JP4430647B2 - Image display device - Google Patents

Description

  The present invention relates to an image display apparatus that displays an output image of an image display element having a plurality of pixels whose light can be controlled according to image information by an image forming optical element.

  Product names such as front projectors, rear projectors, and head-mounted displays are used as image display devices that display the output image of a small image display element having a plurality of pixels that can control light in accordance with image information using an image forming optical element. Widely used in. As this image display element, CRT, liquid crystal panel, DMD (trade name: Texas Instruments Inc .: USA) and the like are used as products, and inorganic EL, inorganic LED, organic LED, etc. are also being studied. .

  Further, as an image display device for observing the output image of the image display element at the same magnification, instead of observing an image obtained by enlarging the output image of the small image display element with a lens, the above-described CRT, liquid crystal panel In addition to inorganic EL, inorganic LEDs, and organic LEDs, plasma displays, fluorescent display tubes, and the like are used as products, and FED (field emission display), PALC (plasma addressing display), and the like have been studied. These are broadly classified into two types, a self-luminous type and a spatial light modulator type, and each has a plurality of pixels that can control light.

  The problem common to these image display devices is to increase the resolution, that is, to increase the number of pixels, and an image display device for HDTV having about 1000 scanning lines for the purpose of broadcast display has already been commercialized. A development product of about 2000 scanning lines for the purpose of high-resolution display of a workstation computer has been announced with a technology using a liquid crystal panel ('98 flat panel display exhibition, IBM Japan's QSXGA 2048, '98 Toshiba 2400 UXGA, etc. at the Electronic Display Exhibition). However, increasing the number of pixels decreases the yield of the liquid crystal panel and decreases the aperture ratio, which increases costs, decreases brightness and contrast, and increases power consumption. It was.

  As a method of increasing the number of pixels more than twice using a plurality of conventional image display elements, there are those described in Patent Document 1 and Patent Document 2. In these devices, a plurality of image display elements are optically displaced from each other, and each image display element has a pixel disposed at a position that is a gap between the pixels. However, these are difficult to align between a plurality of pixels, and use of a plurality of image display elements increases the cost and requires a large projection lens.

  For these problems, Patent Document 3, Patent Document 4, Patent Document 5, and the like describe an image display device that performs interlaced display having a double number of pixels using a single image display element. Yes. Patent Document 6 describes an image display device that displays an image having a pixel number four times or more using a single image display element. The combination of a member exhibiting an electro-optic effect and a birefringent crystal used by these is a known technique as a deflecting means conventionally used as an optical distribution and optical switch in the field of optical communication.

  In addition to the combination of a member exhibiting an electro-optic effect and a birefringent crystal, Patent Document 5 describes means capable of shifting a lens, a vari-angle prism, a rotating mirror, a rotating glass, and the like as means for changing an optical path. Has been. Patent Document 7 describes means for moving a wedge prism as means for changing the optical path.

  FIG. 9 shows an image display device described in Patent Document 5 for observing a virtual image enlarged by a lens by increasing the resolution of an image display element by a method of shifting a lens. In FIG. 9, 1 is an LCD panel, and 2 is an LCD drive circuit for driving the LCD panel 1 with a color video signal to display an image. 3 is an optical path changing means, and 4 is an eyepiece. Reference numeral 5 denotes a voice coil that optically shifts the position of the LCD panel 1 in a direction perpendicular to the optical axis of the eyepiece lens 4, reference numeral 6 denotes a lens mounting base, and reference numeral 7 denotes a drive circuit that drives the voice coil 5. The optical path changing unit 3 includes an eyepiece lens 4, a voice coil 5, a lens mount 6 and a voice coil drive circuit 7.

  The voice coil 5 is driven by a drive circuit 7. The drive circuit 7 determines an odd field and an even field of the color video signal input from the LCD drive circuit 2, and applies the voice coil 5 to the voice coil 5 according to the determination signal O / E. The flowing current is controlled, and the position of the LCD panel 1 is optically shifted in a direction perpendicular to the optical axis of the eyepiece 4.

  As a drive system for shifting, that is, reciprocating, the eyepiece 4, not only the voice coil 5 but also a piezoelectric element, a bimorph, a step motor, a solenoid coil, and the like are described in Patent Document 5. Further, as a method of changing the optical path, in addition to the method of shifting the lens and the optical member, a method of inserting the optical member into the optical path, a method of rotating the optical member, a method of rotating the mirror, an active prism, an electro-optical element, and the like Patent Document 5 describes a method using a birefringent material.

  FIG. 10 shows an image display device described in Patent Document 5 in which an image display element is increased in resolution by a method using an electro-optic element and a birefringent material, and a virtual image enlarged by a lens is observed. In FIG. 10, 8 is a polarization plane rotating member that becomes an electro-optical element, and 9 is a birefringent plate. The polarization plane rotating member 8 is configured by depositing transparent electrodes 11 and 12 on both surfaces of the liquid crystal plate 10, and a liquid crystal driving voltage is applied between the transparent electrodes 11 and 12 from the drive circuit 13, and even and odd numbers are applied. The polarization plane is rotated and deflected for each field, and is matched with the polarization planes of normal light and extraordinary light of the birefringent plate 9. The amount of deflection of the normal light and the extraordinary light varies depending on the refractive index difference of the birefringent plate 9.

