JP2020071480A - Image projection device - Google Patents

Abstract

To make gaps between pixels of a projected image hardly visible.SOLUTION: An image projection device 1 projects image light to display a projected image. The device includes: optical modulation elements 136R, 136G, and 136B that modulate incident light to generate the image light; and shift means 2 that changes an optical path of the image light and thereby shifts a plurality of pixels arranged in two directions orthogonal to each other in the projected image to the same direction. Control means 3 controls the shift means to shift the plurality of pixels by the maximum shift amount of 1/2 or more of an arrangement pitch for every predetermined period while shifting the plurality of pixels so that their shift amounts are 1/2 or more of the width of a gap between adjacent pixels and 1/3 or less of the arrangement pitch of the pixels within the predetermined period in at least one of the two directions.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image projection apparatus (hereinafter referred to as a projector) that projects an image formed by light modulated by a light modulation element onto a projection surface such as a screen.

  In the projector as described above, if there is a region where light is not modulated between the pixels of the light modulation element, a gap is formed between the pixels of the projected image, and the smoothness of the projected image deteriorates. Patent Documents 1 and 2 disclose a projector in which a pixel is enlarged by a microlens provided between a light modulation element and a screen to fill a gap between pixels in a projected image.

JP, 6-337433, A JP, 7-191310, A

  However, in the projectors disclosed in Patent Documents 1 and 2, it is necessary to prepare a large number of fine microlens lenses and dispose them with high accuracy at positions corresponding to the pixels of the light modulation element.

  The present invention provides a projector capable of making a gap between pixels of a projected image less visible with a simpler configuration.

  An image projection apparatus according to one aspect of the present invention projects image light to display a projected image. The device shifts a plurality of pixels arranged in two directions orthogonal to each other in a projected image by changing a light modulation element that modulates incident light to generate image light and an optical path of the image light. And means for controlling the shift means. In at least one of the two directions, the control means sets the shift amount of the plurality of pixels to 1/2 or more of the width of the gap between the pixels adjacent to each other and 1/3 or less of the arrangement pitch of the pixels. While shifting within the predetermined period, the shift means is controlled so as to shift by a maximum shift amount of ½ or more of the arrangement pitch for each predetermined period.

  An image projection apparatus as another aspect of the present invention projects image light to display a projected image. The apparatus modulates incident light to generate image light and a plurality of pixels arranged in two directions orthogonal to each other in a projected image in the same direction by changing an optical path of the image light. It has shift means for shifting and control means for controlling the shift means. The light modulation elements are driven using the same image data within a predetermined period. The control means uses image data different from the image data for each predetermined period so as to shift the plurality of pixels by ½ pixel for each predetermined period while shifting the plurality of pixels within the predetermined period. It is characterized in that the shift means is controlled.

  According to the present invention, it is possible to make a gap between pixels of a projected image less visible with a simpler configuration.

FIG. 1 is a diagram showing a configuration of a projector that is an embodiment of the present invention. FIG. 6 is a diagram illustrating a pixel shift device according to an example. The figure which shows the conventional pixel shift. FIG. 4 is a diagram showing pixel shift in the first embodiment. The figure which shows the shift of the pixel in a comparative example. FIG. 8 is a diagram showing pixel shift in the second embodiment. The figure which shows the experimental result of Examples 1 and 2. FIG. 8 is a diagram showing pixel shift in Examples 3 and 4. FIG. 16 is a diagram showing a pixel shift device and a pixel shift device according to an eighth embodiment. FIG. 16 is a diagram showing pixel shift in Example 9.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the configuration of a projector (image projection apparatus) 1 as an embodiment of the present invention. The projector 1 includes a light source unit 11, a color separation / combination unit 13, and a projection lens 15.

  The light source unit 11 includes a light source 111, a reflector 112, a first lens array 113, a second lens array 114, a polarization conversion element 115, and a condenser lens 116. The light source 111 is a discharge lamp such as an ultra-high pressure mercury lamp or a halogen lamp. However, as the light source 111, a light emitting diode (LED), a laser diode (LD) and a phosphor may be used. The reflector 112 reflects the light emitted from the light source 111 in a direction different from the direction of the first lens array 113 and directs it toward the first lens array 113.

