Backlighting device and head-up display device

Abstract

Backlighting device (20) which includes: a light source (21) that emits light, a printed substrate (22) on which the light source (21) is mounted, a converging lens (23) that collects the light emitted by the light source (21) in a first direction, an adjustment device (26) that adjusts the light emitted by the converging lens (23), a first reflector that reflects the light emitted by the adjustment device in a second direction that differs from the first direction, and a display (27) which includes an image display area (27a) for generating a display image and emits the display light for reproducing the display image, wherein the image display area (27a) transmits the light reflected by the first reflector, wherein the adjusting device (26) consists of two or more optical elements for adjusting the light emitted by the converging lens (23) in accordance with the size of the image display area (27a), one of the optical elements of the adjustment device is also used as the first reflector, and the display (27) and the printed substrate (22) are configured to accommodate a portion of a second reflector, which reflects the display light emitted by the display (27), at an angle between the display (27) and the printed substrate (22).

Description

Background of the invention1. Field of invention

[0001] One or more embodiments of the present invention relate to a head-up display device and a backlight device. 2. State of the art

[0002] A head-up display device (hereinafter referred to as "HUD device") is known in the art as a display device for mounting in a vehicle (see, for example, Patent Documents 1 and 2). The HUD device includes a backlight device and more than one reflection mirror. The backlight device emits a display light to display a display image. The reflection mirror reflects the display light more than once to a windshield and projects the display light onto the windshield serving as a projection member. The display light projected onto the windshield is reflected by the windshield to an eyepoint of an occupant. Thus, the occupant sees a virtual image corresponding to the display image outside the windshield.The HUD device is mounted in a vehicle dashboard in front of the occupant, who, as the driver, sees the virtual image outside the windshield superimposed on the landscape visible in front of the vehicle. Patent document 1: JP 2012 - 203 176 A Patent document 2: JP 2008 - 268 485 A

[0003] US 2013 / 0 063 754 A1 relates to an image forming device. The image forming device includes an optical scanning device having a light source element configured to emit a light beam, an optical deflector configured to deflect the light beam two-dimensionally, a target scanning surface that is transparent and forms a two-dimensional image thereon by the light beam deflected by the optical deflector, and an optical projection system including a convex mirror and configured to magnify the two-dimensional image and project it onto a target projection surface. The target projection surface includes a reflection surface of a half mirror. The half mirror is positioned outside the image forming device and configured to transmit part of the light incident on the half mirror and reflect another part of the light incident on the half mirror.

[0004] US 2014 / 0 022 645 A1 relates to a head-up display device that can improve the efficiency of light radiation toward an eye socket, suppress the amount of brightness change for a display image affected by the movement of the viewpoint, and achieve desirable characteristics for the light distribution angle.An illumination optical system of the head-up display device includes a light source for emitting a light beam, a lens array for generating multiple images of the light source by splitting the light beam, and a field lens for irradiating on a display element at a specific angle the light beam emitted from the image of the light source generated by the lens array, wherein the lens array is arranged such that the imaging surface of the light source generated by the lens array is on the principal point side of the field lens with respect to a focal point on the object side of the field lens.

[0005] US 5,212,471 A relates to a head-up display for a vehicle comprising a windshield having first and second opposing air interfaces for partially reflecting image illumination at a predetermined air interface to create a primary virtual image visible to the vehicle operator, and a half-wave retarder disposed between the first and second air interfaces of the windshield for rotating the linear polarization of the illumination transmitted therethrough. An image illumination source delivers linearly polarized image illumination to the first air interface of the windshield at an angle selected to enhance the reflection of S-polarized light and the transmission of P-polarized light, the polarization being selected to provide S-polarized image illumination at the predetermined beam-splitting air interface. Summary of the invention

[0006] However, because the HUD device is located in the dashboard, it must be housed in a limited space and its size is subject to certain limitations. The HUD device includes a light source, a display panel for generating the display image, and a backlight device with an optical system arranged between the light source and the display panel. Because the optical path from the light source to the display panel is configured linearly in the HUD device, the size of the structure can be large, the HUD device may interfere with the dashboard or other vehicle components, and the HUD device can only be mounted on certain vehicle types.

