JP7732301B2 - Head-up display device - Google Patents

Description

This disclosure relates to a head-up display device.

For example, the head-up display device described in Patent Document 1 includes a display that emits display light, a first mirror that reflects the display light emitted by the display, and a second mirror that reflects the display light reflected by the first mirror. The first mirror causes the reflected display light to cross up and down at a crossing point before reaching the second mirror.

International Publication No. 2018/198821

In the configuration described in Patent Document 1, various components such as the first mirror and second mirror had to be positioned so as not to obstruct the optical path of the display light, resulting in a large head-up display device.

This disclosure was made in consideration of the above-mentioned circumstances, and aims to provide a head-up display device that can be made smaller.

To achieve the above-mentioned objective, the head-up display device disclosed herein projects display light onto a projection target member, thereby enabling a viewer whose viewpoint is within a visible area to view a virtual image. The head-up display device includes a display unit that emits the display light, a first mirror having a reflective surface that reflects the display light emitted from the display unit, and a second mirror that reflects the display light reflected by the first mirror toward the projection target member. The display light intersects at a first cross point and a second cross point in a specific direction, and at least a portion of the reflective surface of the first mirror is included within a virtual circle whose diameter is a line segment connecting the first cross point and the second cross point. The first cross point is a point at which the display light intersects, corresponding to a viewpoint at a first end of the visible area in the specific direction, and the second cross point is a point at which the display light intersects, corresponding to a viewpoint at a second end of the visible area opposite the first end in the specific direction.

This disclosure enables head-up display devices to be made smaller.

1 is a schematic diagram of a vehicle according to an embodiment of the present disclosure. 1 is a schematic diagram of a head-up display device according to an embodiment of the present disclosure. 1 is a schematic diagram of a head-up display device when the viewpoint is located at the center of the visible area according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram of a head-up display device when the viewpoint is located at the top end of the visible area according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram of a head-up display device when a viewpoint is located at the bottom end of a visible area according to an embodiment of the present disclosure. FIG. FIG. 2 is a schematic diagram illustrating an optical path of display light as viewed from the width direction according to an embodiment of the present disclosure. FIG. 10 is a schematic diagram showing the optical path of display light as viewed from the width direction according to a comparative example. FIG. 10 is a schematic diagram showing an optical path of display light as viewed from the width direction according to a modification of the present disclosure.

An embodiment of a head-up display device according to the present disclosure will be described with reference to the drawings.
1 , the head-up display device 100 is mounted on the dashboard of a vehicle 200. The head-up display device 100 projects display light L onto a windshield 201, which is a projection target, to display a virtual image V including vehicle information within a virtual image display area K so that the virtual image V can be viewed by a viewer 1 (e.g., the driver of the vehicle 200). When viewpoints EP1, EP2, and EP3 of the viewer 1 are within a visible region R, the viewer 1 can view the virtual image V.

As shown in FIG. 2 , the head-up display device 100 includes a first mirror 11 , a second mirror 12 , a display unit 20 , and a case 30 .
The case 30 is formed in a box shape from a light-blocking resin or metal. The first mirror 11, the second mirror 12, and the display unit 20 are housed inside the case 30. The case 30 has a window 31 made of a light-transmitting member that transmits display light L generated in the internal space of the case 30 toward the windshield 201.

The display unit 20 has a light emitting surface 21 that emits display light L that represents an image. The display unit 20 may be a type that includes a liquid crystal panel and a lighting device, or a type that includes a reflective display element such as a DMD (Digital Micro Mirror Device) element and a projector. In this example, the display unit 20 emits the display light L as diffused light. The light emitting surface 21 faces toward the rear and upper side of the vehicle. The image displayed on the light emitting surface 21 has been subjected to distortion correction that corrects distortion of the virtual image V viewed by the viewer 1.

As shown in FIG. 2, the first mirror 11 is a curved mirror that is concavely curved along the vehicle's height direction and extends linearly along the vehicle's width direction. The first mirror 11 may be concavely curved or convexly curved in the vehicle's width direction. The first mirror 11 reflects the display light L emitted from the display unit 20 toward the second mirror 12. The concavely curved reflective surface 11a of the first mirror 11 faces downward and forward of the vehicle.

