Indication device

Abstract

To miniaturize an optical system of a display device.SOLUTION: A display device 10 includes: an indicator 20 for outputting linearly polarized display light; a first wavelength plate 22 for transmitting display light outputted from the indicator 20 and converting linearly polarized light to circularly polarized light; a partial reflection mirror 24 that has a first concave surface 24a for transmitting one portion of display light emitted from the first wavelength plate 22 and reflecting one portion while the first concave surface 24a has curvature in a first direction; a second wavelength plate 26 for transmitting display light emitted from the partial reflection mirror 24 and converting circularly polarized light to linearly polarized light; and a reflection type polarizer 28 that has a second concave surface 28a for reflecting a first linearly polarized light component of display light emitted from the second wavelength plate 26 and transmitting a second linearly polarized light component orthogonal to the first linearly polarized light component of display light, and is disposed such that the second concave surface 28a has curvature in a second direction orthogonal to the first direction and the second concave surface 28a faces the first concave surface 24a.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a display device.

Background Art

[0002] As a display device for a vehicle, an electronic mirror that displays an image of the rear of the vehicle on a display for the vehicle occupants to view is known (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, since the display light output from the display is folded back at a right angle by a half mirror, the optical system of the device is enlarged.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for miniaturizing the optical system of a display device.

Means for Solving the Problems

[0006] A display device according to one aspect of the present invention includes: a display unit that outputs linearly polarized display light; a first waveplate that transmits the display light output from the display unit and converts linearly polarized light into circularly polarized light; a partial reflection mirror having a first concave surface that transmits a portion of the display light emitted from the first waveplate and reflects a portion thereof, wherein the first concave surface has curvature in a first direction; a second waveplate that transmits the display light emitted from the partial reflection mirror and converts circularly polarized light into linearly polarized light; and a reflective polarizer having a second concave surface that reflects a first linearly polarized component of the display light emitted from the second waveplate and transmits a second linearly polarized component perpendicular to the first linearly polarized component of the display light, wherein the second concave surface has curvature in a second direction perpendicular to the first direction, and the second concave surface is arranged to face the first concave surface.

[0007] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0008] According to the present invention, the optical system of a display device can be miniaturized. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows a vehicle on which the display device according to the embodiment is installed. [Figure 2] This diagram schematically shows the configuration of a display device according to the embodiment. [Figure 3] This diagram schematically shows the configuration of a display device according to the embodiment. [Figure 4] This diagram schematically illustrates the effect of ambient light incident on a display device. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. The specific numerical values ​​and other details shown in the embodiments are merely examples to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. Furthermore, in this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0011] Figure 1 is a schematic diagram showing a vehicle 12 on which a display device 10 according to an embodiment is installed. The display device 10 displays images captured by a camera 14 mounted on the vehicle 12. The display device 10 is positioned, for example, in the position of the rearview mirror of the vehicle 12. The occupants 16 of the vehicle 12 can view images of the area behind the vehicle 12 by looking at the display device 10. The display device 10 functions as a so-called electronic rearview mirror.

[0012] The occupant 16 drives the vehicle 12 while switching between a first line of sight direction A for viewing the area in front of the vehicle 12 and a second line of sight direction B for viewing the display device 10 and checking the area behind the vehicle 12. In the first line of sight direction A, the occupant 16 usually focuses on objects at a distance of 2 meters or more. On the other hand, the distance from the occupant 16 to the display device 10 is relatively close, about 50 cm. Therefore, if the image is displayed directly at the position of the display device 10, the occupant 16 may have difficulty adjusting their focus when switching their gaze between the first line of sight direction A and the second line of sight direction B.

[0013] In this embodiment, the display device 10 displays the image of the area behind the vehicle 12 as a virtual image 18, and the virtual image display distance from the occupant 16 to the virtual image 18 is set to approximately 1m to 2m. This reduces the burden on the occupant 16 to adjust their focus when switching their gaze between the first line of sight direction A and the second line of sight direction B.

