JP2009058662A - Image display system and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance contrast to avoid black floating. <P>SOLUTION: An image display system 10 has a projector 100 and a screen 200. The screen 200 is configured to vary the reflectivity of its projection screen in units of blocks. When light from a liquid-crystal panel 140 of the projector 100 is projected onto the projection screen, the reflectivity of blocks on the projections screen of the projector 100 that correspond to a portion where the light is projected is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display system and an image display method for displaying an image on a screen.

  Conventionally, there is an image display system that displays an image on a screen by projecting an image using a projector.

  The projection surface of the screen is generally made of a pure white material having a high reflectance. For this reason, the projection surface has a constant reflectance, but the way the image is projected varies greatly with this reflectance. Therefore, as shown in Patent Document 1, a screen has been proposed in which the reflectance of the projection surface automatically changes according to the projected light intensity.

JP 2000-75410 A

  However, in the conventional technique, the reflectance of the screen changes even by outside light, and the contrast is not always high. In particular, the black part became conspicuous due to the influence of external light.

  The present invention has been made in order to solve the above-described conventional problems, and an object thereof is to increase contrast and suppress black float.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
An image display system,
A light source;
A light valve that modulates light from the light source;
A projection optical system for projecting light from the light valve;
A screen that receives light from the projection optical system on a projection surface, and that can change the reflection / transmittance of the projection surface in units of blocks;
An image display system comprising: control means for controlling reflection / transmittance in a block on the projection plane corresponding to a portion on which the light is projected when the light from the light valve is projected onto the projection plane.

  Here, the reflection / transmittance refers to reflectivity or transmittance. When the screen is a reflective screen, the reflectivity / transmittance refers to the reflectivity, and when the screen is a transmissive screen, the reflectivity / transmittance refers to the transmissivity.

  According to the image display system described in Application Example 1, the light modulation is controlled by the light valve, and when the light from the light valve is projected onto the projection surface of the screen, the light is projected. By controlling the reflection / transmittance in the block on the projection plane, the illuminance of the projection plane determined by the product of the amount of light from the light valve and the reflection / transmittance can be changed. For this reason, it is possible to realize the illuminance of the projection surface according to the image signal and to control the reflectance of the projection surface to be small within the feasible range. Therefore, an image according to the image signal can be displayed with high contrast while suppressing the influence of external light.

[Application Example 2]
In the image display system according to application example 1, the control unit needs an illuminance for each pixel on the projection plane determined by a product of a light amount from the light valve and the reflection / transmittance according to the image signal. An image display system comprising a reflection / transmittance suppressing unit that suppresses the reflection / transmittance in the specified block to be less than the maximum reflection / transmittance of the screen within a range where the illuminance can be reduced.

  According to the optical device described in Application Example 2, it is possible to suppress the influence of external light while reliably realizing display of an image according to an image signal. As a result, contrast can be improved and black float can be suppressed.

[Application Example 3]
In the image display system according to application example 2, each block on the projection surface of the screen and each pixel included in the light valve have a 1: 1 correspondence, and the reflection / transmittance suppressing unit includes: A luminance calculating means for calculating luminance for each pixel from the image signal, and when the reflection / transmittance of the screen is a minimum value and the light quantity from the light valve is a maximum value that can be changed by the light valve. The illuminance for each pixel on the projection surface is set as comparative illuminance, and when the luminance for each pixel calculated by the luminance calculation means is lower than the comparative illuminance, the reflection / transmittance of the block corresponding to the pixel having the luminance is determined. The light amount from the light valve is changed after setting the minimum value, and when the calculated luminance for each pixel is equal to or greater than the comparative illuminance, the light amount from the light valve is changed. And a light valve screen control means for varying the reflection and transmission factor of the block corresponding to the pixel of the luminance after having determined the maximum value that can be changed in the light valve, an image display system.

  According to this configuration, when each block on the projection surface of the screen corresponds to each pixel included in the light valve on a 1: 1 basis, the reflection / transmissivity in the block on the projection surface is displayed according to the image signal. Can be minimized to the extent that can be realized.

[Application Example 4]
In the image display system according to application example 2, each block on the projection surface of the screen and each pixel included in the light valve are configured to correspond in a plurality of 1: the reflection / transmittance suppressing unit includes: A luminance calculation unit that calculates a luminance for each pixel from the image signal, a luminance distribution calculation unit that calculates a luminance distribution corresponding to each block of the screen from the calculated luminance for each image, and the luminance distribution calculation unit Normalizing means for normalizing the luminance distribution of the pixels corresponding to each block to be within the light amount width when the luminance distribution for each block obtained by the above is deviated from the light amount width changeable by the light valve; When the maximum luminance of the plurality of pixels corresponding to each block is realized, a shortage that is insufficient with the maximum light quantity that can be changed by the light valve is calculated, and the shortage is calculated. Determine the reflection and transmission factor of the block Zui, and a light valve screen control means for changing the amount of light from the light valve on which holds the reflection and transmission of the block, the image display system.

  According to this configuration, in the case where each block on the projection surface of the screen corresponds to each pixel included in the light valve in a 1: multiple manner, reflection / transmittance in the block on the projection surface can be minimized. .

