KR100876257B1 - Optical measuring method and device therefor - Google Patents

Abstract

The line beam is irradiated to the surface of the transparent measurement object 1 with a laser beam light source 2 at a predetermined incident angle, and the surface light and the back light generated from the surface, the back surface of the transparent measurement object 1 are formed into an optical system 3. The light receiving surface at the image forming position of the back light reflected by the half mirror 4 and the sensor for surface light 5 arranged so that the light receiving surface is positioned at the image forming position of the surface light transmitted through the half mirror 4. Two-dimensional optical measurement data corresponding to the surface of the transparent measurement object 1 with the input of the back light sensor 6 and the output signal from the surface light sensor 5 and the operation information of the support mechanism arranged as the input. 2-dimensional corresponding to the back surface of the transparent measurement object 1 by inputting the measurement data holding part 7 for surface and the operation signal of the support mechanism and the output signal from the back light sensor 6 which generate | generate and hold | maintain Optical measurement data The measurement data holding part 8 for back surface which produces | generates and hold | maintains, and the front and back determination process is performed by inputting both optical measurement data, and the surface data corresponding only to the surface of the transparent measurement object 1 and the back surface data corresponding only to back surface are performed. The front and back data generation holding unit 9 generates and maintains the foreign matter detection accuracy of the detected surface without increasing the scan time, and also measures not only the surface but also the state of the rear surface.

Description

Optical measuring method and apparatus therefor {OPTICAL MEASURING METHOD AND DEVICE THEREFOR}

The present invention relates to an optical measuring method and apparatus for measuring the state of the front and back surfaces of a transparent measurement object using a laser beam.

Background Art Conventionally, an optical measuring device for inspecting foreign matter adhered to a surface of a thin substrate such as a glass substrate for a liquid crystal display device and a substrate having a transparent film for a flat panel display device has been proposed.

 For example, in the foreign material inspection apparatus developed by the inventors described in the December 2001 issue of the monthly display, the foreign matter adhered to the back surface is not detected by using a device configuration combining an imaging detection method and a line sensor. It is realizing that the foreign matter adhering to the sensor is detected with high accuracy.

Scattered light from foreign matter adhering to the back surface of the glass substrate is configured to be imaged at a position far ahead of the line sensor through the imaging optical system, and also at a position slightly off from the position where the line sensor waits. For this reason, the foreign matter adhering to the back surface is hardly detected. In this system, since a mechanism utilizing the basic properties of the optical system is adopted, the test can be performed with high reliability and stability.

The optical measuring device described in Japanese Patent No. 2671241 includes a first laser light source for injecting laser light at a first incidence angle to a glass plate, a second laser light source for injecting laser light at a second incidence angle to a glass plate, The foreign matter of the inspection surface of a glass plate is detected by performing a predetermined process based on the condensing optical system which condenses the light by each laser beam, the light receiving element which receives the condensed light, and the signal from a light receiving element.

Therefore, for example, it is thought that the foreign matter adhering to the surface can be detected with high precision by eliminating the influence of the foreign matter adhering to the back surface of the glass plate.

Monthly Display In the foreign material inspection device described in the December 2001 issue of the separate edition, when the foreign matters attached to the back surface become more than a certain size due to the characteristics of the optical system, the scattered light enters the line sensor, and the foreign matters attached to the back surface are mixed and detected. It will be done.

For example, when a 1.1 mm glass substrate for LCD is to detect foreign substances of 1 μm or more on the surface, foreign substances of 20 μm or more on the back surface are simultaneously detected. In a typical LCD process, since there is almost no dust on the order of 20 µm, the practical problem is not so large, but it is preferable not to completely detect the foreign matter adhering to the back surface.

In addition, in this system, only the foreign matter adhering to the back side was intended to be excluded, and foreign matter adhering to the back side could not be detected.

