Projection-type image display device

Abstract

A first subframe includes: a first bit plane that corresponds to a first bit; a subsequent second bit plane that corresponds to a second bit; and a subsequent third bit plane that corresponds to a third bit. A second subframe includes a fourth bit plane that corresponds to the third bit, a fifth bit plane that corresponds to the second bit; and a subsequent sixth bit plane that corresponds to the first bit. A control device (11) generates low-power illumination light with a light source device (12) when at least some of mirrors (14m) are controlled according to the second or fifth bit plane. The control device (11) generates high-power illumination light with the light source device (12) when all of the mirrors (14m) are controlled according to another bit plane.

Description

Projection-type image display device

[0001] The present disclosure relates to a control device and control method for a projection-type image display device, and a projection-type image display device.

[0002] A variety of display devices have been proposed for displaying digital or moving images.

[0003] For example, Patent Document 1 discloses a display control device that reduces the occurrence of dynamic false contours when displaying a digital grayscale image.

[0004] Japanese Patent Application Laid-Open No. 2002-040983

[0005] In digital or video images, dithering is sometimes used to create more colors using a limited number of colors. Dithering is the process of generating additional colors and tones from an existing palette by interspersing pixels of existing colors.

[0006] However, pixels having pixel values ​​changed by dithering may be perceived as noise, and therefore a display device that is less likely to produce perceptible noise even when dithering is performed is desired.

[0007] An object of the present disclosure is to provide a control device and a control method for a projection-type video display device that can control the projection-type video display device so as to reduce the occurrence of perceptible noise even when dithering is performed. Another object of the present disclosure is to provide such a projection-type video display device.

[0008] A control device for a projection-type image display device according to one aspect of the present disclosure is a control device for a projection-type image display device equipped with a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control device controls the light source device to generate the illumination light at either a first power or a second power lower than the first power, the control device controls the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, each of the plurality of image frames including first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits, each of the first and second sub-frames including a plurality of bit planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order, the first subframe includes a first bit plane corresponding to the first bit, a second bit plane corresponding to the second bit and located immediately after the first bit plane, and a third bit plane corresponding to the third bit and located immediately after the second bit plane; the second subframe includes a fourth bit plane corresponding to the third bit, a fifth bit plane corresponding to the second bit and located immediately after the fourth bit plane, and a sixth bit plane corresponding to the first bit and located immediately after the fifth bit plane; and the control device controls the light source device to generate illumination light having the second power when at least some of the plurality of mirrors are controlled according to the second or fifth bit plane, and controls the light source device to generate illumination light having the first power when all of the plurality of mirrors are controlled according to bit planes different from the second and fifth bit planes.

[0009] According to one aspect of the present disclosure, even when dithering is performed, it is possible to control a projection-type image display device so as to reduce the occurrence of perceptible noise.

[0010] FIG. 1 is a block diagram showing the configuration of a projection-type image display device 1 according to an embodiment. FIG. 2 is a top view showing the configuration of a digital micromirror device 14 of FIG. 1. FIG. 3 is a diagram showing the format of a video signal processed by the projection-type image display device 1 of FIG. 1. FIG. 4 is a timing chart explaining the operation of a projection-type image display device according to a comparative example. FIG. 5 is a timing chart explaining the operation of the projection-type image display device 1 of FIG. 1. FIG. 6 is a diagram explaining dithering performed by the projection-type image display device according to the comparative example. FIG. 7 is a diagram explaining dithering performed by the projection-type image display device 1 of FIG. 1.

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. However, in some cases, more detailed explanations than necessary will be omitted. For example, detailed explanations of already well-known matters and duplicate explanations of substantially identical configurations will be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. Note that components with the same reference numerals have the same functions in each embodiment.

[0012] It should be noted that the present disclosure provides the accompanying drawings and the following description for the understanding of those skilled in the art, and is not intended to limit the subject matter described in the claims.

[0013] 1 is a block diagram showing the configuration of a projection-type image display device 1 according to an embodiment. The projection-type image display device 1 includes a control device 11, a light source device 12, an optical system 13, a digital micromirror device (DMD) 14, and an optical system 15.

[0014] The control device 11 receives a video signal from an external device (not shown) and controls the overall operation of the projection-type image display device 1 based on the video signal.

[0015] The light source device 12 generates illumination light having variable power under the control of the control device 11. The light source device 12 may include, for example, a laser diode. The power of the illumination light may be changed, for example, by changing the magnitude of the current flowing through the laser diode.

