JP2010032986A - Focus positioning device and focus positioning method for liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image quality adjustment/inspection method for a projection image by a new irradiation method using fiber illumination. <P>SOLUTION: Light emitted from a light source is separated into RGB, each color luminous flux is divided into at least four, and each divided light is projected onto each color liquid crystal panel so as to be projected onto the four corners of a screen. Each divided light is emitted from a fiber emission part 25 in a liquid crystal panel holding part 6, reflected by a mirror 38, passes through a diffusion sheet 39 and a polarizing plate 40, and is projected onto the liquid crystal panel 41 held in front of the dichroic prism 42 of an optical unit 1. Images projected onto the four corners of the screen are imaged by color cameras arranged in respective positions. The brightness data of the imaged image is integrated in X and Y directions, to obtain dispersion of the integrated value. A focus value showing the degree of focusing is calculated from the dispersion value and the position and rotational angle of the liquid crystal panel are determined on the basis of the calculated focus value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a focus positioning apparatus and positioning method for a liquid crystal panel for adjusting the position of a liquid crystal panel of an optical system of a projection display device, which is necessary in the assembly manufacturing / inspection process of a light valve of a liquid crystal projector. With the downsizing of the LCD panel, the LCD panel has a low aperture ratio and it is difficult to ensure the brightness of the projected image.It is equipped with an illumination optical system that can ensure the brightness of the projected image. The present invention relates to a focus positioning device and a positioning method for a liquid crystal panel that can search for a true focus surface from a plurality of panel focus positions by analysis.

  In general, a liquid crystal projector uses three liquid crystal panels, red (R), green (G), and blue (B), to create a monochromatic image, and then synthesizes R, G, and B monochromatic images on a dichroic prism. To create a projected image.

  In the assembly and adjustment process of the LCD projector, the green projected image with the clearest color contrast is used as the reference position, and the remaining red and blue projected images are matched as much as possible to the corresponding projected pixel positions of the displayed green. Overlapping the image (convergence adjustment), then the position where the projected pixels on the projected surface projected with a single color are the least blurred at this position, and the projected pixels of each color and the pixel separation are the clearest In addition, it is necessary to adjust the position of each color liquid crystal panel (focus adjustment).

In the conventional assembly / adjustment process, four color cameras have been arranged at the four corners of the projection screen so as to image the corresponding portions, and focus adjustment has been performed using the integrated image output (for example, Non-Patent Document 1). reference). In the automatic focus positioning apparatus disclosed in Non-Patent Document 1, radiation light from an ultrahigh pressure mercury lamp separated into three colors of R, G, and B is incident on three liquid crystal panels corresponding to each color. Images are generated independently, and the images are synthesized by a dichroic prism and projected on a screen. Then, the four corners of the projected image on the screen are acquired by four color cameras while moving the liquid crystal panel in the Z direction (normal direction of the surface of the liquid crystal panel), and the contrast sensitivity in the X direction (reciprocal of contrast is blurred). The position of the liquid crystal panel is adjusted with the position where the average value of the contrast sensitivity in the Y direction is minimized as the best focus position.
NEC Technical Journal, Vol.55, No.2, pp. 63-68 (2002.2.25)

However, in recent miniaturized projectors, the mounted liquid crystal panel is also miniaturized, the optical path length from the light source to the projection lens is shortened, and the pixel size becomes fine, so the light source light condensing rate Since the aperture ratio of the light modulation element is reduced, the projected image tends to be dark.
As the liquid crystal panel moves, the shape of the projected pixel of the projected image changes, but the variation in the projected pixel due to the miniaturized liquid crystal panel is minute and the projected image becomes darker. It has become difficult to detect a focus image variation by the dependent focus position detection method. Furthermore, the sensitivity of the four color cameras varies, and the projected image has become darker, so that errors in focus adjustment due to variations in camera sensitivity cannot be ignored.

  Thus, if the projected image becomes dark and the light amount of the light source is increased to brighten the image, the temperature rises due to heat generation and the liquid crystal panel is likely to deteriorate due to the increased light amount. In particular, in image quality adjustment, when the image quality adjustment time becomes longer under the direct irradiation condition of the light beam to the panel, the expansion of the member due to the temperature rise. Since the discrepancy between the focus position and the determination position by the focus index becomes large, there is a problem that the image quality after assembly and joining of the light valve is lowered, and the product yield is lowered.

[Object of invention]
The present invention has been made in view of such a problem, and an object of the present invention is to appropriately connect the light source and the illumination irradiating unit with an appropriate light guide and appropriately set the brightness of the image captured by the camera. By doing so, it is possible to compensate for the decrease in the light opening rate due to the miniaturization of the projector, which does not depend on the camera sensitivity variation and the visual sensitivity by the naked eye, and the brightness of the projected image at the time of assembly and image inspection of the light valve The focus positioning device and the focus positioning method of the liquid crystal panel can be provided, which can secure the above, suppress the influence of heat from the lamp light source, and can accurately adjust the optical axis position to the best focus position.

  Furthermore, the purpose of the present invention is to make it possible to clarify the projection pixels even when the brightness is reduced, and to perform automatic focus adjustment even when the visibility of the image variation in the projected video is extremely poor. A focus positioning device and a focus positioning method for a liquid crystal panel that can accurately adjust the optical axis position to the focus position are provided.

  In order to achieve the above object, according to the present invention, in a focus positioning device for a liquid crystal panel that adjusts the focus of the liquid crystal panel by irradiating light transmitted through the liquid crystal panel onto a screen via a dichroic prism, A multi-axis drive mechanism that moves and rotates, a light guide mechanism that divides the color-separated light flux and guides it to the four corners of each liquid crystal panel via optical fibers, and the four corners of the image projected on the screen Four image pickup cameras arranged so as to pick up an image, an A / D conversion circuit for converting an output of RGB color components of a color image obtained from the image pickup camera into a digital value, and an A / D converted color signal A gray-scale image generating unit that generates a gray-scale image using the image, a luminance video processing unit that integrates the luminance of the gray-scale image in the vertical direction (Y direction) and the horizontal direction (X direction), and A focus calculation unit that calculates a focus value serving as a focus index using the luminance integration results in the X direction and the Y direction, a focus search unit that searches for the best focus position, and the above-described multiple units for moving the liquid crystal panel to the best focus position. And a position controller that generates a control signal to be transmitted to the shaft drive mechanism.

