Optical system and head-up display device

Abstract

The purpose of the present invention is to provide a compact head-up display device.　A head-up display device (30) according to the present invention comprises a display panel (2), a light source (1) that supplies light to the display panel (2), a relay optical system (3) that maps image light emitted from the display panel (2), and a diffusion element part (4) that diffuses the image light mapped by the relay optical system (3). The diffusion element part (4) has different optical actions in the horizontal direction and the vertical direction of the diffusion element part (4) that correspond to the horizontal direction and the vertical direction of a viewer.

Description

Optical system and head-up display device

[0001] The present invention relates to an optical system and a head-up display device.

[0002] 2. Description of the Related Art Head-up display devices are known that project an image onto a windshield of a moving object such as an automobile or an aircraft, allowing the projected image to be observed as a virtual image through the windshield.

[0003] For example, Patent Document 1 discloses a conventional head-up display device that "includes a projection optical system that irradiates light from behind a transmissive liquid crystal display panel and enlarges and projects an image displayed on the liquid crystal display panel."

[0004] Japanese Patent Application Laid-Open No. 2009-229552

[0005] In the example of a head-up display device disclosed in Patent Document 1, a "magnified real image of an image formed by a relay lens" is projected onto the windshield by a projection lens, allowing the driver to observe a virtual image. In other words, by obtaining a magnified real image of the liquid crystal display panel using the relay lens, a small liquid crystal display panel can be used.

[0006] However, miniaturizing the liquid crystal display panel in a head-up display device poses problems that are different from those encountered in miniaturizing a normal optical system, as will be explained with reference to Figures 7A, 7B, and 7C.

[0007] 7A, 7B, and 7C are explanatory diagrams showing the relationship between the miniaturization of the image display element 2 and the projection optical system 20b. In FIGS. 7A to 7C, the projection optical system 20b includes at least a mirror 5 and a windshield 6.

[0008] Fig. 7A is a diagram showing an image display element 2 of a reference size. In Fig. 7A, the size of the reference image display element 2 is designated as A. The brightness F-number of the projection optical system 20b is determined by F = (focal length) / (pupil diameter = size of the eyebox 8) = 1 / 2 / tan (θ / 2). Fig. 7B is a diagram showing an example of a small-sized image display element 2.

[0009] 7B is a diagram showing a miniaturized image display element 2 obtained by similarly deforming the image display element 2 of FIG. 7A by a factor of 1 / 3, with the size of the image display element 2 being A / 3. In the configuration of FIG. 7B, the size of the eye box 8 is also reduced, so that it is not possible to ensure the size of the eye box 8 required for the head-up display device 30. FIG. 7C is a diagram showing another example of a small image display element 2.

[0010] 7C is a diagram in which the size of the image display element 2 is set to A / 3, as in Fig. 7B, but the size of the eye box 8 is returned to the same size as in Fig. 7A. In the configuration in Fig. 7C, the size of the eye box 8 necessary for the head-up display device 30 is ensured, but the brightness F-number of the projection optical system 20b is F = 1 / 2 / tan(3θ / 2), so a significantly brighter projection optical system 20b is required.

[0011] That is, when the liquid crystal display panel is made smaller, the optical performance of the projection optical system is significantly degraded, or, to ensure the optical performance, a larger number of lenses is required, resulting in a larger size. Furthermore, when only the image display element 2 is made smaller, the virtual image also becomes smaller, resulting in a narrower viewing angle of the head-up display device.

[0012] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a small-sized head-up display device.

[0013] In order to solve the above problem, one representative head-up display device of the present invention comprises a display panel, a light source that supplies light to the display panel, a relay optical system that maps the image light emitted from the display panel, and a diffusion element unit that diffuses the image light mapped by the relay optical system, and the diffusion element unit has different optical effects in the horizontal and vertical directions of the diffusion element unit that correspond to the horizontal and vertical directions of the viewer.

[0014] According to the present invention, it is possible to provide a small-sized head-up display device. Note that problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0015] 1 is a schematic diagram of a head-up display device. FIG. 1 is a schematic diagram of the configuration and functional block diagram of the head-up display device. FIG. 1 is a schematic diagram of the configuration and functional block diagram of the head-up display device. FIG. 2 is a plan view of an automobile, which is a moving body equipped with a head-up display device, viewed from the front. FIG. 2 is a diagram of a configuration using a display panel of a standard size. FIG. 3 is a diagram of a configuration using a display panel, a relay optical system, and a screen plate. FIG. 4 is a diagram of a configuration using a display panel, a relay optical system, and a diffusion element unit. FIG. 4 is a diagram of an example of the configuration of the diffusion element unit. FIG. 5 is a diagram of another example of the configuration of the diffusion element unit. FIG. 6 is a diagram of another example of the configuration of the diffusion element unit. FIG. 7 is a diagram of diffusion of image light when no microlenses are used. FIG. 8 is a diagram of an example of diffusion of image light when microlenses are used. FIG. 9 is a diagram of another example of diffusion of image light when microlenses are used. FIG. 10 is a diagram of an example of a projection optical system depending on the size of the display panel. FIG. 11 is a diagram of an example of a projection optical system depending on the size of the display panel. FIG. 12 is a diagram of an example of a projection optical system depending on the size of the display panel. FIG. 13 is a schematic diagram of the head-up display device. FIG. 14 is a schematic diagram of the configuration and functional block diagram of the head-up display device. FIG. 15 is a diagram of the basic configuration and operation of the diffusion element unit. 1 is a diagram showing mapping of incident light rays of a diffusion element unit; FIG. 2 is a diagram showing mapping of exiting light rays of a diffusion element unit; FIG. 3 is a diagram showing an example of lens data of a diffusion element unit; FIG. 4 is a diagram showing an example of free-form surface coefficients of a diffusion element unit; FIG. 5 is a diagram showing an example of diffusion of image light when a microlens is used; FIG. 6 is a diagram showing image light when there is no microlens, but with the same incident light as the example of diffusion of image light; FIG. 7 is a diagram showing an example of ray diagrams in the YZ cross section and the XZ cross section of a free-form surface lens; FIG. 8 is a diagram showing another example of lens data of a diffusion element unit; FIG. 9 is a diagram showing another example of free-form surface coefficients of a diffusion element unit; FIG. 10 is a diagram showing another example of diffusion of image light when a microlens is used; FIG. 11 is a diagram showing image light when there is no microlens, but with the same incident light as the other example of diffusion of image light; FIG. 12 is a diagram showing another example of ray diagrams in the YZ cross section and the XZ cross section of a free-form surface lens.

[0016] Hereinafter, an embodiment of the present invention and various examples will be described with reference to the drawings, etc. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications are possible by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the examples, parts having the same function are designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0017] The basic configuration of a head-up display device 30 will be described with reference to Fig. 1. The head-up display device may also be called a display device, a virtual image display device, or the like.

[0018] FIG. 1 is a schematic diagram of a head-up display device 30. The head-up display device 30 shown in FIG. 1 includes an image forming unit and an image projection unit. In an embodiment of the present invention, the image forming unit includes a light source 1 and an image display element or display panel 2. The image projection unit may include a mirror 5. Light is emitted from the light source 1 to the image display element or display panel 2, and then the image light from the display panel 2 is incident on the mirror 5. The image light emitted from the mirror 5 is reflected by a windshield 6 of a vehicle (e.g., an automobile 500 in FIG. 3 ) and incident on an observer's eye 9. While the present invention will be described using a case in which the image light is projected onto the windshield 6 of the vehicle, the projection unit that projects the image light may be a projection member such as a combiner. With this configuration, when viewed from the observer's eye 9, it appears as if the observer is viewing image information on a virtual image plane 7.

