Head-up display device

Abstract

To further miniaturize a head-up display device.SOLUTION: The head-up display device comprises: a video display device 30 that has a light source and a display element and forms a video in the display element; and a virtual image optical system that displays a virtual image in front of a vehicle by reflecting light emitted from the video display device 30 with a windshield. The virtual image optical system includes a concave mirror 41 and a distortion correction lens 43, the distortion correction lens 43 is arranged between the video display device 30 and the concave mirror 41, the concave mirror 41 is arranged in a housing formed including an optical component holding exterior case 55 formed along a surface forming the outermost periphery of an effective optical path area of the video light, and the video display device 30 is attached to a part of an outer periphery of the housing.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technology for a head-up display device, and more particularly to a technology that is effective when applied to a head-up display device that projects an image onto a transparent glass plate or the like. [Background technology]

[0002] For example, in a vehicle such as an automobile, information such as vehicle speed and engine RPM is usually displayed on an instrument panel inside the dashboard. In addition, a screen for a car navigation system or the like is displayed on a display built into or installed on the dashboard. Since the driver needs to move their line of sight significantly when viewing this information, a head-up display (hereinafter sometimes referred to as "HUD") device is known as a technology for reducing the amount of line of sight movement, which projects and displays information such as vehicle speed and instructions related to the car navigation system onto the windshield or the like.

[0003] As a technology related to HUDs, for example, Japanese Patent Laid-Open Publication No. 2015-194707 (Patent Document 1) describes a display device that includes a device for displaying images and a projection optical system that projects the image displayed on the display device, thereby reducing screen distortion throughout the entire viewing area of ​​the observer and achieving a compact size. Here, the projection optical system includes a first mirror and a second mirror, arranged in this order along the optical path from the display device to the observer. The document describes how the HUD device can be made compact by configuring the device so that the relationship between the angle of incidence on the first mirror in the image long-axis direction, the angle of incidence on the first mirror in the image short-axis direction, the distance between the image display surface of the display device and the first mirror, and the horizontal width of the virtual image viewed by the observer satisfies a predetermined relationship. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-194707 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the conventional technology described in Patent Document 1 is said to enable miniaturization of the device configuration, there are limitations to miniaturization. Specifically, the technology described in Patent Document 1 requires two mirrors to be placed between the viewer and the display device. In this case, the degree of freedom in arranging the mirrors is limited in order to prevent the light beam reflected by the first mirror from being blocked by the second mirror. In other words, there are limitations to placing the two mirrors close to each other, and they must be placed at a certain distance from each other, which hinders miniaturization of the device configuration, particularly reduction in the overall volume of the device including the housing.

[0006] Therefore, an object of the present invention is to provide a head-up display device that can achieve further miniaturization of the device.

[0007] The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] Among the inventions disclosed in this application, the outline of representative inventions will be briefly explained as follows.

[0009] A head-up display device according to a representative embodiment of the present invention comprises an image display device having a light source and a display element, which displays an image on the display element and generates and emits image projection light, an image projection unit which projects the image projection light emitted from the image display device, and a housing, wherein the display element and the image projection unit are arranged in a space formed by the housing, and the display element is arranged at an angle with respect to the optical axis of the image projection unit. [Effects of the Invention]

[0010] The effects obtained by the representative inventions disclosed in this application will be briefly explained as follows.

[0011] That is, according to the representative embodiment of the present invention, it is possible to achieve further miniaturization of the head-up display device. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an outline of an example of an operation concept of a head-up display device according to a first embodiment of the present invention. [Figure 2] 1A and 1B are diagrams illustrating an example of an implementation of a head-up display device according to a first embodiment of the present invention. [Figure 3] FIG. 2 is an explanatory diagram of light rays in the head-up display device according to the first embodiment of the present invention. [Figure 4] 1(a) to 1(c) are diagrams illustrating a method for forming an exterior cover and an exterior case that constitute a housing in a head-up display device according to a first embodiment of the present invention. [Figure 5] 10A to 10C are diagrams illustrating a method for forming the exterior lid and exterior case that constitute the housing. [Figure 6] 1(a) to 1(c) are bottom, side and rear views showing the entire housing including the exterior case of the head-up display device according to the first embodiment of the present invention. [Figure 7] 1 is a diagram illustrating an overview of an example of a mounting form of a video display device according to a first embodiment of the present invention. [Figure 8] 1 is a diagram illustrating an outline of an example of a mounting form of a light guide according to a first embodiment of the present invention. [Figure 9] 1(a) and 1(b) are diagrams showing a specific example of the mounting form of a mirror driver in the first embodiment of the present invention. [Figure 10] 3A to 3C are diagrams illustrating the operating principle of the mirror driver. [Figure 11]1(a) and 1(b) are diagrams showing a specific example of a mounting form of an LED light source and a heat sink serving as a heat dissipation member thereof in Example 1 of the present invention. [Figure 12] 3A to 3C are diagrams illustrating the operating principle of the heat sink. [Figure 13] 1 is a functional block diagram showing an overview of an example of the overall configuration of a head-up display device according to a first embodiment of the present invention. [Figure 14] 1 is a diagram illustrating an outline of an example of a hardware configuration related to acquisition of vehicle information in a first embodiment of the present invention. [Figure 15] FIG. 2 is a functional block diagram illustrating details of a configuration example according to the first embodiment of the present invention. [Figure 16] 1(a) to 1(c) are diagrams showing an example of the configuration of an optical system that displays a virtual image and an overview of miniaturization of the device according to a first embodiment of the present invention. [Figure 17] 1A to 1C are diagrams illustrating an example of correction of distortion and aberration by a distortion correction lens according to a first embodiment of the present invention. [Figure 18] 10 is a flowchart outlining an example of an initial operation in the first embodiment of the present invention. [Figure 19] 10 is a flowchart outlining an example of a normal operation in the first embodiment of the present invention. [Figure 20] 10 is a flowchart outlining an example of a brightness level adjustment process according to the first embodiment of the present invention. [Figure 21] 10(a) and 10(b) are diagrams illustrating an outline of an example of an implementation form of a head-up display device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings used to explain the embodiments, the same parts are generally designated by the same reference numerals, and repeated explanations will be omitted. Meanwhile, parts designated by reference numerals in one drawing may be referred to by the same reference numerals in other drawings, although they will not be shown again. In addition, in the following examples, a head-up display (HUD) device installed in a vehicle such as an automobile will be described as an example, but the present invention can also be applied to other vehicles such as trains and airplanes. The present invention can also be applied to HUD devices used for purposes other than vehicles.

[0014] Example 1 <Summary> 1 is a diagram illustrating an example of the operational concept of a head-up display device according to a first embodiment of the present invention. In the HUD device 1 of this embodiment, an image displayed by an image display device 30 disposed in a housing 50 (or in a location detachable from the housing 50, as will be described later) is reflected by a concave mirror 41 and projected onto a windshield 3 of a vehicle 2.

[0015] Here, the projection target member is not limited to the windshield 3, but can be a combiner or other member onto which an image is projected. The image display device 30 is configured, for example, by a projector with a backlight or an LCD (Liquid Crystal Display). It may also be a self-luminous VFD (Vacuum Fluorescent Display). It may also be one that displays images on a screen using a projection device. Such a screen may be configured, for example, by a microlens array in which microlenses are arranged two-dimensionally.