[0007] Embodiments of the invention make reference to the above-described circumstances, and it is an object of the invention to provide a head-up display device and a backlight device that can realize a reduction in the size of the device.

[0008] The above problems are solved by a backlight device according to claim 1 and a head-up display device according to claim 4.

[0009] Furthermore, the adjusting device preferably consists of a lens member whose emission surface is formed as a concave surface, and an aspherical mirror which reflects the light emitted by the lens member to the display.

[0010] According to embodiments of the invention, the linear layout of corresponding elements from the display to the light source can be reduced by reflecting the light through the first reflector in an optical path before passing through the image display surface to generate the display image. In this way, the backlight device and the HUD device can be designed with a compact size. Brief description of the drawings Fig. 1 is an explanatory view schematically showing a state of a vehicle to which a HUD device according to a first embodiment is applied. Fig. 2 is an exploded perspective view schematically showing a configuration of the HUD device. Fig. 3 is a perspective view schematically showing the appearance of a backlight device. Fig. 4 is an exploded perspective view showing a configuration of the backlight device. Fig. 5 is an explanatory view schematically showing the main configuration of an optical system of the backlight device according to the first embodiment. Fig. 6 is an explanatory view showing the relationship between the backlight device, a folding mirror, and an aspherical mirror. Fig. 7 is an explanatory view schematically showing a main configuration of an optical system of the backlight device according to a second embodiment. Detailed Description of Exemplary Embodiments (First Embodiment)

[0011] Fig. 1 is an explanatory view schematically showing a state of a vehicle to which a head-up display (HUD) device 1 according to an embodiment is applied. Inside the vehicle, a steering wheel 2 is arranged in front of the driver, and an instrument panel 3 is arranged in front of the steering wheel 2. Furthermore, a windshield 4, through which the scenery in front of the vehicle is visible, is arranged in front of the instrument panel 3.

[0012] The instrument panel 3 is a member that divides the vehicle interior at the front of the vehicle and is formed into a desired shape. An opening 3a extending through the instrument panel 3 is arranged at a predetermined position of the instrument panel 3, and a predetermined area P of the windshield 4 is arranged above the opening 3a.

[0013] The HUD device 1 is mounted on the vehicle such that the HUD device 1 is arranged in the dashboard 3. The HUD device 1 is a device for making a predetermined display image visible to a passenger as a virtual image in a distant view. A display light L emitted from the HUD device is projected onto the windshield 4 through the opening 3a. The display light L is reflected by the windshield 4 and reaches the eye point E of a driver. Thus, the driver sees a virtual image S outside the windshield 4. The driver can simultaneously view an image (display image) of the light emitted from the HUD device 1 and the scenery ahead of the vehicle through the windshield 4 in a superimposed state.

[0014] The HUD device 1 mainly consists of a housing body 10, a backlight device 20, a folding mirror 40 and an aspherical mirror 50. Fig. 2 is an exploded perspective view schematically showing a configuration of the HUD device 1.

[0015] The housing body 10 is a housing that houses the backlight device 20, the folding mirror 40, and the aspherical mirror 50 inside and protects these members. The housing body 10 consists of an upper housing 11, a lower housing 12, and a rear cover 13. These members are integrated with each other by mounting the lower housing 12 under the upper housing 11 and the rear cover 13 under the lower housing 12. The assembly of the upper housing 11 and the lower housing 12, and the assembly of the lower housing 12 and the rear cover 13, are accomplished, for example, by screwing.

