surface shape measurement for measuring a three-dimensional shape of a measurement target surface in a non-contact manner using a scanning white interferometer that uses white light as a light source. The present invention relates to an apparatus and a surface shape measuring method.

  The surface shape measuring device is a device for measuring a three-dimensional shape of a measurement target surface of a measurement object, and one using a scanning white interferometer is known.

  As described in Patent Document 1, the scanning white interferometer uses white light having a wide wavelength width (low coherence light with low coherence) as a light source, and uses a Michelson type or Millow type interferometer. It is used to measure the three-dimensional shape of the surface to be measured of the measurement object in a non-contact manner.

  As described in Patent Document 1, the Michelson-type scanning white interferometer illuminates the surface to be measured with the Michelson-type interferometer arranged to face the surface to be measured of the measurement object (sample). A white light source that emits white light and a CCD camera that captures the interference light generated by the Michelson interferometer are provided.

  The Michelson interferometer includes an objective lens as a component of an optical microscope, a beam splitter disposed between the objective lens and a surface to be measured, and a reference mirror. White light incident on the Michelson interferometer from the white light source passes through the objective lens and is divided into object light and reference light by the beam splitter, the object light is irradiated on the surface to be measured, and the reference light is irradiated on the reference mirror. Is done. The object light returning from the surface to be measured and the reference light returning from the reference mirror are superimposed to generate interference light, which passes through the objective lens and is emitted from the Michelson interferometer to the CCD camera.

  Thereby, an interference image is formed on the imaging surface of the CCD camera, and the interference image is acquired as an interference image by the imaging device of the CCD camera. The interference image is sequentially acquired while the Michelson interferometer is displaced in the height direction with respect to the surface to be measured, and an interferogram (interference fringe) for each point (pixel) on the surface to be measured is obtained from the acquired interference image. Curve) and the relative height of each point on the surface to be measured is measured based on the interferogram for each point.

JP 2013-19767 A

  By the way, in the scanning white interferometer as described above, when the reflectivity is not constant, such as when the measurement target surface of the measurement object has a complicated shape such as a flat portion and a slope portion, If the amount of white light emission is adjusted so as to be appropriate at a location with a high rate, the waveform amplitude of the interferogram at a location with a low reflectivity may be small, and measurement may not be performed correctly. Conversely, if the amount of white light emitted is adjusted so that it is appropriate at locations with low reflectivity, the interferogram at locations with high reflectivity will be saturated (ie, exceeding the preset measurement range). Measurement may not be performed correctly.

  The present invention has been made in view of such circumstances, and even when the reflectance is not constant as in the case where the surface to be measured of the measurement object has a complicated shape, the surface shape (3 An object of the present invention is to provide a surface shape measuring apparatus and a surface shape measuring method capable of measuring (dimensional shape) with high sensitivity and high accuracy.

  In order to achieve the above object, a surface shape measuring apparatus according to a first aspect of the present invention includes a light source unit that emits white light, and the white light from the light source unit is divided into object light and reference light. An interference unit that generates interference light by irradiating the measurement target surface of the measurement object and causing the object light returning from the measurement surface to interfere with the reference light, and the optical axis direction of the object light with respect to the measurement target. A scanning unit that moves relative to the imaging unit, an imaging unit that captures interference light from the interference unit and generates an interference image using the interference light, and a scanning unit that moves the interference unit relative to the measurement target in the optical axis direction. Interferograms are sequentially acquired from the imaging unit while being moved to, and an interferogram for each point of the measured surface is obtained based on the acquired interference image, and each of the measured surfaces is determined based on the interferogram for each point. A processing unit for detecting the position of the point in the optical axis direction, a light source unit or an imaging A control unit that controls the operation of the image processing unit, and the processing unit controls the operation of the light source unit or the image capturing unit by the control unit, thereby relative to the first interference image having a relatively large amount of light from the image capturing unit. And obtaining a plurality of interferograms for each point based on each of the first interference image and the second interference image, and from among the plurality of interferograms. An interferogram within a preset measurement range is selected for each point, and the position in the optical axis direction of each point on the measured surface is detected based on the selected interferogram for each point.

  In the surface shape measuring apparatus according to the second aspect of the present invention, in the first aspect, when there are a plurality of interferograms within the measurement range, the processing unit determines the waveform amplitude from the interferogram within the measurement range. Select the interferogram with the largest maximum value.

  In the surface shape measurement apparatus according to the third aspect of the present invention, in the first aspect or the second aspect, the processing unit controls the measurement condition for the measurement object by controlling the operation of the light source unit or the imaging unit by the control unit. The measurement object is measured multiple times, multiple interferograms are obtained for each point by multiple measurements, and an interferogram within a preset measurement range is selected from the multiple interferograms. A ferrogram is selected for each point, and the position in the optical axis direction of each point on the surface to be measured is detected based on the interferogram for each selected point.

  In the surface shape measurement apparatus according to the fourth aspect of the present invention, in the third aspect, the measurement condition is the amount of white light emitted from the light source unit.

  In the surface shape measuring apparatus according to the fifth aspect of the present invention, in the third aspect or the fourth aspect, the measurement condition is at least one of a gain of the imaging unit, an exposure time, and an aperture value.

  In the surface shape measuring apparatus according to the sixth aspect of the present invention, in the first aspect or the second aspect, the light source unit has a pulse light source that emits pulsed white light, and the control means emits light and images the pulse light source. Control is performed so that the image acquisition of each part is periodically performed while maintaining a certain correlation.

  In the sixth aspect of the surface shape measuring apparatus according to the seventh aspect of the present invention, the light emission period of the pulsed light source is longer than the image acquisition period of the imaging unit, and the light emission time per period of the pulsed light source is 1 of the imaging unit. It is longer than the image acquisition time per cycle.

  In the surface shape measuring apparatus according to the eighth aspect of the present invention, in the seventh aspect, the light emission period of the pulse light source is twice the image acquisition period of the imaging unit.

  A surface shape measurement method according to a ninth aspect of the present invention includes a light source unit that emits white light, and the white light from the light source unit is divided into object light and reference light so that the object light is measured on the surface to be measured. An interference unit that generates interference light that interferes with the object light returning from the measurement surface and the reference light, and scanning that moves the interference unit relative to the measurement target in the direction of the optical axis of the object light. An imaging unit that captures interference light from the interference unit and generates an interference image by the interference light, and from the imaging unit while moving the interference unit relative to the measurement object by the scanning unit in the optical axis direction. Interferograms are acquired sequentially, an interferogram for each point on the measured surface is obtained based on the acquired interference image, and the position of each point on the measured surface in the optical axis direction is determined based on the interferogram for each point. And a control unit that controls the operation of the light source unit or the imaging unit. A surface shape measuring method in a surface shape measuring apparatus comprising: a step; relative to a first interference image having a relatively large amount of light from the imaging unit by controlling an operation of the light source unit or the imaging unit by a control unit; And obtaining a plurality of interferograms for each point based on the first interference image and the second interference image, respectively, and a plurality of interferograms. A selection step for selecting an interferogram within a preset measurement range for each point, and the optical axis direction of each point on the surface to be measured based on the interferogram for each point selected in the selection step And a detecting step for detecting the position of.