[0016] The concave mirror 41 is formed, for example, by a free-form mirror or a mirror having an asymmetrical shape with respect to the optical axis. More specifically, in order to reduce distortion of the virtual image, the shape of the concave mirror 41 is such that, for example, the radius of curvature is relatively small in its upper region (i.e., the light reflected here is reflected below the windshield 3, so the distance to the viewpoint of the driver 5 is relatively short) so that the magnification is large. On the other hand, the radius of curvature is relatively large in its lower region (i.e., the light reflected here is reflected above the windshield 3, so the distance to the viewpoint of the driver 5 is relatively long) so that the magnification is small. The image display device 30 may be disposed at an angle with respect to the optical axis of the concave mirror 41 to correct the difference in image magnification and reduce the distortion itself.

[0017] By looking at the image projected onto the windshield 3, the driver 5 can see the image as a virtual image in front of the driver 5 through the transparent windshield 3. By adjusting the angle of the concave mirror 41 and adjusting the position at which the image is projected onto the windshield 3, the display position of the virtual image seen by the driver 5 may be adjusted in the vertical direction. Note that there are no particular limitations on the content displayed as a virtual image, and for example, vehicle information, navigation information, or an image of the scenery ahead captured by a camera (not shown) (such as a surveillance camera or an around viewer) can be displayed as appropriate.

[0018] In order to increase the size of the virtual image seen by the driver 5 to a practical level, it is necessary to increase the distance from the concave mirror 41 to the virtual image, which results in an increase in the dimensions of the HUD device 1. Furthermore, because the windshield 3 onto which the image is projected is usually positioned at an angle forward and backward when viewed from the driver 5, it is difficult to match the image magnification between the upper and lower parts of the virtual image.

[0019] In contrast to this, in the prior art described in the above-mentioned Patent Document 1, in addition to the concave mirror 41, an optical path folding mirror is provided between the driver 5 and the display device (image display device 30 in this embodiment), thereby reducing the optical path difference in the area where the image magnification is partially different. This is said to make it possible to reduce the partial change in image magnification (image distortion) and the volume of the device while ensuring the distance from the concave mirror 41 to the virtual image.

[0020] On the other hand, the need for two mirrors, the concave mirror 41 and the optical path folding mirror, limits the degree of freedom in arranging the mirrors, and the two mirrors must be spaced apart to a certain extent, which hinders efforts to reduce the size of the device. Furthermore, Patent Document 1 does not mention or consider at all the necessity or specific means for correcting aberrations that occur in the virtual image viewed by the driver 5.

[0021] In contrast, in the HUD device 1 of this embodiment, in order to further reduce the size of the device, the mirror for forming the virtual image is configured as a single mirror, a concave mirror 41, as shown in FIG. 1 . Furthermore, a distortion correction lens 43, for example, with at least one surface concave (having negative refractive power), is disposed as a transmissive optical element between the driver 5 and the image display device 30. This makes it possible to improve visibility by reducing distortion and aberration of the virtual image viewed by the driver 5 to a practically acceptable level while preventing the HUD device 1 from becoming larger and more complex. That is, by controlling the direction of emission of light rays to the concave mirror 41 using the distortion correction lens 43, distortion aberration is corrected in accordance with the shape of the concave mirror 41.

[0022] Furthermore, to further improve the aberration correction capability, multiple distortion correction lenses 43 may be provided. Alternatively, a curved mirror may be provided instead of distortion correction lens 43, and distortion may be reduced by bending the optical path and simultaneously controlling the position of incidence of the light beam on concave mirror 41. It goes without saying that providing an optical element optimally designed to further improve the aberration correction capability between concave mirror 41 and image display device 30 in this way does not deviate from the technical spirit or scope of the present invention.

[0023] Furthermore, by changing the thickness of the optical element such as the distortion correction lens 43 in the optical axis direction, in addition to the original aberration correction, it is also possible to change the optical distance between the concave mirror 41 and the video display device 30 and configure it to continuously change the display position of the virtual image from far to near.

[0024] On the other hand, as a factor that degrades the image quality of the HUD device 1, it is known that the video light emitted from the video display device 30 toward the concave mirror 41 is reflected on the surface of the distortion correction lens 43 disposed on the way and returns to the video display device 30, and is reflected again and superimposed on the original video light. Therefore, in this embodiment, for example, an antireflection film is formed on the surface of the distortion correction lens 43 to suppress reflection. Furthermore, it is preferable to design the shape of the distortion correction lens surface such that the reflected light returning to the video display device 30 does not extremely concentrate on a part of at least one of the incident surface and the exit surface of the video light in the distortion correction lens 43. Also, in the video display device 30, the degradation of the image quality can be reduced by disposing a polarizing plate for absorbing the reflected light from the distortion correction lens 43 as described above.

[0025] <Mounting form of HUD device> FIG. 2 is a diagram showing an outline of an example of the mounting form of a head-up display device according to an embodiment of the present invention. FIG. 2(a) is a perspective view showing an example of the appearance centered on the housing 50 of the HUD device 1. Further, FIG. 2(b) is a perspective view showing a state in which the HUD device 1 shown in FIG. 2(a) is disassembled into each component.

[0026] As shown in FIG. 2(b), the optical component holding exterior case 55 of the HUD device 1 is a member that also functions as an optical component holding member, and houses the concave mirror 41 and the distortion correction lens 43 therein, and has a configuration in which the upper part is covered by the exterior lid part 51. Each member of these optical component holding exterior case 54 and exterior lid part 51 constitutes the housing of the HUD device 1 shown in FIG. 1. And the video display device 30 is mounted on the opening of the optical component holding exterior case 55.

[0027] The exterior cover portion 51 has an opening for emitting the image light toward the windshield 3, and the opening is covered with an anti-glare plate 52 (glare trap).

[0028] The optical component holding exterior case 55 is a member that also functions to hold the concave mirror 41 and distortion correction lens 43 in the HUD device 1 shown in FIG. 1, and although details will be described later, in this embodiment, since this member holds the optical components, it is made of a material that has high heat resistance, high rigidity, and high dimensional accuracy.

[0029] <Housing or exterior case and exterior lid> In the above-described HUD device 1, focusing on the image light emitted from the image display device 30, the light is emitted from the light source, passes through the distortion correction lens 43, and travels toward the concave mirror 41, where it is reflected. The light then passes through an anti-glare plate 52 (glare trap) attached to an opening formed in the exterior cover 51, and exits the device toward the windshield 3. As shown in FIG. 3 , the image light travels along an optical path that originates from the display element (e.g., an LCD panel) 33 of the image display device 30 and travels toward the concave mirror 41. The distortion correction lens 43 increases or expands the cross-sectional area of ​​the image light as it travels along the optical path. The light then continues to be reflected by the concave mirror 41, changing the cross-section of its optical path, passing through the anti-glare plate 52 (glare trap) and toward the windshield 3. If an obstacle is present in the middle of such an optical path, part or all of the image projected by the HUD device 1 will be lost, and therefore it is important to ensure an optical path (hereinafter also referred to as an effective optical path area) inside the HUD device through which such effective light rays (for example, light rays with a predetermined amount of light or more, such as 50% or more of the maximum amount of light) pass. However, considering a typical rectangular housing that is large enough to accommodate components and the like and ensure this effective optical path, the external dimensions of the entire device will be unnecessarily large, making it impossible to reduce the volume.

[0030] Therefore, in the HUD device 1 of this embodiment, as will be described in detail with reference to FIG. 2 above and further to FIGS. 4 to 6 below, the housing 50, and in particular its optical component holding exterior case 55, is configured as follows. Note that this optical component holding exterior case 55 is a physical and functional integration of an optical component holding member and an exterior case. In other words, the concave mirror 41 and the distortion correction lens 43 are directly held in the optical component holding exterior case 55, which also functions as an exterior case.

