projector

Abstract

To provide a projector capable of suppressing deviation of an image due to a difference in wavelength without changing resolution.SOLUTION: A projector 1 includes: a plurality of light sources 11R, 11G, and 11B that output light of a plurality of colors having different wavelengths; a spatial light phase modulator 13 that modulates the light of the plurality of colors and projects an image on a screen S; and a controller 14 that controls the spatial light phase modulator 13 using CGH patterns 21R, 21G, and 21B of a plurality of colors generated from original images 20R, 20G, 20B of a plurality of colors on the basis of a Fourier transform computer-generated hologram. The controller 14 superimposes projected images of respective colors on the screen S by displaying the CGH patterns 21R, 21G, and 21B of respective colors in different display regions of one spatial light phase modulator 13, and the CGH patterns 21R, 21G, and 21B of respective colors has different sizes according to the wavelengths.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a projector. [Background technology]

[0002] Projectors that use a spatial light modulator (SLM) to project an image based on a computer-generated hologram (CGH) are known, as disclosed in Patent Documents 1 and 2, for example.

[0003] The angle of view θ of a computer-generated hologram is determined by the following formula, and is a function of the wavelength λ of the light output from the light source and the pixel pitch p of the spatial light phase modulator. Therefore, when multiple colors of light with different wavelengths are diffracted using the same spatial light phase modulator, the angle of view θ changes depending on the wavelength, resulting in a phenomenon in which the images of each color are misaligned.

[0004]

number

[0005] [Patent Document 1] Patent No. 6483851 [Patent Document 2] Japanese Patent Application Publication No. 2019-204087 Summary of the Invention [Problem to be solved by the invention]

[0006] The simplest solution to this problem is to change the size of the original image for each color, but this solution has the problem of changing the resolution (number of pixels) depending on the color.

[0007] Therefore, an object of the present disclosure is to provide a projector that can suppress image misalignment due to differences in wavelength without changing the resolution. [Means for solving the problem]

[0008] In one aspect, the following solution is provided. A plurality of light sources outputting light of a plurality of colors with different wavelengths; a spatial light phase modulator that modulates the light of the plurality of colors and projects an image onto a screen; a control unit that controls the spatial light phase modulator using the multi-color CGH pattern generated based on a Fourier transform type computer generated hologram from a multi-color original image, the control unit displays the CGH patterns of each color in different display areas of one of the spatial light phase modulators, thereby superimposing the projected images of each color on the screen; A projector is provided in which the CGH patterns for each color vary in size depending on the wavelength. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a projector that can suppress image misalignment due to differences in wavelength without changing the resolution. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic side view of a vehicle equipped with a projector according to an embodiment of the present invention. [Figure 2] FIG. 1A is a diagram showing a schematic configuration of a projector according to this embodiment, and FIG. 1B is a diagram showing the arrangement of CGH patterns according to a conventional example. [Figure 3] FIG. 1A is a perspective view showing a schematic configuration of a projector according to this embodiment, and FIG. 1B is a diagram showing the arrangement of CGH patterns according to this embodiment. [Figure 4] FIG. 2 is a schematic diagram showing projected images of different colors superimposed on a screen. [Figure 5]FIG. 10 is a diagram showing an example of calculating the size (number of pixels) of a CGH pattern for each color. [Figure 6] 10A and 10B are diagrams illustrating examples of creating original images of each color. [Figure 7] 10A and 10B are diagrams illustrating an example of adjusting the projection position using an original image. [Figure 8] (a) is a diagram showing the grating pattern A used to deal with zero-order light, (b) is a diagram showing the CGH pattern arranged on the spatial light phase modulator, and (c) is a diagram comparing a projected image without the application of the grating pattern A and a projected image with the application of the grating pattern A. [Figure 9] (a) is a diagram showing the grating pattern B used to deal with zero-order light, (b) is a diagram showing the CGH pattern placed on the spatial light phase modulator, and (c) is a diagram comparing a projected image without the application of the grating pattern B with a projected image with the application of the grating pattern B. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that in the drawings, for ease of viewing, only some of the reference symbols may be used for multiple parts having the same attribute.

