JPH116786A - Method and device for inspecting image plane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for processing by software and to obtain picked-up image without moire only with a simple optical member by inserting scattering transmission plate between a camera and an image plane under inspection, scattering the light and picking up the image. SOLUTION: The irradiated light from a diffusing irradiation light source 4 transmits through each picture element of an image plane under inspection 1 such as a liquid crystal panel and enters into a scattering transmission plate 5. At this point, the lights from the picture elements located in the proximity each other at the image plane under inspection 1 are mixed, further scattered, smoothed and outputted from the scattering transmission plate. Therefore, the profile of moire can be obscured. In this case, the scattering transmission plate 5 and the image plane under inspection 1 are respectively fixed and mounted on a frame 7a and a mounting stage 8, which are fixed to a structure member, and the position relationship becomes unchangeable. Since the picture elements are separated, the close provision is recommendable. A CCD camera 2 aligns the range to the image plane under inspection 1 so as to set the image pick-up range at the maximum value and aligns the focal-point position to the scattering transmission plate 5. Then, with the picked-up image of the CCD camera 2 being observed, the rectangular-wave voltage of a driving part 6 is adjusted, and the picked-up image without moere is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen inspection method and a screen inspection method for measuring the luminous intensity and transmittance of each pixel constituting an inspection target screen such as a liquid crystal panel, a color filter for a liquid crystal panel, and a shadow mask for a CRT. The present invention relates to an inspection device.

[0002]

2. Description of the Related Art A color filter (CF panel) used for a liquid crystal panel is red,
It is composed of 100 μm square pixels including three filters of blue and green rectangles. Further, a shadow mask used for a television has an arrangement of holes having a diameter of several tens of μm.

A screen inspection apparatus is an apparatus for inspecting a variation in light transmittance of each pixel constituting a liquid crystal panel or a color filter and a variation in diameter of each hole constituting a shadow mask. As shown in FIG. 1, the screen inspection apparatus generally includes a diffuse irradiation light source 4, a camera 2 that captures an image of the inspection target screen 1, and a processing unit 3 that processes an image captured by the camera 2. I have.

When the inspection is performed by the screen inspection apparatus, an arrangement of pixels constituting the inspection target screen 1 (spatial frequency) and an arrangement of pixels constituting the light receiving screen 2a of the camera 2 (spatial frequency).
If there is a deviation, moire occurs. For this reason, there is a problem that the defect cannot be distinguished from the defect of the inspection target screen 1 and, as a result, the inspection accuracy as a screen inspection device is reduced.

For this reason, conventionally, the positional deviation between the pixel to be inspected and the light receiving pixel is represented by a function of the position, a portion where moiré occurs is predicted, and a light receiving signal of the light receiving pixel corresponding to the moiré portion is ignored. There has been proposed an invention for reconstructing a screen to be inspected based on the light receiving signals of the remaining light receiving pixels (see JP-A-8-75542). However, in the technique described in Japanese Patent Application Laid-Open No. H8-75542, software for predicting a moiré-producing portion and reconstructing a screen to be inspected is required, and hardware for executing the software is also prepared. Must be performed, the configuration of the entire apparatus becomes complicated.

Therefore, it has been proposed to insert an optical low-pass filter between the screen to be inspected and the light receiving screen to spread the light passing through the screen to be inspected to the black mask portion of the screen to be inspected (Japanese Patent Application Laid-Open No. Hei 8-8). 32749
No. 6). According to this proposal, moire fringes can be reduced by a simple operation of inserting an optical low-pass filter.

However, the optical low-pass filter according to this proposal is described as "a birefringent plate for horizontal separation and a vertical separation is superposed between two wave plates for converting linearly polarized light into circularly polarized light. It has a five-layer structure in which the same wavelength plate as described above is sandwiched between the plates. "The glass is used for the wavelength plate, and quartz is used for the birefringent plate." Therefore, it is difficult to control the thickness,
Since processing is troublesome, it is expected that the optical low-pass filter will be very expensive.

Accordingly, the present invention provides a screen inspection method and a screen inspection apparatus capable of obtaining a captured image free from moiré by using only an optical member having a simpler structure, which does not require processing by software. The purpose is to realize.

[0009]

The screen inspection apparatus according to the present invention is a method of inserting a scattering transmission plate for scattering light at any position between a camera and a screen to be inspected to take an image. This method will be described with reference to FIG. FIG. 2 is a diagram illustrating a state in which the scattering transmission plate 5 is installed at a distance D from the inspection target screen 1. The camera is arranged above the scattering transmission plate 5 (not shown).