  Further, in the image display apparatus as described above, when an element with a slow response speed is used as the image display element, the writing start time differs greatly between the first scanning line and the last scanning line in the same image field. Therefore, when a high scanning linear velocity such as a moving image is required, it is difficult to form a uniform optical path change state in the scanning direction, and the contrast tends to be lowered. Regarding methods for improving these, Patent Document 5 describes a method of dividing an electro-optic element into a plurality of scanning lines, and Patent Document 8, Patent Document 9 and the like describe methods for improving this problem. Has been.

  FIG. 11 is a diagram for explaining the image display device described in Patent Document 5 in which the influence due to the difference in writing time between the first scanning line and the last scanning line is reduced. In FIG. 11, reference numeral 14 denotes a liquid crystal as a polarization plane rotating element. This liquid crystal 14 is divided into a plurality of parts in a direction parallel to the scanning line, and the plane of polarization is sequentially changed in synchronization with the scanning of the liquid crystal for image display. , The rotation states of the first and last polarization planes of the image display scanning line are made uniform.

  On the other hand, as an example of a spatial light modulation device for obtaining high luminance in an image display device that performs digital gradation display by modulating the light intensity of illumination light, there is a modulation method described in Patent Document 9. This is because the optical spatial modulation element is provided with a first memory and a second memory, and the image data is transferred from the first memory in which the image data is written to the second memory. This is a method of changing the state of a pixel based on image data in a memory. This method can increase the effective illumination time of the illumination light to the optical spatial modulation element, so that it is possible to perform image display with low cost and high energy savings.

Japanese Patent Laid-Open No. 3-150525 JP-A-4-267290 JP-A-4-113308 Japanese Patent Laid-Open No. 5-289004 JP-A-6-324320 JP 7-36504 A JP-A-7-104278 JP-A-11-296135 Japanese Patent Laid-Open No. 11-259039 Japanese Patent Laid-Open No. 11-75144

  In the image display device described in Patent Document 5, the means for changing the optical path is a means for changing the optical path by shifting or deflecting the optical axis of the magnifying optical system, even if other means are used, and Means for changing these optical paths exists between the image display element and the magnifying optical system.

  For this reason, when high-resolution image display is performed, various optical aberrations are likely to occur by changing the optical path length or using the optical axis of the entire optical system as the off-axis of the lens. Not only is the design and layout of the system unreasonable, but there are also cases where one pixel of a minute image display element cannot be enlarged with a sufficient MTF. In addition, the non-uniformity of the member itself that deflects the optical path may reduce the MTF. Further, when the electro-optic element is used, the wavelength is not a single wavelength as in the case of laser light, so that there is a problem that the color shift of the phase due to the wavelength occurs and the contrast is greatly lowered.

  In the image display device described in Patent Document 5 in which the influence due to the difference in writing time between the first scanning line and the last scanning line is reduced, the cost increases due to the complexity of the element structure and the driving method. . Further, it has not been possible to completely eliminate the non-uniformity in the scanning line direction. This is because the response speed of the display device cannot cope with the current image display device in which the data writing speed in the direction of the scan line is large and the full-color moving image display is performed on the current image display device. It depends.

  Further, full color requires gradation display of 64 to 256 gradations for each color of red, blue, and green. Therefore, analog modulation of normal TN liquid crystal and dither modulation for high-speed FLC are possible. A combination of pulse width modulation is used, but for image display with a large number of pixels, an increase in the defect rate and numerical aperture due to an increase in the absolute number of TFT elements, an FLC response speed and the like Due to limitations on the driving method, the cost increases, and a sufficient number of pixels and image quality are not obtained.

  In the modulation method described in Patent Document 9, the optical spatial modulation element does not require a neutralization condition for canceling the DC component of the liquid crystal in order to reduce the time of the bit plane when performing digital gradation display. The purpose of the drive method is to prevent deterioration of the light source, and also to the purpose of high-luminance and low-cost field sequential display by increasing the light source utilization efficiency. When the image display element is displaced in the image field No attention is paid to the spatial crosstalk of the image.

  In addition, in a conventional image display device that increases the resolution by driving the means for changing the optical path from the image information signal, the displacement amount of the real image or the virtual image due to the magnifying optical system varies in the size of each resolution increasing means and the initial assembly. It is also affected by alignment variations. Furthermore, the assembly position may be misaligned or the amount of misalignment may change due to heat generation, vibration, etc. during use. Pixels at different display positions may overlap or cause color misregistration. In some cases, image quality may deteriorate.

An object of the present invention is to provide an image display device capable of providing a high-resolution enlarged image with high gradation.