[0012] FIG. 1 is a schematic side view of a vehicle V equipped with a projector 1 according to this embodiment. As shown in Fig. 1, the projector 1 of this embodiment is mounted on the front end (bumper, etc.) of a vehicle V, which is a moving object. The projector 1 functions as a road projector that emits image light from the front end of the vehicle V to the road surface (screen S) ahead, and projects an image onto the road surface. The projected image may be a symbol such as an arrow, or may be a character (character string).

[0013] Fig. 2(a) is a diagram showing the schematic configuration of projector 1 according to this embodiment, and Fig. 2(b) is a diagram showing the arrangement of CGH patterns 21R, 21G, and 21B according to a conventional example. Fig. 3(a) is a perspective view showing the schematic configuration of projector 1 according to this embodiment, and Fig. 3(b) is a diagram showing the arrangement of CGH patterns 21R, 21G, and 21B according to this embodiment. Fig. 4 is a schematic diagram showing projected images of each color superimposed on screen S. As shown in FIGS. 2 and 3, the projector 1 includes a light source 11, a collimator unit 12, a spatial light phase modulator 13, and a control unit .

[0014] The light source 11 includes multiple light sources 11R, 11G, and 11B that output light of different wavelengths, and operates under the control of the above-mentioned control unit 14. The light source 11R includes, for example, a red LD that emits red laser light with a wavelength of 630 nm. The light source 11G includes, for example, a green LD that emits green laser light with a wavelength of 532 nm. The light source 11B includes, for example, a blue LD that emits blue laser light with a wavelength of 450 nm. Note that the light source 11 is not limited to an LD. For example, a combination of an LED, a wavelength filter, a polarizing filter, and a pinhole can be used to replace the LD.

[0015] The collimating section 12 converts the light from the light source 11 into parallel light and emits it toward the spatial light phase modulator 13. The collimating section 12 may cause the light from the light source 11 to be incident on the spatial light phase modulator 13 in the form of a substantially plane wave.

[0016] The spatial light phase modulator 13 modulates the incident light and projects an image onto the screen S. The spatial light phase modulator 13 operates under the control of the above-mentioned control unit 14. For example, an LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator) is used as the spatial light phase modulator 13.

[0017] The control unit 14 controls the spatial light phase modulator 13 using CGH patterns 21R, 21G, and 21B of each color, which are generated based on Fourier transform-type computer-generated holograms from original images 20R, 20G, and 20B of each color (see FIG. 6). The control unit 14 displays the CGH patterns 21R, 21G, and 21B of each color in different display areas of the single spatial light phase modulator 13, thereby superimposing the projected images of each color on the screen S. For example, as shown in FIG. 2(b), the CGH patterns 21R, 21G, and 21B of each color are displayed in the display area so as to be aligned in the long axis direction of the spatial light phase modulator 13.

[0018] The projector 1 configures an oblique incidence optical system in which light from the light source 11 is incident obliquely on the spatial light phase modulator 13. In this case, the spatial light phase modulator 13 may be tilted in the direction of the major axis of the spatial light phase modulator 13 with respect to the incident light, or in the direction of the minor axis of the spatial light phase modulator 13 with respect to the incident light, but in this embodiment, it is tilted in the direction of the minor axis, as shown in Figure 3(a). In this way, the incident angle of the light source 11 with respect to the spatial light phase modulator 13 can be reduced, and the projector 1 can be made smaller.

[0019] In such a projector 1, when the CGH patterns 21R, 21G, and 21B of each color as shown in FIG. 2(b) are displayed in the display area of ​​the spatial light phase modulator 13, the angle of view changes depending on the wavelength of each color, resulting in a phenomenon in which the projected images of each color are misaligned. In other words, even if the pixel sizes of the original images 20R, 20G, and 20B of each color are the same, the pixel sizes of each color in the projected image will differ depending on the wavelength. The present invention solves this problem by changing the size of the CGH patterns 21R, 21G, and 21B of each color depending on the wavelength of each color. The reason for this is as follows.

[0020] The minimum pixel size is the spot size when the CGH pattern is in phase across the entire surface. This corresponds to the point image size of a rectangular aperture. The point spread distribution I(x) of a rectangular aperture can be calculated using the following formula:

[0021]

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[0022] The equation for point spread I(x) is a function of wavelength λ and numerical aperture NA, and if the numerical aperture NA is changed in accordance with changes in wavelength λ, the spot size (= pixel size) will remain the same. The numerical aperture NA depends on the aperture size. In this embodiment, the aperture size = CGH pattern size (hereinafter referred to as CGH size as appropriate), so the CGH size can be changed for each wavelength λ.

