Patent Description:
In vehicles such as automobiles, a head-up display apparatus for displaying information for a user on a windshield has been becoming widespread. A head-up display apparatus projects certain information onto a combiner composed of a transparent substrate or onto a windshield, so that a user such as a driver visually can recognize a virtual image. Further, in order to improve the usefulness of such a head-up display apparatus, a technique for displaying a plurality of virtual images at places having different distances from a user's viewpoint has been developed.

In a head-up display apparatus disclosed in Patent Literature <NUM>, a lens is disposed in a part of a light-emitting surface of a drawing device for generating display light, and a virtual image formed by light that passed through the lens and a virtual image that is formed by light that does not pass through the lens are recognized as if they are located at places having different distances from a user's viewpoint.

Further, in a display apparatus disclosed in Patent Literature <NUM>, a self-luminous type display panel is disposed in a reflection member that reflects projected display light. Further, a virtual image formed by reflected display light and a virtual image displayed by the self-luminous type display panel are recognized as if they are located at places having different distances from a user's viewpoint.

Patent Literature <NUM> and its US counterpart, Patent Literature <NUM>, disclose a head-up display apparatus, where, in order to display a first virtual image, a first image display device projects a first image onto a windshield via a glare trap part, and in order to display a second virtual image having a different display distance, a second image display device generates a second image on a functional film, mounted on a glare trap part, and projects the second image onto the windshield.

Patent literature <NUM> discloses a head-up display is mounted to a vehicle having a windshield, including a display element configured to display an image, a first optical system configured to reflect the image displayed by the display element and project the image onto the windshield; and a second optical system configured to reflect the image displayed by the display element and project the image onto the windshield. The image projected with the first optical system is projected onto the windshield at a position below a position of the image projected with the second optical system.

Patent Literature <NUM> and its US counterpart, Patent Literature <NUM>, disclose a head-up display which projects display light on a transmission/reflection part to display a first virtual image in an area in which the virtual image can be displayed, said area being superimposed on an actual view outside of a vehicle, wherein, when deviation occurs in the relative positions of the actual view and the transmission/reflection part from the perspective of a viewer, a control unit enlarges a virtual image display area, which sets the range in which the first virtual image is displayed within the area in which the virtual image can be displayed, so as to be larger than normal.

However, in the technique disclosed in Patent Literature <NUM>, since a screen image generated by one drawing device is divided into two images, there is a limit to the size of each of the virtual images. Further, if two drawing devices are disposed in order to eliminate the limitation in regard to the size of each virtual image, the size of the device may increase. In the technique disclosed in Patent Literature <NUM>, when an image generated by the self-luminous type display panel is displayed as a virtual image, the maximum size of the virtual image becomes the actual size of the display panel, so that the expandability thereof is poor. Further, in order to display an image on the self-luminous type display panel in an enlarged manner, a combiner is required for the virtual-image projection surface.

An embodiment according to the present disclosure has been made in order to solve the above-described problem, and provides a head-up display apparatus of which the degree of freedom in designing is high and the expandability is excellent.

A head-up display apparatus according to an embodiment projects a plurality of virtual images of which depths perceived by a user with respect to a virtual-image display unit disposed in front of the user are different from each other. The head-up display apparatus includes a first projection apparatus and a second projection apparatus. The first projection apparatus includes a first display-light emitting unit configured to emit first display light, and a concave mirror configured to reflect the first display light and thereby emit reflected light thereof, and the first projection apparatus is configured to enable the user to perceive a first virtual image by projecting the reflected light onto a virtual-image display unit. The second projection apparatus includes a second display-light generation unit configured to let the reflected light pass therethrough and generate second display light different from the first display light, and the second projection apparatus is configured to enable the user to perceive a second virtual image by projecting the generated second display light onto the virtual-image display unit.

According to the embodiment, it is possible to provide a head-up display apparatus of which the degree of freedom in designing is high and the expandability is excellent.

