Head-up display device

Abstract

The purpose of the present invention is to provide a head-up display device capable of suppressing a degradation in display quality.　A head-up display device (100b) according to the present invention comprises: a display device (10) that has a screen (11a) that emits display light (L); and a reflecting mirror (120) that has a reflective surface (120a) that reflects the display light (L) from the display device (10). The reflective surface (120a) is provided with a convex surface part (121) and a concave surface part (122) which are arranged side by side in the direction in which a central axis (120c) extends.

Description

Head-up display device

[0001] The present disclosure relates to a head-up display device.

[0002] The head-up display device described in Patent Document 1 includes a display that emits display light, a first mirror that is concave in the vertical direction and reflects the display light from the display, and a second mirror that reflects the display light from the first mirror toward the windshield, and the first mirror causes the display light to cross in the vertical direction before reaching the second mirror (see Figure 1 of Patent Document 1).

[0003] Patent No. 7484927

[0004] In the configuration described in Patent Document 1, the radiation surface of the display light of the display device and the reflection surface of the first mirror are opposed to each other in a non-parallel manner. Therefore, the difference in the optical path length of the display light between the radiation surface and the reflection surface becomes large at both ends in the direction perpendicular to the optical axis of the display light. This causes a large difference in magnification depending on the position of the display light, which may cause distortion in the virtual image when a viewer observes it with both eyes, resulting in a deterioration in the display quality of the virtual image.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a head-up display device that can suppress degradation of display quality.

[0006] In order to achieve the above object, the head-up display device according to the present disclosure comprises: a display unit having an emission surface that emits display light; and a mirror having a reflection surface that reflects the display light from the display unit, wherein the reflection surface comprises a convex portion and a concave portion that are aligned in a cross direction that intersects with the optical axis of the display light.

[0007] According to the present disclosure, it is possible to suppress degradation of display quality.

[0008] 1 is a schematic diagram of a vehicle equipped with a head-up display device according to a first embodiment of the present disclosure. FIG. 3 is a perspective view of the head-up display device according to the first embodiment of the present disclosure. FIG. 4 is a perspective view showing an internal configuration of the head-up display device according to the first embodiment of the present disclosure. FIG. 5 is a view from the direction of arrow IV in FIG. 3. FIG. 6 is a view from the direction of arrow V in FIG. 3. FIG. 7 is a diagram showing the positional relationship between a folding mirror and a concave mirror when viewed from below up according to a comparative example. FIG. 8 is a diagram showing the positional relationship between a folding mirror and a concave mirror when viewed from below up according to the first embodiment of the present disclosure. FIG. 9 is a diagram showing the positional relationship between the folding mirror and the concave mirror with respect to a windshield when viewed from above down according to the first embodiment of the present disclosure. FIG. 10 is a diagram showing the positional relationship between the folding mirror and the concave mirror with respect to a windshield when viewed from above down according to a modified example of the present disclosure. FIG. 11 is a schematic diagram of a head-up display device according to a second embodiment of the present disclosure and an optical path of display light. FIG. 12 is a schematic diagram of a concave mirror and an optical path of display light when viewed from the side according to the second embodiment of the present disclosure. FIG. 13 is a schematic diagram of a concave mirror, a windshield, and an optical path of display light when viewed from above down according to the second embodiment of the present disclosure. FIG. 10 is a diagram showing the positional relationship between the eye box and a virtual image when a concave mirror according to a comparative example is rotated. FIG. 11 is a schematic diagram of the concave mirror, windshield, and optical path of display light when looking down from above according to a comparative example. FIG. 11 is a diagram showing the positional relationship between the eye box and a virtual image when a concave mirror according to a comparative example is rotated. FIG. 12 is a diagram showing the positions of a virtual image and an image relative to the position of the eye box according to a second embodiment of the present disclosure. FIG. 13 is a diagram showing the center positions of partitioned areas into which an image displayed on a screen is divided when the eye box according to a second embodiment of the present disclosure is in a low position, a middle position, and a high position. FIG. 14 is a diagram showing the optical path length of display light between a display panel and a folding mirror according to a third embodiment of the present disclosure. FIG. 15 is a diagram showing the optical path length of display light between a display panel and a folding mirror according to a modified example.

[0009] First Embodiment A head-up display device according to a first embodiment of the present disclosure will be described with reference to the drawings. As shown in FIG. 1 , a head-up display device 100 is installed in an instrument panel of a vehicle 200. The head-up display device 100 emits display light L representing an image toward a windshield 201, which is an example of a projection target member of the vehicle 200. The display light L is reflected by the windshield 201 and reaches an eye box EB. When a viewer 1 (mainly the driver of the vehicle 200) has their viewpoint within the eye box EB, they can view a virtual image Vi superimposed on a real scene through the windshield 201.