[0023] FIG. 5 is a diagram showing an example of calculation of the size (number of pixels) of the CGH patterns 21R, 21G, and 21B of each color. As mentioned above, to make the pixel size of each color in the projected image the same, you can change the CGH size according to the wavelength. Specifically, the pixel size of each color will be equal when the following formula is satisfied:

[0024]

number

[0025] As in this embodiment, when CGH patterns 21R, 21G, and 21B of three colors of RGB are arranged on one spatial light phase modulator 13, the number of pixels N of the CGH patterns 21R, 21G, and 21B of each color is R , N G , N B can be calculated using FIG. 5 and the following formula, where N is the number of pixels of the spatial light phase modulator 13, λ R , λ G , λ B is the wavelength of each color.

[0026]

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[0027]

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[0028]

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[0029] According to the above calculations, the CGH size of each color is smallest for blue and largest for red. In this case, it is preferable to place the blue CGH pattern 21B, which has the smallest CGH size, in the center of the display area of ​​the spatial light phase modulator 13, and place the other CGH patterns 21R and 21G on either side of it, as shown in Figures 4 and 5. In this way, when projected images of each color are superimposed on the screen S, the amount of shift of the colors placed on both sides toward the center can be reduced.

[0030] FIG. 6 is a diagram showing an example of creating original images 20R, 20G, and 20B for each color. The original images 20R, 20G, and 20B for each color are based on the number of pixels of the original image 20B of the color that produces the smallest CGH size, and the original images 20R and 20G for the other colors are also drawn with the same number of pixels. Furthermore, black regions 20b are added to the outer edges of the drawing regions 20a of the original images 20R and 20G for the other colors to compensate for the difference in CGH size. This improves the computational efficiency when creating CGH patterns 21R, 21G, and 21B from the original images 20R, 20G, and 20B.

[0031] FIG. 7 is a diagram showing an example of adjusting the projection position using original images 20R, 20G, and 20B. As shown in Fig. 7, the spatial light phase modulator 13 displays CGH patterns 21R, 21G, and 21B of each color, thereby superimposing the projected images of each color on the screen S. At this time, misalignment of the CGH patterns 21R, 21G, and 21B may occur in the projected images of each color (see Fig. 7 before the countermeasure). In such a case, in this embodiment, the positions of the drawing areas 20a relative to the black areas 20b of the original images 20R and 20G are shifted toward the center (CGH pattern 21B) (see Fig. 7 after the countermeasure), thereby adjusting the projection positions on the screen S and suppressing the misalignment of the projected images of each color.

[0032] Figure 8(a) shows a grating pattern A for dealing with zero-order light, (b) shows CGH patterns 21R, 21G, and 21B arranged on the spatial light phase modulator 13, and (c) compares a projected image to which the grating pattern A is not applied with a projected image to which the grating pattern A is applied. 8(b), according to the CGH patterns 21R, 21G, and 21B of this embodiment, an area 13a to which the CGH patterns 21R, 21G, and 21B are not applied is generated on the spatial light phase modulator 13. This area 13a requires some measures to project the zero-order optical image Z onto the screen S (projected image).

[0033] In this embodiment, a grating pattern for dealing with zero-order light is applied to the region 13a. The grating pattern A shown in Fig. 8(a) has a number of gratings corresponding to one pixel of the spatial light phase modulator 13, and is embedded with a pattern that disperses and scatters the zero-order light outside the image projection region.

[0034] Figure 9(a) shows the grid pattern B for dealing with zero-order light, (b) shows the CGH patterns 21R, 21G, and 21B arranged on the spatial light phase modulator 13, and (c) is a comparison between a projected image without grid pattern B and a projected image with grid pattern B applied. The grid pattern applied to the region 13a to deal with the zero-order light may be a random pattern, such as grid pattern B shown in (a) of Fig. 9. With such grid pattern B, the zero-order light is thinly spread within the image projection region, eliminating the need for a mask (opening) to block the scattered zero-order light.