In order to achieve the above object, an invention according to claim 1 includes an illumination unit that emits illumination light and an image display element having a plurality of pixels that spatially modulate the illumination light. In the image display device for displaying an output image by an image forming optical element, the image display with respect to the optical axis of the image forming optical element for every four subfields from the first subfield to the fourth subfield constituting the image field. Displacement means for displacing the position of the element in a direction substantially parallel to the pixel array plane, and the first subfield from the first subfield to the fourth subfield are configured by only the first frame, and each subsequent subfield is set to the second frame. constituted by three frames to the fourth frame from the illumination light in turn the fourth frame or the intensity profile from the first frame , And 4,2,1, and, initially, from the first sub-field to the fourth sub-field disposed only the first frame, then each of the first and second subfields, the first from the second frame Only three frames up to four frames are arranged in order, and then the third subfield is arranged in the order of three frames of the fourth frame, the third frame, and the second frame, and is opposite to the second subfield. Are arranged in the frame order, and then the fourth subfield is arranged in order from the second frame to the fourth frame, so that the position of the image display element is changed from the second subfield to the second subfield. Illumination light control means for illuminating light having the same luminance in the second subfield and the third subfield when displaced to the third subfield is provided. Is shall.

According to the present invention , a high-resolution enlarged image with high gradation can be provided.

FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 21 denotes an illumination light source in which red LEDs are arranged in a two-dimensional array. Reference numeral 22 denotes a diffusion plate. The illumination light source 1 and the diffusion plate 2 constitute an illumination unit. Reference numeral 23 denotes a condenser lens, and reference numeral 24 denotes a liquid crystal panel as an image display element having a plurality of pixels capable of controlling light according to image information. Reference numeral 25 denotes a projection lens as an image forming optical element, and reference numeral 26 denotes a screen. Reference numeral 27 denotes a light source drive unit as illumination light control means, and reference numeral 28 denotes a liquid crystal drive unit that drives the liquid crystal panel 24.

  The illumination light source 21 is driven by the light source drive unit 27 to emit illumination light, and the illumination light is made uniform by the diffusion plate 22 and illuminates the liquid crystal panel 24 by the condenser lens 23. The liquid crystal panel 24 is controlled by the liquid crystal drive unit 28 in accordance with image information in synchronization with the illumination light source 21, so that the illumination light from the condenser lens 23 is critically illuminated and the illumination light is converted according to the image information. Spatial modulation is performed, and the spatially modulated illumination light is output as image light (output image) corresponding to image information. The output image of the liquid crystal panel 24 is enlarged by the projection lens 25 and projected onto the screen 26, whereby the image is displayed on the screen 26 and this image is observed.

  The liquid crystal panel 24 is connected to a support body 29 in the vertical direction, and the support body 29 is fixed to an image display element shift means made of a small piezoelectric element 30 made of a piezoelectric element. The piezoelectric element 30 has an effective position of the image display element 24 corresponding to a plurality of subfields constituting an image field (hereinafter simply referred to as a field) x, which is parallel (or substantially parallel) to the pixel array surface. It is a displacement means that optically displaces in the y direction, and is controlled by the piezoelectric element drive unit 31. Although not visible in FIG. 1, the liquid crystal panel 24 is connected to a support body in a direction perpendicular to the paper surface, and the support body is fixed to an image display element shift means made of a small piezoelectric element made of a piezoelectric element. This piezoelectric element is controlled by the piezoelectric element drive unit 31. The liquid crystal panel unit 32 includes a liquid crystal panel 24, a support 29, a piezoelectric element 30, and a support and a piezoelectric element that cannot be seen in FIG.

In the first reference embodiment, the piezoelectric element 30 and the piezoelectric element not visible in FIG. 1 are driven by the piezoelectric element drive unit 31 to move the liquid crystal panel 24 in the x and y directions. In this case, the piezoelectric element drive unit 31 divides one field into one basic unit, and divides it into four subfields, and the liquid crystal panel 24 divides the image pitch in half in the x and y directions every four subfields. The piezoelectric element 30 is driven so as to reciprocate.

  The period during which the liquid crystal panel 24 moves is a period in which the flicker that is felt when the output image of the liquid crystal panel 24 is enlarged and displayed on the screen 26 is equal to or less than a practical level. In the subfield corresponding to the displaced position of the liquid crystal panel 24, image data corresponding to that position is displayed on the screen 26, so that the number of images displayed is four times that when the liquid crystal panel 24 is not moved. It can be performed.

  FIG. 2 shows an example of the liquid crystal panel unit 32 and is a view seen from the right direction of FIG. In FIG. 2, reference numerals 29 'and 30' denote a support and a piezoelectric element that are not visible in FIG. The holding member 33 for holding the liquid crystal panel 24, the support 29, and the piezoelectric element 30 is connected to the support 29 'in the left-right direction, and the support 29' is fixed to a small piezoelectric element 30 'made of piezo. The piezoelectric elements 30 and 30 ′ are driven by the piezoelectric element drive unit 31 to displace the position of the liquid crystal panel 24 with respect to the optical axis of the projection lens 25 in the x and y directions substantially parallel to the pixel array surface. In FIG. 2, the displacement value Δx in the x direction in which the holding member 33 is displaced from the position x1 to the position x0, and the displacement value Δy in the y direction in which the holding member 33 is displaced from the position y1 to the position y0. Displacement in the x and y directions.