[0031] 4(a) to 4(c) show the optical path (effective optical path area) of a light ray emitted from the display element (LCD panel) 33 of the image display device 30, which serves as a light source, enlarged by the distortion correction lens 43, and projected onto the concave mirror 41. FIG. 4(a) is a perspective view, FIG. 4(b) is a side view, and FIG. 4(c) is a top view. FIG. 5 shows the optical path (effective optical path area) of a light ray reflected by the concave mirror 41, passing through the anti-glare plate 52 (glare trap) and emerging outside the housing 50.

[0032] Therefore, in this embodiment, as shown by the dashed line in Fig. 4, optical component holding exterior case 55 is formed so as to cover the outside of the effective optical path area together with concave mirror 41. More specifically, optical component holding exterior case 55 has a shape that includes a substantially fan-shaped bottom surface portion 55b and side surfaces 55s that rise vertically upward from both side ends of the bottom surface portion so as to cover the outside of the effective optical path area from distortion correction lens 43 to concave mirror 41. Furthermore, optical component holding exterior case 55 also has a shape shown by the dashed line in Fig. 5 so as to cover the outside of the optical path of the light rays reflected by concave mirror 41 so as not to obstruct the optical path of the light rays reflected by concave mirror 41. That is, it has an intermediate bottom surface portion 55mb that is inclined relative to the bottom surface portion 55b (along the underside of the light beam area reflected by the concave mirror 41), and furthermore, an upper side surface portion 55us and a side surface portion 51s of the exterior lid portion 51 that rise vertically from the intermediate bottom surface portion 55mb are shaped to follow the side surfaces of the optical path of the light beam reflected by the concave mirror 41. In other words, the upper side surface portion 55us and the side surface portion 51s of the exterior lid portion 51 are formed to be flush with each other. In yet other words, the exterior lid portion 51 and the optical component holding exterior case 55 that constitute the above-mentioned housing 50 have a two-tiered shape that combines the shapes indicated by the dashed lines in FIGS. 4 and 5. In this example, the exterior lid portion 51 and the optical component holding exterior case 55 are assembled together, for example, by fitting them together.

[0033] Furthermore, the gap from the effective optical path area to the bottom or side surface is preferably set to a range of 1 mm or more and less than 15 mm from the effective optical path area. It is preferable that this gap be uniform throughout the entire optical path; however, the gap in some areas may be uneven and different from the gap in other areas. In other words, it is important that the bottom and side surfaces of exterior cover 51 and exterior case 55 constituting housing 50 are set within a range that does not affect the projected image.

[0034] Figures 6(a) to (c) show the entire housing including the exterior case of the HUD device 1, with Figure 6(a) being a top view, Figure 6(b) being a side view, and Figure 6(c) being a rear view. As is clear from these figures, the housing 50, which is formed as described above and is composed of the bottom surface portion 55b, side surface portion 55s, intermediate bottom surface portion 55mb, and upper side surface portion 55us, allows the effective rays of the image light to be incident on the windshield 3 at a predetermined angle without being blocked within the HUD device 1.

[0035] Other components, such as a main board 70 on which a control unit (to be described later) and a mirror driver 42 including a motor for changing the tilt angle of the concave mirror 41, are detachably attached to the outer periphery of the housing 50 including the optical component holding outer case 55 by fastening means such as screws so that they can be attached / detached. In this embodiment, the concave mirror 41 is attached to the inside of this optical component holding outer case 55 by an optical component holding member 53, and an opening for attaching the image display device 30 is formed in a part of this outer case 55. As a result, the concave mirror 41 is fixed to the outer periphery of the outer case 55 by a fastening mechanism such as screws so that it can be easily attached / detached.

[0036] Furthermore, main board 70 is fixed to the outer peripheral surface of the bottom wall of optical component holding exterior case 55, and a mirror drive unit constituted by a motor and the like is also fixed to a part of the outer peripheral surface of the bottom of exterior case 55, also by a detachable mechanism such as a screw. Note that HUD device 1 with the necessary components attached is then fixed and mounted inside the dashboard in the vehicle cabin at a position at a predetermined angle with respect to windshield (front glass) 3. Other necessary components may also be attached to the outer peripheral surface of housing 50 including optical component holding exterior case 55 and exterior lid 51.

[0037] In this embodiment, the image display device 30 is modularized and configured so that it can be attached / detached integrally to the outside of the optical component holding exterior case 55 described above with screws or the like. This makes it possible, for example, to configure the image display device 30 so that it can be replaced alone without removing or disassembling the HUD device 1 itself, greatly improving the replaceability of the image display device 30, which is a fragile component. Furthermore, by configuring the image display device 30 to be attached to the outside of the housing 50 of the HUD device 1, it is possible to improve heat dissipation to the outside, which also has the effect of reducing failures and deterioration due to heat.

[0038] Furthermore, the optical component holding exterior case 55 and exterior cover 51 described above can improve the sealing of the effective optical path area, which is the optical path of the effective light rays formed therein. This makes it difficult for dust and other particles in the air to adhere to the surfaces of optical components such as the folding mirror and concave mirror, as in conventional structures, making it possible to maintain high optical performance for a long period of time. Furthermore, by configuring the necessary components to be attached to the outside of the exterior case 54, the overall volume of the HUD device 1 can be further reduced, making it easier to install the device inside the dashboard and to replace broken components.

[0039] In addition, for example, as shown in Fig. 21(b) below, when a concave mirror 41 and a distortion correction lens 43 are held at both ends of an individual optical component holding member 53, the shape of the optical component holding member 53 viewed from the side is generally concave (or U-shaped). For example, if the side surfaces of the optical component holding member 53 shown in Fig. 21(b) are wall-shaped, the optical component holding member 53 not only holds the concave mirror 41 and the distortion correction lens 43, but also functions as an exterior case for storing them, i.e., the optical component holding exterior case 55 of this embodiment 1. By using the optical component holding exterior case 55, the HUD device 1 can be made even more compact.

[0040] Furthermore, as described above, this embodiment employs a direct optical system configuration that does not use a light path folding mirror. Therefore, it is not possible to employ a conventional technique, such as using a cold mirror (a mirror that transmits infrared light and reflects only visible light) as the light path folding mirror to suppress temperature rise inside the housing 50. Therefore, for example, an optical member such as a heat insulating film that blocks or reflects infrared light may be provided on the anti-glare plate 52 (on the image light output side), in front of the distortion correction lens 43 (on the image light output side), or in front of the image display device 30 (LCD panel) (on the image light output side). Another means for suppressing temperature rise is, for example, a polarizing plate that transmits S waves perpendicular to the incident surface and blocks P waves parallel to the incident surface. The polarizing plate may be positioned in front of the distortion correction lens 43 (on the image light output side). Furthermore, placing a polarizing plate in front of the distortion correction lens 43 can reduce the amount of sunlight (sunlight) reflected by the lens and returning to the driver's eyes.

[0041] FIG. 7 is a diagram outlining an example of an implementation of image display device 30. Here, a perspective view is shown of modularized image display device 30 disassembled into its individual components. Image display device 30 displays an image by modulating light from a backlight using a display element 33 such as an LCD panel based on a video signal input from main board 70 via flexible cable 34. The displayed image is output to a virtual image optical system (in this embodiment, distortion correction lens 43 and concave mirror 41 in FIG. 2) through an opening in optical component holding exterior case 55 in FIG. 2, and a virtual image visible to driver 5 is generated.

[0042] The light source element in the backlight is, for example, a relatively inexpensive and highly reliable LED (Light Emitting Diode) light source 31a, which is a solid-state light source. The LED light source 31a is a surface-emitting type to achieve high output. In the example of FIG. 7, it is mounted as an LED board. In this case, for example, the utilization efficiency of the divergent light is improved by using technical measures as described below.