[0016] The optical system 13 transmits the illumination light generated by the light source device 12 and makes it incident on the digital micromirror device 14. The optical system 13 includes a combination of multiple optical elements including lenses, prisms, mirrors, filters, and the like.

[0017] The digital micromirror device 14 receives an image signal from the control device 11, and modulates the incident illumination light based on the image signal to generate image light.

[0018] The optical system 15 projects the image light generated by the digital micromirror device 14 onto a screen (not shown). The optical system 15 includes a combination of multiple optical elements, including lenses, prisms, mirrors, filters, and the like.

[0019] 2 is a top view showing the configuration of the digital micromirror device 14 of FIG. 1. The digital micromirror device 14 includes a plurality of mirrors 14m arranged in a two-dimensional array. The plurality of mirrors 14m are controlled to perform two-dimensional scanning in accordance with a video signal. The digital micromirror device 14 has a main scanning direction (x-axis direction) and a sub-scanning direction (y-axis direction).

[0020] The control device 11 controls the light source device 12 to generate illumination light at either a first power or a second power lower than the first power. The control device 11 controls the plurality of mirrors 14m by supplying a video signal to the digital micromirror device 14. When each mirror 14m is turned on, the reflected light from the mirror 14m travels to the optical system 15, and when each mirror 14m is turned off, the reflected light from the mirror 14m travels to an absorbing plate (not shown) inside the projection-type image display device 1.

[0021] [Operation of the Embodiment] FIG. 3 is a diagram showing the format of a video signal processed by the projection-type video display device 1 of FIG.

[0022] The video signal includes a plurality of image frames 21. The image frames 21 may have a frame rate of, for example, 60 Hz.

[0023] Each of the multiple image frames 21 includes sub-frames 22-1 and 22-2 that represent the same image. The image includes multiple pixels, each having a pixel value represented by multiple bits, including at least three bits. In this example embodiment, each pixel has a pixel value represented by 13 bits b0 to b12, where bit b0 is the least significant bit, bit b1 is the bit following bit b0, bit b2 is the bit following bit b1, and so on, with bit b12 being the most significant bit. Corresponding pixels in sub-frames 22-1 and 22-2 have the same pixel value.

[0024] Each of the subframes 22-1 and 22-2 includes a plurality of bit planes corresponding to the plurality of bits of each pixel, arranged in a predetermined temporal order. In this embodiment, each of the subframes 22-1 and 22-2 includes bit planes p0 to p12 corresponding to the bits b0 to b12 of each pixel, respectively. The bit planes p0 to p12 have different time lengths. For example, the bit planes p0 to p12 may each have a time length weighted by a power of 2. In this case, the bit plane p0 has a time length T, the bit plane p1 has a time length T×2, and the bit plane p2 has a time length T×2. ２ and bit plane p3 has a time length T×2 ３ and so on, with bit plane p12 having a time length of T×2 １２ By controlling each mirror 14m in accordance with the bit value of each pixel included in bit planes p0 to p12 having such time lengths, the digital micromirror device 14 performs pulse width modulation of the incident illumination light.

[0025] 3 illustrates a case in which each image frame 21 includes only a single-color image for the sake of simplicity, but the image frame 21 may also include a multi-color image, for example, an RGB image. In this case, each image frame 21 includes two sub-frames representing the same R image, two sub-frames representing the same G image, and two sub-frames representing the same B image. Each of these sub-frames, like the sub-frames 22-1 and 22-2 in FIG. 3, includes a plurality of bit planes corresponding to the multiple bits of each pixel, and arranged in a predetermined temporal order.

[0026] As described above, when dithering a digital image or a moving image, pixels having pixel values ​​changed by dithering may be perceived as noise. In order to make pixels having pixel values ​​changed by dithering less perceptible, it is possible to reduce the power of the illumination light generated by the light source device 12, particularly to reduce the power of the illumination light in only some of the multiple bit planes. However, reducing the power of the illumination light in this manner may cause the following problem, which will be described with reference to FIG. 4.

[0027] FIG. 4 is a timing chart illustrating the operation of the projection-type image display device according to the comparative example.

[0028] The projection display device according to the comparative example has a similar configuration to the projection display device 1 according to the embodiment (see FIG. 1), but operates in a different manner from the projection display device 1 according to the embodiment.

[0029] As shown in FIG. 4, the light source device 12 generates illumination light at either a power W1 or a power W2 lower than the power W1.

