JP3644311B2 - Projection lens inspection apparatus and projection lens inspection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for inspecting a projection lens.
[0002]
[Prior art]
In a projection display device, light emitted from an illumination optical system is modulated according to image information (image signal) using a liquid crystal panel or the like, and the modulated light is projected onto a screen using a projection lens. This realizes image display.
[0003]
FIG. 1 is a schematic configuration diagram illustrating an example of a projection display device. The projection display apparatus 1000 includes an illumination optical system 100, a color light separation optical system 200, a relay optical system 220, three liquid crystal light valves 300R, 300G, and 300B, a cross dichroic prism 320, and a projection lens 340. I have.
[0004]
The illumination optical system 100 includes a polarization generating optical system in addition to the light source device 20 that emits substantially parallel light, and emits one type of linearly polarized light having a uniform polarization direction. The light emitted from the illumination optical system 100 is separated into three color lights of red (R), green (G), and blue (B) in the color light separation optical system 200. The separated color lights are modulated in accordance with image information in the liquid crystal light valves 300R, 300G, and 300B. The liquid crystal light valves 300R, 300G, and 300B include a liquid crystal panel and polarizing plates disposed on the light incident surface side and the light emission surface side thereof. The color lights modulated by the liquid crystal light valves 300R, 300G, and 300B are combined by the cross dichroic prism 320 and projected onto the screen SC by the projection lens 340. As a result, an image is displayed on the screen SC. 1 is described in detail in, for example, Japanese Patent Application Laid-Open No. 10-325954 disclosed by the applicant of the present application, the details are described in this specification. The detailed explanation is omitted.
[0005]
By the way, the projection lens 340 used in the projection display apparatus 1000 may have variations in characteristics due to variations in manufacturing processes and the like. Since variations in the characteristics of the projection lens affect the quality of the image displayed by the projection display apparatus 1000, the characteristics of the projection lens are inspected before the projection display apparatus is shipped.
[0006]
Conventionally, the quality of the projection lens has been determined by mounting the projection lens to be inspected on a predetermined projection display device or the like and visually confirming the projected image.
[0007]
[Problems to be solved by the invention]
However, when inspecting the characteristics of the projection lens by visually confirming the projected image, it is not possible to obtain an accurate characteristic value of the projection lens, and the criterion for determining whether or not the projection lens is good is unclear. there were.
[0008]
The present invention has been made to solve the above-described problems in the prior art, and an object thereof is to provide a technique capable of accurately inspecting the characteristics of a projection lens.
[0009]
[Means for solving the problems and their functions and effects]
In order to solve at least a part of the above problems, an apparatus of the present invention is a projection lens inspection apparatus for inspecting a projection lens used in a projection display apparatus,
An image light emitting unit having a test pattern and emitting image light representing the test pattern;
A screen on which the image light is irradiated by the projection lens, and an image of the test pattern is displayed by the irradiation of the image light;
An imaging unit that captures an image of the test pattern displayed on the screen;
A focus state adjustment unit that automatically adjusts the focus state of the image of the test pattern;
A characteristic value calculation unit for calculating a characteristic value of the projection lens based on a change in brightness of the image of the test pattern;
It is characterized by providing.
[0010]
In the projection lens inspection apparatus of the present invention, after adjusting the focus state of the image displayed on the screen, the characteristic value can be calculated based on the change in brightness of the adjusted test pattern image. The characteristics can be accurately inspected.
[0011]
In the above apparatus,
The focus state adjustment unit may adjust the focus state by adjusting a spatial position of the test pattern in the image light emitting unit.
[0012]
In this way, the focus state of the test pattern image displayed on the screen can be easily adjusted.
[0013]
In the above apparatus,
The screen is a transmissive screen capable of observing an image from the back side of the projection surface on which image light is projected,
The imaging unit is preferably disposed on the back side of the projection surface.
[0014]
In this way, if the imaging unit is arranged on the back side of the projection surface using the transmission screen, the possibility that the imaging unit hinders the display of the test pattern image on the screen can be eliminated. Therefore, it is possible to adjust the focus state of the test pattern image well and accurately calculate the characteristic value of the projection lens.
[0015]
In the above apparatus,
The test pattern includes a first local pattern for forming periodic brightness in the image of the test pattern;
The characteristic value of the projection lens may be a value related to the resolution of the image determined based on a periodic change in brightness of the image of the first local pattern displayed on the screen.
[0016]
In this way, it is possible to obtain a value related to the resolution of the image as the characteristic value of the projection lens.
[0017]
In the above apparatus,
The test pattern includes a second local pattern for forming an isolated bright region in an image of the test pattern,
The characteristic value of the projection lens may be a value related to image flare calculated using the bright region of the image of the second local pattern displayed on the screen.
[0018]
This makes it possible to calculate a value related to image flare as the characteristic value of the projection lens.
[0019]
The method of the present invention is a method for inspecting a projection lens used in a projection display apparatus,
(A) emitting image light representing a test pattern;
(B) irradiating the screen with the image light by the projection lens, and displaying an image of the test pattern on the screen;
(C) capturing an image of the test pattern displayed on the screen;
(D) automatically adjusting the focus state of the image of the test pattern;
(E) calculating a characteristic value of the projection lens based on a change in brightness of an image of the test pattern;
It is characterized by providing.
