Image projector

Abstract

To provide an image projector which can improve the visibility by changing the position of image formation of a virtual image.SOLUTION: An image projector for projecting image light to a display unit (WS) for displaying a virtual image includes: an image display unit (10) for radiating image light; a primary mirror (20) for reflecting the image light which has entered from the image display unit (10); and a mirror position changing unit (60) for changing the relative position of the primary mirror (20) to the image display unit (10).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image projection device, and more particularly to an image projection device that projects image light onto a display unit for displaying a virtual image. [Background technology]

[0002] Conventionally, dashboards that light up icons have been used as devices for displaying various types of information inside a vehicle. As the amount of information to be displayed increases, it has been proposed to embed an image display device in the dashboard or to configure the entire dashboard with an image display device.

[0003] However, since the instrument panel is located below the windshield of the vehicle, in order for a driver or other passenger to view the information displayed on the instrument panel, the driver or other passenger must move his or her eyes downward while driving, which is undesirable. Therefore, image projection devices such as head up displays (hereinafter referred to as HUDs) have been proposed that project images onto the windshield so that passengers can read information when they view the area ahead of the vehicle (see, for example, Patent Documents 1 and 2).

[0004] In the image projection devices of Patent Documents 1 and 2, an image display unit emits irradiation light containing an image, and the irradiation light is reflected by a free-form mirror or the like, and the image reaches the viewpoint of the passenger so that it is formed in space via a display unit such as a windshield. This allows the passenger to recognize that the image is being displayed at the imaging position in the depth direction due to the irradiation light incident on the viewpoint. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-119248 A [Patent Document 2] JP 2019-119262 A Summary of the Invention [Problem to be solved by the invention]

[0006] In such a conventional image projection device, a virtual image is formed at a predetermined distance in front of the vehicle, but when the distance between the vehicle and the vehicle ahead is short, the virtual image may be formed at a position farther away than the vehicle ahead. When the positions of such a virtual image and the vehicle ahead are reversed, there is a problem that the visibility of the virtual image is significantly reduced.

[0007] SUMMARY OF THE PRESENT DISCLOSURE ... The present invention has been made in consideration of the above-mentioned problems in the conventional art, and has an object to provide an image projection device that can improve visibility by changing the imaging position of a virtual image. [Means for solving the problem]

[0008] In order to solve the above problems, the image projection device of the present invention is an image projection device that projects image light onto a display unit for displaying a virtual image, and is characterized in having an image display unit that irradiates the image light, and a primary mirror that reflects the image light incident from the image display unit, and is equipped with a mirror position change unit that changes the relative position of the primary mirror with respect to the image display unit.

[0009] In the image projection device of the present invention, the mirror position change unit changes the relative position of the primary mirror with respect to the image display unit, thereby changing the imaging position of the virtual image to a position closer to the vehicle than the vehicle in front, thereby improving visibility.

[0010] In addition, in one aspect of the present invention, the mirror position changer translates the primary mirror.

[0011] In addition, in one aspect of the present invention, the mirror position changer further rotates the primary mirror.

[0012] In addition, in one aspect of the invention, the exit position of the image light in the image display unit is changed in conjunction with the operation of the mirror position change unit.

[0013] In one aspect of the present invention, the image light includes near image light that forms the virtual image at a first distance and far image light that forms the virtual image at a second distance farther than the first distance, the primary mirror includes a near primary mirror that reflects the near image light and a far primary mirror that reflects the far image light, and the mirror position change unit changes only the position of the far primary mirror.

[0014] In one aspect of the present invention, the optical system further includes a secondary mirror onto which the near image light and the far image light are incident and which reflects the light toward the display unit.

[0015] In one aspect of the present invention, a vehicle distance acquisition unit is provided that acquires vehicle distance information, and the mirror position change unit changes the position of the primary mirror in accordance with the vehicle distance information. Effect of the Invention