According to FIG. 2, light transmitted from each pixel of the inspection target screen 1 from a diffuse irradiation light source (not shown) placed below or light emitted from each pixel of the inspection target screen 1 is scattered and transmitted. Enter plate 5. At this time, the light from the pixels located close to each other on the inspection target screen 1 is mixed, and the mixed light is scattered in the scattering transmission plate 5.
Therefore, the light from the pixels in the vicinity of the inspection target screen 1 exits the scattering transmission plate 5 in a state where the light is smoothed. Due to this smoothing action, the moire contour can be blurred.

The distance D between the inspection target screen 1 and the scattering transmission plate 5
Is large, the light from the pixels of the inspection target screen 1 mixes with each other in a wide range, and the effect of blurring the moire contour increases. However, if the distance D is too large,
The pixels that make up the inspection target screen 1 cannot be separated. Ground glass as the scattering transmission plate,
A scattering type liquid crystal panel or an acrylic plate can be used (claims 2 and 4).

In particular, if a scattering type liquid crystal panel is used, the diffusion rate can be controlled by the voltage, so that changing the voltage has the same effect as changing the distance D between the screen to be inspected and the scattering transmission plate. Obtainable. Further, the screen inspection apparatus of the present invention is for performing the screen inspection method, and includes a camera that captures an inspection target screen, and a processing unit that processes an image signal captured by the camera. The screen inspection apparatus includes a scattering transmission plate fixing means for inserting the scattering transmission plate at any position between the camera and the inspection target screen.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 is a schematic diagram showing the configuration of the screen inspection device. The screen inspection apparatus includes a diffuse irradiation light source 4, a CCD camera 2 for imaging an inspection target screen 1 mounted on a mounting board 8, a processing unit 3 for processing an image captured by the CCD camera 2, It has a frame 7 having a concave cross section for fixing the scattering transmission plate 5, and a driving unit 6.

The inspection target screen 1 is selected from a liquid crystal panel, a color filter for a liquid crystal panel, a shadow mask for a CRT, and the like. The diffuse irradiation light source 4 is used to inspect
The light emitted from the light source passes through each pixel of the inspection target screen 1. If a screen whose light is to be inspected itself emits light, the diffuse illumination light source 4 is used.
Is unnecessary.

The CCD camera 2 has a resolution of about 3000 pixels × about 2000 pixels. In order to maximize the imaging range of the CCD camera 2, the CCD camera 2
And the distance between the screens 1 to be inspected. The focal position of the CCD camera is adjusted to the scattering transmission plate 5, but some deviation is allowed. For example, if the distance D between the inspection target screen 1 and the scatter transmission plate 5 is close to several millimeters, the measurement is performed by inserting the scatter transmission plate 5 while keeping the focus position on the inspection target screen 1. It is also possible.

The scattering transmission plate 5 is fixed to a frame 7a serving as "fixing means". The frame 7 a is fixed to a predetermined structural member of the screen inspection device together with the mounting board 8. Therefore, the positional relationship between the frame 7a and the mounting board 8 is unchanged, and therefore, the positional relationship between the scattering transmission plate 5 fixed to the frame 7a and the inspection target screen 1 placed on the mounting board 8 also remains unchanged. Become. The frame 7a may be installed at any position between the screen 1 to be inspected and the light receiving screen 2a of the camera. However, as described above, if the distance D is too large, the inspection may be performed. It becomes impossible to separate the pixels constituting the target screen 1 ", and therefore, it is preferable to install the target screen 1 close to the inspection target screen 1.

FIG. 4 is an enlarged perspective view of the frame 7a.
The cross section of a is concave, and the concaves are arranged facing each other. The scattering transmission plate 5 can be introduced between the concave portions. The structure of the frame is not limited to the above. For example, as shown in FIG. 5, a frame 7b having a convex cross section may be arranged to face sideways. In this case, the scattering transmission plate 5 can be fixed by placing it from above.

In the present embodiment, a scattering type liquid crystal panel is used as the scattering transmission plate 5. A scattering type liquid crystal is a liquid crystal that is arranged when voltage is applied, and is roughly divided into a phase change type liquid crystal (Nematic-Cholesteric Phase Transition Liq).
uid Crystal.), Polymer Dispersed Liquid Crystal (Polymer Disper)
sed Liquid Crystal, hereinafter referred to as "PDLC". Polyme
r Network Liquid Crystal (hereinafter referred to as “PN-LCD”).