For clarifying the explanation, the following description and the drawings are partially omitted and simplified as appropriate. The same reference numerals (or symbols) are assigned to the same elements throughout the drawings and redundant explanations thereof are omitted as appropriate.

Embodiments according to the present invention will be described hereinafter with reference to the drawings. A head-up display apparatus according to this embodiment is an apparatus that projects a plurality of virtual images of which depths perceived by a user with respect to a virtual-image display unit disposed in front of the user are different from each other. More specifically, a head-up display apparatus according to this embodiment is an apparatus that is installed in an automobile, and is an apparatus that displays information for a driver, i.e., a user, by projecting a virtual image onto a windshield of the automobile or onto a combiner using the windshield or the combiner as a virtual-image display unit.

A configuration of the head-up display apparatus according to the first embodiment will be described with reference to <FIG> is a schematic diagram showing the configuration of the head-up display apparatus according to the first embodiment. <FIG> schematically shows an automobile <NUM>, a user U of the automobile <NUM>, and a head-up display apparatus <NUM>. Note that, in <FIG>, a right-handed orthogonal coordinate system is shown for the sake of convenience for explaining a positional relation among components. In the drawings, the X-axis coincides with the longitudinal direction of the automobile <NUM>, and the X-axis positive direction coincides with the direction from the front of the automobile <NUM> toward the rear thereof. The Y-axis coincides with the left/right direction of the automobile <NUM>, and the Y-axis positive direction coincides with the direction from the left of the automobile <NUM> toward the right thereof. The Z-axis coincides with the vertical direction of the automobile <NUM>, and the Z axis positive direction coincides with the direction from the bottom of the automobile <NUM> to the top thereof. Further, in <FIG> and the subsequent drawings, when an orthogonal coordinate system is shown, the X-, Y-, and Z-axis directions in <FIG> coincide with the X-, Y-, and Z-axis directions in that orthogonal coordinate system, respectively.

As shown in the figure, the head-up display apparatus <NUM> is housed in a dashboard of the automobile <NUM> and projects a first virtual image V101 and a second virtual image V102 onto a windshield WS. The head-up display apparatus includes, as its main components, a first projection apparatus <NUM> and a second projection apparatus <NUM>.

The first projection apparatus <NUM> projects the first virtual image V101 onto the windshield WS. The first projection apparatus <NUM> includes, as its main components, a first display-light emitting unit <NUM>, a reflecting mirror <NUM>, and a concave mirror <NUM>.

The first display-light emitting unit <NUM> includes a first light source <NUM> and a first image display unit <NUM>. The first display-light emitting unit <NUM> generates a first display light L10 by making light emitted from the first light source <NUM> pass through the first image display unit <NUM>, and emits the generated first display light L10. The first display light L10 is display light for forming the first virtual image V101, and contains information to be displayed as the first virtual image V101 for the user U. The first light source <NUM> is composed of, for example, an LED(s) (Light Emitting Diode(s)) or a lamp. Further, the first image display unit <NUM> is composed of a transmission-type liquid-crystal panel or the like. The first display-light emitting unit <NUM> projects the generated first display light L10 onto the reflecting mirror <NUM>. The reflecting mirror <NUM> reflects the first display light L10 received from the first display-light emitting unit <NUM> and projects the reflected light onto the concave mirror <NUM>.

The concave mirror <NUM> generates reflected light L11 as the mirror having the concave shape receives and reflects the first display light L10 received through the reflecting mirror <NUM>. The concave mirror <NUM> is configured so as to project the reflected light L11 onto the windshield WS. Further, in the concave mirror <NUM>, the curved surface is formed so that the reflected light L11 projected by the concave mirror <NUM> forms an image having no distortion as viewed from the user U. Further, the first display light L10 is projected in a magnified manner by the concave mirror <NUM>. Therefore, the first virtual image V101 perceived by the user U is larger than the image displayed by the first image display unit <NUM>. Further, the reflected light L11 projected by the concave mirror <NUM> is projected onto the windshield WS after passing through a second display-light generation unit <NUM> (which will be described later). By the above-described configuration, the first projection apparatus <NUM> enables the user U to perceive the first virtual image V101.