In the optical measuring device described in Japanese Patent No. 2671241, the irradiation of the laser light by the first laser light source and the irradiation of the laser light by the second laser light source must be performed independently of each other, so that the configuration of the optical system becomes complicated, and the device size becomes large. High mounting accuracy is required, leading to the disadvantages of poor maintenance and high cost. In addition, there is a problem that the scan time is doubled.

In addition, since the light collected by the condensing optical system is guided to the light receiving element, there is an inevitable limitation that the foreign matter on the front surface and the foreign matter on the back surface cannot be distinguished due to the saturation of the light receiving element. Foreign substances adhering to the back surface of a certain size or more are mixed and detected.

In addition, since only the foreign matter adhering to the surface of the glass plate is detected, the foreign matter adhering to the back surface of the glass plate cannot be detected. Specifically, only the state of the surface of the glass plate could be detected, but the state of the back surface could not be detected.

The present invention has been made in view of the above problems, and the measurement accuracy of the measurement target surface of the transparent body can be increased without increasing the scan time by a very simple configuration of one light source, one detection optical system, and two sensors. Moreover, it aims at providing the optical measuring method and apparatus which can measure not only the surface but also the back surface state.

The optical measuring method of this invention irradiates the laser beam of a linear form as a line beam to the surface of the transparent measurement object supported by the support member at a predetermined angle from the oblique upper side, and the scattered light from the surface of the transparent measurement object and the scattered light from the back surface Is passed through a single imaging optical system having a light receiving angle of 90 degrees with respect to the surface of the transparent measurement object and having a depth of focus smaller than the thickness of the transparent measurement object, and then led to a single half mirror, Scattered light is transmitted through the single half mirror to form a light receiving portion of one detector having a linear light receiving portion, and the other scattered light is reflected by the half mirror to have a light receiving portion of the other detector having a linear light receiving portion. It forms an image and performs predetermined | prescribed process based on the signal output from both detectors. W, alternatively as a way to signal that corresponds to the surface, is assigned to one of a signal corresponding to the back, and displays the assigned signal corresponding to the signal is allocated corresponding to the surface, respectively.

Therefore, in the case of employing the optical measuring method of the present invention, since only one scan with a laser beam is required, a detector corresponding to scattered light from the front and back surfaces of the transparent measurement object with an imaging optical system can be used without increasing the scan time. The imaging accuracy of the measurement target surface can be improved by forming an image on the light receiving portion of the light source, and the state of the back surface as well as the surface can be measured.

The optical measuring device of the present invention is a laser beam irradiation means for irradiating a linear laser beam as a line beam at a predetermined angle on a surface of a transparent measurement object supported by a support member, and scattered light from the surface of a transparent measurement object. And a single imaging optical system having a light receiving angle of 90 degrees with respect to the surface of the transparent measuring object for forming scattered light from the back surface, and having a depth of focus smaller than the thickness of the transparent measuring object and downstream of the single imaging optical system. Located in the single half mirror and the imaging position of one scattered light transmitted through the single imaging optical system and transmitted through the single half mirror, through the single imaging optical system, and further in the single half mirror. Each disposed in correspondence with the image formation position of the other scattered light reflected by A pair of light receiving means having a light receiving part of the shape, a predetermined processing based on signals output from both light receiving means, and processing means for selectively allocating to one of a signal corresponding to a surface and a signal corresponding to a back surface; And display means for displaying the allocation signal corresponding to the surface and the allocation signal corresponding to the back surface, respectively.

Therefore, in the case of employing the optical measuring device of the present invention, a very simple configuration of one light source, one detection optical system, and two sensors requires only one scan with a laser beam to increase scan time. The imaging accuracy of the measurement target surface can be improved by imaging the scattered light from the front and back surfaces of the transparent measurement object by the imaging optical system to the light receiving portion of the corresponding detector, and can measure not only the surface but also the state of the back surface.