  FIG. 3 shows an outline when the pixels of the liquid crystal panel 24 (actual pixel portions of a 3 × 3 liquid crystal panel) are enlarged and observed. When the image pitch of the liquid crystal panel 24 is 2Δx and 2Δy in the x direction and y direction, respectively, Δx and Δy, which are ½ the pitch, are used as the displacement values of the liquid crystal panel 24 in the x direction and y direction, respectively. One actual pixel of the liquid crystal panel 24 can display four pixels, which is four times that of the actual pixel.

  In FIG. 3, when the position 24a (x0, y0) of the liquid crystal panel 24 is set as the reference position (0, 0), when an actual pixel having an aperture ratio of about 12% is provided at the position 24a, each subfield By setting the positions 24b (x0, y1), 24c (x1, y1), 24d (x1, y0) of the liquid crystal panel 24 to the movement positions (0, 1), (1, 1), (1, 0), Pixels can be displayed at the movement positions 24b, 24c, and 24d, respectively.

  It is not necessary to limit the pitch of these positions 24a to 24d to 1/2 of the pitch of the actual pixel in both the x direction and the y direction. It is also possible to display twice as many pixels by setting the NTSC even and odd fields as subfields by setting the pitch of the actual pixels to ½ only in the y direction. The aperture ratio may be increased or decreased. However, it is preferable that the aperture ratio be around 25% because spatial crosstalk between pixels is reduced and display loss between pixels is difficult to visually recognize.

In the first reference mode, since it is not necessary to deflect the liquid crystal panel and the optical path for each subfield as in the prior art, it is possible to use exactly the same illumination optical system and projection optical system as when the pixels are not multiplied, High-resolution image display can be performed at low cost without degrading the MTF of the optical system. The high-resolution projection lens 25 needs to secure the same MTF for a spatial frequency twice that of the conventional case, and the design burden of the projection optical system can be greatly reduced. In addition, by using a piezoelectric element as a displacement means for displacing the liquid crystal panel 24, the displacement amount can be accurately controlled by the piezoelectric element as compared with a method using a coil, a motor, etc., so the displacement amount is always fed back. Since the drive unit 31 for displacing the liquid crystal panel 24 can be simplified and the liquid crystal panel 24 can be accurately displaced, high-resolution image display with low cost and little deterioration in image quality due to misalignment is possible. It can be performed.

Further, the piezoelectric element is generally applied voltage and the displacement is constrained in the lamination number is smaller, the image display apparatus for observing a 10-50 fold magnified image as in the present reference embodiment, the displacement amount of the original liquid crystal panel Since the displacement of the observed image may be as small as 1/50 to 1/10, the displacement amount is small as an absolute value, and is within the movable range of the piezoelectric element at a voltage within 200V, and in some cases within 100V. The piezoelectric element is not easily restricted by the displacement amount at a practical voltage.

  Furthermore, since the conventional illumination optical system and projection optical system can be used as they are in these image display device configurations, there is no burden of new design, and a low-cost image display device can be provided. Further, in image display without pixel multiplication without displacement by a piezoelectric element, the same optical characteristics as usual can be realized, and this can be easily achieved by switching modes in the same image display device.

As the piezoelectric element 30, it is preferable using a piezoelectric element as in this preferred embodiment. For example, when a piezoelectric element (model number: AE0203D08) manufactured by Tokin Co., Ltd. is used, about 6 μm is obtained with a displacement amount of 100V. The resonance frequency of this piezoelectric element is 138 kHz, and this one-third frequency is the maximum frequency, and high-speed displacement of about 40 kHz or more is possible. Besides the rectangular displacement, the acceleration at the start and end of the displacement is reduced. A displacement profile can be realized.

As the liquid crystal panel 24, the pixel is 10μm pitch Display Technologies, Inc. (USA) using a LCOS (Liquid Crysutal on Si) type spatial light modulator, this preferred embodiment as well as the reflection type illumination optical system and the projection optical system The pixel multiplication can be performed four times. However, as described above, since the requirement for the spatial frequency of the projection lens 25 is doubled for high resolution, it is necessary to use a projection lens corresponding to the resolution. In this reference embodiment, although formed an enlarged real image of the spatial light modulator 24 onto a screen 26 by a projection lens 25, the present invention is not limited to this, the eyepiece in place of the projection lens 25 You may make it observe the virtual image expanded directly using it. At this time, when the field frequency is set to 30 Hz, flicker is likely to occur in such a time-division method, and when the field frequency is set to 120 Hz where flicker is not sufficiently generated, the field frequency is 10 times as high. For example, if the piezoelectric element is driven at about 1.2 kHz, the response speed is sufficient. For this reason, it is sufficient that the resonance frequency is 1.2 kHz or more, which is 10 times higher than that, and preferably 12 kHz corresponding to 100 times or more with respect to the field frequency is sufficient. As a result, the effect of the rise time loss is 1% or less. However, when the end face of the piezoelectric element is actually driven by being bonded to a rigid body holding LCOS, the rigid body and the piezoelectric element generate shock waves during the pulse application time via the adhesive present on the adhesive face, which is lower than the driving frequency. Noise and mechanical shock are generated. In order to prevent this, a piezoelectric element having a resonance frequency of 500 times, preferably 1000 times the field frequency, is used to control the rising characteristics via a resistor, or to apply a rising or falling applied voltage waveform. By controlling to apply at a sufficiently smooth time with respect to the field frequency and at a frequency lower than 1/10 of the resonance frequency, the generation of abnormal noise can be reduced and the mechanical shock can also be reduced. The optimum resonance frequency for the piezoelectric element is 60 kHz or more, which is 500 times or more the field frequency, and preferably 120 kHz or more.

