JP2007219301A - Sensor unit, pixel-shifting unit, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device, etc. capable of reducing the unevenness due to temperature variation, variation due to time passage, or the like, and noise such as pseudo-contours and pseudo-colors. <P>SOLUTION: The image display device equipped with a display part 21, polarized turning liquid crystal cells 22 and 24, a pixel-shifting unit 20 including a birefringent plate, and a display optical part comprises: two polarizing plates 42 and 43, disposed in a parallel-nicol or in a cross-nicol manner so as to sandwich the polarized turning liquid crystal cells 22 and 24; a light-receiving element 44 for measuring the volume of the measuring light that has passed through the polarized turning liquid crystal cells 22 and 24, and the two polarizing plates 42 and 43; a system control microcomputer 51 for obtaining polarization characteristics of the polarized turning liquid crystal cells 22 and 24, based on the drive state information of the polarized turning liquid crystal cells 22 and 24, and the measured value by the light-receiving element 44; and a correction calculation block 52 for correcting the image information to be supplied to the display part 21, based on the obtained polarization characteristics. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sensor unit for measuring the polarization characteristics of a polarization-rotating liquid crystal cell, a pixel shifting unit including the sensor unit, and an image display device including the pixel shifting unit.

  As demands for further increasing the resolution of image display apparatuses are increasing, so-called wobbling techniques have been studied as a technique for obtaining a resolution higher than the resolution of display elements arranged in the image display apparatus.

  This wobbling technology is a technology that increases the visual resolution perceived by humans by shifting the image position of each pixel of the display element on the display surface in a time-sequential manner (higher resolution by shifting pixels). Technology). More specifically, an image display device using this wobbling technology includes, for example, a polarization-rotating liquid crystal cell for rotating the polarization direction of light from the display element by 90 degrees, and the presence or absence of a light beam shift depending on the polarization direction. And a birefringent plate that generates

  Among these, the polarization rotation liquid crystal cell selects whether the polarization direction is rotated 90 degrees or not according to on / off of the applied voltage. Therefore, by controlling this polarization rotation liquid crystal cell, it is possible to control the pixel shift timing by the light beam shift. Details of such a technique are described in, for example, Japanese Patent Application Laid-Open No. 11-326877.

  By the way, light generated as, for example, circularly polarized light from the illumination light source and converted into linearly polarized light in one direction by the polarizing means is incident on the polarization rotating liquid crystal cell. At this time, the polarization swivel liquid crystal cell is basically operated so that the polarization direction does not rotate at all when driven, and the polarization direction rotates 90 degrees when not driven. However, it is known that when the liquid crystal cell is not driven, the rotation of the polarization direction is not always an ideal 90 degrees. In this case, the light emitted from the polarization rotation liquid crystal cell does not become linearly polarized light rotated 90 degrees, but becomes elliptically polarized light including orthogonal components. When this elliptically polarized light passes through the birefringent plate, part of the light travels straight and part of the light is shifted. Therefore, in the pixel information shifted by the state of elliptically polarized light, an error due to the elliptically polarized light is generated as noise such as false color, unevenness, and pseudo contour. For example, if the pixel aperture ratio is not 100%, these false colors not only appear at the edge portion of the image but also repeat unevenness in the vicinity of four pixels in the flat portion of the image (so-called four points). In the case of wobbling), for example, the image looks rough.

  In addition, when the image display device is a projection-type image display device such as a projector, these false colors and unevenness become more conspicuous as the zoom magnification of the optical system is increased and displayed.

  By the way, since various characteristics of liquid crystals (including a polarization rotation liquid crystal cell) change depending on the temperature, it is desirable to measure the temperature of the liquid crystal for stable and high-quality display. Therefore, for example, Japanese Patent Laid-Open No. 2000-284255 discloses a technique for measuring the response time characteristic and calculating the temperature of the liquid crystal by utilizing the fact that the response time characteristic among various characteristics of the liquid crystal depends on the temperature. Are listed. Thus, the temperature of the image display liquid crystal (the liquid crystal described in the publication is not a wobbling liquid crystal) can be measured without using an expensive temperature measuring element. Japanese Patent Laid-Open No. 11-326877 described above describes a technique for monitoring the temperature of a polarization rotation liquid crystal cell. Further, various techniques for stabilizing the display by controlling the temperature characteristics of the response time of the liquid crystal have been developed.

In addition, as an index for evaluating the characteristics of the liquid crystal, a polarizing plate having a constant polarization direction is arranged before and after the optical path sandwiching the liquid crystal, and when the liquid crystal is driven in this state and when it is not driven It is common to measure the signal level in two states and use the extinction ratio obtained by taking these ratios.
Japanese Patent Laid-Open No. 11-326877 JP 2000-284255 A

  In the wobbling technique as described above, when suppressing noise such as false color, unevenness, and pseudo contour due to the polarization characteristics of the polarization swivel liquid crystal cell (hereinafter collectively referred to as false color correction), It can be considered as a solution to measure the characteristics of the liquid crystal in advance, store the measured characteristic information, and correct the image information by the display device based on the stored characteristic information (however, the above-mentioned patent documents) Does not disclose a technique for measuring the polarization characteristics of a polarization-rotating liquid crystal cell. However, in such a system, it is not possible to follow changes in liquid crystal characteristics due to temperature changes and aging.

  Further, in addition to the above, when measuring the polarization characteristics of the liquid crystal in advance, the measurement is performed for each temperature, the characteristic information measured for each temperature is stored, and based on the temperature of the liquid crystal detected in real time. A technique for calculating the polarization characteristics at the temperature is also conceivable. If such a technique is used, it becomes possible to correct the temperature characteristics, but it is still impossible to cope with aging. Therefore, even if such a technique is used, there is a problem of correction accuracy in that the correction error increases as the usage time increases.

  The present invention has been made in view of the above circumstances, and provides a sensor unit, a pixel shift unit, and an image display device that can reduce noise such as unevenness due to temperature change and aging, pseudo contour, and false color. The purpose is that.

  In order to achieve the above object, a sensor unit according to a first aspect of the present invention is a sensor unit for measuring the polarization characteristics of a polarization rotation liquid crystal cell for wobbling display of an image. A first polarizing means that is arranged on the side and allows only light of a predetermined first polarization direction in the measurement light to pass through; and a first polarizing means that is arranged on the other side of the polarization rotation liquid crystal cell. A second polarizing means that passes only light of a predetermined second polarization direction in the measurement light that has passed through the polarizing means and then passed through the polarizing swivel liquid crystal cell, and is disposed on the other side of the polarizing swivel liquid crystal cell A light receiving means for measuring the light quantity of the measuring light which has been made and passed through the second polarizing means, information on the driving state of the polarization swivel liquid crystal cell and measurement of the light quantity received by the light receiving means A measuring means for determining the polarization characteristics of the polarizing rotation liquid crystal cell based on the bets are those provided with the.

  According to a second aspect of the present invention, there is provided a pixel shifting unit that is arranged between the sensor unit according to the first aspect of the present invention, the first polarizing means, and the second polarizing means, and transmits modulated light related to an incident image. A polarization rotation liquid crystal cell for performing wobbling display of an image by controlling whether or not to rotate the polarization, and a birefringent plate on which modulated light that has passed through the polarization rotation liquid crystal cell is incident. is there.

  Furthermore, an image display device according to a third aspect of the invention is a pixel shift unit according to the second aspect of the invention, and an image modulation means for emitting modulated light modulated in accordance with input image information toward the polarization rotation liquid crystal cell. Display optical means for displaying the modulated light that has passed through the birefringent plate so as to be observable, and a correction parameter for image information correction calculation based on the polarization characteristic obtained by the measurement means, and calculating the correction parameter And an image information correction calculating means for correcting the image information by using the image information.

  A pixel shifting unit according to a fourth invention is the pixel shifting unit according to the second invention, wherein the first polarizing means and the second polarizing means are arranged in parallel Nicols.

  A pixel shifting unit according to a fifth invention is the pixel shifting unit according to the second invention, wherein the first polarizing means and the second polarizing means are further arranged in crossed Nicols.

  A pixel shifting unit according to a sixth invention is the pixel shifting unit according to the fifth invention, wherein two sets of the first polarizing means and the second polarizing means are provided, and one set is fixed. Arranged in parallel Nicols, the other set is fixedly arranged in crossed Nicols.

  A pixel shifting unit according to a seventh aspect is the pixel shifting unit according to the fifth aspect, wherein the arrangement of parallel Nicols and the crossed Nicols are time-divisionally arranged on the first polarizing means and the second polarizing means. Further, switching means for switching so as to be taken is further provided.

  The pixel shifting unit according to an eighth aspect of the present invention is the pixel shifting unit according to the sixth or seventh aspect of the present invention, wherein the polarization swivel liquid crystal cell includes a display region that is a region through which a display light beam passes, and the display region. The first polarizing means, the second polarizing means, and the light receiving means are arranged on the optical path of the measurement light passing through the detection area. Is arranged.

  A pixel shifting unit according to a ninth aspect is the pixel shifting unit according to the eighth aspect, further comprising a measurement light source for emitting the measurement light.

  A pixel shifting unit according to a tenth aspect of the invention is the pixel shifting unit according to the fourth or fifth aspect of the invention, in which at least the second polarizing means and the light receiving means in the sensor unit are replaced with a light beam for display in the polarization swivel liquid crystal cell. Is further provided with moving means for moving to a position retracted from the display area, which is a region through which the light passes, and a position disposed on the optical path of the display light beam passing through the display area.

  The pixel shifting unit according to an eleventh aspect of the invention is the pixel shifting unit according to the fourth aspect of the invention, wherein the measuring means calculates the ratio between the white level in the parallel Nicol state and the black level in the parallel Nicol state, To do.

  A pixel shifting unit according to a twelfth aspect of the present invention is the pixel shifting unit according to the fifth aspect of the present invention, wherein the measuring means includes four levels of white level and black level in a parallel Nicol state and white level and black level in a crossed Nicol state. The calculation is performed using two values to obtain the polarization characteristics.

  A pixel shifting unit according to a thirteenth aspect is the pixel shifting unit according to the second aspect, wherein the measuring means calculates a plurality of polarization characteristics based on a plurality of measurement values, and polarizes an average value of the plurality of polarization characteristics. It is a characteristic.

  A pixel shifting unit according to a fourteenth aspect of the invention is the pixel shifting unit according to the second aspect of the invention, wherein the measuring means has a predetermined usage time of the polarization rotation liquid crystal cell from the time when the polarization characteristic of the polarization rotation liquid crystal cell was previously obtained. When the time is reached, the polarization characteristics of the polarization rotation liquid crystal cell are newly obtained.

  A pixel shifting unit according to a fifteenth aspect of the invention is the pixel shifting unit according to the second aspect of the invention, further comprising temperature detecting means for measuring the temperature of the polarization rotation liquid crystal cell, wherein the measurement means is a polarization rotation liquid crystal cell. When the amount of change in temperature of the polarization rotation liquid crystal cell from the previous determination of the polarization property reaches a predetermined value, the polarization property of the polarization rotation liquid crystal cell is newly determined.

  A pixel shifting unit according to a sixteenth aspect of the invention is the pixel shifting unit according to the second aspect of the invention, wherein the measuring means obtains the polarization characteristics of the polarization rotation liquid crystal cell each time the pixel shifting unit is activated. .

  An image display device according to a seventeenth invention is the image display device according to the third invention, wherein a plurality of video signals can be selectively switched and input, and image information corresponding to the input video signals is obtained. A signal input means for outputting is further provided, and the measurement means obtains the polarization characteristics of the polarization rotation liquid crystal cell each time the system of the video signal input to the signal input means is switched.