[0016] The upper case 11 forms an upper part of the case body 10 and is formed into a desired shape. The upper case 11 includes an opening 11a for irradiating the windshield 4 with the display light L. For example, the opening 11a is formed into a substantially rectangular shape. An upper plate 14 for covering the opening 11a is disposed in the upper part of the upper case 11 to intercept glare and suppress the intrusion of dust and the like into the interior of the case body 10. The upper plate 14 is a glass plate, a plastic plate, or another plate made of a transparent material. The upper plate 14 has a shape with a size larger than that of the opening 11a and is fixed to the upper case 11, for example, by means of an adhesive member 15 such as a double-sided adhesive tape.

[0017] The lower housing 12 is a box having a bottom and a predetermined receiving space. An upper part of the box is open, and the lower housing 12 is formed into a desired shape. The lower housing 12 includes a backlight base 12a for holding the backlight device 20 at a predetermined position. The backlight device 20 is screw-mounted in the backlight base 12a. Furthermore, the lower housing 12 includes a mirror base (not shown) for holding a mirror holder 51 that holds an outer peripheral surface of the aspherical mirror 50. The mirror holder 51 is mounted in the mirror base.

[0018] The mirror holder 51 for holding the aspherical mirror 50 is mounted so that it can be rotated relative to the mirror base (not shown) of the lower case 12 and can change the inclination of the aspherical mirror 50. The mirror holder 51 is connected to a motor (not shown) via a drive mechanism (not shown), so that the inclination of the aspherical mirror 50 can be adjusted by a driving force of the motor. By adjusting the inclination, the projection position of the indicator light L in the windshield 4 can be adjusted.

[0019] Furthermore, an opening 12b extending through the lower housing 12 is formed at a part of the bottom surface of the lower housing 12. A mirror shutter portion 41 is attached to the folding mirror 40 so as to overlap a rear surface side thereof. The folding mirror 40 is arranged at a desired position in the lower housing 12 by mounting the mirror shutter portion 41 in the opening 12b from the outside to the inside.

[0020] The back cover 13 is a cover disposed on a bottom surface side of the lower case 12 and covering the opening 12b. A main printed substrate 60 for controlling a display panel 27, the motor of the mirror holder 51, and an LED printed substrate 22 described below is disposed between the back cover 13 and the mirror shutter portion 41.

[0021] Fig. 3 is a perspective view schematically showing the appearance of the backlight device 20. And Fig. Fig. 4 is an exploded perspective view showing the configuration of the backlight device 20. Furthermore, Fig. 5 is an explanatory view schematically showing a main configuration of an optical system of the backlight device 20. The backlight device 20 is a device that emits the display light L for reproducing the display image and is mainly composed of LEDs 21, a lens array 23, a diffusion plate 24, a diffusion lens 25, an aspherical mirror 26, a display panel 27, and a backlight housing 30.

[0022] The LEDs 21 are mounted on the printed LED substrate 22, and the lens array 23 is arranged on the printed LED substrate 22 in correspondence with a mounting position of the LEDs 21. A heat transfer layer 28 and a heat sink 29, both described below, are laminated on a back surface side of the printed LED substrate 22. The laminated structure is mounted in the backlight housing 30 with a desired shape from the bottom surface side.

[0023] Furthermore, the diffusion plate 24, the diffusion lens 25, and the aspherical mirror 26 are arranged on the inside of the backlight housing 30 from an opening portion on the rear surface side of the backlight housing 30, and are each mounted at a desired position in a relationship that meets the optical requirements to be described below. A mirror cover 32 is mounted in the opening portion on the rear surface side of the backlight housing 30, thereby closing the opening portion.

[0024] The display panel 27 is clamped by a shield plate 31 having an opening 31a corresponding to an image display surface 27a of the display panel 27 to be mounted on a front surface side (display light emission side) of the backlight housing 30. An opening 30a of a predetermined size corresponding to the image display surface 27a of the display panel 27 is formed on the front surface side of the backlight housing 30.