In order to achieve the above object, according to the present invention, there is provided a focus positioning method for a liquid crystal panel in which light transmitted through the liquid crystal panel is irradiated onto a screen via a dichroic prism to adjust the focus of the liquid crystal panel. ,
(1) The light emitted from the light source is color-separated and then divided into at least four for each color and guided to at least four corners of the liquid crystal panel through optical fibers, and the light transmitted through the liquid crystal panel is transmitted through the dichroic prism. Projecting onto the screen;
(2) The process of imaging each of the four corners of the image projected on the screen using four imaging cameras;
(3) a process of converting the RGB three-color output obtained from the imaging camera into a digital value;
(4) a process of generating a grayscale image using A / D converted color signals;
(5) integrating the luminance data of the generated grayscale image in the horizontal direction (X-axis direction) and the vertical direction (Y-axis direction);
(6) a process of calculating the average and variance of the luminance integral obtained by the previous process for each of the X-axis direction and the Y-axis direction;
(7) A process of calculating a focus value as a focus index based on the calculation result obtained in the previous process;
(8) The process of obtaining the best focus position;
(9) The process of moving and rotating the liquid crystal panel to the best focus position;
There is provided a focus positioning method for a liquid crystal panel characterized by comprising:

In order to achieve the above object, according to the present invention, there is provided a focus positioning method for a liquid crystal panel in which light transmitted through the liquid crystal panel is irradiated onto a screen via a dichroic prism to adjust the focus of the liquid crystal panel. ,
(1 ') The light emitted from the light source is color-separated and then divided into at least four for each color and guided to at least four corners of the liquid crystal panel through optical fibers, and the light transmitted through the liquid crystal panel is passed through the dichroic prism. Projecting on the screen,
(2 ′) a process of imaging the four corners of the image projected on the screen using four imaging cameras;
(3 ′) a process of converting the RGB three-color output obtained from the imaging camera into a digital value;
(4 ′) a process of generating a grayscale image using the A / D converted color signal;
(5 ′) integrating the luminance data of the generated grayscale image in the horizontal direction (X-axis direction) and the vertical direction (Y-axis direction);
(6 ′) a process of obtaining the maximum value and the minimum value of the luminance integral obtained by the previous process for each of the X-axis direction and the Y-axis direction;
(7 ′) a process of calculating a focus value as a focus index from the maximum value and the minimum value of the luminance integral obtained by the previous process;
(8 ') The process of obtaining the best focus position;
(9 ') The process of moving and rotating the liquid crystal panel to the best focus position;
There is provided a focus positioning method for a liquid crystal panel, characterized by having a focus positioning method for a liquid crystal panel.

According to the present invention, instead of directly irradiating the entire panel opening with illumination light, only the panel position of the imaging part necessary for image quality adjustment is spot-irradiated by optical fiber illumination, so thermal expansion during image quality adjustment is performed. It is possible to reduce image quality fluctuations in the inspection area due to displacement and heat, and to greatly reduce misalignment during image quality adjustment and assembly.
Furthermore, the optical fiber illumination reduces the area and amount of light applied to the liquid crystal panel, which is a polarizing element, and suppresses deterioration of liquid crystal molecules due to heat dissipation and light during adjustment / inspection, thereby improving product quality and yield.
In addition, since the light intensity signal for obtaining the focus index is obtained by integrating the light intensity of the captured image in the X direction and the Y direction, the brightness of the projection pixel decreases as the projector becomes smaller, and the visibility is reduced. Even if the brightness deteriorates, the focus adjustment can be automatically performed, and the focus position adjustment with high accuracy can be performed.
In addition, by inserting a polarizing plate and a diffusion sheet immediately after the optical fiber exit, that is, immediately before the liquid crystal panel, it is possible to improve the light collection characteristics of illumination light and irradiate the liquid crystal panel with uniform light without uneven illumination. Even when the size is very small, the brightness of the screen projection image can be secured, the adjustment accuracy during image quality adjustment can be improved, and the pixel position deviation can be reduced.

[Description of configuration]
FIG. 1 is a block diagram showing a configuration of an embodiment of a focus adjusting apparatus according to the present invention, FIG. 2 is a plan view showing a positional relationship of the color CCD camera shown in FIG. 1, and FIG. FIG. 4 is a side view showing a positional relationship of the color CCD camera shown in FIG. 1, FIG. 4 is a view showing an imaging position on the screen by the color CCD camera shown in FIG. 1, and FIG. 5 is an image recognition shown in FIG. FIG. 6 is a block diagram showing the configuration of the processing unit, and FIG. 6 is a diagram showing the positional relationship between the adjustment optical axis of the optical components of the liquid crystal projector moved by the 6-axis stage unit shown in FIG. 1 and the liquid crystal panel for each color. 7 is a block diagram showing the configuration of the adjustment light source output unit 5 shown in FIG. 2, and FIG. 8 shows the configuration of the optical path between the panel holding unit 6 and the adjustment light source output unit 5 shown in FIG. FIG. 9 shows an adjustment light source output unit 5. FIG. 10 and FIG. 11 are cross-sectional views showing the configuration of the adjustment light source unit 21, and FIGS. 10 and 11 show the relationship between the optical unit 1 and the panel holding unit 6 that supplies the light flux from the adjustment light source output unit to the liquid crystal panel and supports the panel. FIG.

As shown in FIG. 1, the focus positioning apparatus of the present embodiment includes color CCD cameras 3a, 3b, 3c, and 3d, an A / D conversion circuit 11, an image input unit 12, an image memory 13, and recognition control. A unit 7 and a 6-axis stage unit 8 are provided. Here, the recognition control unit 7 includes an image recognition processing unit 14 and a position control unit 15. Although not shown in FIG. 1, the A / D conversion circuit 11 is also provided between the color CCD cameras 3b, 3c, and 3d and the image input unit 12, similarly to the color CCD camera 3a. .
As shown in FIGS. 2 and 3, the color CCD cameras 3a, 3b, 3c, and 3d are projected on the screen projection surface of the screen 2 from the optical unit 1 that constitutes the projection unit of the liquid crystal projector that is a projection display device. It is arranged at a position for imaging the four corners of the projected video. The panel holding unit 6 holds a liquid crystal panel attached to the optical unit 1, and the video signal generator 4 is connected to the liquid crystal panel. As will be described later, the light beam from the adjustment light source output unit 5 is introduced into the panel holding unit 6 by a light guide, and the light beam is branched by an optical branching device immediately before the panel holding unit 6, and then corresponds to the inspection region of the liquid crystal panel Irradiate the panel position, corresponding to the single color raster scan video provided from the video signal generator 4, pass through the liquid crystal panel corresponding to the corresponding color, and project the single color projection video on the screen 2.
Further, in order to shield light other than the projected image from the optical unit 1, all the light from the outside is blocked by the dark curtain 45.
As shown in FIG. 4, white material panels 2a, 2b, 2c, and 2d are attached to the four corners of the screen 2. The color CCD cameras 3a, 3b, 3c, and 3d are respectively installed at positions where the four corners of the projected images on the white material panels 2a, 2b, 2c, and 2d are sufficiently accommodated, and capture the projected images of the projected areas. In FIG. 4, the imaging areas of the color CCD cameras 3a, 3b, 3c, and 3d are denoted by 3a ′, 3b ′, 3c ′, and 3d ′, respectively.