[0019] In the present invention, the mirror 5 functions as an image projection unit that magnifies and reflects image light from the image display element or display panel 2 in a direction at a set angle or in a predetermined direction. The mirror 5 is, for example, a concave mirror (magnifying mirror) and is provided on the optical path between the image display element or display panel 2 and the windshield 6. The mirror 5 functions as an image light projection unit that projects the image light emitted from the display panel 2 onto the windshield 6, causing the projected image light to be viewed as a virtual image by the eye 9 of a user such as a driver. The mirror 5 in this embodiment is configured as a mirror having a concave reflective surface.

[0020] The configuration of the head-up display device of this embodiment will be described with reference to FIG.

[0021] 2A and 2B are configuration and functional block diagrams of a head-up display device of this embodiment. As shown in FIGS. 2A and 2B , the head-up display device includes a display panel 2, a light source 1, and a controller 200 that controls the operations of these components. The head-up display device further includes a relay optical system 3 and a diffusion element unit 4. Light is irradiated from the light source 1 to the display panel 2, and image information (video information) displayed on the display panel 2 is emitted toward a mirror 5 via the relay optical system 3 and the diffusion element unit 4. The combination of the light source 1, the display panel 2, the relay optical system 3, and the diffusion element unit 4 may also be referred to as an optical system.

[0022] The light source 1 is typically configured to include an LED (Light Emitting Diode) light source, and multiple light sources may be arranged for use. The image display element or display panel 2 is typically a liquid crystal display (LCD) panel. The display panel 2 creates an image based on image data input in response to instructions from the controller 200, and displays the image on the display surface of the display element of the display panel 2. The image display element 2 may also be referred to as a liquid crystal display panel, liquid crystal display element, display element, display panel, etc. The light source 1 may also be referred to as a backlight.

[0023] As shown in Fig. 2A, in the embodiment of the present invention, the head-up display device 30 is a device including the controller 200. Also, as shown in Fig. 2B, if the controller 200 is not provided, the control unit of the automobile can function as the controller 200. When the control is performed by the automobile control unit, the control is almost the same as that of the controller 200 of the head-up display device 30, and the following embodiment will be described using the controller 200 of the head-up display device 30. In other words, the head-up display device 30 may include the controller 200, or an external control device such as that of the automobile may be used.

[0024] Various types of information are input to the controller 200 from external devices. For example, a navigation system 208, which is a navigation device that generates and outputs information related to the operation of a mobile object equipped with the head-up display device 30, and an ECU (Electronic Control Unit) 209 that controls the operation of the mobile object are connected to the controller 200. Various sensors 210 equipped in the mobile object are connected to the ECU 209, and are configured to notify the ECU 209 of detected information.

[0025] The controller 200 includes a microcomputer 202 that processes various data from the external devices described above, a memory device 206 connected to the microcomputer 202, and a backlight driving circuit 207 that drives the backlight 1.

[0026] The microcomputer 202 includes a RAM (Random Access Memory) 203 for storing various data from external devices, a CPU (Central Processing Unit) 205 for executing arithmetic processing to generate image data that is the basis of the virtual image viewed by the observer, and a ROM (Read Only Memory) 204 for storing programs and parameters that can execute the arithmetic processing in the CPU 205.

[0027] The controller 200 having the above configuration displays image information on the image display element 2. The image information displayed on the image display element 2 is emitted as image light by the light emitted from the backlight 1 through the relay optical system 3 and the diffusion element section 4 toward the mirror 5.

[0028] Returning to FIG. 1 , the image light emitted from the display panel 2 is projected onto the windshield 6 by the mirror 5. The image light projected from the mirror 5 onto the windshield 6 is reflected by the windshield 6 and reaches the position of the viewer's eye 9. This creates a relationship that, when viewed from the viewer's eye 9, is as if the viewer is viewing image information on the virtual image plane 7. If the mirror 5 is not provided, the image light from the display panel 2 is emitted onto the windshield 6, and the image light emitted onto the windshield 6 is reflected by the windshield 6 and reaches the position of the viewer's eye 9.

[0029] 1, consider imaginary points P1, P2, and P3 on the emission surface of the image light from the image display element 2. The image light emitted from these imaginary points is mapped to points Q1, Q2, and Q3 on the diffusion element 4 by the relay optical system 3. Considering the imaginary points on the virtual image plane 7 corresponding to the image light emitted from points Q1, Q2, and Q3, these points are points V1, V2, and V3 as shown in FIG.

[0030] The range in which points V1, V2, and V3 on the virtual image plane 7 can be seen even when the observer moves the position of his or her eye 9 is the eyebox 8. In this way, the relay optical system 3, the diffusion element unit 4, and the mirror 5 may be referred to as a projection optical system that displays an image (virtual image) of an object (aerial image) in front of the observer's eye 9. Note that the projection optical system does not necessarily have to include the mirror 5.

[0031] Here, an example in which the head-up display device 30 according to this embodiment is mounted on a vehicle or a moving object will be described with reference to FIG.

[0032] 3 is a plan view seen from the front of an automobile 500, which is a moving body equipped with a head-up display device 30. In the automobile 500 shown in FIG. 3, a windshield 6, which is a front glass as a windshield, is disposed in front of the driver's seat.

[0033] The head-up display device 30 projects image light onto the windshield 6, allowing the driver and observers in the vehicle 500 to visually recognize various information related to the vehicle 500 as virtual images. The image light is projected onto a position in front of or around the driver's seat. For example, the image light is projected onto a position shown in a dashed rectangular area R1.

[0034] Next, the basic configuration for miniaturizing the image display element 2 in this embodiment will be described with reference to FIGS. 4A to 4C. In FIGS. 4A to 4C, the projection optical system 20b includes a mirror 5 (FIG. 2A). In this embodiment, the mirror 5 is a concave mirror that has a light-collecting effect, which corresponds to the same function as a convex lens. However, the projection optical system 20b may not be a convex lens, and may include a concave lens in addition to the mirror 5 as an optical component. Similarly, the relay optical system may be composed of multiple lenses including a field lens. Note that the F-number, which represents the brightness of the optical system, is determined by using θ, as F=1 / 2 / tan(θ / 2). The smaller the F-number, the brighter the image; in other words, the larger the θ, the brighter the image.

[0035] Fig. 4A is a diagram showing a configuration using an image display element 2 of a standard size. In Fig. 4A, the size of the standard image display element 2 is designated as A. Using θ, the F-number, which represents the brightness of the optical system, is determined by F = (focal length) / (pupil diameter = size of the eyebox 8) = 1 / 2 / tan(θ / 2). The smaller the F-number, the brighter the image, i.e., the larger θ, the brighter the image.