[Application Example 5]
An image display system according to application examples 1 to 4,
An image display system comprising a projector including the light source, a light valve, a projection optical system, and control means.

  According to this configuration, the screen can be controlled by the projector.

[Application Example 6]
An image display system,
A projector that modulates light with a light valve;
A screen that receives light from the projector on a projection surface, and that can change the reflection / transmittance of the projection surface in units of blocks;
A photographing means for photographing the projection surface of the screen in a state where the screen is not receiving projection from the projector;
A luminance distribution calculating means for obtaining a luminance distribution on the projection plane based on an image photographed by the photographing means;
Reflection distribution calculating means for obtaining a screen reflectance distribution for external light correction based on the obtained luminance distribution;
When projecting the light modulated by the projector onto the projection plane, the reflection / transmittance in the block on the projection plane and the light valve of the light valve are calculated based on the screen reflectance distribution obtained by the reflection distribution calculating means. An image display system comprising: control means for controlling light modulation characteristics.

  According to the image display system described in Application Example 6, the projection surface of the screen is photographed in a state where the screen is not projected from the projector, and the luminance distribution on the projection surface is calculated based on the photographed image. As a result, the luminance distribution generated on the screen by external light can be known. Therefore, the screen reflectance distribution for correcting external light is obtained based on the luminance distribution, and the reflection / transmittance in the block on the projection surface and the light modulation characteristics of the light valve are controlled based on the clean reflectance distribution. Thus, the luminance distribution generated on the screen by the external light can be suppressed. Therefore, it is possible to display an image with high contrast while suppressing the influence of external light.

[Application Example 7]
An image display method,
The light from the light source is modulated by the light valve,
Projecting the modulated light by a projection optical system,
The projected light is received by the projection surface of the screen and an image is displayed.
An image display method for controlling reflection / transmittance in a block on the projection surface corresponding to a portion on which the light is projected when light from the light valve is projected onto the projection surface.

  According to the image display method described in Application Example 7, as in Application Example 1, an image according to the image signal can be displayed with high contrast while suppressing the influence of external light.

[Application Example 8]
An image display method,
Shoot the projection surface of the screen in a state where the screen that can change the reflection / transmittance of the projection surface in units of blocks is not receiving projection from the projector,
Obtaining a luminance distribution on the projection plane based on the captured image;
Based on the obtained luminance distribution, obtain a screen reflectance distribution for external light correction,
An image display method for controlling reflection / transmittance in a block on the projection plane and light modulation characteristics of a light valve provided in the projector based on the obtained screen reflectance distribution.

  According to the image display method described in Application Example 8, similarly to Application Example 6, it is possible to display an image with high contrast while suppressing the influence of external light.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
A1. Overall configuration of the image display system:
A2. Control processing:
A3. Action / effect:
B. Second embodiment:
C. Third embodiment:
D. Other embodiments:

A. First embodiment:
A1. Overall configuration of the image display system:
FIG. 1 is a block diagram showing the overall configuration of an image display system 10 as a first embodiment of the present invention. The image display system 10 includes a projector 100 and a screen 200.

  The projector 100 mainly includes a video signal processing unit 110, a liquid crystal panel driving circuit 120, a screen driving circuit 130, a liquid crystal panel 140, a light source unit 150, and a projection lens 160, and inputs to the video signal processing unit 110. The incoming video signal is displayed on the screen 200.

  The video signal processing unit 110 is configured by a so-called microcomputer, and includes a CPU 111, a ROM 113, a RAM 115, a video signal input circuit 117, and a system bus 119 that interconnects them. The system bus 119 is connected to a liquid crystal panel drive circuit 120 and a screen drive circuit 130.

  The CPU 111 is a central processing unit. The ROM 113 is a read-only memory that stores various built-in computer programs and various constants described later. The RAM 115 is a readable / writable memory that stores various data and the like. The video signal input circuit 117 takes in a video signal input from the outside. The video signal is input to the video signal processing unit 110 in real time by an input device such as a camera, a scanner, or a personal computer (not shown), or read from the computer-readable storage medium (not shown) to the video signal processing unit 110. Any of them may be used. Here, the computer-readable storage medium may be any of DVD-ROM, CD-ROM, FD, MD, and the like. The CPU 111 operates the liquid crystal panel drive circuit 120 and the screen drive circuit 130 by reading a predetermined computer program Pr stored in the ROM 113 and executing processing according to the computer program Pr.

  The liquid crystal panel drive circuit 120 is a circuit that drives the liquid crystal panel 140. The liquid crystal panel 140 is a transmissive liquid crystal panel that visualizes the signal generated by the liquid crystal panel drive circuit 120, and modulates light emitted from the light source unit 150 so that light necessary for projection is directed toward the screen 200. Eject. The liquid crystal panel 140 may be a reflective liquid crystal panel instead of the transmissive liquid crystal panel. Furthermore, instead of the liquid crystal panel, another type of light valve using a DMD (Digital Micromirror Device) or the like may be used. DMD is a trademark of Texas Instruments Incorporated.

  The light source unit 150 is a light source for projecting an image, and mainly includes a lamp 151 that emits light and a lens 152 that condenses the light emitted from the lamp 151. The projection lens 160 is a lens that enlarges and displays the light projected from the light source unit 150 on the screen 200.