[0030] 4 also shows a case where subframes 22-1 and 22-2 include bit planes p0 to p12 arranged in the same temporal order. In each of subframes 22-1 and 22-2, bit plane p0 is located immediately after bit plane p5, and bit plane p8 is located immediately after bit plane p0. The other bit planes are not shown in the figure.

[0031] 4 also shows the operation of mirrors 14m(x,y1) to 14m(x,y8) positioned along a straight line parallel to the sub-scanning direction (direction of the y-axis) of the digital micromirror device 14. Mirrors 14m(x,y1) to 14m(x,y8) are turned on or off according to the bit values ​​of each pixel included in bit planes p5, p0, p8, .... Because the multiple mirrors 14m of the digital micromirror device 14 are controlled to perform two-dimensional scanning, the operation of mirrors 14m(x,y1) to 14m(x,y8) gradually slows down as they move in the sub-scanning direction.

[0032] Assume that bit plane p0 contains bit values ​​related to dithering. To make pixels whose pixel values ​​have been changed by dithering less perceptible, the control device 11 controls the light source device 12 to generate illumination light having power W2 when at least some of the mirrors 14m are controlled according to bit plane p0. Furthermore, the control device 11 controls the light source device 12 to generate illumination light having power W1 when all of the mirrors 14m are controlled according to a bit plane other than bit plane p0. When the mirrors 14m are controlled according to a bit plane other than bit plane p0, for example, bit planes p5 and p8, it is desirable that illumination light having power W1 be incident on each mirror 14m throughout the entire time duration of that bit plane. However, as described above, the operation of the mirrors 14m is gradually delayed as the scanning progresses. Due to this delay, when the mirrors 14m are controlled according to bit planes p5 and p8 adjacent to bit plane p0, illumination light having power W2 is incident on each mirror 14m for part of the time duration of that bit plane. In the example of FIG. 4, reference numerals 31 to 34 indicate time periods during which illumination light having an unintentionally reduced power W2 is incident on each mirror 14m.

[0033] Reference numeral 41 denotes the contribution of bit plane p5 of subframe 22-1 to the image displayed on the screen. Reference numeral 42 denotes the contribution of bit plane p8 of subframe 22-1 to the image displayed on the screen. Reference numeral 43 denotes the contribution of bit plane p5 of subframe 22-2 to the image displayed on the screen. Reference numeral 44 denotes the contribution of bit plane p8 of subframe 22-2 to the image displayed on the screen. When multiple mirrors 14m are controlled in accordance with bit plane p5, the operation of the mirrors 14m is gradually delayed as one progresses in the sub-scanning direction. Due to this delay, the period of time during which illumination light having power W2 is incident on each mirror 14m becomes gradually longer. Therefore, images 41 and 43 become gradually darker as one progresses in the sub-scanning direction. Similarly, when the mirrors 14m are controlled in accordance with bit plane p8, the operation of the mirrors 14m is gradually delayed as the scanning direction progresses, and due to this delay, the time period during which the illumination light having power W1 is incident on each mirror 14m becomes gradually longer. Therefore, the images 42 and 44 become gradually brighter as the scanning direction progresses.

[0034] Reference numeral 51 denotes the composite image of images 41 and 43, i.e., the sum of the contributions of bit plane p5 in sub-frames 22-1 and 22-2. As one moves in the sub-scanning direction, composite image 51 becomes gradually darker. Similarly, reference numeral 52 denotes the composite image of images 42 and 44, i.e., the sum of the contributions of bit plane p8 in sub-frames 22-1 and 22-2. As one moves in the sub-scanning direction, composite image 52 becomes gradually brighter. Thus, as a result of changing the illumination light power, uneven brightness occurs across the image. If image frame 21 contains images of multiple colors, the desired color cannot be generated.

[0035] For the sake of explanation, images 41 to 44 show the case where all mirrors 14m are uniformly turned on. However, even if each mirror 14m is individually turned on or off according to the bit value of each pixel included in a bit plane, uneven brightness will occur across the entire image for the same reasons as those described with reference to FIG.

[0036] In order to solve the problem of uneven brightness, the projection-type image display device 1 according to this embodiment operates as will be described with reference to FIG.

[0037] FIG. 5 is a timing chart illustrating the operation of the projection-type image display device 1 of FIG. 1. According to this embodiment, the control device 11 generates an image frame including subframe 22-2A instead of subframe 22-2 of FIG. 4. Subframe 22-1 of FIG. 5 is the same as subframe 22-1 of FIG. 4. Subframe 22-2A includes bit planes p0 to p12 arranged in a temporal order that is at least partially different from that of subframe 22-1. In subframe 22-2A, bit plane p8 is located immediately before bit plane p0, and bit plane p5 is located immediately after bit plane p0. In subframe 22-2A, bit planes other than bit planes p8, p0, and p5 may be arranged in the same temporal order as subframe 22-1, or may be arranged in a temporal order that is different from that of subframe 22-1.