[0020]
Even when the method of the present invention is used, it has the same operation and effect as the above-described apparatus, and the characteristic value can be calculated based on the change in brightness of the test pattern image.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
A. Projection lens inspection device:
FIG. 2 is an explanatory view showing an example of a projection lens inspection apparatus to which the present invention is applied. This apparatus is an apparatus for inspecting a projection lens used in the projection display apparatus of FIG. The projection lens inspection apparatus includes a projection unit 400 on which a projection lens 480 to be inspected is mounted, a mirror 510, a screen 500, and an inspection unit 600. In this apparatus, the projection lens 480 to be inspected is detachable and can be easily replaced with another projection lens.
[0022]
Image light (light representing an image) emitted from the projection unit 400 is reflected by the mirror 510 and irradiates the screen 500. The screen 500 is a transmissive screen capable of observing an image from the rear surface 500b side of the projection surface 500a on which image light is projected. The inspection unit 600 inspects the projection lens 480 using the image displayed on the screen 500.
[0023]
In the following description, as shown in FIG. 2, the inspection apparatus is represented by an XYZ orthogonal coordinate system in which a plane parallel to the display surface 500 b of the screen 500 is an XY plane. Further, in the inspection apparatus, the projection unit 400 is disposed at a predetermined angle with respect to the XZ plane by a holding unit (not shown). For this reason, in the following description, the projection unit 400 is represented by an STU orthogonal coordinate system obtained by rotating the XYZ orthogonal coordinate system about the X axis by the predetermined angle. The central axis n1 of the projection lens 480 is parallel to the SU plane.
[0024]
FIG. 3 is an explanatory diagram showing a state when the projection unit 400 of FIG. 2 is viewed from the + T direction. As shown in FIG. 3, in addition to the projection lens 480, the projection unit 400 includes a light source device 410, a color light filter 420, first and second mirrors 430 and 442, an inspection sheet 450, and an inspection sheet holding unit. 440, a six-axis adjusting unit 460 for adjusting the arrangement of the inspection sheet holding unit 440, and a dummy prism 470. Note that the inspection sheet holding unit 440 holds the inspection sheet 450 so as not to touch the second mirror 442. 2, the light source device 410, the color light filter 420, and the first mirror 430 illustrated in FIG. 3 are in the + S direction (the paper surface) than the six-axis adjustment unit 460, the inspection sheet holding unit 440, the dummy prism 470, and the projection lens 480. The illustration is omitted for the sake of convenience.
[0025]
As shown in FIG. 3, the projection unit 400 is configured such that substantially the same light is incident on the projection lens 480 as when the projection lens is used in the projection display device of FIG. 1. That is, the light source device 410 corresponds to the light source device 20 in FIG. 1, the inspection sheet 450 corresponds to the liquid crystal light valves 300R, 300G, and 300B in FIG. 1, and the dummy prism 470 corresponds to the cross dichroic prism 320 in FIG. Yes. If an inspection apparatus including such a projection unit 400 is used, it is considered that the projection lens can be inspected in the same environment as when the projection lens is used in the projection display apparatus.
[0026]
The light source device 410 of FIG. 3 includes a light source lamp 412 and a parabolic reflector 414. The paraboloid reflector 414 has a concave paraboloid surface. The light source lamp 412 is disposed in the vicinity of the focal position of the concave surface having a paraboloid shape. With this configuration, the light emitted from the light source lamp 412 and reflected by the paraboloid reflector 414 is emitted from the light source device 410 as a substantially parallel light bundle. As the light source lamp 412, a metal halide lamp, a high pressure mercury lamp, or the like is used. In addition, as the paraboloid reflector 414, for example, a reflection film such as a dielectric multilayer film or a metal film is formed on the concave surface of a rotating paraboloid made of glass ceramics.
[0027]
The color light filter 420 has a function of extracting color light of a predetermined color included in the light emitted from the light source device 410. The color light filter 420 of the present embodiment has a substantially disk shape and is rotatable about a central axis 420c. In the color light filter 420, four types of filters, an R filter, a G filter, a B filter, and a W filter, and a light shielding portion are divided into five equal parts. The light shielding unit is used when it is desired to block light while light is emitted from the light source device 410. The R filter has a function of transmitting only red color light out of the light emitted from the light source device 410. Similarly, the G filter and the B filter have a function of transmitting only green color light and blue color light, respectively. The W filter has a function of transmitting all color light (hereinafter also referred to as white color light), that is, a function of emitting the light emitted from the light source device 410 as it is. As the four types of filters, for example, a filter in which a dielectric multilayer film that transmits four types of color light respectively on a substantially circular glass plate can be used. In addition, as a W filter, you may utilize the glass area | region in which the dielectric multilayer film is not formed as it is.
[0028]
The first and second mirrors 430 and 442 have a function as light guide means for guiding the color light emitted from the light source device 410 and passing through the color light filter 420 to the projection lens 480. As the first and second mirrors, mirrors or metal mirrors on which a dielectric multilayer film that reflects all color lights can be used.
[0029]
The inspection sheet holding unit 440 has a function of holding the inspection sheet 450. The inspection sheet 450 is obtained by forming a test pattern serving as a light shielding region on a light-transmitting plate material such as glass.