The A / D conversion circuit 11 performs A / D conversion on the color images captured by the color CCD cameras 3a, 3b, 3c, and 3d, respectively. A / D conversion is performed for each of the red (R), green (G), and blue (B) colors that are color components of the color image.
In the image input unit 12, the color images captured by the color CCD cameras 3a, 3b, 3c, and 3d installed at the four corners of the projected video and A / D converted are integrated, and image data for each color component is obtained. Generated.
The image memory 13 stores R, G, and B color image data generated by the image input unit 12 for each color component. The image data stored in the image memory 13 is transferred to the image recognition processing unit 14 of the recognition control unit 7.

As shown in FIG. 5, the image recognition processing unit 14 includes a grayscale image generation unit 16 that generates a pseudo monochrome image from R, G, and B image data, a focus inspection area generation unit 17, a luminance projection processing unit 18, and a focus calculation unit. 19 and a focus search unit 20.
The gray image generation unit 16 generates a single color gray image close to the light intensity on the projection surface using the luminance value of the image data of each color component stored for each color component in the image memory 13.
The focus inspection area generation unit 17 sets a focus inspection area in the image area at the camera visual field position corresponding to the four imaging positions on the screen 2.
The luminance projection processing unit 18 performs luminance integration for each of the X and Y directions in the focus inspection area set by the focus inspection area generation unit 17, and the light intensity distribution on the projection surface of the projection pixel area for each X and Y direction. Emphasize the clarification of feature variation.
The focus calculation unit 19 calculates a focus value for specifying the focus position based on the luminance integration for each of the X and Y directions obtained by the projection processing unit 18. A method for calculating the focus value will be described later.
The face search unit 20 determines a panel position where the focus value F is maximum for each focus inspection area, based on the focus value F for each focus inspection area at each position where the panel is moved stepwise within the panel movement range. It is determined as the focus position where the projected image is the clearest.

The position control unit 15 calculates correction angle signals Δθx and Δθy for correcting the focus centroid and the panel posture from the focus position for each focus inspection area obtained by the focus search unit 20, and calculates the calculated focus centroid and correction angle signal. Is sent to the 6-axis stage unit 8 as a command value.
The 6-axis stage unit 8 is a mechanism for adjusting the mounting position of the optical component of the optical unit 1 based on the command value from the position control unit 15, and the liquid crystal panels 9a, 9b, 9c shown in FIG. The panel position is adjusted when it is attached to the dichroic prism 10 that performs color synthesis of light from 9b and 9c.

In FIG. 6, X, Y, Z, θ, θ _X , and θ _Y indicate the respective adjustment optical axes of the liquid crystal panel 9a (in charge of G color) that is moved by the six-axis stage unit 8, and the liquid crystal panel 9a The incident light direction (normal direction) perpendicular to the plane is defined as the Z axis, the incident light direction perpendicular to the liquid crystal panels 9b and 9c is defined as the X axis, and the directions perpendicular to the Z axis direction and the X axis direction are defined as the Y axis. It has established. The liquid crystal panel 9a is panel position X, Y, Z and the rotation angle theta about the Z-axis, a panel tilt angle theta _X around the X axis, the position in six axes of the Y-axis of the panel tilt angle theta _Y As determined, the focus adjustment is performed on three adjustment optical axes around the Z axis, the X axis, and the Y axis. The liquid crystal panel 9b responsible for the R color and the liquid crystal panel 9c responsible for the B color have the same optical axis coordinate arrangement.
In the configuration shown in FIGS. 2 and 3, the image projected from the optical unit 1 is directly received by the screen 2. However, a mirror is disposed in front of the optical unit 1 so that the reflected light is received by the screen 2. May be. In this way, it is possible to increase the distance (projection distance) between the optical unit 1 and the screen 2 while avoiding an increase in the size of the apparatus.

(1) Structure of Adjustment Light Source Next, the configuration of the adjustment light source will be described with reference to FIGS. As shown in FIG. 7, the adjustment light source output unit 5 includes an adjustment light source 21, light guides 22R, 22G, and 22B made of optical fibers, and fiber branching portions 23R, 23G, and 23B. As shown in FIG. 8, the light branched into five at the fiber branching portion 23R (23G, 23B) is guided to the fiber emitting portion 25 inserted into the panel holding portion 6 by the light guide 24 made of an optical fiber. Injected from the fiber emitting unit 25. Further, as shown in FIG. 9, the adjustment light source 21 is configured in a color separation optical system that is substantially the same as the light source unit of the projector, and includes a light source lamp 26, an optical integrator 27, a polarization conversion optical system 28, and a field lens 29. , Total reflection mirrors 30, 33, two dichroic mirrors 31a, 31b, relay lens 32, three condenser lenses 34R, 34G, 34B, and three fiber light incident portions 35R, 35G, 35B.

The luminous flux emitted from the light source lamp 26 is aligned in the emission direction by the optical integrator 27, adjusted to a predetermined polarization component by the polarization conversion optical system 28, and the emission direction is bent by 90 ° by the total reflection mirror 30 a, The red light beam forms an image near the light guide 35R. The red light beam emitted from the relay lens 32 is incident so that the central axis thereof is perpendicular to the incident surface of the subsequent condenser lens 34R, and the red light beam emitted from the condenser lens 34R further enters the light guide 22R. The light is focused on the fiber light incident part 35R constituting the input part. Similarly, the light beams of green (G) and blue (B) are condensed on 35G and 35B.
The color separation optical system includes two dichroic mirrors 31a and 31b and a reflection mirror 33, and a plurality of partial light beams emitted from the integrator 27 by the dichroic mirrors 31a and 31b and the total reflection mirror 33 are red, It has a function of separating light into three colors of green and blue.