[0014] Figures 2 and 3 schematically show the configuration of the display device 10 according to the embodiment. In Figures 2 and 3, the optical axis from the display device 10 toward the occupant 16 is defined as the z direction, and the directions perpendicular to the optical axis are defined as the x and y directions. Figure 2 shows the display device 10 as viewed from the x direction, and Figure 3 shows the display device 10 as viewed from the y direction.

[0015] The display device 10 comprises a display unit 20, a first wave plate 22, a partial reflection mirror 24, a second wave plate 26, a reflective polarizer 28, a polarizing plate 30, a housing 32, and a display control device 34. The display unit 20, the first wave plate 22, the partial reflection mirror 24, the second wave plate 26, the reflective polarizer 28, and the polarizing plate 30 are arranged inside the housing 32 and are positioned in a line along the optical axis.

[0016] The display unit 20 displays an image for displaying the virtual image 18. The display unit 20 is an image display element such as a liquid crystal display (LCD) or an organic electroluminescent display (OELD). The display unit 20 is driven by the display control device 34.

[0017] The display unit 20 has a display surface 20a that outputs display light L1. The display unit 20 outputs linearly polarized display light L1. If the display unit 20 is a liquid crystal display, the display light L1 that is linearly polarized is output by the polarizing plates that make up the liquid crystal display. If the display unit 20 is an organic EL display, the display light L1 that is linearly polarized is output by a polarizing plate additionally provided on the display surface 20a. The direction of linear polarization of the display light L1 output from the display unit 20 is not particularly limited, but for example it is the x-direction.

[0018] The display 20 has a horizontally long shape, with the width Wx in the x - direction of the display 20 being relatively long and the width Wy in the y - direction of the display surface 20a being relatively short. The width Wx in the x - direction of the display 20 corresponds to the horizontal size of the image displayed on the display 20. The width Wy in the y - direction of the display 20 corresponds to the vertical size of the image displayed on the display 20. The width Wx in the x - direction of the display 20 is, for example, about 2 to 5 times the width Wy in the y - direction of the display 20.

[0019] The first wavelength plate 22 is arranged next to the display 20 on the optical axis extending in the z - direction. The first wavelength plate 22 is a quarter - wavelength plate and converts linearly polarized light into circularly polarized light. The linearly polarized display light L1 output from the display 20 becomes circularly polarized display light when passing through the first wavelength plate 22. The first wavelength plate 22 is arranged, for example, so as to convert linearly polarized light in the x - direction incident on the first wavelength plate 22 into right - hand circularly polarized light.

[0020] The partial reflection mirror 24 is arranged next to the first wavelength plate 22 on the optical axis extending in the z - direction. The partial reflection mirror 24 is configured to transmit a part of the display light and reflect a part of the display light. The partial reflection mirror 24 may be a so - called half - mirror, or may be configured such that the transmittance and reflectance of the display light are 50%. The partial reflection mirror 24 includes, for example, a base material made of a transparent material such as glass and a partial reflection film provided on the surface of the base material. The partial reflection film may be a metal film or a dielectric multilayer film.

[0021] The partial reflection mirror 24 has a first concave surface 24a. The first concave surface 24a is a curved surface directed in the +z direction and is a curved surface facing the reflective polarizer 28. The first concave surface 24a has a curvature in a first direction orthogonal to the optical axis (z - direction) and has a refractive power in the first direction. An example of the first direction is the y - direction, but it may also be the x - direction. The first concave surface 24a does not have a curvature in a second direction orthogonal to the first direction. An example of the second direction is the x - direction, but it may also be the y - direction. An example of the first concave surface 24a is a cylindrical surface.

[0022] The first concave surface 24a may have a slight curvature in the second direction (e.g., the x direction). In this case, the curvature of the first concave surface 24a in the second direction is smaller than the curvature of the first concave surface 24a in the first direction, for example, 20% or less, 10% or less, or 5% or less of the curvature in the first direction.