[0043] The luminous efficiency of an LED relative to input power varies depending on the emitted light color, but is approximately 20 to 30%, with the remainder being converted into heat. For this reason, the frame 35 on which the LED light source 31a is mounted is provided with heat dissipation fins (heat sink 31b) made of a material with high thermal conductivity (e.g., a metal material such as aluminum) to dissipate heat to the outside. This effectively improves the luminous efficiency of the LED light source 31a. In particular, LEDs currently available on the market that emit red light experience a significant drop in luminous efficiency as the junction temperature increases, and the chromaticity of the image also changes. Therefore, to prioritize reducing the temperature of the LED light source 31a, it is desirable to increase the area of ​​the heat dissipation fins on the heat sink 31b to improve cooling efficiency.

[0044] 7, a light guide 32b is used to efficiently guide the divergent light from the LED light source 31a to the display element 33. In this case, to prevent the adhesion of dust and the like, it is desirable to modularize the image display device 30 by covering the entire light guide 32b, display element 33, etc. with exterior members 36a and 36b, for example.

[0045] In the example shown in FIG. 7, multiple light funnels 32a, each made of a collimating lens, are provided to capture divergent light from the LED light source 31a and convert it into parallel light. The opening of each light funnel 32a that captures the divergent light from the LED light source 31a is, for example, flat and optically connected to the LED light source 31a by inserting a medium between the light funnel 32a and the LED light source 31a, or is convex and has a focusing effect. This converts the divergent light into parallel light as much as possible, thereby reducing the angle of incidence of the light incident on the interface of the light funnel 32a. This further reduces the divergence angle after passing through the light funnel 32a, making it easier to control the light source light that is reflected by the light guide 32b and then directed toward the display element 33.

[0046] Furthermore, to improve the utilization efficiency of the divergent light from the LED light source 31a, a PBS (Polarizing Beam Splitter) is used at the junction between the light funnel 32a and the light guide 32b to convert the polarization direction into the desired direction. This improves the efficiency of light incident on the display element 33. When the polarization direction of the light from the light source is aligned in this way, it is also desirable to use a material with low birefringence for the light guide 32b. This can prevent problems such as coloring during black display when the polarization direction is rotated and the light passes through the display element 33.

[0047] The light beam from the LED light source 31a, with its divergence angle reduced, is controlled by the light guide 32b and reflected by a total reflection surface provided on the inclined surface of the light guide 32b (the surface on the exterior member 36a side in the example of FIG. 7). The light beam is then diffused by a diffuser 32c (diffuser) disposed between the display element 33 and the surface (exit surface) of the light guide 32b facing the total reflection surface, and then enters the display element 33 (LCD panel). Note that in the example of FIG. 7, the diffuser 32c is disposed between the light guide 32b and the display element 33 to diverge the light beam from the LED light source 31a, but this configuration is not limiting. Instead of disposing the diffuser 32c, for example, a similar effect can be achieved by providing a fine uneven shape on the exit surface of the light guide 32b to provide a diffusing effect.

[0048] As described above, the image display device 30 is configured to be integrally attached with screws or the like to the outer periphery of the housing 50, which includes the optical component holding exterior case 55 and the exterior cover 51. This allows the heat sink 31b, which constitutes the heat dissipation fins of the LED light source 31a, to easily come into contact with the air outside the exterior case 55, thereby enabling efficient dissipation of heat to the outside. Furthermore, by locating the heat sink 31b outside the housing 50, it is not necessary to form an opening for cooling air circulation in part of the housing 50. This improves the dustproofness of the interior and prevents condensation inside, making it possible to maintain high optical performance for a long period of time.

[0049] FIG. 8 is a diagram outlining an example of an implementation of the light guide 32b. The cross-sectional shape of a portion including the light guide 32b and the light funnel 32a is shown in schematic form. The light beam (indicated by the arrow in the figure) whose divergence angle has been reduced by the light funnel 32a passes through the joint 32d and enters the incident surface 32b_1 of the light guide 32b. Due to the effect of the cross-sectional shape of the incident surface, the divergence angle in the vertical direction (the up-down direction in FIG. 8) is controlled, and the light propagates efficiently within the light guide 32b.

[0050] Light from the light source incident through the incident surface 32b_1 is totally reflected by a total reflection prism provided on the opposing surface 32b_2 and travels toward the exit surface 32b_3. The total reflection prism has different shapes (see enlarged view) near the incident surface 32b_1 (part "B" in the figure) and near the exit surface 32b_3 (part "A" in the figure). That is, the prism is divided into steps according to the divergence angle of the light beam incident on each surface, thereby controlling the angle of total reflection at the opposing surface 32b_2. Meanwhile, for the light beam that emerges from the exit surface 32b_3 and enters the display element 33 at the downstream stage, the arrival position and energy amount of the divided light beam after reflection are controlled using the above-mentioned division dimensions on the opposing surface 32b_2 as variables so that the light quantity distribution within the exit surface 32b_3 is uniform.

[0051] 9 is a diagram showing an outline of an implementation example of a mirror driver 42 for changing the tilt angle of a concave mirror 41. Here, as shown in FIG. 9(a), the mirror driver includes at least an electric motor 422, a worm gear 423, and a plurality of gears 424 combined between the output shaft of the motor and the worm gear, within a case 421. As shown in FIG. 9(b), the mirror driver 42 is attached to the outer periphery of the housing 50, more specifically, to the lower end of the optical component holding exterior case 55, so that the worm gear 423 meshes with a worm wheel 411 formed at the lower end of the concave mirror 41, via a partial cutout.

[0052] According to the configuration of the mirror drive unit 42 described above, as shown in FIG. 10, the rotation of the electric motor 422 is converted into a desired driving force through a plurality of gears 424 and transmitted to the worm gear 423. Further, by means of the worm wheel 424 formed at the lower end of the concave mirror, the concave mirror 41 is moved in the front-rear direction while rotating about the rotation axis (see the arrow in the figure), and the concave mirror 41 can be adjusted to a desired tilt angle. In this figure, the plurality of gears 424 are shown at intervals for ease of illustration, but it will be obvious to those skilled in the art that they are actually meshed.

[0053] FIG. 11 is a diagram showing an overview of an implementation example of the LED light source 31a and the heat sink 31b that constitutes fins for its heat dissipation. Here, in FIG. 11(a), a configuration in which the heat sink 31b is integrally attached along the long side of the LED light source 31a, which is a heat-generating component, is shown. On the other hand, in FIG. 11(b), an example in which the heat sink 31b is attached to the short sides on both sides of the LED light source 31a is shown. Thus, by adopting a configuration in which the attachment position of the fins for heat dissipation of the LED light source 31a can be appropriately set, particularly as in this embodiment, the attachment position of the heat sink 31b to the housing 50 can be appropriately set to a location suitable for minimizing the overall dimensions (volume) of the device. This has the advantage of enabling miniaturization of the device and improving the degree of freedom in design.

[0054] When there is a separation between the heat sink 31b and the LED light source 31a, which is a heat-generating component, as shown in FIG. 12, it is preferable to provide a so-called heat pipe 31h, which is a heat transfer member, between them. According to this, since the heat of the LED light source 31a is transmitted to the heat sink 31b (see the arrow in the figure), efficient heat dissipation can be achieved.

[0055] <Functional Configuration of HUD Device> Fig. 13 is a functional block diagram showing an overview of an example of the overall configuration of a head-up display device according to a first embodiment of the present invention. The HUD device 1 mounted on a vehicle 2 includes various components, such as a vehicle information acquisition unit 10, a control unit 20, an image display device 30, a concave mirror 41, a mirror driving unit 42, and a speaker 60. In the example of Fig. 13, the shape of the vehicle 2 is displayed as if it were a passenger car, but the present invention is not limited to this and can be applied to any vehicle in general.