  White light from the light source 111 is divided into a plurality of light fluxes by the first lens array 113, passes through the second lens array 114, and is condensed in the vicinity of the polarization conversion element 115. The polarization conversion element 115 converts unpolarized light from the light source 111 into linearly polarized light having a predetermined polarization direction. The plurality of light beams emitted from the polarization conversion element 115 are superposed by the condenser lens 116 and illuminate the light receiving surface of each light modulation element described later with a uniform illuminance distribution.

  The color separation / combination unit 13 includes a first dichroic mirror 131, a second dichroic mirror 132, three mirrors 133, R (red), G (green), and B (blue) light modulators 136R, 136G, 136B, and a composite prism. It has a (dichroic prism) 137. Further, the color separation / synthesis unit 13 has a pixel shift device 2 as a shift means. The projector 1 is provided with a panel control unit (not shown) that drives the light modulation elements 136R, 136G, and 136B, and a shift control unit 3 as a control unit that controls the pixel shift device 2.

  The first dichroic mirror 131 reflects the G component (hereinafter referred to as G light) of the white light from the light source unit 11 and transmits the R component (hereinafter referred to as R light) and the B component (hereinafter referred to as B light). Let The reflected G light is reflected by the mirror 133 and guided to the G light modulation element 136G. The second dichroic mirror 132 reflects the R light of the R light and the B light from the first dichroic mirror 131 and transmits the B light. The reflected R light is guided to the R light modulation element 136R. The B light transmitted through the second dichroic mirror 132 is reflected by the mirror 133 and guided to the B light modulation element 136B.

  The R, G, and B light modulation elements 136R, 136G, and 136B are configured by liquid crystal panels and digital micromirror devices, and are driven based on a video signal input to the projector 1 from the outside. As a result, the R, G, and B light modulation elements 136R, 136G, and 136B modulate the incident R light, G light, and B light, respectively, and generate R image light, G image light, and B image light. The liquid crystal panel may be a transmissive type as shown in the drawing or a reflective type. The R image light, the G image light, and the B image light enter the combining prism 137.

  The combining prism 137 reflects the incident G image light and the B image light and transmits the incident R image light to combine the R image light, the G image light, and the B image light to synthesize a full-color image light (hereinafter, The image light is generated and guided to the pixel shift device 2. The pixel shift device 2 performs pixel shift described later with respect to image light. The projection lens 15 magnifies and projects the image light from the pixel shift device 2 onto a projection surface such as a screen (not shown). As a result, the projection image (video) formed by the projection light is displayed on the projection surface.

  The projector of this embodiment has R, G, and B light modulation elements that modulate R light, G light, and B light, respectively, but one light modulation is performed for R light, G light, and B light. The elements may be sequentially modulated. Further, color light different from R light, G light, and B light such as infrared light may be projected as the modulation.

  Each of the R, G, B light modulation elements 136R, 136G, 136B (hereinafter also collectively referred to as a light modulation element 136) includes a plurality of pixels that are two-dimensionally arranged in two directions that are orthogonal to each other, that is, a horizontal direction and a vertical direction. (Hereinafter, referred to as a modulation pixel). On the other hand, the projected image is composed of a plurality of pixels (hereinafter, referred to as image pixels) which are two-dimensionally arranged in the horizontal direction and the vertical direction which are two directions orthogonal to each other so as to correspond to the plurality of modulation pixels.

  Each light modulation element 136 may be provided with a region (hereinafter, referred to as a non-modulation region) that does not modulate light between modulation pixels adjacent to each other on the light receiving surface. For example, in a general transmissive liquid crystal panel driven by an active matrix system, a non-modulation region is provided between modulation pixels to arrange a switching element such as a thin film transistor and a signal line for driving the switching element. The same non-modulation region is also present in the reflective liquid crystal panel to some extent. Further, the digital micromirror device has a plurality of micromirrors corresponding to the modulation pixels of the liquid crystal panel, and changes the angle of these mirrors to control the reflection direction (turns on / off the arrival of light on the projection surface). By doing so, the projected image is displayed. In such a digital micromirror device, a gap as a non-modulation region is provided between adjacent mirrors so that the adjacent mirrors do not come into physical contact with each other. Ratio of the area of all the modulation pixels excluding the non-modulation area to the entire light-receiving surface of the light modulation element, in other words, the aperture ratio of the light modulation element (= the length of the modulation pixel vertical side × the length of the horizontal side) / (vertical modulation) The pixel pitch × horizontal modulation pixel pitch)) is about 96% for the reflective liquid crystal panel, about 80% for the digital micromirror, and about 70% for the transmissive liquid crystal panel.