  The screen drive circuit 130 is a circuit that drives the screen 200. Screen 200 has a projection surface for displaying a projection image projected from projection lens 160 of projector 100. The screen 200 can change the reflectance of the projection surface. The screen driving circuit 130 performs driving for changing the reflectance of the projection surface of the screen 200. The configuration for changing the reflectivity of the projection surface uses an electrophoresis method using microcapsules, and is as follows.

  FIG. 2 is an explanatory diagram showing the internal structure of the screen 200. In the screen 200, both surfaces of a light control layer 210 made of a microcapsule CP enclosing a blue liquid A and white charged particles (titanium oxide particles) W are sandwiched between glass substrates 220 and 230 with a transparent electrode, and a transparent electrode on one side A reflective plate 240 is provided on the front surface of the glass substrate 220 and is integrated. When the white charged particles W are on the front side of the microcapsule CP, the display surface appears white. Here, when a negative voltage is applied to the electrode of the glass substrate 230 disposed on the back side of the microcapsule, the white charged particles W are attracted to the back side, so that a blue liquid is displayed (state in FIG. 2). ). This is “black” on the projection plane 250. With this configuration, the reflectance of the projection surface 250 can be varied.

  FIG. 3 is an explanatory diagram showing an outline of blocks defined on the projection plane 250 of the screen 200. As shown in the drawing, the projection plane 250 can be divided into m pieces in the horizontal direction and n pieces in the vertical direction, and the reflectance can be individually changed for each of the m × n blocks. The number of blocks m × n is preferably equal to or more than the number of pixels of the liquid crystal panel 140, and in this embodiment, the number of blocks is the same as the number of pixels of the liquid crystal panel 140. That is, in the present embodiment, each block on the projection plane 250 and each pixel included in the liquid crystal panel 140 have a configuration that corresponds 1: 1.

  The screen 200 may have a configuration in which a light control material is sealed in silicon beads or the like instead of the configuration including the microcapsules. Furthermore, it can be replaced with a polymer dispersed liquid crystal, a magnet board, or the like. Further, the screen 200 may be a rear type integrally assembled as the projector 100 or a front type separately provided.

  The screen 200 having the above-described configuration can actively change the reflectance as described above, but the range that can be changed varies depending on the configuration. The variable range of the reflectance of the screen 200 of this embodiment is, for example, 100 to 30 [%]. Hereinafter, the lower limit value of the variable range is referred to as the minimum reflectance Rmin, and the upper limit value of the variable range is referred to as the maximum reflectance Rmax.

  The projector 100 having the above configuration operates as follows. The video signal processing unit 110 receives an input video signal by the video signal input circuit 117, and the CPU 111 controls the liquid crystal panel drive circuit 120 and the screen drive circuit 130 according to the video signal. The liquid crystal panel 140 modulates and transmits the light from the light source unit 150 by control according to the modulation command signal from the liquid crystal panel drive circuit 120. The modulated light is projected onto the screen 200 through the projection lens 160 and an image is displayed on the screen 200. The screen 200 changes the reflectance of the projection surface 250 in units of blocks by control according to the reflectance command signal from the screen driving circuit 130.

  FIG. 4 is an explanatory diagram showing how the illuminance of the projection surface of the screen 200 is determined in comparison with the conventional example. As shown in the figure, the horizontal axis of the graph shows the conventional example and the present example, and the vertical axis shows the projection plane illuminance. The illuminance on the projection surface of the screen corresponds to the product of the amount of light emitted from the projector and the reflectance of the screen. In the conventional example, the reflectance of the screen is constant (for example, 50%), and the amount of light emitted from the projector is changed to large or small as indicated by □ K2 and K3 in the right column. The illuminance on the projection surface of the screen corresponds to the product of the amount of light emitted from the projector and the reflectance of the screen, and thus changes as shown by □ K6 and K7.

  On the other hand, in this embodiment, the reflectance of the screen 200 can also be actively changed, and the reflectance is changed from 30% to 100%. As shown in □ K1 and K4, if the amount of light emitted from the projector is changed to be large or small (K1 is the same light amount as K2 and K4 is the same light amount as K3), the illuminance on the projection surface of the screen is Since this corresponds to the product of the amount of light emitted from the screen and the reflectance of the screen, in the present embodiment in which both can be changed, the area of the projection plane illuminance can be expanded as indicated by K5 and K8. it can. As a result, contrast can be improved.

A2. Control processing:
Hereinafter, the control process executed by the video signal processing unit 110 will be described in detail. This control process is stored in the ROM 113 in the form of the computer program Pr described above.

  FIG. 5 is a flowchart showing display control processing executed by the CPU 111 of the video signal processing unit 110. As shown in the figure, when the process is started, the CPU 111 operates the video signal input circuit 117 to execute a process of receiving a video signal (step S110).