According to the first reference embodiment, the image display apparatus for displaying an output image of the image display device 24 having a plurality of pixels capable of controlling light in accordance with image information by the image forming optical element 25, constituting the image field Displacement means 24 is provided for displacing the position of the image display element 24 with respect to the optical axis of the image forming optical element 25 in a direction substantially parallel to the pixel array surface for each of a plurality of subfields. Since it is constituted by the image display element shift means 27 made of a piezoelectric element having a frequency of 60 kHz or higher, it is possible to give a higher-resolution enlarged image with less deterioration of the optical characteristics of the magnifying optical system.

Figure 4 is a timing chart showing an example of operation of the second referential embodiment of the present invention. In the second reference embodiment , the piezoelectric element 30 is controlled by the piezoelectric element drive unit 31 to displace the liquid crystal panel 24, so that the x-direction position of the liquid crystal panel 24 is two of x0 and x1, as shown in FIG. The position in the y direction of the liquid crystal panel 24 takes two positions, y0 and y1, and by this combination, the position (x, y) of the liquid crystal panel 24 is (x1, y1), (x1) in the period of one field. , Y0), (x0, y1), and (x0, y0) are sequentially displaced, and these positions are respectively positions in the four subfields SF1 to SF4 constituting one field.

In the second referential embodiment, substantially the same configuration portions other than liquid crystal panel 24 and the first referential embodiment different liquid crystal panel 24 and the first reference embodiment. In the liquid crystal panel 24, image data storage means A for inputting image data based on signals from the scanning lines is inputted to the pixels of the liquid crystal panel 24, that is, image data for each of the four subfields SF1 to SF4 constituting one field is inputted. And image data storage means A for storing them. Further, the liquid crystal panel 24 has image data storage means B for outputting image data in which the same pixels of the liquid crystal panel 24 are different from the image data storage means A, that is, the same pixels of the liquid crystal panel 24 are displaced by the displacement of the liquid crystal panel 24. Image data is inputted and stored so that the image data is displayed at a position different from that of the image data storage means A.

  Further, the liquid crystal panel 24 includes transfer means for transferring the image data of the image data storage means A as image data of the image data storage means B, and the voltage of each pixel of the liquid crystal panel 24 based on the image data of the image data storage means B. Drive means for applying, and transfer timing determining means for causing the transfer means to transfer the image data of the image data storage means A as image data of the image data storage means B to the transfer means for each subfield substantially simultaneously.

  In FIG. 4, for the sake of simplicity, a specific data line has four scanning lines (one data line corresponds to four scanning lines). The same applies to data lines, and also in the case where one data line has a plurality of (n) scanning lines other than four (one data line corresponds to n scanning lines). The image data is written in the same manner by changing the writing of image data for four scanning lines to writing of image data for n scanning lines.

  As shown in FIG. 4, the image data is basically input to the image data storage means A in the order of scanning lines 1, 2, 3, and 4. The image data is converted into image data corresponding to a subfield by an image data processing device (not shown) so that one pixel of the liquid crystal panel 24 is quadrupled in advance. Further, the image data corresponding to this subfield is Four scanning lines are input to the image data storage means A in the order of subfields SF1, SF2, SF3, and SF4.

At this time, an image corresponding to a scanning line of a specific subfield is obtained during a period from the time when certain image data is written in the image data storage means A to the time when the next image data is written in the image data storage means A. When image display is performed in the liquid crystal panel 24 as data, the difference in the scanning lines for differences in the image display period occurs, in the present reference embodiment, the illumination light at a time when the liquid crystal panel 24 as shown in FIG. 4 has been moved Irradiation is stopped by the light source drive unit 27 and image display is not performed. At the same time, the image data in the image data storage means A is transferred to the image data storage means B corresponding to the drive means by the transfer means. Therefore, high-resolution and high-contrast image display without spatial crosstalk can be performed.

  More specifically, as shown in FIG. 4, the image data is input to the image data storage means A in the order of the scanning lines 1, 2, 3 and 4, and the sub-fields are stored in the image data storage means A at a specific timing. Although the states are all different for the scanning lines, the image data in the image data storage means A is transferred to another image data storage means B when the input of the image data to the image data storage means A is completed for all the scanning lines. Thus, in the image data stored in the image data storage means B, all the scanning lines become the same subfield in the next subfield. For this reason, by applying a voltage to the pixels of the liquid crystal panel 24 by the driving means according to the contents of the image data storage means B and irradiating the illumination light from the illumination light source 21 to the liquid crystal panel 24, in one subfield period, The image data input to the image data storage means A is displayed in the period of the previous subfield.