[0036] Figure 4B is a diagram showing a configuration using a small image display element 2, relay optical system 3, and screen plate 4b. In Figure 4B, the size of the image display element 2 is A / 3. In Figure 4B, a relay optical system 3 with a magnification of 3x is used to map an image onto the screen plate 4b, thereby ensuring the size of the eyebox 8. The angle of the relay optical system 3 on the screen plate 4b side is θ, the angle of the relay optical system 3 on the image display element 2 side is 3θ, and the F-number is F = 1 / 2 / tan (3θ / 2), so the relay optical system 3 has a very large aperture.

[0037] 4C is a diagram showing a configuration using a small image display element 2, a relay optical system 3, and a diffusion element unit 4. In Fig. 4C, the size of the image display element 2 is set to A / 3, but the angle of the relay optical system 3 on the image display element 2 side remains θ, and the angle of the relay optical system 3 on the diffusion element unit 4 side is set to θ / 3, and the diffusion element unit 4 diffuses the image light, thereby ensuring the size of the eyebox 8. The angle θ in Fig. 4C is made up of light incident from the image display element 2 on the upper part of the relay optical system 3 and light incident on the lower part of the relay optical system 3.

[0038] 4C, a small image display element 2 can be used without increasing the size of the relay optical system 3. Details of this diffusion element section 4 will be described using FIGS. 5A to 5C. Note that with respect to the vehicle, driver, or viewer, the X axis is the horizontal direction, left-right direction, lateral direction of the vehicle, or width direction of the vehicle, the Y axis is the up-down direction, vertical direction, or lengthwise direction of the vehicle, and the Z axis, which is perpendicular to the lateral direction of the vehicle, is the front-rear direction of the vehicle or the direction of travel of the vehicle.

[0039] 5A to 5C, the X-axis and Y-axis correspond to the horizontal and vertical directions of the viewer's field of view (eye box 8). The horizontal observation range increases by the distance between the left and right eyes. For example, the eye box 8 is 130 mm horizontally and 50 mm vertically. Therefore, a larger observation range is required on the side of the diffusion element 4 corresponding to the X-axis direction compared to the side corresponding to the Y-axis direction. Furthermore, if the microlenses are cylindrical lenses, the radius of curvature of the cylindrical lenses can only be seen from a specific direction, for example, when the light incident side of the microlens array 41 is viewed from the left or right, and when the light exit side of the microlens array 41 is viewed from above or below.

[0040] In Fig. 5A, the light incident side of the microlens array 41 is flat, and the light exit side of the microlens array 41 diffuses light in both the vertical and horizontal directions. In Fig. 5B, the light incident side of the microlens array 41 diffuses light in the Y-axis direction (vertical direction), and the light exit side of the microlens array 41 diffuses light in the X-axis direction (horizontal direction). In Fig. 5C, the light incident side of the microlens array 41 is flat, and the light exit side of the microlens array 41 diffuses light in the horizontal direction.

[0041] 5A(1) to 5A(3) are diagrams showing an example of the configuration of the diffusion element unit 4. In FIG. 5A, the diffusion element unit 4 includes a microlens array 41 and a light-shielding grating 42a. The light-shielding grating and the microlens array are arranged via adhesive or a holding portion. The microlens array 41 has one or more microlenses. The light-shielding grating 42a has one or more openings and is arranged on the light-emitting side of the microlens array 41. The microlens array 41 corresponds to the openings of the light-shielding grating 42a. One microlens may correspond to one opening, or one or more microlenses may correspond to one opening, and there is no particular limitation. In other words, the light-shielding grating has an opening, and the opening has one or more openings, and each opening corresponds to at least one microlens. In this embodiment, the openings of the light-shielding grating for shielding are arranged according to the microlens array. Each pixel of the image display element 2 corresponds to each cell of the microlens array 41 mapped by the relay optical system 3.

[0042] 5A, the light incident side of the microlens array 41 is flat, and the light exit side of the microlens array 41 diffuses light in both the vertical and horizontal directions. The microlens array 41 has different radii of curvature in the XZ cross section and the YZ cross section, and the diffusion angle in the X-axis direction is greater than the diffusion angle in the Y-axis direction. In other words, the divergence effect of each microlens in the microlens array 41 in the horizontal direction (X-axis direction) is greater than the divergence effect of each microlens in the vertical direction (Y-axis direction). Note that the "diffusion effect" in this invention may also be referred to as a "divergence effect."

[0043] The microlenses may be, for example, toroidal lenses or free-form lenses. Each aperture of the light-shielding grating 42a corresponds to each lens of the microlens array 41, and blocks light that spreads to the periphery of each cell from the focused image (spot) of light at each cell of the microlens array 41 mapped by the relay optical system 3. Although this differs depending on the panel size and resolution, the aperture ratio of each pixel of the image display element 2 is, for example, about 50%, so that degradation of resolution is prevented by blocking the light beam of the relay optical system 3 that spreads beyond the magnification.

[0044] 5B(1) to 5B(4) are diagrams showing other examples of the configuration of the diffusion element section 4. While the light-shielding grating 42a in Fig. 5A is arranged on the light-exiting side of the microlens array 41, in Fig. 5B, the light-shielding grating 42c is arranged on the light-incident side of the microlens array 41, and the light-shielding grating 42b is arranged on the light-exiting side of the microlens array 41. The light-shielding grating and the microlens array are arranged by bonding or via a structure or the like.

[0045] In the microlens array 41 of Fig. 5B, the microlenses on the light incident side diffuse light in the Y-axis direction, and the microlenses on the light exit side diffuse light in the X-axis direction. A light-shielding grating 42b is arranged in the X-axis direction, and a light-shielding grating 42c is arranged in the Y-axis direction. Alternatively, in Fig. 5B, the light incident side of the microlens array 41 diffuses light in the vertical direction, and the light exit side of the microlens array 41 diffuses light in the horizontal direction. Also, although Fig. 5B shows a light-shielding grating arranged in the direction of diffusion, the light-shielding grating 42a of Fig. 5A may also be used.

[0046] 5C(1) to 5C(3) are diagrams showing another example of the configuration of the diffusion element unit 4. The microlens array 41 in FIG. 5C has a shape with a radius of curvature only in the X-axis direction, and for example, a cylindrical lens array or a free-form lens array can be used. In FIG. 5C, the incident side of the microlens array 41 is flat, and the exit side of the microlens array 41 diffuses light in the horizontal direction. The microlens array 41 in FIG. 5C has a diffusion effect only in the X-axis direction. In other words, each microlens in the microlens array 41 has a diverging effect only in the horizontal direction (X-axis). Therefore, in FIG. 5C, a light-shielding grating 42b with a shading effect only in the Y-axis direction is arranged on the light exit side.

[0047] The light-shielding grating 42b in FIG. 5C may have a shape that has a shielding effect only in the Y-axis direction, or the light-shielding grating 42a in FIG. 5A may be used. Furthermore, the microlens array 41 shown in FIGS. 5A to 5C may be configured to have different divergence effects on the light incident side and the light exit side. Note that in FIGS. 5A to 5C, the diffusion element 4 may have an integrated structure (holding) the microlens array 41 and the light-shielding gratings 42a, 42b, and 42c. Each microlens of the microlens array 41 may have a diffusing effect on at least one of the light incident surface side and the light exit surface side of the diffusion element. Furthermore, a telecentric optical design may be used between the relay optical system 3 and the diffusion element 4, or a lenticular lens may be placed immediately before the diffusion element 4.