Next, the CPU 111 extracts pixel data for one pixel from the video signal (step S120), and calculates the luminance L of the pixel data (step S130). As a calculation method, for example, a conversion formula of the following formula (1) for directly obtaining the luminance from the RGB value used in the case of a television or the like is used.
y = 0.30R + 0.59G + 0.11B (1)

  Thereafter, the CPU 111 calculates the illuminance of the projection surface of the screen 200 when the reflectance of the screen 200 is the minimum reflectance Rmin and the transmittance of the liquid crystal panel 140 is the maximum transmittance Tmax, and the calculated illuminance is for comparison. It memorize | stores as illumination intensity LS (step S140). The illuminance L of the projection surface of the screen 200 corresponds to the product of the light amount I emitted from the light source unit 150, the transmittance T of the liquid crystal panel 140, and the reflectance R of the screen 200. The conversion formula of Formula (2) is used.

  LS = I × Tmax × Rmin (2)

  The light amount I, the minimum reflectance Rmin, and the maximum transmittance Tmax are constant values determined by the light source unit 150, the screen 200, and the liquid crystal panel 140, and are stored in the ROM 113 in advance. Note that the value of the comparison illuminance LS itself may be stored in the ROM 113 in advance instead of the configuration calculated using the above equation (2).

  Subsequently, the CPU 111 determines whether or not the luminance L calculated in step S130 is smaller than the comparison illuminance LS (step S150). If it is determined that the luminance L is smaller than the comparison illuminance LS, the CPU 111 sets the control amount XL2 of the screen 200 to the minimum reflection value Rmin of the screen 200 (step S160), and the following equation (3 ), The control amount XL1 of the liquid crystal panel 140 is determined (step S170). The Rmin is stored in advance in the ROM 113.

  XL1 = L / (Rmin × I) (3)

  Here, L is the luminance calculated in step S130. I is the light quantity I described above. I and Rmin are stored in advance in the ROM 113, respectively.

  On the other hand, if it is determined in step S150 that the luminance L is equal to or greater than the comparison illuminance LS, the CPU 111 determines the control amount XL1 of the liquid crystal panel 140 as the maximum transmittance value Tmax that can be changed by the liquid crystal panel 140. At the same time (step S180), the control amount XL2 of the screen 200 is determined according to the following equation (4) (step S190). The Tmax is stored in advance in the ROM 113.

  XL2 = L / (Tmax × I) (4)

  After execution of step S170 or S190, the CPU 111 transmits a signal corresponding to the control amount XL1 of the liquid crystal panel 140 to the liquid crystal panel drive circuit 120 (step S200) and also to the screen drive circuit 130 according to the control amount XL2 of the screen 200. The transmitted signal is transmitted (step S210). As a result of the process in step S200, light modulated according to the control amount XL1 is projected from the liquid crystal panel 140, and as a result of the process in step S210, the reflectance of the block on the projection surface corresponding to the portion on which the light is projected. Is controlled according to the control amount LX2.

  Thereafter, the CPU 111 determines whether or not the pixel data extracted in step S120 is the last (step S220). If it is determined that the pixel data is not the last, the process returns to step S120 to extract the subsequent pixel data. . The processes in steps S120 to S220 are repeated until the pixel data becomes the last. If the determination in step S220 is affirmative, the process goes to “END” and the display control process ends.

  FIG. 6 is a graph showing the control contents realized by the display control processing of the above configuration. A line segment Q with dots at both ends in the figure is a light quantity width LW that can be changed by the liquid crystal panel 140. The reason why there are a plurality of line segments Q is that the screen reflectivity is changed. The illuminance L of the projection surface of the screen 200 corresponds to the product of the light amount I emitted from the light source unit 150, the transmittance T of the liquid crystal panel 140, and the reflectance R of the screen 200. That is, the light quantity width LW that can be changed by the liquid crystal panel 140 varies depending on the reflectance of the screen 200 as well as the change amount of the transmittance of the liquid crystal panel 140. The larger the reflectance R of the screen 200, the larger the light quantity width LW.

  The range of the reflectance R that can be changed by the screen 200 is a range from Rmin to Rmax. The amount of light determined from the minimum reflectance Rmin is L2min, and the amount of light determined from the maximum reflectance Rmax is L2max. That is, the amount of light contributing to the projection surface illuminance L by the control of the screen 200 is in the range from L2min to L2max. The projection surface illuminance L of the screen 200 can be controlled within a trapezoidal region determined from the vertices A, B, C, and D in the figure by controlling the liquid crystal panel 140 and the screen 200. For example, in the drawing, the projection surface illuminance LZ can be realized at any position on the line segment EF within the trapezoidal region.

  The comparative illuminance LS corresponds to the point B in the figure because it is the illuminance of the projection surface of the screen 200 when the screen 200 has the minimum reflectance Rmin and the liquid crystal panel 140 has the maximum transmittance Tmax. When it is determined that the luminance L is smaller than the comparison illuminance LS (processing in step S150), control is performed within the range of the line segment AB in the figure. That is, the illuminance corresponding to the luminance L is realized by changing the amount of light from the liquid crystal panel 140 (processing in step S170) after setting the screen 200 to the minimum reflectance Rmin (processing in step S160).

  On the other hand, when it is determined that the luminance L is equal to or greater than the comparison illuminance LS (processing in step S150), control is performed within the range of line segment BC in the figure. That is, the illuminance corresponding to the luminance L is realized by changing the reflectance of the screen 200 (processing in step S190) after setting the liquid crystal panel 140 to the maximum transmittance Tmax (processing in step S180). By setting the liquid crystal panel 140 to the maximum transmittance Tmax and setting the light quantity that can be changed by the liquid crystal panel 140 to the maximum value, the light quantity contributing to the projection plane illuminance L is made as small as possible by controlling the screen 200.