[0038] Assume that bit plane p0 contains bit values ​​related to dithering. To make pixels having pixel values ​​changed by dithering less perceptible, the control device 11 controls the light source device 12 to generate illumination light having power W2 when at least some of the mirrors 14m are controlled according to bit plane p0. Furthermore, the control device 11 controls the light source device 12 to generate illumination light having power W1 when all of the mirrors 14m are controlled according to a bit plane different from bit plane p0. When the mirrors 14m are controlled according to bit planes p5 and p8 adjacent to bit plane p0, illumination light having power W2 is incident on each mirror 14m for part of the time length of the bit plane, as in the case of FIG. 4 . In the example of FIG. 5 , reference numerals 31, 32, 33A, and 34A denote time periods during which illumination light having an unintentionally reduced power W2 is incident on each mirror 14m.

[0039] Reference numeral 41 denotes the contribution of bit plane p5 of subframe 22-1 to the image displayed on the screen. Reference numeral 42 denotes the contribution of bit plane p8 of subframe 22-1 to the image displayed on the screen. Reference numeral 43A denotes the contribution of bit plane p5 of subframe 22-2A to the image displayed on the screen. Reference numeral 44A denotes the contribution of bit plane p8 of subframe 22-2A to the image displayed on the screen. When the multiple mirrors 14m are controlled in accordance with bit plane p5 of subframe 22-1, the time period during which illumination light having power W2 is incident on each mirror 14m becomes gradually longer as the image advances in the sub-scanning direction. Furthermore, when the multiple mirrors 14m are controlled in accordance with bit plane p5 of subframe 22-2A, the time period during which illumination light having power W1 is incident on each mirror 14m becomes gradually longer as the image advances in the sub-scanning direction. Therefore, image 41 becomes gradually darker and image 43A becomes gradually brighter as the image advances in the sub-scanning direction. Similarly, when the mirrors 14m are controlled in accordance with bit plane p8 of subframe 22-1, the time period during which illumination light having power W1 is incident on each mirror 14m becomes gradually longer as the distance increases in the sub-scanning direction. Furthermore, when the mirrors 14m are controlled in accordance with bit plane p8 of subframe 22-2A, the time period during which illumination light having power W2 is incident on each mirror 14m becomes gradually longer as the distance increases in the sub-scanning direction. Therefore, image 42 becomes gradually brighter and image 44A becomes gradually darker as the distance increases in the sub-scanning direction.

[0040] Reference numeral 51A denotes the composite image of images 41 and 43A, i.e., the sum of the contributions of bit plane p5 in sub-frames 22-1 and 22-2A. The luminance variations in images 41 and 43A in the sub-scanning direction cancel out, resulting in composite image 51A with uniform brightness. Similarly, reference numeral 52A denotes the composite image of images 42 and 44A, i.e., the sum of the contributions of bit plane p8 in sub-frames 22-1 and 22-2A. The luminance variations in images 42 and 44A in the sub-scanning direction cancel out, resulting in composite image 52A with uniform brightness.

[0041] When dithering a video signal, the control device 11 generates a video signal including bit planes p0 to p12 arranged in the time sequence as described with reference to FIG. 5, and controls the light source device 12 and the digital micromirror device 14 in accordance with the timing chart of FIG. 5.

[0042] The power W2 may be, for example, 50% of the power W1. Also, if the image frame 21 includes images of multiple colors, the power of the illumination light may be reduced by different percentages for each color.

[0043] Bit planes p5 and p8 have a longer time length than bit plane p0. The time length of bit planes p5 and p8 may be set, for example, to be longer than the time required to scan the multiple mirrors 14m in the sub-scanning direction of the digital micromirror device 14. In this case, illumination light having power W2 is incident on the digital micromirror device 14 during the time period when the multiple mirrors 14m are controlled according to bit plane p0 and during part of the time period when the multiple mirrors 14m are controlled according to bit planes p5 and p8, and illumination light having power W1 is incident on the digital micromirror device 14 during the other time periods. This allows the power of the illumination light to be reduced without affecting bit planes other than bit planes p0, p5, and p8.