[0025] The LEDs 21 form a light source for emitting light and are mounted on the printed LED substrate 22. In the embodiment, the light source consists of a plurality of (for example, five) LEDs 21. The LEDs 21 are arranged linearly at equal intervals. The plurality of LEDs 21 are arranged as shown in Fig. 4, are arranged at positions toward an edge side in a substrate region of the printed LED substrate 22. In the printed LED substrate 22, a large area is secured in a region where the LEDs 21 are not mounted. And when the printed LED substrate 22 is provided in the HUD device, the region is arranged under the folding mirror 40 described below.

[0026] The backlight device 20 further includes the heat transfer layer 28 and the heat sink 29. The heat sink 29 radiates the heat generated in the LEDs 21 and the substrate and contacts a back surface of the printed LED substrate 22, i.e., a surface opposite a mounting surface of the LEDs 21. For example, the heat sink 29 is formed by arranging a plurality of plate-shaped fins extending parallel to each other. To increase the thermal contact efficiency between the printed LED substrate 22 and the heat sink 29, the heat transfer layer 28 is provided between the printed LED substrate 22 and the heat sink 29.

[0027] The lens array 23 is formed, for example, from a translucent resin such as polycarbonate and is formed by a parallel arrangement of a plurality of lenses. In each lens, the incident surface is planar, an emitting surface is convex, and the light emitted from the LED 21 is collected in the optical axis direction (first direction) of the lens and emitted to the diffusion plate 24.

[0028] The diffusion plate 24 is formed, for example, from a translucent resin such as polycarbonate in the shape of a rectangular plate with a plate thickness of approximately 0.1 mm. The diffusion plate 24 is arranged between the lens array 23 and the diffusion lens 25 in a state substantially parallel to the LED printed substrate 22. The diffusion plate 24 diffuses the light emitted from the lens array 23 and emits the diffused light to the diffusion lens 25. The boundaries of each LED 21 and the boundaries between each lens of the lens array 23 are blurred, and unevenness in the intensity of the light is suppressed by a diffusing function of the diffusion plate 24.

[0029] The diffusion lens 25 is formed, for example, from a translucent resin such as polycarbonate, with a horizontally elongated shape in the arrangement direction of the LEDs 21. The diffusion lens 25 is arranged between the diffusion plate 24 and the aspherical mirror 26. The diffusion lens 25 has a uniform shape along the arrangement direction of the LEDs 21, with an incident surface being flat and an emission surface being formed as a concave surface. The diffusion lens 25 broadens the light emitted from the lens array 23 through the diffusion plate 24 to maintain the size of the image display area 27a of the display panel 27 and emits the light to the aspherical mirror 26.

[0030] The aspherical mirror 26 has a reflection surface formed by depositing a metal film, such as aluminum, on a resin substrate, and the reflection surface is formed as an aspherical surface. The aspherical mirror 26 is arranged in a state where it is tilted at a certain angle in an optical path of the light emitted from the diffusion lens 25, and reflects the light reflected from the diffusion lens 25 toward the display panel 27. The aspherical mirror 26 reflects the light emitted from the diffusion lens 25 in a different direction (second direction). The embodiment is configured such that the optical path from the LED 21 to the display panel 27 forms a substantially L-shape.

[0031] The aspherical mirror 26 emits the light broadened by the diffusing lens 25 with a size corresponding to the size of the image display area 27a of the display panel 27. Furthermore, the aspherical mirror 26 uniformizes the light incident on the display panel 27 through the reflection action of the aspherical mirror 26. The light emitted by the diffusing lens 25 is emitted by the aspherical mirror 26 as light that is more uniform than the incident light.