[0023] The second wavelength plate 26 is disposed next to the partial reflection mirror 24 on the optical axis extending in the z direction. The second wavelength plate 26 is a quarter-wave plate, which converts circularly polarized light into linearly polarized light and linearly polarized light into circularly polarized light. The circularly polarized display light transmitted through the partial reflection mirror 24 becomes linearly polarized display light when passing through the second wavelength plate 26. The second wavelength plate 26 is arranged, for example, to convert the right-handed circularly polarized light incident on the second wavelength plate 26 into linearly polarized light in the x direction.

[0024] The first wavelength plate 22 is disposed adjacent to the partial reflection mirror 24. The first wavelength plate 22, for example, contacts the convex surface 24b of the partial reflection mirror 24. Here, the convex surface 24b is a surface directed in the -z direction and is a surface facing the display 20. The first wavelength plate 22 may be a quarter-wave film covering the convex surface 24b or may have a surface shape corresponding to the convex surface 24b.

[0025] The second wavelength plate 26 is disposed adjacent to the partial reflection mirror 24. The second wavelength plate 26, for example, contacts the first concave surface 24a of the partial reflection mirror 24. The second wavelength plate 26 may be a quarter-wave film covering the first concave surface 24a or may have a surface shape corresponding to the first concave surface 24a.

[0026] The first wavelength plate 22, the partial reflection mirror 24, and the second wavelength plate 26 may be configured as an integrated optical element stacked in sequence.

[0027] Note that at least one of the first wavelength plate 22 and the second wavelength plate 26 may be disposed away from the partial reflection mirror 24. In this case, at least one of the first wavelength plate 22 and the second wavelength plate 26 may have a surface shape corresponding to the convex surface 24b or the first concave surface 24a of the partial reflection mirror 24, or may have a flat plate shape.

[0028] The reflective polarizer 28 is positioned after the second waveplate 26 on the optical axis extending in the z direction. The reflective polarizer 28 reflects the first linearly polarized light and transmits the second linearly polarized light that is orthogonal to the first linearly polarized light. The reflective polarizer 28 is, for example, a wire grid polarizer. The reflective polarizer 28 is configured to reflect linearly polarized light in the x direction and transmit linearly polarized light in the y direction.

[0029] The reflective polarizer 28 has a second concave surface 28a. The second concave surface 28a is a surface oriented in the -z direction and is the surface facing the partial reflection mirror 24. The second concave surface 28a has curvature in a second direction (e.g., the x direction) and refractive power in the second direction. The second concave surface 28a has no curvature in the first direction (e.g., the y direction). An example of the second concave surface 28a is a cylindrical surface.

[0030] The second concave surface 28a may have a slight curvature in the first direction (e.g., the y-direction). In this case, the curvature of the second concave surface 28a in the first direction is smaller than the curvature of the second concave surface 28a in the second direction, for example, 20% or less, 10% or less, or 5% or less of the curvature in the second direction.

[0031] The reflective polarizer 28 includes a substrate made of a transparent material such as glass, and a polarizing film provided on the surface of the substrate. The polarizing film covers the second concave surface 28a and has a curved shape corresponding to the second concave surface 28a. The second concave surface 28a reflects the first linearly polarized component of the display light and transmits the second linearly polarized component that is orthogonal to the first linearly polarized component. For example, the first linearly polarized component is linearly polarized in the x direction, and the second linearly polarized component is linearly polarized in the y direction.

[0032] The polarizing plate 30 is positioned after the reflective polarizer 28 on the optical axis extending in the z direction. The polarizing plate 30 has a flat plate shape. The polarizing plate 30 is a cover provided to close the opening 32a of the housing 32. The polarizing plate 30 is, for example, a reflective polarizer, configured to reflect first linearly polarized light and transmit second linearly polarized light. The polarizing plate 30 is, for example, configured to reflect linearly polarized light in the x direction and transmit linearly polarized light in the y direction. The polarizing plate 30 may also be an absorptive polarizer.

[0033] The display control device 34 controls the operation of the display unit 20. The display control device 34 acquires the video captured by the camera 14 and drives the display unit 20 so that the acquired video is displayed on the display unit 20. The various functions provided by the display control device 34 can be realized, for example, through the cooperation of hardware and software. The hardware of the display control device 34 is realized by components and mechanical devices such as the CPU and memory of a computer. The software of the display control device 34 is realized by a computer program or the like.