  An image display device according to an eighteenth aspect of the present invention is the image display device according to the third aspect of the present invention, wherein a pre-correction vector is constructed using a signal at each pixel position of wobbling in the pre-correction image information as a component. When the corrected vector is configured using the signal at each pixel position of wobbling as a component, the image information correction calculation means calculates an inverse matrix of the matrix using the polarization characteristic as a correction parameter for the image information correction calculation, A vector after correction is calculated by performing a matrix operation on the correction parameter to the vector before correction to correct the image information.

  A sensor unit according to a nineteenth aspect of the invention is the sensor unit according to the first aspect of the invention, further comprising a non-volatile storage means for storing the polarization characteristic obtained by the measurement means.

  An image display device according to a twentieth aspect of the present invention is the image display device according to the eighteenth aspect of the invention, wherein the non-volatile storage means for storing the inverse matrix of the matrix using the polarization characteristic obtained by the image information correction calculation means Is further provided.

  An image display device according to a twenty-first aspect of the invention is the image display device according to the third aspect of the invention, which displays a color image, and the measuring means displays the polarization characteristics of the polarization-rotating liquid crystal cell and the color image. It is obtained for each color to be configured, and the image information correction calculation means corrects the image information for each color.

  An image display device according to a twenty-second aspect of the invention is the image display device according to the twenty-first aspect of the invention, which displays a color image in color plane order.

  An image display apparatus according to a twenty-third aspect of the invention is the image display apparatus according to the twenty-first aspect of the invention, which displays a color image by a multi-panel display method having an independent optical path for each color constituting the color image.

  An image display device according to a twenty-fourth aspect of the invention is the image display device according to the third aspect of the invention, further comprising power supply control means for turning on / off the power supply to the image information correction calculation means, the power supply control means. If the polarization characteristic obtained by the measuring means is within a predetermined range, the power supply to the image information correction calculating means is turned off.

  An image display apparatus according to a twenty-fifth aspect of the present invention is the image display apparatus according to the third aspect of the present invention, wherein the display optical means includes a zoom optical system, and the power to the image information correction calculation means is Power supply control means for turning on / off the supply is further provided, and the power supply control means supplies power to the image information correction calculation means when the zoom magnification of the display optical means is less than a predetermined value. It is to turn off.

  An image display device according to a twenty-sixth aspect of the invention is the image display device according to the third aspect of the invention, wherein the display optical means includes a focus optical system for adjusting a focal position. Power supply control means for turning on / off power supply to the information correction calculation means is further provided, and the power supply control means is configured to correct the image information correction when the focal position of the display optical means is closer than a predetermined position. The power supply to the computing means is turned off.

  An image display device according to a twenty-seventh aspect is the image display device according to the third aspect, wherein the display optical means includes a zoom optical system and a focus optical system for adjusting a focal position. And further comprising power control means for turning on / off the power supply to the image information correction calculation means, wherein the power control means has a polarization characteristic determined by the measurement means within a predetermined range, In addition, when the zoom magnification of the display optical means is less than a predetermined value and the focal position of the display optical means is closer than the predetermined position, the power supply to the image information correction calculation means is turned off.

  According to the sensor unit, the pixel shifting unit, and the image display device of the present invention, noise such as unevenness due to temperature change and aging change, pseudo contour, and false color can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIGS. 1 to 21 show Embodiment 1 of the present invention, and FIG. 1 is a diagram showing an outline of a configuration mainly related to an optical system of an image display apparatus.

  As shown in FIG. 1, the image display apparatus includes a projector 1 and a screen 2 that is a part of display optical means on which an image is projected from the projector 1. In the present embodiment, a projector type device will be described as an example of the image display device. However, the present invention is not limited to this.

  The projector 1 includes an illumination unit 5, a display unit 21, a pixel shift unit 6, and a display optical unit 7.

  Among these, the illuminating unit 5 is a part of image modulation means configured to include a display light source 11, a color wheel 12, a PS conversion element 13, an integrator rod 14, and an illumination optical system 15. It is.

  The display light source 11 includes, for example, a light source unit 11a that emits white light by discharge from an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, and the like, and a light beam emitted from the light source unit 11a for condensing light at a predetermined point. And an elliptical reflector 11b. In addition, although the discharge lamp which light-emits by discharge is mentioned as an example here as the light source part 11a, it is not restricted to this, For example, various light emission means, such as LED and a halogen lamp, can be used as the light source part 11a. It is.

  The color wheel 12 is for extracting color components of light emitted from the light source 11 for display in time series. For example, the R filter 12r, G (green) that can transmit only the wavelength of R (red). The three color filters of the G filter 12g that can transmit only the wavelength of B) and the B filter 12b that can transmit only the wavelength of B (blue) (see also FIG. 7) are arranged on the disc at equal intervals in the circumferential direction. The disk is configured to be rotated by a driving means such as a motor. As a result, the color wheel 12 sequentially generates three color lights of RGB in a time division manner.

  The PS conversion element 13 is a device for efficiently converting light that has passed through the color wheel 12 into light having a specific polarization direction.

  The integrator rod 14 is for converting the luminous points of the light source into multi-points using internal reflection, thereby eliminating unevenness of light from the PS conversion element 13 and converting it into uniform illumination light.

  The illumination optical system 15 is an optical system for efficiently projecting illumination light emitted from the integrator rod 14 onto the display unit 21.

  The display unit 21 is a part of image modulation means configured by, for example, a transmissive LCD. Since this image display device is a color image display device that employs the single-plate color plane sequential display method using the color wheel 12 as described above, the transmissive LCD used in the display unit 21 is a so-called monochrome type. This is a transmissive LCD. The transmissive LCD is configured such that the direction of the polarization transmission axis coincides with the polarization direction of the illumination light converted by the PS conversion element 13 of the illumination unit 5.

  The display unit 21 is controlled by a display control unit 29 provided in the projector 1.

  In the example shown in FIG. 1, the pixel shifting unit 6 includes a first polarization rotation liquid crystal cell 22, a first birefringence plate 23, a second polarization rotation liquid crystal cell 24, and a second birefringence plate 25. Are arranged in order on the optical path from the display unit 21 to the display optical unit 7. A first set of the first polarization-rotating liquid crystal cell 22 and the first birefringent plate 23, and a second set of the second polarization-rotating liquid crystal cell 24 and the second birefringent plate 25; One of these constitutes, for example, a pixel shifting unit that shifts the light beam in the horizontal direction, and the other constitutes, for example, a pixel shifting unit that shifts the light beam in the vertical direction, so that so-called four-point wobbling can be performed. It has become.

  Further, the pixel shifting unit 6 is provided with a cylindrical light shielding member 28 for preventing the light related to the display light beam from leaking on the outer peripheral side of the optical path from the display unit 21 to the display optical unit 7.

  The above-described first polarization rotation liquid crystal cell 22 includes a portion projecting to the outer peripheral side of the light shielding member 28, and a display region 22a for allowing a display light beam to pass through the inner peripheral side surrounded by the light shielding member 28 includes: Detection regions 22b are respectively provided in portions protruding to the outer peripheral side of the light shielding member 28 (see FIG. 2 and the like). And the 1st sensor unit 26 for detecting the polarization state of this 1st polarization rotation liquid crystal cell 22 as needed is arranged so that the detection area 22b of this projection part may be inserted.

  Similarly, the second polarization rotation liquid crystal cell 24 described above includes a portion that protrudes to the outer peripheral side of the light shielding member 28, and a display region for allowing a display light beam to pass through the inner peripheral side surrounded by the light shielding member 28. Detection areas 24b are provided in the portions 24a projecting to the outer peripheral side of the light shielding member 28 (see FIG. 2, etc.). And the 2nd sensor unit 27 for detecting the polarization state of this 2nd polarization rotation liquid crystal cell 24 as needed is arrange | positioned so that the detection area 24b of this protrusion part may be pinched | interposed.

  Therefore, in the present embodiment, the characteristics of the polarization swirl liquid crystal cell are not estimated by monitoring the temperature as described in Japanese Patent Laid-Open No. 11-326877, but the characteristics of the polarization swirl liquid crystal cell are directly measured. It is supposed to be detected.

  The display optical unit 7 includes a projection optical system 31, a zoom / focus drive mechanism 32, and a zoom / focus position information detection unit 33.

  The projection optical system 31 is a display optical means configured as a zoom optical system that includes a focus optical system and can adjust a focal position (focus position) and can adjust a focal distance (zoom position).

  The zoom / focus drive mechanism 32 is for performing the focus position adjustment and zoom adjustment of the projection optical system 31.

  The zoom / focus position information detection unit 33 is for outputting focus position information and zoom information set by the zoom / focus drive mechanism 32 to a system control microcomputer 51 (see FIG. 2, FIG. 8, etc.) described later. It is.

  An image is enlarged and projected on the screen 2 from the projector 1 having such a configuration, so that the image on the screen 2 can be observed. FIG. 1 shows a state in which a conjugate image of the display unit 21 is projected on the screen 2 and can be observed.

  Next, FIG. 2 is a diagram showing a basic configuration of the sensor units 26 and 27. Since the first sensor unit 26 and the second sensor unit 27 are basically configured in the same manner, they will be described together here.

  In the sensor units 26 and 27, the measurement light source 41 and the polarizing plate 42 are disposed on one side of the polarization rotation liquid crystal cells 22 and 24, and the polarizing plate 43, the color filter 45, and the light receiving element 44 are disposed on the other side. To be arranged on the optical axis directed from the light receiving element 44 to the light receiving element 44. In the example shown in FIG. 2, for example, the measurement light source 41 is on the illumination unit 5 side of the polarization rotation liquid crystal cells 22 and 24, and the light receiving element 44 is on the screen 2 side of the polarization rotation liquid crystal cells 22 and 24, respectively. Although arranged, it is also possible to arrange the opposite.

  The measurement light source 41 is composed of, for example, a white LED or the like, and always emits light based on the control of the light source light emission circuit 53 when the sensor units 26 and 27 perform measurement. The light source light emission circuit 53 performs voltage generation, current control, and the like for causing the measurement light source 41 to emit light.

  The polarizing plate 42 is a first polarizing means that passes only light in one polarization direction among the light beams emitted from the measurement light source 41 and does not pass light in other polarization directions orthogonal to the one polarization direction. . The polarized light beam that has passed through the polarizing plate 42 passes through the polarization rotation liquid crystal cells 22 and 24 for pixel shifting, which is a measurement object. The polarizing plate 43 is a second polarizing means that allows only light in the polarization direction to be measured out of the light that has passed through the polarization rotation liquid crystal cells 22 and 24 to pass. In the example shown in FIG. 2, the polarizing plate 42 and the polarizing plate 43 are arranged so that the polarization transmission axes 42a and 43a are in the same direction (that is, parallel Nicols).

  The color filter 45 is an array of color filters (R color filter 45r, G color filter 45g, and B color filter 45b) having the same optical characteristics as the color wheel 12 described above. Which one of these color filters is arranged on the optical axis from the measurement light source 41 to the light receiving element 44 can be selectively switched by the color filter position control mechanism 46. Here, in the example shown in FIG. 2, the color filter position control mechanism 46 includes a rack 46 a that is integrally provided on the lower side of the color filter 45, and a motor 46 b that meshes with the rack 46 a. , And is configured. Here, the color filter 45 and the color filter position control mechanism 46 are provided in order to explain an example of the sensor units 26 and 27 incorporated in the color image display device. However, in the case of a monochrome image display device, these are provided. Is no longer necessary.

  The light intensity of the polarized light passing through the polarizing plate 43 described above varies depending on the driving state of the polarization rotation liquid crystal cells 22 and 24. The light receiving element 44 is a light receiving unit that receives the polarized light passing through the polarizing plate 43 by the light receiving unit 44a and outputs a change in the amount of received light as a waveform.

