Image projection device

Abstract

To provide an image projection device that enables miniaturization and cost reduction. [Solution] The head-up display (HUD) 1, which projects a projected image onto a display unit for displaying a virtual image, comprises an image illumination unit 3 that emits image light, and a first mirror 5 that reflects the image light from the image illumination unit 3 in order to project the image light as a projected image. The first mirror 5 is rotatable about a rotation axis 6. The rotation axis 6 is provided on the first mirror 5 such that, when viewed from its axis X direction, the length from the rotation axis 6 to one end of the first mirror 5 and the length from the rotation axis 6 to the other end of the first mirror 5 are different.

Description

Technical Field

[0001] The present disclosure relates to an image projection device.

Background Art

[0002] As a display device for vehicles, a head-up display (hereinafter referred to as HUD) that displays required images for vehicle occupants has been proposed.

[0003] As this HUD, for example, Patent Document 1 discloses a display device configured such that an image displayed on an image display element such as a liquid crystal (LCD) is projected onto the windshield of an automobile by an optical system, and an occupant visually recognizes a virtual image (hereinafter also referred to as a display image) formed by the image light reflected by this windshield.

[0004] The display device of Patent Document 1 includes a concave mirror as part of the optical system, and in order to allow occupants with different eye heights to visually recognize a suitable display image, a device for adjusting the position where the image light reflected by the concave mirror is projected onto the windshield is provided. Specifically, in Patent Document 1, a tilt arm is connected to a rotation axis provided on the concave mirror, and the angle of the reflecting surface of the concave mirror is adjusted by tilting this tilt arm with an actuator, thereby adjusting the reflection direction of the image light.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In HUDs, in order to make the space required for mounting on a vehicle as small as possible, it is required to configure the optical system to be small.

[0007] Therefore, the purpose of this disclosure is to provide an image projection device that can be miniaturized and cost-reduced. [Means for solving the problem]

[0008] An image projection device relating to one aspect of this disclosure is: An image projection device that projects a projected image onto a display unit for displaying a virtual image, An image illumination unit that emits image light, In order to project the aforementioned image light as the projected image, a first mirror that reflects the image light from the image illumination unit, Equipped with, The first mirror is rotatable around its axis of rotation, The rotating shaft is provided on the first mirror such that, when viewed from the axial direction, the length from the rotating shaft to one end of the first mirror is different from the length from the rotating shaft to the other end of the first mirror. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide an image projection device that can be miniaturized and cost-reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a head-up display (HUD) according to the embodiment of this disclosure, viewed from the side of a vehicle. [Figure 2] This figure shows an example of the configuration of the first mirror, rotation axis, tilting arm, and actuator included in the HUD shown in Figure 1. [Figure 3] This figure shows an example of the first mirror as viewed from its reflective surface side. [Figure 4] This figure shows an example of the rotation trajectory of the first mirror in the comparative example HUD. [Figure 5] This figure shows an example of the rotation trajectory of the first mirror in the HUD of this disclosure. [Figure 6]This figure shows an example of the configuration of the first mirror and actuator according to a modified example of the present disclosure. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will now be described with reference to the drawings. In the drawings, the up arrow indicates the upward direction of the illustrated structure. The down arrow indicates the downward direction of the illustrated structure. The forward arrow indicates the forward direction of the illustrated structure. The backward arrow indicates the rearward direction of the illustrated structure. The right arrow indicates the rightward direction of the illustrated structure. The left arrow indicates the leftward direction of the illustrated structure. These directions are relative directions set for the vehicle 10 shown in Figure 1, with the direction of travel of the vehicle 10 being the forward direction.