[0032] The display panel 27 is a display that includes the image display surface 27a configured as an LCD or the like and generates a display image on the display surface 27a. The display panel 27 is arranged in the optical path between the aspherical mirror 26 and the folding mirror 40. The display panel 27 transmits the light reflected by the aspherical mirror 26 from the rear surface side to the image display surface 27a and generates the display light L (see Fig. 1) for displaying the display image. The generated display light L is emitted to the folding mirror 40. The display image generated on the image display surface 27a contains information (letters, images, and the like) displayed to the occupant and is controlled by the main printed substrate 60 based on a display image signal input from a host controller.

[0033] The backlight housing 30 is arranged on the printed LED substrate 22 to cover the LEDs 21 and the lens assembly 23, with the diffusion plate 24, the diffusion lens 25, and the aspherical mirror 26 mounted at desired positions, respectively. Furthermore, the display panel 27 is mounted in the opening 30a of the backlight housing 30. The light from the LEDs 21 is incident on the display panel 27 and guided through the interior of the backlight housing 30 by means of the lens assembly 23, the diffusion plate 24, the diffusion lens 25, and the aspherical mirror 26.

[0034] Fig. 6 is an explanatory view showing the relationship between the backlight device 20, the folding mirror 40, and the aspherical mirror 50. The folding mirror 40 has a reflection surface formed by depositing a metal film such as aluminum on a resin substrate, and the reflection surface is formed to be planar. The folding mirror 40 is arranged in the optical path of the display light L emitted from the backlight device 20 in a state where it is tilted at a certain angle and reflects the display light L emitted from the backlight device 20 to the aspherical mirror 50. In the embodiment, the backlight device 20 emits the display light L from top to bottom, so that the display light L is incident on the folding mirror 40 from above.The folding mirror 40 guides the incident display light L to the aspherical mirror 50 by reflecting the display light L in a substantially horizontal direction.

[0035] The aspherical mirror 50 has a reflection surface formed by depositing a metal film such as aluminum on a resin substrate, and the reflection surface is formed as an aspherical surface. The aspherical mirror 50 is disposed in the optical path of the display light L emitted from the folding mirror 40 in a state where it is tilted at a certain angle and reflects the display light L emitted from the folding mirror 40 toward the windshield 4. In the embodiment, the display light L is incident on the aspherical mirror 50 in the horizontal direction, the aspherical mirror 50 reflects the incident display light L toward the windshield 4 side (substantially upward), and the display light L is guided toward the windshield 4. The aspherical mirror 50 also has a function of broadening the display light L from the folding mirror 40 to a desired size.

[0036] The backlight device 20 according to the embodiment includes a plurality of LEDs 21 (light source) for emitting light, the lens array 23 (converging lens) for converging the light emitted by the plurality of LEDs 21 in the first direction, the adjusting means for adjusting the light emitted by the lens array 23, the first reflector for reflecting the light emitted by the adjusting means in the second direction different from the first direction, and the display panel 27 (display) for emitting the display light L for displaying the display image, wherein the light reflected by the first reflector passes through the image display surface 27a. Furthermore, the adjusting means consists of two or more optical elements for adjusting the light emitted by the lens array 23 in accordance with the size of the image display surface 27a.One of the optical elements of the adjustment device is also used as the first reflector.

[0037] The linear layout of corresponding elements from the display panel 27 to the LEDs 21 can be reduced by folding the optical path in the backlight device 20 by the first reflector. Furthermore, because one of the optical elements of the adjustment device is also used as the first reflector, a dedicated optical element does not need to be provided as the first reflector, and the configuration from the LEDs 21 to the first reflector can be made compact. Therefore, the backlight device 20 can be made compact, and the HUD device 1 with the backlight device 20 incorporated therein can be made compact. In this way, interference with the instrument panel 3 or other vehicle components mounted in the vehicle interior can be suppressed.And because the HUD device 1 can be arranged in a compact receiving space, the HUD device can be mounted on a wider range of vehicle types.