  The optical components constituting the integrator, the polarization conversion optical system, the color separation optical system, and the relay lens of the adjustment light source 21 are accommodated in the optical component casing. The color-separated light fluxes shown in FIG. 8 are branched into five light fluxes from the fiber light incident portions 35R, 35G, and 35B by the light guides and immediately before the liquid crystal panel holding portion 6 by the light splitters 23R 23G and 23B. As shown in FIGS. 10 and 11, the light beam that has been split is input into the fiber emitting section 25 and passes through the two condensing lenses 37a and 37b so as to have an appropriate light diameter in a range that covers the inspection region. To the total reflection mirror 38. These light beams of R, G, and B are reflected by a total reflection mirror 38 attached at an angle of 45 ° with respect to the traveling direction of the light beam of the condenser lens, and are bent by 90 °, so that a diffusion sheet 39, a polarizing plate 40a, The optical unit 1 is irradiated through the five optical path holes 44, the liquid crystal panel 41, and the polarizing plate 40b of the liquid crystal panel holding unit 6 shown in FIG.

  On the other hand, the optical unit 1 shown in FIG. 10 is composed of a cross dichroic prism 42 and a projection lens 43 serving as an opto-color synthesis optical system, and the cross dichroic prism 42 is fixed to the front stage of the optical path of the projection lens 43 and from the light guide. The emitted light beam passes through the cross dichroic prism 42 and is then projected onto the screen 2 from the projection lens 43 serving as a projection optical system.

  FIGS. 13A and 13B are diagrams showing the diffusion sheet on the front surface of the liquid crystal panel when the actual panel is irradiated with the light beam of the adjustment light source output unit shown in FIG. FIG. 13C and FIG. 13D are actual images when green (G) color without diffusion sheet is projected onto the screen. From the light quantity distribution shown in FIG. 13B, it can be seen that a light beam having a symmetrical light quantity distribution is secured on the liquid crystal panel surface by the combination of the condensing lens at the fiber exit and the effect of the diffusion sheet. Furthermore, from the image shown in FIG. 13 (d), in the actual projection image by the optical unit 1 adopting this illumination method, a uniform image can be secured at the irradiation position on the liquid crystal panel, and the brightness on the screen surface is sufficiently secured. You can see that it is made.

(2) Focus Search Operation Next, the operation of the present embodiment will be described in detail with reference to FIG. FIG. 14 is a flowchart showing the operation of the focus positioning apparatus according to the present invention. In this embodiment, the focus search is performed through the stages of coarse adjustment, fine adjustment, and ultrafine adjustment, but the focus search at any stage is performed in the same process (the operation in step A10 is different). The following description should be understood as a common processing operation in each adjustment stage unless otherwise specified.
The movement range of the liquid crystal panel is determined in advance so as to include the best focus position, and inspection is performed while moving the liquid crystal panel step by step (the movement range of the liquid crystal panel and the movement width of one step are adjusted as the adjustment stage proceeds). Gradually narrowed). For example, the inspection is performed while starting from the position farthest from the dichroic prism and making it approach the dichroic prism step by step. First, the video signal generator 4 provides a monochromatic raster scan video to the liquid crystal projector 1 (step A1), and the liquid crystal projector uses the monochromatic raster scan video provided to the liquid crystal panels 9a, 9b, 9c corresponding to the corresponding color. Either one is passed and projected onto the screen 2 as a monochromatic projection image (step A2). The monochromatic raster scan video is an image for performing focus adjustment. For the focus adjustment of the liquid crystal panel 9a in charge of G color, the monochromatic raster scan video of G color is used for focus adjustment of the liquid crystal panel 9b in charge of R color. The R single-color raster scan video is used for the focus adjustment of the liquid crystal panel 9c responsible for the B color, and the B single-color raster scan video is used. In the present embodiment, a solid pattern (full screen equal display) is used during coarse adjustment and fine adjustment, and an L-shaped pattern is irradiated during super fine adjustment. Hereinafter, an example of performing the focus adjustment of the liquid crystal panel 9a in charge of G color will be described.

  Next, the four corners of the G-color projection image projected on the screen 2 by the color CCD cameras 3a, 3b, 3c, and 3d are respectively picked up as color images (step A3) and picked up by the A / D conversion circuit 11 respectively. A / D conversion is performed for each color component of the color image (step A4), and the four color images A / D converted by the image input unit 12 are integrated and stored in the image memory 13 together with the coordinates for each color component. (Step A5). The screen 2 is projected with the G color projection image that has passed through the liquid crystal panel 9a in charge of the G color. However, since the R color and B color components are actually included, the color CCD camera 3a, Images are taken as color images by 3b, 3c, and 3d.

  FIG. 15 is a diagram illustrating an example of image data generated by the image input unit illustrated in FIG. 1. The image data generated by the image input unit 12 is a four-frame color image captured by the color CCD cameras 3a, 3b, 3c, and 3d and A / D-converted. As shown in FIG. Each area of the imaging areas 3a ′, 3b ′, 3c ′, and 3d ′ is an area corresponding to an opening portion of the projection pixel and a black matrix that becomes a break between the projection pixels. For example, a color CCD camera 3c having 640 × 480 pixels captures an effective projection area on the screen by 1/4 of the imaging area, and an L-shaped pattern formed by raster scanning is projected onto the area. Yes (during ultra fine adjustment). The luminance distribution at the pixel position (x, y) in one frame of the image data is R (x, y), G (x, y), B (x, y) for each color component in the image memory 13. (Hereinafter described as R, G, and B, respectively).

Next, a pseudo monochrome image is generated by the grayscale image generation unit 16 (step A6). The grayscale image generation unit 16 sequentially reads out the image data of each imaging area stored in the image memory 13 from the image memory 13, and appropriately weights the luminance distributions R, G, and B of each color component of the image data to obtain a single color. To generate a grayscale image. As the weighting of the luminance distributions R, G, and B when generating a single color grayscale image, for example, the luminance value I (x of the single color grayscale image at the pixel position (x, y) in one frame in the color image data is used. , Y)
I (x, y) = (m1 * R + m2 * G + m3 * B) / m4
As a result, a monochrome gray image close to a monochrome image is generated. Here, for example, the weighting coefficients are m1 = 28, m2 = 77, m3 = 151, and m4 = 256.