[0010] In the following description, the upward direction Ud, downward direction Dd, forward direction Fd, backward direction Bd, left direction Ld, and right direction Rd are defined with respect to a viewer 1 of the vehicle 200. In addition, in this embodiment, the vehicle 200 is exemplified as a left-hand drive vehicle. However, the vehicle 200 may also be a right-hand drive vehicle. In the case of a right-hand drive vehicle, the head-up display device 100 is configured to be inverted in the left-right direction.

[0011] As shown in FIGS. 1 to 3, the head-up display device 100 includes a housing 60, a display device 10, a folding mirror 20, a concave mirror 30, and a control unit 50.

[0012] As shown in FIG. 2 , the housing 60 is hollow and made of a non-transparent resin material or a metal material. The folding mirror 20 and the concave mirror 30 are housed within the housing 60. The housing 60 has an opening 60a formed in a position facing the windshield 201. The housing 60 also has a curved, plate-like window portion 61 that closes the opening 60a. The window portion 61 is made of a translucent resin material such as acrylic, through which the display light L passes, and has a plate-like shape that is concavely curved in the front-to-rear directions Fd and Bd. The window portion 61 curves upward in the upward direction Ud as it travels rearward in the rearward direction Bd. The window portion 61 reflects sunlight that passes through the windshield 201 and enters it in the forward direction Fd. This allows the reflected sunlight to be absorbed by the dark-colored resin that constitutes the instrument panel, thereby suppressing the generation of stray light.

[0013] The display device 10 emits display light L under the control of a control unit 50. The display device 10 includes a TFT (Thin Film Transistor) liquid crystal display panel 11 (see FIG. 5 ) and a backlight (not shown) that illuminates the display panel 11. A screen 11a for displaying an image is formed on the light exit surface of the display panel 11. With an image showing vehicle information such as vehicle speed displayed on the screen 11a, illumination light from the backlight (not shown) is irradiated onto the display panel 11. As a result, display light L is emitted from the screen 11a. The display panel 11 is installed so that the display light L emitted from the screen 11a travels in a forward direction Fd and a downward direction Dd as it travels toward the outside of the vehicle compartment Od (leftward direction Ld in a left-hand drive vehicle).

[0014] 2 , the display device 10 is located rearward in the direction Bd from the upper end of the window 61 in the rear direction Bd, and is located downward in the direction Dd from this upper end. In other words, the display device 10 and the window 61 are arranged so as to overlap in the front-rear direction Fd, Bd. This prevents the display device 10 from protruding above the upper end of the window 61 in the rear direction Bd, thereby making it possible to reduce the size of the head-up display device 100. Note that, without being limited to this example, the display device 10 may be located directly below the upper end of the windshield 201 in the rear direction Bd.

[0015] The control unit 50 controls the display device 10. The control unit 50 includes a CPU (Central Processing Unit), a GDC (Graphic Display Controller), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The control unit 50 displays an image on the screen 11a and performs distortion correction (warping) on ​​the displayed image to correct distortion of the virtual image Vi.

[0016] 3 to 5, the folding mirror 20 is a correction mirror that reflects the display light L from the display device 10 toward the concave mirror 30. The reflective surface 20a of the folding mirror 20 is formed as a free-form surface. The folding mirror 20 is located further outward from the vehicle cabin Od (leftward in a left-hand drive vehicle, Ld) than the display panel 11, and in the forward direction Fd. The reflective surface 20a of the folding mirror 20 is oriented so that the reflected display light L travels in the forward direction Fd and downward direction Dd as it travels toward the vehicle cabin Id (rightward in a left-hand drive vehicle, Rd).

[0017] As shown in Figure 4, the folding mirror 20 is located in the rear direction Bd from the concave mirror 30, more specifically, between the concave mirror 30 and the screen 11a in the front-to-back directions Fd and Bd, and even more specifically, closer to the concave mirror 30 than the midpoint between the concave mirror 30 and the screen 11a.

[0018] 5, the center position 20b of the reflecting surface 20a is located in the downward direction Dd from the center position 11b of the screen 11a, and more specifically, is located between the center position 30b of the reflecting surface 30a of the concave mirror 30 and the center position 11b of the screen 11a in the vertical directions Ud, Dd. More specifically, the center position 20b is located closer to the center position 11b than the intermediate position between the center position 30b of the reflecting surface 30a and the center position 11b of the screen 11a in the vertical directions Ud, Dd. The position and orientation of the folding mirror 20 are adjusted to set the incident direction Li (see FIG. 4) of the display light L to the reflecting surface 30a, which will be described later.

[0019] The optical path of the display light L between the screen 11a, the folding mirror 20, and the concave mirror 30 forms a V-shape opening toward the vehicle interior Id when viewed from the downward direction Dd to the upward direction Ud, as shown in Fig. 4. Also, the optical path of the display light L between the screen 11a, the folding mirror 20, and the concave mirror 30 forms a V-shape opening toward the vehicle interior Id when viewed from the forward direction Fd to the backward direction Bd, as shown in Fig. 5.