[0012] Figure 1 is a schematic diagram of a head-up display (HUD) according to an embodiment of the present disclosure, viewed from the side of a vehicle. As shown in Figure 1, the HUD 1 is mounted on a vehicle 10. For example, the HUD 1 is located in the dashboard of the vehicle 10. The HUD 1 functions as a visual interface between the vehicle 10 and its occupants. Specifically, the HUD 1 is configured to display predetermined information as a virtual image to the occupants of the vehicle 10 such that the information is superimposed on the real space outside the vehicle 10 (for example, the surrounding environment in front of the vehicle 10). The predetermined information is displayed as a still image or a moving image. The HUD 1 is an example of the “image projection device” of the present disclosure.

[0013] The HUD1 comprises a HUD housing 2, an image projection unit 3, a second mirror 4, a first mirror 5, a rotation axis 6, a tilting arm 7, an actuator 8, and a control unit 9. The HUD housing 2 has an emission window 21. The image projection unit 3, the second mirror 4, the first mirror 5, the rotation axis 6, the tilting arm 7, the actuator 8, and the control unit 9 are arranged inside the HUD housing 2. The emission window 21 is made of a transparent plate that transmits visible light.

[0014] The image illumination unit 3 is configured to generate a predetermined image for forming a virtual image and to emit light constituting the image (hereinafter referred to as image light). The image illumination unit 3 emits the image light toward the second mirror 4. The image light emitted from the image illumination unit 3 is, for example, visible light. The image illumination unit 3, although not shown in detail, includes a light source, optical components, and a display device. The light source is, for example, an LED light source or a laser light source. The LED light source is, for example, a white LED light source. The laser light source is, for example, an RGB laser light source configured to emit red laser light, green laser light, and blue laser light, respectively. The optical components include prisms, lenses, diffusers, magnifying glasses, etc. as appropriate. The optical components transmit the light emitted from the light source and emit it toward the display device. The display device is a liquid crystal display, a DMD (Digital Mirror Device), etc. The image projection unit 3 may use a raster scan method, a DLP (Digital Light Processing) method, or an LCOS (Liquid Crystal On Silicon) method. If a DLP or LCOS method is used, the light source for the image projection unit 3 may be an LED light source. If a liquid crystal display method is used, the light source for the image projection unit 3 may be a white LED light source.

[0015] The second mirror 4 is located on the optical path of the image light emitted from the image illumination unit 3, and is positioned between the image illumination unit 3 and the first mirror 5. The second mirror 4 reflects the image light emitted from the image illumination unit 3 toward the first mirror 5. The second mirror 4 is a non-rotating mirror whose orientation does not change. The second mirror 4 is composed of, for example, a convex mirror or a plane mirror. The second mirror 4 is provided, for example, to improve aberrations in the first mirror 5 and to substantially extend the focal length of the first mirror 5.

[0016] The first mirror 5 is on the optical path of the image light emitted from the image irradiation unit 3, and is disposed between the second mirror 4 and the windshield 11 of the vehicle 10. The first mirror 5 further reflects the image light reflected by the second mirror 4 and projects it as a projected image onto the windshield 11. The windshield 11 is an example of the "display unit" of the present disclosure. In this example, the first mirror 5 is disposed in front of the image irradiation unit 3 within the HUD housing 2. The first mirror 5 is configured, for example, as a concave mirror. The first mirror 5 reflects the image light emitted from the image irradiation unit 3 so that the image of the light emitted from the image irradiation unit 3 and imaged is imaged on the windshield 11 at a predetermined magnification.

[0017] The first mirror 5 has a rotation axis 6. The first mirror 5 is integrated with the rotation axis 6. The first mirror 5 is configured to be rotatable about the axis X of the rotation axis 6. The axis X of the rotation axis 6 extends in the left-right direction. The first mirror 5 integrated with the rotation axis 6 rotates about the axis X together with the rotation axis 6 by a predetermined angle as the rotation axis 6 rotates.

[0018] The rotation axis 6 is connected to one end of the tilt arm 7. The tilt arm 7 is provided so as to extend in the front-rear direction. The rotation axis 6 is connected to the front end of the tilt arm 7.