[0030]
FIG. 4 is an explanatory diagram showing the inspection sheet 450 on which the test pattern TP is formed. On the inspection sheet 450 shown in FIG. 4, four substantially square local patterns (hereinafter also referred to as “square local patterns”) PSa to PSd are formed at the four corners of the peripheral portion. Further, a plurality of ruled line local patterns (hereinafter also referred to as “ruled line local patterns”) PL are formed in a lattice shape, and are divided into 20 rectangular blocks. In each of the 20 blocks, first measurement local patterns PM1 to PM20 for evaluating the characteristics of the projection lens are formed. Further, second measurement local patterns PMC1 to PMC4 for evaluating the characteristics of the projection lens are formed along the oblique lines L1 and L2 indicated by broken lines in the drawing. In the present specification, all patterns such as the square local patterns PSa to PSd, the ruled line local pattern PL, the first and second measurement local patterns PM1 to PM20, PMC1 to PMC4 are collectively referred to as a test pattern TP. In the test pattern TP in FIG. 4, four square local patterns PSa to PSd, a plurality of ruled line local patterns PL, and first and second measurement local patterns PM1 to PM20, PMC1 to PMC4 are formed. Other than the above, no local pattern is formed, but other local patterns may be formed.
[0031]
FIG. 5 is an explanatory diagram showing, in an enlarged manner, one square local pattern PSa included in the test pattern TP of FIG. In the figure, hatched areas are light-blocking areas through which light does not pass, and hatched areas are light-transmitting areas through which light passes. As shown in the figure, the square local pattern PSa includes nine square light-transmitting regions inside. The pattern shown in FIG. 5 is the same for the other square local patterns PSb to PSd in FIG.
[0032]
FIG. 6 is an explanatory diagram showing an enlarged view of one first measurement local pattern PM1 included in the test pattern TP of FIG. As shown in FIG. 6, the first measurement local pattern PM1 includes a plurality of patterns in each of the two areas WA and WB. The pattern in the area WA is a pattern in which a specific shape is formed by the light shielding area, and the pattern in the area WB is a pattern in which a specific shape is formed by the light transmitting area. In the figure, the area WA includes a character pattern in which numerals such as “20” and “25” are formed, and eight types of parallel line patterns PTAa to PTAh. Each of the parallel line patterns PTAa to PTAh is formed by periodically arranging a strip-shaped light transmitting region and a light shielding region, and the size or direction of each pattern is different from each other. On the other hand, in the region WB, a character pattern in which alphabets such as “A” and “B” are formed, four types of parallel line patterns PTBa to PTBd, and four types of small hole patterns that are substantially circular light-transmitting regions PHa to PHd are included. The pattern shown in FIG. 6 is the same for the other first measurement local patterns PM2 to PM20 shown in FIG.
[0033]
FIG. 7 is an explanatory diagram showing an enlargement of one second measurement local pattern PMC1 included in the test pattern TP of FIG. In the second measurement local pattern PMC1, four types of parallel line patterns similar to the parallel line patterns PTAa to PTAh included in the region WA of the first measurement local pattern PM1 shown in FIG. 6 are formed. However, in the second local pattern for measurement PMC1, strip-like light transmitting areas and light-shielding areas are arranged along the oblique line L1 in FIG. 4, and thus the first local pattern for measurement PM1 (FIG. 6). The direction is different from each parallel line pattern included. The pattern shown in FIG. 7 is the same for the other second measurement local patterns PMC2 to PMC4 shown in FIG.
[0034]
The test pattern TP shown in FIG. 4 is set to be approximately the same size (about 26.64 mm × about 19.98 mm) as an effective display area where image light is formed in the liquid crystal light valves 300R, 300G, and 300B of FIG. Has been. The ruled line local pattern PL included in the test pattern TP is formed with a line width of about 0.1 to about 0.2 mm. Further, as shown in FIG. 5, the four square local patterns PSa to PSd are formed with a side of about 0.4 mm. As shown in FIG. 6, the first local patterns for measurement PM1 to PM20 are formed with a size of about 0.8 mm × about 1.4 mm. As shown in FIG. 7, the second local patterns for measurement PMC1 to PMC4 are formed with a size of about 0.39 mm × about 0.32 mm. In addition, each parallel line pattern included in the first and second local patterns for measurement (FIGS. 6 and 7) has strip-shaped light-shielding regions and light-transmitting regions each having a width of about 10 to about 25 μm. Each small hole pattern included in the first measurement local pattern (FIG. 7) is formed with a diameter of about 5 to about 30 μm.
[0035]
The inspection sheet holding unit 440 (FIG. 3) is fixed to the 6-axis adjustment unit 460, and the arrangement of the inspection sheet holding unit 440 is adjusted by controlling the 6-axis adjustment unit 460. The six-axis adjustment unit 460 is a combination of six movable stages capable of translation in the S direction, T direction, and U direction, and rotation about the S axis, T axis, and U axis in the figure. is there. By controlling the six-axis adjusting unit 460, the spatial arrangement of the inspection sheet 450 held by the inspection sheet holding unit 440 can be adjusted. In other words, the spatial arrangement of the test pattern TP is adjusted by the control of the 6-axis adjustment unit 460.