  Eventually, when the luminance L is smaller than the comparative illuminance LS and the luminance L is equal to or higher than the comparative illuminance LS, the projection surface illuminance L is within a range that can be determined by the video signal. Control is performed to keep the reflectance R as small as possible.

  In the present embodiment, the process in steps S150 to S190 is configured to perform the process along the line segment AB or line segment BC in FIG. 6, but instead of the process in steps S150 to S190, The line segments A-B and B-C in the graph of FIG. 6 may be stored as map data as they are, and the control amounts of the liquid crystal panel 14 and the screen 200 may be determined by searching the map data.

A3. Action / effect:
According to the image display system 10 of the present embodiment configured as described above, the reflectance in the block on the projection surface of the screen 200 can be suppressed as small as possible. For this reason, since the influence of external light can be suppressed, there is an effect that black floating can be suppressed.

B. Second embodiment:
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment only in the screen resolution and the control processing executed by the video signal processing unit 110, and the other configurations are the same. The same parts as in the first embodiment will be described below with the same parts as in the first embodiment.

  FIG. 7 is an explanatory diagram showing a comparison between the number of blocks included in the projection plane 350 of the screen and the number of pixels of the liquid crystal panel 340. In the first embodiment, the number of blocks included in the projection surface 250 of the screen 200 is equal to or greater than the number of pixels of the liquid crystal panel 140. On the other hand, in the second embodiment, as shown in FIG. The number v of blocks included in the projection plane 350 is smaller than the number u of pixels of the liquid crystal panel 140. For this reason, the number of pixels of the liquid crystal panel 340 projected onto one block BL on the projection surface 350 is u / v. That is, the u / v pixel group PN of the liquid crystal panel 340 corresponds to one block BL of the projection plane 350. In other words, each block BL on the projection surface 350 of the screen and each pixel included in the liquid crystal panel 140 correspond to 1: n (n is a plurality).

  FIG. 8 is a graph showing the control content realized by the control process executed by the video signal processing unit 110 in the second embodiment. Before explaining the routine of the control process, the control contents will be described in advance with reference to FIG. Trapezoids A, B, C, and D in the figure are the same as those in FIG. 6 of the first embodiment. By controlling the liquid crystal panel 140 and the screen 200, trapezoids A, B, C, and D in the figure are shown. Control within the area becomes possible.

  However, in actuality, since each block BL on the projection surface 350 of the screen and each pixel of the liquid crystal panel 140 correspond to each other in a 1: multiple, the screen side of the one pixel group PN (FIG. 7) described above is used. The reflectance is limited to a value of 1 block. Therefore, when projecting light from one pixel group PN onto the projection plane 350, it is necessary to set the reflectance of one block BL corresponding to one pixel group PN to an optimum value.

  Therefore, in this embodiment, the luminance distribution for a plurality of pixels included in one pixel group PN is obtained, and when the width of the luminance distribution is larger than the maximum light amount width LWmax that can be changed by the liquid crystal panel 140, that is, the luminance When the distribution deviates from the light amount width LWmax, preprocessing for normalizing the luminance of the pixels included in the pixel group PN so as to be within the light amount width LWmax is performed in advance. When the width of the luminance distribution is equal to or smaller than the light amount width LWmax, the normalization pixel conversion is not performed.

  In FIG. 8, for example, the section TL of the projection surface illuminance corresponds to the luminance distribution of the pixels included in the pixel group PN (the luminance distribution of the normalized pixel when normalized). To do. In order to realize the projection plane illuminance in this section TL, it is necessary to control the screen reflectivity between R1 and R2. If the screen reflectance is smaller than R1, even if the light amount from the liquid crystal panel 140 is the maximum value, the value on the maximum value side of the section TL cannot be realized. On the other hand, if the screen reflectance is larger than R2, This is because even if the light amount from the liquid crystal panel 140 is set to the minimum value, a value on the minimum value side of the section TL cannot be realized.

  In the present embodiment, similar to the first embodiment, the object is to prevent black floating. For this purpose, it is desired to reduce the screen reflectivity as much as possible in order to suppress the influence of external light. For this reason, control is performed so that the side having the smaller reflectance in the section from the screen reflectance R1 to R2 described above, that is, the screen reflectance is R1. In this case, as can be seen from FIG. 8, in the case of the maximum value (maximum luminance) in the section TL, the light amount from the liquid crystal panel 140 is set to the maximum value, and for values other than the maximum luminance in the section TL, the liquid crystal The desired value is realized by changing the amount of light from the panel 140.

  FIG. 9 is a flowchart showing display control processing in the second embodiment. This flowchart is for realizing the control content described above with reference to FIG. As shown in the figure, when the process is started, the CPU 111 operates the video signal input circuit 117 to execute a process of receiving a video signal (step S310).

  Next, the CPU 111 identifies one black BL on the projection surface 350 of the screen, extracts a plurality of pixel data corresponding to the one block BL (step S320), calculates the luminance L of the pixel data, and calculates the luminance. A luminance histogram representing the distribution of L is created (step S330).