[0035] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. Furthermore, it is also possible to combine all or a plurality of components of the above-described embodiments.

[0036] The present invention includes the following examples.

[0037] [1] A plurality of light sources outputting light of different wavelengths and different colors; a spatial light phase modulator that modulates the light of the plurality of colors and projects an image onto a screen; a control unit that controls the spatial light phase modulator using the CGH pattern of the plurality of colors generated from the original image of the plurality of colors based on a Fourier transform type computer generated hologram, the control unit displays the CGH patterns of each color in different display areas of one of the spatial light phase modulators, thereby superimposing the projected images of each color on the screen; The CGH pattern for each color varies in size depending on the wavelength.

[0038] [2] The original image of each color is drawn using the number of pixels of the color that results in the smallest size as a reference, and the original images of other colors are drawn with the same number of pixels; The projector according to [1], wherein the original image of another color has a black area added to the outer periphery of the drawing area to fill in the difference with the size.

[0039] [3] The projector according to [2], wherein the projection position of the original image of another color on the screen is adjusted by shifting the position of the drawing area relative to the black area.

[0040] [4] The multiple colors are three colors; The projector according to any one of [1] to [3], wherein the CGH pattern of the smallest color is arranged in the center of the display area.

[0041] [5] An oblique incidence optical system is configured to make the light from the light source obliquely incident on the spatial light phase modulator, the CGH patterns of each color are displayed in the display area so as to be aligned in the long axis direction of the spatial light phase modulator; The projector according to any one of [1] to [4], wherein the spatial light phase modulator is tilted in a minor axis direction of the spatial light phase modulator with respect to the incident light.

[0042] [6] The projector according to any one of [1] to [5], wherein a grid pattern for dealing with zero-order light is applied to an area of ​​the display area where the CGH pattern of each color is not displayed.

[0043] [7] The projector according to [6], wherein the grating pattern is a random pattern that disperses zero-order light.

[0044] [8] The projector according to any one of [1] to [7], which is mounted on a moving object.

[0045] [9] The projector according to [8], wherein the screen is a road surface. [Explanation of symbols]

[0046] 1 projector 11(11R, 11G, 11B) Light source 12 Collimation section 13 Spatial light phase modulator 13a area 20(20R, 20G, 20B) Original image 20a Drawing area 20b black area 21(21R, 21G, 21B) CGH pattern S Screen V vehicle Z 0th optical image

Claims

1. A plurality of light sources outputting light of a plurality of colors with different wavelengths; a spatial light phase modulator that modulates the light of the plurality of colors and projects an image onto a screen; a control unit that controls the spatial light phase modulator using the multi-color CGH pattern generated based on a Fourier transform type computer generated hologram from a multi-color original image, the control unit displays the CGH patterns of the respective colors in different display areas of one of the spatial light phase modulators, thereby superimposing the projected images of the respective colors on the screen; A projector in which the CGH patterns for each color are made to have different sizes depending on the wavelength.

2. The original image of each color is drawn using the number of pixels of the color that results in the smallest size as a reference, and the original images of other colors are drawn with the same number of pixels; The projector according to claim 1 , wherein a black area is added to the outer periphery of the drawing area of ​​the original image of another color to fill in the difference in size with respect to the drawing area.

3. The projector according to claim 2 , wherein the projection position of the original image of the other color on the screen is adjusted by shifting the position of the drawing area relative to the black area.

4. the plurality of colors is three colors, The projector according to claim 1 , wherein the CGH pattern of the smallest color is positioned in the center of the display area.

5. an oblique incidence optical system that causes light from the light source to be obliquely incident on the spatial light phase modulator; the CGH patterns of each color are displayed in the display area so as to be aligned in the long axis direction of the spatial light phase modulator; The projector according to claim 1 , wherein the spatial light phase modulator is tilted in a minor axis direction of the spatial light phase modulator with respect to incident light.

6. 2. The projector according to claim 1, wherein a grid pattern for dealing with zero-order light is applied to an area of ​​the display area where the CGH pattern of each color is not displayed.

7. The projector according to claim 6 , wherein the grating pattern is a random pattern that disperses zero-order light.

8. The projector according to claim 1 , which is mounted on a moving object.

9. The projector of claim 8 , wherein the screen is a road surface.

Images