[0036]
As described above, the dummy prism 470 is provided to simulate the cross dichroic prism 320 of the projection display device of FIG. In the cross dichroic prism 320 shown in FIG. 1, an “X” -shaped thin film is provided inside to synthesize light emitted from the three liquid crystal light valves 300R, 300G, and 300B. However, since this thin film is unnecessary in this inspection apparatus, the dummy prism 470 is formed by applying an antireflection coating to a glass body having the same cubic shape as the cross dichroic prism 320.
[0037]
The projection lens 480 to be inspected is sequentially replaced and mounted on the inspection apparatus. In this embodiment, the projection lens 480 is fixedly installed on a holding unit (not shown).
[0038]
With the configuration of the projection unit 400 described above, the light emitted from the light source device 20 (FIG. 3) is reflected by the first and second mirrors 430 and 442 after passing through the color light filter 420. The light reflected by the second mirror 442 passes through the inspection sheet 450 and is emitted as image light representing an image of the test pattern TP. The image light is projected by the projection lens 480 after passing through the dummy prism 470. As can be seen from this description, the projection unit 400 excluding the projection lens 480 in this embodiment corresponds to the image light emitting unit of the present invention.
[0039]
As shown in FIG. 2, in the projection unit 400 of the present embodiment, the central axis n1 of the projection lens 480 and the normal line n2 passing through the center of the inspection sheet 450 are shifted by a predetermined distance. This is to simulate the “tilting projection” state in the projection display device. The projection lens 480 is designed to project and display an image without distortion in such a tilt projection state. Note that projection in which the central axis n1 of the projection lens 480 and the normal line n2 passing through the center of the inspection sheet 450 do not coincide is generally referred to as “tilting projection”.
[0040]
The inspection unit 600 of FIG. 2 includes a processing unit 610, four adjustment imaging units 620a to 620d arranged in the vicinity of the four corners of the screen 500, and one measurement imaging unit 640. The processing unit 610 is electrically connected to the adjustment imaging units 620a to 620d and the measurement imaging unit 640, and is also electrically connected to the 6-axis adjustment unit 460 of the projection unit 400. The processing unit 610 analyzes the image data obtained by the adjustment imaging units 620a to 620d, and controls the 6-axis adjustment unit 460 based on the analysis result. As described above, the spatial arrangement of the test pattern TP is adjusted by controlling the six-axis adjusting unit 460, and thereby the focus state (described later) of the test pattern image is adjusted. The processing unit 610 has a function of processing the image data obtained by the measurement imaging unit 640 and calculating the characteristic value of the projection lens.
[0041]
As can be seen from this description, the processing unit 610 of this embodiment corresponds to a characteristic value calculation unit in the present invention. The adjustment imaging units 620a to 620d and the measurement imaging unit 640 correspond to the imaging unit in the present invention, and the adjustment imaging units 620a to 620d, the processing unit 610, and the six-axis adjustment unit 460 are the focus state adjustment unit. Equivalent to.
[0042]
FIG. 8 is an explanatory diagram showing the arrangement of the adjustment imaging units 620a to 620d and the measurement imaging unit 640 when the screen 500 is viewed from the + Z direction. As shown in the figure, the four adjustment imaging units 620a to 620d are provided at the four corners of the screen 500, and can be moved in the XY plane by a moving mechanism (not shown). The measurement imaging unit 640 is provided near the center of the screen 500, and can be moved in the XY plane by a moving mechanism (not shown). However, as shown in FIG. 2, the measurement imaging unit 640 is arranged so as to be shifted in the + Z direction from each adjustment imaging unit 620 a to 620 d, and thus moves so as not to interfere with each adjustment imaging unit 620 a to 620 d. Can be made. The adjustment imaging units 620a to 620d and the measurement imaging unit 640 capture an image of the test pattern TP displayed on the screen 500, and transmit the captured image data to the processing unit 610 (FIG. 2).
[0043]
The processing unit 610 processes the image data transmitted from the adjustment imaging units 620a to 620d and the measurement imaging unit 640, and obtains the characteristic value of the projection lens 480 by the method described below.
[0044]
B. Projection lens characteristics inspection:
FIG. 9 is a flowchart showing a series of processing procedures when the projection lens is inspected. In step S101, the focus state of the image displayed on the screen 500 is adjusted and the displayed image is aligned. In the process of step S101, four square local patterns PSa to PSd (FIG. 5) included in the test pattern TP of FIG. 4 are used. In step S 101, the light emitted from the light source device 410 in FIG. 3 is set to pass through the W filter in the color light filter 420. At this time, in the test pattern image displayed on the screen 500 in accordance with the image light emitted from the inspection sheet 450 in FIG. 4, the area corresponding to the translucent area of the test pattern TP is white (bright area) and corresponds to the light shielding area. This is a black and white image in which the area to be black is black (dark area).
[0045]
FIG. 10 is an explanatory diagram showing an image ITP of the test pattern TP (FIG. 4) displayed on the screen 500. However, the test pattern image ITP of FIG. 10 includes four square local pattern images IPSa to IPSd displayed according to the four square local patterns PSa to PSd included in the test pattern TP of FIG. Only the ruled line local pattern image IPL displayed according to the constituting ruled line local pattern PL is shown. Note that the four square local pattern images IPSa to IPSd are drawn considerably enlarged for convenience of explanation.
[0046]
When the test pattern image ITP is first displayed on the screen 500, the focus state may be poor and the image may be blurred. Therefore, in step S101 (FIG. 9), first, the focus state of the test pattern image ITP is adjusted. In this specification, “the focus state is good” means that the in-focus state is achieved, and “the focus state is bad” means that the in-focus state is not achieved.