1 is a schematic view showing an embodiment of the optical measuring device of the present invention;

FIG. 2 is a view showing the results of inspecting a scattering surface of a glass substrate in which particles of a spherical particle were intentionally scattered, and outputting the resultant as foreign matter on the surface; FIG.

FIG. 3 is a view showing the results of the glass substrate of FIG. 2 intentionally scattered with the spherical particles inverted upside down and inspected, and outputted as a foreign matter with a back surface. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, embodiment of the optical measuring method of this invention and its apparatus is described in detail.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the foreign matter inspection apparatus which is one Embodiment of the optical measuring apparatus of this invention.

This optical measuring device is made of a transparent measurement object (for example, a thin substrate such as a glass substrate for a liquid crystal display device, a substrate having a transparent film for a flat panel display device) 1 supported by a support mechanism (not shown). The imaging optical system which forms the laser light source 2 which irradiates a line beam with a predetermined angle of incidence with respect to the surface, and the image of the surface scattering light generated from the surface, the back surface, and the back surface scattering light by the irradiated line beam ( 3), the half mirror 4 provided at a predetermined position upstream from the image forming position, the surface light sensor 5 arranged so that the light receiving surface is located at the image forming position of the surface light transmitted through the half mirror 4, and the half Transparent measurement by using as input the output signal from the back light sensor 6 and the surface light sensor 5 and the operation information of the support mechanism which are arranged so that the light receiving surface is located at the image formation position of the back light reflected by the mirror 4Surface-information measurement data holding unit 7 for generating and maintaining two-dimensional optical measurement data corresponding to the surface of the object 1, output signals from the back light sensor 6, and operation information of the support mechanism as inputs. Optical measurement data held by the back side measurement data holding part 8 and the surface measurement data holding part 7 for generating and holding two-dimensional optical measurement data corresponding to the back side of the transparent measurement object 1 Front and back determination processing is performed by using the optical measurement data held in the measurement data holding unit 8 for backside as input, thereby generating surface data corresponding only to the surface of the transparent measurement object 1 and backside data corresponding only to the backside. It has a front and back data generation holding | maintenance part 9 to hold | maintain, and the display part (not shown) which performs the display based only on surface data, and the display based only on back surface data.

In addition, 11 is an encoder which outputs the signal which shows the position of the transparent measurement object 1, 12 is a control signal and encoder from a stage operation control part (in this embodiment, it is contained in the surface measurement data holding part 7). It is a stage controller which inputs the signal from (11), and outputs the operation command with respect to a support mechanism.

The said laser light source 2 irradiates a line beam with the incident angle of 45 degrees or more and less than 90 degrees, Preferably it is 80 degrees, with respect to the surface of the transparent measuring object 1. The laser light emitted from the laser light source 2 is preferably S-polarized light and has a wavelength of 400 to 1200 nm, preferably 800 nm. Moreover, it is preferable to set the width | variety of a line beam to the width equal to or more than the visual field width of the sensor 5 for surface lights and the sensor 6 for back surface lights.

It is preferable that the imaging optical system 3 should just have a depth of focus smaller than the thickness of the transparent measurement object 1, and it is preferable that the depth of focus is 1/2 or less of the thickness of the transparent measurement object 1. Moreover, it is preferable to suppress the ups and downs of the transparent measurement object 1 to this depth of focus or less.

The arrangement position of the surface light sensor 5 and the back light sensor 6 takes into account the position offset value (deviation amount) determined by the refractive index, the thickness, the incident angle of the laser light, the wavelength, and the like of the transparent measurement object 1. And the two-dimensional coordinates such as the position where the front surface and the back surface of the transparent measurement object 1 are imaged.

The surface measurement data holding unit 7 and the rear surface measuring data holding unit 8 transmit signals from the surface light sensor 5 and the rear light sensor 6 and the movement data of the transparent measurement object 1. In this case, the two-dimensional optical measurement data corresponding to the front and back surfaces of the transparent measurement object 1 are generated and maintained in consideration of the offset value.