Further, the concave mirror <NUM> includes a drive unit (not shown) that rotates the concave mirror <NUM> around a shaft <NUM> parallel to the Y-axis over a predetermined angle by using the shaft <NUM> as a fulcrum. As the drive unit rotates the concave mirror <NUM>, the concave mirror <NUM> can change the direction of the reflected light L11. In this way, the head-up display apparatus <NUM> can suitably adjust the change in the place where the first virtual image V101 is displayed, which is caused as the height of the viewpoint of the user U changes.

The second projection apparatus <NUM> projects the second virtual image V102 onto the windshield WS. The second projection apparatus <NUM> includes, as its main components, the second display-light generation unit <NUM> and an excitation-light emitting unit <NUM>.

The second display-light generation unit <NUM> lets the reflected light L11 generated by the first projection apparatus <NUM> pass therethrough, and generates second display light L21 different from the first display light L10. The second display light L21 generated by the second display-light generation unit <NUM> is projected onto the windshield WS, and thereby enables the user U to perceive the second virtual image V102.

The second display-light generation unit <NUM> is formed by using a plate-like transparent member having a concavely-curved upper surface as a substrate. In order to make the above-described reflected light L11 generated by the first projection apparatus pass the substrate, highly-transparent plastic such as polycarbonate or acryl, or highly-transparent glass is used for the substrate. By the concavely-curved upper surface, the second display-light generation unit <NUM> prevents external light coming from the outside of the automobile <NUM> from being reflected thereon into the interior of the vehicle. Further, the second display-light generation unit <NUM> prevents foreign substances from entering the head-up display apparatus <NUM>. Note that the second display-light generation unit <NUM> is also referred to as a clear cover.

The second display-light generation unit <NUM> will be further described with reference to <FIG> is a cross-sectional view of the second display-light generation unit in the head-up display apparatus according to the first embodiment. The second display-light generation unit <NUM> is composed of, as viewed from the top, a coating layer <NUM>, a substrate <NUM>, and a self-luminous layer <NUM>. The coating layer <NUM> is an AR (Anti-Reflection) coating that suppresses reflection of light and reflection of images. Further, the coating layer <NUM> may be one having a scratch-resisting function.

The substrate <NUM> is formed of a transparent polycarbonate material. Further, the substrate <NUM> has a thickness of, for example, about <NUM> millimeter in order to suppress unintended refraction which would otherwise occur when the reflected light L11 projected from the first projection apparatus <NUM> passes therethrough.

The self-luminous layer <NUM> contains a self-luminous material 140A in a binder material having a high visible-light transmittance. The self-luminous material 140A is a material that emits fluorescence, which is visible light, by receiving specific excitation light. Further, the specific excitation light is light having a specific frequency. For example, the specific excitation light is ultraviolet light. That is, the self-luminous material 140A in this embodiment is a material that emits fluorescence when it receives ultraviolet light having a specific frequency. Note that the position of the self-luminous material 140A is not limited to the lower layer of the second display-light generation unit <NUM>, but may be an intermediate layer and/or an upper layer thereof.

Next, the excitation-light emitting unit <NUM> of the second projection apparatus <NUM> will be described with reference to <FIG> is a schematic diagram showing a configuration of an excitation-light emitting unit according to the first embodiment. The excitation-light emitting unit <NUM> is a laser projector apparatus that projects ultraviolet laser light, which serves as excitation light, onto the second display-light generation unit <NUM>. The excitation-light emitting unit <NUM> includes, as its main components, a control unit <NUM> and a laser light emitting unit <NUM>. The control unit <NUM> includes a CPU (Central Processing Unit), a driver IC (Integrated Circuit), and the like, and has a function of appropriately controlling each component of the laser light emitting unit <NUM>.