[0044] 6 is a diagram illustrating dithering performed by a projection-type video display device according to a comparative example. When dithering an image 60, for example, the pixel value of pixel 61 is changed. However, due to insufficient bit depth, the difference between the pixel value of pixel 61 and the pixel values ​​of its surrounding pixels is excessively large, and as a result, pixel 61 may be perceived as noise.

[0045] 7 is a diagram illustrating dithering performed by the projection-type image display device 1 of FIG. 1. When dithering image 60A, for example, the pixel value of pixel 61A represented by bit plane p0 corresponding to the least significant bit b0 is changed. Furthermore, when multiple mirrors 14m are controlled in accordance with bit plane p0, light source device 12 is controlled to generate illumination light having reduced power W2. This reduces the difference between the pixel value of pixel 61A and the pixel values ​​of its surrounding pixels compared to the case of FIG. 6, making pixel 61A less perceptible as noise.

[0046] Thus, according to this embodiment, when bit plane p0 includes a bit value related to dithering, the power of the illumination light is reduced when the mirrors 14m are controlled in accordance with bit plane p0, making it difficult to perceive pixels having pixel values ​​changed by dithering. In this way, even when dithering is performed, the projection-type image display device 1 can be controlled so as to reduce the occurrence of perceptible noise.

[0047] Furthermore, according to this embodiment, by generating a video signal so as to cancel out the change in luminance across the sub-frames 22-1 and 22-2, it is possible to change the power of the illumination light without causing unevenness in luminance.

[0048] The projection-type image display device 1 according to this embodiment can be realized with a relatively simple configuration and processing, without significantly increasing costs and processing time.

[0049] Effects of the Embodiment A control device 11 of a projection-type image display device 1 according to an embodiment controls a projection-type image display device 1 equipped with a light source device 12 and a digital micromirror device 14. The digital micromirror device 14 includes a plurality of mirrors 14m arranged in a two-dimensional array and modulates illumination light generated by the light source device 12 and incident on the digital micromirror device 14. The control device 11 controls the light source device 12 to generate illumination light at either a first power or a second power lower than the first power. The control device 11 controls the mirrors 14m by supplying a video signal including a plurality of image frames to the digital micromirror device 14. Each of the plurality of image frames includes first and second subframes representing the same image, and the image includes a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits. Each of the first and second subframes includes a plurality of bit planes corresponding to the plurality of bits of each pixel, the plurality of bit planes being arranged in a predetermined temporal order. The first subframe includes a first bit-plane corresponding to the first bit, a second bit-plane corresponding to the second bit and located immediately after the first bit-plane, and a third bit-plane corresponding to the third bit and located immediately after the second bit-plane. The second subframe includes a fourth bit-plane corresponding to the third bit, a fifth bit-plane corresponding to the second bit and located immediately after the fourth bit-plane, and a sixth bit-plane corresponding to the first bit and located immediately after the fifth bit-plane. The control device 11 controls the light source device 12 to generate illumination light having a second power when at least some of the plurality of mirrors 14m are controlled according to the second or fifth bit-plane. The control device 11 controls the light source device 12 to generate illumination light having a first power when all of the plurality of mirrors 14m are controlled according to bit-planes different from the second and fifth bit-planes.

[0050] With this configuration, even when dithering is performed, the projection-type image display device 1 can be controlled so as to reduce the occurrence of perceptible noise.

[0051] According to the control device 11 of the projection display device 1 according to the embodiment, the second and fifth bit-planes may have a first time length, the first and sixth bit-planes may have a second time length that is longer than the first time length, and the third and fourth bit-planes may have a third time length that is longer than the first time length.

[0052] With this configuration, even when the power of the illumination light is reduced, it is possible to make it less likely that the power will affect bit planes other than the first to sixth bit planes.

[0053] According to the control device 11 of the projection display device 1 according to this embodiment, the mirrors 14m may be controlled to scan two-dimensionally in accordance with a video signal. The second and third time lengths may be set longer than the time length required to scan the mirrors 14m in the sub-scanning direction of the digital micromirror device 14.

[0054] This configuration allows the power of the illumination light to be reduced without affecting other bit planes different from the first to sixth bit planes.

[0055] According to the control device 11 of the projection display device 1 according to the embodiment, the second and fifth bit planes may include bit values ​​related to dithering of the image.

[0056] This configuration makes it possible to perform dithering without causing uneven brightness while making it difficult for perceptible noise to occur.

[0057] The projection-type image display device according to the embodiment includes a light source device 12 , a digital micromirror device 14 , and a control device 11 .