  The light quantity measurement output signal from the light receiving element 44 is converted to a digital signal via an A / D converter (not shown) and the like, and then output to the system control microcomputer 51 serving as measurement means.

  Further, in the vicinity of the polarization rotation liquid crystal cells 22 and 24, a temperature detection device 55 serving as a temperature detection means for measuring the temperature of the polarization rotation liquid crystal cells 22 and 24 is arranged as required for control. It has become. The temperature measurement output signal from the temperature detection device 55 is also converted to a digital signal and then output to the system control microcomputer 51.

  The system control microcomputer 51 controls the liquid crystal cell driving circuit 54 to drive the polarization rotation liquid crystal cells 22 and 24. The system control microcomputer 51 grasps the temporal relationship of the light reception waveform of the light receiving element 44 with respect to the drive waveform of the liquid crystal cell drive circuit 54. Then, the system control microcomputer 51 calculates a correction parameter to be set in the correction calculation block 52 as image information correction calculation means based on the drive waveform and the received light waveform for the same time. At this time, the system control microcomputer 51 determines the correction parameter in consideration of the temperature information from the temperature detection device 55 as necessary.

  The correction calculation block 52 corrects the image information based on the calculated correction parameter so as to obtain an optimum polarization characteristic, and performs frame sequential for pixel shifting as will be described later.

  The display control unit 29 converts the signal output from the correction calculation block 52 into a signal format suitable for display, and outputs the signal format to the display unit 21. Thus, the corrected image is displayed on the display unit 21.

  The corrected image information is output to the display control unit 29 and displayed on the display unit 21.

  The system control microcomputer 51 is provided with a lighting control circuit 51a for instructing the light source light emitting circuit 53 to turn on / off the light source and controlling the lighting by the light source light emitting circuit 53.

  The first pixel shifting unit 20 includes a pixel shifting unit including a polarization rotation liquid crystal cell 22 and a birefringent plate 23, a sensor unit 26 disposed so as to sandwich the polarization rotation liquid crystal cell 22, and, if necessary. And a temperature detecting device 55 provided.

  Similarly, the second pixel shifting unit 20 includes a pixel shifting unit including the polarization rotation liquid crystal cell 24 and the birefringent plate 25, a sensor unit 27 disposed so as to sandwich the polarization rotation liquid crystal cell 24, and, if necessary. And a temperature detecting device 55 disposed in the same manner.

  Next, FIG. 3 is a diagram for explaining the effect of performing a four-point pixel shift by performing a light ray shift by the pixel shift unit.

  The pixel shifting unit 6 of the present embodiment combines the on / off of the voltage applied to the first polarization rotation liquid crystal cell 22 and the second polarization rotation liquid crystal cell 24 to thereby obtain the pixel position A, the pixel position B, The pixel position is shifted to four points of pixel position C and pixel position D. Here, the polarization rotation liquid crystal cells 22 and 24 do not rotate the polarization direction when turned on, and rotate the polarization direction by 90 ° when turned off.

  First, FIG. 3A shows a case where the light beam from the display unit 21 goes straight and does not shift and reaches the pixel position A. This state is achieved by turning off the applied voltage of the first polarization rotation liquid crystal cell 22 and turning off the application voltage of the second polarization rotation liquid crystal cell 24. At this time, the polarized light (S-polarized light) having the polarization transmission axis in the vertical direction from the display unit 21 is rotated by 90 ° by the first polarization rotation liquid crystal cell 22 in the off state, and the polarization transmission axis in the horizontal direction. Is converted to polarized light (P-polarized light). The P-polarized light passes through the first birefringent plate 23 as it is. This P-polarized light is converted into S-polarized light by the second polarization rotation liquid crystal cell 24 in the off state. The S-polarized light passes through the second birefringent plate 25 as it is. In this way, the pixel position A is achieved.

  Next, FIG. 3C shows a case where the light beam from the display unit 21 is shifted rightward and reaches the pixel position C. This state is achieved by turning off the applied voltage of the first polarization rotation liquid crystal cell 22 and turning on the application voltage of the second polarization rotation liquid crystal cell 24. In this case, it is the same as the case shown in FIG. 3A until the light beam from the display unit 21 passes through the first birefringent plate 23. The P-polarized light from the first birefringent plate 23 passes through the P-polarized light as it is without changing the polarization state by the second polarization rotation liquid crystal cell 24 in the on state. This P-polarized light is shifted rightward by the second birefringent plate 25. In this way, the pixel position C is achieved.

  Next, FIG. 3B shows a case where the light beam from the display unit 21 is shifted downward and reaches the pixel position B. This state is achieved by turning on the applied voltage of the first polarization rotation liquid crystal cell 22 and turning on the application voltage of the second polarization rotation liquid crystal cell 24. In this case, the S-polarized light from the display unit 21 passes through the first polarization rotation liquid crystal cell 22 in the on state as it is without changing the polarization state. The S-polarized light is shifted downward by the first birefringent plate 23. The S-polarized light passes through the second polarization-rotating liquid crystal cell 24 in the on state as it is without changing the polarization state. The S-polarized light passes through the second birefringent plate 25 as it is. In this way, the pixel position B is achieved.

  FIG. 3D shows a case where the light beam from the display unit 21 is shifted in the lower right direction and reaches the pixel position D. This state is achieved by turning on the applied voltage of the first polarization rotation liquid crystal cell 22 and turning off the application voltage of the second polarization rotation liquid crystal cell 24. In this case, the process is the same as that shown in FIG. 3B until the light beam from the display unit 21 is shifted downward by the first birefringent plate 23. S-polarized light from the first birefringent plate 23 is rotated by 90 ° by the second polarization-rotating liquid crystal cell 24 in the off state, and converted to P-polarized light. This P-polarized light is shifted rightward by the second birefringent plate 25. In this way, the pixel position D is achieved.

  Next, FIG. 4 is a pixel shift timing chart in the color image display device of the single-plate color plane sequential display method.

  The frame period for displaying one color image is, for example, 30 Hz. Within one frame, three colors of R, G, and B are displayed in a time-sharing manner, and the period (referred to as a color frame period) is 90 Hz. Since a four-point pixel shift from pixel position A to pixel position D is performed within one color frame, the period used to display one pixel position (referred to as a subframe period) is 360 Hz. In addition, since the subframe indicating one state period of pixel shift is determined based on the drive limit frequency of the display unit 21 and the response characteristics of the polarization swivel liquid crystal cells 22 and 24, 360 Hz shown in the figure is It is an example.

  In one color frame, the first polarization rotation liquid crystal cell 22 is turned off and the second polarization rotation liquid crystal cell 24 is turned off in the first subframe, and the first polarization rotation liquid crystal cell 22 is turned off in the second subframe. In addition, the second polarization rotation liquid crystal cell 24 is on, the first polarization rotation liquid crystal cell 22 is on and the second polarization rotation liquid crystal cell 24 is on in the third subframe, and the first polarization rotation liquid crystal is in the first subframe. It is driven so that the cell 22 is turned on and the second polarization rotation liquid crystal cell 24 is turned off. Therefore, the pixel position changes in the order of A → C → B → D for each color (see also FIG. 3).

  Subsequently, several configuration examples of the sensor unit will be described with reference to FIGS. The examples shown in FIGS. 5 to 7 are configuration examples for detecting both originally intended light in the polarization direction and unintended light perpendicular to the polarization direction.

  First, FIG. 5 shows a configuration example in which three polarizing plates, two light sources for measurement, and two light receiving elements are fixedly arranged in parallel Nicols and crossed Nicols for each polarization rotating liquid crystal cell 22, 24. FIG.

  As described above, the display unit 21, the first polarization rotation liquid crystal cell 22, the first birefringence plate 23, the second polarization rotation liquid crystal cell 24, and the second birefringence plate 25 are sequentially arranged on the optical path. Has been.

  Among these, the 1st polarization rotation liquid crystal cell 22 is provided with the area | region 22b for a detection so that it may protrude to the side from the area | region 22a for a display. Two measurement light sources 41A1 and 41A2 and one polarized light are provided on one side of the detection region 22b (in the illustrated example, the display unit 21 side) so as to be parallel to the optical path of the display light beam through the detection region 22b. The plate 42A is provided with two polarizing plates 43Ap and 43As and two light receiving elements 44A1 and 44A2 as light receiving means on the other side (the first birefringent plate 23 side in the illustrated example).

  The polarizing plate 42A allows only light in one polarization direction out of the light emitted from the measurement light sources 41A1 and 41A2 to pass. For example, the polarizing plate 42A serves as a first polarizing means that allows only P-polarized light to pass. .

  The polarizing plate 43Ap is the second polarizing means (parallel Nicols) disposed so as to have the polarization transmission axis in the same direction as the polarizing plate 42A. In the above-described example, only the P-polarized light is transmitted. It has become. The polarization rotation liquid crystal cell 22 rotates the polarization state by 90 ° when it is off as described above. Therefore, the light that attempts to pass through the two polarizing plates 42A and 43Ap arranged in parallel Nicols is normally shielded when the polarization rotation liquid crystal cell 22 is off (as will be described in detail later, elliptically polarized light). (Because of the light, it is not strictly shielded.) Thus, the parallel Nicols are arranged to measure a normally black (NB) state.

  On the other hand, the polarizing plate 43As is a second polarizing means (crossed nicols) arranged so as to have a polarization transmission axis in a direction orthogonal to the polarizing plate 42A. In the above-described example, only the S-polarized light is transmitted. It has become. Therefore, the light that attempts to pass through the two polarizing plates 42A and 43As arranged in crossed Nicol normally passes as it is when the polarization rotation liquid crystal cell 22 is off (as described above, it is converted into elliptically polarized light. Therefore, strictly speaking, a part of the light is shielded.) Thus, the crossed Nicols are arranged to measure a normally white (NW) state.

  In this way, the light emitted from the measurement light source 41A1 is received by the light receiving element 44A1 through the two polarizing plates 42A and 43Ap arranged in parallel Nicols (the first light source 41A1). Optical path of measurement light). The light emitted from the measurement light source 41A2 is received by the light receiving element 44A2 via the two polarizing plates 42A and 43As arranged in crossed Nicols (the second measurement light Light path). Thus, the measurement light source and the light receiving element are fixedly provided independently for each polarization direction.

  Further, a color filter 45A is interposed, for example, between the polarizing plate 42A and the detection region 22b on the optical path from each measurement light source 41A1, 41A2 to the detection region 22b of the first polarization rotation liquid crystal cell 22. It is supposed to be. The color filter 45A is configured by arranging, for example, an R color filter 45Ar, a G color filter 45Ag, and a B color filter 45Ab in the vertical direction, and any one of the color filters is arranged on the optical paths of the two measurement lights described above. It is controlled by the color filter position control mechanism 46A. Similar to the color filter position control mechanism 46 described above, the color filter position control mechanism 46A includes, for example, a rack 46Aa and a motor 46Ab.

  Further, the second polarization rotation liquid crystal cell 24 includes a detection region 24b so as to protrude downward from the display region 24a. Two measurement light sources (not shown) and one first polarization means are provided on one side (display unit 21 side) of the detection region 24b so as to be parallel to the optical path of the display light beam through the detection region 24b. The polarizing plate 42B has two polarizing plates 43Bp and 43Bs as the second polarizing means and two light receiving elements 44B1 and 44B2 as the light receiving means on the other side (the second birefringent plate 25 side in the illustrated example). It is arranged.

  In the same manner as described above, the polarizing plate 42B and the polarizing plate 43Bp are parallel Nicols (for example, both pass only P-polarized light), and the polarizing plates 42B and 43Bs are crossed Nicols (for example, polarizing plates). 43Bs is disposed so that only S-polarized light passes through.

