JP2023173740A - display device - Google Patents

Abstract

To provide a display device which can suppress a deviation of images due to a difference in wavelengths without changing a resolution.SOLUTION: A display device comprises: a first light source (11R) which outputs light in a first wavelength; a first spatial phase modulator (13) which diffracts light in the first wavelength; a first telescopic optical system (15) which expands/contracts a first real image (IM_R) with diffracted light of the first spatial phase modulator (13); a second light source (11G) which outputs light in a second wavelength shorter than the first wavelength; a second spatial phase modulator (13) which diffracts the light in the second wavelength; a second telescopic optical system (15) which expands/contracts a second real image (IM_G) with diffracted light of the second spatial phase modulator (13); and a multiplexing unit (17) which multiplexes the light passing through the first telescopic optical system (15) and the second telescopic optical system (15). A magnification of the second real image (IM_G) of the second telescopic optical system (15) is smaller than a magnification of the first real image (IM_R) of the first telescopic optical system (15).SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a display device.

2. Description of the Related Art A display device that displays an image including interference fringes based on a computer-generated hologram (CGH) using a spatial light modulator (SLM) is known. For example, a projector disclosed in Patent Document 1 is known.

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

Japanese Patent Application Publication No. 2017-151444

The simplest solution to this phenomenon is to change the size of the original image for each color. However, when such a solution is implemented, there is a problem in that the resolution (number of pixels) changes depending on the color.

Therefore, an object of the present disclosure is to provide a display device that can suppress image shifts due to differences in wavelength without changing resolution.

In one aspect, the following solution is provided.

a first light source (11R) that outputs light of a first wavelength;
a first spatial phase modulator (13) that diffracts the light of the first wavelength and displays an image including interference fringes based on a computer-generated hologram;
a first telescope optical system (15) that expands and contracts a first real image (IM_R) formed by the diffracted light of the first spatial phase modulator (13);
a second light source (11G) that outputs light with a second wavelength shorter than the first wavelength;
a second spatial phase modulator (13) that diffracts the light of the second wavelength and displays an image including interference fringes based on a computer-generated hologram;
a second telescope optical system (15) that expands and contracts a second real image (IM_G) formed by the diffracted light of the second spatial phase modulator (13);
a combining unit (17) that combines the light that has passed through the first telescope optical system (15) and the second telescope optical system (15),
The magnification rate of the second real image (IM_G) of the second telescope optical system (15) is set to be smaller than the magnification rate of the first real image (IM_R) of the first telescope optical system (15). A display device with features is provided.

According to the present disclosure, it is possible to provide a display device that can suppress image shifts due to differences in wavelength without changing resolution.

FIG. 1 is a schematic side view of a vehicle equipped with a head-up display device according to an embodiment. 1 is a schematic cross-sectional view of a head-up display device according to an embodiment. FIG. 2 is a schematic diagram showing the configuration of a display device. It is a schematic diagram showing one monochromatic optical system among a plurality of monochromatic optical systems. FIG. 2 is an explanatory diagram of a telescope optical system. FIG. 2 is a schematic diagram showing the configuration of a display device according to a second embodiment.

Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. Note that in the drawings, for ease of viewing, only some of the parts having the same attribute may be labeled with reference numerals.

[Configuration of head-up display device]
FIG. 1 is a schematic side view of a vehicle 10 equipped with a head-up display device H according to this embodiment. FIG. 1A is a schematic cross-sectional view of a head-up display device H according to this embodiment. In FIGS. 1 and 1A, 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 longitudinal direction of the vehicle 10, and the Y-axis corresponds to the vertical direction of the vehicle 10.

The head-up display device H is arranged inside the instrument panel 7 of the vehicle 10, as shown in FIG. The head-up display device H displays a virtual image V by reflecting the projected display light PL on the windshield WS of the vehicle 10 in the direction of the passenger P (for example, the driver) of the vehicle 10. That is, the head-up display device H emits (projects) display light PL emitted from a display device 1, which will be described later, onto a windshield WS (projection member), and displays a display image (virtual image) V obtained by this emission to the passenger. This is a projection type display device that is visible to P. Thereby, the passenger P can visually recognize the virtual image V superimposed on the scenery.

In the head-up display device H, a display 1, a reflector 2, a control unit 3, and the like are housed in a case 4. The case 4 has an exit 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 via the exit port 41. Note that the emission port 41 may be covered with a transparent dustproof cover.

The display device 1 emits display light PL. In this embodiment, the display device 1 emits display light PL including interference fringes forming a computer-generated hologram, as described later. In this case, the display light PL forms an image on the retina (screen) of the passenger P, and a virtual image V appears in front of the windshield WS. Details of the display device 1 will be described later with reference to FIG. 2 and subsequent figures.