According to the second reference embodiment, the first image data storage means and, the same each pixel of the first image data for image data input based on the signal from each pixel scan lines of the image display device 24 Second image data storage means for outputting image data different from the storage means, transfer means for transferring the image data of the first image data storage means as image data of the second image data storage means, Driving means for applying a voltage to each pixel based on the image data in the second image data storage means, and the image display element 24 to the transfer means for each subfield in the image of the first image data storage means Transfer timing determining means for transferring data substantially simultaneously as image data of the second image data storage means, so that high resolution with reduced spatial crosstalk Magnified image can be given.

In the second reference embodiment, the spatial light modulation element 24 is irradiated with illumination light and the illumination light is controlled by spatial light modulation with the spatial light modulation element 24, but the present invention is limited to this configuration. In addition, even when a light emitting element such as an organic EL, an inorganic EL, or an inorganic LED chip array is used, light emitted from the light emitting element can be directly controlled without using illumination light.

FIG. 5 is a timing chart showing an example of the operation of the third embodiment of the present invention. In the third reference embodiment, the piezoelectric element 30 is controlled by the piezoelectric element drive unit 31 to displace the liquid crystal panel 24, so that the x-direction position of the liquid crystal panel 24 is two of x0 and x1, as shown in FIG. The position in the y direction of the liquid crystal panel 24 takes two positions, y0 and y1, and by this combination, the position (x, y) of the liquid crystal panel 24 is (x1, y1), (x1) in the period of one field. , Y0), (x0, y1), and (x0, y0) are sequentially displaced, and these positions are respectively positions in the four subfields SF1 to SF4 constituting one field. The illumination light source 21 is driven by the light source drive unit 27 to irradiate the liquid crystal panel 24 with illumination light having exponentially different intensities in the four frames constituting one subfield.

In the third reference embodiment, the above first reference embodiment are substantially the same structure other than the liquid crystal panel 24, the liquid crystal panel 24 is configured similarly to the liquid crystal panel of the second embodiment. As a result, the third reference form can operate in substantially the same manner as the second reference form, and a specific data line has only one scan line for simplification of description (one scan line). Only). That is, only one specific scanning line of the image display element 24 will be described, but even when the number of scanning lines of one data line is n, the operation is substantially the same as in the second reference embodiment. At this time, it is assumed that there is no delay for one subfield shown in FIG.

  Further, the image data is converted into image data corresponding to the subfield by an image data processing device (not shown) so that one pixel of the image display element 24 is quadrupled in advance. Correspondingly, subfields 1, 2, 3 and 4 are further divided into four frames and simultaneously input to image data storage means A and B, and image data for one field is input and displayed. The

As can be seen from FIG. 5, in one subfield, the illumination light from the illumination light source 21 irradiates the image display element 24 while the illumination light intensity exponentially changes to 4, 4, 2, 1 in four frames. Then, the image display element 24 performs binary spatial light modulation by turning on and off the illumination light in each frame, and as a result, can display an image of 16 gradations in one subfield. Note that the integrated illumination light intensity / SF shown in FIG. 5 indicates the integrated illumination light intensity per subfield, and is an arbitrary unit. However, assuming that the unit time of the frame is 1, the illumination effective by the image data in each frame It is the sum of the light intensity and the unit time of 1 in the subfield. For example, by setting the image data of each frame to image data as shown in FIG. 5, the fields 1, 2, 3, and 4 can display 15 values, 0 values, 5 values, and 1 values, respectively. . Further, by setting the number of frames present reference embodiment 6 or 8, 64 gradations respectively, display of 256 gradations it is possible.

  A conventional image display element based on a TN liquid crystal having a slow response speed cannot display a moving image by increasing the number of pixels by four times or more. This is because a time restriction of 4 times can be achieved by increasing the number of pixels by 4 times. In the conventional gradation display with pulse width modulation for a constant illumination light intensity, the upper limit is about 32 gradations. This means that when the video rate is 60 Hz, 60 × 32 × 4 = 7.68 kHz, the image data has a pulse width of 190 μs, and the image display element has a response at the time of ON / OFF by the image data. It is preferably 1/4 of 33 μs, depending on the applied voltage, but is close to the lower limit of the ferroelectric liquid crystal.

  In addition, in a high-speed image display element (Texas Instruments Inc .: USA) in which micromirrors are formed on silicon, it is possible to display a floor length of 32 gradations or more. The key is the limit. In order to reproduce the gradation of the silver salt film, about 4096 gradations are sufficient, and the image quality of movie image data shot with the silver salt film may be inferior to that of the silver salt film in a dark scene.

However, in this reference embodiment as described above, although a binary image display element is used, a gradation is obtained by a change in the light intensity of the illumination light to obtain a normal gradation of 1/10 in 64 gradations. It is only necessary to divide the frame into 6-fold frames, and it is possible to increase the pixels two-dimensionally by 4 times or more using an image display element made of a ferroelectric liquid crystal, and further, an image in which a micromirror is formed on silicon. In the display element, the number of pixels can be increased by 9 times or more. Further, in the image display device to form a micro mirror on this silicon, in current SXGA, albeit almost equal to the silver film to display an image such as a movie, further illumination light as in the present reference embodiment By changing the light intensity to 4 times the pixel, and enabling the same level of gradation as the silver halide film, a very high quality image that achieves both high resolution and high gradation that surpasses the silver halide film. Can be formed.