The laser light emitting unit <NUM> includes a laser light source unit <NUM> and a laser scanning unit <NUM>. The laser light source unit <NUM> includes a laser diode(s) 153LD, a mirror <NUM>, and a photodetector 153PD. The laser diode 153LD generates ultraviolet laser light at a predetermined timing according to an instruction from the control unit <NUM>, and supplies the generated ultraviolet laser light to the mirror <NUM>. The mirror <NUM> lets part of the ultraviolet laser light received from the laser diode 153LD pass therethrough and thereby outputs that part of the ultraviolet laser light, and reflects and supplies other part of the ultraviolet laser light to the photodetector 153PD. The photodetector 153PD detects (i.e., measures) the intensity of the ultraviolet laser light supplied from the mirror <NUM>, and feeds back a signal that is generated based on the detection to the control unit <NUM>.

The laser scanning unit <NUM> generates excitation light L20 from the ultraviolet laser light received from the laser light source unit <NUM>. The laser scanning unit <NUM> includes a first scanner mirror <NUM> and a second scanner mirror 154V. The first scanner mirror <NUM> makes the ultraviolet laser light perform to-and-fro movements over a predetermined angle along the horizontal scanning line of the second virtual image V102. The second scanner mirror 154V makes the ultraviolet laser light perform to-and-fro movements over a predetermined angle along the vertical scanning line of the second virtual image v102. The laser scanning unit <NUM> generates surface excitation light L20 by appropriately performing the scanning operations of the ultraviolet laser light, which is supplied from one point and travels in a straight line, along the two scanning lines orthogonal to each other.

By the above-described configuration, the excitation-light emitting unit <NUM> generates excitation light for forming the second virtual image V102, and projects the generated excitation light onto the second display-light generation unit <NUM>. Further, when the excitation light is projected from the excitation-light emitting unit <NUM> onto the second display-light generation unit <NUM> as described above, a part of the second display-light generation unit <NUM> on which the excitation light is incident emits fluorescence. Then, the fluorescence emitted by the second display-light generation unit <NUM> is projected onto the windshield WS and is perceived by the user U as the second virtual image V102.

The description will be continued by referring to <FIG> again. As described above, the head-up display apparatus <NUM> projects each of the reflected light L11 generated by the first projection apparatus <NUM> and the second display light L21 generated by the second projection apparatus <NUM> onto the windshield WS. Note that, as shown in the figure, the length of the optical path for the first virtual image V101 from the first display-light emitting unit <NUM> to the windshield WS is longer than that of the optical path for the second virtual image V102 from the second display-light generation unit <NUM> to the windshield WS. Therefore, the user U perceives that the distance from his/her viewpoint to the first virtual image V101 is longer than the distance from his/her viewpoint to the second virtual image V102. In other words, the user U perceives that the first virtual image V101 is located more distant from him/her than the second virtual image V102 is. That is, the head-up display apparatus <NUM> can project a plurality of virtual images of which depths perceived by the user U are different from each other.

Further, as described above, the head-up display apparatus <NUM> is configured so that the place where the first virtual image V101 is displayed can be adjusted. That is, the head-up display apparatus <NUM> is configured so that the reflected light L11 can be moved within the range of the second display-light generation unit <NUM>. Therefore, the head-up display apparatus <NUM> is configured so that the reflected light L11 becomes smaller than the second display-light generation unit <NUM> at the place where it passes through the second display-light generation unit <NUM>. Therefore, the angle of view of the first virtual image V101 is smaller than that of the second virtual image V102. Alternatively, it can be said that the first virtual image V101 is included (i.e., confined) in the range in which the second virtual image V102 can be displayed. Therefore, since the head-up display apparatus <NUM> can display the second virtual image V102 of which the angle of view is larger than that of the first virtual image V101, it realizes a head-up display apparatus of which the expandability is excellent. Note that, in the above-described configuration, it is possible to make the angle of view of the second virtual image V102 smaller than that of the first virtual image V101.