Next, a focus inspection area is set by the focus inspection area generation unit 17 (step A7). FIG. 15 is a diagram showing the positional relationship of the focus inspection areas generated by the focus inspection area generation unit shown in FIG.
As shown in FIG. 15, the focus inspection area generation unit 17 sets, for example, a focus inspection area of 13 × 11 pixels in each captured image data. The focus inspection area is set so as to correspond to the imaging areas 3a ′, 3b ′, 3c ′, and 3d ′ of the color CCD camera that images the four corners of the screen. Since the distribution of the projection pixels in the grayscale image is almost constant at any position in the camera field of view, the size of the focus inspection area is within the range of about 10 × 10 pixels as shown in FIG. It is set. This is because the number of pixels necessary for calculation for focus adjustment is minimized to reduce the number of calculations, thereby realizing high speed.

Next, the luminance projection processing unit 18 performs luminance integration for each direction in the X direction and the Y direction, which are the light distribution features in the focus inspection area (step A8).
The luminance projection processing unit 18 performs luminance integration for each direction in the X direction and the Y direction of the focus inspection area set by the focus inspection area generation unit 17. By performing luminance integration, it is possible to clearly grasp the characteristics of the light quantity distribution.
Next, the average value and the variance value of the luminance integrated values in the X and Y directions obtained by the luminance projection processing unit 18 are calculated by the focus calculation unit 19 (step A9) (in the case of ultra fine adjustment). Alternatively, the maximum value (Imax) _X , (Imax) _Y and the minimum value (Imin) _X , (Imin) _Y of the luminance integrated values in the X and Y directions obtained by the luminance projection processing unit 18 are obtained by the focus calculation unit 19. (Step A9) (in the case of coarse adjustment or fine adjustment).

Further, the focus calculation unit 19 calculates the focus value at the panel position by a calculation formula that can evaluate the degree of focusing using the average value, variance value, maximum value, minimum value, etc. of the luminance integrated values in the X and Y directions. (Step A10). This calculation formula can be appropriately determined by those skilled in the art. Therefore, in the present embodiment, the calculation formulas differ between the focus value at the time of coarse adjustment and fine adjustment and the focus value at the time of fine adjustment. In the case of coarse adjustment and fine adjustment in which a solid inspection pattern is projected, the focus value is calculated by, for example, specific visibility (Imax-Imin) / (Imax + Imin) corresponding to MTF (Modulation Transfer Function). Here, Imax and Imin are Imax = {(Imax) _X + (Imax) _Y } / 2 and Imin = {(Imin) _X + (Imin) _X } / 2. That is, the focus value F (z) can also be calculated as follows.
F _X (z) = {(Imax) _X- (Imin) _X } / {(Imax) _X + (Imin) _X }
F _Y (z) = {(Imax) _Y- (Imin) _Y } / {(Imax) _Y + (Imin) _Y }
F (z) = {F _X (z) + F _Y (z)} / 2
On the other hand, in the case of ultra fine adjustment, the focus value F (z) is calculated by 1 − [{σ _x (z)} ÷ {σ _y (z)}], for example. Here, σ _x (z) and σ _y (z) are variance values of luminance integration. The focus value is a characteristic value that takes a value between 0 and 1, and when calculating with (Imax-Imin) / (Imax + Imin), the focus value becomes smaller as the focus position is closer to 1-[{ In the case of σ _x (z)} ÷ {σ _y (z)}], on the contrary, the closer to the best focus position, the larger the value. The focus value is calculated for each imaging region 3a ′, 3b ′, 3c ′, 3d ′. Then, the focus calculation unit 19 stores the focus value together with the panel position (Z position).

  Next, it is checked whether or not the predetermined range of step movement of the liquid crystal panel in the Z-axis direction is completed (step A11). If not, the liquid crystal panel is moved one step (step A12). After that, the process returns to step A3. If it is determined in step A11 that the movement of the liquid crystal panel has been completed, in step A10, the focus value F (z) at which the image is the clearest takes an extreme value (the focus value is A focus position (maximum value or minimum value) is obtained for each focus inspection area (step A13).

That is, the focus search unit 20 obtains the Z-axis position where the focus value F (z) calculated for each focus inspection area is maximized or minimized as the focus position. The focus positions for each focus inspection area (upper left, upper right, lower left, lower right) are obtained as Za, Zb, Zc, and Zd, respectively. Za, Zb, Zc, Zd are
Za = MAX {F (z)} orMIN {F (z)}
Zb = MAX {F (z)} orMIN {F (z)}
Zc = MAX {F (z)} orMIN {F (z)}
Zd = MAX {F (z)} orMIN {F (z)}
Can be expressed as

Next, when the focus value F (z) is calculated as 1 − [{σ _x (z)} ÷ {σ _y (z)}], the Z-axis position where the focus value F (z) becomes the maximum value is The reason for the focus position will be described.
FIG. 16 shows the brightness in the X and Y directions integrated by the brightness projection processing unit shown in FIG. 5 when the panel is moved by ± 50 μm in the Z-axis direction with the best focus position in between. FIG. 17 is a diagram showing a change in the integral value. FIG. 17 shows the variance calculated from the luminance integral values in the X and Y directions integrated by the projection processing unit shown in FIG. FIG. 18 is a conceptual diagram showing the relationship with the Z-axis position, and FIG. 18 is a diagram showing the relationship between the focus value calculated by the focus calculation unit shown in FIG. 5 and the Z-axis position. Further, FIG. 19 shows a dispersion value of the luminance integrated value integrated by the luminance projection processing unit 18 shown in FIG. 5 when a single color G is projected and the panel is moved at intervals of 3 μm in the Z-axis direction. It is a figure which shows the relationship between a focus parameter | index and Z-axis position.
FIG. 16 shows an image and an integrated luminance value at −50 μm position, best focus position, and +50 μm position from the top. It can be seen from the figure that the integrated luminance value is minimum in both the X and Y directions at the best focus position. Further, as shown in the figure, the luminance integrated value in the X direction is larger at the −50 μm position than at the +50 μm position. On the other hand, the luminance integrated value in the Y direction is smaller at the −50 μm position than at the +50 μm position.