These gradations and resolutions are generally visually complementary, but the number of scanning lines and data lines as high resolution is more important up to a class equivalent to 400 dpi if the gradations are 64 gradations or more. It becomes. Therefore, the display current normal image is not compatible to 400 dpi, the increase in pixel according to the reference embodiment can form an image with excellent very visibility. Furthermore, when a high-speed image display element is used, the gradation can be realized in the silver salt film class. Furthermore, the amount of responsiveness can be utilized to increase the scanning line drive frequency. This is very effective in reducing spatial flicker when pixel multiplication is performed.

This third order of the subfields and the frame in the first field of the reference embodiment is not limited to the order shown in FIG. 5, the luminance flicker, color flicker space flicker, the load of data processing and data transfer In order to decrease, the image data may be changed appropriately. This may be in a specific order in advance, but a display order determining means for determining an appropriate display order from the content of the image data of one pixel or the image data of the peripheral pixels and all the pixels is added, and this display is performed. You may determine dynamically by an order determination means.

FIG. 6 shows the display order of the embodiment of the present invention that realizes the same gradation as the display order shown in FIG. 5 in the third reference embodiment. In the display order of this embodiment, the light source drive unit 27 controls the illumination light source 21 so that the illumination light intensity is changed in the order in which the illumination light source 21 irradiates the illumination light with the maximum luminance in the initial stage, and the frame in the second half. The illumination light source 21 is controlled so that the order is reversed. For this reason, since the change in luminance per unit time due to the difference in color is small, it is possible to make it difficult to visually recognize the color flicker depending on the image data. These changes in the display order reduce the number of frames when the minimum one pulse is equivalent to a frame as compared with the pulse width display, so that the load of dynamic calculation by the display order determination means becomes smaller.

According to this embodiment of the present invention , the displacement for displacing the position of the image display element 24 with respect to the optical axis of the image forming optical element 25 in a direction substantially parallel to the pixel array surface for each of a plurality of subfields constituting the image field. And the illumination light control means 27 for making each subfield composed of a plurality of frames and using the illumination light as illumination light having different intensity profiles in each frame. Can be given.

Figure 7 is a timing chart showing an example of operation of the fourth reference embodiment of the present invention.

In the fourth reference embodiment , the piezoelectric element 30 is controlled by the piezoelectric element drive unit 31 to displace the liquid crystal panel 24, so that the x-direction position of the liquid crystal panel 24 is two of x0 and x1, as shown in FIG. The position in the y direction of the liquid crystal panel 24 takes two positions, y0 and y1, and by this combination, the position (x, y) of the liquid crystal panel 24 is (x1, y1), (x1) in the period of one field. , Y0), (x0, y1), and (x0, y0) are sequentially displaced, and these positions are respectively positions in the four subfields SF1 to SF4 constituting one field.

In the fourth reference embodiment, the configuration other than the liquid crystal panel 24 is configured in substantially the same manner as the first reference configuration, and the liquid crystal panel 24 is configured in the same manner as the liquid crystal panel in the second reference configuration. In the fourth reference embodiment, the configuration other than the liquid crystal panel 24 is configured in substantially the same manner as the first reference configuration, and the liquid crystal panel 24 is configured in the same manner as the liquid crystal panel in the second reference configuration. As a result, the fourth reference form can operate in substantially the same manner as the second reference form, and a specific data line has only one scan line for simplification of description (one scan line). Only). That is, only one specific scanning line of the image display element 24 will be described, but even when the number of scanning lines of one data line is n, the operation is substantially the same as in the second reference embodiment. At this time, it is assumed that there is no delay for one subfield shown in FIG.

  Further, the image data is converted into image data corresponding to the subfield by an image data processing device (not shown) so that one pixel of the image display element 24 is quadrupled in advance, and the image data of the subfield is converted into the image data of the subfield. Correspondingly, it is further divided into three frames in the order of subfields 1, 2, 3, and 4 and is simultaneously input to image data storage means A and B, and image data for one field is input and displayed. The

  As can be seen from FIG. 7, in one subfield, the illumination light from the illumination light source 21 has three frames of illumination light intensity of red (hereinafter referred to as G), green (hereinafter referred to as G), and blue (hereinafter referred to as B). The image display element 24 is irradiated while changing in order, and the image display element 24 performs binary spatial light modulation by turning on and off the illumination light in each frame, resulting in eight colors in one subfield. Multi-color image display. For example, by making the image data of each frame into the image data as shown in FIG. 7, the fields 1, 2, 3, and 4 display white, black, red, and blue-green colors, respectively.

Further, in this reference embodiment, each frame is further divided into subframes, and the gradation of each color is displayed in this subframe, so that full color display can be performed. Since these constrained image display device, it is preferable that the third referential embodiment and by operating similarly display the grayscale. For normal full color display, display of 64 gradations or more for every three colors is preferable. When the video rate is 60 Hz, it is 60 × 3 × 6 × 4 = 4.34 kHz in the case of 64 gradations and a 4-fold increase in pixels. However, field sequential is easy to feel color flicker at the normal video rate. In order to prevent the image from being visually recognized, it is further doubled to 8.64 kHz, that is, close to the lower limit of the ferroelectric liquid crystal depending on the applied voltage of the pixel, but the displayable range.