  When the light-receiving surface of the light modulation element has a non-modulation area in this way, gaps (non-display areas where the image is not displayed) corresponding to the non-modulation areas are formed in a grid pattern between the image pixels of the projected image. The pixel shift device 2 is used in the projector 1 of the present embodiment in order to display the smooth projected image by making this grid-like gap difficult to see. The pixel shift device 2 is arranged between the combining prism 137 and the projection lens 15. The pixel shift device 2 changes (shifts) the optical path of the image light emitted from the synthesizing prism 137, so that a plurality (all) of the image pixels two-dimensionally arranged in the two directions in the projection image in the same shift direction. Pixel shift is performed.

  The shift control unit 3 causes the pixel shift device 2 to perform a first pixel shift for displaying a projection image having a higher resolution (for example, a resolution corresponding to 4K) than the resolution of the light modulation element 136 (for example, a resolution corresponding to full high-definition). Then, the second pixel shift for making the gap between the image pixels hard to see can be performed.

  Here, the principle of pixel shift by the pixel shift device 2 will be described with reference to FIGS. Here, one divided period obtained by dividing one frame period of a video signal into a plurality (for example, two) is referred to as one subframe period as a predetermined period. From each of the plurality of frame image signals forming the video signal, subframe image data for driving the light modulation element 136 is generated in each subframe period in accordance with the position of the image pixel in the subframe period. Within each sub-frame period, the light modulation element 136 is driven using the same sub-frame image data.

  In order to perform the first pixel shift, the shift control unit 3 causes the pixel shift device 2 to shift the image pixels by one half of the image pixel pitch (the arrangement pitch of the image pixels) every one subframe period. To control. By driving the light modulation element 136 using the above-described sub-frame image data for each sub-frame period, the resolution of the image projected and displayed can be increased in a pseudo manner. Such a first pixel shift is disclosed in, for example, Japanese Patent Laid-Open No. 2011-203460.

  2A to 2D show a pixel shift device 2 configured so that a light-transmissive parallel flat plate glass 210 can be rotated (inclined) about an axis 230 extending in the XY plane. Is shown. 2 (a) and 2 (b) respectively show the non-inclined state of the parallel flat plate glass 210 as viewed from the X direction and the Z direction orthogonal to the XY plane. 2 (c) and 2 (d) respectively show the tilted state of the parallel flat plate glass 210 viewed from the X direction and the Z direction. In these figures, 250 is a normal line of the plane (light incident surface or light emitting surface) of the parallel plate glass 210. The normal 250 extends in the Z direction when the parallel plate glass 210 is in the non-inclined state, and the normal 250 inclines with respect to the Z direction in the inclined state.

  FIG. 3 shows how the image pixels are shifted on the projection surface (xy plane) in the first pixel shift. 260 indicates the length of one side of the image pixel in the x direction, and 261 indicates the image pixel pitch in the x direction. Reference numeral 262 indicates a length of ½ of the image pixel pitch in the x direction, and reference numeral 263 indicates a gap (non-display area) between adjacent image pixels. Further, 265 indicates an image pixel pitch in the y direction, and 266 indicates a half of the image pixel pitch in the y direction. Reference numeral 270 indicates an image pixel before shifting (first position), and 290 indicates an image pixel after shifting (second position).

  The image light emitted from the combining prism 137 shown in FIG. 1 passes through the parallel flat plate glass 210 shown in FIGS. 2A to 2D from the − side to the + side in the Z direction. At this time, as shown in FIGS. 2A and 2B, when the parallel flat plate glass 210 is in the non-inclined state, the image pixels 270 are projected on the projection surface. On the other hand, as shown in FIGS. 2 (c) and 2 (d), when the parallel flat glass 210 is tilted so as to move the area A in the Z direction + side and the area B in the Z direction − side. The image pixel 290 shifted in the x and y directions (that is, the pixel diagonal direction) with respect to the image pixel 270 is projected on the projection surface.