[0019] The end of the tilt arm 7 opposite to the end to which the rotation axis 6 is connected (hereinafter referred to as the other end) is engaged with the actuator 8. The tilt arm 7 is configured to tilt by the position of the other end of the tilt arm 7 moving due to the drive of the actuator 8. When the position of the other end of the tilt arm 7 moves, the rotation axis 6 connected to one end of the tilt arm 7 and the first mirror 5 integrated with the rotation axis 6 rotate. When the first mirror 5 rotates, the angle of the surface (reflective surface) of the first mirror 5 with respect to the image light emitted from the image irradiation unit 3 and reflected by the second mirror 4 changes.

[0020] The control unit 9 is configured to control the operation of each part of the HUD1. The control unit 9 is connected to the vehicle control device 12, which controls the movement of the vehicle 10. The control unit 9 can be implemented by one or more processors and memory. Examples of processors include a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a GPU (Graphics Processing Unit). Examples of memory include ROM (Read Only Memory) and RAM (Random Access Memory). In this case, ROM is an example of a non-temporary computer-readable medium that stores computer programs that perform processing related to the operation of each part of the HUD1. A general-purpose microprocessor selects at least a portion of the computer program stored in ROM, loads it onto RAM, and performs the above-mentioned processing in cooperation with RAM.

[0021] For example, the control unit 9 controls the operation of the image projection unit 3. Specifically, the control unit 9 generates a control signal to control the operation of the image projection unit 3 based on vehicle driving information and surrounding environment information transmitted from the vehicle control device 12, and transmits the control signal to the image projection unit 3. The vehicle driving information includes, for example, information related to the operation of the vehicle 10 (e.g., vehicle speed, information related to autonomous driving, etc.). The surrounding environment information includes, for example, information about objects existing outside the vehicle 10 (pedestrians, other vehicles including the vehicle in front, signs, etc.).

[0022] Furthermore, the control unit 9 controls the operation of the first mirror 5. Based on the position adjustment information of the virtual image (virtual image object I) transmitted from the vehicle control device 12, the control unit 9 generates a control signal to control the operation of the first mirror 5 and transmits the control signal to the actuator 8. Based on the control signal, the actuator 8 rotates the rotation axis 6 of the first mirror 5 around axis X. The position adjustment information of the virtual image object I includes, for example, occupant operation input information transmitted from an input device 13 that accepts operations from the occupants of the vehicle 10 to adjust the position of the virtual image object I shown in Figure 1.

[0023] In the HUD1 configured as described above, as illustrated in Figure 1, the image light L emitted from the image projection unit 3 is reflected by the first mirror 5 via the second mirror 4, and then emitted from the emission window 21 of the HUD housing 2. The image light L emitted from the emission window 21 is projected onto the windshield 11. A portion of the light projected onto the windshield 11 from the emission window 21 is reflected towards the occupant's viewpoint E. As a result, the occupant perceives the image light L emitted from the HUD housing 2 as a virtual image object I formed at a predetermined distance in front of the windshield 11. That is, the virtual image object is an image that appears as if it were projected into space when the image light L reflected by the windshield 11 reaches the occupant's viewpoint E (eyebox). In this way, the image generated by the image projection unit 3 is superimposed onto the real space in front of the vehicle 10 through the windshield 11, allowing the occupant to perceive the virtual image object I, formed by a predetermined image, as if it were floating on the road outside the vehicle 10.

[0024] Furthermore, when the input device 13 is operated by the crew, the actuator 8 rotates the first mirror 5 around the axis X of the rotation axis 6, for example, as shown by arrow A. As a result, the image light L, which is reflected by the first mirror 5 and then emitted from the emission window 21 of the HUD housing 2, changes its emission angle, for example, image light L1, image light L2, depending on the angle of the reflective surface of the first mirror 5. Consequently, the position of the eyebox from which the virtual image object I can be seen is displaced vertically. In this way, the crew can adjust the position of the virtual image object I according to their eye level (viewpoint E).