In the present embodiment, a rectangular wave voltage is applied from the driving section 6. When this voltage is 0 V, the scattering state becomes maximum.
In DLC, it becomes transparent at 60V to 100V. Therefore, when the degree of occurrence of moiré is high while actually viewing the image captured by the CCD camera 2, the voltage is adjusted to a voltage at which moiré can be removed. The scattering effect at this time is the same as that of the ground glass of No. 2000. When measuring a defect in a minute area, the voltage can be adjusted so as to be in a state close to a transparent state.

However, in addition to the scattering type liquid crystal panel, a frosted glass or acrylic plate having a further simple structure can be used as the scattering transmission plate 5. The frosted glass has a number of 1000 to 2000 and a thickness of about 2 mm. The distance D between the inspection target screen 1 and the scattering transmission plate 5 is 1 mm.
By doing so, moire can be removed. As the acrylic plate, a milky white one having a thickness of about 0.1 mm to about 0.5 mm is used. Since the acrylic plate is scattered throughout the inside of the plate, it can be directly installed on the inspection target screen 1.

When an image of a screen to be inspected is imaged using the screen inspection apparatus described above, a smoothing action of the scattering transmission plate is obtained.
It is possible to take an image by blurring the outline of moiré.

[0022]

【Example】

<Comparative Example> A circular zone plate (hereinafter, referred to as “CZP”) using a conventional inspection apparatus (a focal length f of a lens f = 50 mm, an aperture F = 5.6) without using a scattering transmission plate.
As a result, as shown in FIG. 6, three virtual images due to moire appeared in addition to the real image of CZP. Further, the contrast of the image of the unevenness in the left half from the center is low, making it difficult to identify. When the light intensity was plotted along the horizontal axis F of the imaging screen and graphed, a striped graph as shown in FIG. 7F was obtained. <Example> When a CZP was imaged using a screen inspection apparatus using frosted glass (No. 2000) of the present invention (distance D from inspection screen 1 = 1 mm), a virtual image of moire as shown in FIG. No screen was obtained. When the light intensity was plotted along the horizontal axis G of this imaging screen and graphed, a graph as shown in FIG. 7G was obtained.

From the examples and comparative examples, it can be seen that moiré cannot be sufficiently removed without using a scattering transmission plate, but can be removed using a scattering transmission plate. Also, it can be seen that the stripe pattern of CZP is smoothed by the scattering transmission plate.

[0024]

As described above, according to the screen inspection apparatus of the present invention, a moire-free picked-up image can be obtained by using the inexpensive and simple structure of the scattered transmission plate, and the inspection accuracy of the inspection target screen can be improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a conventional screen inspection apparatus.

FIG. 2 is a diagram for explaining a method of the present invention in which a scattering transmission plate that scatters light is inserted into any position between a camera and a screen to be inspected to capture an image.

FIG. 3 is a schematic diagram illustrating a configuration of a screen inspection device.

FIG. 4 is a perspective view of a frame as a scattering transmission plate fixing means.

FIG. 5 is a perspective view showing another specific example of the frame serving as the scattering transmission plate fixing means.

FIG. 6 is a diagram showing a screen obtained by imaging a CZP using a conventional screen inspection apparatus that does not use a scattering transmission plate.

7 is a graph in which light intensity is plotted along a horizontal axis F of the imaging screen of FIG. 6 and a horizontal axis G of the imaging screen of FIG. 8, where the horizontal axis represents the position of a pixel and the vertical axis represents the light intensity. .

FIG. 8 is a diagram showing a screen obtained by imaging a CZP using the screen inspection apparatus using the scattering transmission plate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 inspection target screen 2 CCD camera 3 processing unit 4 diffused irradiation light source 5 scattering transmission plate 6 drive unit 7a, 7b frame 8 mounting board

Claims (4)

[Claims] 1. A method for inspecting a screen to be inspected using a screen inspection apparatus including a camera for imaging a screen to be inspected, and a processing unit for processing an image signal captured by the camera, comprising: A method for inspecting a screen, comprising: inserting a scattering transmission plate that scatters light at any position between the screen and an inspection target screen; 2. The screen inspection method according to claim 1, wherein the scattering transmission plate is a ground glass, a scattering type liquid crystal panel or an acrylic plate. 3. A screen inspection apparatus comprising: a camera for capturing an image of an inspection target screen; and a processing unit for processing an image signal captured by the camera. A screen inspection apparatus, comprising: a scattering transmission plate fixing means for inserting a scattering transmission plate at a position. 4. The screen inspection apparatus according to claim 3, wherein the scattering transmission plate is a ground glass, a scattering type liquid crystal panel or an acrylic plate.