  The shift amount of the image pixel at this time is determined by the thickness of the parallel plate glass 210 and the tilt angle (opening angle) of the normal line 250 with respect to the Z direction. In FIG. 3, the direction in which the normal line 250 is inclined with respect to the Z direction, in other words, the direction in which the axis 230 extends is set so that the image pixel 270 shifts to the position of the image pixel 290 in the pixel diagonal direction, and the x direction is set. The case where the thickness of the parallel plate glass 210 and the opening angle of the normal line 250 are set so that the shift amounts in the y direction are 1/2 of the image pixel pitches 262 and 266, respectively.

  Specifically, for a light modulation element having a modulation pixel pitch of 3.8 μm in the X direction and the Y direction, a parallel plate glass 210 formed of a glass material BK7 having a refractive index of 1.5 with a thickness of 1 mm is used. By tilting the non-tilted state so that the opening angle becomes 0.23 degrees, the image pixels are shifted by ½ of the image pixel pitch in the x and y directions.

  In the first pixel shift, the parallel plate glass 210 is rotated (swinged) between a non-tilted state and a tilted state for each subframe period, and a projection image is changed between the non-tilted state and the tilted state. Thus, the resolution of the projected image can be pseudo doubled.

  On the other hand, in the second pixel shift, the parallel plate glass 210 is rotated (swinged) between the non-inclined state and the inclined state within one subframe period, and the projection image is changed between the non-inclined state and the inclined state. Not doing so (that is, displaying the same projection image) makes it difficult to see the gap between the image pixels.

  In some cases, there is no first pixel shift but only second pixel shift. In this case, the subframe has the same meaning as one frame.

  Hereinafter, a specific example regarding the second pixel shift will be described.

  FIGS. 4A and 4B show the shift of the image pixels in the second pixel shift in the first embodiment. In this embodiment and other embodiments described later, the image pixel 270 has a square shape, and the four sides extending in the x direction and the y direction have the same length. Further, the widths of the image pixel pitch 261 and the gap 263 between the image pixels 270 in the x direction and the y direction are also equal to each other. In the following description, the projection image displayed on the projection surface by driving the light modulation element 136 using the subframe image data is also referred to as a subframe projection image.

  FIG. 4A shows a state in which the image pixel 270 is shifted by 1/2 (273) of the width 272 of the gap 263 in the x direction and the y direction (image pixel 271 after the shift). FIG. 4B shows a state (image pixel 274 after shift) in which the image pixel 270 is shifted by 1/3 (264) of the image pixel pitch 261 (width 272 of the gap 263 or more). Reference numeral 277 shows a pixel shift locus in the pixel diagonal direction from the image pixel 270 to the position of the image pixel 274.

  The shift control unit 3 causes the parallel plate glass 210 to make one reciprocating rotation between the non-inclined state and the inclined state within one subframe period in order to cause the pixel shift device 2 to perform the second pixel shift. When the frame rate of the video signal is 60 fps and each frame period is divided into two, one subframe period is 1/60 fps / 2 = 8.3 ms. Assuming that the transition time required for the parallel flat glass 210 to rotate from one of the non-inclined state and the inclined state to the other is 1 ms, the parallel flat glass 210 makes one reciprocating rotation between the non-inclined state and the inclined state. Therefore, a round trip transition time of 2 ms is required. In the present embodiment, the same sub-frame image is projected while the parallel flat glass 210 stops in the non-inclined state and the inclined state (8.3-2) /2=3.15 ms, and each transition time is 1 ms. Do not project the sub-frame image during the period.

  As described above, in this embodiment, the maximum shift amount of the image pixel 270 in each of the x direction and the y direction is 1/2 or more of the width 272 of the gap 263 and 1/3 or less of the image pixel pitch 261. Then, the reciprocal pixel shift is performed within one sub-frame period to shift back to the original position. Then, the same pixel shift is performed in each subsequent sub-frame period.