[0034] Next, the operation of the display device 10 will be described. The display light L1 output from the display unit 20 passes through the first wave plate 22, the partial reflection mirror 24, and the second wave plate 26. The display light L2 after passing through the first wave plate 22, the partial reflection mirror 24, and the second wave plate 26 is first linearly polarized light, for example, linearly polarized light in the x-direction.

[0035] The first linearly polarized display light L2 is reflected by the reflective polarizer 28. The display light L3 after being reflected by the reflective polarizer 28 is the first linearly polarized light. The display light L3 heading from the reflective polarizer 28 toward the second wave plate 26 passes through the second wave plate 26 and becomes circularly polarized light, and a portion of it is reflected by the first concave surface 24a of the partial reflection mirror 24. The display light reflected by the first concave surface 24a of the partial reflection mirror 24 passes through the second wave plate 26 and becomes second linearly polarized light that is perpendicular to the first linearly polarized light.

[0036] The second linearly polarized display light L4 emitted from the second wave plate 26 passes through the reflective polarizer 28 and then through the polarizer plate 30. The occupant 16 of the vehicle 12 sees the display light L5 emitted from the opening 32a of the housing 32. Therefore, the occupant 16 sees the display light L5 reflected by the first concave surface 24a of the partial reflective mirror 24 and the second concave surface 28a of the reflective polarizer 28.

[0037] The display unit 20 is positioned closer than the focal length of the first concave surface 24a. The first distance d1 (see Figure 2) over which the display light travels from the display unit 20 to the first concave surface 24a is smaller than the focal length of the first concave surface 24a. The first distance d1 is the sum of the second distance d2 from the display surface 20a of the display unit 20 to the second concave surface 28a and the third distance d3 from the first concave surface 24a to the second concave surface 28a (i.e., d1 = d2 + d3).

[0038] The display unit 20 is positioned closer than the focal length of the second concave surface 28a. The second distance d2 (see Figure 2) over which the display light travels from the display unit 20 until it is reflected by the second concave surface 28a is smaller than the focal length of the second concave surface 28a. The focal length of the second concave surface 28a in the second direction may be smaller than the focal length of the first concave surface 24a in the first direction. Since the curvature of a concave surface is inversely proportional to its focal length, the curvature of the first concave surface 24a in the first direction may be smaller than the curvature of the second concave surface 28a in the second direction.

[0039] By positioning the display unit 20 at a location closer than the focal length of the first concave surface 24a and closer than the focal length of the second concave surface 28a, the image displayed on the display unit 20 can be presented as a virtual image 18. For example, the curvature of the first concave surface 24a, the curvature of the second concave surface 28a, and the position of the display unit 20 can be determined so that the virtual image display distance from the crew member 16 to the virtual image 18 is approximately 1m to 2m.

[0040] According to this embodiment, the display unit 20, the partial reflection mirror 24, and the reflective polarizer 28 can be arranged in a line on the optical axis, thus allowing for a smaller optical system compared to a configuration where the optical axis is folded at a right angle. According to this embodiment, by combining the partial reflection mirror 24 having curvature in the first direction and the reflective polarizer 28 having curvature in the second direction, it is possible to prevent the concave mirror from strongly focusing the ambient light, such as sunlight, onto the display device 10.

[0041] Figure 4 schematically shows the effect of ambient light incident on the display device 10. Ambient light L10, such as sunlight, is incident on the polarizing plate 30. The polarizing plate 30 reflects the first linearly polarized light L11 and transmits the second linearly polarized light L12. The polarizing plate 30 functions as a mirror that reflects the first linearly polarized light L11, which is part of the ambient light L10. When the power to the display device 10 is off and no image is displayed on the display unit 20, the polarizing plate 30 can function as a general optical rearview mirror. Note that the polarizing plate 30 is not an essential component, and the display device 10 does not need to be equipped with a polarizing plate 30.