[0056] The vehicle information acquisition unit 10 is composed of information acquisition devices such as various sensors (described later) installed in various parts of the vehicle 2, and acquires and outputs vehicle information 4 by detecting various events that occur in the vehicle 2 and detecting and acquiring the values ​​of various parameters related to the driving situation at predetermined intervals. As shown in the figure, the vehicle information 4 may include, for example, speed information and gear information of the vehicle 2, steering angle information, lamp illumination information, external light information, distance information, infrared information, engine ON / OFF information, camera image information (inside / outside the vehicle), acceleration gyro information, GPS (Global Positioning System) information, navigation information, vehicle-to-vehicle communication information, and road-to-vehicle communication information.

[0057] The control unit 20 has a function of controlling the operation of the HUD device 1 and is implemented, for example, by a CPU (Central Processing Unit) and software executed thereby. It may also be implemented by hardware such as a microcomputer or FPGA (Field Programmable Gate Array). As shown in FIG. 1 , the control unit 20 drives the image display device 30 to form an image to be displayed as a virtual image based on the vehicle information 4 acquired from the vehicle information acquisition unit 10, and projects this image onto the windshield 3 by reflecting it off a concave mirror 41.

[0058] As described above, the image display device 30 is a modularized device including, for example, a projector and an LCD, and forms an image for displaying a virtual image based on instructions from the control unit 20, and projects or displays the image. The mirror driving unit 42 adjusts the angle of the concave mirror 41 based on instructions from the control unit 20, and adjusts the position of the display area of ​​the virtual image in the vertical direction. The speaker 60 outputs audio related to the HUD device 1. For example, audio guidance from a navigation system or audio output when notifying the driver 5 of a warning or the like can be output.

[0059] 14 is a diagram showing an outline of an example of a hardware configuration related to acquisition of vehicle information 4 in the head-up display device of this embodiment. Here, the hardware configuration of the vehicle information acquisition unit 10 and part of the control unit 20 is mainly shown. The vehicle information 4 is acquired, for example, under the control of an ECU (Electronic Control Unit) 21, by information acquisition devices such as various sensors connected to the ECU 21.

[0060] These information acquisition devices include, for example, a vehicle speed sensor 101, a shift position sensor 102, a steering wheel steering angle sensor 103, a headlight sensor 104, an illuminance sensor 105, a chromaticity sensor 106, a distance measurement sensor 107, an infrared sensor 108, an engine start sensor 109, an acceleration sensor 110, a gyro sensor 111, a temperature sensor 112, a wireless receiver for road-to-vehicle communication 113, a wireless receiver for vehicle-to-vehicle communication 114, a camera (inside the vehicle) 115, a camera (outside the vehicle) 116, a GPS receiver 117, and a VICS (Vehicle Information and Communication System, registered trademark (hereinafter the same)) receiver 118. It is not necessary to have all of these devices, and other types of devices may also be included. Vehicle information 4 that can be acquired by the devices provided can be used as appropriate.

[0061] The vehicle speed sensor 101 acquires speed information of the vehicle 2. The shift position sensor 102 acquires current gear information of the vehicle 2. The steering wheel angle sensor 103 acquires steering wheel angle information. The headlight sensor 104 acquires lamp illumination information relating to the ON / OFF status of the headlights. The illuminance sensor 105 and chromaticity sensor 106 acquire external light information. The distance measurement sensor 107 acquires distance information between the vehicle 2 and external objects. The infrared sensor 108 acquires infrared information relating to the presence or absence of objects in the vicinity of the vehicle 2, the distance, etc. The engine start sensor 109 detects engine ON / OFF information.

[0062] The acceleration sensor 110 and the gyro sensor 111 acquire acceleration gyro information consisting of acceleration and angular velocity as information on the attitude and behavior of the vehicle 2. The temperature sensor 112 acquires temperature information inside and outside the vehicle. The road-to-vehicle communication wireless receiver 113 and the vehicle-to-vehicle communication wireless receiver 114 respectively acquire road-to-vehicle communication information received by road-to-vehicle communication between the vehicle 2 and roads, signs, traffic lights, etc., and vehicle-to-vehicle communication information received by vehicle-to-vehicle communication between the vehicle 2 and other surrounding vehicles.

[0063] Camera (inside vehicle) 115 and camera (outside vehicle) 116 capture video images of the conditions inside and outside the vehicle, respectively, to obtain camera video information (inside vehicle / outside vehicle). Camera (inside vehicle) 115 captures, for example, the posture, eye position, and movement of driver 5. By analyzing the obtained video images, it is possible to grasp, for example, the fatigue level and line of sight of driver 5. Camera (outside vehicle) 116 also captures the surrounding conditions, such as in front of and behind vehicle 2. By analyzing the obtained video images, it is possible to grasp, for example, the presence or absence of moving objects, such as other vehicles and people, buildings, topography, road surface conditions (rain, snow, ice, unevenness, etc.), etc.

[0064] The GPS receiver 117 and the VICS receiver 118 acquire GPS information obtained by receiving GPS signals and VICS information obtained by receiving VICS signals, respectively, and may be implemented as part of a car navigation system that acquires and uses this information.

[0065] Fig. 15 is a functional block diagram showing in detail an example of the configuration of the head-up display device of this embodiment. In the example of Fig. 15, the image display device 30 is a projector, and the image display device 30 has various components such as a light source 31, an illumination optical system 32, and a display element 33.

[0066] The light source 31 is a component that generates illumination light for projection and constitutes a backlight. Examples of such components include a high-pressure mercury lamp, a xenon lamp, an LED light source, and a laser light source. It is desirable to use a solid-state light source with a long product life. For example, for an LED light source, whose light output changes little with changes in ambient temperature, it is desirable to perform polarization conversion using a PBS equipped with optical means for reducing the divergence angle of the light. In this embodiment, as shown in FIG. 5, the light source 31 is constituted by an LED light source 31a and a heat sink 31b. The light source 31 is positioned or controlled so that the direction of light incident on the display element 33 (described later) is efficiently incident on the entrance pupil of the concave mirror 41.

[0067] The illumination optical system 32 is an optical system that collects illumination light generated by the light source 31, makes the light more uniform, and irradiates the display element 33. In this embodiment, as shown in Fig. 7, the illumination optical system 32 is configured by a light funnel 32a, a light guide 32b, and a diffuser plate 32c.

[0068] The display element 33 is an element that generates the image to be projected, and can be, for example, a transmissive liquid crystal panel, a reflective liquid crystal panel, a DMD (Digital Micromirror Device) (registered trademark) panel, or the like. It is desirable to provide polarizers on the light entrance surface (i.e., the side of the light source 31 and illumination optical system 32) and the light exit surface (i.e., the side of the distortion correction lens 43 and concave mirror 41 in FIG. 1 ) of the display element 33, respectively, to enhance the contrast ratio of the image light. A high contrast ratio can be achieved by using an iodine-based polarizer with a high degree of polarization for the light entrance surface. On the other hand, a dye-based polarizer can be used for the light exit surface, ensuring high reliability even when external light is incident or the ambient temperature is high.

[0069] When an LCD panel is used as display element 33, a problem may occur in which a specific polarized wave is blocked, making the image invisible, particularly when driver 5 is wearing polarized sunglasses. To prevent this, it is desirable to place a λ / 4 plate further in front of the polarizing plate placed on the light exit surface of the LCD panel (i.e., on the side of distortion correction lens 43 and concave mirror 41) to convert image light aligned in a specific polarization direction into circularly polarized light.