  Since the aperture ratio of the transmissive liquid crystal panel is approximately 70% as described above, in the transmissive liquid crystal panel for 4K with the modulation pixel pitch of 3.80 μm, one side of the modulation pixel is 3.19 μm, and The width of the non-modulation area between them is 0.61 μm. The light from the modulation pixel of the transmissive liquid crystal panel is equal to or more than 1/2 (0.61 / 2 = 0.305 μm) of the width of the non-modulation region and 1/3 of the modulation pixel pitch (3.80 / 3 = 1. 27 μm) or less in order to shift the maximum shift amount, the parallel flat plate glass 210 formed by the glass material BK7 having a refractive index of 1.5 with a thickness of 1 mm has a maximum of 0.07 degrees or more and 0.46 degrees or less. It may be rotated so as to incline within the range of the opening angle.

  The second pixel shift described above makes it difficult to see the grid-shaped gaps between the image pixels in the projected image, and a smooth projected image can be displayed. FIG. 7A shows an experimental result in which the relationship between the shift amount with respect to the width of the gap between the image pixels and the smoothness (sensory evaluation value) of the projected image felt by the observer is examined. As can be seen from FIG. 7A, when the image pixels are shifted by a shift amount of ½ (= 0.5) or more of the gap width, the projected image is larger than when shifted by a smaller shift amount. Improves the smoothness of.

  Therefore, in the second pixel shift, the pixel shift device 2 is driven so that the maximum shift amount of the image pixel is ½ or more of the gap width of the image pixel in each of the x direction and the y direction (parallel plate). It is desirable to rock the glass 210).

  Further, as a comparative example, as shown in FIG. 5, it is possible to make the gap 263 difficult to see even if the maximum shift amount of the image pixel 270 is set to 1/2 (267) of the image pixel pitch 261. However, when the image pixel 270 is shifted over the gap 263 in this way, the amount of overlap between the image pixel 270 and the image pixel 280 after the shift increases, which leads to a reduction in the resolution of the projected image. FIG. 7B shows an experimental result in which the relationship between the shift amount with respect to the image pixel pitch and the resolution (sensory evaluation value) felt by the observer is investigated. As can be seen from FIG. 7A, when the image pixels are shifted by a shift amount of ⅓ (= 0.33) or less of the image pixel pitch 261, the solution is larger than when shifting by a larger shift amount. It is possible to suppress deterioration of image quality.

  Therefore, in the second pixel shift, it is desirable to drive the pixel shift device 2 such that the maximum shift amount of the image pixel is 1/3 or less of the image pixel pitch in each of the x direction and the y direction.

  In this embodiment, the case where the pixel shift device 2 is controlled to shift the image pixels within one sub-frame period has been described, but the pixel shift device 2 is controlled to shift the image pixels within one frame period (predetermined period). You may. In this case, the light modulation element 136 is driven using the same image data within one frame period.

  Here, the same image data is one set of RGB gradation. In the display method of one set of RGB gradations, each color of RGB may be displayed at the same time, or may be displayed by color time division. Regarding the relationship between the same image data and the shift position, the same image data may be displayed even if the shift position is changed, or the shift position may be changed in a period shorter than the time for displaying the same image data.

  FIG. 5 shows a state (image pixel 280 after the shift) in which the image pixel 270 is shifted in the x direction and the y direction by the width 272 of the gap 263 due to the second pixel shift in the second embodiment. In this embodiment, the image pixel 270 is shifted so that the maximum shift amount in the x direction and the y direction is not less than the width 272 of the gap 263 and not more than 1/3 of the image pixel pitch 261 and is returned to its original position. The reciprocating pixel shift for returning is performed within one sub-frame period. Then, the same pixel shift is performed in each subsequent sub-frame period.

  If the parallel plate glass 210 formed of the glass material BK7 having a refractive index of 1.5 and having a thickness of 1 mm is rotated so as to be tilted within the range of the maximum opening angle of 0.14 degrees or more and 0.46 degrees or less. Good.

  Due to the second pixel shift described above, the grid-like gaps between the image pixels in the projected image are almost invisible, and a smoother projected image can be displayed as compared with the first embodiment. As shown in FIG. 7A, when the image pixels are shifted by a shift amount equal to or larger than the width of the gap (= 1), the smoothness of the projected image is further improved as compared with the case where the shift amount is smaller. To do.