[0020] The concave mirror 30 reflects the display light L reflected by the folding mirror 20 toward the windshield 201. The reflective surface 30a of the concave mirror 30 is formed as a concave curved surface in the longitudinal direction of the concave mirror 30. The concave mirror 30 is located closer to the interior of the vehicle Id than the folding mirror 20, in the forward direction Fd, and in the downward direction Dd. The reflective surface 30a of the concave mirror 30 is oriented so that the reflected display light L travels toward the exterior of the vehicle Od and in the backward direction Bd as it travels upward in the upward direction Ud.

[0021] As shown in FIG. 5 , the concave mirror 30 has a central axis 30c extending in the longitudinal direction of the concave mirror 30. The central axis 30c is located at the center of the concave mirror 30 in the lateral direction and passes through a central position 30b of the area where the display light L is reflected by the reflective surface 30a. The central axis 30c of the concave mirror 30 is inclined at an angle α with respect to the left-right directions Ld and Rd. The angle α is set to, for example, 30° to 60°, preferably 35° to 55°, and more preferably approximately 45° (including ±1°). When viewed from the forward direction Fd in the backward direction Bd, the positive direction of the angle α is clockwise. For example, when the angle α is 0 (zero) degrees, the reflective surface 30a faces the upward direction Ud.

[0022] 4 is a diagram showing an optical system including the display panel 11, the folding mirror 20, and the concave mirror 30, viewed from the downward direction Dd to the upward direction Ud. As shown in the figure, the incident direction Li of the display light L onto the reflecting surface 30a is set to a direction intersecting the front-rear directions Fd and Bd, which are reference directions. In other words, the angle θ of the incident direction Li of the display light L with respect to the front-rear directions Fd and Bd is set to a value other than 0 (zero)° and 180°. The angle θ is the angle of the incident direction Li with respect to the front-rear directions Fd and Bd in a horizontal plane (a plane along the front-rear directions Fd and Bd and the left-right directions Ld and Rd), and the incident direction Li is defined as the direction in which the optical axis of the display light L reaching the center position 30b of the reflecting surface 30a extends. When the angle θ is 0° (see Figure 6A for the comparative example), the incident direction Li extends in the front-to-rear directions Fd, Bd so as to move from the rear direction Bd to the front direction Fd, and when the angle θ is 180°, the incident direction Li extends in the front-to-rear directions Fd, Bd so as to move from the front direction Fd to the rear direction Bd.

[0023] The angle θ may be set to a value other than 0° and 180°, preferably 45° to 135°, 50° to 70°, 55° to 65°, or approximately 60° (including ±1°). The numerical range of the angle θ is not limited to these, and may be set to, for example, preferably 10° to 170°, 20° to 160°, 30° to 150°, or approximately 90° (including ±1°).

[0024] When the angle θ is 90°, the folding mirror 20 and the concave mirror 30 are aligned in the left-right directions Ld and Rd. As shown in the comparative example of Fig. 6A, when the angle θ is 0 (zero)°, the folding mirror 20 and the concave mirror 30 are aligned in the front-to-rear directions Fd and Bd. In other words, the smaller the absolute value of cos θ, the smaller the size of the head-up display device 100 in the front-to-rear directions Fd and Bd can be. When the angle θ is 90°, the size in the front-to-rear directions Fd and Bd is minimum.

[0025] For example, as shown in the comparative example of Fig. 6A, when the angle θ is 0 (zero)°, the folding mirror 20 and the concave mirror 30 are aligned in the front-to-rear directions Fd and Bd, and the size S1 in the front-to-rear directions Fd and Bd required for arranging the folding mirror 20 and the concave mirror 30 becomes large. On the other hand, when the angle θ is other than 0 (zero)°, for example, when the angle θ is 60°, as in the present embodiment, the size S2 in the front-to-rear directions Fd and Bd required for arranging the folding mirror 20 and the concave mirror 30 becomes smaller than the above-mentioned size S1, as shown in Fig. 6B. In this embodiment, the reflecting surfaces 20a and 30a are brought closer to each other in the front-to-rear directions Fd and Bd so that portions of the reflecting surfaces 20a and 30a overlap when viewed from the left-to-right directions Ld and Rd.

[0026] The folding mirror 20 and the concave mirror 30 are arranged along the windshield 201. For example, as shown in FIG. 7A , the display light L between the folding mirror 20 and the concave mirror 30 forms a three-dimensional optical shape Lf. The three-dimensional optical shape Lf is rectangular when cut in a direction perpendicular to the optical axis of the display light L. The three-dimensional optical shape Lf has a light contour line L1 extending along the corner of the rectangular cross section that is closest to the windshield 201. The light contour line L1 is parallel to a reference line L2 that passes through two points P1 and P2 separated in the left-right directions Ld and Rd on the windshield 201. Point P1 is located closest to one end of the light contour line L1 (the end on the folding mirror 20 side) on the windshield 201, and point P2 is located closest to the other end of the light contour line L1 (the end on the concave mirror 30 side) on the windshield 201. By positioning the folding mirror 20 and the concave mirror 30 so that the light contour line L1 is parallel to the reference line L2, it becomes easier to fit into the storage space within the instrument panel (not shown), and the head-up display device 100 can be made more compact.