[0047]
In the adjustment of the focus state, first, four square local pattern images IPSa to IPSd are respectively searched using the four adjustment imaging units 620a to 620d in FIG. In searching for the square local pattern images IPSa to IPSd, pattern information of the test pattern TP is input in advance to the processing unit 610, and an image region that substantially matches the pattern information of the square local patterns PSa to PSd is automatically detected by pattern matching. Is done by looking for. Or you may make it perform, confirming the image imaged with the imaging parts 620a-620d for adjustment by the user.
[0048]
When four square local pattern images IPSa to IPSd are found, the quality of the focus state of the four square local pattern images taken is checked. The quality of the focus state is determined using the captured image data. For example, by using the captured image data, the edge strength at the boundary between the white region (bright region) and the black region (dark region) of the black and white image can be examined, and the quality of the focus state can be determined based on the magnitude of the edge strength. . That is, by using a specific index value indicating the quality of the focus state such as the edge strength, it can be determined whether or not the in-focus state.
[0049]
When the in-focus index values for the square local pattern images IPSa to IPSd are obtained, the six-axis adjustment unit 460 is controlled based on the four in-focus index values, and the spatial arrangement of the inspection sheet 450 (test pattern TP) Adjust. Thereafter, the focus index values for the square local pattern images IPSa to IPSd are obtained again. In this manner, the focus index values for the four square local pattern images IPSa to IPSd are substantially equal while repeating the adjustment of the six-axis adjustment unit 460 and the calculation of the four focus index values, and the most The arrangement that increases is determined as the arrangement of the inspection sheet 450 in which the focus state of the test pattern image ITP is good.
[0050]
Also, as shown in FIG. 10, when the test pattern image ITP is first displayed on the screen 500, the center ITPc of the test pattern image ITP may be shifted from the center 500c of the screen 500. In the present embodiment, the center ITPc of the test pattern image means an intersection of two diagonal lines of a quadrangular area having apexes at the positions of the four square local pattern images IPSa to IPSd. In step S101 (FIG. 9), the image is aligned after the focus state of the image is adjusted.
[0051]
Specifically, the six-axis adjusting unit 460 is controlled so that the center ITPc of the test pattern image ITP shown in FIG. 10 coincides with the center 500c of the screen 500, and the arrangement of the inspection sheet 450 (test pattern TP) is adjusted. To do. In this embodiment, the arrangement of the inspection sheet 450 (test pattern TP) is adjusted so that the positions of the two square local pattern images IPSa and IPSb displayed on the screen 500 are substantially parallel to the X direction. Is done. In this way, even when the inspection sheet 450 is not properly attached to the predetermined position of the inspection sheet holding part 440, it can be corrected so that it is substantially attached to the predetermined position. Note that, when the images are aligned, the focus states of the four square local pattern images IPSa to IPSd are confirmed again.
[0052]
When the adjustment and alignment of the focus state of the test pattern image ITP is completed in step S101 (FIG. 9), the characteristics of the projection lens are inspected in steps S102 and S103.
[0053]
In step S102 (FIG. 9), the resolution of the image is measured as the characteristic value of the projection lens. In the process of step S102, the first measurement local patterns PM1 to PM20 (FIG. 6) included in the test pattern TP of FIG. 4 are used. However, in the measurement of image resolution, parallel line patterns PTAa to PTAh and PTBa to PTBd included in the first measurement local pattern (FIG. 6) are used. In the present embodiment, the image resolution is measured for each color light that has passed through the R filter, G filter, and B filter in the color light filter 420 (FIG. 3). However, when changing the color light filter, it is desirable to measure the resolution of the image after adjusting the focus state of the image of each color light. By doing so, it becomes possible to accurately determine the resolution of the image corresponding to each color light.
[0054]
FIG. 11 is an explanatory diagram showing parallel line pattern images included in the test pattern image displayed on the screen and changes in brightness of the parallel line pattern images. 11 is the same as the X direction of the test pattern image ITP displayed on the screen 500 shown in FIG.
[0055]
FIG. 11A-1 shows a parallel line pattern image IPTAd displayed according to the parallel line pattern PTAd included in the area WA of FIG. In the drawing, hatched areas indicate dark areas where light is blocked by the light blocking areas of the parallel line pattern PTAd, and other areas indicate bright areas. In FIG. 11A-1, the boundary between the bright region and the dark region is drawn clearly for convenience of illustration, but actually, the boundary gradually changes from the bright region to the dark region. Yes. FIG. 11A-2 shows a change in the intensity of light in the X direction obtained from the image data of FIG. 11A-1, and the dark region in FIG. 11A-1 has a relatively low intensity. Corresponding to the portion, the bright region corresponds to a portion having a relatively high intensity.
[0056]
Similarly, FIG. 11B-1 shows a parallel line pattern image IPTBa formed in accordance with the parallel line pattern PTBa included in the region WB of FIG. FIG. 11B-2 shows a change in light intensity in the X direction obtained from the image data of FIG.