[0048] 6A to 6D, the diffusion effect of the image light by the microlens array 41 of the diffusion element unit 4 will be described. 6A to 6D show the state in which the image light is incident on the microlens array 41 from the relay optical system 3 side.

[0049] Fig. 6A is a diagram showing the diffusion of image light when no microlenses are used. Fig. 6A shows the case where the microlens array 41 is not used as a reference, and the shape of the image light on the image display element side or relay optical system side is almost the same as that on the Eyebox side.

[0050] 6B is a diagram showing an example of diffusion of image light when a microlens is used. In Fig. 6B, a microlens array 41 having a positive refractive power is placed in front of the light-condensing position of the relay optical system 3, thereby increasing the angle at which the image light is diffused.

[0051] 6C is a diagram showing another example of diffusion of image light when a microlens is used. In this example, a microlens array 41 having a positive refractive power is disposed in front of the light-condensing position of the relay optical system 3 and a negative refractive power is disposed behind the light-condensing position, thereby further increasing the angle at which the image light is diffused.

[0052] Fig. 6D is a diagram showing another example of diffusion of image light when microlenses are used. In Fig. 6D, a microlens array 41 with a decentered negative refractive power is arranged after the light-condensing position of the relay optical system 3, thereby increasing the angle at which the image light is diffused and emitting the light at an angle. Note that in Fig. 6D, each microlens of the microlens array 41 may be a decentered lens.

[0053] The head-up display device of this embodiment includes a light source 1, a display panel 2, a relay optical system 3 that maps image light emitted from the display panel 2, and a diffusion element unit 4 that diffuses the image light mapped by the relay optical system 3. The device may further include a mirror 5 that reflects the image light diffused by the diffusion element unit 4. When the mirror 5 is included, the light reflected by the mirror 5 is projected onto a projection member such as a windshield 6 to display a virtual image. When the mirror 5 is not included, the image light diffused by the diffusion element unit 4 is emitted onto a projection member such as a windshield 6 to display a virtual image. The diffusion element unit 4 includes a microlens array 41 having a plurality of microlenses, and the microlens array 41 has different optical effects in the horizontal and vertical directions of the microlens array 41, which correspond to the horizontal and vertical directions of the field of view in which the virtual image can be observed.

[0054] As a result, according to this embodiment, even if the image display element 2 is made smaller, the optical performance of the projection optical system 20b can be ensured without increasing the number of lenses, and a small head-up display device can be provided.

[0055] The image display element 2 may be a reflective image display element in addition to a transmissive liquid crystal display panel.

[0056] Furthermore, between the relay optical system 3 and the diffusion element unit 4, a telecentric optical design may be performed, or a lenticular lens may be disposed immediately before the diffusion element unit 4.

[0057] <Other Embodiments> The basic configuration of a head-up display device 30 will be described with reference to Fig. 8. The head-up display device may also be called a display device, a virtual image display device, or the like.

[0058] FIG. 8 is a schematic diagram of a head-up display device 30. The head-up display device 30 shown in FIG. 8 includes an image forming unit and an image projection unit. In an embodiment of the present invention, the image forming unit includes a light source 1 and an image display element or display panel 2. The image projection unit may include a concave lens 10 and a mirror 5. Light is emitted from the light source 1 to the image display element or display panel 2, and then the image light from the display panel 2 is incident on the mirror 5. The image light emitted from the mirror 5 is reflected by the windshield 6 of a vehicle (e.g., the automobile 500 in FIG. 3 ) and incident on the observer's eye 9. While the present invention will be described using a case where the image light is projected onto the windshield 6 of the vehicle, the projection unit that projects the image light may be a projection member such as a combiner. With this configuration, when viewed from the observer's eye 9, it appears as if the observer is viewing image information on a virtual image plane 7.

[0059] In the present invention, the mirror 5 functions as an image projection unit that magnifies and reflects image light from the image display element or display panel 2 in a direction at a set angle or in a predetermined direction. The mirror 5 is, for example, a concave mirror (magnifying mirror) and is provided on the optical path between the image display element or display panel 2 and the windshield 6. The mirror 5 functions as an image light projection unit that projects the image light emitted from the display panel 2 onto the windshield 6, causing the projected image light to be viewed as a virtual image by the eye 9 of a user such as a driver. The mirror 5 in this embodiment is configured with a mirror having a concave reflective surface. The mirror 5 may also be called a reflective element, a reflective mirror, or the like.

[0060] The configuration of the head-up display device of this embodiment will be described with reference to FIGS. 9A and 9B.

[0061] 9A and 9B are configuration and functional block diagrams of a head-up display device of this embodiment. As shown in FIGS. 9A and 9B , the head-up display device includes a display panel 2, a light source 1, and a controller 200 that controls the operations of these components. The head-up display device further includes a relay optical system 3, a diffusion element unit 4, and a concave lens 10. Light is irradiated from the light source 1 to the display panel 2, and image information (video information) displayed on the display panel 2 is emitted toward a mirror 5 via the relay optical system 3, the diffusion element unit 4, and the concave lens 10. The combination of the light source 1, the display panel 2, the relay optical system 3, the diffusion element unit 4, and the concave lens 10 may also be referred to as an optical system.

[0062] The light source 1 is typically configured to include an LED (Light Emitting Diode) light source, and multiple light sources may be arranged for use. The image display element or display panel 2 is typically a liquid crystal display (LCD) panel. The display panel 2 creates an image based on image data input in response to instructions from the controller 200, and displays the image on the display surface of the display element of the display panel 2. The image display element 2 may also be referred to as a liquid crystal display panel, liquid crystal display element, display element, display panel, etc. The light source 1 may also be referred to as a backlight. The concave lens 10 may also be referred to as an optical element.

[0063] As shown in Fig. 9A , in the embodiment of the present invention, the head-up display device 30 is a device including the controller 200. Also, as shown in Fig. 9B , if the controller 200 is not provided, the control unit of the automobile can function as the controller 200. When controlled by the automobile control unit, the control is almost the same as that of the controller 200 of the head-up display device 30, and the following embodiment will be described using the controller 200 of the head-up display device 30. In other words, the head-up display device 30 may include the controller 200, or an external control device such as that of the automobile may be used.

[0064] Various types of information are input to the controller 200 from external devices. For example, a navigation system 208, which is a navigation device that generates and outputs information related to the operation of a mobile object equipped with the head-up display device 30, and an ECU (Electronic Control Unit) 209 that controls the operation of the mobile object are connected to the controller 200. Various sensors 210 equipped in the mobile object are connected to the ECU 209, and are configured to notify the ECU 209 of detected information.

[0065] The controller 200 includes a microcomputer 202 that processes various data from the external devices described above, a memory device 206 connected to the microcomputer 202, and a backlight driving circuit 207 that drives the backlight 1.

[0066] The microcomputer 202 includes a RAM (Random Access Memory) 203 for storing various data from external devices, a CPU (Central Processing Unit) 205 for executing arithmetic processing to generate image data that is the basis of the virtual image viewed by the observer, and a ROM (Read Only Memory) 204 for storing programs and parameters that can execute the arithmetic processing in the CPU 205.

[0067] The controller 200 having the above configuration displays image information on the image display element 2. The image information displayed on the image display element 2 is emitted as image light by the light emitted from the backlight 1 through the relay optical system 3, the diffusion element unit 4, and the concave lens 10 toward the mirror 5.