[0070] More specifically, the control unit 20 includes an ECU 21, an audio output unit 22, a nonvolatile memory 23, a memory 24, a light source adjustment unit 25, a distortion correction unit 26, a display element drive unit 27, a mirror adjustment unit 28, and other units.

[0071] As shown in FIG. 15 , the ECU 21 acquires vehicle information 4 via the vehicle information acquisition unit 10, and records, stores, or reads the acquired information in the nonvolatile memory 23 or memory 24 as needed. The nonvolatile memory 23 may store setting information such as setting values ​​and parameters for various controls. The ECU 21 also generates video data related to a virtual image to be displayed as the HUD device 1 by executing a dedicated program, for example. The audio output unit 22 outputs audio information via the speaker 60 as needed. The light source adjustment unit 25 adjusts the light emission amount of the light source 31 of the video display device 30. If there are multiple light sources 31, they may be controlled individually.

[0072] Distortion correction unit 26 performs image processing to correct distortions that occur when the image generated by ECU 21 is projected onto the windshield 3 of the vehicle 2 by image display device 30. This distortion may include, for example, image distortion caused by the curvature of the windshield 3 or distortion caused by slight misalignment when the module of image display device 30 is installed. Display element drive unit 27 sends a drive signal to display element 33 according to the image data corrected by distortion correction unit 26, causing the display element 33 to generate the image to be projected. When it is necessary to adjust the position of the display area of ​​the virtual image itself, mirror adjustment unit 28 changes the angle of concave mirror 41 via mirror drive unit 42, thereby moving the display area of ​​the virtual image up or down.

[0073] <Configuration of virtual image optical system> Fig. 16 is a diagram outlining an example of the configuration of an optical system that displays a virtual image in the HUD device 1 and how the device can be made smaller. Fig. 16(a) is a diagram outlining the basic configuration of the virtual image optical system in the HUD device 1, and schematically shows the shape of a vertical cross section of the HUD device 1. For simplicity of explanation, the distortion correction lens 43 for correcting aberrations and distortion is not shown here. Also, the concave mirror 41 is simply shown as a flat mirror.

[0074] 16 shows a basic configuration in which an LCD panel is used as the display element 33 of the image display device 30, and further includes a light source 31 serving as a backlight and a concave mirror 41, all of which are housed in a housing 50. Each element of the basic configuration is positioned so that the image displayed on the display element 33 is reflected by the concave mirror 41 and is viewed as a virtual image. Also, image light generated from the images at the top, center, and bottom of the screen of the display element 33 is indicated by dotted arrows as image light R1, R2, and R3, respectively. Here, as shown in the figure, a design constraint is to position each element so that when each image light is reflected by the concave mirror 41, it does not interfere with the display element 33 and block the image light.

[0075] 16(a) to 16(c) show the state where the horizontal distance Z between the centers of concave mirror 41 and display element 33 is changed as a parameter, taking the above design constraints into consideration. From Fig. 16(a) to Fig. 16(c), the distance Z gradually decreases from Z1 to Z3, as shown, and accordingly the angle of concave mirror 41 from the horizontal plane gradually increases from α1 to α3. Similarly, the vertical dimension of concave mirror 41 also gradually increases.

[0076] When the parameter of the distance Z is changed, the height and depth of the HUD device 1 (more specifically, the housing 50) change, and the volume also changes accordingly. That is, when the distance Z is reduced, the height of the HUD device 1 increases slightly while the depth can be significantly reduced, as shown in FIG. 16(c). As a result, by reducing the volume due to the configuration of the exterior case 54 and the exterior lid part 51 that make up the housing 50 described above, and by configuring the distance Z to be smaller, the volume of the HUD device 1 (housing 50) can be further reduced, making it more compact.

[0077] On the other hand, for example, as shown in FIG. 16(c), when the distance Z is reduced (distance Z3), the difference between the distance from the top of the display element 33 to the top of the concave mirror 41 (corresponding to image light R1) and the distance from the bottom of the display element 33 to the bottom of the concave mirror 41 (corresponding to image light R3) increases. That is, reducing the distance Z reduces the volume of the HUD device 1, but increases the distortion and aberration of the virtual image generated by the concave mirror 41. To address this issue, it is desirable to move at least the positions of the display element 33 and other components in the directions indicated by the arrows in FIG. 16(c) within a range that does not interfere with the image light (particularly image light R3) and position the display element 33 and the concave mirror 41 so that the distance between them is as uniform as possible. Additionally, arranging the light source 31 and the display element 33 so that they fit within the height dimension of the concave mirror 41 would be advantageous for miniaturizing the device without unnecessarily increasing the height dimension of the housing 50.

[0078] Furthermore, in this embodiment, as described above, distortion and aberration are corrected by disposing a distortion correction lens 43 between the display element 33 and the concave mirror 41 to correct distortion of the virtual image and aberrations generated by the virtual image.

[0079] 17 is a diagram outlining an example of distortion and aberration correction using distortion correction lens 43. As shown in the diagram, by placing display element 33 (object point) inside focal point F (focal length f) with respect to point O on the optical axis of concave mirror 41, a virtual image (indicated by an arrow in the diagram) can be obtained by concave mirror 41. For ease of explanation, the diagram regards concave mirror 41 as a convex lens with the same positive refractive power, and shows the relationship between the object point, the convex lens (indicated as concave mirror 41 in the diagram for ease of explanation), and the virtual image that is generated.

[0080] In this embodiment, as described above, a distortion correction lens 43 is disposed to reduce distortion and aberrations occurring in the concave mirror 41. In this embodiment, this optical element is a transmissive optical lens, but it is not limited to a lens and may be a concave mirror. The distortion correction lens 43 is (1) When the image light from the display element 33 is incident on the reflecting surface of the distortion correction lens 43 as a telecentric light beam, the refractive power of the distortion correction lens 43 (optical lens or concave mirror) becomes almost zero. (2) When the image light from the display element 33 diverges and enters the distortion correction lens 43, the distortion correction lens 43 has a positive refractive power. (3) When the image light from the display element 33 is condensed and enters the distortion correction lens 43, the distortion correction lens 43 has a negative refractive power. In this way, the direction (angle and position) of the light beam incident on concave mirror 41 is controlled, thereby correcting distortion of the virtual image generated by concave mirror 41. Furthermore, if distortion correction lens 43 is configured as a transmissive optical lens, the interaction between the light incident surface (display element 33 side) and the light exit surface (concave mirror 41 side) corrects aberration related to imaging performance generated in the virtual image.

[0081] At this time, as described above, the distance a from the display element 33 to the concave mirror 41 and the distance b from the concave mirror 41 to the virtual image will differ between the upper and lower ends of the virtual image due to the inclination and curvature of the windshield 3. As a result, the image magnification of the virtual image visually recognized by the driver 5 will differ between the upper and lower ends.

[0082] 17 (not perpendicular, i.e., the optical axis is raised by the lens), the image magnification M'=b' / a' at the upper end of the virtual image is made to approximately match the image magnification M=b / a at the lower end of the virtual image. This reduces distortion due to the tilt of the windshield 3, etc.

[0083] Furthermore, in this embodiment, the average radius of curvature of the vertical cross-sectional shape of the distortion correction lens 43 is set to different values ​​from the average radius of curvature of the horizontal cross-sectional shape. This corrects distortion aberration caused by the optical path difference resulting from the difference between the vertical and horizontal radii of curvature of the windshield 3, as well as aberrations that degrade the imaging performance of the virtual image. In an HUD device 1 that obtains a virtual image by directly reflecting image light onto the windshield 3, correcting the aberration caused by the optical path difference resulting from the difference between the vertical and horizontal radii of curvature of the windshield 3 is the most important factor in ensuring the imaging performance of the virtual image.