[0025] Figure 2 shows an example of the specific configuration of the first mirror 5, the rotating shaft 6, the tilting arm 7, and the actuator 8. As shown in Figure 2, the first mirror 5 is equipped with a reflective surface 51 that reflects image light emitted from the image illumination unit 3. The first mirror 5 is provided with a rotating shaft 6a that protrudes outward from the left side edge and a rotating shaft 6b that protrudes outward from the right side edge. The axis X connecting the rotating shafts 6a and 6b is positioned on the first mirror 5 so as to penetrate the mirror 5. These pair of rotating shafts 6a and 6b are rotatably supported by a frame 22 provided on the HUD 1. The configuration of the part where the rotating shafts 6a and 6b are supported by the frame 22 is, for example, configured as a sliding bearing in which the rotating shafts 6a and 6b are inserted into bearing holes (not shown) opened in the frame 22. The first mirror 5 is made capable of rotating relative to the frame 22 at a predetermined angle, for example as shown by arrow A, using these rotating shafts 6a and 6b as pivot points, and tilting the reflective surface 51.

[0026] Furthermore, the first mirror 5 is connected to one end 71 of the tilting arm 7 on one of the pair of rotating shafts 6a, 6b, the rotating shaft 6b. The connection between the rotating shaft 6b and the tilting arm 7 is made such that, for example, a semicircular connecting portion formed at the end of the rotating shaft 6b is fitted into a semicircular connecting hole opened in the tilting arm 7.

[0027] The tilting arm 7 is provided so as to extend in the front-rear direction, and the actuator 8 is engaged with the other end 72 opposite to the end 71 to which the rotation shaft 6b is connected. The tilting arm 7 is formed, for example, in the shape of an elongated plate, and is connected to the rotation shaft 6b of the first mirror 5 at one end 71 and engaged with the actuator 8 at the other end 72.

[0028] The actuator 8 is mounted, for example, on the HUD housing 2. The actuator 8 comprises a ring nut that is rotated at a reduced speed by the rotation of a pulse motor, and a screw rod 81 that is screwed onto this ring nut. The tip of the screw rod 81 is engaged with the other end 72 of the tilting arm 7 in a manner that allows for free movement. The screw rod 81 is engaged with the tilting arm 7, for example, via a ball joint 82.

[0029] When the ring nut is rotated by the reciprocating rotation of the pulse motor of the actuator 8, the screw rod 81 screwed into the ring nut is moved back and forth in the direction of the rod axis. In this example, the direction of the rod axis of the screw rod 81 is the vertical direction. This reciprocating movement of the screw rod 81 causes the other end 72 of the tilting arm 7, which is engaged with the screw rod 81, to move to multiple positions along the vertical direction, for example as shown by arrow B, with the rotation axis 6b provided at one end 71 as the pivot point. As the other end 72 of the tilting arm 7 moves to multiple positions along the vertical direction, the rotation axis 6b connected to one end 71 of the tilting arm 7 rotates, and the angle of the reflective surface 51 of the first mirror 5 with respect to the image light changes in multiple steps.

[0030] Figure 3 shows an example of the first mirror 5 as viewed from the reflective surface 51 side. As shown in Figure 3, the rotation axes 6a and 6b of the first mirror 5 are provided on the first mirror 5 such that, when viewed from the direction of the axis X of the rotation axes 6a and 6b, the length from the rotation axes 6a and 6b to one end of the first mirror 5 is different from the length from the rotation axes 6a and 6b to the other end of the first mirror 5. In other words, the rotation axes 6a and 6b are provided at positions offset from the center of the vertical length of the first mirror 5 when viewed from the direction of their axis X. To put it another way, the axis X of the rotation axes 6a and 6b is provided along the width direction (left-right direction) of the first mirror 5, and the position of that axis X is located at a position offset from the center of the height direction (direction perpendicular to the width direction) of the first mirror 5.

[0031] One end of the first mirror 5 is the upper end of the first mirror 5 (for example, the upper end 5u). The other end of the first mirror 5 is the lower end of the first mirror 5 (for example, the lower end 5d). In other words, in this example, the rotation axes 6a and 6b are positioned above the center of the first mirror 5.