  Thereafter, the CPU 111 determines whether or not the width of the luminance histogram, that is, the luminance difference between the maximum luminance and the minimum luminance is larger than the maximum light amount width LWmax that can be changed by the liquid crystal panel 140 (step S340). The maximum light amount width (hereinafter referred to as “maximum light amount width”) LWmax is a value at which the reflectance R of the screen 200 with respect to the light amount width LW that can be changed by the liquid crystal panel 140 is maximized. Here, when it is determined that the width of the luminance histogram is larger than the maximum light amount width LWmax, the pixel data is normalized so that the width of the luminance histogram is within the maximum light amount width LWmax (step S350). .

  FIG. 10 is a graph for explaining the normalization process. The horizontal axis of the graph represents luminance, and the vertical axis represents the number of pixels for each luminance. Now, it is assumed that the luminance histogram HG created in step 330 has a luminance distribution indicated by a solid line in the figure. In the illustrated example, the width HW of the luminance histogram HG is larger than the maximum light amount width LW. Therefore, first, the position of the maximum light quantity width LW is moved to the left and right in the figure, and the position of the maximum light quantity width LW is determined so that the total number of pixels included in the maximum light quantity width LW is maximized. Normalize to fit within the width. As normalization processing, tone mapping (F. Drago, Kmyszkowski, T. Annen, N. chiba, “Adaptive Logarithmic Mapping For Displaying High Contrast Screens”, Eurographics 2003) is used. The two-dot chain line in FIG. 10 is the normalized luminance histogram HG ′. As a result, the pixel data extracted in step S320 is subjected to normalization pixel conversion as necessary.

  Returning to FIG. 9, after execution of step S350, the process proceeds to step S355. When it is determined in step S340 that the width HW of the luminance histogram is equal to or smaller than the light amount width LW, the CPU 111 immediately proceeds to step S355 without executing step S350. In step S355, the CPU 111 changes the luminance distribution of the projection surface of the screen 200 obtained by changing the light valve transmittance from the minimum transmittance Tmin to the maximum transmittance Tmax (when normalization is performed in step S350). Performs the process of calculating the minimum reflectance Ra of the screen 200 when including the normalized luminance distribution). That is, the minimum value among the reflectances R of the screen satisfying the relationship of the following formula (5) is obtained as Ra.

  I × Tmin × R ≦ Luminance distribution ≦ I × Tmax × R (5)

  Thereafter, the CPU 111 sets the screen control amount XL2 to the reflectance Ra calculated in step S355.

  Thereafter, the CPU 111 transmits a signal corresponding to the control amount XL2 of the screen 200 to the screen driving circuit 130 (step S370). This process is the same as step S210 of the first embodiment.

  Subsequently, the CPU 111 extracts the luminance L for a plurality of pixel data (normalized pixel data after normalization) corresponding to the block BL identified in step S320 (step S380). Next, the CPU 111 determines the control amount XL1 of the liquid crystal panel 140 according to the following equation (6) (step S390).

  LW = I × Ra × (Tmax−Tmin) (6)

  Thereafter, the CPU 111 transmits a signal corresponding to the control amount XL1 of the liquid crystal panel 140 to the liquid crystal panel drive circuit 120 (step S400). This process is the same as step S200 of the first embodiment.

  After executing step S400, the CPU 111 determines whether or not the luminance extracted in step S380 is for the last pixel data in the block BL (step S410). The process returns to step S380 to extract the luminance L of the subsequent pixel data. The processes in steps S380 to S410 are repeated until the pixel data becomes the last, and if an affirmative determination is made in step S410, the process proceeds to step S420.

  In step S420, it is determined whether or not the block BL identified in step S320 is the last one. If it is determined that the block BL is not the last, the process returns to step S320 to perform the process for the subsequent block. The processes in steps S320 to S420 are repeated until the block BL comes to the end, and when an affirmative determination is made in step S420, the process goes to “END” and the display control process is terminated.

  According to the image display system 10 of the second embodiment configured as described above, as described above, each block BL on the projection surface 350 of the screen corresponds to each pixel of the liquid crystal panel 140 in a plurality. Even in this case, the reflectance of the block BL on the projection plane 350 can be suppressed as small as possible. For this reason, since the influence of external light can be suppressed, there is an effect that black floating can be suppressed.

C. Third embodiment:
FIG. 11 is a block diagram showing the overall configuration of an image display system 400 as a third embodiment of the present invention. The image display system 400 includes a projector 405, a screen 410, a camera 420, and a control unit 430.

  The projector 405 includes a light valve (not shown), and performs light modulation using the light valve.

  The screen 410 is the same as the screen 200 of the first embodiment. In other words, the screen 410 can change the reflectance of the projection surface in units of blocks. The camera 420 is a photographing unit that photographs the projection surface of the screen 410. The photographer shoots the projection surface in a state where the screen 200 is not receiving projection from the projector 405.