[0057]
When the light intensity change as shown in FIGS. 11A-2 and B-2 is obtained, the MTF value (%), which is a value for evaluating the resolution of the image, is expressed by the following equation (1). Calculated by
[0058]
MTF = [(LMmax−LMmin) / (LMmax + LMmin)] × 100 (1)
[0059]
Here, as shown in FIGS. 11A-2 and 11B-2, LMmax is the maximum value of the light intensity in a region where the light intensity periodically changes, and LMmin is periodically This is the minimum value of the light intensity in the region where the light intensity changes.
[0060]
Note that the MTF value based on the light intensity change as shown in FIG. 11A-2 is an image when a dark region is displayed in the bright region of the image, as can be seen from FIG. 11A-1. Is required to evaluate the resolution. On the other hand, the MTF value based on the change in light intensity as shown in FIG. 11B-2 is an image when a bright area is displayed in the dark area of the image, as can be seen from FIG. 11B-1. Is required to evaluate the resolution. FIGS. 11A-2 and B-2 show a case where the MTF value is obtained based on such two types of changes in brightness, but at least one of them is required for evaluating the resolution of the image. What is necessary is just to obtain | require MTF value of the kind.
[0061]
Normally, the smaller the pitch of the parallel line pattern is, the smaller the amount of change in light intensity (LMmax−LMmin) as shown in FIGS. 11A-1 and B-1 is, and as a result, the MTF value is smaller. Tend to be. When the amount of change in light intensity is small, it becomes impossible to clearly distinguish the bright area and the dark area of the parallel line pattern image displayed on the screen. Therefore, when the MTF value obtained by the equation (1) is larger than a predetermined value, it can be determined that the image of the parallel line pattern is displayed well, while the MTF value is a predetermined value. If it is smaller, it can be determined that the image of the parallel line pattern is not displayed well.
[0062]
As described above, if the MTF values are sequentially obtained using the parallel line pattern images represented by the plurality of parallel line patterns included in the test pattern TP of FIG. You can know the resolution of the image that can be done. For example, when the MTF value for the parallel line pattern PTAa having a relatively large pitch in FIG. 6 is larger than a predetermined value and the MTF value for the parallel line pattern PTAd having a relatively small pitch is smaller than the predetermined value. It can be determined that the image can be displayed well up to the resolution corresponding to the pitch of the parallel line pattern PTAa.
[0063]
As shown in FIG. 6, in the test pattern TP of the present embodiment, parallel line patterns having different pattern orientations are provided in the areas WA and WB. Therefore, by using parallel line patterns with different orientations (for example, PTAb), it is possible to measure not only the resolution of the image in the X direction on the screen but also the resolution of the image in the Y direction. Further, the test pattern TP (FIG. 4) of the present embodiment includes second measurement local patterns PMC1 to PMC4 as shown in FIG. Therefore, if the second measurement local patterns PMC1 to PMC4 are used, the image in a direction (normal direction) different from the case where the parallel line patterns included in the first measurement local patterns PM1 to PM20 are used. It becomes possible to measure the resolution. Each parallel line pattern included in the first measurement local patterns PM1 to PM20 and the second measurement local patterns PMC1 to PMC4 corresponds to the first local pattern in the present invention. Thus, the first local pattern may be any pattern that forms periodic light and darkness in the image displayed on the screen.
[0064]
In the present embodiment, the MTF value is obtained using the parallel line patterns included in the first measurement local patterns PM1 to PM20 in each of the 20 blocks of FIG. In each block, MTF values for at least two types of parallel line patterns having different pitches included in the first local pattern for measurement are obtained. By comprehensively evaluating each MTF value obtained in this way, the resolution of the image is determined for the projection lens 480 to be inspected.
[0065]
Further, the projection lens 480 to be inspected in the present embodiment changes the arrangement of the lens system inside thereof (that is, the distance between the lenses) to change the size of the projected image to wide (middle) and middle. (Medium) and Tele (Small) can be changed to three stages. For this reason, in this embodiment, the resolution of the image is measured for each of the plurality of display magnifications of the projection lens 480. By doing so, it is possible to examine the characteristics relating to the resolution of the image of the projection lens 480 according to the state of use.
[0066]
As described above, in step S102, the MTF value is obtained using equation (1). However, another equation may be used as a value for evaluating the resolution of the image. For example, a formula obtained by adding a correction formula for correcting disturbance noise caused by light from the outside to Formula (1) may be used. In general, it is only necessary to determine a value related to the resolution of an image based on a periodic change in brightness of the image.
[0067]
In step S103 (FIG. 9), the flare (expansion amount) of the image is obtained as the characteristic value of the projection lens. Image flare occurs due to reflection of part of the image light inside the projection lens 480. That is, when part of the image light is reflected and emitted a plurality of times on the lens surface or the like inside the projection lens, the part of the image light may irradiate a region different from the region to be originally irradiated. At this time, the image displayed on the screen is larger than the image displayed when a part of the image light is not reflected. In step S103, the flare of such an image is measured.
[0068]
In the process of step S103, as in the process of step S102, the first local patterns for measurement PM1 to PM20 (FIG. 6) included in the test pattern TP of FIG. 4 are used. However, in step S103, only four types of small hole patterns PHa to PHd included in the region WB are used among the first measurement local patterns shown in FIG. Note that the flare measurement of the image of this embodiment is performed using only the white color light that has passed through the W filter in the color light filter 420 (FIG. 3), but the color light that has passed through the R filter, G filter, and B filter. You may make it perform.