  FIG. 8A shows a case where the image pixel is shifted to three positions in the pixel diagonal direction within one subframe period by the second pixel shift in the third embodiment. A in the figure is the first position (first position), which is the position when the parallel flat glass 210 is in the non-inclined state. B and C are the second and third positions (second position), respectively, and are the positions when the parallel plate glass 210 is in the state of being inclined in one direction and the other direction from the non-inclined state. The positions B and C are positions that are shifted from the position A by ½ of the width of the gap between the image pixels in the x direction and the y direction. The shift direction of the image pixel between the position A and the position B and the shift direction of the image pixel between the position A and the position C are the same one direction (linear direction).

  In this embodiment, the parallel plate glass 210 is rotated (swinged) so as to shift the image pixels in the order of A → B → A → C → (A in the next subframe period) within one subframe period. As described above, when one frame period is divided into two when the frame rate of the video signal is 60 fps, one subframe period is 8.3 ms. Assuming that the transition time required for the parallel flat glass 210 to rotate from one of the non-inclined state and the inclined state to the other is 0.5 ms, the parallel flat glass 210 rotates four times between the non-inclined state and the inclined state. In order to do so, 2.0 ms is required. In the present embodiment, the parallel plate glass 210 is stopped in the non-tilted state and the respective tilted states (that is, the image pixels are at positions A, B, C) (8.3-2) / 4 = 1.58 ms. To do. In this case, the number of times the gap between the image pixels is filled can be increased twice in one frame period, and a smoother image can be obtained.

  In this embodiment, the case where the distance between the positions A and B and the distance between the positions A and C are equal to each other has been described. However, these distances may be different from each other, and are appropriate according to the aspect ratio of the image pixels. You can choose to. Further, in the present embodiment, the case where the number of positions where the image pixels shift within one sub-frame period is three has been described, but the positions may be shifted to a larger number of positions.

  FIG. 8B shows a case where the image pixel is shifted to three positions in the pixel diagonal direction within one sub-frame period by the second pixel shift in the fourth embodiment. Similar to the third embodiment, A in the drawing is the first position, which is the position when the parallel flat glass 210 is in the non-inclined state. B and C are the second and third positions, respectively, and are the positions when the parallel plate glass 210 is in a state of being inclined in one direction and the other direction from the non-inclined state. However, the positions B and C are positions shifted from the position A by the width of the gap between the image pixels in the x direction and the y direction. The shift direction between the position A and the position B is different from the shift direction between the position A and the position C.

  Also in this embodiment, the parallel plate glass 210 is rotated (swinged) so that the image pixels are shifted in the order of A → B → A → C → (A in the next sub-frame period) every frame period. However, in this embodiment, the stop time at the position of the image pixel is set to 0.8 times that in the fourth embodiment, and the stop time at the positions B and C is set to 1.2 times that in the fourth embodiment. The glass 210 is rotated.

  As described above, when one frame period is divided into two when the frame rate of the video signal is 60 fps, one subframe period is 8.3 ms. Assuming that the transition time required for the parallel flat glass 210 to rotate from one of the non-inclined state and the inclined state to the other is 0.5 ms, the parallel flat glass 210 rotates four times between the non-inclined state and the inclined state. In order to do so, 2.0 ms is required. In this embodiment, while the parallel plate glass 210 is stopped for 1.58 × 0.8 = 1.26 ms in the non-tilted state (that is, the image pixel is at the position A) and each inclined state (that is, the image pixel is in the position). In B and C), the same frame projection image is displayed while it is stopped for 1.58 × 1.2 = 1.90 ms, and the subframe projection image is not displayed during each transition time 0.5 ms.

  As described above, in this embodiment, the time when the image pixel stops at the position A which is the center of the shift range is longer than the time when the image pixel stops at the positions B and C which are the ends of the shift range. As a result, the uniformity of the brightness when the brightness of the image pixels is integrated over time in one sub-frame period is further improved as compared with the third embodiment, and a smoother projected image can be obtained.

  In the present embodiment, the case where the stop times at the positions B and C are made equal to each other has been described, but the stop times may be different from each other.

  In Example 1 (FIG. 1), the case where the pixel shift device 2 is arranged between the combining prism 137 and the projection lens 15 has been described, but at least one of the spatial modulation elements 136R, G, and B and the combining prism 137 are described. A pixel shift device may be arranged between them. That is, the pixel shift device may shift the image pixels formed by a part of the color lights included in the image light. Accordingly, the shift amount of the image pixel can be independently controlled for each color light. In particular, by disposing the pixel shift device only for G light that greatly affects the resolution of the projected image, it becomes easy to reduce coloring of the edge portion in the moving image.