[0084] Specifically, by using a free-form surface shape for the distortion correction lens 43, the degradation of the virtual image formation performance caused by differences in the radius of curvature of the windshield 3 as described above is reduced. Conventional optical designs use aspheric shapes that define the shape of the lens surface or mirror surface as a function of the distance r from the optical axis. The aspheric shape is expressed by the following equation:

[0085]

number

[0086] In contrast to this, in this embodiment, a free-form surface shape is used, which allows the shape of the surface to be defined as a function of absolute coordinates (x, y) from the optical axis. The free-form surface shape is expressed by the following equation.

[0087]

number

[0088] In this way, by using distortion correction lens 43 and controlling its cross-sectional shape and placement position, it is possible to correct the distortion and aberration of the virtual image generated by concave mirror 41. However, this presupposes that high positioning accuracy is ensured for the optical members, namely concave mirror 41 and distortion correction lens 43.

[0089] In this regard, for example, in the configuration of the HUD device 1 shown in Figure 2(b), problems can arise if the components of the housing 50, such as the exterior cover 51 and the optical component holding exterior case 55, are formed using materials that lack heat resistance, rigidity, and dimensional accuracy. For example, the positional relationship between the concave mirror 41 and the distortion correction lens 43 can deviate from the design due to factors such as the processing accuracy and work accuracy during the manufacture of the HUD device 1 and installation on the vehicle 2, and expansion and deformation due to heat during use. As a result, the accuracy of distortion and aberration correction achieved by using the distortion correction lens 43 will also decrease.

[0090] Therefore, in this embodiment, in the configuration of the HUD device 1 shown in Fig. 2(b), at least the optical component holding exterior case 55 that holds the concave mirror 41 and the distortion correction lens 43 is formed from a material that has high heat resistance, high rigidity, and high dimensional accuracy. Specifically, for example, an unsaturated polyester resin such as BMC (Bulk Molding Compound), or polycarbonate containing glass filler is used. In particular, BMC is used in this embodiment because it is thermosetting and can be molded into complex shapes using a mold.

[0091] By holding the concave mirror 41 and the distortion correction lens 43 in the optical component holding exterior case 55 made of the above-described material, the positional relationship between the concave mirror 41 and the distortion correction lens 43 can be maintained with high precision even in harsh operating environments such as high temperatures and vibrations in the vehicle 2. Note that the relative positional relationship between the concave mirror 41 and the distortion correction lens 43 is a complex three-dimensional torsional relationship, making it difficult to construct and hold the concave mirror 41 and the distortion correction lens 43 as a single unit. Therefore, in this embodiment, the concave mirror 41 and the distortion correction lens 43 are held together by the optical component holding exterior case 55.

[0092] And even if the positional relationship between the concave mirror 41 and the distortion correction lens 43 is in the three-dimensional torsional relationship as described above, the optical component holding exterior case 55 can achieve and maintain this with high precision. That is, by holding the concave mirror 41 and the distortion correction lens 43 with the optical holding member 53, which is a single intervening component formed of a material having the characteristics of high heat resistance, high rigidity, and high dimensional accuracy, the relative positional relationship is maintained with high precision. And in this embodiment, the shape of the optical component holding exterior case 55 having such characteristics is also optimized so that it can be molded as a single component by resin die molding.

[0093] Also, in this embodiment, as described above, the video display device 30 is modularized so as to be easily detachable. As a result, there may be a slight positional deviation when the video display device 30 is mounted, but this deviation can be corrected and adjusted, for example, by image processing or the like in the distortion correction unit 26 of the control unit 20 shown in FIG. 15.

[0094] <Processing Contents of HUD Device> FIG. 18 is a flowchart showing an outline of an example of the initial operation of the head-up display device of this embodiment. When the power of the HUD device 1 is turned on (S01) by turning on the ignition switch in the stopped vehicle 2, the HUD device 1 first acquires vehicle information by the vehicle information acquisition unit 10 based on an instruction from the control unit 20 (S02). Then, the control unit 20 calculates a suitable brightness level based on the external light information acquired by the illuminance sensor 105, the chromaticity sensor 106, etc. among the vehicle information 4 (S03), and controls the light emission amount of the light source 31 by the light source adjustment unit 25 to set it to the calculated brightness level (S04). For example, when the external light is bright, the brightness level is set high, and when it is dark, the brightness level is set low.

[0095] Thereafter, ECU 21 determines and generates an image (for example, an initial image) to be displayed as a virtual image (S05), distortion correction unit 26 performs processing to correct distortion of the generated image (S06), and then display element drive unit 27 drives and controls display element 33 to form the image to be projected (S07). As a result, the image is projected onto windshield 3, allowing driver 5 to view the virtual image.

[0096] When the startup and start-up of each part of the HUD device 1, including the above-mentioned series of initial operations, is completed, a HUD-ON signal is output, and the control unit 20 determines whether this signal has been received (S08). If not, the control unit 20 waits for a HUD-ON signal for a certain period of time (S09), and repeats the HUD-ON signal waiting process (S09) until it is determined in step S08 that a HUD-ON signal has been received. If it is determined in step S08 that a HUD-ON signal has been received, the HUD device 1 starts normal operation (S10), which will be described later, and the series of initial operations ends.

[0097] Fig. 19 is a flowchart outlining an example of normal operation of the head-up display device of this embodiment. In normal operation, the basic processing flow is generally similar to the initial operation shown in Fig. 18 above. First, the HUD device 1 acquires vehicle information using the vehicle information acquisition unit 10 based on an instruction from the control unit 20 (S21). Then, the control unit 20 performs brightness level adjustment processing based on external light information acquired by the illuminance sensor 105, chromaticity sensor 106, etc., among the vehicle information 4 (S22).

[0098] FIG. 20 is a flowchart outlining an example of the brightness level adjustment process of the head-up display device of this embodiment. When the brightness level adjustment process starts, first, a suitable brightness level is calculated based on the acquired ambient light information (S221). Then, by comparing the brightness level with the currently set brightness level, it is determined whether or not the brightness level needs to be changed (S222). If a change is not necessary, the brightness level adjustment process ends. On the other hand, if a change is necessary, the light source adjustment unit 25 controls the light emission amount of the light source 31 to set the changed brightness level (S223), and the brightness level adjustment process ends. Note that in step S222, even if there is a difference between the suitable brightness level calculated in step S221 and the currently set brightness level, it may be determined that a brightness level change is necessary only if the difference is equal to or greater than a predetermined threshold.

[0099] 19, thereafter, the ECU 21 changes the current image to be displayed as a virtual image as necessary based on the latest vehicle information 4 acquired in step S21, and determines and generates the changed image (S23). Note that there are many possible patterns for changing the display content based on the vehicle information 4, depending on the content of the acquired vehicle information 4 and combinations thereof. For example, there are various possible patterns, such as changing the speed display value that is always displayed because the speed information has changed, or displaying / erasing a guide arrow graphic based on navigation information, or changing the shape or display position of the arrow, etc.

[0100] Thereafter, in this embodiment, adjustment and correction processes are performed to maintain visibility, appropriateness of the display content, and the like according to the driving conditions of vehicle 2. First, if it is necessary to adjust the position of the display area of ​​the virtual image itself, a mirror adjustment process is performed in which the angle of concave mirror 41 is changed via mirror driver 42 to move the display area of ​​the virtual image up or down (S24). Then, a vibration correction process is performed to correct the display position of the image within the display area in response to vibrations of vehicle 2 (S25). Then, distortion correction unit 26 performs a process to correct distortion of the adjusted and corrected image (S26), and then display element driver 27 drives and controls display element 33 to form the image to be projected (S27).

