JP2009025593A - Inspection method of optical compensation plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inspect an optical compensation plate to be mounted to a liquid crystal projector in a simple method, for example. <P>SOLUTION: White circles indicate the contrast of a liquid crystal projector mounted with an optical compensation plate of a small phase difference, and black circles indicate the contrast of a liquid crystal projector mounted with an optical compensation plate of a large phase difference. Based on such phase differences of the optical compensation plates and actual measurement values of the contrasts, a correlation between the phase differences of the plurality of optical compensation plates and the contrasts of the images projected by the liquid crystal projectors mounted with these optical compensations plates is acquired. Here, the correlation coefficient (R<SP>2</SP>=0.9043) showing the correlation between the phase differences and contrasts in a range where the phase differences of the optical compensation plates are large is larger than the correlation coefficient (R<SP>2</SP>=0.6421) when the phase differences are small. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field of an optical compensator inspection method capable of inspecting in advance an optical compensator used for a light valve in order to increase the contrast of a projection display device such as a liquid crystal projector.

  In this type of display device, a microlens array or a microlens array plate may be used in combination in order to increase the utilization efficiency of incident light incident on a liquid crystal device used as a light valve. In this case, the light incident perpendicularly to the liquid crystal layer is incident on the liquid crystal layer obliquely at different angles for light collection by the microlens array. When light is incident on the liquid crystal layer from an oblique direction, the phase is shifted, leading to a decrease in contrast and a narrowing of the viewing angle. From such a background, the liquid crystal device provided with the microlens array has an optical compensator that can prevent a decrease in contrast and increase a viewing angle by compensating for a phase difference of light that has shifted in phase. Used. In a liquid crystal device using such an optical compensator, the optical compensator is disposed in the liquid crystal device or by a display device in which the optical compensator is disposed as part of the optical system of the projection display device. The compensation effect of the optical compensator was evaluated by evaluating the contrast of the displayed projected image. Non-Patent Document 1 discloses an example of a phase difference measuring apparatus that measures the phase difference of an optical compensator.

Oji Scientific Instruments phase difference measurement device http://www.oji-keisoku.co.jp/products/kobra/theory.html

  However, when the number of optical compensators arranged in the optical system increases, it is difficult to identify an optical compensator that causes a decrease in contrast among a plurality of optical compensators. Even so, there is a problem that the labor and time required for the identification increase and the burden required for the inspection increases.

  In addition, the performance of an optical compensator having an inclined refractive index ellipsoid is usually determined by the phase difference (front phase difference) of the emitted light detected in front of the optical compensator, but is displayed by the projection display device. The correlation between the contrast of the image and the front phase difference is small, and it is difficult to say that the front phase difference is suitable as an index to be referred to when evaluating the optical compensator. In addition, at the manufacturing stage of the optical compensator, there is a problem that the measured front phase difference variation is small and it is determined that the optical characteristics of the manufactured optical compensators are uniform with each other. Therefore, it is difficult to evaluate the influence of the optical characteristics of the optical compensation plate on the contrast of the image before mounting the optical compensation plate on the projection display device, and to judge the quality of the optical compensation plate based on the evaluation. Met.

  Therefore, the present invention has been made in view of the above problems and the like. For example, whether or not the optical compensator is a good product before being mounted on a projection display device such as a liquid crystal projector, that is, the optical compensator. It is an object of the present invention to provide an inspection method for an optical compensator that can determine whether or not a projection display device including the above can display an image with high contrast.

  In order to solve the above-described problem, the optical compensator inspection method according to the present invention has a gradient refractive index ellipsoid and irradiates one surface of the first optical compensator to be inspected with inspection light. And the optical path of the inspection light so that the detection direction for detecting the outgoing light emitted from the other surface of the first optical compensation plate is along the direction in which the major axis of the inclined refractive index ellipsoid extends. Based on the second step of tilting the first optical compensator and rotating the first optical compensator about the optical path, and the phase difference of the first optical compensator in the extending direction, the first optical compensator A third step of determining whether the compensation plate is good or bad.