[0032] The reflective surface 51 of the first mirror 5 shown in Figure 3 determines the size of the area of ​​the occupant's eyebox (viewpoint E shown in Figure 1). The upper area of ​​the reflective surface 51 is the area necessary to form the upper area of ​​the eyebox. Conversely, the lower area of ​​the reflective surface 51 is the area necessary to form the lower area of ​​the eyebox. Therefore, in this embodiment, the axis X of the rotation axes 6a and 6b is positioned eccentrically from the center of the eyebox.

[0033] The rotating axes 6a and 6b are positioned such that the ratio of the length R1 from axis X to the upper end 5u to the length R2 from axis X to the lower end 5d is within the range of R1:R2 = 1:1.1 to 1:3.

[0034] Figure 4 shows an example of the rotation trajectory of the first mirror 105 in the comparative example HUD. As shown in Figure 4, the rotation axis 106 of the first mirror 105 in the comparative example is located at the center of the vertical length of the first mirror 105.

[0035] Furthermore, the dashed circle in Figure 4 represents a hypothetical rotational trajectory 131 that the first mirror 105 may follow when it is rotated around the rotation axis 106. When the first mirror 105 is rotated within a predetermined angle range as shown by arrow A, the vertical range in which the upper end 105u of the first mirror 105 rotates is from the position of the rotation axis 106 to a position moved upward by a height H1.

[0036] Note that the image light L101 shown in Figure 4 represents the image light reflected by the reflective surface 51 when the first mirror 105 is rotated to the position of the first mirror 105a. Also, the image light L102 represents the image light reflected by the reflective surface 51 when the first mirror 105 is rotated to the position of the first mirror 105b.

[0037] Figure 5 shows an example of the rotation trajectory of the first mirror 5 in the HUD1 of this disclosure. As shown in Figure 5, the rotation axis 6 (6a, 6b) of the first mirror 5 of this disclosure is located at a position offset above the center of the vertical length of the first mirror 5.

[0038] Furthermore, in Figure 5, a dashed line shows a hypothetical rotational trajectory 31 that the upper end 5u of the first mirror 5 may pass through when the first mirror 5 is rotated within a predetermined angle range around the rotation axis 6 (6a, 6b). When the first mirror 5 is rotated within a predetermined angle range as shown by arrow A, the vertical range in which the upper end 5u of the first mirror 5 rotates is from the position of the rotation axis 6 (6a, 6b) to a position moved upward by a height H2.

[0039] Note that the image light L3 shown in Figure 5 represents the image light reflected by the reflective surface 51 when the first mirror 5 is rotated to the position of the first mirror 5a. Also, the image light L4 represents the image light reflected by the reflective surface 51 when the first mirror 5 is rotated to the position of the first mirror 5b.

[0040] In the embodiment of this disclosure, the first mirror 5 has its rotation axis 6(6a,6b) positioned above the center. Therefore, the length from the rotation axis 6(6a,6b) to the upper end 5u in the first mirror 5 is shorter than the length from the rotation axis 106 to the upper end 105u in the comparative example first mirror 105. Consequently, the height H2 from the rotation axis 6(6a,6b) when the upper end 5u of the first mirror 5 moves is lower than the height H1 from the rotation axis 106 when the upper end 105u of the first mirror 105 moves.

[0041] As described above, in this embodiment, the HUD (Image Projection Device) 1 has a first mirror 5 that is rotatable around rotation axes 6a and 6b, and the rotation axes 6a and 6b are provided on the first mirror 5 such that the length R1 from the rotation axes 6a and 6b to the upper end 5u of the first mirror 5 and the length R2 from the rotation axes 6a and 6b to the lower end 5d of the first mirror 5 are different when viewed from the axis X direction. With this configuration, the rotation axes 6a and 6b are provided on the first mirror 5 such that the length R1 from the rotation axes 6a and 6b to the upper end 5u of the first mirror 5 and the length R2 from the rotation axes 6a and 6b to the lower end 5d of the first mirror 5 are unequal. In other words, the rotation axes 6a and 6b of the first mirror 5 are provided offset from the center of the length of the first mirror 5 in the vertical direction. For this reason, the upward range of rotation of the upper end 5u of the first mirror 5 when the first mirror 5 is rotated within a predetermined angle range can be suppressed (for example, the height H2 in Figure 5 can be lowered).