  The control unit 430 is configured by a so-called microcomputer and includes a CPU, a ROM, a RAM, and the like. The control unit 430 is electrically connected to the camera 420 and captures an image captured by the camera 420. The control unit 430 is electrically connected to a screen driving circuit 440 that drives the screen 410. The screen drive circuit 440 is the same as the screen drive circuit 130 of the first embodiment. The control unit 430 is electrically connected to the projector 405. The control unit 430 performs light modulation by controlling the light valve of the projector 405, and changes the reflectance of the projection surface of the screen 410 in units of blocks by controlling the screen driving circuit 440.

  FIG. 12 is a flowchart executed by the control unit 430. As illustrated, the control unit 430 first captures an image captured by the camera 420 (step S510), and obtains a luminance distribution on the projection plane based on the captured image (step S520). Next, the control unit 430 obtains a screen reflectance distribution for external light correction based on the luminance distribution obtained in step S520 (step S530). Thus, data indicating the screen light reflectance distribution for external light correction is stored in the control unit 430.

  FIG. 13A shows the luminance distribution on the projection plane obtained in step S520. This luminance distribution is due to external light hitting the projection surface. FIG. 13B shows the screen light reflectance distribution for external light correction obtained in step S530. In step S530, a screen reflectance distribution for correcting external light is obtained by performing processing for inverting the reflectance on the luminance distribution obtained in step S520.

  Thereafter, when the control unit 430 projects the light modulated by the projector 405 onto the projection plane (step S540), the block on the projection plane is determined based on the screen reflectance distribution data obtained in step S530. (Step S550) and, based on the screen reflectance distribution data obtained in step S530, the light valve transmittance (corresponding to the light modulation characteristics) in the projector 405 is controlled (step S560). .

  In this embodiment, since the reflectance on the screen is not constant, the luminance shifts when the image is projected as it is. Therefore, in step S560, the transmittance of the light valve is controlled in accordance with the reflectance of the screen. Specifically, the transmittance XT of the light valve is obtained according to the following equation (7), and a control amount corresponding to the transmittance XT is sent to the light valve.

  XT = T × Rmax / R (7)

  According to the equation (7), the light valve transmittance XT of the projector 405 determined from the image signal is divided by the reflectance R of the screen and multiplied by the maximum value Rmax of the reflectance so that the light valve as a control value is obtained. The transmittance XT is obtained.

  As a result of steps S550 and S560, the correction according to FIG. 13B can be realized. As shown in FIG. 13C, the luminance on the screen excluding the pixels from the projector 405. The distribution is a combination of (A) and (B) in FIG. That is, the unevenness caused by the external light on the screen 410 is canceled by the external light correction screen reflectance distribution, and as shown in FIG. Become.

  According to the image display system 400 of the third embodiment configured as described above, the influence of external light can be suppressed as described above, so that black floating can be suppressed during display by the projector. There is an effect.

D. Other embodiments:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the scope of the invention.

(1) Modification 1:
In the first and second embodiments, the video signal processing unit 110 and the screen driving circuit 130 are provided in the projector 100. Instead, the screen driving circuit 130 and the video signal processing unit are provided outside the projector 100. 110 may be provided with a portion for calculating the control amount of the screen. That is, a projector that performs projection according to an image signal, a control unit that takes in the image signal and controls the screen according to the image signal, and a screen have the same functions as the first and second embodiments. It can also be realized.

(2) Modification 3:
In the first to third embodiments, the video signal processing unit 110 and the control unit 430 are configured by so-called microcomputers, but may be configured by discrete electronic circuits instead.

(3) Modification 3:
In the first or second embodiment, the control is performed such that the reflectance R of the screen 200 is minimized as long as the projection surface illuminance L can be a luminance determined from the video signal. Instead of this, the reflectance R may be less than the maximum reflectance Rmax of the screen. This configuration can also improve contrast.

(4) Modification 4:
In the first to third embodiments, the screens 200 and 410 are so-called reflective screens. However, instead of this, a configuration of a transmissive screen may be used. In this case, as a configuration in which the transmittance of the projection surface can be changed, the transmittance may be changed in place of the reflectance in the control processing of FIG. 5 of the first embodiment. In the second and third embodiments, the transmittance may be changed instead of the reflectance.

(5) Modification 5:
In the first to third embodiments, the liquid crystal panel 140 and the light valve are so-called transmissive light valves. However, instead of this, a configuration of a reflective light valve may be used. In this case, in the control process of FIG. 5 of the first embodiment, the reflectance may be changed in place of the transmittance of the light valve. In the second and third embodiments, the reflectance may be changed instead of the transmittance.