[0016] The present invention can provide an image projection device that can improve visibility by changing the imaging position of a virtual image. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a schematic diagram illustrating projection of a virtual image using the image projection device 100 according to the first embodiment. [Diagram 2] 2A and 2B are schematic diagrams explaining the imaging positions of virtual images P1 and P2 by the image projection device 100, where FIG. 2(a) shows a case where a sufficient distance is secured between the vehicles, and FIG. 2(b) shows a case where a sufficient distance is not secured between the vehicles. [Diagram 3] FIG. 1 is a schematic cross-sectional view illustrating an overview of an image projection device 100 according to a first embodiment. [Figure 4] 4 is a flowchart illustrating an image projection method using the image projection device 100 according to the first embodiment. [Diagram 5] FIG. 11 is a schematic cross-sectional view illustrating an overview of an image projection device 100 according to a second embodiment. [Figure 6]FIG. 11 is a schematic cross-sectional view illustrating an overview of an image projection device 100 according to a third embodiment. [Figure 7] 7A and 7B are schematic diagrams for explaining the imaging positions of virtual images P1 and P2 by the image projection device 100 according to the fourth embodiment, where FIG. 7(a) shows a case where a sufficient distance between vehicles is secured, and FIG. 7(b) shows a case where a sufficient distance between vehicles is not secured. [Figure 8] FIG. 11 is a schematic cross-sectional view illustrating an overview of an image projection device 100 according to a fourth embodiment. [Figure 9] 13 is a flowchart illustrating an image projection method using the image projection device 100 according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In the following description, an embodiment in which an image projection device 100 according to the present invention is applied to a HUD mounted on a vehicle or the like will be described as an example. FIG. 1 is a schematic diagram for explaining the projection of a virtual image using the image projection device 100 according to this embodiment. The dashed line shown in FIG. 1 indicates the optical path of a first image light L1, which will be described later, and the dashed line indicates the optical path of a second image light L2. As shown in FIG. 1, the first image light L1 and the second image light L2 projected from the image projection device 100 are reflected by a windshield (display unit) WS and irradiated to the driver's viewpoint position. The driver visually recognizes virtual images P1 and P2 formed on the extension of the optical path along which the first image light L1 and the second image light L2 are incident. In this embodiment, an example is shown in which the image projection device 100 projects the first image light L1 and the second image light L2 to form two images P1 and P2, but the number of virtual images is not limited.

[0019] The windshield WS is a part provided in front of the driver's seat of the vehicle and transmits visible light. The windshield WS reflects the first image light L1 and the second image light L2 incident from the image projection device 100 toward the viewpoint direction on the inner surface of the vehicle and transmits light from the outside of the vehicle toward the viewpoint direction, and therefore corresponds to the display unit in the present invention. Here, an example is shown in which the windshield WS is used as the display unit, but a combiner may be prepared as a display unit separate from the windshield WS and may reflect light from the image projection device 100 toward the viewpoint direction. In addition, the display unit is not limited to being located in front of the vehicle, and may be located to the side or rear as long as it projects an image toward the viewpoint of the passenger.

[0020] The virtual images P1 and P2 are images that are displayed as if they were formed in space when the first image light L1 and the second image light L2 reflected by the windshield WS reach the viewpoint (eyebox) of the passenger. The positions at which the virtual images P1 and P2 are formed depend on the composite focal length of the projection optical unit included in the image projection device 100 and the windshield WS.

[0021] In the image projection device 100 of this embodiment, a distant image displayed in the distant display area 10a of the image display unit 10 is irradiated as a first image light L1, and a near image displayed in the near display area 10b is irradiated as a second image light L2. Examples of distant images displayed in the distant display area 10a include images calling attention and auxiliary information related to driving, such as emergency information. Examples of near images displayed in the near display area 10b include speed and volume indicators, driving direction guides, etc.

[0022] FIG. 2 is a schematic diagram for explaining the image formation positions of virtual images P1 and P2 by the image projection device 100, where FIG. 2(a) shows a case where the vehicle distance is sufficiently secured, and FIG. 2(b) shows a case where the vehicle distance is not sufficiently secured. The vehicle C1 shown in the figure is a vehicle equipped with the image projection device 100, and the vehicle ahead C2 is a vehicle traveling ahead of the vehicle C1. The virtual image P1 is formed at a position farther from the vehicle C1 than the virtual image P2. The image displayed by the virtual image P1 is a distant image, and the image displayed by the virtual image P2 is a near image. FIG. 2 shows an example where the position where the normal virtual image P1 is formed is about 8 to 15 m ahead of the vehicle C1. The position where the virtual image P2 is formed is 2 to 3 m ahead of the vehicle C1. In addition, the imaging position of the virtual image P1, which is a near image, is lower than the imaging position of the virtual image P2, which is a far image, and the depression angle from the viewpoint position of the host vehicle C1 is large.