[0042] By the way, when the first mirror 5 is rotated around the rotation axes 6a and 6b, other components cannot be placed on the rotation trajectory, which is the range of movement of the first mirror 5, in order to prevent interference with other components of the HUD 1. In contrast, in this embodiment, the upward range in which the upper end 5u of the first mirror 5 rotates when the first mirror 5 is rotated can be suppressed, so it becomes possible to position the first mirror 5 higher in the HUD housing 2 than in the conventional case. In other words, a wider empty space can be secured below the first mirror 5. As a result, it becomes possible to lay out the components of the HUD 1, including the first mirror 5, more freely. In addition, since the space above the first mirror 5 in the HUD 1 can be reduced, it becomes possible to miniaturize the HUD 1 in the vertical direction of the vehicle 10, and consequently, it becomes possible to reduce component costs. Furthermore, it becomes possible to enlarge the eyebox by increasing the size of the first mirror 5 while maintaining the same dimensions as before for the HUD1. In this case, if the size of the eyebox can cover a certain number of angle change steps in the first mirror 5, it becomes possible to reduce the amount of rotation of the first mirror 5 or to further simplify the rotation mechanism, thereby reducing costs.

[0043] Furthermore, according to HUD1, the ratio of the length R1 from the rotation axes 6a, 6b to the upper end 5u to the length R2 from the rotation axes 6a, 6b to the lower end 5d is configured to be within the range of R1:R2 = 1:1.1 to 1:3. For example, if the lengths R1 and R2 are made the same as in the conventional design, it becomes difficult to freely arrange the components of HUD1. On the other hand, if R2 is made larger than 3 when R1 is set to 1, there is a high possibility that distortion of the projected image will occur due to the rotation of the first mirror 5, or that the load applied to the connection between the rotation axes 6a, 6b and the first mirror 5 will increase. Therefore, by setting R1:R2 within the range of 1:1.1 to 1:3, it is possible to freely arrange the components of HUD1 while suppressing distortion of the projected image due to the rotation of the first mirror 5, and further limiting the load applied to the connection between the rotation axes 6a, 6b and the first mirror 5, thereby suppressing deterioration of the rotation mechanism.

[0044] Furthermore, the HUD1 includes a tilting arm 7 with one end 71 connected to a rotation axis 6b, and an actuator 8 engaged with the other end 72 of the tilting arm 7. By driving the actuator 8, the other end 72 of the tilting arm 7 moves to multiple positions, thereby changing the angle of the reflective surface 51 of the first mirror 5 with respect to the image light in multiple stages. With this configuration, by adjusting the angle of the reflective surface 51 of the first mirror 5 in multiple stages using the actuator 8 and the tilting arm 7, the display position and display direction of the projected image can be changed in multiple stages. This makes it possible to suitably display the projected image to occupants with different line-of-sight positions with a simple configuration.

[0045] (modified version) Figure 6 shows a modified example of the first mirror and actuator. The same parts as those in the example described in Figure 2 are denoted by the same reference numerals. In this modified example, the first mirror 5, like the first mirror 5 in Figure 2, is provided with a pair of rotating shafts 6a and 6b on its left and right side edges. These rotating shafts 6a and 6b are rotatably supported by the frame 22, and as shown by arrow A, they can rotate at a predetermined angle to tilt the reflective surface 51.

[0046] On the other hand, this modified example differs from the example in Figure 2, in that one end 71A of the gear arm 7A is connected to the rotation axis 6b of the first mirror 5, while the other end 72A opposite to the one end 71A is engaged with the actuator 8A.

