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 includes: a plurality of light sources 11R, 11G, 11B for outputting light of different wavelengths; a spatial light phase modulator 13 that diffracts the light output from the plurality of light sources 11R, 11G, 11B and projects an object image including an interference fringe based on a computer-generated hologram onto a screen S; and a controller 3 that controls the plurality of light sources 11R, 11G, 11B and the spatial light phase modulator 13. The projector consists of an oblique-incidence optical system that causes the light output from the plurality of light sources 11R, 11G, 11B to be obliquely incident on the spatial light phase modulator 13. Incident angles θ of the light output from the plurality of light sources 11R, 11G, 11B to the spatial light phase modulator 13 are different from each other in a two-dimensional direction and are set on the basis of wavelengths of the output light.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A projector that uses a spatial light modulator (SLM) to project an image including interference fringes based on a computer-generated hologram (CGH) is known. For example, it is disclosed in Patent Document 1.

[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 difference in wavelength, resulting in a phenomenon in which the images θ of each color are shifted.

[0004]

number

[0005] [Patent Document 1] JP 2017-151444 A 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 that the resolution (number of pixels) changes depending on the color.

[0007] In view of the above, 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 different wavelengths; a spatial light phase modulator that diffracts light output from the plurality of light sources and projects an object image including an interference fringe based on a computer-generated hologram onto a screen; A control unit that controls a plurality of the light sources and the spatial light phase modulator, an oblique incidence optical system that causes light output from the plurality of light sources to be obliquely incident on the spatial light phase modulator; The projector is characterized in that the angles of incidence of light output from the multiple light sources with respect to the spatial light phase modulator are different from each other in two-dimensional directions and are set based on the wavelength of the output light. Effect 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 description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a side view of a vehicle equipped with a head-up display device according to an embodiment of the present invention. [Diagram 2] 1 is a schematic cross-sectional view of a head-up display device according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a configuration of a display device. [Figure 4] 1A and 1B are diagrams showing the apparent pixel pitch of a spatial light phase modulator, in which (a) shows the case where the incident angle θ is 0 deg, and (b) shows the case where the incident angle θ is 25 deg. [Diagram 5] FIG. 13 is a diagram showing the relationship between the target angle of view and the incident angle θ for each color. [Figure 6] FIG. 13 is a diagram showing the incident angle θ for each color when the target angle of view is 8 deg. [Figure 7] FIG. 1 is a diagram showing a basic method for creating a control CGH pattern. [Figure 8] 1A to 1C are diagrams illustrating a method for creating a control CGH pattern according to the present embodiment. [Figure 9] FIG. 13 is a diagram showing a process for correcting deviation of a central angle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 given to a plurality of parts having the same attribute.

[0012] [Configuration of head-up display device] Fig. 1 is a schematic diagram of a side view of a vehicle 10 equipped with a head-up display device H according to this embodiment. Fig. 2 is a schematic cross-sectional view of the head-up display device H according to this embodiment. In Fig. 1 and Fig. 2, three orthogonal axes (X-axis, Y-axis, and Z-axis) are defined in a right-handed coordinate system. Here, the X-axis corresponds to the left-right direction (width direction) of the vehicle 10, the Z-axis corresponds to the front-rear direction of the vehicle 10, and the Y-axis corresponds to the up-down direction of the vehicle 10.

[0013] 1, the head-up display device H is disposed inside an instrument panel 7 of a vehicle 10. The head-up display device H reflects projected display light PL toward a passenger P (e.g., a driver) of the vehicle 10 by a windshield WS of the vehicle 10, thereby displaying a virtual image V. That is, the head-up display device H is a projection-type display device (projector) that emits (projects) display light PL emitted from a display 1 (described later) onto the windshield WS (projection member) and allows the passenger P to view a display image (virtual image) V obtained by this emission. This allows the passenger P to view the virtual image V superimposed on the scenery.

[0014] The head-up display device H accommodates a display 1, a reflecting mirror 2, a control unit 3, etc. in a case 4. The case 4 has an emission port 41 on the upper surface side of the instrument panel 7, and the display light PL is emitted from inside the case 4 toward the windshield WS through the emission port 41. The emission port 41 may be covered with a transparent dust cover.

[0015] The display device 1 emits display light PL. In this embodiment, the display device 1 emits display light PL including interference fringes that constitute a computer-generated hologram, as described below. In this case, the display light PL forms an image on the retina (screen S: see FIG. 3) of the passenger P, and a virtual image V is seen in front of the windshield WS. Details of the display device 1 will be described later with reference to FIG. 3 and subsequent figures.

[0016] The reflecting mirror 2 is in the form of, for example, a concave mirror, and reflects the display light PL from the display 1 while magnifying the display light PL, and directs the display light PL toward the windshield WS. That is, the reflecting mirror 2 magnifies the display light PL while folding it back.