  Further, a color filter 45B is inserted between, for example, the polarizing plate 42B and the detection region 24b on the optical path from each measurement light source to the detection region 24b of the second polarization rotation liquid crystal cell 24. It has become. The color filter 45B is configured by arranging, for example, an R color filter 45Br, a G color filter 45Bg, and a B color filter 45Bb in the left-right direction, and any one of the color filters is disposed on the optical paths of the two measurement lights. In this manner, the color filter position control mechanism 46B is controlled. Similarly to the color filter position control mechanism 46A described above, the color filter position control mechanism 46B includes, for example, a rack 46Ba and a motor 46Bb.

  According to the configuration shown in FIG. 5, when it becomes necessary to measure the polarization characteristics of the polarization rotation liquid crystal cell, the measurement can be immediately performed. Accordingly, it is possible to quickly change the processing parameter for removing noise such as false color due to the polarization characteristic, and it is possible to always display a high-quality image.

  Next, FIG. 6 shows three polarizing plates, one light source for measurement, and one light receiving element for each polarization swivel liquid crystal cell 22, 24 so that parallel Nicols and crossed Nicols can be switched in a time division manner. It is a perspective view which shows the structural example which has arrange | positioned. In FIG. 6, the description of the same parts as those in FIG.

  In the configuration shown in FIG. 6, the measurement light source 41A2 and the light receiving element 44A2 are omitted from the configuration shown in FIG. Correspondingly, the polarizing plate 42A is also changed from a vertically long rectangle as shown in FIG. 5 to a substantially square shape.

  The polarizing plates 43Ap and 43As are integrally assembled to the frame member 47Aa. These polarizing plates 43Ap and 43As are configured to be movable in, for example, the vertical direction in FIG. 6 by the first polarizing plate position control mechanism 47A serving as switching means, and between the measurement light source 41A1 and the light receiving element 44A1. It can be inserted alternatively on the optical path between them. The first polarizing plate position control mechanism 47A includes, for example, a rack 47Ab provided on the edge of the frame member 47Aa and a motor 47Ac.

  Next, the second sensor unit 27 for measuring the polarization characteristics of the second polarization rotation liquid crystal cell 24 also uses the first sensor for measuring the polarization characteristics of the first polarization rotation liquid crystal cell 22 as described above. Similar to the sensor unit 26, one of the two measurement light sources is omitted, and the corresponding light receiving element 44B2 is also omitted. Then, the polarizing plate 42B is changed to a substantially square shape, and the polarizing plates 43Bp and 43Bs are integrally assembled to the frame member 47Ba, and the second polarizing plate position control mechanism 47B serving as switching means, for example, in the horizontal direction. It is possible to move to. The second polarizing plate position control mechanism 47B also includes, for example, a rack 47Bb provided on the edge of the frame member 47Ba and a motor 47Bc, as in the first polarizing plate position control mechanism 47A. It consists of

  According to the configuration shown in FIG. 6, normally black measurement and normally white measurement cannot be performed simultaneously, but can be performed in time division. And by adopting such a configuration, it is possible to perform normally black measurement and normally white measurement only by using one set of measurement light source and light receiving element. The characteristics of the light receiving element are the same in both the normally black measurement and the normally white measurement, so that correction of measurement data is unnecessary, and the configuration can be simplified and the manufacturing cost can be reduced.

  In the configuration shown in FIG. 6, the arrangement of the polarization means is switched between two states of a crossed Nicol state and a parallel Nicol state by moving and switching the positions of the two polarizing plates. For example, one polarizing plate may be rotated by 90 °.

  Next, in FIG. 7, a polarizing plate and a light receiving element for performing normally black measurement and normally white measurement are arranged to be able to enter and exit in the optical path through which the display light beam passes in the pixel shifting unit 6. It is a perspective view which shows the example of a structure.

  The sensor unit shown in FIG. 7 includes two light receiving elements 44A and 44B as light receiving means, and polarizing plates 43p and 43s as second polarizing means are arranged in front of the light paths of these light receiving elements 44A and 44B, respectively. It is installed. Then, the sensor unit position control mechanism 48 as a moving means can integrally move the light receiving elements 44A and 44B and the polarizing plates 43p and 43s into and out of an optical path through which the display light beam passes. Here, the sensor unit position control mechanism 48 includes, for example, a rack 48a and a motor 48b. The sensor unit is configured to be able to enter and exit immediately after the second birefringent plate 25 is on the optical path.

  In such a configuration, the measurement light source and the measurement color filter as shown in FIGS. 5 and 6 are not provided, and the display light source 11 and the color wheel 12 are used instead. ing. Further, the function of the first polarizing plate 42 (first polarizing means) is also served by the illumination unit 5 and the display unit 21 which are image modulation means.

  Further, when measuring the polarization characteristics using the configuration as shown in FIG. 7, uniform image information in which all pixels have the maximum white level is input to the display unit 21. ing.

  In such a configuration, since measurement cannot be performed while displaying a normal image, the measurement is performed when a normal image is not displayed, for example, when the image display apparatus is activated or terminated. In this configuration, the measurement of the first polarization rotation liquid crystal cell 22 and the measurement of the second polarization rotation liquid crystal cell 24 are simultaneously performed in a state where they are superimposed in the optical path direction. Alternatively, two sets of sensor units having the above-described configuration are provided, with one set immediately after the optical path of the first polarization rotation liquid crystal cell 22 and the other set immediately after the optical path of the second polarization rotation liquid crystal cell 24. These may be provided so as to be able to enter and exit, and more accurate measurement may be performed.

  According to the configuration as shown in FIG. 7, since the measurement light source and the measurement color filter are not required, the configuration can be simplified.

  Next, FIG. 8 is a block diagram mainly showing an electrical configuration of the image display apparatus.

  As described above, the image display device includes the measurement light source 41, the polarizing plate 42, the color filters 45r, 45g, and 45b, the polarization-rotating liquid crystal cells 22 and 24, the polarizing plate 43, and the light reception. Element 44, color filter position control mechanism 46, temperature detection device 55, system control microcomputer 51, correction calculation block 52, light source light emission circuit 53, polarizing plate polarization direction control unit 47, power switch 56, The polarization characteristic correction processing power source 57, the frame sequential timing control circuit 58, the pixel shift plane sequentializing unit 59, the liquid crystal cell driving circuit 54, the display control unit 29, the display unit 21, and the image switching operation button 61. The first video input terminal 62a, the second video input terminal 62b, the third video input terminal 62c, the first signal detection circuit 63a, the second signal detection circuit 63b, and the third signal detection. And circuit 63c, an input selection switch 64, and a zoom / focus position information detecting unit 33, a.

  The system control microcomputer 51 includes a lighting control circuit 51a, a temperature register 51b, a polarization characteristic calculation unit 51c, a correction processing parameter calculation unit 51d, a parameter storage unit 51e, a video switching control circuit 51f, and a color filter position control. Circuit 51g.

  The correction calculation block 52 includes a polarization characteristic calculation unit 51c, a correction processing parameter calculation unit 51d, a parameter storage unit 51e, a polarization characteristic correction processing unit 52a, and an output selection switch 52b in the system control microcomputer 51 described above. have.

  In such a configuration, the system control microcomputer 51 outputs a position control signal from the color filter position control circuit 51g to the color filter position control mechanism 46, and any of the R color filter 45r, the G color filter 45g, and the B color filter 45b. These are arranged on the optical axis from the measurement light source 41 to the light receiving element 44. The following processing is performed for all of the color filters 45r, 45g, and 45b by sequentially changing the R color filter 45r, the G color filter 45g, and the B color filter 45b arranged on the optical axis.

  Then, the system control microcomputer 51 gives a lighting signal to the light source light emitting circuit 53 by the lighting control circuit 51a. Then, the light source light emitting circuit 53 performs voltage generation, current control, and the like for causing the measurement light source 41 to emit light, and drives the measurement light source 41.

  The light emitted from the measurement light source 41 is adjusted to one linearly polarized state (for example, P-polarized state) by the polarizing plate 42 and then passes through one of the color filters 45r, 45g, and 45b to be polarized swirl liquid crystal. The light enters the cells 22 and 24.

  The frame sequential timing control circuit 58 receives the polarization rotation control signal from the system control microcomputer 51 and controls the polarization state of the polarization rotation liquid crystal cells 22 and 24 via the liquid crystal cell drive circuit 54. At the time of image display, this shifts the pixels and switches the display position of the pixels. The same applies when performing measurement in real time with image display.

  On the other hand, when only the measurement is performed without displaying an image, the system control microcomputer 51 changes the polarization rotation control signal supplied to the frame sequential timing control circuit 58 to a special measurement polarization rotation control signal. In addition, the polarization state of the polarization rotation liquid crystal cells 22 and 24 is forcibly controlled and fixed.

  The polarized light that has passed through the polarization rotating liquid crystal cells 22 and 24 is generally elliptically polarized light as will be described later. By passing this elliptically polarized light through the polarizing plate 43 for measurement, only linearly polarized light in one direction is allowed to pass. For example, in the case of the configuration shown in FIGS. 5 and 7 described above, the polarization direction of the polarizing plate 43 can be switched by selecting the output of the light receiving element. For example, in the case of the configuration shown in FIG. 6 described above, the polarization direction of the polarizing plate 43 can be switched using the polarizing plate position control mechanisms 47A, 47B and the like.

  The system control microcomputer 51 receives the light quantity measurement output signal from the light receiving element 44 and calculates the polarization characteristic by the polarization characteristic calculation unit 51c. When calculating the polarization characteristics, the polarization characteristic calculation unit 51c uses the polarization direction information output from the polarizing plate polarization direction control unit 47 serving as switching means, and triggers the lighting information output from the light source light emitting circuit 53. It is supposed to be.

  The system control microcomputer 51 further calculates a correction parameter to be set in the correction calculation block 52 by the correction processing parameter calculation unit 51d based on this polarization characteristic. At this time, as described above, the correction parameter may be determined in consideration of the temperature information stored in the temperature register 51b based on the temperature measurement output signal output from the temperature detection device 55 as needed.

  The correction parameters calculated by the correction processing parameter calculation unit 51d are stored in a parameter storage unit 51e configured as a non-volatile memory (nonvolatile storage unit), and a matrix calculation coefficient (about this) of the polarization characteristic correction processing unit 52a. Is used later.)

  Here, although the correction parameter is stored in the parameter storage unit 51e, the polarization characteristic calculated by the polarization characteristic calculation unit 51c may be stored.

  On the other hand, in this image display device, a plurality of (for example, three) video input terminals constituting the signal input means are, as described above, the first video input terminal 62a, the second video input terminal 62b, and the third video input. An external video source is connected to each of the video input terminals 62a, 62b, and 62c so that a video signal can be input. Each of these video input terminals 62a, 62b, and 62c is connected to an input selection switch 64 that constitutes a signal input means.

  The first video input terminal 62a is connected to the first signal detection circuit 63a, the second video input terminal 62b is connected to the second signal detection circuit 63b, and the third video input terminal 62c is connected to the third signal detection circuit 63c. Therefore, it is detected whether there is an input of a valid video signal.

  The first signal detection circuit 63a, the second signal detection circuit 63b, and the third signal detection circuit 63c constituting the signal input means are connected to the video switching control circuit 51f in the system control microcomputer 51, respectively.

  This image display device is further provided with a video switching operation button 61 so that it can be selected which of the video input terminals 62a, 62b, 62c described above is to be displayed. It is configured. The output of the video switching operation button 61 is connected to the video switching control circuit 51f described above.

  The video switching control circuit 51 f is further connected to the input selection switch 64. Then, in accordance with an operation input from the video switching operation button 61, a video signal from the first video input terminal 62a, a video signal from the second video input terminal 62b, and a video signal from the third video input terminal 62c Which one is used for display is switched. However, when the signal detection circuits 63a, 63b, and 63c detect that the video signal is not input from the video input terminal designated by the input selection switch 64 and the terminal is invalid, A warning display or the like is displayed, or an input terminal according to a predetermined priority order is automatically selected from video input terminals that have been detected to be valid.