The front and back data generation holding unit 9 corresponds to the same two-dimensional coordinates among the two-dimensional optical measurement data held by the surface measurement data holding unit 7 and the back side measurement data holding unit 8. It is to determine which optical measurement data is to be employed based on the relationship of the optical measurement data, and generate and maintain surface data corresponding only to the surface of the transparent measurement object 1 and back surface data corresponding only to the back surface based on the determination result. . Specifically, in the case of the foreign matter inspection apparatus, the optical measurement data held in the surface measurement data holding unit 7 and A, the optical measurement data held in the rear surface measurement data holding unit 8 in correspondence with the same position. In the case of B, the output signals of A and B to be handled both become scattered light intensity signals from foreign matter attached to either the surface or the back surface, although it is unclear at this time. Basically, as the foreign matter increases, the scattered light intensity also increases. Since an imaging optical system and a linear light-receiving unit, or a line sensor, are used, if this output signal is used as the total luminance signal of the phase of the foreign matter, the increase of this output signal due to the increase of the size of the foreign matter is quite sharp at first. In addition to the effect of the change of, the effect of the change of the luminance is also large). In addition, after the luminance is saturated with the increase of the scattered light intensity and the influence due to the change in luminance is virtually eliminated, the output signal gradually increases under the influence of the size of the image. Therefore, an output signal that matches the size of the foreign matter can be obtained without generating saturation of the output signal.

Since the signals of each of A and B are compared and a linear light receiving unit, that is, a line sensor is used, if A> kB, the surface data corresponding to only the surface of the transparent measurement object 1, that is, the data of foreign matter attached to the surface is assumed. On the contrary, if A? In addition, k is a value calculated | required by the intensity ratio of the light from the surface of the transparent measuring object 1 and the light from a back surface, the optical imaging characteristic of an imaging optical system, and a depth of focus. For example, when S polarized light is used as the laser light and the incidence angle is set to 80 °, the light intensity from the back surface becomes about 1/2 of the light intensity from the surface. In consideration of the optical characteristics, k becomes a value larger than approximately 2.

In addition, before and after the increase of the above-mentioned output signal is slowed down, by using this determination formula separately, it is possible to make a higher precision determination. That is, at this time, the judgment formula becomes a more complicated nonlinear judgment formula.

The operation of the optical measuring device of the above configuration is as follows.

When the line beam is irradiated from the laser light source 2 onto the surface of the transparent measuring object 1 at a predetermined angle of incidence, the line beam is refracted based on Snell's law to intrude into the transparent measuring object 1. We exit from the back side. Therefore, the irradiation position with respect to the surface of the transparent measuring object 1 of a line beam, and the emission position with respect to the back surface differ with respect to the optical axis of the imaging optical system 3, and ideally, The sensor disposed at an imaging position of light (scattered light, etc.) from the irradiation position with respect to the surface does not sense light (scattered light, etc.) from the emission position on the back side of the transparent measuring object 1 (this light is a transparent measuring object ( Received by a sensor disposed at an imaging position of light from an irradiation position with respect to the back side of 1). Moreover, since a line beam is not irradiated to the back surface which faces the irradiation position with respect to the surface of the transparent measurement object 1, this part does not affect a sensor either.

However, in reality, very little light is irradiated on the back of the laser measuring object to the irradiation position with respect to the surface of the transparent measuring object 1, which may affect the sensor, resulting in optical measurement error. Cause it to come.

This embodiment considers such an actual fact, and an optical measurement error can be largely suppressed by performing the following process.

In further detail, when the transparent measurement object 1 is scanned by the line beam from the laser light source 2, the light from the line beam incident position of the transparent measurement object 1 is further reduced by the imaging optical system 3 and further. Through the mirror 4, it forms in the light-receiving surface of the sensor 5 for surface light. In addition, although the amount of light is greatly reduced, light from the back surface facing the line beam incidence position is received by the imaging optical system 3 and through the half mirror 4, and the depth of focus is determined by the transparent measurement object 1. Since it is smaller than the thickness, the focus does not fit.