As shown in FIGS. 3, 4, and 5, the first mirror 11 reflects the display light L from the display unit 20 (see FIG. 2) toward the second mirror 12 so that the display light L intersects with the display light L at cross points CP1, CP2, and CP3 in the height direction of the vehicle 200. The cross points CP1, CP2, and CP3 are located between the first mirror 11 and the second mirror 12 in the optical path of the display light L. The display light L converges from the first mirror 11 to the cross points CP1, CP2, and CP3 and diverges from the cross points CP1, CP2, and CP3 toward the second mirror 12. Note that although a portion of the display light L intersects with the cross points CP1, CP2, and CP3, the positions at which the display light L is focused do not necessarily coincide with the positions of the cross points. In the head-up display device 100 of the present disclosure, the display light L is focused at a position different from the cross points between the first mirror 11 and the second mirror 12 in the height direction.
The method for setting the positions of the crossing points CP1, CP2, and CP3 will be described in detail later.

As shown in FIG. 2, the second mirror 12 is a concave mirror that curves along the height and width directions of the vehicle. The second mirror 12 reflects the display light L reflected from the first mirror 11 toward the windshield 201. The second mirror 12 reflects the display light L from the first mirror 11 toward the windshield 201 so as to magnify it. The concavely curved reflective surface 12a of the second mirror 12 faces toward the rear and upper side of the vehicle. The second mirror 12 works in cooperation with the first mirror 11 to suppress distortion of the virtual image caused by reflection on the windshield 201.

Next, a method for setting the positions of the cross points CP1, CP2, and CP3 will be described with reference to FIGS.
The positions of the cross points CP1, CP2, and CP3 on the optical path of the display light L are adjusted depending on the radius of curvature of the reflecting surface 11a of the first mirror 11, the diffusion angle of the display light L emitted by the display unit 20, and the like. For example, the larger the radius of curvature of the reflecting surface 11a of the first mirror 11, the closer the positions of the cross points CP1, CP2, and CP3 are to the reflecting surface 11a. Furthermore, the larger the diffusion angle of the display light L emitted by the display unit 20, the closer the positions of the cross points CP1, CP2, and CP3 are to the reflecting surface 11a. The cross points CP1, CP2, and CP3 are provided closer to the first mirror 11 than the midpoint between the first mirror 11 and the second mirror 12.

The crossing points CP1, CP2, and CP3 will be specifically described.
4 , the cross point CP2 is a position where, as viewed in the width direction, light rays L2T and L2B of the display light L corresponding to a viewpoint EP2 located at the upper end of the visible region R in the height direction intersect. The light ray L2T is a light ray corresponding to the upper end of the virtual image display area K, and the light ray L2B is a light ray corresponding to the lower end of the virtual image display area K.
5 , the cross point CP3 is a position where, as viewed in the width direction, light rays L3T and L3B of the display light L corresponding to a viewpoint EP3 located at the lower end of the visible region R in the height direction intersect. The light ray L3T is a light ray corresponding to the upper end of the virtual image display area K, and the light ray L3B is a light ray corresponding to the lower end of the virtual image display area K.
3 , the cross point CP1 is a position where light rays L1T and L1B of the display light L corresponding to a viewpoint EP1 located at the center of the visible region R in the height direction intersect when viewed from the width direction. The light ray L1T is a light ray corresponding to the upper end of the virtual image display area K, and the light ray L1B is a light ray corresponding to the lower end of the virtual image display area K.
Each of the viewpoints EP1, EP2, and EP3 is located at the center of the visible region R in the width direction of the vehicle.

The two light rays L1T, L1B, L2T, L2B, L3T, and L3B that make up each cross point CP1, CP2, and CP3 intersect when viewed two-dimensionally from the width direction. However, in reality, light rays L1T, L1B, L2T, L2B, L3T, and L3B extend in three-dimensional space and do not necessarily intersect at cross points CP1, CP2, and CP3. Therefore, in this example, cross points CP1, CP2, and CP3 are defined as the intersections of light rays L1T, L1B, L2T, L2B, L3T, and L3B projected onto plane PL, on which both line segments of light rays L2T and L3B lie.