  The video signal selected by the input selection switch 64 is input to the polarization characteristic correction processing unit 52a and the output selection switch 52b in the correction calculation block 52.

  The output selection switch 52b is configured to switch between the corrected image information from the polarization characteristic correction processing unit 52a and the uncorrected image information from the input selection switch 64 in response to a switching signal from the correction processing parameter calculation unit 51d. Which is output as image information for display is selected.

  That is, the correction processing parameter calculation unit 51d is obtained, for example, when the polarization property of the polarization rotation liquid crystal obtained by measurement is good enough not to require correction processing, or obtained from the zoom / focus position information detection unit 33. The image magnification based on the zoom information and the focal position (distance from the projection optical system 31 to the image plane of the screen 2) information is small, and the deterioration of the image based on the change in the polarization characteristic has a substantial effect on visual observation. In the case where it is not given, it is determined that the uncorrected image information is used as it is without performing the polarization characteristic correction process, and a switching signal to that effect is output to the output selection switch 52b.

  If the system control microcomputer 51 further determines not to perform the polarization characteristic correction process, the system control microcomputer 51 outputs a command to the polarization characteristic correction processing unit power source 57 serving as a power source control unit, and supplies power to the polarization characteristic correction processing unit 52a. The supply is turned off. This makes it possible to reduce power consumption. In addition, for example, a cooling fan attached to the arithmetic processing chip constituting the polarization characteristic correction processing unit 52a can be stopped, and noise reduction can be achieved. Furthermore, by reducing the power consumption of the power supply unit of the entire image display apparatus including the polarization characteristic correction processing power supply 57, the number of revolutions per unit time of the cooling fan of the power supply unit can be reduced, and the noise reduction can be achieved. It becomes possible to plan.

  As described above, the image data output from the output selection switch 52 b is time-axis converted by the pixel shifting surface sequentialization unit 59 in the correction calculation block 52. This time axis conversion will be described with reference to FIG. FIG. 12 is a diagram illustrating an example of a pixel array of image information.

  From the video input terminals 62a, 62b, and 62c described above, when there is image information as shown in FIG. In addition, reading is performed in the order of line units such as A11C11A12C12 ... B11D11B12D12 ... A21C21A22C22 ... B21D21B22D22 ... On the other hand, as shown in FIG. 4, the image display apparatus divides the pixel positions A, C, B, and D into four sub-frames within one color frame, thereby shifting the pixels. It is necessary to perform conversion according to the plane order. Therefore, the pixel shift plane sequentialization unit 59 displays each pixel data read out in the order as described above in a pixel shift plane sequential display such as A11A12... A21A22... C11C12... C21C22. It is to be converted into an order suitable for.

  The pixel shifted frame sequential image information thus converted is output from the pixel shifted frame sequential unit 59 to the display controller 29 based on the frame sequential timing control signal output from the frame sequential timing control circuit 58. It has become.

  The frame sequential timing control circuit 58 controls the frame sequential timing in accordance with the polarization rotation control signal output from the system control microcomputer 51. That is, the frame sequential timing control circuit 58 is connected to the liquid crystal cell drive circuit 54 and controls the output timing of the polarization rotation control signal output from the liquid crystal cell drive circuit 54 to the polarization rotation liquid crystal cells 22 and 24. It is like that. As a result, the drive timing of the polarization swivel liquid crystal cells 22 and 24 and the display timing of the frame sequential subframe (see FIG. 4) by the display unit 21 can be synchronized to perform pixel-shifted display. Yes.

  The pixel shift frame sequential image information output from the pixel shift plane sequentialization unit 59 is converted into a signal format suitable for input to the display unit 21 by the display control unit 29 and output. Thus, the display unit 21 converts the image data into display light. This display light is projected onto the screen 2 via the pixel shifting unit 6 and the display optical unit 7 as shown in FIG.

  Next, FIG. 9 is a diagram showing the driving waveform of the polarization rotation control signal and the waveform of the light quantity measurement output signal obtained from the light receiving element.

  As described above, the polarization rotation liquid crystal cells 22 and 24 basically rotate the polarization direction by 90 ° when off (low level: Lo) and rotate in the polarization direction when on (high level: Hi). It is configured not to perform.

  Therefore, the measurement result through two polarizing plates arranged in parallel Nicols is black when the polarization rotation liquid crystal cells 22 and 24 are off (because of the black level of normally black, the level is NB (denoted as NB (B)), and white when turned on (similarly, the level is denoted as NB (W)).

  On the other hand, the measurement result through two polarizing plates arranged in crossed Nicols is white (normally white white level when the polarization rotation liquid crystal cells 22 and 24 are off). NW (W).), When on, black (similarly, the level is described as NW (B)).

  However, since the polarization rotation liquid crystal cells 22 and 24 are generally not capable of completely rotating the polarization direction by 90 ° when the polarization rotation liquid crystal cells 22 and 24 are turned off, the polarization rotation liquid crystal cells 22 and 24 pass through the polarization rotation liquid crystal cells 22 and 24. The light is precisely elliptically polarized, and as shown in FIG. 9, NB (B) is not completely black and NW (W) is completely white (note that perfect white The luminance L is 1.0.)

  On the other hand, when the polarization rotation liquid crystal cells 22 and 24 are turned on, the polarization direction of the incident light may be considered to pass through the polarization direction as it is without changing almost completely. However, although it can be considered to be almost complete in principle, it is impossible to deny that there is a possibility that a slight error exists. Further, in the measurement system, two polarizing plates 42 and 43 that do not exist in the display system are used, but when the light output from these polarizing plates 42 and 43 becomes completely linearly polarized light (ideal linearly polarized light). Therefore, when these effects are taken into consideration, it is considered that NB (W) hardly reaches completely white and NW (B) slightly floats from completely black. The relative luminance in FIG. 9 indicates such deviation from perfect black and deviation from perfect white.

  Further, the polarization swivel liquid crystal cells 22 and 24 have a response time. When turned on, the response time is relatively short. When turned off, the response time is relatively long. , And can be read from the graph of relative luminance L.

  FIG. 10 is a diagram for explaining the deviation from the ideal linearly polarized light by the polarizing plate when the polarization swivel liquid crystal cells 22 and 24 are turned on. In FIG. 10, in order to clearly show the description contents in the drawing, it is exaggerated from the actual deviation.

  Here, it is assumed that complete P-polarized light is emitted when ideal linear polarization is performed. The (P, S) component of the vector VA in the PS plane of this ideal polarized light is (1, 0). On the other hand, when the polarized light by the polarizing plate is slightly elliptical polarized light deviating from the ideal linearly polarized light, there is a slight S component, and the components of the vector VB are (NB (W), NW). (B)) (however, this component has not been normalized). Accordingly, the normalized P component of this vector VB is ([NB (W) / {NB (W) + NW (B)}], 0), and the normalized S component is (0, [NW (B ) / {NB (W) + NW (B)}]).

  Next, FIG. 11 is a diagram for explaining that elliptically polarized light is generated when at least one of the two polarization rotation liquid crystal cells 22 and 24 is in an OFF state. In FIG. 11, in order to clearly show the description in the drawing, it is exaggerated from the actual elliptical polarization state.

  First, when both the first polarization swivel liquid crystal cell 22 and the second polarization swivel liquid crystal cell 24 are on, as described above, almost perfect P-polarized linearly polarized light is obtained (see FIG. As shown in FIG. 10, there is a possibility that a slight deviation may occur, but FIG. 11 shows a case where almost perfect P-polarized linearly polarized light is obtained. The (P, S) component of the vector V1 at this time is V1 = (NB (W), NW (B)).

  Next, when one of the first polarization rotation liquid crystal cell 22 and the second polarization rotation liquid crystal cell 24 is on and the other is off, the polarization direction is basically rotated by 90 °. Ideally, S-polarized light should be obtained. However, as described above, since the deviation due to the elliptically polarized light in the polarization rotation liquid crystal cell in the off state occurs, the P component remains in the vector V2 obtained at this time, and the component is V2 = ( NB (B), NW (W)). That is, the normalized P component of the vector V2 is ([NB (B) / {NW (W) + NB (B)}], 0), and the normalized S component is (0, [NW (W ) / {NW (W) + NB (B)}]).

  Similarly, when both the first polarization rotation liquid crystal cell 22 and the second polarization rotation liquid crystal cell 24 are turned off, the ideal 180 ° rotation of the polarization direction is not performed, as shown in the vector V3. Both the S component and the P component exist, the P component of the vector V3 is V3p, and the S component is V3s.

ここに、ＲＮＷ（Ｗ）はＮＷ測定白偏光比を、ＲＮＷ（Ｂ）はＮＷ測定黒偏光比を、ＲＮＢ（Ｂ）はＮＢ測定黒偏光比を、ＲＮＢ（Ｗ）はＮＢ測定白偏光比を、それぞれ示している。 Based on the light quantity measurement output signal obtained from the light receiving element 44, the polarization characteristic calculator 51c can measure such a deviation in the polarization direction. At this time, each polarization ratio as a polarization characteristic calculated by the polarization characteristic calculation unit 51c is expressed by the following Equation 1.
[Equation 1]

Here, RNW (W) is the NW measurement white polarization ratio, RNW (B) is the NW measurement black polarization ratio, RNB (B) is the NB measurement black polarization ratio, and RNB (W) is the NB measurement white polarization ratio. , Respectively.

  Each of these polarization ratios is calculated based on the light quantity measurement output signal measured for each color, and therefore exists independently for each color of RGB.

  The polarization characteristics can be calculated based on a single measurement value, but a plurality of measurements are performed to calculate a plurality of polarization characteristics, and an average value of the calculated plurality of polarization characteristics is defined as a polarization characteristic. Good. This is because measurement errors can be reduced.

When the error from the ideal linearly polarized light by the polarizing plate as shown in FIG. 10 can be almost ignored, approximation as shown in the first and second equations in the following equation 2 can be performed. Furthermore, when it can be assumed that there is almost no loss of light quantity due to the polarizing plate, approximation as shown in the third formula in the following formula 2 can be performed.
[Equation 2]
NW (B) ≒ 0
NB (W) ≒ 1
NB (B) + NW (W) ≒ 1

If such an approximate expression is used, Expression 1 can be rewritten as shown in Expression 3 below.
[Equation 3]
RNW (W) ≈1-R
RNW (B) ≒ 0
RNB (B) ≒ R
RNB (W) ≒ 1
Here, R is a polarization ratio, and the NB measurement black polarization ratio RNB (B) substantially corresponds to this.

  Therefore, if only the black level NB (B) in the parallel Nicol state is measured, each polarization ratio can be approximately calculated. This means that if it is sufficient to approximately calculate the polarization characteristics, it is not necessary to arrange the polarizing plates in both parallel and crossed Nicols, and only the arrangement of parallel Nicols is sufficient. When only the parallel Nicol arrangement is adopted, in addition to the black level NB (B) in the parallel Nicol state, the white level NB (W) in the parallel Nicol state is also measured without adding a configuration. Therefore, it is possible to calculate these ratios to obtain polarization characteristics.

  Next, FIG. 13 is a flowchart showing the basic operation of the polarization characteristic correction parameter calculation.

  When this process is started, first, polarization characteristics are detected (step S1). That is, any one of the color filters 45r, 45g, 45b, for example, the R color filter 45r, is arranged on the optical axis from the measurement light source 41 to the light receiving element 44, and the polarization direction of the polarization swivel liquid crystal cells 22, 24; The polarization characteristic calculation unit 51c calculates the polarization characteristics based on the light amount measurement output signal output from the light receiving element 44 while controlling the polarization directions of the polarizing plates 42 and 43 as necessary. The polarization characteristics calculated here are white level NW (W) for normally white measurement, black level NW (B) for normally white measurement, white level NB (W) for normally black measurement, and black for normally black measurement. Each value of level NB (B). Thereafter, the G color filter 45g and the B color filter 45b are also sequentially arranged on the optical axis from the measurement light source 41 to the light receiving element 44, and the same detection is performed.