  According to the method for inspecting an optical compensator according to the present invention, the first optical compensator to be inspected functions as a retardation plate in a projection display device including a liquid crystal panel as a light valve, for example. Compensates for the phase difference between the light incident on or emitted. Such an inclined refractive index ellipsoid of the first optical compensator has refractive index anisotropies in which the major and minor axes have different refractive indexes. Therefore, the polarization state of the light emitted from the optical compensator depends on the incident angle of the light incident on the refractive index ellipsoid and the detection direction for detecting the outgoing light emitted from the gradient refractive index ellipsoid. Different. Therefore, when the light transmittance is measured in a state where the polarizer and the detector are arranged on one side and the other side of the first optical compensator plate, the incident angle and the detection direction described above are measured. Depending on each, the light transmittance differs from each other.

  Therefore, in the second step, with respect to the optical path of the inspection light, the detection direction for detecting the emitted light emitted from the other surface of the first optical compensation plate is along the direction in which the major axis of the gradient refractive index ellipsoid extends. By tilting the first optical compensation plate and rotating the first optical compensation plate around the optical path of the inspection light, the first optical compensation plate in the detection direction along the direction in which the major axis of the refractive index ellipsoid extends is extended. Identify the phase difference.

  In the third step, the quality of the first optical compensator is determined based on the phase difference of the first optical compensator in the direction in which the major axis of the gradient refractive index ellipsoid extends. Such a phase difference is the direction in which the first optical compensator is rotated, that is, the azimuth angle direction in which the direction in which the major axis of the refractive index ellipsoid extends is projected on one of the surfaces of the first optical compensator. 2 corresponds to the angle at which the major axis of the refractive index ellipsoid is inclined with respect to the optical path of the inspection light. In the present invention, the refractive index of the first optical compensator is determined based on the front phase difference due to the characteristics of the refractive index ellipsoid, that is, the refractive index anisotropy, based on the experiment of the present inventor. The first optical compensator is more accurately determined based on the phase difference specified in the direction in which the major axis of the ellipsoid extends, that is, in the state where the first optical compensator is inclined with respect to the optical path of the inspection light. It is known that it can be judged whether it is good or bad.

  Therefore, according to the method of inspecting an optical compensator according to the present invention, the first optical compensator alone is mounted on the first optical compensator without mounting the first optical compensator on a projection display device such as a liquid crystal projector. The quality can be determined, and the first optical compensator to be inspected can be selected in the manufacturing process of the first optical compensator. Therefore, the burden required for the inspection of the first optical compensator can be reduced as compared with the case where the inspection is performed with the projection display device mounted. In addition, since only the phase difference is measured, it is possible to perform an inspection with reduced labor in a short time without evaluating the contrast of the image displayed by the projection display device.

  In addition, according to the optical compensator inspection method of the present invention, the first optical compensator need only be subjected to an appearance inspection in addition to the inspection based on the above-described phase difference, so that the manufacturing cost of the optical compensator can be reduced. . In addition, when the first optical compensator is inspected with an image displayed on the projection display device, the light source of the projection display device may be damaged, but the optical compensator according to the present invention is inspected. According to the method, since the first optical compensator to be inspected can be inspected without using a high-output light source, the safety of the inspection can be ensured.

  In one aspect of the optical compensator inspection method according to the present invention, prior to the first step, an image projected by a projection display device including a second optical compensator of the same type as the first optical compensator is used. And a fourth step of acquiring data specifying the relationship between the contrast and the phase difference of the second optical compensator specified in the direction in which the major axis of the refractive index ellipsoid of the second optical compensator extends. In the third step, the quality may be determined based on whether a contrast corresponding to a phase difference of the first optical compensator in the data is equal to or higher than a predetermined contrast.

  According to this aspect, prior to the first step, the contrast of the image projected by the projection display device including the second optical compensation plate of the same type as the one optical compensation plate, and the refractive index of the second optical compensation plate are included. Data specifying the relationship with the phase difference of the second optical compensator specified in the direction in which the long axis of the ellipsoid extends is acquired. Here, “the same type of second optical compensation plate” refers to an optical compensation plate having the same design specifications as the first optical compensation plate to be inspected. That is, in the fourth step, data referred to for determining whether the first optical compensator to be inspected is good or bad is obtained in advance for the optical characteristics of the second optical compensator, in other words, the phase difference and contrast. Keep it. Such data includes, for example, the phase differences of a plurality of second optical compensators obtained by a procedure similar to the procedure for specifying the phase difference of the first optical compensator, and a projection on which these second optical compensators are mounted. The image displayed by the type | mold display apparatus shows the correlation with contrast. In particular, in this aspect, according to the experiment by the inventors of the present application, the correlation between the front phase difference of the plurality of second optical compensators and the contrast of the image displayed by the projection display device equipped with the second optical compensators is determined. In comparison, the correlation between the phase difference specified in the direction in which the major axis of the refractive index ellipsoid extends for each of the plurality of second optical compensation plates and the contrast of the image displayed by the projection display device is high. ing. Therefore, in the third step, the contrast corresponding to the phase difference of the first optical compensator in the data acquired in advance is individually specified based on the predetermined contrast, that is, the display performance required for the projection display device. When the contrast is equal to or higher than the set contrast, it is determined that the second optical compensation plate is a non-defective product.