As shown in Figure 6, cross points CP1, CP2, and CP3 are set at positions where a portion of the reflecting surface 11a of the first mirror 11 is included within an imaginary circle C, where the line segment connecting the two cross points CP2 and CP3 has a diameter D. Cross point CP1 is located at the center of the imaginary circle C. The imaginary circle C is determined by experiment or simulation.

In the comparative example of Figure 7, the cross points CP1, CP2, and CP3 are set at positions where the reflective surface 11a of the first mirror 11 is not included within the imaginary circle C. In this comparative example, the cross points CP1, CP2, and CP3 are farther from the reflective surface 11a than in the present embodiment of Figure 6. In terms of optical path design, the reflective surface 11a must be formed at a position that traces the display light L's traveling direction from the cross points CP2 and CP3 toward the reflective surface 11a in the opposite direction. Therefore, in this comparative example, the size of the reflective surface 11a must be increased. This reduces the gap S2 between the upper end of the reflective surface 11a of the first mirror 11 and the display light L, particularly the light ray L2T, reflected by the second mirror 12. Therefore, in this comparative example, the size of the reflective surface 11a must be increased, which may cause various components, such as a mirror holder (not shown) that holds the first mirror 11, to interfere with the optical path of the display light L.

On the other hand, in the present embodiment shown in Fig. 6, the cross points CP1, CP2, and CP3 are closer to the reflecting surface 11a than in the comparative example shown in Fig. 7. As a result, as shown in Fig. 6, the display light L, particularly the light ray L2T, does not reach the eliminable region 11b of the reflecting surface 11a, and the display light L, particularly the light ray L3B, does not reach the eliminable region 11c of the reflecting surface 11a. Therefore, the eliminable regions 11b and 11c can be omitted on the reflecting surface 11a, and the size of the reflecting surface 11a can be reduced.
Furthermore, the gap S1 between the upper end of the reflecting surface 11a of the first mirror 11 and the display light L, particularly the light ray L2T, reflected by the second mirror 12 is increased. This prevents various members, such as a mirror holder (not shown) that holds the first mirror 11, from interfering with the optical path of the display light L.

(effect)
According to the embodiment described above, the following effects are achieved.
(1) The head-up display device 100 projects display light L onto a windshield 201, which is an example of a projection target member, thereby enabling a viewer 1, whose viewpoints EP1, EP2, and EP3 are within a visible region R, to view a virtual image V. The head-up display device 100 includes a display unit 20 that emits the display light L, a first mirror 11 having a reflective surface 11a that reflects the display light L emitted from the display unit 20, and a second mirror 12 that reflects the display light L reflected by the first mirror 11 toward the windshield 201. The display light L intersects with a cross point CP2, which is an example of a first cross point, and a cross point CP3, which is an example of a second cross point, in a height direction, which is an example of a specific direction. A portion of the reflective surface 11a of the first mirror 11 is included in a virtual circle C, the diameter of which is D, of which is a line segment connecting the cross points CP2 and CP3. The cross point CP2 is a point where the display light L intersects with the viewpoint EP2 at the first end (upper end) of the visible region R in the height direction. The cross point CP3 is a point where the display light L intersects with the viewpoint EP3 at the second end (lower end) of the visible region R in the height direction.
According to this configuration, a portion of the reflective surface 11a of the first mirror 11 is included in the virtual circle C, so the cross points CP2 and CP3 are set near the reflective surface 11a of the first mirror 11. Therefore, for the reasons described above, the size of the reflective surface 11a can be reduced, thereby enabling the head-up display device 100 to be made more compact.
Furthermore, it is possible to prevent various members such as a mirror holder (not shown) that holds the first mirror 11 from interfering with the optical path of the display light L. This increases the degree of freedom in designing the head-up display device 100.

(2) The crossing points CP2 and CP3 are located between the first mirror 11 and the second mirror 12 in the optical path of the display light L.
According to this configuration, the head-up display device 100 can be made smaller.