[0027] 7A , the head-up display device 100 can be configured more compactly, even if the folding mirror 20 and the concave mirror 30 are arranged so that the optical axis center line L3 of the display light L is parallel to the reference line L2 instead of the above-mentioned light contour line L1, as shown in FIG. 7B . Furthermore, the folding mirror 20 and the concave mirror 30 do not have to be arranged along the windshield 201.

[0028] (Effects) According to the first embodiment described above, the following effects are achieved. (1-1) The head-up display device 100, which projects display light L onto the windshield 201, which is an example of a projection target member of the vehicle 200, includes a concave mirror 30, which is an example of a mirror having a reflective surface 30a that reflects the display light L toward the windshield 201. The incident direction Li of the display light L onto the reflective surface 30a is set at an angle θ intersecting the front-rear direction Fd, Bd of the vehicle 200 within a horizontal plane (a plane along the front-rear directions Fd, Bd and the left-right directions Ld, Rd). With this configuration, the distance in the front-rear directions Fd, Bd between the folding mirror 20 and the concave mirror 30 can be reduced. Therefore, the head-up display device 100 can be made smaller in the front-rear directions Fd, Bd of the vehicle 200.

[0029] (1-2) The incident direction Li is set to intersect with the front-rear direction Fd, Bd at an angle θ of 45° or more in the horizontal plane. With this configuration, the head-up display device 100 can be made smaller in the front-rear direction Fd, Bd of the vehicle 200.

[0030] (1-3) The incident direction Li is set to intersect with the front-rear directions Fd and Bd at an angle of 55° to 65° in the horizontal plane. With this configuration, the head-up display device 100 can be made smaller in the front-rear directions Fd and Bd of the vehicle 200.

[0031] (1-4) The head-up display device 100 includes, in addition to the concave mirror 30, a folding mirror 20 that reflects display light L toward the concave mirror 30, and a display device 10 that is located in the rearward direction Bd and upward direction Ud of the vehicle 200 relative to the concave mirror 30 and emits display light L toward the folding mirror 20. With this configuration, the distance in the front-to-rear directions Fd and Bd between the folding mirror 20 and the concave mirror 30 can be reduced, so even if the display device 10 is located in the rearward direction Bd and upward direction Ud relative to the concave mirror 30, the head-up display device 100 is unlikely to become large in the front-to-rear directions Fd and Bd. Furthermore, the optical path length of the display light L from the display device 10 via the folding mirror 20 to the concave mirror 30 can be lengthened, allowing the virtual image Vi to be displayed farther away from the viewer 1.

[0032] Second Embodiment A control device, a head-up display device, and a display control method according to a second embodiment of the present disclosure will be described with reference to the drawings. The following description will focus on differences from the first embodiment. As shown in FIG. 8 , the head-up display device 100a includes a mirror rotation drive unit 35 in addition to the configuration of the first embodiment. The mirror rotation drive unit 35 rotates the concave mirror 30 around the central axis 30c under the control of the control unit 50. When the concave mirror 30 rotates around the central axis 30c, the irradiation position of the display light L on the windshield 201, and thus the eye box EB, moves along the vertical directions Ud and Dd. Specifically, the eye box EB can be displaced in the vertical directions Ud and Dd between a high position H1, a middle position H2, and a low position H3. The height relationship between the positions is "H1 > H2 > H3." The middle position H2 is located midway between the high position H1 and the low position H3 in the vertical directions Ud and Dd.

[0033] For example, when the eyebox EB moves in either the upward direction Ud or the downward direction Dd, the virtual image Vi moves in the other direction Ud or the downward direction Dd. If the change in the positions of the eyebox EB and the virtual image Vi is likened to the rotation of a seesaw connecting the eyebox EB and the virtual image Vi with the straight lines I1, I2, and I3, the eyebox EB and the virtual image Vi rotate around the rotation center axis J. The rotation center axis J is an invisible axis that appears at the intersection of the straight lines I1, I2, and I3 connecting the corresponding centers of the virtual image Vi and the eyebox EB when the eyebox EB is in the high position H1, the middle position H2, or the low position H3.

[0034] In FIG. 8, the pivot axis J is illustrated as extending in the vehicle width direction (left-right directions Ld, Rd), but in reality, as shown in FIGS. 9 and 10A, it is inclined relative to the left-right directions Ld, Rd.