[0042] The second linearly polarized light L12, having passed through the polarizing plate 30, further passes through the reflective polarizer 28 and is incident on the second wave plate 26. The second linearly polarized light L12 passes through the second wave plate 26, is reflected by the first concave surface 24a of the partial reflection mirror 24, and passes through the second wave plate 26 again to become the first linearly polarized light L13. The first linearly polarized light L13 is incident on the second concave surface 28a of the reflective polarizer 28. Most of the first linearly polarized light L13 is reflected by the second concave surface 28a to become the first linearly polarized light L14, and a small portion of the remainder passes through the reflective polarizer 28 and the polarizing plate 30 and is emitted from the aperture 32a to the outside of the housing 32 to become the first linearly polarized light L15.

[0043] The first linearly polarized light L14 reflected by the second concave surface 28a passes through the second wave plate 26, is reflected by the first concave surface 24a of the partial reflection mirror 24, and passes through the second wave plate 26 again to become the second linearly polarized light L16. Most of the second linearly polarized light L16 passes through the reflective polarizer 28 and the polarizer 30 and exits the housing 32 through the aperture 32a to become the second linearly polarized light L17.

[0044] The first linearly polarized light L15 emitted to the outside of the housing 32 is reflected only by the first concave curved surface 24a, and is therefore focused in the first direction but not in the second direction. Accordingly, according to this embodiment, it is possible to suppress the temperature rise at the point of focus caused by the first linearly polarized light L15 being strongly focused to a single point outside the housing 32.

[0045] The second linearly polarized light L17 emitted to the outside of the housing 32 is reflected once by the second concave surface 28a and twice by the first concave surface 24a. Therefore, the position where the second linearly polarized light L17 is focused in the first direction is shifted from the position where the second linearly polarized light L17 is focused in the second direction. Accordingly, according to this embodiment, it is possible to suppress the temperature rise at the point of focus caused by the second linearly polarized light L17 being strongly focused to a single point outside the housing 32.

[0046] According to this embodiment, since the curvature in the first direction of the first concave surface 24a is relatively small, the degree to which the first linearly polarized light L15 and the second linearly polarized light L17 are focused in the first direction outside the housing 32 can be reduced. Therefore, according to this embodiment, the temperature rise at the point where the first linearly polarized light L15 and the second linearly polarized light L17 are focused outside the housing 32 can be suppressed.

[0047] Although the present invention has been described above with reference to the embodiments described above, the present invention is not limited to the embodiments described above, and the present invention is also included in combinations or substitutions of the configurations shown in each embodiment as appropriate. [Explanation of Symbols]

[0048] 10...Display device, 12...Vehicle, 20...Display unit, 22...First wave plate, 24...Partially reflective mirror, 24a...First concave surface, 26...Second wave plate, 28...Reflective polarizer, 28a...Second concave surface.

Claims

1. A display unit that outputs linearly polarized light, A first wave plate that transmits the display light output from the display and converts linearly polarized light into circularly polarized light, A partial reflection mirror having a first concave surface that transmits a portion of the display light emitted from the first wave plate and reflects a portion of it, wherein the first concave surface has curvature in a first direction perpendicular to the transmission direction of the display light, A second wave plate that transmits the display light emitted from the partial reflection mirror and converts circularly polarized light into linearly polarized light, A display device comprising: a reflective polarizer having a second concave surface that reflects a first linearly polarized component of the display light emitted from the second wave plate and transmits a second linearly polarized component perpendicular to the first linearly polarized component of the display light, wherein the second concave surface has curvature in a second direction perpendicular to both the transmission direction of the display light and the first direction, and the second concave surface is arranged to face the first concave surface in the transmission direction of the display light.

2. The display device according to claim 1, wherein the curvature of the first concave surface in the first direction is smaller than the curvature of the second concave surface in the second direction.

3. The display device according to claim 1 or 2, wherein the first concave surface has no curvature in the second direction, and the second concave surface has no curvature in the first direction.

4. The display device according to claim 1 or 2, wherein at least one of the first waveplate and the second waveplate is adjacent to the partial reflection mirror.

5. The aforementioned display unit shows video footage of the area behind the vehicle. The display device is the display device according to claim 1 or 2, which is mounted on the vehicle.

Images