  Subsequently, the correction processing parameter calculation unit 51d calculates a color mixture coefficient matrix for each of the R, G, and B colors based on the polarization characteristics calculated as described above (step S2).

  Here, the color mixture coefficient matrix will be described.

ここに、ｎは、２×２画素ブロックに順に付した番号で、時系列のフレーム番号を表している。具体的には、図１２に示した画素配置において、添え字「１１」の画素ブロックにｎ＝１を、添え字「１２」の画素ブロックにｎ＝２を、などのように順に付すことに相当している。 First, the color mixing coefficient matrix relating to the R color includes the input image information (INAR (n), INBR (n), INDR (n), INCR (n)), this image information is projected onto the screen 2, and the output image information obtained by measuring the projected image is (OUTAR (n), OUTBR (n), OUTDR (n)). , OUTCR (n)), it is defined as a transformation matrix KR (n) as shown in the following equation 4 between the input image information and the output image information.
[Equation 4]

Here, n is a number assigned in order to the 2 × 2 pixel block, and represents a time-series frame number. Specifically, in the pixel arrangement shown in FIG. 12, n = 1 is added to the pixel block with the subscript “11”, n = 2 is added to the pixel block with the subscript “12”, and so on. It corresponds.

  Each polarization ratio in the definition of the conversion matrix KR (n) in the second equation in Equation 4 is calculated as shown in Equation 1 based on the measurement result obtained from the light receiving element 44 through the R color filter. It has been done.

Similarly, the color mixture coefficient matrix relating to G color includes input image information (INAG (n), INBG (n)) to the pixel positions A, B, D, and C of the display unit 21 relating to the four-point pixel shift of G color. , INDG (n), INCG (n)), and this image information is projected onto the screen 2, and the output image information obtained by measuring the projected image is (OUTAG (n), OUTBG (n), OUTDG (n) ), OUTCG (n)), the input image information and the output image information are defined as a transformation matrix KG (n) as shown in Equation 5 below.
[Equation 5]

  However, each polarization ratio in the definition of the conversion matrix KG (n) in the second equation is calculated as shown in Equation 1 based on the measurement result obtained from the light receiving element 44 through the G color filter. Yes, the meaning of “n” is the same as in Equation 4.

Further, the color mixture coefficient matrix relating to the B color includes the input image information (INAB (n), INBB (n), INBB (n), INDB (n), INCB (n)), this image information is projected onto the screen 2, and the output image information obtained by measuring the projected image is (OUTAB (n), OUTBB (n), OUTDB (n)). , OUTCB (n)), it is defined as a transformation matrix KB (n) as shown in the following Equation 6 between input image information and output image information.
[Equation 6]

  However, each polarization ratio in the definition of the conversion matrix KB (n) in the second equation is calculated as shown in Equation 1 based on the measurement result obtained from the light receiving element 44 through the B color filter. Yes, the meaning of “n” is the same as Equation 4 and Equation 5.

  When the polarization swivel liquid crystal cells 22 and 24 have ideal polarization characteristics, the color mixing coefficient matrix relating to each of these colors becomes a unit matrix if the input image information and the output image information are normalized. It should be. However, as described above, since the polarization rotation liquid crystal cells 22 and 24 tend to be elliptically polarized light, the non-diagonal component is not zero, and information is mixed at each pixel position. Thus, if no measures are taken, the input image information, which is the originally intended image, is not displayed as it is, and an image with reduced quality due to pixel mixing is displayed. Accordingly, the corrected input image information obtained by multiplying the input image information by the inverse matrix of the color mixture coefficient matrix is replaced with the above-described input image information, whereby the output image information can be matched with the originally intended input image information. Basically possible (“Basically possible” means that the inverse matrix of the color mixture coefficient matrix does not exist or the inverse matrix of the color mixture coefficient matrix exists but the correction signal obtained using this inverse matrix is physically This is because it may be necessary to perform some kind of approximation such as a signal that is meaningless (for example, a signal that generates negative luminance).

［数８］

［数９］

That is, the inverse matrix CKR (n) as shown in Formula 7 as the inverse matrix of the matrix KR (n) shown in Formula 4 is shown in Formula 8 as the inverse matrix of the matrix KG (n) shown in Formula 5. As the inverse matrix CKG (n), the inverse matrix CKB (n) as shown in Equation 9 is calculated as the inverse matrix of the matrix KB (n) shown in Equation 6 (step S3).
[Equation 7]

[Equation 8]

[Equation 9]

The inverse matrix at this time can be calculated as shown in Equation 10, as is well known. Here, ΔA is a cofactor matrix of the matrix A, and | A | is a determinant of the matrix A.
[Equation 10]

  The coefficients of the inverse matrices CKR (n), CKG (n), and CKB (n) for performing the correction thus calculated are written and stored in the parameter storage unit 51e as calculation parameters (step S4). .

  Thereafter, when the polarization characteristic correction process is performed on the image information for display, the coefficient of the correction matrix stored in the parameter storage unit 51e is written as a calculation parameter of the polarization characteristic correction processing unit 52a (step S5). . Thereby, the polarization characteristic correction processing unit 52a automatically performs correction calculation using the calculation parameter every time image information is input.

That is, when the video signals INAR (N), INBR (N), INRR (N), INCR (N) relating to the R color are input, the correction is performed as shown in the following equation 11 to obtain a corrected result. The video signals HINAR (N), HINBR (N), HINDR (N), and HINCR (N) are calculated.
[Equation 11]

Further, when the video signals INAG (N), INBG (N), INDG (N), INCG (N) relating to the G color are input, the correction is performed as shown in the following Expression 12, Video signals HINAG (N), HINGB (N), HINGG (N), and HINGG (N) are calculated.
[Equation 12]

Similarly, when the video signals INAB (N), INBB (N), INDB (N), INCB (N) relating to the B color are input, the correction is performed as shown in the following Equation 13 and the corrected Video signals HINAB (N), HINBB (N), HINDB (N), and HINCB (N) are calculated.
[Equation 13]

  Then, by using these corrected video signals to display on the display unit 21 via the display control unit 29, it is possible to display the originally intended image without false colors or the like.

  In this way, the polarization characteristic correction processing unit 52a corrects the polarization characteristics of the pixel-swiring polarization rotation liquid crystal cells 22 and 24 for each color (more precisely, for each spectral wavelength).

  As described above, when the process of step S5 is completed, the process exits the polarization characteristic correction parameter calculation process and returns to the main routine or the like.

  Next, FIG. 14 is a flowchart showing a process for performing the polarization characteristic correction parameter calculation process for each predetermined usage elapsed time.

  When this process is started, the polarization characteristic correction parameter calculation setting time stored in advance in the parameter storage unit 51e is read (step S11).

  Next, the usage elapsed time since the previous polarization characteristic correction parameter calculation is detected (step S12). This detection is performed, for example, by referring to a nonvolatile storage value of a timer register (not shown) and comparing it with the current time.

  Subsequently, it is determined whether or not the elapsed usage time is equal to or longer than the polarization characteristic correction parameter calculation setting time (step S13).

  Here, when the usage elapsed time is equal to or longer than the polarization characteristic correction parameter calculation setting time, the polarization characteristic correction parameter calculation process as shown in FIG. 13 is executed (step S14). Thereby, a new correction parameter is stored in the parameter storage unit 51e.

  Then, the non-volatile storage value of the timer register as described above is reset, that is, the usage elapsed time is set to 0 (step S15).

  If the process of step S15 ends, or if it is determined in step S13 that the usage elapsed time has not yet reached the polarization characteristic correction parameter calculation setting time, this process ends.

  Next, FIG. 15 is a flowchart showing a process for performing the polarization characteristic correction parameter calculation process for each predetermined temperature change amount.

  When this process is started, the current temperatures of the polarization rotation liquid crystal cells 22 and 24 stored in the temperature register 51b are read (step S21).

  Next, the temperature of the polarization rotation liquid crystal cells 22 and 24 when the previous polarization characteristic correction parameter calculation process stored in the temperature register 51b is performed is read (step S22).

  Then, a temperature difference absolute value between the temperature read in step S21 and the temperature read in step S22 is calculated (step S23).

  It is determined whether or not the absolute value of the temperature difference thus calculated is a predetermined temperature value, for example, 10 ° C. or more (step S24).

  In this step S24, when it is determined that the temperature difference absolute value is 10 ° C. or more, the current temperature value is set to the previously detected temperature (step S25), and the stored value of the temperature register 51b is rewritten (step S25). S26).

  Subsequently, a polarization characteristic correction parameter calculation process as shown in FIG. 13 is executed (step S27).

  If the process of step S27 ends, or if it is determined in step S24 that the temperature difference absolute value has not yet reached the predetermined temperature value, this process ends.

  Next, FIG. 16 is a flowchart showing a process for calculating a polarization characteristic correction parameter every time the image display apparatus is powered on.

  When this process is started, the on / off state of the power switch 56 is detected (step S31).

  Subsequently, the state of the power switch 56 detected last time is read from a nonvolatile power switch state register (not shown) provided in the system control microcomputer 51 (step S32).

  Then, it is determined whether or not the current power switch 56 detected in step S31 is on (step S33).

  If it is determined in step S33 that the current state of the power switch 56 is on, the state of the power switch 56 is changed from the off state by comparing with the state of the power switch 56 read in step S32. It is determined whether or not the state has changed to an on state (step S34).

  If it is determined in step S34 that the state of the power switch 56 has changed from the off state to the on state, the on state, which is the current state of the power switch 56, is stored in the power switch state register (step S34). S35), a polarization characteristic correction parameter calculation process as shown in FIG. 13 is performed (step S36).

  When it is determined that the process of step S36 is completed or the state of the power switch 56 has not changed from the off state to the on state in step S34 (that is, the state of the power switch 56 has been on previously). If it is still in the ON state), each process such as video display is performed (step S37), and then the process returns to step S31 to repeat the process as described above.

  On the other hand, when it is determined in step S33 that the current power switch is not in the on state (that is, in the off state), it is determined whether or not the state of the power switch 56 has changed from the on state to the off state. (Step S38).

  If it is determined in step S38 that the state of the power switch 56 has changed from the on state to the off state, the current off state of the power switch 56 is stored in the power switch state register (step S39). .

  When it is determined in step S38 that the state of the power switch 56 has not changed from the on state to the off state (that is, when the state of the power switch 56 has been previously off and is currently off), or step When the process of S39 is completed, the process returns to step S31 and the above-described processes are repeated.

  Next, FIG. 17 is a flowchart showing a process for performing the polarization characteristic correction parameter calculation every time the video input terminal is switched.

  When this process is started, the video input selection setting is read from a video selection register (not shown) built in the video switching control circuit 51f (step S41).

  Subsequently, the connection states of the video input terminals 62a to 62c are detected via the signal detection circuits 63a to 63c (step S42), and whether or not the video signal of the video input terminal set for video input selection is valid. Is determined (step S43).

  If it is determined in step S43 that the video signal of the video input terminal set for video input selection is invalid, it is determined whether there is another video input terminal with a valid video signal ( Step S44).

  If it is determined in step S44 that there is another video input terminal with a valid video signal, the video input selection is performed in accordance with a predetermined order determined in advance among the valid video input terminals. Is switched to the priority video input terminal (step S45).

  Then, the video input selection setting in the video selection register is rewritten to the video input terminal set in step S45 (step S46), and the polarization characteristic correction parameter calculation process as shown in FIG. 13 is performed (step S47).