The reflecting mirror 2 is, for example, in the form of a concave mirror, and magnifies the display light PL from the display device 1 while reflecting the display light PL to direct the display light PL toward the windshield WS. That is, the reflecting mirror 2 magnifies the display light PL while returning it.

The control unit 3 is, for example, in the form of a control circuit board, and controls the display 1. For example, the control unit 3 generates display light PL according to various vehicle information at appropriate timing so that 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 method of controlling the display 1 may be arbitrary.

In addition, in the example shown in FIG. 1 and FIG. 1A, the head-up display device H has the reflecting mirror 2, but the reflecting mirror 2 may be omitted. Further, other optical systems may be additionally arranged within the case 4. For example, the display light PL may be projected onto the windshield WS via a screen.

[Display configuration]
FIG. 2 is a schematic diagram showing the configuration of the display device 1. As shown in FIG.

The display 1 includes a light source 11, a collimator 12, a spatial phase modulator 13, a half mirror 14, a telescope optical system 15, a zero-order light cut mask 16, a dichroic mirror 17, and an aperture 18. .

In this embodiment, an optical system composed of the light source 11, the collimator 12, the spatial phase modulator 13, the half mirror 14, the telescope optical system 15, and the zero-order light cut mask 16 is referred to as a monochromatic optical system 19. Furthermore, the display device 1 of this embodiment includes a plurality of light sources 11R, 11G, and 11B that emit light of different wavelengths, and monochromatic optical systems 19R, 19G, and 19B are configured for each of the light sources 11R, 11G, and 11B. . However, since the configurations of each of the monochromatic optical systems 19R, 19G, and 19B are substantially the same, only one of the monochromatic optical systems 19 may be described below.

FIG. 3 is a schematic diagram showing one monochromatic optical system 19 among the plural monochromatic optical systems 19 (19R, 19G, 19B). FIG. 4 is an explanatory diagram of the telescope optical system 15.

The light source 11 outputs light of a predetermined wavelength. For example, the light source 11 includes an LD (laser diode) that emits laser light. As described above, the display device 1 of this embodiment includes a plurality of light sources 11R, 11G, and 11B that emit light of different wavelengths. The light source 11R includes, for example, a red LD that emits a red laser beam with a wavelength of 630 nm. Further, the light source 11G includes, for example, a green LD that emits green laser light with a wavelength of 532 nm. Further, the light source 11B includes, for example, a blue LD that emits blue laser light with a wavelength of 450 nm. Note that although the display device 1 of this embodiment includes three light sources 11R, 11G, and 11B that emit light with different wavelengths, the number of light sources 11 that emit light with different wavelengths may be two or four. There may be more than one. Furthermore, the light source 11 is not limited to an LD. For example, an LD can be replaced by combining an LED, a wavelength filter, a polarizing filter, and a pinhole.

The collimating unit 12 converts the light from the light source 11 into parallel light and emits the parallel light toward the spatial phase modulator 13 . The collimator 12 may cause the light from the light source 11 to enter the spatial phase modulator 13 in substantially the form of a plane wave.

The spatial phase modulator 13 is a reflective modulator (spatial light modulator) that diffracts incident light and displays interference fringes based on a computer-generated hologram. The spatial phase modulator 13 operates under the control of the control section 3 described above. As the spatial phase modulator 13, for example, a LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator) is used. Note that the light reflected by the spatial phase modulator 13 may include not only light for transmitting vehicle information toward the passenger P but also zero-order light that is not used for transmitting vehicle information.

The half mirror 14 is arranged between the collimating section 12 and the spatial phase modulator 13 with an inclination of a predetermined angle with respect to the optical axis. In other words, the half mirror 14 transmits the light emitted by the collimating section 12 and reflects the light diffracted by the spatial phase modulator 13 to enter the telescope optical system 15 .

The telescope optical system 15 enlarges or contracts the real image IM formed by the diffracted light of the spatial phase modulator 13. As the telescope optical system 15, a Keplerian telescope optical system or a Galilean telescope optical system can be used. As shown in FIG. 4, the telescope optical system 15 of this embodiment is a Keplerian telescope optical system, and is composed of two lenses 151 and 152 having positive focal lengths f1 and f2. The two lenses 151 and 152 are arranged with a distance corresponding to the sum of the focal lengths f1 and f2 of each lens 151 and 152. The magnification (magnification rate) of the telescope optical system 15 can be expressed by the following formula, where f1 is the focal length of the lens 151 on the spatial phase modulator 13 side, and f2 is the focal length of the lens 152 on the real image IM side. .