  The surface shape measuring apparatus according to the tenth aspect of the present invention is the surface shape measuring apparatus according to the ninth aspect, wherein the selecting step includes the step of measuring the waveform amplitude from the interferogram within the measurement range when there are a plurality of interferograms within the measurement range. Select the interferogram with the largest maximum value.

  In the surface shape measuring apparatus according to the eleventh aspect of the present invention, in the ninth aspect or the tenth aspect, the acquisition step sets the measurement conditions for the measurement object to each other by controlling the operation of the light source unit or the imaging unit by the control unit. A plurality of measurements are performed on an object to be measured in a different manner, and a plurality of interferograms are obtained for each point by a plurality of measurements.

  In the surface shape measuring apparatus according to the twelfth aspect of the present invention, in the eleventh aspect, the measurement condition is the amount of white light emitted from the light source unit.

  In the surface shape measurement apparatus according to the thirteenth aspect of the present invention, in the eleventh aspect or the twelfth aspect, the pre-measurement condition is at least one of a gain of the imaging unit, an exposure time, and an aperture value.

  The surface shape measuring apparatus according to the fourteenth aspect of the present invention is the surface shape measuring apparatus according to the ninth aspect or the tenth aspect, wherein the light source unit has a pulsed light source that periodically emits white light, and the control means emits and images the pulsed light source. Control is performed so that the image acquisition of each part is periodically performed while maintaining a certain correlation.

  The surface shape measuring apparatus according to the fifteenth aspect of the present invention is the surface shape measuring apparatus according to the fourteenth aspect, wherein the light emission cycle of the pulse light source is longer than the image acquisition cycle of the image pickup unit, and the light emission time per cycle of the pulse light source is one of the image pickup unit. It is longer than the image acquisition time per cycle.

  The surface shape measurement apparatus according to the sixteenth aspect of the present invention is the fifteenth aspect, wherein the light emission cycle of the pulsed light source is twice the image acquisition cycle of the imaging unit.

  According to the present invention, the surface shape (three-dimensional shape) of the surface to be measured is highly sensitive and accurate even when the reflectance is not constant, such as when the surface to be measured has a complicated shape. Can be measured.

The block diagram which showed the whole structure of the surface shape measuring apparatus which concerns on 1st Embodiment The figure which showed the pixel arrangement | sequence of the interference image (imaging surface of an image pick-up element) on xy coordinates Diagram illustrating interference fringe curve The figure which illustrated the relationship between the different z-coordinate value of the different point of a surface to be measured, and an interference fringe curve The flowchart which showed an example of the surface shape measuring method using the surface shape measuring apparatus which concerns on 1st Embodiment The figure which showed an example of the plurality of interference fringe curves corresponding to the arbitrary points of the measured surface The figure which showed an example of the plurality of interference fringe curves corresponding to the arbitrary points of the measured surface The figure which showed an example of distribution of the interference fringe curve selected with respect to each pixel (equivalent to each point of a to-be-measured surface) of an interference image The block diagram which showed the whole structure of the surface shape measuring apparatus which concerns on other embodiment of this invention. The block diagram which showed the whole structure of the surface shape measuring apparatus which concerns on 2nd Embodiment Timing chart showing the relationship between the light emission timing of the light source and the image acquisition timing of the image sensor The flowchart which showed an example of the surface shape measuring method by the surface shape measuring apparatus which concerns on 2nd Embodiment The figure which showed the modification of 2nd Embodiment The figure which showed the other modification of 2nd Embodiment

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
First, a first embodiment of the present invention will be described.

  FIG. 1 is a configuration diagram showing the overall configuration of the surface shape measuring apparatus according to the first embodiment.

  As shown in FIG. 1, a surface shape measuring apparatus 1 according to the first embodiment is a so-called mirrow-type scan that measures a surface shape of a measurement object in a non-contact manner three-dimensionally using a mirrow interferometer. Type white interferometer (microscope), which is acquired by the optical unit 2 that acquires an interference image of the measurement target P, the stage 10 on which the measurement target P is placed, and various controls of the optical unit 2 and the optical unit 2 And a processing unit 18 including an arithmetic processing device such as a personal computer that performs various arithmetic processes based on the interference image.

  In the measurement space where the measurement object P is arranged, the two coordinate axes in the horizontal direction orthogonal to each other are the x axis (axis parallel to the paper surface) and the y axis (axis orthogonal to the paper surface), and the x axis and the y axis. A vertical coordinate axis orthogonal to the z axis is defined as z-axis.

  The stage 10 has a flat upper surface substantially parallel to the x-axis and the y-axis, and has a stage surface 10a on which the measurement object P is placed.

  At a position facing the stage surface 10a, that is, above the stage 10, the optical unit 2 accommodated and held integrally by a housing (not shown) is disposed.

  The optical unit 2 includes a light source unit 12 having an optical axis L1 parallel to the x axis, an interference unit 14 and an imaging unit 16 having an optical axis L0 parallel to the z axis. The optical axis L1 of the light source unit 12 is orthogonal to the optical axis L0 of the interference unit 14 and the imaging unit 16, and intersects the optical axis L0 between the interference unit 14 and the imaging unit 16. Note that the optical axis L1 is not necessarily parallel to the x-axis.

  The light source unit 12 emits white light having a wide wavelength range (low coherence light with low coherence) as illumination light for illuminating the measurement object P, and illumination light emitted after being diffused from the light source 40. And a collector lens 42 that converts the light into a substantially parallel light beam. The center axis of each of the light source 40 and the collector lens 42 is arranged coaxially as the optical axis L1 of the light source unit 12.

  Further, as the light source 40, any type of light emitter such as a light emitting diode, a semiconductor laser, a halogen lamp, and a high-intensity discharge lamp can be used.

  The illumination light emitted from the light source unit 12 is disposed between the interference unit 14 and the imaging unit 16, and is applied to a beam splitter 44 such as a half mirror disposed at a position where the optical axis L1 and the optical axis L0 intersect. Incident. The illumination light reflected by the beam splitter 44 (the flat light splitting surface (reflecting surface) of the beam splitter 44) travels along the optical axis L0 and enters the interference unit 14.

  The interference unit 14 is configured by a well-known Millo interferometer, divides the illumination light incident from the light source unit 12 into object light and reference light, and measures the object light with the z-axis direction (first direction) as the optical axis. Interference light is generated by causing the object light that is irradiated to the object P and returned from the measurement object P to interfere with the reference light.

  The interference unit 14 includes an objective lens 50 having a condensing function, a reference mirror 52 having a flat reflecting surface for reflecting light, and a beam splitter 54 having a flat light dividing surface for dividing light. The center axes of the objective lens 50, the reference mirror 52, and the beam splitter 54 are arranged coaxially as the optical axis L0 of the interference unit 14. The reference mirror 52 is installed on the central surface portion of the objective lens 50, for example.

  The illumination light incident on the interference unit 14 from the light source unit 12 is focused on the objective lens 50 and then enters the beam splitter 54.

  The beam splitter 54 is, for example, a half mirror, and the illumination light incident on the beam splitter 54 is split into object light that passes through the beam splitter 54 and reference light that is reflected by the light splitting surface of the beam splitter 54.

  The object light that has passed through the beam splitter 54 is irradiated onto the measurement target surface S of the measurement object P, returns from the measurement target surface S to the interference unit 14, and is incident on the beam splitter 54 again. Then, the object light transmitted through the beam splitter 54 enters the objective lens 50.