  If it is determined in step S43 that the video signal of the video input terminal set for video input selection is valid, or if it is determined in step S44 that there is no other video input terminal for which the video signal is valid, Alternatively, when the process of step S47 is finished, this process is finished.

  Next, FIG. 18 is a flowchart showing processing for selecting whether or not to perform polarization characteristic correction according to the result of detecting the polarization characteristic of the polarization swivel liquid crystal cells 22 and 24.

  When this process is started, a polarization characteristic correction parameter calculation process as shown in FIG. 13 is first performed (step S51).

  Next, based on the detection result, the correction processing parameter calculation unit 51d calculates the polarization ratio as shown in Equation 1 (step S52).

  Then, it is determined whether or not the calculated NB measurement black polarization ratio RNB (B) is a predetermined value or more, for example, 0.1 (10%) or more (step S53). Such a determination is made because false colors and unevenness are likely to be noticeable when the NB measurement black polarization ratio RNB (B) is large.

  In step S53, when it is determined that the NB measurement black polarization ratio RNB (B) is 10% or more, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and the output selection switch As an output of 52b, an image signal subjected to the polarization characteristic correction processing from the polarization characteristic correction processing unit 52a is selected (step S54).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to supply power to the polarization characteristic correction processing unit 52a (step S55).

  On the other hand, if it is determined in step S53 that the NB measurement black polarization ratio RNB (B) is less than 10%, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b to select the output. As an output of the switch 52b, the image signal before correction from the input selection switch 64 is selected (step S56).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to stop the power supply to the polarization characteristic correction processing unit 52a (step S57).

  Thus, when the process of step S55 or step S57 is performed, this process ends.

  In the description of FIG. 18, the polarization characteristic correction parameter calculation process shown in FIG. 13 is performed in step S51. However, only the process of step S1 and the calculation process of equation 1 are performed in the step S51. You may make it do. At this time, only when it is determined in step S53 that the NB measurement black polarization ratio RNB (B) is 10% or more, it is sufficient to perform the processes in steps S2 to S5 shown in FIG.

  Next, FIG. 19 is a flowchart showing processing for turning off the power of the polarization characteristic correction processing unit 52a when the zoom magnification of the projection optical system 31 is smaller than a predetermined value.

  When this process is started, the correction process parameter calculation unit 51d acquires information regarding the zoom magnification of the projection optical system 31 from the zoom / focus position information detection unit 33 (step S61).

  Then, it is determined whether or not the zoom magnification of the projection optical system 31 is a predetermined value, for example, twice or more (step S62). Such a determination is made because if the zoom magnification is large, an image is enlarged and projected on the screen 2, so that false colors and unevenness are likely to be noticeable.

  In step S62, when it is determined that the zoom magnification is 2 times or more, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and outputs the polarization characteristic as an output of the output selection switch 52b. The image signal that has been subjected to the polarization characteristic correction processing from the correction processing section 52a is selected (step S63).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to supply power to the polarization characteristic correction processing unit 52a (step S64).

  On the other hand, if it is determined in step S62 that the zoom magnification is less than two times, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and the input is output as the output of the output selection switch 52b. The image signal before correction from the selection switch 64 is selected (step S65).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to stop the power supply to the polarization characteristic correction processing unit 52a (step S66).

  Thus, when the process of step S64 or step S66 is performed, this process is terminated.

  Next, FIG. 20 is a flowchart showing processing for turning off the power of the polarization characteristic correction processing unit 52a when the focal position of the projection optical system 31 is closer than a predetermined position.

  When this process is started, the correction process parameter calculation unit 51d acquires information on the focal position of the projection optical system 31 from the zoom / focus position information detection unit 33 (step S71).

  Then, it is determined whether or not the focal position of the projection optical system 31 is a predetermined value, for example, 3 m or more (step S72). Such a determination is made because if the focal position is far, an image is enlarged and projected on the screen 2, so that false colors and unevenness are likely to be noticeable.

  In step S72, when it is determined that the focal position is 3 m or more, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and corrects the polarization characteristic as an output of the output selection switch 52b. The image signal that has been subjected to the polarization characteristic correction processing from the processing unit 52a is selected (step S73).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to supply power to the polarization characteristic correction processing unit 52a (step S74).

  On the other hand, if it is determined in step S72 that the focal position is less than 3 m, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b and selects the input as the output of the output selection switch 52b. The image signal before correction from the switch 64 is selected (step S75).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to stop the power supply to the polarization characteristic correction processing unit 52a (step S76).

  Thus, when the process of step S74 or step S76 is performed, this process ends.

  Next, FIG. 21 shows a process for controlling on / off of the polarization characteristic correction processing unit 52a according to the polarization characteristics of the polarization swivel liquid crystal cells 22 and 24 and the zoom magnification and focus position of the projection optical system 31. It is a flowchart.

  When this process is started, a polarization characteristic correction parameter calculation process as shown in FIG. 13 is first performed (step S81).

  Next, based on the detection result, the correction processing parameter calculation unit 51d calculates the polarization ratio as shown in Equation 1 (step S82).

  Then, it is determined whether or not the calculated NB measurement black polarization ratio RNB (B) is not less than a predetermined value, for example, not less than 0.1 (10%) (step S83).

  In this step S83, when it is determined that the NB measurement black polarization ratio RNB (B) is 10% or more, the correction processing parameter calculation unit 51d performs the operation of the projection optical system 31 from the zoom / focus position information detection unit 33. Information about the zoom magnification is acquired (step S84).

  Then, it is determined whether or not the zoom magnification of the projection optical system 31 is a predetermined value, for example, twice or more (step S85).

  In this step S85, when it is determined that the zoom magnification is 2 times or more, the correction processing parameter calculation unit 51d acquires information on the focal position of the projection optical system 31 from the zoom / focus position information detection unit 33. (Step S86).

  Then, it is determined whether or not the focal position of the projection optical system 31 is a predetermined value, for example, 3 m or more (step S87).

  In this step S87, when it is determined that the focal position is 3 m or more, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and corrects the polarization characteristic as an output of the output selection switch 52b. The image signal that has been subjected to the polarization characteristic correction processing from the processing unit 52a is selected (step S88).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to supply power to the polarization characteristic correction processing unit 52a (step S89).

  On the other hand, if it is determined in step S83 that the NB measurement black polarization ratio RNB (B) is less than 10%, if it is determined in step S85 that the zoom magnification is less than 2, or the focus position is determined in step S87. When it is determined that the length is less than 3 m, the correction processing parameter calculation unit 51d outputs a switching signal to the output selection switch 52b, and the image signal before correction from the input selection switch 64 is output as the output selection switch 52b. Is selected (step S90).

  Thereafter, the system control microcomputer 51 controls the polarization characteristic correction processing unit power source 57 to stop the power supply to the polarization characteristic correction processing unit 52a (step S91).

  Thus, when the process of step S89 or step S91 is performed, this process is terminated.

  In the description of FIG. 21, the polarization characteristic correction parameter calculation process shown in FIG. 13 is performed in step S81. However, only the process of step S1 and the calculation process of equation 1 are performed in the step S81. You may make it do. At this time, it is only necessary to perform steps S2 to S5 shown in FIG. 13 only when it is determined in step S87 that the focal position is 3 m or more.

  In the above description, the image display device that displays color images sequentially in the color plane has been described. However, the present invention is not limited to this. For example, a multi-panel display method having an independent optical path for each color constituting a color image. Of course, application to an image display device is also possible.

  According to the first embodiment, since the sensor unit for detecting the polarization characteristic of the polarization rotation liquid crystal cell for pixel shifting is incorporated in the image display device, the polarization characteristic of the polarization rotation liquid crystal cell is detected almost in real time. It becomes possible to do.

  Then, since a correction calculation block for correcting image degradation based on the detected polarization characteristic is incorporated in the image display device, correction of image information is performed using false color correction parameters updated in a timely manner. Can do. As a result, even when there is a temperature change or a secular change, it is possible to follow up at any time, to reduce false colors and to display a high-quality image.

  In addition, every time the elapsed time since the previous polarization characteristic correction parameter calculation has reached a predetermined time, the polarization characteristic correction parameter calculation is automatically performed again, so there is no need for troublesome manual operation. It is possible to display a quality image.

  In addition, every time the absolute value of the temperature change since the previous polarization characteristic correction parameter calculation reaches a predetermined temperature, the polarization characteristic correction parameter calculation is automatically performed again, eliminating the need for troublesome manual operations. It is possible to always display a high-quality image following the change in ambient temperature and the change in temperature in the image display device.

  And every time the power switch of the image display device changes from OFF to ON, the polarization characteristic correction parameter calculation is automatically performed again, so that it is not necessary to perform troublesome manual operation, especially following aging, etc. Therefore, it is possible to always display a high-quality image.

  Furthermore, every time the selection state of the video input terminal changes, the polarization characteristic correction parameter calculation is automatically performed again, so there is no need for troublesome manual operation, and it always follows changes in the connection environment, etc. A high-quality image can be displayed.

  In addition, when the false color or unevenness is inconspicuous (for example, when the measurement value of the polarization ratio is high, when the zoom magnification is large, or when the focal position is far away), the power of the polarization characteristic correction processing unit is automatically turned on. Therefore, power consumption can be reduced and noise reduction can be achieved without performing troublesome manual operation. In particular, the polarization characteristic correction processing unit needs to perform complicated arithmetic processing at high speed following a displayed image in real time, and is considered to be relatively large in power consumption. Become.

  In this way, since the polarization characteristic of the polarization swivel liquid crystal cell is directly measured to determine the parameters for the correction calculation processing of the image information, the polarization characteristic of the polarization swirl liquid crystal cell is indirectly estimated by measuring the temperature etc. Unlike the above, it is possible to execute a more accurate false color correction process that does not include an error. This makes it possible to display a high-quality image by performing pixel shifting with higher accuracy.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the spirit of the invention.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a sensor unit for measuring the polarization characteristics of a polarization swivel liquid crystal cell, a pixel shift unit including the sensor unit, and an image display device including the pixel shift unit.