[0017] The control unit 3 is, for example, in the form of a control circuit board, and controls the display device 1. For example, the control unit 3 generates display light PL according to various vehicle information at appropriate timing so that the various vehicle information is transmitted to the passenger P via the virtual image V. The type of vehicle information transmitted via the virtual image V and the control method of the display device 1 may be arbitrary.

[0018] 1 and 2, the head-up display device H has a reflecting mirror 2, but the reflecting mirror 2 may be omitted. In addition, other optical systems may be additionally disposed in the case 4. For example, the display light PL may be projected onto the windshield WS via the screen S.

[0019] [Display configuration] FIG. 3 is a schematic diagram showing the configuration of the display device 1. As shown in FIG.

[0020] The display 1 includes a light source 11, a collimator unit 12, and a spatial light phase modulator 13.

[0021] The light source 11 includes a plurality of light sources 11R, 11G, and 11B (see FIG. 6) that output light of different wavelengths, and operates under the control of the above-mentioned control unit 3. 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 substituted for the LD.

[0022] The collimating section 12 collimates the light from the light source 11 and emits the parallel light toward the spatial light phase modulator 13. The collimating section 12 may cause the light from the light source 11 to enter the spatial light phase modulator 13 in the form of a substantially plane wave.

[0023] The spatial light phase modulator 13 is a reflective modulator (spatial light modulator) that diffracts incident light and projects an object image including interference fringes based on a computer-generated hologram onto the screen S. The spatial light phase modulator 13 operates under the control of the above-mentioned control unit 3. For example, an LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator) is used as the spatial light phase modulator 13. Note that the spatial light phase modulator 13 is not limited to an LCOS-SLM. For example, a MEMS mirror array may be used.

[0024] In the display 1, the light output from the light source 11 is obliquely incident on the spatial light phase modulator 13. In other words, instead of a coaxial optical system in which the light output from the light source 11 is incident on the spatial light phase modulator 13 from the same direction as the central axis CL, an oblique incidence optical system is used in which the light output from the light source 11 is obliquely incident on the central axis CL of the spatial light phase modulator 13 at a predetermined incidence angle θ (θ≠0).

[0025] The incidence angle θ of each color of light output from the multiple light sources 11R, 11G, and 11B is set based on the wavelength of the light of each color so that the field angle FOV of each color in the computer-generated hologram coincides. Hereinafter, the principle of field angle adjustment using the oblique incidence optical system will be described with reference to Figs. 4 to 6.

[0026] FIG. 4 is a diagram showing the apparent pixel pitch p' of the spatial light phase modulator 13, where (a) shows the case where the incident angle θ is 0 deg, and (b) shows the case where the incident angle θ is 25 deg.

[0027] As shown in Fig. 4, the apparent pixel pitch p' as seen from the image side (screen S side) onto which the spatial light phase modulator 13 is projected changes according to the incident angle θ. For example, if the actual pixel pitch p in the H direction (horizontal direction) of the spatial light phase modulator 13 is 6.4 μm, as shown in Fig. 4(a), the apparent pixel pitch p' in the H direction when the incident angle θ is 0 deg is 6.4 μm. On the other hand, as shown in Fig. 4(b), the apparent pixel pitch p' in the H direction when the incident angle θ is 25 deg is 5.8 μm according to the following formula. p′=6.4×cos(25deg)=5.8

[0028] The field angle FOV of the computer-generated hologram is expressed by the following formula: where λ is the wavelength of the light output from the light source 11, and p is the pixel pitch of the spatial light phase modulator 13 in the H direction.

[0029]

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[0030] Moreover, the apparent pixel pitch p′ in the H direction in the oblique incidence optical system is expressed by the following formula.

[0031]

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[0032] If the pixel pitch p in the derivation formula for the angle of view FOV shown in [Mathematical formula 2] is replaced with the apparent pixel pitch p', the following formula is obtained.

[0033]

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[0034] Therefore, by setting the incidence angle θ of each color of light output from the multiple light sources 11R, 11G, and 11B according to the wavelength, it is possible to match the field of view FOV of each color in the computer-generated hologram. Note that in the above explanation and drawings, the incidence angle θ in the H direction with respect to the spatial light phase modulator 13 is shown for the sake of simplicity of explanation and illustration, but since the deviation of the field of view FOV due to the wavelength occurs in two-dimensional directions, the incidence angle θ in the V direction (vertical direction) must also be set in the same way as in the H direction.

[0035] Fig. 5 is a diagram showing the relationship between the target angle of view and the incident angle θ for each color, Fig. 6 is a diagram showing the incident angle θ for each color when the target angle of view is 8 deg.

[0036] Fig. 5 shows the achievable incident angle θ for each color for each target angle of view (6 to 12 deg) when the pixel pitch p of the spatial light phase modulator 13 is 6.4 μm. For example, as shown in Fig. 6, when the target angle of view is 8 deg, the incident angle θ is 45 deg for red light, 53 deg for green light, and 60 deg for blue light.