[0069]
FIG. 12 is an explanatory diagram showing an example of a small hole pattern image included in the test pattern image displayed on the screen. FIG. 12 shows an image IPHa of the small hole pattern PHa (FIG. 6) displayed near the upper left of the screen 500 in FIG. 8. Note that the shape of the small hole pattern image IPHa is not limited to the egg shape as shown in FIG. 12, and may be various shapes depending on the projection lens.
[0070]
In the drawing, a substantially circular area HA1 indicates a bright area to be irradiated by the small hole pattern PHa when it is assumed that a part of the image light is not reflected inside the projection lens. The oval area HA2 including the area HA1 indicates a bright area irradiated by the small hole pattern PHa when a part of the image light is actually reflected inside the projection lens. The area BA outside the area HA2 indicates a dark area where no light is irradiated, and the bright area HA2 is isolated in the dark area BA. As can be seen from this description, each of the small hole patterns PHa to PHd (FIG. 6) of the present embodiment corresponds to the second local pattern in the present invention. Note that the second local pattern is not limited to the substantially circular small hole pattern as shown in FIG. 6, and patterns having other shapes may be used. The light intensity distribution in each region is relatively large in the region HA1, and relatively small in the region HA2 excluding the region HA1. In FIG. 12, for convenience of illustration, the boundaries of the areas HA1, HA2, and BA are clearly divided and drawn, but actually, the intensity of light gradually changes at the boundaries of the areas.
[0071]
In this embodiment, the flare E (%) of the image is given by the following equation (2).
[0072]
E = (S _HA2 / S _HA1 ) × 100 (2)
[0073]
Where S _HA1 Is the area of the region HA1 and S _HA2 Is the area of the region HA2 including the region HA1. Area S _HA1 Can be determined by using the area of the small holes of the small hole pattern PHa of FIG. 6 and the magnification of the image. Note that the image enlargement ratio is, for example, the distance between the two square local patterns PSa and PSd included in the test pattern TP in FIG. 4 and the two square local pattern images IPSa, included in the test pattern image ITP in FIG. And the distance between IPSd. In addition, area S _HA2 Can be obtained by binarizing imaged image data with a predetermined threshold as shown in FIG.
[0074]
As described above, in this embodiment, the flare E of the image is determined using the area of the region HA1 and the area of the region HA2, but other methods may be used. For example, the flare of the image may be determined using the area of the area HA1 and the area of the area HA2 excluding the area HA1. Or you may determine using the maximum value of the distance between 2 points on the outer periphery of area | region HA1 (namely, diameter of area | region HA1), and the maximum value of the distance between 2 points | pieces on the outer periphery of area | region HA2. In general, it is only necessary to determine a value related to image flare using an isolated bright region in the image.
[0075]
In the present embodiment, the flare of the image is measured using the small hole patterns included in the first measurement local patterns PM1 to PM20 in each of the 20 blocks in FIG. However, the flare E of the image tends to increase with increasing distance from the central axis of the projection lens, in other words, toward the periphery of the image displayed on the screen. Therefore, the flare of the image may be evaluated using only the small hole pattern image positioned around the test pattern image displayed on the screen.
[0076]
By using the characteristic value relating to the resolution of the image caused by the projection lens and the characteristic value relating to the flare of the image obtained in steps S102 and S103, the quality of the projection lens can be easily determined. In this embodiment, the characteristic values of the projection lens are sequentially measured in steps S102 and S103, but the measurement order is not limited.
[0077]
As described above, the projection lens inspection apparatus of the present invention calculates the characteristic value based on the change in brightness of the adjusted test pattern image after adjusting the focus state of the image displayed on the screen. This makes it possible to accurately inspect the characteristics of the projection lens.
[0078]
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0079]
(1) In the above embodiment, as shown in FIG. 2, the projection unit 400 including the inspection sheet 450 (FIG. 4) on which the test pattern TP is formed is used as the image light emitting unit. Instead, a liquid crystal light valve may be used. Even in this case, it is possible to emit image light representing a test pattern similar to the test pattern TP of FIG. 4 by supplying an image signal to the liquid crystal light valve. In addition, when a plurality of types of test patterns are used, the contents of the test patterns can be easily changed by supplying image signals corresponding to the test patterns.
[0080]
Further, in the above embodiment, the light source device 410 is provided in the projection unit 400, but the image light emitting unit may be configured without using the light source device 410. For example, if a high-intensity cathode ray tube is used as the image light emitting unit, the light source device can be omitted. When a high-intensity CRT is used, the contents of the test pattern can be easily changed according to the supplied image signal, as in the case of using the liquid crystal light valve.
[0081]
When a liquid crystal light valve or a high-intensity CRT is used, the image alignment in step S101 in FIG. 9 can also be performed by changing the display position of the test pattern on the liquid crystal light valve or the high-intensity CRT. .
[0082]
(2) In the above embodiment, the case where the screen 500 is a transmissive screen that displays an image on the back side of the projection surface has been described. However, a screen that displays an image on the projection surface side may be used. Good. However, in this case, care must be taken so that the display of the test pattern image on the screen is not hindered by the adjustment imaging unit, the measurement imaging unit, or the like. If the adjustment imaging units 620a to 620d, the measurement imaging unit 640, and the like are arranged on the back side of the projection surface using the transmission screen 500 as in this embodiment, a test pattern image can be easily captured. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of a projection display device.