Magnification = f2/f1
In addition, in the Keplerian telescope optical system, once the distance a from the spatial phase modulator 13 to the lens 151 and the focal lengths f1 and f2 of each lens 151 and 152 are determined, the distance b from the lens 152 to the real image IM is unique. It is decided. When increasing the distance b, it is necessary to increase the focal lengths f1 and f2 and to decrease the distance a.

In the display device 1 of this embodiment, the size of the real image IM to be generated is adjusted for each wavelength using the telescope optical system 15, and the angle of view and pixel size are adjusted. This makes it possible to suppress image shifts due to differences in wavelength without changing resolution. A specific example is shown below.

Image generation in the real image IM is similar to that of the spatial phase modulator 13, and the angle of view is expressed by the same formula as in the spatial phase modulator 13 (see [Equation 1] in paragraph [0004]). Furthermore, the magnification of the size of the real image IM with respect to the size of the spatial phase modulator 13 is determined by the ratio of the focal lengths f1 and f2 of the lenses 151 and 152, as described above. The required real image pixel pitch for each wavelength is calculated as follows according to the desired angle of view (FOV 12 degrees, for example).

To obtain an FOV of 12 degrees at a wavelength of 450 nm (blue), a real image pixel pitch of approximately 2.1 um (μm) is required. Furthermore, in order to obtain an FOV of 12 degrees at a wavelength of 532 nm (green), a real image pixel pitch of approximately 2.5 um is required. Furthermore, in order to obtain an FOV of 12 degrees at a wavelength of 630 nm (red), a real image pixel pitch of approximately 3.0 um is required. Here, by setting the magnification of each telescope optical system 15 as described below, the angle of view of each wavelength can be matched even when spatial phase modulators 13 having the same pixel pitch are used.

For example, by setting the magnification of the telescope optical system 15 on which light of other wavelengths enters, based on a certain wavelength, the angle of view of all wavelengths is matched. The mode that can contribute to increasing the resolution the most is to set the magnification of the telescope optical system 15 to which light of other wavelengths enters to be small, based on the longest wavelength. As a specific example, when the pixel pitch of the spatial phase modulator 13 used is 3.0 um, each telescope optical system where light of each wavelength enters is set as follows, with the longest wavelength of 630 nm (red) as a reference. By determining the system 15, the same FOV of 12 degrees can be obtained at any of the wavelengths of 450 nm (blue), 532 nm (green), and 630 nm (red).

Magnification of wavelength 630 nm (reference wavelength: red) = 1.0 times Magnification of wavelength 532 nm (green) = wavelength 532 nm/reference wavelength 630 nm ≒ 0.84 times Magnification of wavelength 450 nm (blue) = wavelength 450 nm/reference Wavelength: 630 nm ≈ 0.71 times The zero-order light cut mask 16 blocks the zero-order light included in the light emitted from the spatial phase modulator 13 and prevents the zero-order light from reaching the real image IM. In the display device 1 of this embodiment, the telescope optical system 15 is a Keplerian telescope optical system, and a zero-order light cutting mask 16 is arranged at or near the focal position of the Keplerian telescope optical system. That is, in the Keplerian telescope optical system, since an intermediate image is generated at the focal position, it is easy to deal with zero-order light, and the zero-order light can be efficiently removed. A specific example of the zero-order light cut mask 16 is, for example, a transparent slide having a light-shielding (or light-absorbing) black dot that can block zero-order light. The positions and sizes of the zero-order light cut mask 16 and the sunspots can be adjusted empirically so that the zero-order light is effectively blocked.

As shown in FIG. 2, the dichroic mirror 17 is configured by combining a plurality of mirrors with different wavelengths of transmitted light and reflected light, and the dichroic mirror 17 is configured by combining a plurality of mirrors with different wavelengths of transmitted light and reflected light. (Real images IM_R, IM_G, IM_B) are multiplexed. In other words, the dichroic mirror 17 synthesizes the real images IM_R, IM_G, and IM_B of each color formed before the dichroic mirror 17, and displays the synthesized image as a reconstructed image G through the aperture 18 arranged after the dichroic mirror 17. let

The aperture 18 is a mask that blocks stray light (light unnecessary for image display), and has an opening 181 that allows only the light necessary for image display to pass through. The aperture 18 in this embodiment is arranged after the dichroic mirror 17. In other words, when placing the aperture 18 after the dichroic mirror 17, a plurality of apertures 18 are required depending on the number of monochromatic optical systems 19, but when placing the aperture 18 after the dichroic mirror 17, only one aperture 18 is required. Can be done. Further, a distance greater than a predetermined distance is required between the real image IM and the aperture 18, but by interposing the dichroic mirror 17 between the real image IM and the aperture 18, it becomes easier to secure the required distance. .