Further, the excitation-light emitting unit <NUM> can change the direction of the projection of the excitation light L20 according to the position of the concave mirror <NUM>. Therefore, in the head-up display apparatus <NUM>, when the place where the first virtual image V101 is displayed is adjusted by driving the concave mirror <NUM>, the place where the second virtual image V102 is displayed can be adjusted according to the place where the first virtual image V101 is displayed. In this case, for example, the control unit <NUM> detects the angle of the concave mirror <NUM>, and adjusts the timing at which the laser light source unit <NUM> emits light according to the detected angle of the concave mirror <NUM>. By adjusting the light emitting timing of the laser light source unit <NUM>, the excitation-light emitting unit <NUM> can adjust the direction of the image projected by the laser light emitting unit <NUM>.

Note that although the excitation-light emitting unit <NUM> is disposed near the concave mirror <NUM> and behind the concave mirror <NUM> (on the positive side in the X-axis direction) in the figure, the position of the excitation-light emitting unit <NUM> is not limited to the position shown in the figure as long as it does not interfere with either of the first display light L10 generated by the first projection apparatus and the reflected light L11 thereof. That is, the excitation-light emitting unit <NUM> of the second projection apparatus <NUM> may have any configuration as long as it projects excitation light to the second display-light generation unit <NUM> in an incident direction different from the incident direction in which the reflected light L11 is projected onto the second display-light generation unit <NUM>. Therefore, the degree of freedom in designing of the second projection apparatus <NUM> is high. That is, according to the first embodiment, it is possible to provide a head-up display apparatus of which the degree of freedom in spatial designing is high and the increase in volume is minimized.

Next, an example of a virtual image displayed by the head-up display apparatus <NUM> will be described with reference to <FIG> shows an example of a virtual image projected by the head-up display apparatus. The virtual image shown in the figure shows a virtual image perceived by the user U.

As shown in the figure, the user U perceives a first virtual image V101 and a second virtual image V102. In the example shown in the figure, in the first virtual image V101, a traveling speed (<NUM>/h) of the automobile <NUM> and guide information (i.e., an arrow indicating a right turn) for a traveling route are displayed. By displaying such information in the first virtual image V101, a user U can obtain information necessary for the driving as appropriate while minimizing the movement of the line of sight of the user U and the change of the focal distance of the eyes during the driving.

Meanwhile, in the second virtual image V102, an icon indicating that a pedestrian is approaching from the left side, and a message urging attention thereto are displayed. By displaying such information in the second virtual image V102, which the user U perceives as being located closer to him/her than the first virtual image V101 is, the head-up display apparatus <NUM> can make the user U have a sense of urgency. Further, by using the second virtual image V102 having an angle of view larger than that of the first virtual image V101, it is possible to effectively call attention to the user U without interfering with the display of normal information displayed during the traveling. Further, the brightness of the second display light L21 for displaying the second virtual image V102 can be changed by changing the intensity of the ultraviolet laser light. Therefore, the head-up display apparatus <NUM> can adjust the brightness of the second virtual image V102 by changing the intensity of the excitation light.

The first embodiment has been described above, but it should be noted that the head-up display apparatus <NUM> according to the first embodiment is not limited to the above-described configuration. For example, the laser light emitting unit <NUM>, which is one of the components of the excitation-light emitting unit <NUM>, may be configured so as to emit a surface emitting laser. Further, the laser scanning unit <NUM> may be a DLP (Digital Light Processing) unit.

Further, the self-luminous material 140A may be contained in a plurality of layers in the second display-light generation unit <NUM>. In this case, the self-luminous material(s) may be one(s) that emits fluorescence, which is visible light, by receiving excitation light having a different frequency in each of the layers.

As described above, the head-up display apparatus displays an image for forming a second virtual image on the second display-light generation unit, which is a clear cover, and thereby projects a plurality of virtual images of which depths are different from each other while minimizing the increase in volume thereof. Therefore, according to the first embodiment, it is possible to provide the head-up display apparatus of which the degree of freedom in designing is high and the expandability is excellent.