  In Examples 1 to 5, the maximum shift amount of image pixels in the second pixel shift (that is, the maximum opening angle of the parallel plate glass 210) may be changeable. Further, the maximum shift amount may be changed for each color light. As a result, it is possible to display a projection image having smoothness according to the content.

  The shift amount of the image pixel in the second pixel shift may be changed according to the projection mode of the projector. As the projection mode, there are a projection mode for displaying a smooth moving image, a projection mode for displaying a sharp line like a presentation material, and the like.

  In the present embodiment, the shift amount (maximum shift amount) preset for each projection mode is stored in the projector, and the shift amount corresponding to the projection mode selected by the user is read and set. As a result, the shift amount suitable for each projection mode is automatically set, and a good projection image can be displayed in each projection mode.

  The shift of the image pixel due to the second pixel shift in the eighth embodiment will be described. In Examples 1 to 4, the case where the image pixels are stopped at a plurality of positions within one frame period has been described. On the other hand, in the present embodiment, as shown in FIGS. 9A to 9C, the image pixels are continuously shifted (circular movement) within one frame period without being stopped. A in the drawing indicates the initial position (first position) of the image pixel. In the following description, the period in which the image pixel makes a circular motion from the initial position A and returns to the initial position A again within one frame period is referred to as one shift period. E, F, and G in the figure respectively indicate the position (second position) of the image pixel at 1/4, 2/4, and 3/4 of one shift period.

  FIG. 9D shows a pixel shift device 2'used in this embodiment. The pixel shift device 2 ′ includes a disk-shaped parallel plate glass 310, a glass holding ring 710 rotatable about an axis 720 extending in the Z direction, and a motor 730 rotating the glass holding ring 710.

  The parallel plate glass 310 is held by the glass holding ring 710 in a posture in which the normal line 350 to the plane is inclined with respect to the axis 720. When the shift control unit 3 controls the rotation of the motor 730 to rotate the glass holding ring 710, the parallel plate glass 310 also rotates around the axis 720 while the normal line 250 is inclined with respect to the axis 720. By continuously rotating the parallel plate glass 310 without stopping, the image pixels formed by the image light transmitted through the parallel plate glass 310 do not stop on the projection surface and are A → E → F → G → ( Circular movement with A → ...). For example, when linear movement is performed at an angle of 45 degrees as in Example 1, a gap between pixels whose appearance is eased and a gap between pixels whose appearance is difficult to appear appear due to this movement. New thin diagonal lines with diagonal directivity are observed. On the other hand, in the circular motion as in the present embodiment, the directivity in the two-dimensional direction corresponding to the motion in the specific direction is lost, and a smoother projected image can be displayed.

  The first pixel shift may be performed while the second pixel shift described in Examples 1 to 8 is performed. That is, the maximum shift is performed while shifting all the image pixels within one sub-frame period such that the maximum shift amount is 1/2 or more of the width of the gap between the image pixels and 1/3 or less of the image pixel pitch. The pixel shift device 2 may be controlled such that the amount is larger than the width of the gap and is 1/2 or more of the image pixel pitch for each subframe period. As a result, it is possible to display a smooth projected image in which a gap is difficult to see in a pseudo high resolution.

  Specifically, as shown in FIG. 10A, the maximum shift amount of all image pixels is 1/2 or more of the width of the gap between the image pixels and 1/3 or less of the image pixel pitch. As described above, the shifts of a and −a are alternately performed within one subframe period so that the period of shifting by a and the period of shifting by −a in one subframe period are half of the subframe period. Further, all the image pixels are alternately shifted by b and -b every one sub-frame period so that the maximum shift amount is ½ or more of the image pixel pitch. Thereby, the gap between the image pixels can be preferably made difficult to see, and an image with high resolution can be displayed.

  In addition, as shown in FIG. 10B, + a of all image pixels is shifted so that the period of shifting by a and the period of shifting by −a in the sub-frame period are each half or less of the sub-frame. The shift of −a may be repeated a plurality of times. This figure shows a case where there are R periods and G periods within one frame period, and shows a case where shifts of + a and −a are repeated a plurality of times in the R periods and G periods.