[0047] The gear arm 7A is configured to tilt when the position of its other end 72A moves due to the drive of the actuator 8A, thereby changing the angle of the first mirror 5. A gear (sector gear) 73 that engages with the actuator 8A is integrally formed on the other end 72A of the gear arm 7A.

[0048] Actuator 8A is composed of a pulse motor with a reduction mechanism, and a small gear 83 is provided on its rotating shaft. The small gear 83 of actuator 8A is meshed with the gear 73 of gear arm 7A. When actuator 8A is driven and the small gear 83 rotates, the gear 73 of gear arm 7A, which is meshed with the small gear 83, rotates by a small angle, causing gear arm 7A to tilt.

[0049] The gear arm 7A moves to multiple positions vertically, with the other end 72A, on which the gear 73 is formed, pivoting around the rotation axis 6b of the one end 71A. As the other end 72A of the gear arm 7A moves to multiple positions vertically, the rotation axis 6b connected to the one end 71A of the gear arm 7A rotates, and the angle of the reflective surface 51 of the first mirror 5 with respect to the image light changes in multiple steps.

[0050] In this way, by adjusting the angle of the reflective surface 51 of the first mirror 5 in multiple stages using the actuator 8A and the gear arm 7A, it is possible to change the display position and display direction of the projected image in multiple stages. This makes it possible to make the projected image suitable for each occupant with different line of sight positions using a simple configuration.

[0051] (A modified configuration of the second mirror 4) The second mirror 4 described in the above embodiment was non-rotating and did not change the orientation of the reflective surface, but is not limited to this. The second mirror 4 may be configured to be rotatable about a rotation axis.

[0052] For example, the second mirror 4, like the first mirror 5, may have rotation axes protruding from its left and right side edges, and may be rotatable about these rotation axes. In that case, the rotation axis of the second mirror 4 may be provided on the second mirror 4 such that the length from the rotation axis to one end of the second mirror 4 is different from the length from the rotation axis to the other end of the second mirror 4 when viewed from the axial direction, or it may be provided at the center of the vertical length of the second mirror 4. The rotation axis of the second mirror 4 is an example of the "second rotation axis" of this disclosure.

[0053] Thus, the modified second mirror 4, like the first mirror 5, is rotatable about a rotation axis, and the rotation axis may be positioned offset from the center of the second mirror 4's vertical length. This configuration allows for greater flexibility in the layout of the components of the HUD 1, including the first mirror 5 and the second mirror 4, thus enabling further miniaturization of the HUD 1. Furthermore, the function for controlling changes in the display position and direction of the projected image illuminated by the image light can be distributed not only to the rotation of the first mirror 5 but also to the rotation of the second mirror 4, allowing for significant changes in the display position and direction of the projected image. In addition, when the HUD 1 is not in use, the reflective surfaces of the first mirror 5 and the second mirror 4 can be rotated to prevent external light, such as sunlight, from entering the image illumination unit 3.

[0054] While embodiments of this disclosure have been described above, it goes without saying that the technical scope of this disclosure should not be interpreted restrictively by the description of these embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the disclosure described in the claims. The technical scope of this disclosure should be determined based on the scope of the disclosure described in the claims and its equivalents.

[0055] In the above embodiment, an example of changing the rotation angle of the first mirror 5 using the actuator 8 was described in which the occupant operates the input device 13, but the invention is not limited to this. For example, the rotation angle of the first mirror 5 may be automatically controlled by eye tracking the occupant's line of sight using an eye tracker or eye camera.

[0056] In the above embodiment, a case in which the second mirror 4 is placed between the image irradiation unit 3 and the first mirror 5 was described, but the embodiment is not limited to this. The second mirror 4 is not essential, and for example, a configuration without the second mirror 4 may be used. That is, the image light irradiated from the image irradiation unit 3 may be directly incident on the first mirror 5 without passing through the second mirror 4.