As described above, when the liquid crystal panel 9c is moved in the Z-axis direction, the X direction and the Y direction have opposite focus characteristics in the vicinity of the best focus. That is, as shown in FIG. 17, when the liquid crystal panel 9c is sequentially moved along the Z axis from the near side (− direction) to the dichroic prism 10 direction (+ direction) across the focus position, the dispersion value of y Decreases, while the variance of x tends to increase.
That is, when the liquid crystal panel 9c is sequentially moved along the Z axis from the near side (− direction) across the focus position to the dichroic prism 10 direction (+ direction), the amount of change in the amount of light of the projected image pattern is X There is a conflict between the direction and the Y direction. This property reflects the fact that the light entering the projection lens has a condensing characteristic, that is, a tangent value of the lens is different between the lens center and the peripheral part, so that the X and Y condensing characteristics are not symmetric at the best focus position.
Accordingly, as shown in FIG. 17, the change in the focus value when the liquid crystal panel 9c is sequentially moved along the Z axis from the front (− direction) to the dichroic prism 10 direction (+ direction) across the focus position, as shown in FIG. For example, when the focus value F (z) is given by the above-described calculation formula, the focus value F (z) is maximum at the best focus position where the projected image is sharpest as shown by the curve in FIG. Value.

On the other hand, when the focus value F (z) is coarse adjustment and fine adjustment given by F (z) = (Imax−Imin) / (Imax + Imin), the transition of the focus value is as shown in FIG. . Further, in the case of ultra fine adjustment, the transition of the focus value when the focus value is redefined as σ _x (z)} ÷ σ _y (z) is as shown in FIG. When coarse adjustment in FIG. 20 is performed, the panel is moved at a pitch of 5 μm to specify an approximate best focus position, and when the fine adjustment of FIG. 21 using the result is performed, the panel is moved at a pitch of 1 μm. In the ultra-fine adjustment mode with high resolution, it captures small focus fluctuations that are easy to overlook and detects the true best focus position.

Next, the focus search unit 20 obtains the focus position of the panel from the focus value calculated for each focus inspection area by the focus calculation unit 19.
Since the liquid crystal panel 9a has rotation, tilt, and tilt angles in the X and Y directions with respect to the optical axis direction of the Z axis, and there is a difference in the optical path length to the projection surface, each focus inspection area (upper left, upper right, The focus positions Za, Zb, Zc, and Zd obtained from the color images obtained by imaging the lower left and lower right) with the color CCD cameras 3a, 3b, 3c, and 3d, respectively, do not match. Accordingly, if the true focus surface position through which the center of the liquid crystal panel 9a passes is found from the focus positions Za, Zb, Zc, and Zd, the final focus position of the liquid crystal panel can be searched.

For example, the true focus position Z of the optical axis (Z axis) perpendicular to the screen 2 of the liquid crystal panel 9a is calculated from the focus centroid calculated from the focus position in each focus inspection area from the symmetry with respect to the optical axis center of the liquid crystal panel. Then
Z = (n1 × Za + n2 × Zb + n3 × Zc + n4 × Zd) / Σni
For example, weighting for each optical axis direction
n1 = n2 = n3 = n4 = 1
As an alternative, the focus center of gravity Z at the optimum focus position at each imaging position may be used as the focus surface of the liquid crystal panel.

Next, the position controller 15 generates a command value for the 6-axis stage 8 based on the focus position of each focus inspection area (step A14).
The focus search unit 20 calculates the adjustment correction amounts θx and θy in the rotation directions around the X axis and the Y axis when the true focus position Z is determined.
Δθx = (±) arcsin [{(Z _A + Z _B )-(Z _C + Z _D )} / 2] / L _v
Δθy = (±) arcsin [{(Z _A + Z _C )-(Z _B + Z _D )} / 2] / L _H
(L _v and L _H are the vertical and horizontal lengths of the liquid crystal panel), and the adjustment correction amounts Δθx and Δθy together with the true focus position Z are transmitted to the position control unit 15 as command values, The position control unit 15 adjusts the optical axis of the liquid crystal panel 9 a by the 6-axis stage unit 8 based on the command value from the focus search unit 20. Regarding the signs of Δθx and Δθy, after adjusting each sign, the flow of steps A1 to A10 is performed to calculate the focus value in each case, and in the case of coarse adjustment and fine adjustment, the focus value The code that minimizes is adopted as the best focus. If the approximate best focus position can be detected by the coarse adjustment, then the focus search range and the single movement step width of the liquid crystal panel are narrowed and fine adjustment is performed by the same method as the coarse adjustment. Subsequently, when the approximate best focus position obtained by fine adjustment can be detected, the fine search is performed by further narrowing the focus search range and the single movement step width of the liquid crystal panel. Any one or each of coarse adjustment, fine adjustment, and super fine adjustment may be performed a plurality of times. The ultrafine adjustment is performed, and if there is no problem in alignment, the liquid crystal panel 9a is fixed to the dichroic prism 10 by UV bonding or the like. This focus adjustment is performed for the three liquid crystal panels R, G, and B.

Here, the determination of the signs of the adjustment correction amounts θx and θy in the rotation direction around the X axis and the Y axis will be described. In FIG. 22, the angle correction amount in the θx and θy directions from the best focus position in the Z-axis direction in the four imaging regions is shifted to the (+) and (−) sides to correct the position correction with the same angle complement. It shows the transition of the focus value in the imaging areas at the four positions on the screen. When the pixel pitch of the liquid crystal panel is miniaturized, the color from the light source incident on the panel, or the variation of the parts of the optical system that constitutes the projection lens and its projector, the liquid crystal panel is emitted from the fiber illumination and the light beam It may be attached not perpendicular to the axial direction. For this reason, it is necessary to correct the panel angle. Although the absolute values of the correction angles θx and θy can be calculated, it is difficult to visually determine the correction direction. This is because the angle correction is apparently a depth and a tilt direction, and it is extremely difficult to visually determine a change in the focus image on a panel having a very small pixel pitch. In FIG. 22, when θx and θy are shaken in the (−) direction, the focus values in the imaging range at the four corners of the screen are all small. Therefore, the angle correction of the panel position is performed in the (−) direction by the automatic code determination.
FIG. 23 is a combination of four actual images when G color projection is performed after completion of automatic focus adjustment when the angle correction amounts of θx and θy are corrected by the sign on the (−) side. FIG. 24 is an enlarged view of a projected pixel near the lower right corner of the captured image in FIG. 23. Further, FIG. 25 is a combination of four actual images in G color projection after completion of automatic focus adjustment when the angle correction amounts of θx and θy are corrected by the sign on the (+) side. FIG. 26 is an enlarged view of a projection pixel near the lower right corner of the captured image in FIG. 25. Referring to FIG. 24, it can be seen that when the angle correction is performed on the (−) side, the occurrence of flare as shown in FIG. 26 is not observed, and the panel is guided to the best focus position.