[0068] Returning to Fig. 8, the image light emitted from the display panel 2 is projected onto the windshield 6 by the mirror 5. The image light projected from the mirror 5 onto the windshield 6 is reflected by the windshield 6 and reaches the position of the viewer's eye 9. This creates a relationship that, when viewed from the viewer's eye 9, is as if the viewer is viewing image information on the virtual image plane 7. If the mirror 5 is not provided, the image light from the display panel 2 is emitted onto the windshield 6, and the image light emitted onto the windshield 6 is reflected by the windshield 6 and reaches the position of the viewer's eye 9.

[0069] As shown in Fig. 8, consider imaginary points P1, P2, and P3 on the emission surface of the image light from the image display element 2. The image light emitted from these imaginary points is mapped to points Q1, Q2, and Q3 on the diffusion element 4 by the relay optical system 3. Considering the imaginary points on the virtual image plane 7 corresponding to the image light emitted from points Q1, Q2, and Q3, these points are points V1, V2, and V3 as shown in Fig. 8.

[0070] The range in which points V1, V2, and V3 on the virtual image plane 7 can be seen even when the observer moves the position of his or her eye 9 is the eyebox 8. In this way, the relay optical system 3, the diffusion element 4, the concave lens 10, and the mirror 5 may be referred to as a projection optical system that displays an image (virtual image) of an object (aerial image) in front of the observer's eye 9. Note that the projection optical system does not have to include the mirror 5.

[0071] Here, an example in which the head-up display device 30 according to this embodiment is mounted on a vehicle or a moving object will be described with reference to FIG.

[0072] 3 is a plan view seen from the front of an automobile 500, which is a moving body equipped with a head-up display device 30. In the automobile 500 shown in FIG. 3, a windshield 6, which is a front glass as a windshield, is disposed in front of the driver's seat.

[0073] The head-up display device 30 projects image light onto the windshield 6, allowing the driver and observers in the vehicle 500 to visually recognize various information related to the vehicle 500 as virtual images. The image light is projected onto a position in front of or around the driver's seat. For example, the image light is projected onto a position shown in a dashed rectangular area R1.

[0074] Next, the basic configuration for miniaturizing the image display element 2 in this embodiment will be described with reference to FIGS. 4A to 4C. In FIGS. 4A to 4C, the projection optical system 20b includes a mirror 5 (FIG. 9A). In this embodiment, the mirror 5 is a concave mirror that has a light-collecting effect, which corresponds to the same function as a convex lens. However, the projection optical system 20b may not be a convex lens, and may include a concave lens in addition to the mirror 5 as an optical component. Similarly, the relay optical system 3 may be composed of multiple lenses including a field lens. Note that the F-number, which represents the brightness of the optical system, is determined by using θ, as F=1 / 2 / tan(θ / 2). The smaller the F-number, the brighter the image; in other words, the larger the θ, the brighter the image.

[0075] Fig. 4A is a diagram showing a configuration using an image display element 2 of a standard size. In Fig. 4A, the size of the standard image display element 2 is designated as A. Using θ, the F-number, which represents the brightness of the optical system, is determined by F = (focal length) / (pupil diameter = size of the eyebox 8) = 1 / 2 / tan(θ / 2). The smaller the F-number, the brighter the image, i.e., the larger θ, the brighter the image.

[0076] Figure 4B is a diagram showing a configuration using a small image display element 2, relay optical system 3, and screen plate 4b. In Figure 4B, the size of the image display element 2 is A / 3. In Figure 4B, a relay optical system 3 with a magnification of 3x is used to map an image onto the screen plate 4b, thereby ensuring the size of the eyebox 8. The angle of the relay optical system 3 on the screen plate 4b side is θ, the angle of the relay optical system 3 on the image display element 2 side is 3θ, and the F-number is F = 1 / 2 / tan (3θ / 2), so the relay optical system 3 has a very large aperture.

[0077] 4C is a diagram showing a configuration using a small image display element 2, a relay optical system 3, and a diffusion element unit 4. In Fig. 4C, the size of the image display element 2 is set to A / 3, but the angle of the relay optical system 3 on the image display element 2 side remains θ, and the angle of the relay optical system 3 on the diffusion element unit 4 side is set to θ / 3, and the diffusion element unit 4 diffuses the image light, thereby ensuring the size of the eyebox 8. The angle θ in Fig. 4C is made up of light incident from the image display element 2 on the upper part of the relay optical system 3 and light incident on the lower part of the relay optical system 3.

[0078] 4C, a small image display element 2 can be used without increasing the size of the relay optical system 3. Details of this diffusion element section 4 will be described with reference to FIGS. 10 to 17. Note that with respect to the vehicle, driver, or viewer, the X axis is the horizontal direction, left-right direction, lateral direction, or width direction of the vehicle, the Y axis is the up-down direction, vertical direction, or lengthwise direction of the vehicle, and the Z axis, which is perpendicular to the lateral direction of the vehicle, is the front-rear direction of the vehicle or the direction of travel of the vehicle.

[0079] In Figure 10, the X-axis and Y-axis correspond to the horizontal and vertical directions of the viewer's field of view (eye box 8). The horizontal viewing range is larger by the distance between the left and right eyes. For example, the eye box 8 may be 130 mm horizontally and 50 mm vertically. Therefore, a larger viewing range is required on the side of the diffusion element 4 corresponding to the X-axis direction compared to the side corresponding to the Y-axis direction.

[0080] In FIG. 10(1), the diffusion effect is achieved by a convex surface on the light-incident side of the microlens array 41 and a concave surface on the light-exit side of the microlens array 41. A light-shielding grating 42a is disposed on the light-incident side of the microlens array 41, and a light-shielding grating 42b is disposed on the light-exit side of the microlens array 41. In FIG. 10(2), each opening of the light-shielding grating 42a corresponds to each cell of the microlens array 41. Each opening of the light-shielding grating 42a corresponds to each microlens of the microlens array 41 and blocks light that spreads to the periphery of each cell from the focused image (spot) of light at each cell of the microlens array 41 mapped by the relay optical system 3. Although this differs depending on the panel size and resolution, for example, the aperture ratio of each pixel of the image display element 2 is approximately 50%, so that degradation of resolution is prevented by blocking the light beam of the relay optical system 3 that spreads beyond the magnification.

[0081] The light-shielding grating and the microlens array are arranged by bonding or via a structure. In Fig. 10, the diffusion element unit 4 may have a structure (holding) in which the microlens array 41 and the light-shielding gratings 42a and 42b are integrated. Furthermore, a telecentric optical design may be performed between the relay optical system 3 and the diffusion element unit 4, or a Fresnel lens may be placed immediately before the diffusion element unit 4. The relay optical system 3 also has a telecentric optical design, so that light beams of the same conditions are incident on each microlens of the microlens array 41.

[0082] Next, the basic concept for achieving different diffusion effects in the X-axis direction (horizontal direction) and Y-axis direction (vertical direction) of the microlens array 41 in order to convert an incident light beam with a circular cross-section into an exit light beam with a rectangular cross-section to match the eyebox 8 will be described with reference to Figures 11A and 11B.