1 is a diagram illustrating an outline of a configuration mainly related to an optical system of an image display apparatus according to Embodiment 1 of the present invention. The figure which shows the basic composition of the sensor unit in the said Embodiment 1. FIG. In the said Embodiment 1, the figure for demonstrating the effect | action which performs a light ray shift by a pixel shift part, and performs 4 point | piece pixel shift. 4 is a pixel shift timing chart in the color image display device of the single-plate color plane sequential display method according to the first embodiment. In the first embodiment, a perspective view showing a configuration example in which three polarizing plates, two light sources for measurement, and two light receiving elements are fixedly arranged in parallel Nicols and crossed Nicols for each polarization rotation liquid crystal cell. Figure. In the first embodiment, for each polarization swivel liquid crystal cell, three polarizing plates, one measuring light source, and one light receiving element are arranged so that parallel Nicol and crossed Nicol can be switched in a time-sharing manner. The perspective view which shows an example. In the first embodiment, a configuration example in which a polarizing plate and a light receiving element for performing normally black measurement and normally white measurement are arranged to be able to enter and exit in an optical path through which a display light beam passes in the pixel shifting unit. FIG. FIG. 3 is a block diagram mainly showing an electrical configuration of the image display apparatus according to the first embodiment. In the said Embodiment 1, the diagram which shows the drive waveform of a polarization rotation control signal, and the waveform of the light quantity measurement output signal obtained from a light receiving element. In the said Embodiment 1, the diagram for demonstrating the shift | offset | difference from the ideal linearly polarized light by a polarizing plate when the polarization rotation liquid crystal cell is turned on. In the said Embodiment 1, a diagram for demonstrating that elliptically polarized light generate | occur | produces when at least one of two polarization | polarized-light rotation liquid crystal cells is an OFF state. FIG. 3 is a diagram illustrating an example of a pixel array of image information in the first embodiment. 5 is a flowchart showing a basic operation of calculation of polarization characteristic correction parameters in the first embodiment. 5 is a flowchart showing processing for performing polarization characteristic correction parameter calculation processing for each predetermined usage elapsed time in the first embodiment. 7 is a flowchart showing processing for performing polarization characteristic correction parameter calculation processing for each predetermined amount of temperature change in the first embodiment. 6 is a flowchart illustrating processing for performing a polarization characteristic correction parameter calculation every time the image display apparatus is powered on in the first embodiment. 7 is a flowchart illustrating processing for performing a polarization characteristic correction parameter calculation every time the video input terminal is switched in the first embodiment. 5 is a flowchart illustrating processing for selecting whether or not to perform polarization characteristic correction according to the result of detecting the polarization characteristic of the polarization rotation liquid crystal cell in the first embodiment. 9 is a flowchart showing processing for turning off the power of the polarization characteristic correction processing unit when the zoom magnification of the projection optical system is smaller than a predetermined value in the first embodiment. 9 is a flowchart showing processing for turning off the power of the polarization characteristic correction processing unit when the focal position of the projection optical system is closer than a predetermined position in the first embodiment. 5 is a flowchart showing processing for controlling on / off of a polarization property correction processing unit according to the polarization property of a polarization rotation liquid crystal cell, the zoom magnification and the focal position of a projection optical system in the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector 2 ... Screen (display optical means)
5. Illumination unit (image modulation means)
6 ... Pixel shifting part 7 ... Display optical part 11 ... Light source for display 11a ... Light source part 11b ... Elliptic reflector 12 ... Color wheel 12b ... B filter 12g ... G filter 12r ... R filter 13 ... PS conversion element 14 ... Integral rod 15 ... Illumination optical system 20 ... pixel shifting unit 21 ... display unit (image modulation means)
DESCRIPTION OF SYMBOLS 22 ... 1st polarization rotation liquid crystal cell 22a ... Display area 22b ... Detection area 23 ... 1st birefringent plate 24 ... 2nd polarization rotation liquid crystal cell 24a ... Display area 24b ... Detection area 25 ... 2nd Birefringent plate 26 ... 1st sensor unit 27 ... 2nd sensor unit 28 ... Light-shielding member 29 ... Display control part 31 ... Projection optical system (display optical means)
32 ... Zoom / focus drive mechanism 33 ... Zoom / focus position information detector 41, 41A1, 41A2 ... Measuring light source 42, 42A, 42B ... Polarizing plate (first polarizing means)
42a: Polarization transmission axis 43, 43Ap, 43As, 43Bp, 43Bs, 43p, 43s ... Polarizing plate (second polarizing means)
43a: Polarization transmission axis 44, 44A, 44A1, 44A2, 44B, 44B1, 44B2 ... Light receiving element (light receiving means)
44a ... Light receiving portion 45, 45A, 45B ... Color filter 45Ab, 45Bb, 45b ... B color filter 45Ag, 45Bg, 45g ... G color filter 45Ar, 45Br, 45r ... R color filter 46, 46A, 46B ... Color filter position control mechanism 46a, 46Aa, 46Ba ... rack 46b, 46Ab, 46Bb ... motor 47 ... polarizing plate polarization direction control section (switching means)
47A, 47B ... Polarizing plate position control mechanism (switching means)
47Aa, 47Ba ... frame member 47Ab, 47Bb ... rack 47Ac, 47Bc ... motor 48 ... sensor unit position control mechanism (moving means)
48a ... rack 48b ... motor 51 ... system control microcomputer (measuring means)
51a ... Lighting control circuit 51b ... Temperature register 51c ... Polarization characteristic calculation unit 51d ... Correction processing parameter calculation unit 51e ... Parameter storage unit (non-volatile storage means)
51f ... Video switching control circuit 51g ... Color filter position control circuit 52 ... Correction calculation block (image information correction calculation means)
52a ... Polarization characteristic correction processing unit 52b ... Output selection switch 53 ... Light source light emission circuit 54 ... Liquid crystal cell drive circuit 55 ... Temperature detection device (temperature detection means)
56 ... Power switch 57 ... Polarization characteristic correction processing power supply (power control means)
58... Sequential timing control circuit 59... Pixel shifting frame sequential unit 61... Video switching operation button 62 a .. first video input terminal (signal input means)
62b ... Second video input terminal (signal input means)
62c ... Third video input terminal (signal input means)
63a: first signal detection circuit (signal input means)
63b ... second signal detection circuit (signal input means)
63c ... Third signal detection circuit (signal input means)
64 ... Input selection switch (signal input means)

Claims (27)

A sensor unit for measuring polarization characteristics of a polarization swivel liquid crystal cell for wobbling display of an image,
A first polarizing means arranged on one side of the polarization-rotating liquid crystal cell and passing only light of a predetermined first polarization direction in the measurement light;
Light having a predetermined second polarization direction in the measurement light that is arranged on the other side of the polarization rotation liquid crystal cell, passes through the first polarization means, and then passes through the polarization rotation liquid crystal cell. A second polarizing means for passing only
A light receiving means that is arranged on the other side of the polarization rotation liquid crystal cell and that measures the amount of measurement light that has passed through the second polarizing means;
Measuring means for determining the polarization characteristics of the polarization swirl liquid crystal cell based on information on the driving state of the polarization swirl liquid crystal cell and the measured value of the amount of light received by the light receiving means;
A sensor unit comprising: A sensor unit according to claim 1;
Polarized light that is arranged between the first polarizing means and the second polarizing means and performs wobbling display of an image by controlling whether or not to rotate the polarization of modulated light related to an incident image. A swivel liquid crystal cell;
A birefringent plate on which the modulated light having passed through the polarization rotation liquid crystal cell is incident;
A pixel shifting unit comprising: A pixel shifting unit according to claim 2;
Image modulation means for emitting modulated light modulated in accordance with input image information toward the polarization rotation liquid crystal cell;
Display optical means for displaying the modulated light that has passed through the birefringent plate so as to be observable;
An image information correction calculation means for calculating a correction parameter for image information correction calculation based on the polarization characteristic obtained by the measurement means, and correcting the image information using the correction parameter;
An image display device comprising:   3. The pixel shifting unit according to claim 2, wherein the first polarizing means and the second polarizing means are arranged in parallel Nicols.   3. The pixel shifting unit according to claim 2, wherein the first polarizing means and the second polarizing means are further arranged in crossed Nicols.   The first polarizing means and the second polarizing means are provided in two sets, one set fixedly arranged in parallel Nicols and the other set fixedly arranged in crossed Nicols. 6. The pixel shifting unit according to claim 5, wherein the pixel shifting unit is provided.   6. The apparatus according to claim 5, further comprising switching means for switching the first polarizing means and the second polarizing means so that parallel Nicols and crossed Nicols are arranged in a time-sharing manner. Pixel shift unit described in 1. The polarization swivel liquid crystal cell is configured to include a display region that is a region through which a display light beam passes, and a detection region disposed outside the display region.
The first polarizing means, the second polarizing means, and the light receiving means are arranged on an optical path of measurement light passing through the detection region. The pixel shifting unit described.   The pixel shifting unit according to claim 8, further comprising a measurement light source for emitting the measurement light.   A position where at least the second polarizing means and the light receiving means in the sensor unit are retracted from the display area, which is an area through which the display light flux passes, in the polarization swivel liquid crystal cell, and for display passing through the display area 6. The pixel shifting unit according to claim 4, further comprising moving means for moving to a position arranged on the optical path of the luminous flux.   5. The pixel shifting unit according to claim 4, wherein the measuring means calculates a ratio between a white level in the parallel Nicol state and a black level in the parallel Nicol state to obtain a polarization characteristic.   The measurement means is characterized in that a polarization characteristic is obtained by performing calculation using four values of a white level and a black level in a parallel Nicol state and a white level and a black level in a crossed Nicol state. The pixel shifting unit according to claim 5.   3. The pixel shifting unit according to claim 2, wherein the measuring means calculates a plurality of polarization characteristics based on a plurality of measurement values, and uses an average value of the plurality of polarization characteristics as the polarization characteristics.   The measuring means newly obtains the polarization characteristics of the polarization swirl liquid crystal cell when the usage time of the polarization swirl liquid crystal cell has reached a predetermined time since the last determination of the polarization characteristics of the polarization swirl liquid crystal cell. The pixel shifting unit according to claim 2, wherein the pixel shifting unit is provided. Further comprising a temperature detection means for measuring the temperature of the polarization rotation liquid crystal cell,
The measuring means newly obtains the polarization characteristic of the polarization swirl liquid crystal cell when the amount of change in temperature of the polarization swirl liquid crystal cell has reached a predetermined value since the polarization characteristic of the polarization swirl liquid crystal cell was previously obtained. The pixel shifting unit according to claim 2, wherein the pixel shifting unit is one.   3. The pixel shifting unit according to claim 2, wherein the measuring means obtains a polarization characteristic of the polarization rotation liquid crystal cell every time the pixel shifting unit is activated. A plurality of video signals can be selectively switched and input, and further comprises signal input means for outputting image information corresponding to the input video signal,
4. The image display device according to claim 3, wherein the measuring means obtains a polarization characteristic of the polarization rotation liquid crystal cell every time a system of video signals inputted to the signal input means is switched. . When configuring a pre-correction vector using a signal at each pixel position of wobbling in the image information before correction as a component, and configuring a corrected vector using a signal at each pixel position of wobbling in the image information after correction as a component,
The image information correction calculation means calculates an inverse matrix of the matrix using the polarization characteristic as a correction parameter of the image information correction calculation, and calculates a corrected vector by performing a matrix calculation on the correction parameter to the pre-correction vector. The image display device according to claim 3, wherein the image information is corrected.   The sensor unit according to claim 1, further comprising a non-volatile storage means for storing the polarization characteristic obtained by the measurement means.   19. The image display device according to claim 18, further comprising non-volatile storage means for storing an inverse matrix of the matrix using the polarization characteristic obtained by the image information correction calculation means. The image display device displays a color image,
The measuring means obtains the polarization characteristics of the polarization swivel liquid crystal cell for each color constituting the color image,
4. The image display device according to claim 3, wherein the image information correction calculation means corrects the image information for each color.   The image display device according to claim 21, wherein the image display device displays a color image in color plane order.   The image display device according to claim 21, wherein the image display device displays a color image by a multi-panel display method having an independent optical path for each color constituting the color image. A power control unit for turning on / off power supply to the image information correction calculation unit;
4. The power supply control means according to claim 3, wherein the power supply control means turns off the power supply to the image information correction calculation means when the polarization characteristic obtained by the measurement means is within a predetermined range. The image display device described. The display optical means is configured to have a zoom optical system,
A power control unit for turning on / off power supply to the image information correction calculation unit;
4. The power supply control means according to claim 3, wherein the power supply control means turns off the power supply to the image information correction calculation means when the zoom magnification of the display optical means is less than a predetermined value. Image display device. The display optical means includes a focus optical system for adjusting the focal position,
A power control unit for turning on / off power supply to the image information correction calculation unit;
4. The power supply control means according to claim 3, wherein the power supply control means turns off the power supply to the image information correction calculation means when the focal position of the display optical means is closer than a predetermined position. Image display device. The display optical means comprises a zoom optical system and a focus optical system for adjusting the focal position,
A power control unit for turning on / off power supply to the image information correction calculation unit;
The power control means has a polarization characteristic determined by the measuring means within a predetermined range, the zoom magnification of the display optical means is less than a predetermined value, and the focal position of the display optical means is more than a predetermined position. 4. The image display device according to claim 3, wherein when close, power supply to the image information correction calculation means is turned off.

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