[0035] The orientation of the rotation center axis J is determined by the orientation of the central axis 30c of the concave mirror 30. This will be described in detail below, comparing this embodiment with a comparative example. In the comparative example shown in FIG. 11A , when looking down from the upward direction Ud to the downward direction Dd, the central axis 30c of the concave mirror 30 is positioned approximately parallel to the portion of the windshield 201 facing the concave mirror 30, so that the optical path length between the windshield 201 and the reflective surface 30a is uniform across the entire area. In this comparative example, the rotation center axis J is parallel to the central axis 30c of the concave mirror 30. Therefore, in this comparative example, as shown in FIG. 11B , when the eyebox EB moves in the vertical directions Ud and Dd between the high position H1, the middle position H2, and the low position H3, the virtual image Vi moves in the vertical directions Ud and Dd. At this time, the virtual image Vi does not shift in position in the horizontal direction Ld.

[0036] In this embodiment, as shown in FIG. 10A , when viewed from the upward direction Ud to the downward direction Dd, the central axis 30c of the concave mirror 30 is inclined relative to the portion of the windshield 201 facing the concave mirror 30. Specifically, the angle β of the central axis 30c of the concave mirror 30 relative to the left-right directions Ld and Rd in the horizontal plane is larger than the angle β in the comparative example shown in FIG. 11A , and is set to, for example, 30° to 50°. In this embodiment, the rotation central axis J is non-parallel to the central axis 30c of the concave mirror 30. Specifically, the distance between the rotation central axis J and the central axis 30c in the front-rear directions Fd and Bd decreases toward the interior side Id of the vehicle. Therefore, the rotation central axis J and the central axis 30c form a V-shape. This increases the difference in optical path lengths A1 and A2 of the display light L between the windshield 201 and both longitudinal ends of the reflecting surface 30a. 9, when viewed in the left-right directions Ld and Rd, the central axis 30c and the pivot axis J form a V-shape via the windshield 201. The distance between the pivot axis J and the central axis 30c in the front-rear directions Fd and Bd decreases as the distance increases in the upward direction Ud.

[0037] In the configuration according to this embodiment in which the central axis 30c and the rotation central axis J are non-parallel, without performing the misalignment correction described below, when the eye box EB moves in the up-down directions Ud and Dd between the high position H1, the middle position H2, and the low position H3, the virtual image Vi moves in a direction inclined relative to the up-down directions Ud and Dd, as shown in FIG. 10B according to the comparative example. Therefore, the display position of the virtual image Vi shifts laterally (left-right directions Ld and Rd). When the eye box EB is in the middle position H2, the virtual image V1 shifts leftward by a shift amount ΔY1 when the eye box EB is in the high position H1, and the virtual image V3 shifts rightward by a shift amount ΔY2 when the eye box EB is in the low position H3.

[0038] As shown in FIG. 12, the control unit 50 performs deviation correction to change the display position of the image G in the screen 11a in the left - right directions Ld and Rd according to the position of the eye box EB so as to reduce the deviation in the left - right directions Ld and Rd of the virtual image Vi. In this deviation correction, as the position of the eye box EB is moved upward in the upward direction Ud, the control unit 50 shifts the display position of the image G in the screen 11a in the right direction Rd so as to cancel out the positional deviation of the virtual image Vi in the left direction Ld. Hereinafter, the directions of the screen 11a and the image G are defined as the left - right and up - down directions corresponding to the left - right and up - down directions with respect to the virtual image Vi, and are independent of the actual directions of the screen 11a and the image G.

[0039] In this deviation correction, as shown in the middle row of FIG. 12, with the position of the image G2 in the screen 11a when the eye box EB is at the middle position H2 as a reference, as shown in the upper row of FIG. 12, when the eye box EB is at the low position H3, the image G3 in the screen 11a is displayed at a position shifted leftward in the left direction Ld by a shift correction amount ΔW1 from the reference image G2. The shift correction amount ΔW1 is set to an amount that cancels out the deviation amount ΔY2 of the virtual image Vi in the right direction Rd. Thereby, the horizontal deviation between the virtual images V2 and V3 shown in FIG. 10B can be eliminated. Also, in this deviation correction, as shown in the lower row of FIG. 12, when the eye box EB is at the high position H1, the image G1 in the screen 11a is displayed at a position shifted rightward in the left direction Ld by a shift correction amount ΔW2 from the reference image G2. The shift correction amount ΔW2 is set to an amount that cancels out the deviation amount ΔY1 of the virtual image Vi in the left direction Ld. Thereby, the horizontal deviation between the virtual images V1 and V2 shown in FIG. 10B can be eliminated. In this example, the shift correction amount ΔW1 from the middle position H2 to the low position H3 is smaller than the shift correction amount ΔW2 from the middle position H2 to the high position H1. Note that in this example, the shift correction amount ΔW1 is set to be smaller than the shift correction amount ΔW2, but it is not limited to this, and it may be set to be larger than the shift correction amount ΔW2 or the same amount as the shift correction amount ΔW2.