[0083] FIG. 11A is a cross-sectional view of the incident light beams for each microlens of the microlens array 41 of FIG. 10(1), showing a mapping in which A0 to A5 are assigned to representative points. Similarly, FIG. 11B is a cross-sectional view of the exit light beams for each microlens of the microlens array 41 of FIG. 10(1), showing a mapping in which B0 to B5 are assigned to representative points. Since the circular shape is converted into a rectangular shape, there is left-right symmetry and top-bottom symmetry. Therefore, in the cross-sectional view of FIG. 11A, the center point is A0, and A1 to A5 are arranged at equal intervals on the outer periphery of the light beam in the first quadrant (in the range of α = 0 to 90 degrees in the figure). Similarly, there is left-right symmetry and top-bottom symmetry. Therefore, in the cross-sectional view of FIG. 11B ... The reason why the arrangement locations are different between Figures 11A and 11B is that the light beam is concentrated within the microlens array 41, so the signs of the values ​​on the X axis are reversed between the incident light beam and the outgoing light beam, and the signs of the values ​​on the Y axis are reversed.

[0084] Incidentally, when converting an incident light beam with a circular cross section into an exiting light beam with a rectangular cross section to fit the eyebox 8, if the light density is converted to a substantially constant value, significant unevenness in brightness is less likely to occur. Therefore, it is necessary to match the area ratio cut out from the circular shape with the area ratio of the corresponding rectangular shape. Because of the vertical and horizontal symmetry, in order to match the four-division of the circular shape in Figure 11A (the area of ​​the circle cut out by arcs A1 to A5 and point A0) with the four-division of the rectangular shape in Figure 11B (the area of ​​the rectangle cut out by outer peripheries B1 to B5 and point B0), point A0 on the cross section of the incident light beam corresponds to point B0 on ​​the cross section of the exiting light beam, point A1 corresponds to point B1, and point A5 corresponds to point B5.

[0085] Next, in FIG. 11A , point A3 is set at α=45 degrees, and the line segment A0-A3 further divides the four-division into two, resulting in eight divisions of the area of ​​the original circular shape. In FIG. 11B , point B3 is set at a diagonal corner of the rectangular shape, and the line segment B0-B3 further divides the four-division into two, resulting in eight divisions of the area of ​​the original rectangular shape. That is, point A3 on the cross section of the incident light beam corresponds to point B3 on the cross section of the exiting light beam. Similarly, in FIG. 11A , point A2 is set at α=22.5 degrees, and point A4 is set at α=67.5 degrees, and the line segment A0-A2 and line segment A0-A4 further divide the eight-division into two, resulting in sixteen divisions of the area of ​​the original circular shape. 11B, by setting point B2 midway between points B1 and B3 of the rectangular shape, and point B4 midway between points B3 and B5, and further dividing the eighth division into two by line segments B0-B2 and B0-B4, the area of ​​the original rectangular shape is divided into 16 parts. This can be understood from the fact that points B2 and B4 are the midpoints of the bases of the eighth-division triangles.

[0086] As described above, the points A1 to A5 are evenly arranged on the outer periphery of the cross section of the circular incident light beam, and the light density on the outer periphery of the cross section of the rectangular exiting light beam is uniform, and points A0 to A5 in Figure 11A correspond in order to points B0 to B5 in Figure 11B.

[0087] Next, the correspondence between the points inside the circular shape of the cross section of the incident light beam ( FIG. 11A ) and the points inside the rectangular shape of the cross section of the exiting light beam ( FIG. 11B ) will be described. In FIG. 11A , the circular shape including points A1 to A5 is reduced by 50%, resulting in a circular shape indicated by dotted lines, which has a surface area that is ¼ of the original circular area. Similarly, in FIG. 11B , the rectangular shape including points B1 to B5 is reduced by 50%, resulting in a rectangular shape indicated by dotted lines, which has a surface area that is ¼ of the original rectangular area. Therefore, a sequence of points similar to points A1 to A5 is placed on the dotted circular shape in FIG. 11A , and a sequence of points similar to points B1 to B5 is placed on the dotted rectangular shape in FIG. 11B , and the corresponding points are then aligned. Note that, in order to uniformize the light beam density throughout the entire light beam, different reduction ratios may be used as necessary, and the number of points placed on the periphery may be increased.

[0088] As described above, by making the points correspond to each other while keeping the area ratio the same, it is possible to make the light ray density closer to uniform in the rectangular shape of the cross section of the emitted light beam.

[0089] Next, an example of a diffusion element 4 that converts an incident light beam with a circular cross section into an outgoing light beam with a rectangular cross section and achieves nearly uniform light density will be described using Figures 12A to 14. The microlens of the diffusion element 4 in Figure 12A is configured with a single free-form lens, and Figure 12B shows its free-form surface coefficients (Equation 1). The incident light beam incident on this single free-form lens and the converted outgoing light beam will be described using Figures 13A and 13B.

[0090]

[0091] In Figure 13A, the diffusion effect of a rotationally asymmetric free-form lens (Figures 12A and 12B) with a circular cross section placed at the focusing position of an incident light beam with θ = 6 degrees results in an exit light beam with a rectangular cross section and a horizontal angle of 18.3 degrees and a vertical angle of 5.7 degrees. The size of the image plane is 3226 mm horizontally x 1001 mm vertically, achieving the same ratio as the eyebox 8, 130 mm x 40 mm. The reason for providing a 10 mm distance (Figure 12A) before and after the free-form lens is to separate the image plane to a distance where the height of the light beam at the free-form lens is negligible compared to the height of the light beam at the image plane, thereby simplifying the distribution of the light beam's exit angle in a spot diagram at the image plane. Therefore, optical elements are placed immediately before and after the actual free-form lens (microlens array 41) (Figure 8). In this example, a convex Fresnel lens is placed on the reduction side, and a concave lens 10 is placed on the magnification side. 13B, for comparison, shows the exiting light beam and the incident light beam itself when the same incident light beam as in FIG. 13A is used but without the microlens array 41. Therefore, it can be seen that in FIG. 13A, the exiting light beam has a large angle of emission in the horizontal direction, and has a rectangular cross section in both the horizontal and vertical directions.

[0092] 14 shows ray diagrams for the YZ cross section and the XZ cross section of a free-form lens, with the light beam at the entrance surface being circular and the light beam at the exit surface being vertically elongated. The difference in the size of the light beam at the entrance surface and the exit surface of the free-form lens is less than twice as large because the microlens array 41 (free-form lens) is arranged so that the cross-sectional areas of the light beam at the YZ cross section and the XZ cross section are minimized between the entrance surface and the exit surface, preventing the free-form lens from becoming too large. Furthermore, the light beam at the exit surface of the free-form lens is aligned into a vertically elongated, approximately rectangular shape, and the action of the free-form surface at the exit surface greatly widens the horizontal diffusion angle, thereby achieving a horizontally elongated rectangular shape on the image plane.

[0093] Next, using Figures 15A to 17 and 7A to 7C, we will explain another example of a diffusion element 4 that converts an incident light beam with a circular cross section into an exiting light beam with a rectangular cross section and makes the light ray density nearly uniform. The microlenses of the diffusion element 4 in Figure 15A are composed of two free-form lenses, and Figure 15B shows their free-form surface coefficients (Equation 1). The incident light beam incident on these two free-form lenses and the converted exiting light beam will be explained using Figures 16A and 16B.