  In addition, since the image display element in which the micromirror is formed on the silicon has a response speed several times faster than this, not only full color display with less flicker by 4 times pixel multiplication but also 9 times pixel multiplication is possible. Full color display with less flicker is also possible.

In the image display device that multiplies the pixel, the effective position of the pixel is displaced by changing the position of the image display element or the positional relationship between the image display element and the lens for enlargement. It is necessary to accurately control at a position of 1/2 or 1/3 of the pixel with an accuracy within 1/4 or 1/6 of the original pixel. If the original pixels are 10 μm apart, this accuracy corresponds to within 2.5 μm. In order to realize this with a three-panel image display device with R, G and B liquid crystal panels, it is very difficult to assemble with mechanical accuracy compared to the case of normal resolution, and is not practical. Cost is increased and long-term reliability with respect to transportation, vibration, etc. is reduced. However, by adopting the configuration as in the fourth embodiment, it can be realized using a single-panel type liquid crystal panel, so adjustment of about 2 μm class is unnecessary, and the cost can be reduced and the reliability is greatly improved. To do. Furthermore, since the splitting optical system of the illumination light source is unnecessary, it becomes possible to reduce the size and weight.

The order of the subfields and their frames in the first field of the fourth reference form is not limited to the order shown in FIG. 7, and the luminance flicker, color flicker, spatial flicker, data processing and data transfer load, etc. are reduced. Therefore, the image data may be appropriately changed. This may be in a specific order in advance, but a display order determining means for determining an appropriate display order from the content of the image data of one pixel or the image data of the peripheral pixels and all the pixels is added, and this display is performed. You may determine dynamically by an order determination means.

FIG. 8 shows another display order for realizing the same display color as the display order shown in FIG. 7 in the fourth reference embodiment. In this display order, the light source drive unit 27 controls the illumination light source 21 so that the illumination light source 21 initially emits green illumination light having a high relative visibility, and the frame order is reversed in the second half. The illumination light source 21 is controlled so that For example, when the response speed of the green light source is fast, the limit of the response speed of the illumination light can be reduced by collectively irradiating the green illumination light as shown in FIG.

According to the fourth reference embodiment, the displacement for displacing the position of the image display device 24 in a direction substantially parallel to the pixel array surface with respect to the optical axis of the image-forming optical element 25 for each of a plurality of subfields constituting the image field And the illumination light control means 27 is configured such that each subfield is composed of a plurality of frames and the illumination light has a wavelength spectrum different from each other in each frame, so that the cost is low and the energy saving performance is high. An enlarged image of resolution can be provided.

It is the schematic which shows the 1st reference form of this invention . It is sectional drawing which shows an example of the liquid crystal panel unit of the said 1st reference form. It is a figure which shows the outline at the time of expanding and observing the pixel of the liquid crystal panel of the said 1st reference form. It is a timing chart which shows an example of operation of the 2nd reference form of the present invention . It is a timing chart which shows an example of operation of the 3rd reference form of the present invention . It is a timing chart which shows the display order of the embodiment of the present invention . It is a timing chart which shows an example of operation of the 4th reference form of the present invention . It is a timing chart figure which shows the other display order of the 4th reference form. 1 is a schematic diagram showing an image display device described in Patent Document 1. FIG. FIG. 10 is a schematic diagram showing another image display device described in Patent Document 2. It is a figure for demonstrating the other image display apparatus of patent document 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Illumination light source 22 Diffusing plate 23 Condenser lens 24 Liquid crystal panel 25 Projection lens 26 Screen 27 Light source drive part 28 Drive part which drives a liquid crystal panel 29 Support body 30 Piezoelectric element 31 Piezoelectric element drive part 32 Liquid crystal panel unit 33 Holding member

Claims (1)

In an image display apparatus comprising: an illuminating unit that emits illumination light; and an image display element having a plurality of pixels that spatially modulate the illumination light, and an output image of the image display element is displayed by an image forming optical element.
The position of the image display element with respect to the optical axis of the image forming optical element is displaced in a direction substantially parallel to the pixel array surface for every four subfields from the first subfield to the fourth subfield constituting the image field. The first subfield from the first subfield to the fourth subfield is composed of only the first frame, and each subsequent subfield is composed of three frames from the second frame to the fourth frame , illumination light is a sequentially with 8,4,2,1 the fourth frame or the intensity profile from the first frame, and, initially, from the first sub-field to the fourth sub-field disposed only the first frame, Thereafter, a first subfield of the second subfield, respectively, in order only three frames from the second frame to the fourth frame And location, then the third sub-field the fourth frame, the third frame and the second sub-field arranged in the order of three frames of the second frame and arranged in reverse frame order, then, By arranging three frames from the second frame to the fourth frame in order in the fourth subfield, the position of the image display element when the position of the image display element is displaced from the second subfield to the third subfield is increased. An image display device comprising illumination light control means for making illumination light having the same luminance in the second subfield and the third subfield.

Images