FIG. 2 is an explanatory diagram showing an example of a projection lens inspection apparatus to which the present invention is applied.
FIG. 3 is an explanatory diagram showing a state when the projection unit 400 of FIG. 2 is viewed from the + T direction.
FIG. 4 is an explanatory diagram showing an inspection sheet 450 on which a test pattern TP is formed.
FIG. 5 is an explanatory diagram showing an enlargement of one square local pattern PSa included in the test pattern TP of FIG.
6 is an explanatory diagram showing an enlarged view of one first measurement local pattern PM1 included in the test pattern TP of FIG. 4;
7 is an explanatory diagram showing an enlarged view of one second measurement local pattern PMC1 included in the test pattern TP of FIG. 4;
FIG. 8 is an explanatory diagram showing the arrangement of the adjustment imaging units 620a to 620d and the measurement imaging unit 640 when the screen 500 is viewed from the + Z direction.
FIG. 9 is a flowchart showing a series of processing procedures for inspecting a projection lens.
10 is an explanatory diagram showing an image ITP of a test pattern TP (FIG. 4) displayed on the screen 500. FIG.
FIG. 11 is an explanatory diagram showing a parallel line pattern image included in a test pattern image displayed on a screen and changes in brightness of the parallel line pattern image.
12 is an explanatory diagram showing an example of an image of the small hole pattern of FIG. 6 displayed on the screen.
[Explanation of symbols]
20 ... Light source device
100: Illumination optical system
1000: Projection display device
200: Color light separation optical system
220: Relay optical system
300R, 300G, 300B ... Liquid crystal light valve
320 ... Cross dichroic prism
340 ... Projection lens
SC ... Screen
400 ... projection unit
410 ... Light source device
412 ... Light source lamp
414 ... Parabolic reflector
420 ... Color light filter
420c ... central axis
430, 442 ... Mirror (total reflection mirror)
440 ... Inspection sheet holder
450 ... Inspection sheet
460 ... 6-axis adjustment unit
470 ... Dummy prism
480 ... Projection lens (test lens)
500 ... Screen
500a ... Projection surface
500b ... display surface
510 ... Mirror (total reflection mirror)
600 ... Inspection department
610: Processing unit
620a to 620d ... Adjustment imaging unit
640 ... Measurement imaging unit
TP ... Test pattern
ITP ... Test pattern image
PSa to PSd: square local pattern
IPSa to IPSd ... square local pattern image
PL ... Ruled line local pattern
IPL ... Ruled line local pattern image
PM1 to PM20: First measurement local pattern
PMC1 to PMC4 ... second measurement local pattern
PTAa to PTAh: Parallel line pattern
PTBa to PTBd: parallel line pattern
IPTAd, IPTBa ... Parallel line pattern image
PHa to PHd: Small hole pattern
IPHa ... Small hole pattern image
n1 ... central axis
n2 ... Normal

Claims (5)

A projection lens inspection device for inspecting a projection lens used in a projection display device,
An image light emitting unit having a test pattern and emitting image light representing the test pattern;
A screen on which the image light is irradiated by the projection lens, and an image of the test pattern is displayed by the irradiation of the image light;
An imaging unit that captures an image of the test pattern displayed on the screen;
A focus state adjustment unit that automatically adjusts the focus state of the image of the test pattern;
A characteristic value calculation unit for calculating a characteristic value of the projection lens based on a change in brightness of the image of the test pattern;
Bei to give a,
The test pattern includes a first local pattern for forming an isolated bright region in an image of the test pattern,
The characteristic value of the projection lens, a projection lens, characterized in it to contain the value associated with the flare of the image is calculated by using the bright area of the image of the first local pattern displayed on the screen Inspection device. The projection lens inspection apparatus according to claim 1 ,
It said test pattern further includes a second local pattern for forming a periodic light and dark in the image before Symbol test pattern,
The characteristic value of the projection lens further comprises a pre-Symbol periodic brightness values for the resolution of the image that is determined based on the change of the previous SL second local pattern of an image displayed on a screen, the projection lens Inspection device. A projection lens inspection apparatus according to claim 1 or 2 ,
The projection lens inspection apparatus, wherein the focus state adjustment unit adjusts the focus state by adjusting a spatial position of the test pattern in the image light emitting unit. A projection lens inspection apparatus according to any one of claims 1 to 3 ,
The screen is a transmissive screen capable of observing an image from the back side of the projection surface on which image light is projected,
The imaging lens inspection device, wherein the imaging unit is disposed on the back side of the projection surface. A method for inspecting a projection lens used in a projection display device,
(A) emitting image light representing a test pattern;
(B) irradiating the screen with the image light by the projection lens, and displaying an image of the test pattern on the screen;
(C) capturing an image of the test pattern displayed on the screen;
(D) automatically adjusting the focus state of the image of the test pattern;
(E) calculating a characteristic value of the projection lens based on a change in brightness of an image of the test pattern;
Bei to give a,
The test pattern includes a first local pattern for forming an isolated bright region in an image of the test pattern,
The characteristic value of the projection lens, a projection lens, characterized in it to contain the value associated with the flare of the image is calculated by using the bright area of the image of the first local pattern displayed on the screen Inspection method.

Images