[0094] In Figure 16A, the diffusion effect of a rotationally asymmetric free-form lens (Figures 15A and 15B) with a circular cross section placed at the focusing position of an incident light beam with θ = 4 degrees results in an exit light beam with a rectangular cross section and a horizontal angle of 18.5 degrees and a vertical angle of 5.8 degrees. The size of the image plane is 3262 mm horizontally x 1010 mm vertically, achieving the same ratio as the eyebox 8's 130 mm x 40 mm. The reason for providing a 10 mm distance (Figure 15A) before and after the free-form lens is to separate the image plane to a distance where the height of the light beams at the free-form lens is negligible compared to the height of the light beams at the image plane, thereby simplifying the distribution of the light beam's exit angle on the image plane in a spot diagram. Therefore, optical elements are placed immediately before and after the actual free-form lens (microlens array 41) (Figure 8). In this example, a convex Fresnel lens is placed on the reduction side, and a concave lens 10 is placed on the magnification side. 16B, for comparison, shows the exiting light beam and the incident light beam itself when the same incident light beam as in Fig. 16A is used but without the microlens array 41. Therefore, in Fig. 16A, it can be seen that the exiting light beam has a large emission angle in the horizontal direction and has a rectangular cross section in both the horizontal and vertical directions.

[0095] 17 is a ray diagram of the free-form lens in the YZ cross section and the XZ cross section, in which the light beam at the entrance surface is circular and the light beam at the exit surface is vertically elongated. The reason the size of the light beam at the entrance surface and the exit surface of the free-form lens is approximately the same is because the microlens array 41 (free-form lens) is arranged so that the cross-sectional area of ​​the light beam at the YZ cross section and the XZ cross section is minimized between the entrance surface and the exit surface, preventing the free-form lens from becoming too large. Furthermore, by aligning the light beam at the exit surface of the free-form lens to a vertically elongated shape and greatly widening the horizontal diffusion angle due to the action of the free-form surface at the exit surface, a horizontally elongated rectangular shape is achieved on the image plane.

[0096] The microlens array 41 has different radii of curvature in the XZ cross section and in the YZ cross section, and the diffusion angle in the X-axis direction is greater than the diffusion angle in the Y-axis direction. In other words, the divergence effect of each microlens in the microlens array 41 in the horizontal direction (X-axis direction) is greater than the divergence effect of each microlens in the vertical direction (Y-axis direction) of the microlens array 41. Note that the "diffusion effect" in the present invention may also be referred to as a "divergence effect."

[0097] The head-up display device of this embodiment includes a light source 1, a display panel 2, a relay optical system 3 that maps image light emitted from the display panel 2, a diffusion element unit 4 that diffuses the image light mapped by the relay optical system 3, and a concave lens 10. The device may further include a mirror 5 that reflects light diffused by the diffusion element unit 4 and passed through the concave lens 10. When the mirror 5 is included, the light reflected by the mirror 5 is projected onto a projection member such as a windshield 6 to display a virtual image. When the mirror 5 is not included, the light emitted from the concave lens 10 is projected onto a projection member such as a windshield 6 to display a virtual image. The diffusion element unit 4 includes a microlens array 41 having a plurality of microlenses, and the microlens array 41 has different optical effects in the horizontal and vertical directions of the microlens array 41, which correspond to the horizontal and vertical directions of the field of view in which the virtual image can be observed.

[0098] As a result, according to this embodiment, even if the image display element 2 is made smaller, the optical performance of the projection optical system 20b can be ensured without increasing the number of lenses, and a small head-up display device can be provided.

[0099] The image display element 2 may be a reflective image display element in addition to a transmissive liquid crystal display panel.

[0100] Furthermore, between the relay optical system 3 and the diffusion element unit 4, a telecentric optical design may be performed, or a Fresnel lens may be disposed immediately before the diffusion element unit 4.

[0101] The technology according to this embodiment can display navigation information such as destination and speed, as well as information necessary for driving such as alert information when an oncoming vehicle or pedestrian is detected, in line with the actual view through the windshield, reducing the driver's eye movement and contributing to supporting safe driving, thereby preventing traffic accidents. This contributes to the achievement of "Good health and well-being for all," one of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0102] 1...light source or backlight, 2...image display element or display panel, 3...relay optical system, 4...diffusion element section, 4b...screen plate, 5...mirror, 6...windshield, 7...virtual image surface, 8...eye box, 9...observer's eye, 20b...projection optical system, 30...head-up display device, 41...microlens array, 42a...light-shielding grating, 42b...light-shielding grating, 42c...light-shielding grating

Claims

1. An optical system comprising: a display panel; a light source that supplies light to the display panel; a relay optical system that maps the image light emitted from the display panel; and a diffusion element unit that diffuses the image light mapped by the relay optical system, wherein the diffusion element unit has different optical effects in the horizontal and vertical directions of the diffusion element unit which correspond to the horizontal and vertical directions of a viewer.

2. An optical system according to claim 1, wherein the diffusion element section comprises a microlens array, and the microlens array has different divergence effects in the horizontal and vertical directions.

3. An optical system according to claim 2, wherein the microlens array has different divergence effects on the light incident surface side and the light exit surface side.

4. An optical system according to claim 2, wherein the diffusion element portion has a light-shielding grating arranged on the light-emitting side of the microlens array.

5. An optical system according to claim 2, wherein the diffusion element section has a light-shielding grating arranged on the light incident side of the microlens array.

6. An optical system according to claim 2, wherein the diffusion element portion has a light-shielding grating arranged on the light entrance side and the light exit side of the microlens array.

7. The optical system according to claim 2, wherein the microlens array comprises a plurality of microlenses.

8. An optical system according to claim 7, wherein the microlens has a diverging effect in the horizontal direction that is greater than the diverging effect in the vertical direction.

9. The optical system according to claim 7, wherein the microlens is a decentered lens.

10. An optical system according to claim 7, wherein the diffusion element portion comprises a light-shielding grating having an opening, the opening having one or more apertures, the aperture corresponding to at least one of the microlenses.

11. An optical system according to claim 2, wherein the microlens array has a diverging effect only in the horizontal direction.

12. An optical system according to claim 2, wherein the microlens array has a diverging effect on at least one of the light entrance surface side and the light exit surface side of the diffusion element portion.

13. A head-up display device comprising: a display panel; a light source that supplies light to the display panel; a relay optical system that maps the image light emitted from the display panel; and a diffusion element unit that diffuses the image light mapped by the relay optical system, wherein the diffusion element unit has different optical effects in the horizontal and vertical directions of the diffusion element unit which correspond to the horizontal and vertical directions of a viewer.

14. A head-up display device according to claim 13, wherein the diffusion element portion comprises a microlens array, and the microlens array has different divergence effects in the horizontal and vertical directions.

15. A head-up display device according to claim 14, wherein the microlens array has different divergence effects on the light incident surface side and the light exit surface side.

16. A head-up display device according to claim 14, wherein the diffusion element portion has a light-shielding grid arranged on the light emission side of the microlens array.

17. A head-up display device according to claim 14, wherein the diffusion element portion has a light-shielding grating disposed on the light incident side of the microlens array.

18. A head-up display device according to claim 14, wherein the diffusion element portion has a light-shielding grating arranged on the light entrance side and the light exit side of the microlens array.