[0038] The HUD device 1 according to the embodiment includes the plurality of LEDs 21 (light source) for emitting light, the lens array 23 (converging lens) for converging the light emitted by the plurality of LEDs 21 in the first direction, the adjusting device for adjusting the light emitted by the lens array 23, the first reflector for reflecting the light emitted by the adjusting device in the second direction different from the first direction, the display panel 27 (display) for emitting the display light L, the light reflected by the first reflector being transmitted through the image display surface 27a, the folding mirror 40 (second reflector) for reflecting the incident display light by allowing the display light L emitted by the display panel 27 to be incident from above,and the aspherical mirror 50 (third reflector) for reflecting the display light incident from the folding mirror 40 to the windshield 4 (projection member). The adjusting device adjusts the light emitted by the lens assembly 23 in accordance with the size of the image display area 27a.

[0039] As described above, because the HUD device 1 is covered by the instrument panel 3, the HUD device 1 must be housed in a limited space, and certain restrictions are imposed on its size. The HUD device 1 of the embodiment is configured such that the display light L is emitted toward the folding mirror 40 positioned at the lower part. Therefore, if the layout of the respective elements from the LEDs 21 to the display panel 27 is provided linearly, the size of the device is increased upward because the respective elements from the display panel 27 to the LEDs 21 are arranged from bottom to top.

[0040] Furthermore, in the HUD device 1, the layout requirements of the display panel 27 are determined depending on the distance to the virtual image S visible to the driver, and the arrangement position of the HUD device 1 is determined depending on the layout requirements. In this case, the HUD device 1 is likely to be arranged adjacent to the instrument panel 3, and the size of the device may increase toward the top, possibly causing interference with the instrument panel 3 and requiring a large accommodation space. Therefore, a problem arises that the HUD device can only be mounted on certain vehicle types.

[0041] Accordingly, in the HUD device 1 according to the embodiment, the optical path from the LEDs 21 to the display panel 27 is configured to be folded from the first direction to the second direction by the first reflector. The linear layout of corresponding elements from the display panel 27 to the LEDs 21 can be reduced by folding the optical path by the first reflector. In this way, the size of the HUD device 1 can be made compact in the upward direction. Furthermore, because it does not interfere with the instrument panel 3 and does not require a large accommodation space, the problem that the HUD device 1 can only be mounted on certain types of vehicles can be solved.

[0042] Furthermore, in the embodiment, the adjusting means includes a function for uniforming the intensity distribution of the light incident on the image display surface 27a.

[0043] According to this configuration, the occurrence of unevenness in the intensity distribution of the light incident on the image display surface 27a can be prevented. Thus, a uniform intensity distribution of the light incident on the image display surface 27a is provided. This suppresses shadowing in the light of the virtual image S and improves visibility.

[0044] Furthermore, in the embodiment, the adjusting device consists of two or more optical elements, wherein one of the optical elements of the adjusting device is also used as the first reflector.

[0045] Because the adjustment device is also used as the first reflector in the configuration, no dedicated optical element needs to be provided as the adjustment device. Therefore, the configuration from the LEDs 21 to the first reflector can be made compact. This allows the entire device to be made compact.

[0046] In the HUD device 1 and the backlight device 20 of the embodiment, the adjusting means is composed of the diffusion lens 25, which is a lens member whose emission surface is formed as a concave surface, and the aspherical mirror 26, which reflects the light emitted from the diffusion lens 25 to the display panel 27.

[0047] In this configuration, the light emitted by the diffusion lens 25 is reflected by the aspherical mirror 26, making it possible to uniformize the intensity distribution of the light incident on the image display surface 27a. This suppresses the occurrence of unevenness in the intensity distribution of the light incident on the image display surface 27a. Thus, a uniform intensity distribution of the light incident on the image display surface 27a can be achieved. This suppresses shadows in the light of the virtual image S, and visibility can be improved.

[0048] Furthermore, because the aspherical mirror 26 also functions as an adjustment device, the diverging lens 25 can be implemented as a lens with a concave emission surface. Because the thickness of the diverging lens 25 can be reduced in the optical axis direction, the entire device can be made compact.