 Moreover, the said line beam is guide | induced to the back surface of the transparent measurement object 1 according to Snell's law, and it exits as it is. Therefore, the backside position facing the line beam incidence position and the backside position from which the line beam is guided are different from each other. As a result, the light from the back surface position where the line beam is guided is reflected by the imaging optical system 3 and the half mirror 4, and is imaged on the light receiving surface of the back light sensor 6.

When the measurement content is a foreign matter inspection, in these cases, when there is no foreign matter at the place affected by the line beam, the intensity of scattered light or the like is remarkably low, so that the surface light sensor 5 and the back light sensor ( 6) outputs a signal indicating that no foreign matter exists.

On the contrary, if foreign matter exists in a place affected by the line beam, the intensity of scattered light or the like increases, so that a signal indicating that the foreign matter exists from the surface light sensor 5 and the back light sensor 6 is output. .

Here, the output signal of the surface light sensor 5 and the back light sensor 6 increases as the size of the foreign matter increases. Incidentally, the increase in the output signal is quite rapid at first (the effect of the change in luminance is greater than the effect of the change in size of the image). In addition, after the influence due to the change in luminance is almost eliminated, the output signal gradually increases under the influence of the change in the size of the image. Therefore, an output signal that matches the size of the foreign matter can be obtained without generating saturation of the output signal. As a result, the presence of foreign matters and the size determination thereof can be improved.

Then, the surface measurement is performed by taking the signal from the surface light sensor 5, the back light sensor 6, and the movement data of the transparent measurement object 1 into consideration, and taking into account the position offset value if applicable. The data holding part 7 and the measurement data holding part 8 for back surface generate and hold two-dimensional optical measurement data corresponding to the front surface and the back surface of the transparent measurement object 1, respectively. Therefore, the surface measurement data holding part 7 and the back surface measurement data holding part 8 hold surface measurement data and back surface measurement data corresponding to the same two-dimensional coordinates.

Thereafter, in the front and back data generation holding unit 9, the surface measuring data corresponding to the same two-dimensional coordinates held by the surface measuring data holding unit 7 and the back side measuring data holding unit 8, The backside measurement data is compared to determine which optical measurement data is to be employed, and based on this determination result, surface data corresponding only to the surface of the transparent measurement object 1 and backside data corresponding to only the backside are generated and maintained.                 

And the display part 10 can perform display based only on surface data, and display based only on back surface data.

In the case of a foreign matter inspection device, the presence, position, and size of a foreign matter attached to the surface can be obtained from the surface data, and the presence, position, and size of a foreign matter attached to the back surface can be obtained from the surface data.

Therefore, based on these displays, not only the surface of the transparent measurement object 1 but also the presence or absence of the foreign matter adhering to the back surface, the density of the foreign matter, etc. can be grasped simply and accurately. Moreover, the effect of washing | cleaning can be confirmed by performing said series of processes before and after washing | cleaning of the transparent measurement object 1, for example.

Moreover, since only one scan by the laser light source 2 can obtain surface data corresponding only to the surface of the transparent measurement object 1 and back surface data corresponding only to the back surface, the required time can be shortened.

Next, the optical measuring method of the present invention will be described in more detail. In addition, this method is applied to the foreign matter inspection of the transparent glass substrate, and the surface inspection camera and the back inspection camera which focus on the surface and the back surface of the transparent glass substrate, respectively, are installed to the surface inspection camera and the back inspection camera. The test result obtained by this is shown by C and D, respectively.

First, the necessity and unnecessaryness of front and back separation processing are set. Specifically, for example, when the inspection object is a transparent glass substrate, front and back separation treatment is required, and when the inspection object is an opaque substrate, front and back separation treatment is unnecessary. In the latter case, only the inspection result by the surface inspection camera has meaning, so the same processing as in the prior art may be performed (the detailed description is omitted).