  On the other hand, the reference light reflected by the beam splitter 54 is reflected by the light reflecting surface of the reference mirror 52 and then enters the beam splitter 54 again. Then, the reference light reflected by the beam splitter 54 enters the objective lens 50.

  As a result, interference light is generated by superimposing the object light irradiated on the measurement surface S from the interference unit 14 and returning to the interference unit 14 and the reference light reflected by the reference mirror 52, and the interference light is generated by the objective lens 50. Then, the light is emitted from the interference unit 14 toward the imaging unit 16.

  Further, the beam splitter 54 (light splitting surface) is a position close to the objective lens 50 side by a distance h with respect to the focal plane of the objective lens 50 (a plane passing through the focus of the objective lens 50 and perpendicular to the optical axis L0). That is, it is arranged at a position higher than the focal plane of the objective lens 50 by a distance h.

  The reference mirror 52 (reflection surface) is disposed at a position that is closer to the objective lens 50 side by a distance h than the beam splitter 54 (light splitting surface), that is, a position that is higher by a distance h than the beam splitter 54.

  Therefore, the beam splitter 54 and the reference mirror 52 are arranged so that the optical path length of the object light reflected at the position of the focal plane of the objective lens 50 is equal to the optical path length of the reference light.

  When the focal length of the objective lens 50 is Hs, a value 2h obtained by doubling the distance h, that is, the distance 2h from the focal plane of the objective lens 50 to the reference mirror 52 is smaller than the focal length Hs of the objective lens 50. .

  Further, after the illumination light is divided into the object light and the reference light, the optical distance of the optical path through which each of the object light and the reference light passes until the object light and the reference light are superimposed is expressed as the optical path of the object light. The length and the optical path length of the reference light are referred to as the optical path length difference between the object light and the reference light.

  The interference unit 14 is provided so as to be linearly movable in the z-axis direction in the optical unit 2. The interference unit 14 moves in the z-axis direction by driving the interference unit actuator 56. As a result, the position (height) of the focal plane of the objective lens 50 moves in the z-axis direction, and the optical path length of the object light changes as the distance between the measured surface S and the beam splitter changes. The optical path length difference between the light and the reference light changes. The interference unit actuator 56 is an example of a scanning unit.

The imaging unit 16 is an imaging unit that receives interference light from the interference unit 14 and generates an interference image by the interference light. For example, the imaging unit 16 corresponds to a CCD (Charge Coupled Device) camera, and is connected to a CCD type imaging device 60. And an image lens 62. The axes that are the centers of the imaging element 60 and the imaging lens 62 are arranged coaxially with the optical axis L0 of the imaging unit 16. The imaging device 60 can be any imaging means such as a CMOS (Complementary Metal Oxide Semiconductor) type imaging device.

  The interference light emitted from the interference unit 14 enters the beam splitter 44 described above, and the interference light transmitted through the beam splitter 44 enters the imaging unit 16.

  The interference light incident on the imaging unit 16 forms an interference image on the imaging surface 60 a of the imaging element 60 by the imaging lens 62. Here, the imaging lens 62 enlarges an interference image with respect to a region around the optical axis L0 of the measurement target surface S of the measurement object P at a high magnification and forms an image on the imaging surface 60a of the imaging device 60.

  In addition, the imaging lens 62 images a point on the focal plane of the objective lens 50 of the interference unit 14 as an image point on the imaging surface of the imaging element 60. That is, the imaging unit 16 is designed so that it is in focus (focused) on the position of the focal plane of the objective lens 50. In the following, the position of the focal plane of the measurement object P in the z-axis direction is simply referred to as “focus position” or “focus position of the imaging unit 16”.

  The interference image formed on the imaging surface 60a of the imaging device 60 is converted into an electrical signal by the imaging device 60 and acquired as an interference image. Then, the interference image is given to the processing unit 18.

  As described above, the optical unit 2 including the light source unit 12, the interference unit 14, the imaging unit 16, and the like is provided as a whole so as to be linearly movable in the z-axis direction. For example, the optical unit 2 is supported by a z-axis guide unit (not shown) provided upright along the z-axis direction so as to be able to move straight. The entire optical unit 2 moves straight in the z-axis direction by driving the z actuator 70. Accordingly, the focus position of the imaging unit 16 can be moved in the z-axis direction more than in the case where the interference unit 14 is moved in the z-axis direction. For example, the imaging unit according to the thickness of the measurement target P or the like The 16 focus positions can be adjusted to appropriate positions.

  When the processing unit 18 measures the surface shape of the measurement surface S of the measurement object P, the processing unit 18 controls the interference unit actuator 56 to move the interference unit 14 of the optical unit 2 in the z-axis direction (first direction). The interference images are sequentially acquired from the image sensor 60 of the imaging unit 16. Then, an interferogram (hereinafter also referred to as “interference fringe curve”) for each point on the surface S to be measured is obtained based on the acquired interference image, and the surface of the surface to be measured is determined based on the interferogram for each point. The position of each point in the z-axis direction is obtained, and three-dimensional shape data indicating the surface shape of the measured surface S is obtained.

  The processing for acquiring the three-dimensional shape data of the surface S to be measured will be described. The imaging device 60 of the imaging unit 16 has a large number of two-dimensional arrays arranged along the xy plane (horizontal plane) composed of the x axis and the y axis. The luminance value of the interference image received by each pixel, that is, the luminance value of each pixel of the interference image acquired by the image sensor 60 is composed of each light receiving element (pixel). The intensity (intensity information) of the interference light according to the optical path length difference between the object light reflected by the point and the reference light is shown.

  Here, as shown in FIG. 2, the pixels in the m-th column and the n-th row of the interference image (the imaging surface of the imaging device 60) are represented as (m, n). An x coordinate value indicating the position of the pixel (m, n) in the x-axis direction (hereinafter, the position in the x-axis direction is referred to as “x position”) is represented by x (m, n), and the position in the y-axis direction ( Hereinafter, a y coordinate value indicating a position “y position” in the y-axis direction) is expressed as y (m, n).

  Further, the x coordinate value indicating the x position of the point on the measured surface S of the measurement object P corresponding to the pixel (m, n) is represented as X (m, n), and the y coordinate value indicating the y position is represented as Y. It is assumed that (m, n) is represented, and the point is represented by (X (m, n), Y (m, n)) by an xy coordinate value. The point on the measured surface S corresponding to the pixel (m, n) is on the measured surface S where the image point is formed at the position of the pixel (m, n) in the focused state. Means a point.

  At this time, the luminance value of the pixel (m, n) of the interference image acquired by the image sensor 60 is a point (X (m, n), Y () on the measured surface S corresponding to the pixel (m, n). m, n)) indicates the size according to the optical path length difference between the object light irradiated to the reference light and the reference light. When the optical path length difference is 0, the largest value is shown.

  That is, the interference unit actuator 56 of FIG. 1 moves the interference unit 14 in the z-axis direction, and the relative position of the interference unit 14 with respect to the optical unit 2 (imaging unit 16) (hereinafter referred to as “z position”). ) Is moved, the focus position of the imaging unit 16 (focal plane of the objective lens 50) is also moved in the z-axis direction, and the focus position is also displaced by the same displacement amount as the interference unit 14. Further, when the focus position is displaced, the optical path length of the object light applied to each point on the surface S to be measured also changes.