  Therefore, according to this aspect, it is only necessary to determine whether or not the phase difference of the first optical compensator to be inspected is for a contrast having a predetermined contrast or higher in previously acquired data. The quality of the board can be determined.

  In another aspect of the optical compensator inspection method according to the present invention, in the first step, the inspection light is light obtained by polarizing light source light with a polarizer disposed on the one surface side, In the second step, the emitted light may be detected by a light receiving means via an analyzer disposed on the other surface side.

  According to this aspect, in the first step, for example, the light source light having a certain wavelength is irradiated onto the polarizer, and the light polarized by the polarizer, that is, the polarized light is irradiated onto the first optical compensator as inspection light. .

  In the second step, for example, the polarizer and the analyzer are positioned so that the optical axes of the polarizer and the analyzer are parallel (so-called parallel Nicols arrangement) or orthogonal (so-called crossed Nicols arrangement). In this state, the phase difference of the first optical compensator is measured by detecting the outgoing light transmitted through the detector by the light receiving means. Note that the light transmittance of the first optical compensation plate measured when specifying the phase difference depends on the tilt angle and the rotation angle at which the first optical compensation plate is tilted or rotated. In this measurement mode for measuring light transmittance, in other words, whether the phase difference is specified at an angle at which the light transmittance is increased or the phase difference is specified at an angle at which the light transmittance is decreased. They differ from each other depending on the mutual relationship between the optical axes of the children, that is, whether it is a parallel Nicols arrangement or a crossed Nicols arrangement.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, embodiments of an inspection method for an optical compensator according to the present invention will be described with reference to the drawings.

<1: Projection display device>
First, a configuration of a liquid crystal projector as an example of a projection display device in which an optical compensation plate to be inspected in the optical compensation plate inspection method according to the present embodiment is mounted with a liquid crystal panel will be described with reference to FIG. . FIG. 1 is a plan view showing a configuration of a liquid crystal projector which is an example of a projection display device equipped with an optical compensation plate to be inspected in the optical compensation plate inspection method according to the present embodiment.

  As shown in FIG. 1, a projector 1100 includes a lamp unit 1102 made of a white light source such as a halogen lamp. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and serves as a light valve corresponding to each primary color. The light enters the liquid crystal panels 1110R, 1110B, and 1110G.

  The configurations of the liquid crystal panels 1110R, 1110B, and 1110G are the same as those of the liquid crystal device described above, and are driven by R, G, and B primary color signals supplied from the image signal processing circuit. The light incident on or emitted from these liquid crystal panels is optically compensated. Light emitted from the optical system including the liquid crystal panel enters the dichroic prism 1112 from three directions. In this dichroic prism 1112, R and B light is refracted at 90 degrees, while G light travels straight. Accordingly, as a result of the synthesis of the images of the respective colors, a color image is projected onto the screen or the like via the projection lens 1114.

  Here, paying attention to the display images by the liquid crystal panels 1110R, 1110B, and 1110G, the display image by the liquid crystal panel 1110G needs to be horizontally reversed with respect to the display images by the liquid crystal panels 1110R, 1110B.

  Since light corresponding to the primary colors R, G, and B is incident on the liquid crystal panels 1110R, 1110B, and 1110G by the dichroic mirror 1108, it is not necessary to provide a color filter.

  In such a projector 1100, optical compensators inspected by an inspection method described later are disposed as retardation plates on the light incident side and the light exit side of the liquid crystal panels 1110R, 1110G, and 1110B, respectively. Optical compensation is possible on each of the side and the light exit side. Therefore, in the projector 1100, the contrast of the projected image projected on a projection surface such as a screen is increased, and a high-quality image can be displayed.

  The contrast described later is specified by measuring the contrast of an image displayed by a projection display device such as the projector 1100.