[0058] This configuration makes it possible to make it difficult for perceptible noise to occur even when dithering is performed.

[0059] A control method for a projection-type image display device 1 according to an embodiment includes controlling a projection-type image display device 1 equipped with a light source device 12 and a digital micromirror device 14. The digital micromirror device 14 includes a plurality of mirrors 14m arranged in a two-dimensional array and modulates illumination light generated by the light source device 12 and incident on the digital micromirror device 14. The control method includes generating illumination light with the light source device 12 at either a first power or a second power lower than the first power, and controlling the plurality of mirrors 14m by supplying a video signal including a plurality of image frames to the digital micromirror device 14. Each of the plurality of image frames includes first and second sub-frames representing the same image, and the image includes a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits. Each of the first and second sub-frames includes a plurality of bit planes corresponding to the plurality of bits of each pixel, the plurality of bit planes being arranged in a predetermined temporal order. The first subframe includes a first bit-plane corresponding to the first bit, a second bit-plane corresponding to the second bit and located immediately after the first bit-plane, and a third bit-plane corresponding to the third bit and located immediately after the second bit-plane. The second subframe includes a fourth bit-plane corresponding to the third bit, a fifth bit-plane corresponding to the second bit and located immediately after the fourth bit-plane, and a sixth bit-plane corresponding to the first bit and located immediately after the fifth bit-plane. The control method includes generating illumination light having a second power by the light source device 12 when at least some of the plurality of mirrors 14m are controlled according to the second or fifth bit-plane, and generating illumination light having a first power by the light source device 12 when all of the plurality of mirrors 14m are controlled according to bit-planes different from the second and fifth bit-planes.

[0060] With this configuration, even when dithering is performed, the projection-type image display device 1 can be controlled so as to reduce the occurrence of perceptible noise.

[0061] [Other Embodiments] As described above, the embodiments have been described as examples of the technology disclosed in this application. For this purpose, the accompanying drawings and detailed description have been provided. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, it is also possible to combine the components described in the above embodiments to create new embodiments.

[0062] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings and / or detailed description should not be interpreted as immediately being essential.

[0063] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0064] The bit values ​​related to image dithering are not limited to bit plane p0 corresponding to the least significant bit b0, but may also be included in bits near the least significant bit b0, for example, bit planes p0 to p2 corresponding to bits b0 to b2. As with the case described for bit plane p0 with reference to Figure 5, for bit planes p1 and p2, by generating a video signal that offsets changes in luminance across subframes 22-1 and 22-2, the power of the illumination light can be changed without causing uneven luminance.

[0065] If the bit values ​​for dithering an image are contained in multiple bit planes, the power of the illumination light may be reduced by different percentages for each bit plane.

[0066] When the bit values ​​for image dithering are included in multiple bit planes, the multiple bit planes containing the bit values ​​for image dithering may be adjacent in time. In this case, the first subframe includes a first bit plane corresponding to the first bit, a first group of bit planes including at least a first bit plane corresponding to the second bit, and second and third bit planes corresponding to the third bit, and positioned immediately after the first bit plane, and a fourth bit plane corresponding to the fourth bit and positioned immediately after the first group of bit planes. The second subframe includes a fifth bit plane corresponding to the fourth bit, a second group of bit planes including at least a sixth and seventh bit planes corresponding to the second and third bits, and positioned immediately after the fourth bit plane, and an eighth bit plane corresponding to the first bit and positioned immediately after the second group of bit planes. The control device 11 controls the light source device 12 to generate illumination light having a second power W2 when at least some of the multiple mirrors are controlled according to the first or second group of bit planes. When all of the mirrors are controlled according to bit planes different from the bit planes included in the first and second bit plane groups, the control device 11 controls the light source device 12 to generate illumination light having a first power W1. This makes it possible to control the projection-type image display device 1 so as to reduce the occurrence of perceptible noise, even when multiple temporally adjacent bit planes contain bit values ​​related to image dithering.

[0067] Each image frame may include more than two sub-frames.

[0068] If each image frame includes an odd number of sub-frames, the video signal may be generated to offset the change in luminance across one sub-frame included in the first image frame and one sub-frame included in the second image frame.

[0069] Instead of a single set of bit planes representing an image, each subframe may contain multiple sets of bit planes representing the same image. In this case, by generating a video signal that offsets luminance changes in a single subframe, the power of the illumination light can be changed without causing uneven luminance.