The focus adjustment has been described above. Before this focus adjustment, the convergence adjustment is roughly adjusted using image recognition technology such as pattern matching so that the image for focus adjustment enters the camera imaging range to some extent. Desirably, a pattern for focus adjustment is partially imaged in the imaging range during automatic adjustment or when the liquid crystal panel is attached. Further, since color misregistration may occur as a result of focus adjustment, in such a case, it is desirable to perform convergence adjustment by fine adjustment after the focus adjustment is completed. Furthermore, since the focus position may be shifted due to the convergence adjustment, it is desirable to perform the focus adjustment again in that case. The UV bonding described above is performed after the focus adjustment is finally finished.
In the present embodiment, the position adjustment of the liquid crystal panel of the optical system of the projection display device has been described. However, the DLP (digital light processing) type in which the liquid crystal panel is replaced with an optical device using a DMD (digital mirror device). It is also effective for adjusting the projection image by adjusting the position of the DMD in the projector.
Furthermore, the focus index used in this embodiment can also be applied to autofocus adjustment using a projection lens of a projection image of a projector product equipped with a distance sensor and a micro camera module.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for implementing the present invention. In each figure, the same numerals are given to the same component.

1 is a block diagram showing the configuration of an embodiment of a focus positioning device according to the present invention. FIG. 2 is a plan view showing the positional relationship of the color CCD camera shown in FIG. 1. The side view which shows the positional relationship of the color CCD camera shown in FIG. The figure which shows the imaging position on the screen by the color CCD camera shown in FIG. The block diagram which shows the structure of the image recognition process part shown in FIG. FIG. 2 is a diagram showing a positional relationship between an adjustment optical axis of an optical component of a liquid crystal projector moved by a six-axis stage unit shown in FIG. 1 and a liquid crystal panel for each color. The figure which shows the structure of the light source output part for adjustment of the focus positioning apparatus which concerns on this invention. The figure which shows the structure from the fiber branch part of the illumination light optical path of the focus positioning apparatus which concerns on this invention to fiber injection | emission. The figure which shows the structure of the light source for adjustment of the focus positioning apparatus which concerns on this invention. The figure which shows the structure of the structure of an optical unit and the fiber emission part in a panel holding part in the focus positioning apparatus which concerns on this invention. The figure which shows the assembly structure of the optical unit and liquid crystal panel holding | maintenance part of the focus positioning apparatus which concerns on this invention. The figure which shows the light beam emission hole of the panel holding part of the focus positioning apparatus which concerns on this invention. The figure which shows the light quantity distribution and projection image | video of the fiber injection | emission part in a liquid crystal panel surface at the time of using the illumination method of this invention and making a comparison without a diffusion sheet. 5 is a flowchart showing the operation of the embodiment of the focus adjustment apparatus according to the present invention. The figure which shows the example of image data produced | generated by the image input part shown in FIG. FIG. 6 is a diagram illustrating a distribution of luminance integration values and a displacement of projection pixels when the luminance integration by the projection processing unit shown in FIG. 5 is shifted by ± 50 μm from the focus center. FIG. 6 is a diagram showing the relationship between the transition of the variance of the luminance integration value obtained by the luminance integration by the projection processing unit shown in FIG. 5 and the panel position. The figure which shows the relationship between the focus value calculated by the focus calculating part shown in FIG. 5, and the panel position on a Z-axis. When a single color R pattern is projected onto the screen, the focus index obtained from the variance of the luminance integrated values in the X and Y directions integrated by the luminance projection processing unit shown in FIG. 5 and the panel on the Z axis The figure which shows the relationship with a position. FIG. 6 is a diagram showing a relationship between a transition of a focus value calculated from a luminance integration value obtained by luminance integration by a projection processing unit shown in FIG. 5 and a panel position. (Coarse adjustment) The figure which shows the relationship between transition of the redefined focus value calculated from the brightness | luminance integral value obtained by the brightness | luminance integration by the projection process part shown in FIG. 5, and a panel position. (During ultra fine adjustment) FIG. 9 is a comparative diagram showing changes in focus values in the imaging areas at the four corners of the screen when the angle correction amounts in the θx and θy directions are corrected with the same amount of correction on the (+) side and the (−) side, respectively. The real image figure which combined the four images in G color projection when the angle correction amount of the θx and θy directions is corrected to the (−) side. The projection pixel enlarged view of the lower right corner vicinity of FIG. The real image figure which combined the four images in G color projection when the angle correction amount of the θx and θy directions is corrected to the (+) side. The projection pixel enlarged view of the lower right corner vicinity of FIG.

Explanation of symbols

1 optical unit, 2 screen, 2a, 2b, 2c, 2d white material panel, 3a, 3b, 3c, 3d color CCD camera, 3a ', 3b', 3c ', 3d' imaging area, 4 video signal generator, 5 Light source output unit for adjustment, 6 panel holding unit, 7 recognition control unit, 8 6-axis stage unit, 9a, 9b, 9c liquid crystal panel, 10 dichroic prism, 11 A / D conversion circuit, 12 image input unit, 13 image memory, 14 image recognition processing unit, 15 position control unit, 16 grayscale image generation unit, 17 focus inspection area generation unit, 18 luminance projection processing unit, 19 focus calculation unit, 20 focus search unit, 21 light source unit, 22R, 22G, 22B light guide, 23R, 23G, 23B Fiber branch, 24 branch light guide, 25 B emission unit, 26 light source lamp, 27 light integrator, 28 polarization conversion optical system, 29 field lens, 30 total reflection mirror, 31a, 31b dichroic mirror, 32 relay lens, 33 total reflection mirror, 34R, 34G, 34B condenser lens, 35R, 35G, 35B fiber light incident part, 37a, 37b condensing lens, 38 total reflection mirror, 39 diffusion sheet, 40a, 40b deflection plate, 41 liquid crystal panel, 42 dichroic prism, 43 projection lens, 44 optical path hole, 45 dark curtain

Claims (14)