  Then, while moving the interference unit 14 in the z-axis direction and displacing the focus position, that is, while changing the optical path length of the object light, the interference image is sequentially acquired from the image sensor 60 and any pixel ( When the luminance value of m, n) is detected, the luminance value along the interference fringe curve (interferogram) Q as shown in FIG. 3 is obtained with respect to the z coordinate value of the focus position.

  Here, the processing unit 18 can detect the amount of displacement of the interference unit 14 from the predetermined reference position (z position of the interference unit 14) by a detection signal from a position detection unit (not shown) such as a potentiometer or an encoder. In the case where the z position of the interference unit 14 is controlled without using the position detecting means, for example, when the interference unit 14 is moved by a certain amount of displacement by the drive signal applied to the interference unit actuator 56, the total amount It can be detected by the amount of displacement. Then, the z position of the focus position when the interference unit 14 is the reference position is set as the reference position (origin position) of the z coordinate in the measurement space, and the displacement amount from the reference position of the interference unit 14 is the z coordinate value of the focus position. Can be obtained as For the z coordinate value, a position higher than the origin position (position approaching the imaging unit 16) is a positive side, and a position lower (position approaching the stage surface 10a) is a negative side. In addition, the reference position of the interference unit 14, that is, the origin position of the z coordinate can be set and changed to an arbitrary z position.

  The interference fringe curve Q at an arbitrary pixel (m, n) is irradiated to a point (X (m, n), Y (m, n)) on the measured surface S corresponding to the pixel (m, n). When the optical path length difference between the object light and the reference light is larger than a predetermined value, the luminance value is substantially constant. When the optical path length difference is smaller than the predetermined value, the luminance value oscillates as the optical path length difference decreases. As the amplitude increases.

  Therefore, the interference fringe curve Q shows the maximum value when the optical path lengths of the object light and the reference light match (when the optical path length difference is 0), and the maximum value in the envelope of the interference fringe curve Q Indicates.

  Further, the optical path length between the object light and the reference light irradiated to the point (X (m, n), Y (m, n)) on the measured surface S is such that the focus position of the imaging unit 16 is the measured surface S. When the upper point (X (m, n), Y (m, n)) coincides with the z position, it matches.

  Therefore, when the interference fringe curve Q shows the maximum value (or when the envelope of the interference fringe curve Q shows the maximum value), the focus position is a point (X (m, n), Y ( The z coordinate value of the focus position at that time is the z coordinate of the point (X (m, n), Y (m, n)) on the measured surface S. Indicates the value.

  From the above, the processing unit 18 moves the interference unit 14 in the z-axis direction (first direction) by the interference unit actuator 56 and moves the focus position in the z-axis direction (changes the optical path length of the object light). However, the interference image is sequentially acquired from the image sensor 60, and the luminance value of each pixel (m, n) is acquired in association with the z coordinate value of the focus position. That is, the brightness value of each pixel (m, n) of the interference image is acquired while scanning the focus position in the z-axis direction. Then, for each pixel (m, n), the z-coordinate value of the focus position when the luminance value of the interference fringe curve Q as shown in FIG. 3 shows the maximum value is measured for each pixel (m, n). It is detected as a z-coordinate value Z (m, n) of a point (X (m, n), Y (m, n)) on the surface S.

  Z (m, n) represents the z coordinate value of the point (X (m, n), Y (m, n)) on the measured surface S corresponding to the pixel (m, n).

  Also, a method of detecting the z coordinate value of the focus position when the luminance value of the interference fringe curve Q shows the maximum value is well known, and any method may be adopted. For example, by acquiring an interference image at z coordinate values for every minute interval at the focus position, the luminance is such that an interference fringe curve Q as shown in FIG. 3 can be actually drawn for each pixel (m, n). The z-coordinate of the focus position when the luminance value of the interference fringe curve Q shows the maximum value by detecting the z-coordinate value of the focus position when the acquired luminance value shows the maximum value. The value can be detected. Alternatively, the interference fringe curve Q is estimated by the least square method or the like based on the luminance value acquired at each z coordinate value of the focus position, or the envelope of the interference fringe curve Q is estimated, and the estimated interference fringe curve Q Alternatively, the z coordinate value of the focus position when the luminance value shows the maximum value based on the envelope is detected, thereby detecting the z coordinate value of the focus position when the luminance value of the interference fringe curve Q shows the maximum value. be able to.

  As described above, the processing unit 18 uses the points (X (m, n), Y) on the measured surface S corresponding to the pixels (m, n) of the interference image (the imaging surface 60a of the imaging device 60). By detecting the z coordinate value Z (m, n) of (m, n)), the relative height of each point (X (m, n), Y (m, n)) on the surface S to be measured. Can be detected. Then, the x coordinate value X (m, n), the y coordinate value Y (m, n), and the z coordinate value Z (m, n) of each point on the measured surface S are converted into a three-dimensional shape of the measured surface S. It can be acquired as data (data indicating the surface shape). For example, as shown in FIG. 4, when z coordinate values Z1, Z2, and Z3 at three points on the measured surface S corresponding to three pixels arranged in the x-axis direction are different, the focus position is scanned in the z-axis direction. When the luminance values of the pixels of the interference image are acquired while the interference position is the z-coordinate value Z1, Z2, and Z3 with respect to each of the pixels, the interference fringe curves Q1, Q2, and Q3 having the maximum luminance value are obtained. Is acquired. Therefore, by detecting the z coordinate value of the focus position when the luminance values of the interference fringe curves Q1, Q2, and Q3 show the maximum values, z at three points on the measured surface S corresponding to those pixels is detected. Coordinate values Z1, Z2, and Z3 can be detected.

  By the way, when the surface to be measured S of the measurement object P has a complicated shape having, for example, a flat portion and a slope portion, the amount of white light emitted is adjusted so as to be appropriate in a portion having a large reflectance, There are cases where the waveform amplitude of the interference fringe curve at a portion having a low reflectance is small and measurement cannot be performed correctly. Conversely, if the amount of white light emission is adjusted so as to be appropriate at a location where the reflectivity is low, the interference fringe curve at the location where the reflectivity is high is saturated (ie, exceeds a preset measurement range). Measurement may not be performed correctly.

  On the other hand, in the surface shape measuring apparatus 1 of the first embodiment, in order to solve the above-described problem, the measurement is performed twice under measurement conditions in which the amount of white light emission is different from each other, and the first measurement is performed by each measurement. An interference fringe curve and a second interference fringe curve are obtained for each point, an interference fringe curve suitable for each point is selected from the first interference fringe curve and the second interference fringe curve, and the interference for each selected point. Based on the fringe curve, a process for detecting the relative height (z coordinate value) of each point on the surface to be measured is performed.

  In order to realize such processing, the surface shape measuring apparatus 1 according to the first embodiment includes a light source control unit 72 as an example of a control unit, as shown in FIG. The light source control unit 72 controls the amount of white light emitted from the light source 40 (light source light amount). Specifically, the light source control unit 72, when the measurement is performed twice by the processing unit 18 with different measurement conditions for the measurement object, the light emission amount (first light emission amount) in the first measurement, The light emission amount (second light emission amount) in the second measurement is determined, and the light emission amount of the light source 40 is controlled so as to be the light emission amount determined in each measurement. The first light emission amount and the second light emission amount are different from each other. For example, the first light emission amount is an appropriate large light amount when the reflectance of the measurement surface S is low, and the second light emission amount is an appropriate small light amount when the reflectance of the measurement surface S is high.