[0070] If none of the bit planes contains bit values ​​related to image dithering, the control device 11 may control the light source device 12 to generate illumination light having a constant power throughout each subframe.

[0071] Summary of the embodiment According to a control device for a projection-type video display device according to a first aspect of the present disclosure, there is provided a control device for a projection-type video display device including a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control device controls the light source device to generate the illumination light at either a first power or a second power lower than the first power, the control device controls the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, each of the plurality of image frames including first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits, each of the first and second sub-frames including a plurality of bit planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order, the first subframe includes a first bit plane corresponding to the first bit, a second bit plane corresponding to the second bit and located immediately after the first bit plane, and a third bit plane corresponding to the third bit and located immediately after the second bit plane; the second subframe includes a fourth bit plane corresponding to the third bit, a fifth bit plane corresponding to the second bit and located immediately after the fourth bit plane, and a sixth bit plane corresponding to the first bit and located immediately after the fifth bit plane; and the control device controls the light source device to generate illumination light having the second power when at least some of the plurality of mirrors are controlled according to the second or fifth bit plane, and controls the light source device to generate illumination light having the first power when all of the plurality of mirrors are controlled according to bit planes different from the second and fifth bit planes.

[0072] According to a control device relating to a second aspect of the present disclosure, in the control device relating to the first aspect, the second and fifth bit planes have a first time length, the first and sixth bit planes have a second time length longer than the first time length, and the third and fourth bit planes have a third time length longer than the first time length.

[0073] According to the control device of the third aspect of the present disclosure, in the control device of the second aspect, the plurality of mirrors are controlled to scan two-dimensionally in accordance with the video signal, and the second and third time lengths are set longer than the time length required to scan the plurality of mirrors in the sub-scanning direction of the digital micromirror device.

[0074] According to a fourth aspect of the present disclosure, in the control device according to one of the first to third aspects, the second and fifth bit planes include bit values ​​related to dithering of the image.

[0075] According to a fifth aspect of the present disclosure, there is provided a control device for a projection-type image display device comprising a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control device controls the light source device to generate the illumination light at either a first power or a second power lower than the first power, the control device controls the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, each of the plurality of image frames including first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to fourth bits, each of the first and second sub-frames including a plurality of bit planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order, the plurality of bit planes comprising: a first bit plane corresponding to the first bit; the second subframe includes: a first bit-plane group including at least second and third bit-planes corresponding to the second and third bits and located immediately after the first bit-plane; and a fourth bit-plane corresponding to the fourth bit and located immediately after the first bit-plane group; the second subframe includes: a fifth bit-plane corresponding to the fourth bit; a second bit-plane group including at least sixth and seventh bit-planes corresponding to the second and third bits and located immediately after the fourth bit-plane; and an eighth bit-plane corresponding to the first bit and located immediately after the second bit-plane group; and the control device controls the light source device to generate illumination light having the second power when at least some of the plurality of mirrors are controlled in accordance with the first or second bit-plane group;When all of the plurality of mirrors are controlled according to a bit plane different from the bit planes included in the first and second bit plane groups, the light source device is controlled to generate illumination light having the first power.

[0076] A projection-type image display device according to a sixth aspect of the present disclosure includes: a light source device; a digital micromirror device; and a control device according to one of the first to fifth aspects.

[0077] According to a seventh aspect of the present disclosure, there is provided a method for controlling a projection-type video display device including a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control method comprising: generating the illumination light with the light source device at either a first power or a second power lower than the first power; and controlling the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, wherein each of the plurality of image frames includes first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits; and each of the first and second sub-frames includes a plurality of bit-planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order; the first subframe includes a first bit plane corresponding to the first bit, a second bit plane corresponding to the second bit and located immediately after the first bit plane, and a third bit plane corresponding to the third bit and located immediately after the second bit plane; the second subframe includes a fourth bit plane corresponding to the third bit, a fifth bit plane corresponding to the second bit and located immediately after the fourth bit plane, and a sixth bit plane corresponding to the first bit and located immediately after the fifth bit plane; and the control method includes: when at least some of the plurality of mirrors are controlled according to the second or fifth bit plane, generating illumination light having the second power by the light source device; and when all of the plurality of mirrors are controlled according to bit planes different from the second and fifth bit planes, generating illumination light having the first power by the light source device.

[0078] A control device for a projection-type video display device according to one aspect of the present disclosure is applicable to a projection-type video display device that displays high-quality digital images or moving images.