[0049] Furthermore, in the embodiment, the HUD device 1 and the backlight device 20 include the LED printed substrate 22 on which the plurality of LEDs 21 are mounted, the heat sink 29 (heat radiation member) that thermally contacts the LED printed substrate 22, and the backlight case (housing) 30 in which the display panel 27 arranged on the LED printed substrate 22 is mounted and which is provided to cover the plurality of LEDs 21. Here, the LED printed substrate 22 and the heat sink 29 extend in the emission direction of the display light L and are housed in the lower part of the folding mirror 40.

[0050] Because in the HUD device 1, the light emitted by the LEDs 21 reaches the occupant's eye point through the plurality of optical elements, the light intensity is attenuated in the process. Furthermore, in recent years, colored display panels 27 have been increasingly used, so the attenuation of the light by the display panel 27 is large. Thus, the high output of the light source is attenuated, and an increased number of mounted LEDs 21 and an increased output of the LEDs 21 increase the heat generated by the LEDs 21. Therefore, the size of the heat sink 29 must be increased. Furthermore, because the heat sink 29 is arranged on a rear surface of the printed LED substrate 22, the size of the backlight device 20 with the backlight housing 30 contained therein must also be increased upward.

[0051] The linear layout of corresponding elements from the display panel 27 to the LEDs 21 can be reduced by folding the optical path in the backlight device 20 by the aspherical mirror 26. Therefore, since corresponding elements from the diffusion lens 25 to the heat sink 29 do not extend in the upward direction, the backlight device 20 and the HUD device 1 can be provided compactly in the upward direction. Because no interference with the instrument panel 3 is caused and no large accommodation space is required, the problem that the HUD device 1 can only be mounted on certain vehicle types can be solved.

[0052] Furthermore, in the embodiment, since the printed LED substrate 22 and the heat sink 29 extend in the emission direction of the display light L, a large radiation area can be ensured. By ensuring the radiation area, the sizes of the printed LED substrate 22 and the heat sink 29 can be increased. Therefore, the entire backlight device 20 is configured in a substantially L-shape, with the printed LED substrate 22 and the heat sink 29 extending in the emission direction of the display light L. Due to the substantially L-shape, the extended portions of the printed LED substrate 22 and the heat sink 29 can be effectively utilized with a space in the lower part of the folding mirror 40. This can suppress the upward enlargement of the backlight device 20 while ensuring heat radiation efficiency. (Second embodiment)

[0053] Fig. 7 is an explanatory view schematically showing a main configuration of an optical system of a backlight device 20 according to a second embodiment. The HUD device 1 and the backlight device 20 according to the second embodiment differ from those of the first embodiment in that a first reflector and an adjusting device are each composed of separate optical elements. Hereinafter, repeated descriptions of the identical parts to those in the first embodiment will be omitted, and differences from the first embodiment will be described primarily.

[0054] In the embodiment, the backlight device 20 is a device that generates a display light L for displaying a display image and is mainly composed of LEDs 21, a lens array 23, a diffusion plate 24, a diffusion lens 33, a flat mirror 34 and a display panel 27.

[0055] The diffusion lens 33 is formed, for example, from a translucent resin such as polycarbonate and has a horizontally elongated shape in the arrangement direction of the LEDs 21. The diffusion lens 33 is arranged between the diffusion plate 24 and the flat mirror 34. The diffusion lens 33 has a uniform shape along the arrangement direction of the LEDs 21, with an incident surface formed as a concave surface and an emission surface formed as a convex surface. The diffusion lens 33 broadens the light emitted from a lens array 23 through the diffusion plate 24 at the incident surface and emits the light broadened by the incident surface with a size corresponding to the size of the image display area 27a of the display panel 27 at the emission surface.