19. A head-up display device according to claim 14, wherein the microlens array comprises a plurality of microlenses.

20. A head-up display device according to claim 19, wherein the divergence effect of the microlenses in the horizontal direction is greater than the divergence effect in the vertical direction.

21. A head-up display device according to claim 19, wherein the microlens is a decentered lens.

22. A head-up display device according to claim 19, wherein the diffusion element portion is provided with a light-shielding grid having an opening, the opening having one or more apertures, and the apertures corresponding to at least one of the microlenses.

23. A head-up display device according to claim 14, wherein the microlens array has a diverging effect only in the horizontal direction.

24. A head-up display device according to claim 14, wherein the microlens array has a diverging effect on at least one of the light entrance surface side and the light exit surface side of the diffusion element portion.

25. An optical system comprising: a display panel; a light source that supplies light to the display panel; a relay optical system that maps image light emitted from the display panel; a diffusion element section that diffuses the image light mapped by the relay optical system; and a reflecting element that reflects the image light diffused by the diffusion element section, wherein the diffusion element section has different optical effects in the horizontal and vertical directions of the diffusion element section which correspond to the horizontal and vertical directions of a viewer.

26. The optical system according to claim 25, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a horizontal cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light beam size between the light incident surface side and the light exit surface side of each microlens is smaller than the light beam size at the light incident surface side of each microlens and the light beam size at the light exit surface side of each microlens.

27. The optical system according to claim 25, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a vertical cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light beam size between the light incident surface side and the light exit surface side of each microlens is smaller than the light beam size at the light incident surface side of each microlens and the light beam size at the light exit surface side of each microlens.

28. An optical system as described in claim 26, wherein, in the horizontal direction of the diffusion element portion, the intersection point between the horizontal coordinate on the light incident surface side of each microlens of the microlens array and the horizontal coordinate on the light exit surface side of each microlens of the microlens array is different.

29. An optical system as described in claim 27, wherein, in the vertical direction of the diffusion element portion, the intersection point between the vertical coordinate on the light incident surface side of each microlens of the microlens array and the vertical coordinate on the light exit surface side of each microlens of the microlens array is different.

30. An optical system according to claim 25, wherein the cross section of the light beam incident on said diffusion element portion is circular, and the cross section of the light beam emerging from said diffusion element portion is rectangular.

31. The optical system according to claim 30, wherein the ratio of the area obtained by dividing the circular shape is equal to the ratio of the area obtained by dividing the rectangular shape.

32. An optical system as described in claim 25, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a horizontal cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side and the light exit surface side of each microlens, and in a vertical cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side and the light exit surface side of each microlens.

33. The optical system according to claim 32, wherein when the horizontal direction of the diffusion element portion is the X-axis, the vertical direction is the Y-axis, and the optical axis of each microlens of the microlens array is the Z-axis, in the optical path between the light incident surface side and the light exit surface side of each microlens of the microlens array, the intersections of the X-coordinates on the light incident surface side and the light exit surface side of each microlens of the microlens array have opposite signs, and the intersections of the Y-coordinates on the light incident surface side and the light exit surface side of each microlens of the microlens array have opposite signs.

34. The optical system according to claim 32, wherein the cross section of the light beam incident on said diffusion element portion is circular, and the cross section of the light beam emerging from said diffusion element portion is rectangular.

35. An optical system as described in claim 34, wherein, when the horizontal direction of the diffusion element portion is the X-axis, the vertical direction is the Y-axis, and the optical axis of each microlens of the microlens array is the Z-axis, the intersection of the circular-shaped light ray and the rectangular-shaped light ray with the X-axis has opposite signs, the intersection of the circular-shaped light ray and the rectangular-shaped light ray with the Y-axis has opposite signs, and the proportion of the area divided into the circular shape is the same as the proportion of the area divided into the rectangular shape.

36. A head-up display device comprising: a display panel; a light source that supplies light to the display panel; a relay optical system that maps the image light emitted from the display panel; a diffusion element section that diffuses the image light mapped by the relay optical system; and a reflection element that reflects the image light diffused by the diffusion element section, wherein the diffusion element section has different optical effects in the horizontal and vertical directions of the diffusion element section which correspond to the horizontal and vertical directions of a viewer.

37. A head-up display device as described in claim 36, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a horizontal cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side of each microlens and the light flux size at the light exit surface side of each microlens.

38. A head-up display device as described in claim 36, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a vertical cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side of each microlens and the light flux size at the light exit surface side of each microlens.

39. A head-up display device as described in claim 37, wherein, in the horizontal direction of the diffusion element portion, the intersection point between the horizontal coordinate on the light incident surface side of each microlens of the microlens array and the horizontal coordinate on the light exit surface side of each microlens of the microlens array is different.

40. A head-up display device as described in claim 38, wherein, in the vertical direction of the diffusion element portion, the intersection point between the vertical coordinate on the light incident surface side of each microlens of the microlens array and the vertical coordinate on the light exit surface side of each microlens of the microlens array is different.

41. A head-up display device according to claim 36, wherein the cross section of the light beam incident on said diffusion element portion is circular, and the cross section of the light beam emitted from said diffusion element portion is rectangular.

42. A head-up display device according to claim 41, wherein the area ratio of the circular shape divided is the same as the area ratio of the rectangular shape divided.

43. A head-up display device as described in claim 36, wherein the diffusion element portion comprises a microlens array having a plurality of microlenses, and in a horizontal cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side and the light exit surface side of each microlens, and in a vertical cross section of the optical path from the light incident surface side to the light exit surface side of each microlens of the microlens array, there is a position where the light flux size between the light incident surface side and the light exit surface side of each microlens is smaller than the light flux size at the light incident surface side and the light exit surface side of each microlens.

44. A head-up display device as described in claim 43, wherein, when the horizontal direction of the diffusion element portion is the X-axis, the vertical direction is the Y-axis, and the optical axis of each microlens of the microlens array is the Z-axis, in the optical paths between the light incident surface side and the light exit surface side of each microlens of the microlens array, the intersections of the X-coordinates on the light incident surface side and the light exit surface side of each microlens of the microlens array have opposite signs, and the intersections of the Y-coordinates on the light incident surface side and the light exit surface side of each microlens of the microlens array have opposite signs.

45. A head-up display device according to claim 36, wherein the cross section of the light beam incident on said diffusion element portion is circular, and the cross section of the light beam emitted from said diffusion element portion is rectangular.

46. ​​A head-up display device as described in claim 45, wherein the diffusion element section comprises a microlens array having a plurality of microlenses, and when the horizontal direction of the diffusion element section is the X-axis, the vertical direction is the Y-axis, and the optical axis of each microlens of the microlens array is the Z-axis, the intersection of the circular-shaped light beam and the rectangular-shaped light beam with the X-axis has opposite signs, the intersection of the circular-shaped light beam and the rectangular-shaped light beam with the Y-axis has opposite signs, and the proportion of the area obtained by dividing the circular shape is the same as the proportion of the area obtained by dividing the rectangular shape.

47. A head-up display device as described in claim 45, wherein the divided area of ​​the cross section of the incident light beam to the circular diffusion element portion and the divided area of ​​the cross section of the outgoing light beam from the rectangular diffusion element portion are in the same ratio, and points on each divided cross section in the circular shape correspond to points on each divided cross section in the rectangular shape.