  FIG. 5 is a flowchart showing an example of a surface shape measuring method by the surface shape measuring apparatus according to the first embodiment.

  When the measurement object P is placed on the stage surface 10a of the stage 10 and, for example, the start of measurement is instructed by the input unit 22 in FIG. 1, first, the process of step S10 in FIG. 5 (first measurement condition setting process). As described above, the light source control unit 72 performs control so that the amount of white light emitted from the light source 40 becomes the first amount of light (large amount of light).

  Next, as the process of Step S12 (first interferogram acquisition process), the processing unit 18 controls the interference unit actuator 56 to move the interference unit 14 of the optical unit 2 in the z-axis direction to change the focus position to z. Interference images are sequentially acquired from the image sensor 60 while moving in the axial direction, and a first interference fringe curve (first) is obtained for each point of the measurement surface S (that is, each pixel of the interference image) based on the acquired interference image. Interferogram).

  Next, as the process of Step S14 (second measurement condition setting process), the light source control unit 72 performs control so that the light emission amount of the white light emitted from the light source 40 becomes the second light emission amount (small light amount). .

  Next, as the process of Step S16 (second interferogram acquisition process), similarly to the process of Step S12 (first interferogram acquisition process), the processing unit 18 controls the interference unit actuator 56 to control the optical unit. The interference image 14 is sequentially acquired from the image sensor 60 while moving the two interference portions 14 in the z-axis direction and the focus position is moved in the z-axis direction, and each point on the surface S to be measured (that is, based on the acquired interference image) The second interference fringe curve (second interferogram) is acquired for each pixel of the interference image.

  Next, as the process of Step S18 (first selection process), the processing unit 18 is preset from the first interference fringe curve (first interferogram) and the second interference fringe curve (second interferogram). An interference fringe curve within the measured range is selected, and this process is performed for all points (pixels).

  FIG. 6 is a diagram illustrating an example of the first interference fringe curve Qa and the second interference fringe curve Qb with respect to an arbitrary point (arbitrary pixel in the interference image) on the surface S to be measured. In this example, the first interference fringe curve Qa is acquired when the amount of white light emitted is the first amount of light (large amount of light). Therefore, in the case where the reflectance at an arbitrary point on the measurement surface S is high, the first interference fringe curve Qa exceeds the preset measurement range as shown in FIG. It may be difficult to detect the z-coordinate value of the focus position when the luminance value of the first interference fringe curve Qa shows the maximum value (maximum value of the waveform amplitude). On the other hand, the second interference fringe curve Qb is a measurement condition different from the measurement condition when obtaining the first interference fringe curve Qa, that is, the first emission amount of white light (when obtaining the first interference fringe curve Qa ( Since the second light emission amount (small light amount) is less than the large light amount), the second interference fringe curve Qb falls within a preset measurement range as shown in FIG. It becomes possible to stably and accurately detect the z coordinate value of the focus position when the luminance value of the second interference fringe curve Qb shows the maximum value (maximum value of the waveform amplitude).

  Therefore, in the first embodiment, within the measurement range from the first interference fringe curve and the second interference fringe curve obtained for an arbitrary point (arbitrary pixel in the interference image) of the measurement surface S. The focus position when the luminance value of the selected interference fringe curve (the second interference fringe curve Qb in the example shown in FIG. 6) shows the maximum value (maximum value of the waveform amplitude). Is detected as a z-coordinate value Z at a point on the surface to be measured.

  Next, as a process of Step S20 (second selection process), the processing unit 18 selects a plurality of interference fringe curves for any point on the measurement surface S in Step S18 (first selection process) described above. If this is the case (that is, if both the first fringe curve and the second fringe curve are within the measurement range), the interference fringe curve with the maximum maximum waveform amplitude is selected from these interference fringe curves. This process is performed for all points (pixels).

  FIG. 7 is a diagram showing a case where both the first interference fringe curve Qa and the second interference fringe curve Qb with respect to an arbitrary point (pixel) on the measurement surface S are within a preset measurement range. In the case of the example shown in FIG. 7, in the process of Step S18 (first selection process), the first interference fringe curve Qa and the second interference fringe curve Qb are both within the preset measurement range. Both the interference fringe curve Qa and the second interference fringe curve Qb are selected. In such a case, even if the interference fringe curve is within the measurement range, if the waveform amplitude is too small, the z coordinate value of the focus position when the luminance value shows the maximum value may not be detected accurately. Therefore, in the first embodiment, in the case of the example shown in FIG. 7, the first interference fringe curve Qa and the second interference fringe curve in the measurement range are used as the step (second selection step) in step S20. The interference fringe curve Qa having the largest waveform amplitude maximum is selected from Qb.

  FIG. 8 is a diagram showing an example of the distribution of interference fringe curves selected for each pixel (corresponding to each point on the surface to be measured) of the interference image. In the example shown in FIG. 8, the portion of the measured surface S corresponding to the central portion of the interference image is a portion having a low reflectance, and each point (pixel) corresponding to this portion has a first emission amount of white light. The first interference fringe curve (first interferogram) Qa acquired when the light emission amount (large light amount) is selected. Further, the portion of the measured surface S corresponding to the peripheral portion of the interference image is a portion having a high reflectance, and each point (pixel) corresponding to this portion has a white light emission amount smaller than the first light emission amount. The second interference fringe curve (second interferogram) Qb acquired when the amount of light emission is two (small amount of light) is selected.

  Next, as a process of step S22 (detection process), the processing unit 18 acquires three-dimensional shape data indicating the surface shape of the measurement surface S based on the interference fringe curve selected for each point of the measurement surface S. To do. That is, the x-coordinate value X (m, n), y-coordinate value Y (m, n), and z-coordinate value Z (m, n) of each point on the measured surface S are used as the three-dimensional shape of the measured surface S. Get as data. The process for acquiring the three-dimensional shape data of the surface S to be measured is as described above.

  When the above process is completed, the measurement of the surface shape of the measurement object P is completed.

  Note that step S10 (first measurement condition setting step), step S12 (first interferogram acquisition step), step S14 (second measurement condition setting step), and step S16 (second interferogram) shown in FIG. (Acquisition step) corresponds to the “acquisition step” of the present invention. Step S18 (first selection process) and step S20 (second selection process) correspond to the “selection step” of the present invention. Step S22 (detection step) corresponds to the “detection step” of the present invention.

  As described above, in the first embodiment, each point (pixel) of the measurement surface S is within the measurement range set in advance from the first interference fringe curve and the second interference fringe curve, and The interference fringe curve having the largest waveform amplitude is selected. That is, since an appropriate interference fringe curve is selected for each point on the surface to be measured according to the difference in reflectance depending on the shape and material of the surface to be measured S, the surface to be measured S has a complicated shape, etc. Thus, even when the reflectance is not constant, the surface shape (three-dimensional shape) of the measurement surface S can be measured with high sensitivity and high accuracy.