Next, a second embodiment will be described. A configuration for generating a second virtual image in a head-up display apparatus according to the second embodiment is different from that in the first embodiment. Differences from the first embodiment will be described hereinafter.

<FIG> is a schematic diagram showing a configuration of a head-up display apparatus according to the second embodiment. The head-up display apparatus <NUM> shown in the figure includes a second projection apparatus <NUM> in place of the second projection apparatus <NUM>.

The second projection apparatus <NUM> includes, in place of the laser projector apparatus for projecting ultraviolet laser light, a transmission-type display panel and a driver circuit for driving the display panel. The second projection apparatus <NUM> includes a second display-light generation unit <NUM> and a second display-light control unit <NUM>.

The second display-light generation unit <NUM> includes a transmission-type display panel <NUM> which uses a plate-like member having a high visible-light transmittance as a substrate. The transmission-type display panel <NUM> is composed of, for example, an organic EL (Electro Luminescence) display panel. That is, the second display-light generation unit <NUM> includes a layer that lets reflected light L11, which is visible light, pass therethrough and emits light by itself. Note that the display panel <NUM> may be a transmission-type liquid-crystal panel instead of the organic EL display panel.

The second display-light control unit <NUM> is connected to the second display-light generation unit <NUM>, and is a circuit including a driver IC for controlling the display panel <NUM> of the second display-light generation unit <NUM>. Note that the second display-light control unit <NUM> can be disposed at an arbitrary place as long as it does not interfere with either of the first display light L10 generated by the first projection apparatus and the reflected light L11 thereof.

As described above, the head-up display apparatus <NUM> according to the second embodiment displays an image for forming a second virtual image on the second display-light generation unit, which is a clear cover, and thereby projects a plurality of virtual images of which depths are different from each other while minimizing the increase in volume. Therefore, according to the second embodiment, it is possible to provide the head-up display apparatus of which the degree of freedom in designing is high and the expandability is excellent.

Note that the present invention is not limited to the above-described embodiements.

For example, the above-described head-up display apparatus can be applied to vehicles other than automobiles, such as aircrafts and ships. Further, the objects or the like to which the above-described head-up display apparatus is applied is not limited to vehicles. That is, the head-up display apparatus may be applied to driving simulators for automobiles, flight simulators for airplanes, video-game apparatuses, and the like.

Claim 1:
A head-up display apparatus (<NUM>) configured to project a plurality of virtual images of which depths perceived by a user with respect to a virtual-image display unit (WS) disposed in front of the user are different from each other, the head-up display apparatus (<NUM>) comprising:
a first projection apparatus (<NUM>) comprising a first display-light emitting unit (<NUM>) configured to emit first display light, and a concave mirror (<NUM>) configured to reflect the first display light and thereby emit reflected light thereof, the first projection apparatus (<NUM>) being configured to enable the user to perceive a first virtual image by projecting the reflected light onto a virtual-image display unit (WS); and
a second projection apparatus (<NUM>) comprising: a second display-light generation unit (<NUM>) configured to let the reflected light pass therethrough and generate second display light different from the first display light, and an excitation-light emitting unit (<NUM>) configured to project excitation light having a predetermined wavelength onto the second display-light generation unit (<NUM>,<NUM>), wherein:
the second projection apparatus is configured to enable the user to perceive a second virtual image by projecting the generated second display light onto the virtual-image display unit (WS),
the second virtual image has an angle of view larger than that of the first virtual image,
the second display-light generation unit (<NUM>) contains a self-luminous material, and is configured to generate the second display light as the self-luminous material emits light by receiving the excitation light, and
when the first projection apparatus (<NUM>) adjusts the place where the first virtual image is displayed, by driving the concave mirror, the second projection apparatus (<NUM>) adjusts the place where the second virtual image is displayed, by changing the direction of the projection of the excitation light, according to the place where the first virtual image is displayed.