[0056] Furthermore, the diffusing lens 33 also has a function of uniforming the light incident on the display panel 27. The light emitted from the lens array 23 is reflected through the diffusing lens 33 to the flat mirror 34, providing more uniform light than the incident light.

[0057] The flat mirror 34 is formed as a reflection surface by depositing a metal film such as aluminum on a resin substrate, thereby forming the reflection surface flat. The flat mirror 34 is arranged in an optical path of the light emitted from the diffusion lens 33 in a state where it is tilted at a certain angle and reflects the light emitted from the diffusion lens 33 toward the display panel 27. The flat mirror 34 reflects the light emitted from the diffusion lens 33 in a different direction (second direction). Similar to the first embodiment, the optical path from the LEDs 21 to the display panel 27 is configured in a substantially L-shaped manner.

[0058] In the above-described embodiment, the linear layout of each element from the display panel 27 to the LEDs 21 can be reduced by folding the optical path in the backlight device 20 by the flat mirror 34. Since the elements from the diffusion lens 33 to the LEDs 21 do not extend in the upward direction, the backlight device 20 and the HUD device 1 can be formed compactly in the upward direction. Therefore, since no interference with the instrument panel 3 is caused and no large accommodation space is required, the problem that the HUD device 1 can only be mounted in certain types of vehicles can be solved.

[0059] While HUD devices according to embodiments of the invention have been described above, the invention is not limited to the above-described embodiments, and various modifications may be made thereto without departing from the scope of the invention. In addition to the HUD device, the backlight device in the HUD device also constitutes part of the invention.

[0060] In the embodiments described above, the display light is projected from the backlight device 20 onto the windshield 4, but it could also be projected onto a projection member other than the windshield 4, and a combiner could also be used. Furthermore, in a half-mirror structure for displaying a virtual image on a transparent cover in front of a measuring device, the transparent cover can be used as the projection member.

Claims

[1] Backlight device (20) comprising: a light source (21) which emits light, a printed substrate (22) on which the light source (21) is mounted, a converging lens (23) which collects the light emitted by the light source (21) in a first direction, an adjusting device (26) which adjusts the light emitted by the converging lens (23), a first reflector that reflects the light emitted by the adjusting device in a second direction different from the first direction, and a display (27) including an image display surface (27a) for generating a display image and emitting the display light for reproducing the display image, wherein the image display surface (27a) transmits the light reflected by the first reflector, wherein the adjusting device (26) consists of two or more optical elements for adjusting the light emitted by the converging lens (23) in accordance with the size of the image display area (27a), one of the optical elements of the adjusting device is also used as the first reflector, and the display (27) and the printed substrate (22) are configured to receive a portion of a second reflector, which reflects the display light emitted by the display (27), in an inclined manner between the display (27) and the printed substrate (22). [2] Backlight device according to claim 1, wherein the adjusting device (26) consists of: a lens member (25) whose emission surface is formed as a concave surface, and an aspherical mirror (26) which reflects the light emitted by the lens member (25) to the display (27). [3] The backlight device according to claim 1, further comprising: a heat radiation member (29) thermally contacting the printed substrate (22); and a housing (30) arranged on the printed substrate (22) so as to cover the light source (21) and in which the display (27) is mounted. [4] A head-up display device (1) in which a display light for displaying a display image is projected onto a projection member (4) so that an occupant sees the display image, the head-up display device (1) comprising: the backlight device (20) according to one of claims 1 to 3; a second reflector (40) which reflects the display light emitted by the display and incident from above and is provided between the display (27) and the printed substrate (22), and a third reflector (50) which reflects the display light incident from the second reflector to the projection member (4). [5] A head-up display device (1) according to claim 4, wherein the adjusting means (26) uniforms the intensity distribution of the light incident on the image display surface (27a). [6] A head-up display device (1) according to claim 4 or 5, wherein the printed substrate (22) and the heat radiation member (29) extend in the emission direction of the display light and are accommodated below the second reflector (40).

Images