1 is a block diagram showing an overall configuration of an image display system 10 as a first embodiment of the present invention. 4 is an explanatory diagram showing an internal structure of a screen 200. FIG. FIG. 4 is an explanatory diagram illustrating an outline of blocks defined on a projection plane 250 of a screen 200. It is explanatory drawing which shows how the illumination intensity of the projection surface of the screen 200 is determined compared with a prior art example. 3 is a flowchart showing display control processing executed by a CPU 111 of a video signal processing unit 110. It is a graph which shows the control content implement | achieved by display control processing. It is explanatory drawing which shows the comparison with the number of blocks contained in the projection surface 350 of the screen in 2nd Example of this invention, and the number of pixels of the liquid crystal panel 340. FIG. It is a graph which shows the control content of 2nd Example. It is a flowchart which shows the display control process in 2nd Example. It is a graph for demonstrating a normalization process. It is a block diagram which shows the whole structure of the image display system 400 as 3rd Example of this invention. It is a flowchart which shows the display control process in 3rd Example. It is explanatory drawing which shows the control content of 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image display system 100 ... Projector 110 ... Video signal processing part 111 ... CPU
113 ... ROM
115 ... RAM
117 ... Video signal input circuit 119 ... System bus 120 ... Liquid crystal panel drive circuit 130 ... Screen drive circuit 140 ... Liquid crystal panel 150 ... Light source 151 ... Lamp 152 ... Lens 160 ... Projection lens 200 ... Screen 210 ... Light control layer 220 ... Glass Substrate 230 ... Glass substrate 240 ... Reflector 250 ... Projection surface 340 ... Liquid crystal panel 350 ... Projection surface 400 ... Image display system 405 ... Projector 410 ... Screen 420 ... Camera 430 ... Control unit 440 ... Screen drive circuit

Claims (8)

An image display system,
A light source;
A light valve that modulates light from the light source;
A projection optical system for projecting light from the light valve;
A screen that receives light from the projection optical system on a projection surface, and that can change the reflection / transmittance of the projection surface in units of blocks;
An image display system comprising: control means for controlling reflection / transmittance in a block on the projection plane corresponding to a portion on which the light is projected when the light from the light valve is projected onto the projection plane. The image display system according to claim 1,
The control means includes
The reflection / transmittance in the specified block is within a range in which the illuminance for each pixel on the projection plane determined by the product of the light amount from the light valve and the reflection / transmittance can be the illuminance required according to the image signal. An image display system comprising: reflection / transmittance suppression means for suppressing the screen to less than the maximum reflection / transmittance of the screen. The image display system according to claim 2,
Each block on the projection surface of the screen and each pixel included in the light valve are configured to correspond 1: 1.
The reflection / transmittance suppressing means is:
Luminance calculation means for calculating the luminance for each pixel from the image signal;
The illumination intensity for each pixel on the projection surface when the reflection / transmission rate of the screen is the minimum value and the light quantity from the light valve is the maximum value that can be changed by the light valve is used as the comparison illumination intensity, and the brightness When the luminance of each pixel calculated by the calculating means is lower than the comparative illuminance, the light quantity from the light valve is changed after setting the reflection / transmittance of the block corresponding to the pixel of the luminance to the minimum value. When the calculated luminance for each pixel is equal to or greater than the comparison illuminance, the light amount from the light valve is set to a maximum value that can be changed by the light valve, and the reflection of the block corresponding to the pixel having the luminance is performed. An image display system comprising: a light valve that changes transmittance, and screen control means. The image display system according to claim 2,
Each block on the projection surface of the screen and each pixel included in the light valve are configured to correspond by a plurality of 1:
The reflection / transmittance suppressing means is:
Luminance calculation means for calculating the luminance for each pixel from the image signal;
A luminance distribution calculating means for obtaining a luminance distribution corresponding to each block of the screen from the calculated luminance for each image;
When the luminance distribution for each block obtained by the luminance distribution calculating means deviates from the light amount width changeable by the light valve, normalization is performed so that the luminance of the pixel corresponding to each block is within the light amount width. Normalization means to
When realizing the maximum brightness among the plurality of pixels corresponding to each block, a shortage that is insufficient with the maximum amount of light that can be changed by the light valve is calculated, and the reflection / transmittance of the block is calculated based on the shortage And a light valve / screen control means for changing the amount of light from the light valve while maintaining the reflection / transmittance of the block. The image display system according to claim 1, wherein
An image display system comprising a projector including the light source, a light valve, a projection optical system, and control means. An image display system,
A projector that modulates light with a light valve;
A screen that receives light from the projector on a projection surface, and that can change the reflection / transmittance of the projection surface in units of blocks;
A photographing means for photographing the projection surface of the screen in a state where the screen is not receiving projection from the projector;
A luminance distribution calculating means for obtaining a luminance distribution on the projection plane based on an image photographed by the photographing means;
Reflection distribution calculating means for obtaining a screen reflectance distribution for external light correction based on the obtained luminance distribution;
When projecting the light modulated by the projector onto the projection plane, the reflection / transmittance in the block on the projection plane and the light valve of the light valve are calculated based on the screen reflectance distribution obtained by the reflection distribution calculating means. An image display system comprising: control means for controlling light modulation characteristics. An image display method,
The light from the light source is modulated by the light valve,
Projecting the modulated light by a projection optical system,
The projected light is received by the projection surface of the screen and an image is displayed.
An image display method for controlling reflection / transmittance in a block on the projection surface corresponding to a portion on which the light is projected when light from the light valve is projected onto the projection surface. An image display method,
Shoot the projection surface of the screen in a state where the screen that can change the reflection / transmittance of the projection surface in units of blocks is not receiving projection from the projector,
Obtaining a luminance distribution on the projection plane based on the captured image;
Based on the obtained luminance distribution, obtain a screen reflectance distribution for external light correction,
An image display method for controlling reflection / transmittance in a block on the projection plane and light modulation characteristics of a light valve provided in the projector based on the obtained screen reflectance distribution.

Images