[0101] If the power is turned off or the like as a result of the vehicle 2 being stopped or the like while the series of normal operations described above is being performed, a HUD-OFF signal is output to the HUD device 1, and the control unit 20 determines whether or not this signal has been received (S28). If the HUD-OFF signal has not been received, the process returns to step S21 and the series of normal operations is repeated until the HUD-OFF signal is received. If it is determined that the HUD-OFF signal has been received, the series of normal operations is terminated.

[0102] As described above, according to the HUD device 1 of the first embodiment of the present invention, the virtual image optical system does not use an optical path folding mirror, but instead uses a direct optical system consisting only of the concave mirror 41. To correct distortion and aberration of the virtual image generated by the concave mirror 41, a distortion correction lens 43 is disposed between the concave mirror 41 and the display element 33. Furthermore, the housing 50 of the HUD device 1 includes the exterior case 54 and the exterior cover 51, which are formed along the surface that forms the outermost periphery of the effective optical path area of ​​the image light, thereby reducing the overall volume. This configuration allows the HUD device 1 to be further miniaturized.

[0103] Furthermore, in this embodiment, the concave mirror 41 and distortion correction lens 43 are held in an optical component holding exterior case 55 made of a highly heat-resistant, highly rigid, and highly dimensionally accurate material. This makes it possible to maintain the positional relationship between the concave mirror 41 and the distortion correction lens 43 with high precision. Furthermore, the light source 31, illumination optical system 32, and display element 33 (such as an LCD panel) are modularized as the image display device 30, and configured to be detachable from part of the outer periphery of the housing 50. This improves the replaceability of the image display device 30, which is prone to malfunctions, and also improves heat dissipation.

[0104] Example 2 2(b), the above-described first embodiment is configured such that concave mirror 41 and distortion correction lens 43 are held by optical component holding exterior case 55, and these are housed inside housing 50 consisting of exterior case 54 and exterior cover 51. In this case, in order to maintain the positional relationship between concave mirror 41 and distortion correction lens 43 with high precision, at least optical component holding exterior case 55 is formed from a material with high heat resistance, high rigidity, and high dimensional precision, such as BMC, as described above.

[0105] Incidentally, the HUD device 1 of Example 2 is provided with an optical component holding member 53, which is a separate member different from the outer case 54, as a member for holding the optical components of the concave mirror 41 and the distortion correction lens 43.

[0106] 21 is a diagram showing an outline of a head-up display device of Example 2. Here, in a HUD device 1 similar to the configuration shown in Example 1 above, a concave mirror 41 and a distortion correction lens 43 are directly held by an optical component holding member 53 that is different from an exterior case 54. The optical component holding member 53 is formed from a material such as BMC that has high heat resistance, high rigidity, and high dimensional accuracy, similar to the optical component holding exterior case 55 in FIG. 2(b).

[0107] This makes it possible to achieve the same effects as those obtained by the configuration of the HUD device 1 of the first embodiment, such as maintaining the positional relationship between the concave mirror 41 and the distortion correction lens 43 with high precision.

[0108] The invention made by the inventor has been specifically described above based on the embodiments. However, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from the spirit of the invention. For example, the above embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Industrial Applicability]

[0109] The present invention can be used in a head-up display device that projects an image onto a transparent glass plate or the like. [Explanation of symbols]

[0110] 1...HUD device, 2...vehicle, 3...windshield, 4...vehicle information, 5...driver, 10...Vehicle information acquisition unit, 20...control unit, 21...ECU, 22...audio output unit, 23...nonvolatile memory, 24...memory, 25...light source adjustment unit, 26...distortion correction unit, 27...display element drive unit, 28...mirror adjustment unit, 30...image display device, 31...light source, 31a...LED light source, 31b...heat sink, 32...illumination optical system, 32a...light funnel, 32b...light guide, 32b_1...incident surface, 33...display element, 33b_2...opposing surface, 32b_3...exit surface, 32c...diffusion plate, 32d...joint, 33...display element, 34...flexible cable, 35...frame, 36a, 36b...exterior member, 41...concave mirror, 42...mirror driving unit, 43...distortion correction lens, 50...housing, 51...exterior cover portion, 51s...side portion, 52...anti-glare plate, 53...optical component holding member, 54...exterior case, 55...optical component holding exterior case, 55b...bottom portion, 55s...side portion, 55mb...middle bottom portion, 55us...upper side portion, 60...speaker, 70...Main board, 101...vehicle speed sensor, 102...shift position sensor, 103...steering wheel steering angle sensor, 104...headlight sensor, 105...illuminance sensor, 106...chromaticity sensor, 107...distance measurement sensor, 108...infrared sensor, 109...engine start sensor, 110...acceleration sensor, 111...gyro sensor, 112...temperature sensor, 113...wireless receiver for road-to-vehicle communication, 114...wireless receiver for vehicle-to-vehicle communication, 115...camera (inside vehicle), 116...camera (outside vehicle), 117...GPS receiver, 118...VICS receiver

Claims

1. A head-up display device, an image display unit having a light source and a display element, displaying an image on the display element and emitting image light; a concave mirror that projects the image light emitted from the image display unit; a housing having a bottom portion, a middle bottom portion, and a plurality of side portions; the display element and the concave mirror are disposed in a space formed by the housing, the display element is disposed at an angle with respect to the optical axis of the concave mirror; the concave mirror includes a mirror driver that drives the concave mirror; the mirror driving unit is attached so as to be located on the outer periphery of the bottom surface portion of the housing formed along a bottom surface of an optical path of image light that is emitted from the image display unit and proceeds toward the concave mirror, the intermediate bottom surface portion is formed along the lower surface of a light beam area of ​​the image light reflected by the concave mirror. Head-up display device.

2. The head-up display device according to claim 1, A head-up display device, wherein the display element is disposed inside the focal length of the optical axis of the concave mirror.

3. The head-up display device according to claim 1, the image display unit has a polarizing plate, The head-up display device has the polarizing plates disposed on the light incident surface side and the light exit surface side of the display element, respectively.

4. The head-up display device according to claim 1, The head-up display device, wherein the concave mirror is held in an exterior case consisting of the bottom portion and the plurality of side portions.

5. The head-up display device according to claim 1, A head-up display device having an optical holding member that holds the concave mirror.

6. The head-up display device according to claim 1, an opening corresponding to a light emitting surface of the display element of the video display unit is formed in a part of the housing; The video display unit is detachably attached to the housing through the opening.

7. The head-up display device according to claim 1, the concave mirror is held by a holding member or an exterior case, and has an angle adjustment mechanism; A head-up display device in which the position of the virtual image can be adjusted in the vertical direction by adjusting the angle of the concave mirror using the angle adjustment mechanism.

8. The head-up display device according to claim 1, A head-up display device, wherein the concave mirror is configured so that the radius of curvature of an area corresponding to the lower side of a vehicle's windshield or combiner is smaller than the radius of curvature of an area corresponding to the upper side of the windshield or combiner.

9. The head-up display device according to claim 1, Furthermore, a board on which a control unit for controlling the operation of each unit including the light source and the display element constituting the image display unit is mounted is attached to a part of the outer periphery of the housing. Head-up display device.

10. The head-up display device according to claim 1, The video display unit is a head-up display device, wherein at least a heat dissipation means for the light source is attached to the outer periphery of the housing in a part of the outer periphery of the housing.

11. The head-up display device according to claim 10, The heat dissipation means includes a heat sink.

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