[0040] As described above, the control unit 50 performs distortion correction (warping) on ​​the image G to be displayed, correcting the distortion of the virtual image Vi. FIG. 13 shows the center positions Pn, Pt, and Ps of each divided area when the distortion-corrected image displayed on the screen 11a is divided into multiple divided areas in the up-down directions Ud and Dd and the left-right directions Ld and Rd. In this example, each center position Pn is the center position of each divided area of ​​the image G2 on the screen 11a when the eye box EB is at the middle position H2. Each center position Pt is the center position of each divided area of ​​the image G1 on the screen 11a when the eye box EB is at the high position H1. Each center position Ps is the center position of each divided area of ​​the image G3 on the screen 11a when the eye box EB is at the low position H3. As a result of the above-described misalignment correction, in each divided area, the center position Ps is located to the left of the center position Pn in the Ld direction, and the center position Pt is located to the right of the center position Pn in the Rd direction. The shift correction amounts ΔW1 and ΔW2 described above are expressed as the distances in the left-right directions Ld and Rd between the center positions Pn, Pt, and Ps in each divided area, and the distances between the center positions Pn, Pt, and Ps are different for each divided area. For example, the distance between the center positions Pn, Pt, and Ps decreases as one moves from the right direction Rd to the left direction Ld in all divided areas. Furthermore, the distance between the center positions Pn, Pt, and Ps decreases as one moves from the upward direction Ud to the downward direction Dd in all divided areas. In particular, the distance between the center positions Pn, Pt, and Ps in the upper right divided area is the longest, and the distance between the center positions Pn, Pt, and Ps decreases as one moves away from this upper right divided area. Furthermore, the distance between the center positions Pn and Ps is set to be smaller than the distance between the center positions Pn and Pt.

[0041] In this embodiment, the vehicle is described as a left-hand drive vehicle, but it may also be a right-hand drive vehicle. In the case of a right-hand drive vehicle, the left and right in this embodiment are reversed. Furthermore, in this embodiment, a shift correction amount ΔW2 corresponding to the high position H1 of the eye box EB and a shift correction amount ΔW1 corresponding to the low position H3 of the eye box EB are set, but the number of set shift correction amounts may be three or more. For example, the shift correction amount corresponding to each position of the eye box EB may be obtained from a data table or by calculation.

[0042] (Effects) According to the second embodiment described above, the following effects are achieved. (2-1) The head-up display device 100a includes a concave mirror 30 having a reflective surface 30a that reflects display light L toward a windshield 201 to display a virtual image Vi, which is an example of a projected image, and that is tilted with respect to the windshield 201 so that there is a difference in optical path lengths A1, A2 from both longitudinal ends of the reflective surface 30a, and a mirror rotation drive unit 35 that rotates the concave mirror 30 about a central axis 30c, which is an example of a rotation axis, extending in the longitudinal direction. The control unit 50, which is an example of a control device for the head-up display device 100a, displays an image G emitting display light L on the screen 11a and performs misalignment correction by shifting the display position of the image G on the screen 11a in the left-right directions Ld, Rd in the direction opposite to the direction of the positional misalignment so as to suppress positional misalignment of the virtual image Vi in the left-right directions Ld, Rd that occurs due to rotation of the concave mirror 30. This configuration prevents the virtual image Vi from shifting in position in the left-right directions Ld and Rd when the concave mirror 30 rotates, thereby preventing a decrease in the display quality of the virtual image Vi.

[0043] (2-2) The control unit 50 rotates the concave mirror 30 about the central axis 30c to move the position of the eye box EB, which is the area in which the virtual image Vi is visible, between a high position H1, a low position H3 located below the high position H1, and a middle position H2 located halfway between the high position H1 and the low position H3, and performs a shift correction so that the shift correction amount ΔW1 of the display position of the image G when moved from the middle position H2 to the low position H3 is smaller than the shift correction amount ΔW2 of the display position of the image G when moved from the high position H1 to the middle position H2. With this configuration, the shift correction amounts ΔW1 and ΔW2 are set according to the shape of the windshield 201, further suppressing positional shifts of the virtual image Vi in the left-right directions Ld and Rd when the concave mirror 30 rotates.

[0044] (2-3) The control unit 50 divides the image G displayed on the screen 11a into a plurality of divided regions, sets shift correction amounts ΔW1 and ΔW2 for each divided region, and performs deviation correction so that the shift correction amounts ΔW1 and ΔW2 are large on the side (right side of FIG. 13 ) of the plurality of divided regions that corresponds to the side (right side of FIG. 10A ) where the optical path lengths A1 and A2 of the display light L between the reflective surface 30a and the windshield 201 are small. With this configuration, the shift correction amounts ΔW1 and ΔW2 are set according to the orientation of the concave mirror 30 with respect to the windshield 201, which further suppresses positional deviation of the virtual image Vi in the left-right directions Ld and Rd when the concave mirror 30 rotates.