<2: Configuration of optical compensator>
Next, a schematic configuration of the optical compensation plate to be inspected in the optical compensation plate inspection method according to the present embodiment will be described with reference to FIGS. FIG. 2 is a perspective view showing a schematic configuration of the optical compensation plate, and FIG. 3 is a schematic configuration diagram schematically showing a detailed configuration of the optical compensation plate.

  As shown in FIGS. 2 and 3, the optical compensation plate 100 as an example of the “first optical compensation plate” of the present invention includes a substrate 103 and a gradient index ellipsoid 102 existing on the substrate 103. Has been. The angle formed by the projection component obtained by projecting the major axis of the gradient refractive index ellipsoid 102 onto the surface 101 and the axis Q2 passing through the center C of the surface 101, that is, the major axis of the refractive index ellipsoid 102 in the plane of the surface 101 extends. The direction is defined by the azimuth angle θ. The major axis of the gradient refractive index ellipsoid 102 is inclined at a polar angle φ with respect to the normal line Q 1 of the optical compensation plate 100. Therefore, the direction in which the major axis of the gradient refractive index ellipsoid 102 extends is defined by the azimuth angle θ and the polar angle φ, and the angle at which the optical compensation plate 100 is irradiated with the inspection light and the optical compensation plate 100 In accordance with the difference in detection direction for detecting the emitted light, the phase difference of the emitted light is different from each other, and the transmittance of light detected by the photodetector via the analyzer changes.

  Therefore, as will be described later, in the optical compensation plate inspection method according to the present embodiment, the emitted light emitted from the optical compensation plate 100 is detected in the detection direction along the direction in which the major axis of the refractive index ellipsoid 102 extends. Thus, the phase difference of the optical compensation plate 100 is specified.

  In FIG. 3, the optical compensation plate 100 is configured to include the substrate 103 and the refractive index ellipsoid 102, but the substrate 102 is also a member on a flat plate configured to include the inclined refractive index ellipsoid 102. For convenience of explanation, the gradient index ellipsoid 102 and the substrate 103 are distinguished from each other in order to explain the direction in which the major axis of the gradient index ellipsoid 102 extends.

<3: Inspection method for optical compensation plate>
Next, an optical compensation plate inspection method according to this embodiment will be described with reference to FIGS. 4 to 7. FIG. 4 is a schematic configuration diagram schematically showing the configuration of an inspection apparatus capable of executing the optical compensation plate inspection method according to the present embodiment. FIG. 5 is a flowchart showing the main steps of the optical compensation plate inspection method according to the present embodiment. FIG. 6 is a graph showing the results of an experiment conducted by the inventor of the present application.

  In FIG. 5, an inspection apparatus 210 includes a light source 201 that can emit light of a constant wavelength, a polarizer 202, an analyzer 203, and a photodetector 204 that is an example of the “light receiving unit” of the present invention. It is configured. The optical compensation plate 100 to be inspected is disposed between the polarizer 202 and the detector 203 at the time of the inspection.

  At the time of inspection of the optical compensator 100, the light source light P1 emitted from the light source 201 enters the polarizer 202 along the optical path R1, and optically compensates along the optical path R1 as inspection light P2 polarized by the polarizer 202. The plate 100 is irradiated. The optical compensator 100 compensates the phase difference of the inspection light P2 by the refractive index anisotropy corresponding to each of the major axis and the minor axis of the refractive index ellipsoid 102, and emits the emitted light P3 toward the analyzer 203. . The photodetector 204 detects the outgoing light P3 polarized by the analyzer 203, and measures the light transmittance in the optical compensation plate 100.

  In the inspection method according to this embodiment to be described later, at the time of inspection of the optical compensation plate 100, first, the polarizer 202 and the analyzer 203 are set so that the normal line Q1 and the optical path R1 of the optical compensation plate 100 shown in FIG. After the optical compensation plate 100 is disposed therebetween, the optical compensation plate 100 is rotated around the optical path R1. In parallel with this, by rotating the optical compensator 100 about the rotation axis R2 coinciding with the axis Q2 described in FIG. 2, the emitted light P3 is detected while the optical compensator 100 is inclined with respect to the optical path R1. Then, the phase difference of the optical compensation plate 100 is specified based on the angle dependency of the light transmittance.