[0023] In the image projection device 100 of this embodiment, as shown in Fig. 2(a), when the distance between the vehicle C1 and the preceding vehicle C2 is greater than the distance between the position where the virtual image P1 is normally formed and the vehicle C1, the virtual image P1 is formed at the normal image forming position. Also, as shown in Fig. 2(a), when the distance between the vehicle C1 and the preceding vehicle C2 is smaller than the distance between the position where the virtual image P1 is normally formed and the vehicle C1, the position where the virtual image P1 is formed is changed to be closer to the vehicle C1. In Figs. 2(a) and 2(b), an example is shown in which the image forming position of the virtual image P2 is not changed regardless of the distance between the vehicle C1 and the preceding vehicle C2, but the image forming position of the virtual image P2 may be changed.

[0024] FIG. 3 is a schematic cross-sectional view for explaining an overview of the image projection device 100 according to this embodiment. As shown in FIG. 3, the image projection device 100 includes an image display unit 10, a primary mirror for far distances 20, a primary mirror for near distances 30, a secondary mirror 40, a prism 50, a mirror position change unit 60, and a vehicle distance acquisition unit 70. In the image projection device 100, each unit is controlled using a control unit (not shown) connected to each unit so as to be able to communicate information with the unit. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for performing information processing, a memory device, a recording medium, an information communication device, and the like. The control unit controls the operation of each unit according to a predetermined program, and sends information including an image (image information) to the image display unit 10.

[0025] The image display unit 10 is a part that irradiates the far-distance primary mirror 20 with light containing an image as image light based on image information from the control unit. The image display unit 10 has a far-distance display area 10a and a near-distance display area 10b, and displays a far-distance image in the far-distance display area 10a and irradiates a first image light L1 (far-distance image light), and displays a near-distance image in the near-distance display area 10b and irradiates a second image light L2 (near-distance image light). Here, the far-distance display area 10a and the near-distance display area 10b may each be configured with a separate display device, but it is preferable to use one display device divided into two areas.

[0026] The primary mirror for distance 20 is an optical member that reflects the image light for distance irradiated from the far display area 10a toward the secondary mirror 40. In the example shown in Fig. 3, the primary mirror for distance 20 is a flat reflecting mirror, but a reflecting mirror with a concave or convex surface may be used. In addition, when the primary mirror for distance 20 is configured with a curved surface, it is not limited to a surface with a constant curvature, and a paraboloid of revolution, an ellipsoid, a free curved surface mirror, etc. may be used.

[0027] The near primary mirror 30 is an optical member that reflects the near image light irradiated from the near display area 10b toward the secondary mirror 40. In the example shown in Fig. 3, the near primary mirror 30 is a flat reflecting mirror, but a concave or convex reflecting mirror may be used. In addition, when the near primary mirror 30 is configured with a curved surface, it is not limited to a surface with a constant curvature, and a paraboloid of revolution, an ellipsoid, a free curved surface mirror, etc. may be used.

[0028] The secondary mirror 40 is an optical member that reflects, in the direction of the windshield WS, the far-distance image light arriving from the far-distance primary mirror 20 and the near-distance image light arriving from the near-distance primary mirror 30. In the example shown in Fig. 3, the secondary mirror 40 is a free-form mirror with an optically designed concave shape necessary for projecting the far-distance image light and the near-distance image light as virtual images P1, P2.

[0029] The reflecting surfaces of the primary mirror 20 for far distances, the primary mirror 30 for near distances, and the secondary mirror 40 are designed to expand the light diameter in the driver's viewpoint direction in order to project the far image light and the near image light as virtual images P1 and P2 through the windshield WS. Here, the expansion of the light diameter in the viewpoint direction includes not only the case where the light diameter expands consistently after reflection, but also the case where the light diameter shrinks and expands after forming an image at an intermediate point. The combination of the primary mirror 20 for far distances, the primary mirror 30 for near distances, and the secondary mirror 40 has the function of projecting the far image light and the near image light through the windshield WS, and corresponds to the irradiation optical unit in the present invention.