Note that this disclosure is not limited to the above-described embodiments and drawings. Modifications (including the deletion of components) may be made as appropriate within the scope of the gist of this disclosure. An example of a modification is described below.

(Modification)
In the above embodiment, the cross points CP1, CP2, and CP3 are set between the first mirror 11 and the second mirror 12 in the optical path of the display light L, but this is not limiting and they may be set between the reflecting surface 11a and the light emitting surface 21 as shown in Fig. 8. In this case, the light emitting surface 21 emits the display light L that converges so as to intersect at the cross points CP1, CP2, and CP3 before reaching the reflecting surface 11a. Even in this case, a part of the reflecting surface 11a of the first mirror 11 is included in an imaginary circle C having a diameter D and formed by a line segment connecting the two cross points CP2 and CP3. This provides the same effects as those of the above embodiment.

In the above embodiment, the display light L intersects in the height direction of the vehicle 200. However, instead of or in addition to this, it may intersect in the width direction of the vehicle 200. In this case, the reflective surface 11a of the first mirror 11 is formed in a concave shape that is curved along the width direction of the vehicle 200. In this modified example, using a method similar to that of the above embodiment, at least a portion of the reflective surface 11a is set to be included within a virtual circle identified by the crossing point in the width direction.

In the above embodiment, a portion of the reflective surface 11a of the first mirror 11 is included within the imaginary circle C when viewed from the width direction, but this is not limited to this, and the entire reflective surface 11a may be included within the imaginary circle C.
Furthermore, in the above embodiment, the positions of the cross points CP1, CP2, and CP3 were set so that a portion of the reflective surface 11a of the first mirror 11 was included within the virtual circle C. From a similar perspective, the positions of the cross points CP1, CP2, and CP3 may also be set so that a portion of the reflective surface 11a of the first mirror 11 is included within a virtual sphere that includes the virtual circle C.

In the above embodiment, the second mirror 12 may be configured to be rotatable by a mirror driver around a rotation axis along the width direction of the vehicle. By rotating the second mirror 12 around the rotation axis, it is possible to adjust the irradiation position of the display light L onto the viewer 1 in the vertical direction. In this case, for example, the cross points CP1, CP2, CP3 and the imaginary circle C are identified at the rotation angle of the second mirror 12 at which the irradiation position of the display light L is at the center position in the vertical direction.

In the above embodiment, the head-up display device 100 is mounted on a vehicle, but this is not limited to this and it may also be mounted on vehicles such as airplanes and ships. Furthermore, the projection target member is not limited to the windshield 201 and may be a dedicated combiner.

1 Viewer 11 First mirror 11a, 12a Reflecting surface 11b, 11c Omittable area 12 Second mirror 20 Display unit 21 Light emitting surface 30 Case 100 Head-up display device 200 Vehicle 201 Windshield C Virtual circle D Diameter K Virtual image display area L Display light R Visible area S1, S2 Gap V Virtual images L1B, L2B, L3B, L1T, L2T, L3T Light rays CP1, CP2, CP3 Cross points EP1, EP2, EP3 Viewpoint PL Plane

Claims (3)

A head-up display device that projects display light onto a projection member to allow a viewer whose viewpoint is within a visible area to view a virtual image,
a display unit that emits the display light;
a first mirror having a reflective surface that reflects the display light emitted from the display unit;
a second mirror that reflects the display light reflected by the first mirror toward the projection member,
the display light intersects at a first cross point and a second cross point in a specific direction;
at least a part of the reflecting surface of the first mirror is included within a virtual circle having a diameter equal to a line segment connecting the first cross point and the second cross point,
the first crossing point is a point at which the display light intersects, the point corresponding to a viewpoint at a first end of the visible area in the specific direction;
the second crossing point is a point at which the display light intersects with the viewpoint at a second end of the visible area in the specific direction, the second crossing point being opposite to the first end of the visible area;
Head-up display device. the first cross point and the second cross point are located between the first mirror and the second mirror in the optical path of the display light;
The head-up display device according to claim 1 . the first cross point and the second cross point are located between the display unit and the first mirror in the optical path of the display light;
The head-up display device according to claim 1 .