[0057] In the above embodiment, the control unit 9 and the vehicle control device 12 are provided as separate components, but the system is not limited to this. For example, the control unit 9 may be configured integrally with the vehicle control device 12.

[0058] This disclosure includes the following aspects: (1) An image projection device that projects a projected image onto a display unit for displaying a virtual image, An image illumination unit that emits image light, In order to project the aforementioned image light as the projected image, a first mirror that reflects the image light from the image illumination unit, Equipped with, The first mirror is rotatable around its axis of rotation, An image projection device wherein the rotation axis is provided on the first mirror such that, when viewed from the axial direction, the length from the rotation axis to one end of the first mirror is different from the length from the rotation axis to the other end of the first mirror. (2) The image projection apparatus according to (1), wherein the ratio of the length from the rotation axis to one end to the length from the rotation axis to the other end is in the range of 1:1.1 to 1:3. (3) The image projection apparatus according to (2), wherein one end is the upper end of the first mirror and the other end is the lower end of the first mirror. (4) A tilting arm with one end connected to the rotation shaft, An actuator engaged with the other end of the tilting arm, Furthermore, The image projection apparatus according to any one of (1) to (3), wherein the other end of the tilting arm moves to multiple positions by driving the actuator, thereby changing the angle of the reflective surface of the first mirror with respect to the image light in multiple steps. (5) The system further comprises a second mirror positioned on the optical path of the image light between the image illuminator and the first mirror, which reflects the image light toward the first mirror, The second mirror is rotatable about the second axis of rotation, The image projection apparatus according to any one of (1) to (4), wherein the second rotation axis is provided on the second mirror such that, when viewed from the axial direction thereof, the length from the second rotation axis to one end of the second mirror is different from the length from the second rotation axis to the other end of the second mirror. [Explanation of symbols]

[0059] 1 HUD 2 HUD Housings 3 Image irradiation area 4. Second Mirror 5,5a,5b First mirror 5u top end 5d bottom edge 6, 6a, 6b Rotation axis 7. Tilting Arm 7A Gear Arm 8.8A Actuator 9. Control Unit 10 vehicles 11 Windshield 12 Vehicle control system 13 Input device 21 Ejection window 22 frames 51 Reflective surface 71,71A One end 72,72A Other end 73. Gear (sector gear) 81 Screw Rod 82 Ball joint 83 Small Gear E perspective Illusion object L, L1, L2, L3, L4, Image light X axis

Claims

1. An image projection device that projects a projected image onto a display unit for displaying a virtual image, An image illumination unit that emits image light, In order to project the aforementioned image light as the projected image, a first mirror that reflects the image light from the image illumination unit, Equipped with, The first mirror is rotatable around its axis of rotation, An image projection device wherein the rotation axis is provided on the first mirror such that, when viewed from the axial direction, the length from the rotation axis to one end of the first mirror is different from the length from the rotation axis to the other end of the first mirror.

2. The image projection apparatus according to claim 1, wherein the ratio of the length from the rotation axis to one end to the length from the rotation axis to the other end is in the range of 1:1.1 to 1:

3.

3. The image projection apparatus according to claim 2, wherein one end is the upper end of the first mirror and the other end is the lower end of the first mirror.

4. A tilting arm with one end connected to the rotation shaft, An actuator engaged with the other end of the tilting arm, Furthermore, The image projection apparatus according to claim 1 or 2, wherein the other end of the tilting arm moves to a plurality of positions by driving the actuator, thereby changing the angle of the reflective surface of the first mirror with respect to the image light in a plurality of steps.

5. The system further comprises a second mirror positioned on the optical path of the image light, between the image irradiation unit and the first mirror, which reflects the image light toward the first mirror, The second mirror is rotatable about the second axis of rotation, The image projection apparatus according to claim 1 or 2, wherein the second rotation axis is provided on the second mirror such that, when viewed from the axial direction thereof, the length from the second rotation axis to one end of the second mirror is different from the length from the second rotation axis to the other end of the second mirror.

Images