When the front and back separation processing is set to be necessary, the test results C and D are stored to recognize that they are related. Specifically, for example, a flag indicating that there is relevance is set.

After that, the offset amounts of offset of the inspection results C and D are corrected. As a correction amount for this correction, it is possible to prepare in advance so that a predetermined value can be set, and the offset shift is corrected using this predetermined value. In addition, since this correction process is a well-known technique, detailed description is abbreviate | omitted.

Next, an example of arithmetic processing based on both inspection results C and D is demonstrated.

First, the foreign matter existing in the same coordinate is recognized based on the position coordinates of the inspection results C and D in which offset misalignment is corrected. Here, for the same coordinate determination, the allowable error parameter (0.01 to 5.00 mm) is set, and foreign matter existing within this distance is identified. In the case where a large amount of foreign matter exists within this distance, only the closer side is identified.

In this case, the foreign substance information group of C and D is displayed as C & D, and the foreign substance information group of D is displayed as D & C.

In addition, C-D which removes C & D from C is represented by C-D, and D & C which removes D & C from D is represented by D-C.

In this case, foreign substances can be detected as shown in Table 1.                 

  Foreign matter on the surface   Foreign matter on the back   CD    ○   D-C    ○   CD  obscurity  obscurity   D & C  obscurity  obscurity

Moreover, about C & D and D & C which are unclear in Table 1, the magnitude of a detection value is compared with respect to each foreign substance identified. However, instead of employing the detection value of C as it is, multiplying the predetermined coefficient k is adopted. Here, the coefficient k is a value in the range of 0.1-10.0, For example, it is preferable to set based on the measurement result. Moreover, in order to simplify an operation, it is preferable to set the default value (for example, 2.0) of the coefficient k.

In this case, foreign matter can be detected as shown in Table 2.

  surface   Back side  C & D kC ＞ D    ○  C & D kC≤D   X (C surface = Discard)  D & C D≤kC   ○  D & C D ＞ kC    X (D surface = Discard)

Therefore, determination of front and back is as follows.

Surface = (C-D) + {(C & D) & (kC> D)}

= (D-C) + {(D & C) & (D≤kC)}

In addition, the data on the backside found by the camera for surface inspection is (C & D) & (kC≤D),

The surface data found by the back inspection camera is (D & C) & (D> kC)

These are not employed as foreign matter detection results and are discarded.

2 and 3 show the results of detecting foreign matter by performing the above process.

FIG. 2 is a view showing a result of inspecting a scattering surface of a glass substrate in which particles of a spherical particle were intentionally scattered, and outputting it as a foreign matter on a surface. FIG.

In FIG. 2, the left side is a foreign material map, the circumference shows the whole surface of a glass substrate, the area | region of a white rectangle has shown the inspection area, and the gray circumference part has shown the non-inspection area | region. And a small dot shows the presence of a foreign material.

In addition, the upper right side in FIG. 2 is a histogram (frequency distribution), and the number of foreign matters having the size is shown on the horizontal axis and the size of the foreign matter on the vertical axis. And from this histogram, it turns out that the foreign material of the magnitude | size a little larger than the middle of the horizontal axis exists in the surface of a glass substrate. These foreign particles are scattered particles.

2, the number of foreign matters and the total number of foreign matters for each S, M, and L size classification are shown. As can be seen from these, about 10,000 foreign substances are detected.

FIG. 3 is a view showing the results of the glass substrate of FIG. 2 intentionally scattered with the spherical particles inverted upside down and inspected, and outputted as a foreign matter with a back surface. FIG.

In FIG. 3, the left side is a foreign matter map, the circumference shows the whole surface of a glass substrate, the area | region of a white rectangle has shown the inspection area, and the gray periphery part has shown the non-inspection area | region. And a small dot shows the presence of a foreign material. This map is similar to the state flipped so that the map of FIG. 2 can be reversed up and down.