  Although not shown in the figure, the period of shifting by a or the period of shifting by −a may be longer than the subframe period. Further, although not shown in the figure, the amounts of + a and −a may be randomly changed and temporally integrated to make it difficult to see the gap between the image pixels on average.

  In the first to eighth embodiments, the case where the image shift device 2 (or 2 ') as the shift means provided separately from the liquid crystal panel as the light modulation element is used has been described. However, when a digital micromirror device is used as the light modulation element, the optical path of the image light is changed by changing the angle of the micromirror corresponding to the modulation pixel in the digital micromirror device to shift the image pixel. Is possible. In this case, the digital micromirror device also serves as the shift means.

  In Examples 1 to 8, the pixel shift device has a configuration in which the optical path of the image light is changed by swinging or rotating the parallel plate glass, but other pixel shift devices may be used. .. For example, a pixel shift device capable of changing the optical path of the image light by changing the refractive index for the image light may be used.

  The embodiments described above are merely representative examples, and various modifications and changes can be made to the embodiments when implementing the present invention.

1 Projector 136R, 136G, 136B Light modulation element 2, 2'Pixel shift device 210 Parallel plate glass 261 Image pixel pitch 270, 290 Image pixel

Claims (12)

An image projection device for projecting image light to display a projected image,
A light modulation element that modulates incident light to generate the image light,
Shift means for shifting a plurality of pixels arranged in two directions orthogonal to each other in the projection image by changing the optical path of the image light;
A control means for controlling the shift means,
In at least one of the two directions, the control unit causes the shift amounts of the plurality of pixels to be 1/2 or more of a width of a gap between the pixels adjacent to each other and 1 / of an array pitch of the pixels. The image projection apparatus is characterized in that the shift means is controlled so as to shift by a maximum shift amount of ½ or more of the array pitch for each predetermined period while shifting within a predetermined period so as to be 3 or less. .   The image projection according to claim 1, wherein a shift period of the pixel to be shifted within the predetermined period is half or less of a predetermined period, and there are a plurality of shift periods of the pixel that can be shifted within the predetermined period. apparatus   The shift amount of the pixel shifted within the predetermined period is set to a random amount within a range of ½ or more of the width of the gap between the pixels adjacent to each other and ⅓ or less of the arrangement pitch of the pixels. The image projection apparatus according to claim 1, wherein the image projection apparatus according to claim 1. The light modulation element is driven using the same image data within the predetermined period,
The image projection apparatus according to claim 1, wherein the control unit controls the shift unit so as to shift the plurality of pixels within the predetermined period.   5. The image projection apparatus according to claim 1, wherein the control unit controls the shift unit to shift the plurality of pixels in the two directions within the predetermined period. ..   The image projection apparatus according to any one of claims 1 to 5, wherein the maximum shift amount is equal to or larger than the width of the gap.   7. The image projection apparatus according to claim 1, wherein the shift unit shifts the pixel formed by a part of the color light included in the image light. ..   The image projection apparatus according to claim 7, wherein the control unit changes the maximum shift amount for each color light included in the image light.   The image projection apparatus according to any one of claims 1 to 8, wherein the control unit changes the maximum shift amount according to a projection mode set in the image projection apparatus. The control means shifts the plurality of pixels while stopping at each of a plurality of positions,
The image projection apparatus according to claim 1, wherein a stop time of the plurality of pixels at any one of the plurality of positions is different from a stop time at another position. .   The image projection apparatus according to claim 1, wherein the control unit controls the shift unit so as to continuously shift the plurality of pixels without stopping the plurality of pixels. An image projection device for projecting image light to display a projected image,
A light modulation element that modulates incident light to generate the image light,
Shift means for shifting a plurality of pixels arranged in two directions orthogonal to each other in the projection image in the same direction by changing the optical path of the image light;
A control means for controlling the shift means,
The light modulation element is driven using the same image data within a predetermined period,
The control means shifts the plurality of pixels within the predetermined period and shifts the plurality of pixels by ½ pixel for each predetermined period, which is different from the image data for each predetermined period. An image projection apparatus, characterized in that the shift means is controlled using image data.