  In the first embodiment, a mode in which the light source control unit 72 is provided as an example of the control unit has been described. However, the present invention is not limited to this. For example, as illustrated in FIG. 9, the imaging control unit 74 may be provided. Good. The imaging control unit 74 controls the gain of the image sensor 60 in the imaging unit 16, the exposure time, the aperture value of an aperture unit (not shown), and the like. Also in this aspect, similarly to the aspect in the first embodiment, the first interference fringe curve and the second interference acquired under different measurement conditions (that is, the gain of the imaging unit 16, the exposure time, the aperture value, and the like). By selecting an appropriate interference fringe curve for each point of the surface to be measured S according to the difference in reflectance depending on the shape and material of the surface to be measured S from the fringe curve, the surface to be measured S has a complicated shape. Even if it has, it becomes possible to measure the surface shape (three-dimensional shape) of the surface S to be measured with high sensitivity and high accuracy.

  Moreover, although illustration is abbreviate | omitted, the aspect provided with both the light source control part 72 of FIG. 1 and the imaging control part 74 of FIG. 9 as an example of a control means may be sufficient. In this case, as a measurement condition for the measurement object P, the measurement object is set by combining the emission amount of white light emitted from the light source 40, the gain in the imaging unit 16, the exposure time, the aperture value, and the like. Optimization can be achieved in accordance with the difference in reflectance depending on the shape, material, etc. of the surface S to be measured.

  In the first embodiment, the measurement condition for the measurement object P is changed and measurement is performed twice, and a first interference fringe curve and a second interference fringe curve having different measurement conditions are obtained for each point. However, the number of measurements for the measurement object P may be three or more. In this case, a plurality of interference fringe curves with different measurement conditions (that is, three or more) are acquired, but the measurement range is within the plurality of interference fringe curves and the maximum value of the waveform amplitude is the largest. An interference fringe curve may be selected. Thereby, even when the measured surface S has a more complicated shape, the surface shape (three-dimensional shape) of the measured surface S can be measured stably and reliably.

(Second Embodiment)
In the first embodiment, the surface shape (three-dimensional shape) of the measurement surface S is highly sensitive even when the reflectance is not constant, such as when the measurement surface S of the measurement object P has a complicated shape. Although it is possible to measure with high accuracy, it is necessary to measure multiple times (at least twice) under different measurement conditions for the measurement object P (for example, the amount of white light emission), A new problem arises that it takes a long time to measure. In addition, in order to perform measurement a plurality of times, the scanning process for moving the interference unit 14 in the z-axis direction must be repeated. If an error due to the repetition of this scanning process increases, the measurement accuracy may be adversely affected. is there.

  In order to solve the problem in the first embodiment, the second embodiment is the same as the first embodiment, with only one measurement without performing measurement on the measurement object P a plurality of times. As a result, the measurement time can be shortened compared to the first embodiment, and the measurement accuracy is improved by eliminating the influence of errors caused by repeated scanning processes. . Details of the second embodiment will be described below. In addition, description is abbreviate | omitted about the part which is common in 1st Embodiment, and it demonstrates focusing on the characteristic part of 2nd Embodiment.

  FIG. 10 is a configuration diagram showing the overall configuration of the surface shape measuring apparatus according to the second embodiment. In FIG. 10, components that are the same as or similar to those in FIG. 1 or FIG. 9 are given the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 10, the light source unit 12 of the surface shape measuring apparatus 1A according to the second embodiment includes a light source 40 composed of a pulsed light source that periodically emits pulsed white light (pulsed light). ing.

  The surface shape measuring apparatus 1A includes a light source control unit 72 and an imaging control unit 74. The processing unit 18 includes a synchronization signal generation unit 80, a light emission timing signal generation unit 82, and an image acquisition timing signal generation unit. 84 is provided. In FIG. 10, the case where the synchronization signal generation unit 80, the light emission timing signal generation unit 82, and the image acquisition timing signal generation unit 84 are part of the components of the processing unit 18 is illustrated as an example. Instead, some or all of these may be configured separately from the processing unit 18.

  The synchronization signal generator 80 generates the synchronization signal TG0 based on the clock signal output from the clock signal generator (not shown). The synchronization signal TG0 generated by the synchronization signal generation unit 80 is output to the light emission timing signal generation unit 82 and the image acquisition timing signal generation unit 84.

  The light emission timing signal generation unit 82 is synchronized with the synchronization signal TG0 output from the synchronization signal generation unit 80 for a predetermined period of time (while the scanning process is being performed), and the light emission timing signal TG1 to the light source 40 is constant. Is output.

  The image acquisition timing signal generation unit 84 synchronizes with the synchronization signal output from the synchronization signal generation unit 80 and acquires the image acquisition timing to the image sensor 60 for a predetermined period of time (while the scanning process is performed). The signal TG2 is output.

  The light source controller 72 controls the driving of the light source 40 based on the light emission timing signal TG1 output from the light emission timing signal generator 82. That is, the light source controller 72 causes the light source 40 to emit light when the light emission timing signal TG1 is on, and stops the light emission of the light source 40 when the light emission timing signal TG1 is off. Thereby, the light source 40 emits pulsed light at a predetermined cycle (light emission cycle T1 described later) synchronized with the synchronization signal TG0.

  The imaging control unit 74 controls driving of the imaging element 60 based on the image acquisition timing signal TG2 output from the image acquisition timing signal generation unit 84. That is, the imaging control unit 74 executes image acquisition (image reading) by the imaging element 60 when the image acquisition timing signal TG2 is on, and stops image reading by the imaging element 60 when the image acquisition timing signal TG2 is off. To do. As a result, the image sensor 60 performs image acquisition at a predetermined cycle (image acquisition cycle T2 described later) synchronized with the synchronization signal TG0.

  Here, the relationship between the light emission timing of the light source 40 and the image acquisition timing of the image sensor 60 will be described with reference to FIG. FIG. 11 is a timing chart showing the relationship between the light emission timing of the light source 40 and the image acquisition timing of the image sensor 60. In FIG. 11, (a) is a light emission timing signal TG1, (b) is an image acquisition timing signal TG2, and (c) is an exposure amount of an interference image (image per frame) obtained by image acquisition per cycle. Each is shown. In addition, the light emission corresponding | compatible area | region shown by dot hatching in FIG.11 (b) represents the area | region (time slot | zone) where image acquisition is performed when the light source 40 is light-emitting.

  In the second embodiment, as shown in FIGS. 11A and 11B, the light emission period (light emission interval) T1 of the light source 40 is set to the image acquisition period (image read interval) T2 of the image sensor 60. Is set to double. The light emission time Ta per cycle of the light source 40 is set to be longer than the image acquisition time Tb per cycle of the image sensor 60. Due to this relationship, as shown in FIG. 11C, an interference image with a relatively large exposure amount (a large light amount image, an example of the first interference image) and an interference image with a relatively small exposure amount (small size). A light quantity image and an example of a second interference image) are obtained alternately. That is, an even frame image with a frame number of 0, 2, 4, 6,... Is a large light image, and an odd frame image with a frame number of 1, 3, 5, 7,. It becomes.