[0045] (2-4) The head-up display device 100 includes a control unit 50, a display device 10 having a screen 11a, a concave mirror 30, and a mirror rotation drive unit 35. This configuration prevents the virtual image Vi from shifting in position in the left-right directions Ld and Rd when the concave mirror 30 rotates. This prevents a decrease in the display quality of the virtual image Vi.

[0046] Third Embodiment A head-up display device according to a third embodiment of the present disclosure will be described with reference to the drawings. This embodiment differs from the first and second embodiments in that a convex portion and a concave portion are arranged on the reflective surface of the folding mirror. The following description will focus on the differences from the first and second embodiments.

[0047] As shown in FIG. 14 , the folding mirror 120 is tilted non-parallel to the display panel 11. Specifically, a central axis 120c extending in the longitudinal direction of the reflective surface 120a of the folding mirror 120 is tilted non-parallel to the display panel 11. More specifically, the folding mirror 120 is disposed so that the inter-surface distance between the reflective surface 120a of the folding mirror 120 and the screen 11a of the display panel 11 decreases in the upward direction Ud relative to the display panel 11. The optical path length La of the display light L between the reflective surface 120a and the screen 11a is determined according to this inter-surface distance. The optical path length La becomes the minimum optical path length LS at the position where this inter-surface distance is minimum, and becomes the maximum optical path length LT at the position where this inter-surface distance is maximum. The minimum optical path length LS is located above the reflective surface 120a and the screen 11a, respectively, and the maximum optical path length LT is located below the reflective surface 120a and the screen 11a, respectively.

[0048] The reflective surface 120a includes a convex surface portion 121 and a concave surface portion 122 that are aligned in the direction in which the central axis 120c extends. The convex surface portion 121 is curved convexly so as to bulge toward the display panel 11. The concave surface portion 122 is curved concavely so as to be recessed toward the display panel 11. The convex surface portion 121 and the concave surface portion 122 give the reflective surface 120a one period of a sine wave in the direction in which the central axis 120c extends. The boundary between the convex surface portion 121 and the concave surface portion 122 is located at the center of the reflective surface 120a in the direction in which the central axis 120c extends. The convex surface portion 121 and the concave surface portion 122 extend linearly in the short-side direction of the reflective surface 120a.

[0049] The concave surface 122 of the reflecting surface 120a is located on the minimum optical path length LS side, and the convex surface 121 of the reflecting surface 120a is located on the maximum optical path length LT side, thereby making it possible to reduce the optical path length difference, which is the difference between the maximum optical path length LT and the minimum optical path length LS.

[0050] Specifically, in the comparative example of Fig. 15, the folding mirror 220 includes a reflective surface 220a having a series of concave shapes extending in the direction of the central axis 220c. In this comparative example, similar to the configuration of this embodiment (the configuration of Fig. 14), the central axis 220c extending in the longitudinal direction of the reflective surface 220a is tilted non-parallel to the display panel 11. In this comparative example, the optical path length difference, which is the difference between the maximum optical path length LT and the minimum optical path length LS, is large. In contrast, in this embodiment, the concave surface portion 122 increases the minimum optical path length LS, and the convex surface portion 121 reduces the maximum optical path length LT, thereby reducing the optical path length difference.

[0051] In this example, the convex surface portion 121 and the concave surface portion 122 are arranged to be aligned in the direction in which the central axis 120c extends. However, this is not limited thereto, and they may be arranged to be aligned in the short direction of the reflecting surface 120a. Furthermore, the convex surface portion 121 and the concave surface portion 122 may be arranged to be aligned in a direction inclined with respect to the direction in which the central axis 120c extends. Furthermore, the boundary between the convex surface portion 121 and the concave surface portion 122 may be located at a position other than the center position in the direction in which the central axis 120c extends of the reflecting surface 120a. The shapes of the convex surface portion 121 and the concave surface portion 122 can be changed as appropriate. Furthermore, the reflecting surface 120a is composed of the convex surface portion 121 and the concave surface portion 122. However, multiple convex surface portions 121 may be positioned on either side of the concave surface portion 122, or multiple concave surface portions 122 may be positioned on either side of the convex surface portion 121. For example, the reflective surface 120a may be arranged such that the convex surface portions 121 and the concave surface portions 122 are alternately repeated multiple times. In addition, in this example, the reflective surface 120a and the screen 11a extend along the up-down directions Ud and Dd, but this is not limitative and they may extend in any direction, for example, along the left-right directions Ld and Rd.