  More specifically, in this embodiment, the polarizer 202 and the detector 203 are arranged so that the optical axes of these polarizing plates are orthogonal to each other. That is, in the present embodiment, the polarizer 202 and the analyzer 203 are arranged in a crossed Nicols arrangement. In the inspection method to be described later, the rotation angle and the angle at which the illuminance of the light detected by the photodetector 204 is highest are specified by rotating and tilting the optical compensation plate 100. The detection direction specified by each of the rotation angle and the inclination angle (that is, the angle indicating the inclination of the optical compensation plate 100 with respect to the optical path R1) specified in this way is the refractive index ellipsoid 102. It coincides with the direction in which the long axis extends. In the present embodiment, the phase difference of the optical compensator 100 is determined based on the rotation angle and tilt angle of the optical compensator 100 specified in this way, and the light transmittance measured according to the rotation angle and tilt angle. Identify.

  The polarizer 202 and the detector 203 may be arranged in parallel Nicols so that their optical axes are parallel to each other. In this case, the phase difference of the optical compensation plate 100 is specified by the light transmittance measured according to the rotation angle and the inclination angle at which the illuminance of the light detected by the photodetector 204 is the lowest.

  Next, an optical compensation plate inspection method according to this embodiment will be described with reference to FIGS. 5 and 6.

  As shown in FIG. 5, in step S10, which is an example of the “fourth step” according to the present invention, an optical compensator of the same type as the optical compensator 100, that is, an example of the “second optical compensator” of the present invention is provided. The contrast of the image projected by the projection display device such as a liquid crystal projector, and the phase difference of the optical compensator specified in the direction in which the major axis of the inclined refractive index ellipsoid of the optical compensator of the same kind described above extends. The data specifying the relationship is acquired in advance. In step S 10, the optical compensator for which the contrast and phase difference of the image are specified includes the inclined refractive index ellipsoid 102 similar to that of the optical compensator 100, and has the same design specifications as the optical compensator 100. An optical compensator. In step S10, the phase difference of such an optical compensation plate is specified by an inspection method similar to the inspection method for inspecting the optical compensation plate 100 in advance prior to step S11. In addition, the correlation between the contrast and the phase difference is specified by measuring the contrast in the liquid crystal projector.

More specifically, for example, the data shown in FIG. 6 is acquired in advance by the present inventor. The data shown in FIG. 6 shows the relationship between the phase difference of the optical compensator when a plurality of optical compensators are inspected by irradiating the inspection light, and the contrast of the liquid crystal projector equipped with the retardation plate. . In FIG. 6, ○ indicates data when the optical compensator is irradiated with inspection light from the front during the inspection, and ● indicates inspection with the optical compensator inclined with respect to the optical path of the inspection light during the inspection Data. That is, the correlation between the phase difference and the contrast of the display image is obtained for each tilt angle of the stage on which the optical compensation plate is placed during inspection. Here, when the tilt angle of the stage is large (● in the figure), the correlation coefficient (R ² = 0.9043) indicating the correlation between the phase difference and the contrast is small when the tilt angle is small (◯ in the figure), that is, in front. It has been found by experiments by the inventor of the present application that it is larger than the correlation coefficient (R ² = 0.6421) of the phase difference and contrast of the stage in a state where the phase difference is observed. Therefore, the optical compensator 100 can be easily inspected by determining whether the optical compensator 100 is good or bad within a range of an inclination angle having a large correlation coefficient with contrast.

  Here, with reference to FIG. 6, the quality determination procedure of the optical compensation plate 100 will be described in detail. More specifically, for example, a case where the optical compensator 100 that generates a contrast equal to or higher than the contrast A0 in FIG. In FIG. 6, when the contrast A1 in the correlation line L1 corresponding to the phase difference B1 specified for the optical compensator 100 is greater than or equal to the contrast A0, the optical compensator 100 is determined to be a non-defective product. Therefore, by acquiring the data shown in FIG. 6 in advance, the quality of the optical compensator 100 can be accurately determined. That is, the optical compensator 100 can be inspected without performing inspection with the optical compensator 100 mounted on the projection display device.

  Next, in step S11 which is an example of the “first step” of the present invention, the inspection light P2 is irradiated from one surface side of the optical compensation plate 100, that is, the side facing the polarizer 202.