  As described above, in the second embodiment, the light source 40 emits light at regular intervals while maintaining a constant correlation with the image acquisition timing in the image sensor 60. That is, the light emission of the light source 40 and the image acquisition of the image sensor 60 are controlled to be performed periodically while maintaining a certain correlation. As a result, when the interference image is sequentially acquired from the image sensor 60 while moving the interference unit 14 in the z-axis direction and the focus position is displaced, the exposure amount is relatively large (that is, light with respect to the image acquisition time). An interference image (large light image) having a relatively large irradiation time and an interference image (low light image) having a relatively small exposure amount (that is, a light irradiation time is relatively small with respect to the image acquisition time). It becomes possible to acquire alternately. Therefore, it is possible to sequentially acquire interference images (a large light amount image and a small light amount image) having different light amounts in one measurement, and from each interference image, a first interference fringe curve (first interferogram) and a second An interference fringe curve (second interferogram) can be acquired. As a result, similar to the first embodiment, even when the surface to be measured S of the measurement object P has a complicated shape, the surface shape (3 (Dimensional shape) can be measured with high sensitivity and high accuracy.

  Next, a surface shape measuring method by the surface shape measuring apparatus 1A according to the second embodiment will be described with reference to FIG. FIG. 12 is a flowchart showing an example of a surface shape measuring method by the surface shape measuring apparatus according to the second embodiment. In FIG. 12, processes that are the same as the processes shown in FIG. 5 are given the same reference numerals, and descriptions thereof are simplified or omitted.

  In the second embodiment, when the start of measurement is instructed in the same manner as in the first embodiment, first, as the process (control process) of step S30 in FIG. Control is performed so that image acquisition is synchronized. Specifically, the light source control unit 72 controls the driving of the light source 40 based on the light emission timing signal TG1 output from the light emission timing signal generation unit 82. Thereby, the light source 40 emits pulsed light with a light emission period T1 synchronized with the synchronization signal TG0. Further, the imaging control unit 74 controls driving of the imaging element 60 based on the image acquisition timing signal TG2 output from the image acquisition timing signal generation unit 84. Thereby, the image sensor 60 performs image acquisition at an image acquisition cycle T2 synchronized with the synchronization signal TG0. The light emission period T1 is set to be twice the image acquisition period T2.

  Next, as the process of step S32 (image acquisition process), the processing unit 18 controls the interference unit actuator 56 to move the interference unit 14 of the optical unit 2 in the z-axis direction and move the focus position in the z-axis direction. The interference image is sequentially acquired from the image sensor 60 while the image is being processed. Accordingly, an interference image (a large light amount image) having a relatively large exposure amount (that is, a light irradiation time is relatively large with respect to the image acquisition time) and a relatively small exposure amount (that is, an image acquisition time). In contrast, interference images (low-light images) are obtained alternately. The acquired interference image is stored in an image memory (not shown) separately for a large light amount image (even frame image) and a small light amount image (odd frame image).

  Next, as a process of Step S34 (first interferogram acquisition process), the processing unit 18 performs each point (that is, each point on the surface S to be measured (that is, an even frame image) based on a plurality of large light quantity images (even frame images) stored in the memory. A first interference fringe curve (first interferogram) is acquired for each pixel of the interference image.

  Next, as a process of Step S36 (second interferogram acquisition process), the processing unit 18 performs each point (that is, each point on the measurement surface S based on a plurality of small light quantity images (odd frame images) stored in the memory). The second interference fringe curve (second interferogram) is acquired for each pixel of the interference image. The subsequent processing is the same as in the first embodiment.

  As described above, according to the second embodiment, a large light image and a small light amount are measured in one measurement (scanning process) for the measurement object P that needs to be measured a plurality of times in the first embodiment. Since the images are obtained alternately, the first interference fringe curve and the second interference fringe curve can be obtained for each point (pixel) on the surface S to be measured from these images. The same effect can be obtained, and the measurement time can be shortened compared to the first embodiment, and the measurement accuracy is improved because there is no error due to repeated scanning processing by a plurality of measurements. Can be made.

  In the second embodiment, as an example of a preferred mode, the light emission period T1 of the light source 40 is longer than the image acquisition period T2 of the image sensor 60, and the light emission time Ta per cycle of the light source 40 is the image sensor 60. In the present embodiment, a plurality of types of interference images having different light amounts can be alternately and repeatedly acquired in one measurement (scanning process). The light emission of the light source 40 and the image acquisition of the image sensor 60 may be performed periodically while maintaining a certain correlation.

  FIG. 13 is a diagram showing a modification of the second embodiment, and is a timing chart showing the relationship between the light emission timing of the light source 40 and the image acquisition timing of the image sensor 60.

  In the modification shown in FIG. 13, the light emission period T1 of the light source 40 is set to be three times the image acquisition period T2 of the image sensor 60. The light emission time Ta per cycle of the light source 40 is set to be longer than the image acquisition time Tb per cycle of the image sensor 60. Due to this relationship, as shown in FIG. 13C, an interference image (large light amount image) having a relatively large exposure amount and an interference image (small light amount image) having a relatively small exposure amount are alternately obtained. It is done. That is, frame images with frame numbers 0, 1, 3, 4, 6, 7... Are large light images, and frame images with frame numbers 2, 5,.

  Therefore, when acquiring the interference image sequentially from the image sensor 60 while moving the interference unit 14 in the z-axis direction and displacing the focus position, the images are in the order of the large light image, the large light image, and the small light image. Obtained periodically. That is, interference images (a large light amount image and a small light amount image) having different light amounts can be acquired by one measurement, and the first interference fringe curve (first interferogram) and the second interference are obtained from each interference image. A fringe curve (second interferogram) can be acquired, and an interference fringe curve having a maximum waveform amplitude and a maximum value is selected from these interference fringe curves. Thus, the same effect as that of the second embodiment described above can be obtained.

  In the second embodiment, the case where the phases of the light emission timing signal TG1 and the image acquisition timing signal TG2 coincide with each other has been described. However, the present invention is not limited to this. In other words, in the present invention, a constant correlation is maintained between the image acquisition timing in the image sensor 60 so that at least a large light image and a small light image can be periodically acquired by one measurement, and at a constant interval. For example, the light source 40 may be adjusted so that the phase of the light emission timing signal TG1 and the image acquisition timing signal TG2 is shifted by a phase adjustment circuit (not shown).

  FIG. 14 is a diagram illustrating another modification of the second embodiment, and is a timing chart illustrating a relationship between the light emission timing of the light source 40 and the image acquisition timing of the image sensor 60.

  In the modification shown in FIG. 14, the light emission period T <b> 1 of the light source 40 is set to be 1.5 times the image acquisition period T <b> 2 of the image sensor 60. The light emission time Ta per cycle of the light source 40 is set to be longer than the image acquisition time Tb per cycle of the image sensor 60. Further, the image acquisition timing signal TG2 is set to be out of phase by the delay time Tc with respect to the light emission timing signal TG1. Due to this relationship, as shown in FIG. 14C, an interference image (large light amount image) having a relatively large exposure amount and an interference image (small light amount image) having a relatively small exposure amount are relatively Interference images (medium light images) with a medium exposure amount are obtained alternately. That is, a frame image with a frame number of 0, 3,... Is a large light image, a frame image with a frame number of 2, 5,. .. is a small light image.

  Therefore, when sequentially acquiring the interference images from the image sensor 60 while moving the interference unit 14 in the z-axis direction and displacing the focus position, the images are in the order of the large light image, the small light image, and the medium light image. Obtained periodically. That is, interference images (a large light amount image, a medium light amount image, and a small light amount image) having different light amounts can be acquired by one measurement, and a first interference fringe curve (first interferogram) is obtained from each interference image. ), A second interference fringe curve (second interferogram), and a third interference fringe curve (third interferogram), and a measurement range set in advance from these interference fringe curves. By selecting the interference fringe curve having the largest waveform amplitude and the maximum value, the same effect as in the second embodiment described above can be obtained.