[0079] REFERENCE SIGNS LIST 1 projection type image display device 11 control device 12 light source device 13 optical system 14 digital micromirror device (DMD) 14m mirror 15 optical system

Claims

1. A control device for a projection-type image display device equipped with a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control device controls the light source device to generate the illumination light at either a first power or a second power lower than the first power, the control device controls the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, each of the plurality of image frames including first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits, each of the first and second sub-frames including a plurality of bit planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order, the first subframe includes a first bit-plane corresponding to the first bit, a second bit-plane corresponding to the second bit and located immediately after the first bit-plane, and a third bit-plane corresponding to the third bit and located immediately after the second bit-plane; the second subframe includes a fourth bit-plane corresponding to the third bit, a fifth bit-plane corresponding to the second bit and located immediately after the fourth bit-plane, and a sixth bit-plane corresponding to the first bit and located immediately after the fifth bit-plane; and the control device controls the light source device to generate illumination light having the second power when at least some of the plurality of mirrors are controlled according to the second or fifth bit-plane, and controls the light source device to generate illumination light having the first power when all of the plurality of mirrors are controlled according to bit-planes different from the second and fifth bit-planes.

2. The control device according to claim 1, wherein the second and fifth bit planes have a first time length, the first and sixth bit planes have a second time length longer than the first time length, and the third and fourth bit planes have a third time length longer than the first time length.

3. The control device according to claim 2, wherein the plurality of mirrors are controlled to scan two-dimensionally in accordance with the video signal, and the second and third time lengths are set longer than the time lengths required to scan the plurality of mirrors in the sub-scanning direction of the digital micromirror device.

4. The control device of claim 1, wherein the second and fifth bit planes contain bit values ​​related to dithering of the image.

5. A control device for a projection-type image display device equipped with a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control device controls the light source device to generate the illumination light at either a first power or a second power lower than the first power, the control device controls the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, each of the plurality of image frames including first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to fourth bits, each of the first and second sub-frames including a plurality of bit planes respectively corresponding to the plurality of bits of each pixel and arranged in a predetermined temporal order, the plurality of bit planes being arranged in a predetermined temporal order, the first sub-frame including: a first bit plane corresponding to the first bit; the second subframe includes: a first bit-plane group including at least second and third bit-planes corresponding to the second and third bits and located immediately after the first bit-plane; and a fourth bit-plane corresponding to the fourth bit and located immediately after the first bit-plane group; the second subframe includes: a fifth bit-plane corresponding to the fourth bit; a second bit-plane group including at least sixth and seventh bit-planes corresponding to the second and third bits and located immediately after the fourth bit-plane; and an eighth bit-plane corresponding to the first bit and located immediately after the second bit-plane group; and the control device controls the light source device to generate illumination light having the second power when at least some of the plurality of mirrors are controlled in accordance with the first or second bit-plane group;a control device that controls the light source device to generate illumination light having the first power when all of the plurality of mirrors are controlled according to a bit plane different from the bit planes included in the first and second bit plane groups.

6. A projection-type image display device comprising: a light source device; a digital micromirror device; and the control device according to any one of claims 1 to 5.

7. A control method for a projection-type image display device equipped with a light source device and a digital micromirror device, wherein the digital micromirror device includes a plurality of mirrors arranged in a two-dimensional array and modulates illumination light generated by the light source device and incident on the digital micromirror device, the control method comprising: generating the illumination light with the light source device at either a first power or a second power lower than the first power; and controlling the plurality of mirrors by supplying a video signal including a plurality of image frames to the digital micromirror device, wherein each of the plurality of image frames includes first and second sub-frames representing the same image, the image including a plurality of pixels each having a pixel value represented by a plurality of bits including at least first to third bits; and each of the first and second sub-frames includes a plurality of bit planes respectively corresponding to the plurality of bits of each pixel, the plurality of bit planes being arranged in a predetermined temporal order; the first subframe includes a first bit-plane corresponding to the first bit, a second bit-plane corresponding to the second bit and located immediately after the first bit-plane, and a third bit-plane corresponding to the third bit and located immediately after the second bit-plane; the second subframe includes a fourth bit-plane corresponding to the third bit, a fifth bit-plane corresponding to the second bit and located immediately after the fourth bit-plane, and a sixth bit-plane corresponding to the first bit and located immediately after the fifth bit-plane; and the control method includes: when at least some of the plurality of mirrors are controlled according to the second or fifth bit-plane, generating illumination light having the second power by the light source device; and when all of the plurality of mirrors are controlled according to bit-planes different from the second and fifth bit-planes, generating illumination light having the first power by the light source device.

Images