[0052] (Effects) The third embodiment described above provides the following effects. (3-1) The head-up display device 100b includes a display device 10, which is an example of a display unit, having a screen 11a, which is an example of an emission surface, that emits display light L, and a folding mirror 120, which is an example of a mirror having a reflection surface 120a that reflects the display light L from the display device 10. The reflection surface 120a includes a convex surface 121 and a concave surface 122 that are aligned in a cross direction (the direction in which the central axis 120c extends) that intersects with the optical axis of the display light L. With this configuration, the convex surface 121 and the concave surface 122 can adjust the difference in optical path length of the display light L between the screen 11a and the reflection surface 120a to be small. This can suppress distortion of the virtual image Vi (projected image) when a viewer observes the virtual image Vi with both eyes, thereby suppressing a decrease in the display quality of the virtual image Vi.

[0053] (3-2) The folding mirror 120 is arranged at an angle non-parallel to the screen 11a so that the inter-surface distance between the screen 11a and the reflective surface 120a changes in the direction of extension of the central axis 120c. The convex surface portion 121 is located on the side of the reflective surface 120a where the inter-surface distance (i.e., the optical path length La) is large (the maximum optical path length LT side). The concave surface portion 122 is located on the side of the reflective surface 120a where the inter-surface distance (i.e., the optical path length La) is small (the minimum optical path length LS side). With this configuration, the convex surface portion 121 and the concave surface portion 122 can adjust the optical path length difference of the display light L between the screen 11a and the reflective surface 120a to be small. This can suppress a decrease in the display quality of the virtual image Vi.

[0054] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) may be made as appropriate within the scope of the present disclosure. An example of such a modification is described below.

[0055] (Modifications) In each of the above embodiments, the folding mirror 20 may be omitted. In this case, the display panel 11 may be located at the position of the folding mirror 20. In this configuration, the head-up display device 100 can be made even more compact. Furthermore, in this configuration, the head-up display device 100 can be made the most compact by particularly positioning the display panel 11 laterally (to the left direction Ld or the right direction Rd) of the folding mirror 20. In each of the above embodiments, the concave mirror 30 may be a mirror other than a concave mirror, for example, a flat mirror.

[0056] In the above embodiments, the projection target member is the windshield 201, but it may also be a dedicated combiner. The head-up display devices 100, 100a, and 100b are not limited to vehicles, and may be mounted on other vehicles such as airplanes and ships. In the above embodiments, the relative height positions of the display panel 11, the folding mirror 20, and the concave mirror 30 in the up-down direction Ud and Dd can be changed as appropriate. For example, the display panel 11 may be at the same height as the concave mirror 30, or may be located lower in the direction Dd than the concave mirror 30.

[0057] In each of the above embodiments, the display device 10 is a type including a liquid crystal display panel 11, but is not limited to this and may be any type as long as it is capable of emitting display light L. The display device 10 may be, for example, a type including an OLED (Organic Light-Emitting Diode), a type that receives light reflected by a DMD (Digital Micromirror Device) and displays an image on a transmissive screen, or the like.

[0058] 1...Viewer 10...Display device, 11...Display panel, 11a...Screen, 11b...Center position 20, 120, 220...Folding mirror, 20a, 120a, 220a...Reflecting surface, 20b...Center position, 120c, 220c...Center axis, 121...Convex portion, 122...Concave portion 30...Concave mirror, 30a...Reflecting surface, 30b...Center position, 30c...Center axis, 35...Mirror rotation drive unit 50...Control unit 60...Housing, 60a...Opening, 61...Window portion 100, 100a, 100b...Head-up display device 200...Vehicle, 201...Windshield α, θ, β...angle, A1, A2, La...optical path length, G, G1-G3...image, H1...high position, H2...medium position, H3...low position, I1-I3...straight line, J...rotation center axis, L...display light, L1...light contour line, L2...reference line, L3...optical axis center line, EB...eye box, S1, S2...size, Vi, V1-V3...virtual image, ΔW1, ΔW2...shift correction amount, ΔY1, ΔY2...displacement amount, Fd...forward direction, Bd...rearward direction, Ud...upward direction, Dd...downward direction, Ld...leftward direction, Rd...rightward direction, Id...vehicle interior, Od...vehicle exterior, LT...maximum optical path length, LS...minimum optical path length, Lf...light three-dimensional shape, Li...incident direction, Pn, Ps, Pt...center position

Claims

1. A head-up display device comprising: a display unit having an emission surface that emits display light; and a mirror having a reflective surface that reflects the display light from the display unit, wherein the reflective surface has a convex portion and a concave portion aligned in a direction intersecting the optical axis of the display light.

2. A head-up display device according to claim 1, wherein the mirror is arranged at an angle non-parallel to the radiation surface so that the inter-surface distance between the radiation surface and the reflection surface varies in the intersecting direction, the convex surface portion is located on the side of the reflection surface where the inter-surface distance is larger, and the concave surface portion is located on the side of the reflection surface where the inter-surface distance is smaller.

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