(Other)
In each of the above-described embodiments, the configuration in which the three-dimensional shape of the measurement target surface of the measurement object is non-contacted using a Millo interferometer is shown as an example. However, the present invention is not limited to this, for example, Michelson It is also possible to adopt a type of interferometer.

  Moreover, in each said embodiment, although the case where the to-be-measured surface S had a complicated shape was shown as an example when the reflectance of the to-be-measured surface S of the measuring object P is not constant, it is not restricted to this, For example, In addition, the present invention can be effectively used even in the case where a glossy part or an inclined part having a sharp change in reflectance from the measurement object P is included, a case where the reflectance is made of different materials, or a combination thereof. it can.

  P ... measurement object, O ... central axis, Q, Q1, Q2, Q3, Qa, Qb ... interference fringe curve, S ... measured surface, L0, L1 ... optical axis, 1 ... surface shape measuring device, 2 ... optical Part, 10 ... stage, 10a ... stage surface, 12 ... light source part, 14 ... interference part, 16 ... imaging part, 18 ... processing part, 20 ... display part, 22 ... input part, 40 ... light source, 42 ... collector lens, 44, 54 ... Beam splitter, 50 ... Objective lens, 52 ... Reference mirror, 56 ... Interference part actuator, 60 ... Imaging element, 60a ... Imaging surface, 62 ... Imaging lens, 70 ... z actuator, 72 ... Light source control part, 74: Imaging control unit, 80 ... Synchronization signal generation unit, 82 ... Light emission timing signal generation unit, 84 ... Image acquisition timing signal generation unit

Claims (16)

A light source that emits white light;
The white light from the light source unit is divided into object light and reference light, the object light is irradiated onto the measurement target surface of the measurement object, and the object light returning from the measurement target surface interferes with the reference light. An interference unit for generating the interference light,
Scanning means for moving the interference unit relative to the measurement object in the optical axis direction of the object light;
An imaging unit that images the interference light from the interference unit and generates an interference image by the interference light;
The interference image is sequentially acquired from the imaging unit while the interference unit is moved relative to the measurement object in the optical axis direction by the scanning unit, and the surface to be measured is obtained based on the acquired interference image. A processing unit for obtaining an interferogram for each of the points, and detecting a position in the optical axis direction of each point of the measured surface based on the interferogram for each of the points;
Control means for controlling the operation of the light source unit or the imaging unit;
With
The processing unit controls the operation of the light source unit or the imaging unit by the control unit, so that the first interference image having a relatively large amount of light from the imaging unit and the second interference having a relatively small amount of light from the imaging unit. And obtaining a plurality of interferograms for each point based on each of the first interference image and the second interference image, and presetting from the plurality of interferograms A surface shape measuring device that selects an interferogram within a measurement range for each point and detects the position of each point on the surface to be measured in the optical axis direction based on the selected interferogram for each point. . When there are a plurality of interferograms within the measurement range, the processing unit selects an interferogram having the largest waveform amplitude maximum value from the interferograms within the measurement range.
The surface shape measuring apparatus according to claim 1. The processing unit performs a plurality of measurements on the measurement object by changing the measurement conditions for the measurement object by controlling the operation of the light source unit or the imaging unit by the control unit, Obtaining a plurality of interferograms for each point by a plurality of measurements, selecting an interferogram within a preset measurement range from the plurality of interferograms for each point, and selecting the selected Detecting the position in the optical axis direction of each point of the measured surface based on an interferogram for each point;
The surface shape measuring apparatus according to claim 1 or 2. The measurement condition is a light emission amount of white light emitted from the light source unit.
The surface shape measuring apparatus according to claim 3. The measurement condition is at least one of a gain, an exposure time, and an aperture value of the imaging unit.
The surface shape measuring apparatus according to claim 3 or 4. The light source unit has a pulse light source that emits pulsed white light,
The control means controls the light emission of the pulse light source and the image acquisition of the imaging unit to be performed periodically while maintaining a constant correlation.
The surface shape measuring apparatus according to claim 1 or 2. The light emission cycle of the pulse light source is longer than the image acquisition cycle of the imaging unit, and the light emission time per cycle of the pulse light source is longer than the image acquisition time of the imaging unit.
The surface shape measuring apparatus according to claim 6. The light emission period of the pulse light source is twice the image acquisition period of the imaging unit.
The surface shape measuring apparatus according to claim 7. A light source that emits white light;
The white light from the light source unit is divided into object light and reference light, the object light is irradiated onto the measurement target surface of the measurement object, and the object light returning from the measurement target surface interferes with the reference light. An interference unit for generating the interference light,
Scanning means for moving the interference unit relative to the measurement object in the optical axis direction of the object light;
An imaging unit that images the interference light from the interference unit and generates an interference image by the interference light;
The interference image is sequentially acquired from the imaging unit while the interference unit is moved relative to the measurement object in the optical axis direction by the scanning unit, and the surface to be measured is obtained based on the acquired interference image. A processing unit for obtaining an interferogram for each of the points, and detecting a position in the optical axis direction of each point of the measured surface based on the interferogram for each of the points;
Control means for controlling the operation of the light source unit or the imaging unit;
A surface shape measuring method in a surface shape measuring apparatus comprising:
By controlling the operation of the light source unit or the imaging unit by the control unit, at least a first interference image having a relatively large amount of light and a second interference image having a relatively small amount of light are respectively acquired from the imaging unit. And obtaining a plurality of interferograms for each point based on each of the first interference image and the second interference image;
A selection step of selecting, for each of the points, an interferogram within a preset measurement range from the plurality of interferograms;
A detection step of detecting a position in the optical axis direction of each point of the measured surface based on an interferogram for each of the points selected in the selection step;
A surface shape measuring method comprising: In the selection step, when there are a plurality of interferograms within the measurement range, the interferogram having the largest waveform amplitude maximum value is selected from the interferograms within the measurement range.
The surface shape measuring method according to claim 9. In the obtaining step, the control means controls the operation of the light source unit or the imaging unit to perform different measurements for the measurement object, and performs measurement for the measurement object multiple times, Obtaining a plurality of interferograms for each point by a plurality of measurements;
The surface shape measuring method according to claim 9 or 10.   The surface shape measurement method according to claim 11, wherein the measurement condition is a light emission amount of white light emitted from the light source unit.   The surface shape measurement method according to claim 11 or 12, wherein the measurement condition is at least one of a gain, an exposure time, and an aperture value of the imaging unit. The light source unit has a pulse light source that periodically emits the white light,
The control means controls the light emission of the pulse light source and the image acquisition of the imaging unit to be performed periodically while maintaining a constant correlation.
The surface shape measuring method according to claim 9 or 10. The light emission cycle of the pulse light source is longer than the image acquisition cycle of the imaging unit, and the light emission time per cycle of the pulse light source is longer than the image acquisition time of the imaging unit.
The surface shape measuring method according to claim 14. The light emission period of the pulse light source is twice the image acquisition period of the imaging unit.
The surface shape measuring method according to claim 15.

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