[0037] As described above, the display 1 uses an oblique incidence optical system and sets the incidence angle θ of each color according to the wavelength, making it possible to suppress image shifts caused by differences in wavelength without changing the resolution. Furthermore, the oblique incidence optical system has the advantage of being able to simplify the optical system compared to a coaxial optical system, as well as reducing light loss.

[0038] Next, the display control of the computer-generated hologram by the control unit 3 will be described with reference to FIG.

[0039] Fig. 7 is a diagram showing a basic method for creating a control CGH pattern, and Fig. 8 is a diagram showing a method for creating a control CGH pattern according to this embodiment.

[0040] As shown in FIG. 7, the control unit 3 controls the spatial light phase modulator 13 based on a control CGH pattern obtained by synthesizing the CGH pattern of the object and the CGH pattern of the lens, and projects a computer-generated hologram on the screen S. When projecting a color computer-generated hologram on the screen S, the control unit 3 controls the spatial light phase modulator 13 in a time-division manner based on three-color control CGH patterns, as shown in FIG. 8. That is, in the red display period, the spatial light phase modulator 13 is controlled based on the red control CGH pattern while turning on the red light source 11R. In addition, in the green display period, the spatial light phase modulator 13 is controlled based on the green control CGH pattern while turning on the green light source 11G. In addition, in the blue display period, the spatial light phase modulator 13 is controlled based on the blue control CGH pattern while turning on the blue light source 11B.

[0041] The control unit 3 changes the CGH pattern of the lens for each color according to the incident angle θ described above. That is, the CGH pattern of the lens for each color is changed to optimize the control CGH pattern for each color according to the apparent pixel pitch p' that changes according to the incident angle θ. For example, the CGH pattern of the lens for each color is changed so that an image is projected on the screen S with the apparent pixel pitch p' derived by the following formula. However, the pixel pitch p of the spatial light phase modulator 13 is 6.4 μm, the incident angle θ of red light is 45 deg, the incident angle θ of green light is 53 deg, and the incident angle θ of blue light is 60 deg. Apparent pixel pitch of red light p′=6.4×cos(45deg)=4.52 Apparent pixel pitch of green light p′=6.4×cos(53deg)=3.81 Apparent pixel pitch for blue light p′=6.4×cos(60deg)=3.23

[0042] FIG. 9 is a diagram showing a process for correcting the deviation of the central angle.

[0043] As described above, when the oblique incidence optical system is used and the incidence angle θ of each color is changed according to the wavelength, it is possible to match the field of view FOV (image size) of each color, but a phenomenon occurs in which the drawing central angle (center position of the image) of each color is shifted. In order to correct such a shift in the drawing central angle of each color, the control unit 3 synthesizes a central angle correction CGH pattern with at least two color control CGH patterns. For example, in the example shown in FIG. 9, the drawing central angle of red light is used as a reference, and a central angle correction CGH pattern for matching the drawing central angle of green light to the drawing central angle of red light is synthesized with the control CGH pattern for green light. In addition, a central angle correction CGH pattern for matching the drawing central angle of blue light to the drawing central angle of red light is synthesized with the control CGH pattern for blue light. The central angle correction CGH pattern is a CGH pattern created to have the same function as an optical component called a wedge prism.

[0044] Although each embodiment has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. In addition, it is also possible to combine all or a plurality of the components of the above-described embodiments. [Explanation of symbols]

[0045] H Head-up display device (projector) 1 Display 2 reflector 3. Control Unit 4 Cases 41 Exit port 11(11R, 11G, 11B) Light source 12 Collimation section 13 Spatial light phase modulator S Screen

Claims

1. A plurality of light sources outputting light of different wavelengths; a spatial light phase modulator that diffracts light output from the plurality of light sources and projects an object image including an interference fringe based on a computer-generated hologram onto a screen; A control unit that controls a plurality of the light sources and the spatial light phase modulator, an oblique incidence optical system that causes light output from the plurality of light sources to be obliquely incident on the spatial light phase modulator; A projector, wherein angles of incidence of light output from the plurality of light sources with respect to the spatial light phase modulator are different from one another in two-dimensional directions and are set based on the wavelength of the output light.

2. the control unit controls the spatial light phase modulator based on a control CGH pattern obtained by combining a CGH pattern of an object and a CGH pattern of a lens; The projector of claim 1 , wherein the CGH pattern of the lens is changed according to the angle of incidence.

3. The plurality of light sources include three light sources outputting light of three colors having different wavelengths, the control unit controls the spatial light phase modulator in a time division manner based on the control CGH patterns for three colors; 3. The projector according to claim 2, wherein a central angle correcting CGH pattern for correcting deviation of a drawing central angle for each color is synthesized with at least two of the control CGH patterns for the three colors.

Images