[Second example]
Next, a second embodiment of the present invention will be described with reference to FIG. However, for configurations common to the first embodiment, the same reference numerals as in the first embodiment are used, and the explanation of the first embodiment is used.

FIG. 5 is a schematic diagram showing the configuration of the display device 1B of the second embodiment.

The display device 1 of the first embodiment has a configuration suitable for a projection type display device, whereas the display device 1B of the second example has a configuration suitable for a direct view type display device. For example, the display device 1B of the second embodiment can be suitably used in a direct-view type head-up display device.

In the direct viewing method, the closer the distance between the eyes of the passenger P and the real image IM (IM_R+IM_G+IM_B), the wider the eye box becomes, which is advantageous in terms of visibility. In the display device 1B of the second embodiment, as shown in FIG. 5, real images IM_R, IM_G, and IM_B of each color are formed on the same surface after the dichroic mirror 17. This imaging position is near the eyes of the passenger P, and the passenger P can clearly see the reconstructed image G through the half mirror HM over the real image IM.

Furthermore, the display device 1B of the second embodiment is also provided with an aperture 18B that blocks stray light. The aperture 18B of the second embodiment is provided between the telescope optical system 15 and the dichroic mirror 17 of the three monochromatic optical systems 19R, 19G, and 19B. The number of apertures 18B required in the second embodiment is three, but by interposing the dichroic mirror 17 between the real image IM and the aperture 18B, a distance greater than a predetermined distance can be maintained between the real image IM and the aperture 18B. Can be secured.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes can be made within the scope of the claims. It is also possible to combine all or a plurality of the components of the embodiments described above.

For example, in the first embodiment and the second embodiment, the display device of the present invention was described as a head-up display. However, the projection-type display device shown in the first embodiment may be applied to a head-mounted display worn on the head of a viewer or a road projector that projects an image onto a road surface. Further, the direct-view type display device shown in the second embodiment may be applied to a head-mounted display.

H Head-up display device 1, 1B Display unit 2 Reflector 3 Control unit 4 Case 41 Output port 11 (11R, 11G, 11B) Light source 12 Collimator unit 13 Spatial phase modulator 14 Half mirror 15 Telescope optical system 151, 152 Lens 16 0th order light cut mask 17 Dichroic mirror 18, 18B Aperture 181 Opening 19 (19R, 19G, 19B) Monochromatic optical system IM (IM_R, IM_G, IM_B) Real image G Reconstructed image

Claims (5)

a first light source (11R) that outputs light of a first wavelength;
a first spatial phase modulator (13) that diffracts the light of the first wavelength and displays an image including interference fringes based on a computer-generated hologram;
a first telescope optical system (15) that expands and contracts a first real image (IM_R) formed by the diffracted light of the first spatial phase modulator (13);
a second light source (11G) that outputs light with a second wavelength shorter than the first wavelength;
a second spatial phase modulator (13) that diffracts the light of the second wavelength and displays an image including interference fringes based on a computer-generated hologram;
a second telescope optical system (15) that expands and contracts a second real image (IM_G) formed by the diffracted light of the second spatial phase modulator (13);
a combining unit (17) that combines the light that has passed through the first telescope optical system (15) and the second telescope optical system (15),
A display device, wherein the magnification rate of the second real image (IM_G) of the second telescope optical system (15) is set smaller than the magnification rate of the first real image (IM_R) of the first telescope optical system (15). . The display device according to claim 1, wherein the magnification factor of the first real image (IM_R) of the first telescope optical system (15) is set to 1. The first telescope optical system (15) and the second telescope optical system (15) are Keplerian telescope optical systems,
The display device according to claim 1, further comprising a zero-order light cut mask (16) that blocks zero-order light at a focal position of the Keplerian telescope optical system. The first real image (IM_R) and the second real image (IM_G) are formed before the combining section (17),
The display device according to any one of claims 1 to 3, further comprising an aperture (18) for blocking stray light at a stage subsequent to the multiplexing section (17). The first real image (IM_R) and the second real image (IM_G) are imaged on the same plane at a stage subsequent to the combining section (17),
between the output surface of the first telescope optical system (15) and the multiplexing section (17), and between the output surface of the second telescope optical system (15) and the multiplexing section (17). A display device according to any one of claims 1 to 3, comprising an aperture (18) for blocking stray light.