In a liquid crystal panel focus positioning device that adjusts the focus of a liquid crystal panel by irradiating light transmitted through the liquid crystal panel onto a screen via a dichroic prism, and a color-separated multi-axis drive mechanism that moves and rotates the liquid crystal panel A light guide mechanism that divides the luminous flux and guides it to the four corners of each liquid crystal panel through an optical fiber, and four imaging cameras arranged to capture the four corners of the image projected on the screen, An A / D conversion circuit that converts an output of RGB color components of a color image obtained from the imaging camera into a digital value; a gray image generation unit that generates a gray image using the A / D converted color signal; Using a luminance image processing unit that integrates the luminance of a grayscale image in the vertical direction (Y direction) and the horizontal direction (X direction), and the luminance integration results in the X direction and the Y direction A focus calculation unit that calculates a focus value serving as a focus index, a focus search unit that searches for a best focus position, and a control signal that is transmitted to the multi-axis drive mechanism unit to move the liquid crystal panel to the best focus position A focus positioning device for a liquid crystal panel. The light guide unit includes an optical branching unit, a fiber emitting unit, an optical fiber connecting the light source unit and the optical branching unit, and an optical fiber connecting the optical branching unit and the fiber emitting unit. The focus positioning device for a liquid crystal panel according to claim 1. 3. The focus positioning device for a liquid crystal panel according to claim 1, wherein a light diffusion member is inserted between the light guide portion and the liquid crystal panel. 4. The liquid crystal panel according to claim 1, wherein the liquid crystal panel is held by a panel holding portion driven by the multi-axis driving mechanism together with a terminal portion of the light guide portion. Focus positioning device. The outputs of the A / D conversion circuits that convert the outputs of the four imaging cameras are integrated by an image input unit and then stored in an image memory, and the grayscale image generation unit includes data stored in the image memory. 5. The focus positioning device for a liquid crystal panel according to claim 1, wherein a grayscale image is generated on the basis of the above. 6. The focus positioning device for a liquid crystal panel according to claim 1, wherein a mirror that reflects a projected image is provided between the dichroic prism and the screen. A liquid crystal panel focus positioning method for adjusting the focus of a liquid crystal panel by irradiating light transmitted through the liquid crystal panel onto a screen via a dichroic prism,
(1) The light emitted from the light source is color-separated and then divided into at least four for each color and guided to at least four corners of the liquid crystal panel through optical fibers, and the light transmitted through the liquid crystal panel is transmitted through the dichroic prism. Projecting onto the screen;
(2) The process of imaging each of the four corners of the image projected on the screen using four imaging cameras;
(3) a process of converting the RGB three-color output obtained from the imaging camera into a digital value;
(4) a process of generating a grayscale image using A / D converted color signals;
(5) integrating the luminance data of the generated grayscale image in the horizontal direction (X-axis direction) and the vertical direction (Y-axis direction);
(6) a process of calculating the average and variance of the luminance integral obtained by the previous process for each of the X-axis direction and the Y-axis direction;
(7) A process of calculating a focus value as a focus index based on the calculation result obtained in the previous process;
(8) The process of obtaining the best focus position;
(9) The process of moving and rotating the liquid crystal panel to the best focus position;
A focus positioning method for a liquid crystal panel, comprising: A liquid crystal panel focus positioning method for adjusting the focus of a liquid crystal panel by irradiating light transmitted through the liquid crystal panel onto a screen via a dichroic prism,
(1 ') The light emitted from the light source is color-separated and then divided into at least four for each color and guided to at least four corners of the liquid crystal panel through optical fibers, and the light transmitted through the liquid crystal panel is passed through the dichroic prism. Projecting on the screen,
(2 ′) a process of imaging the four corners of the image projected on the screen using four imaging cameras;
(3 ′) a process of converting the RGB three-color output obtained from the imaging camera into a digital value;
(4 ′) a process of generating a grayscale image using the A / D converted color signal;
(5 ′) integrating the luminance data of the generated grayscale image in the horizontal direction (X-axis direction) and the vertical direction (Y-axis direction);
(6 ′) a process of obtaining the maximum value and the minimum value of the luminance integral obtained by the previous process for each of the X-axis direction and the Y-axis direction;
(7 ′) a process of calculating a focus value as a focus index from the maximum value and the minimum value of the luminance integral obtained by the previous process;
(8 ') The process of obtaining the best focus position;
(9 ') The process of moving and rotating the liquid crystal panel to the best focus position;
A focus positioning method for a liquid crystal panel, comprising: 9. The following (a) and (b) are repeated after the end of the seventh (7) or (7 ′) process until the liquid crystal panel finishes moving within a preset range. 4. A method for positioning a focus of a liquid crystal panel.
(A) The liquid crystal panel is moved by a predetermined distance in a normal direction standing on the surface of the liquid crystal panel.
(B) Steps (2) to (7) or steps (2 ') to (7') are executed. After completion of the ninth (9) or (9 ') step, the set range is reduced within the range including the best focus position, and the focus position is adjusted again by reducing the predetermined distance. 10. The focus positioning method for a liquid crystal panel according to claim 9, The liquid crystal according to any one of claims 7 to 10, wherein in the process (4) or (4 '), the brightness I (x, y) of each point is calculated based on the following equation. Panel focus positioning method.
I (x, y) = {m1 * R (x, y) + m2 * G (x, y) + m3 * B (x, y)} / (m1 + m2 + m3)
However, m1, m2, and m3 are constants, and R (x, y), G (x, y), and B (x, y) are intensity signals of respective colors at coordinates (x, y). In the process of the (9) or the (9 '), from the four corners of the focus position of the liquid crystal panel, based on the following equation, and the rotation [Delta] [theta] _X around the X-axis, angular rotation of the rotation [Delta] [theta] _Y around the Y axis 12. The focus positioning method for a liquid crystal panel according to claim 7, wherein the panel orientation is corrected to determine the sign of the correction direction based on the focus value after the orientation correction.
Δθ _X = (±) arcsin [{(Z _A + Z _B )-(Z _C + Z _D )} / 2] / L _v
Δθ _Y = (±) arcsin [{(Z _A + Z _C )-(Z _B + Z _D )} / 2] / L _H
However, Z _A , Z _B , Z _C , and Z _D are the focus positions during coarse or fine adjustment of each imaging area, and L _v and L _H are the vertical and horizontal lengths of the liquid crystal panel. For each code, after correcting the panel orientation, the focus value is obtained by performing the steps (1) to (7) or the steps (1 ′) to (7 ′). The focus positioning method for a liquid crystal panel according to claim 12. Prior to executing the processes from (1) to (9) or after executing the processes from (1) to (9), the liquid crystal panels for each color are aligned (convergence adjustment). 13. The focus positioning method for a liquid crystal panel according to any one of claims 7 to 12, wherein:

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