  Next, in parallel with step S11, in step S12, which is an example of the “second step” of the present invention, the optical compensator 100 is rotated about the optical path R1 and tilted with respect to the optical path R1. The other surface of the compensation plate 100, that is, the emitted outgoing light P <b> 3 facing the analyzer 203 is detected along the direction in which the major axis of the gradient refractive index ellipsoid 102 extends. In this way, the phase difference when the optical compensation plate 100 is tilted along the major axis of the gradient refractive index ellipsoid 102 is specified.

  Next, in step S14, which is an example of the “third step” of the present invention, the quality of the optical compensator 100 is determined based on the phase difference of the optical compensator 100 and the previously acquired data shown in FIG. The procedure for determining whether the optical compensator 100 is good or bad is based on the procedure already described with reference to FIG.

  Therefore, according to the inspection method of the optical compensator according to the present embodiment, the phase difference of the optical compensator 100 to be inspected corresponds to a contrast having a predetermined contrast or higher, for example, a contrast A0 or higher, in previously acquired data. It is possible to determine whether the optical compensator 100 is good or bad simply by determining whether or not it is being performed.

  Therefore, it is possible to determine whether the optical compensation plate 100 is acceptable or not by mounting the optical compensation plate 100 to be inspected on a projection display device such as a liquid crystal projector alone. In this manufacturing process, the optical compensation plate 100 can be selected. Therefore, the burden required for the inspection of the optical compensation plate 100 can be reduced as compared with the case where the inspection is performed in a state where it is mounted on the projection display device. In addition, since only the phase difference is measured for the optical compensator 100 to be inspected, it is possible to perform an inspection with reduced labor in a short time without evaluating the contrast of the image displayed by the projection display device. become.

  In addition, according to the method for inspecting an optical compensator according to the present embodiment, the optical compensator 100 only needs to be subjected to an appearance inspection in addition to the inspection based on the above-described phase difference, thereby reducing the manufacturing cost of the optical compensator. it can. In addition, when the optical compensation plate 100 is inspected in a state where an image is displayed on the projection display device, the light source of the projection display device may be damaged. However, the optical compensation plate according to the present embodiment is inspected. According to the method, since the optical compensator 100 to be inspected can be inspected without using a high-output light source, the safety of the inspection can be ensured.

It is a top view which shows the structure of an example of the projection type display apparatus with which the optical compensation board test | inspected by the inspection method of the optical compensation board which concerns on this embodiment was integrated in the optical system. It is the perspective view which showed an example of schematic structure of the optical compensator inspected by the inspection method of the optical compensator concerning this embodiment. It is the schematic block diagram which showed typically the detailed structure of the optical compensator inspected by the inspection method of the optical compensator concerning this embodiment. It is the schematic block diagram which showed typically the structure of the inspection apparatus which can perform the inspection method of the optical compensator which concerns on this embodiment. It is the flowchart which showed the main processes of the inspection method of the optical compensation board concerning this embodiment. It is the graph which showed the experimental result which this inventor performed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Optical compensator, 102 ... Refractive index ellipsoid, 201 ... Light source, 202 ... Polarizer, 203 ... Analyzer, 210 ... Inspection apparatus

Claims (3)

A first step of irradiating one surface of the first optical compensator to be inspected with inspection light having an inclined refractive index ellipsoid;
With respect to the optical path of the inspection light, the detection direction for detecting the outgoing light emitted from the other surface of the first optical compensation plate is along the direction in which the major axis of the inclined refractive index ellipsoid extends. A second step of tilting the optical compensator and rotating the first optical compensator about the optical path;
An inspection method for an optical compensator, comprising: a third step of determining pass / fail of the first optical compensator based on a phase difference of the first optical compensator in the extending direction. Prior to the first step, the contrast of the image projected by the projection display device having the second optical compensation plate of the same type as the first optical compensation plate, and the gradient refractive index ellipsoid of the second optical compensation plate A fourth step of acquiring data specifying the relationship with the phase difference of the second optical compensator specified in the direction in which the major axis extends,
2. The quality determination according to claim 1, wherein in the third step, the quality is determined based on whether or not a contrast corresponding to a phase difference of the first optical compensator in the data is equal to or higher than a predetermined contrast. Inspection method for optical compensation plate. In the first step, the inspection light is light in which light source light is polarized by a polarizer disposed on the one surface side,
The optical compensation plate inspection according to claim 1 or 2, wherein in the second step, the emitted light is detected by a light receiving means via an analyzer disposed on the other surface side. Method.

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