3, the upper right side is a histogram (frequency distribution), which shows the size of foreign matter on the horizontal axis and the number of foreign matters on the vertical axis. And from this histogram, it turns out that the foreign material of the size slightly larger than the center of the horizontal axis exists in the surface of a glass substrate. These foreign particles are scattered particles.

 3, the number of foreign matters and the total number of foreign matters for each S, M, and L size classification are shown. As can be seen from these, about 10,000 foreign substances are detected.

As can be seen from FIGS. 2 and 3, foreign matters on the surface and foreign matters on the back surface can be detected with high accuracy.

In addition, although the specific example which detects the foreign material of the front and back of a transparent substrate was demonstrated above, it can be applied also when detecting defects, such as a flaw and a crack of the front and back of a transparent substrate, and also the roughness of the front and back of a transparent substrate is demonstrated. It is also applicable to the case of detecting.

Moreover, when measuring the pattern patterned on the front and back of a transparent substrate, it can apply also when the pattern is examined. However, in these cases, what is necessary is just the pattern which allows the permeation | transmission of light (for example, the pattern which consists of a remarkable thin metal thin film formed in the transparent substrate), and irradiates the light to the back surface of a transparent substrate regardless of the presence or absence of a pattern. It can be secured.

Claims (7)

The surface of the transparent measurement object supported by the supporting member is irradiated with a linear laser beam as a line beam at a predetermined angle from the oblique upper side, and the scattered light from the surface of the transparent measurement object and the scattered light from the back surface are the surface of the transparent measurement object. Passing through a single imaging optical system having a light receiving angle of about 90 degrees and having a depth of focus smaller than the thickness of the transparent measurement object, which then leads to a single half mirror and directs one scattered light to the single half mirror. The light-receiving portion of one detector having a linear light-receiving portion, which is transmitted, is imaged, the other scattered light is reflected by the half mirror, and the light-receiving portion of the other detector having a linear light-receiving portion is imaged and output from both detectors. A predetermined process based on the signal is performed to selectively correspond to the surface. Is assigned to one of a signal, a signal corresponding to the back surface, and displays an allocation signal corresponding to the surface and an allocation signal corresponding to the back surface, respectively. Laser light irradiation means (2) for irradiating a linear laser beam as a line beam at a predetermined angle from the oblique upper side to the surface of the transparent measurement object (1) supported by the supporting member; Single imaging having a light receiving angle of 90 degrees with respect to the surface of the transparent measurement object that forms scattered light from the surface of the transparent measurement object 1 and scattered light from the back side, and having a depth of focus smaller than the thickness of the transparent measurement object. A single half mirror 4 located downstream of the optical system 3 and the single imaging optical system 3, An imaging position of one scattered light that has passed through the single imaging optical system 3 and has passed through the single half mirror 4, and has passed through the single imaging optical system 3 and further has passed through the single half mirror ( 1 pair of light receiving means 5 and 6 which have a linear light receiving part arrange | positioned correspondingly to the image formation position of the other scattered light reflected by 4), Processing means (7, 8, 9) for performing predetermined processing based on signals output from both light receiving means (5, 6), and selectively assigning to one of a signal corresponding to a surface and a signal corresponding to a back surface; And display means for displaying the allocation signal corresponding to the surface and the allocation signal corresponding to the back surface, respectively. The method of claim 2, The optical measuring device (1) is a transparent substrate. The method of claim 3, The processing means (7, 8, 9) are provided from the surface of the transparent substrate (1) with respect to the signal output from one light receiving means (5) and the signal output from the other light receiving means (6). The magnitude of the ratio multiplied by the value multiplied by the intensity ratio between the light and the light from the back surface, the optical imaging characteristic of the imaging optical system 3, and the depth of focus is determined, and selectively corresponds to the surface based on the determination result. An optical measuring device assigned to one of the signal corresponding to the signal and the back surface. delete delete delete

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