[0030] 1 and 3, the optical paths of the first image light L1 (far image light) and the second image light L2 (near image light) are depicted as a straight line. However, the actual far image light and near image light are displayed in a predetermined area in the far display area 10a and the near display area 10b of the image display unit 10, and have a predetermined area in a direction perpendicular to the traveling direction. In addition, the far image light and the near image light may be reflected by the far primary mirror 20 and the near primary mirror 30, and travel with their light diameters reduced, and may be intermediately imaged at an intermediate image position between the far primary mirror 20 and the secondary mirror 40, or between the near primary mirror 30 and the secondary mirror 40.

[0031] The prism 50 is an optical member that splits the light of the image irradiated from the image display unit 10, and splits the image light for far distance irradiated from the far display area 10a and the image light for near distance irradiated from the near display area 10b. Here, an example in which the prism 50 is used as an optical member for splitting the light is shown, but a method of making the angle of incidence and the angle of reflection of light different using a reflecting mirror may be used. In the example shown in FIG. 3, the prism 50 is arranged overlapping the far display area 10a. Therefore, the image light for far distance irradiated from the far display area 10a is branched into a path different from the image light for near distance and reaches the primary mirror for far distance 20. Moreover, the image light for near distance irradiated from the near display area 10b reaches the primary mirror for near distance 30.

[0032] Here, arranging the prism 50 so as to overlap the far display region 10a means that the region in which the prism 50 is arranged overlaps the far display region 10a in a plan view. In addition, the overlapping arrangement includes both the case where the prism 50 and the image display unit 10 are in contact with each other and the case where they are not in contact with each other. In addition, the overlapping arrangement also includes the case where an optical member that transmits light or a holding member for maintaining the distance between the prism 50 and the image display unit 10 is interposed between the prism 50 and the image display unit 10. In addition, although an example in which the prism 50 is arranged so as to overlap the far display region 10a is shown in FIG. 3, if the emission directions of the far image light and the near image light from the image display unit 10 can be separated and can reach the far primary mirror 20 and the near primary mirror 30, respectively, the prism 50 may be omitted.

[0033] The mirror position change unit 60 is a part that changes the relative position of the distance primary mirror 20 with respect to the image display unit 10. The mirror position change unit 60 translates or rotates the distance primary mirror 20 based on a control signal from the control unit, thereby changing the traveling path of the distance image light reflected by the distance primary mirror 20. The specific configuration of the mirror position change unit 60 is not limited, but a configuration that changes the position or orientation of the distance primary mirror 20 by an extension / contraction operation using a linear actuator, a rotation operation using a swivel mechanism, or the like can be used.

[0034] The inter-vehicle distance acquisition unit 70 is a part that acquires the distance between the host vehicle C1 and the preceding vehicle C2 as inter-vehicle distance information. The configuration of the inter-vehicle distance acquisition unit 70 is not limited, and the inter-vehicle distance information may be acquired from outside the image projection device 100 using an information communication means. The method of acquiring the inter-vehicle distance information is also not limited, and an image of the preceding vehicle C2 may be captured by a camera for an advanced driver-assistance system (ADAS) mounted on the host vehicle C1, and the inter-vehicle distance information may be acquired by image recognition. In addition, a millimeter wave radar sensor, a LiDAR (Light Detection And Ranging), an ultrasonic sensor, or the like mounted on the host vehicle C1 may be used.

[0035] In the image projection device 100 shown in Fig. 3, the mirror position change unit 60 changes the position of the far-distance primary mirror 20 based on the vehicle distance information acquired by the vehicle distance acquisition unit 70. In Fig. 3, the position of the far-distance primary mirror 20' when a virtual image P1' is formed at a normal imaging position and the path of the far-distance image light are shown by dashed lines. Also, the position of the far-distance primary mirror 20 and the path of the far-distance image light are shown by solid lines when the distance between the vehicle C1 and the leading vehicle C2 is closer than the normal imaging position and the imaging position of the virtual image P1 is closer to the vehicle C1 than normal. Also, the path of the near-distance image light is shown by dashed lines.

[0036] As shown in FIG. 3, the image light for far distances irradiated from the far distance display area 10a is branched by the prism 50, and is reflected by the far distance primary mirror 20, the secondary mirror 40, and the windshield WS to reach the driver's viewpoint, and virtual images P1' and P1 are formed in the distance. The image light for near distances irradiated from the near distance display area 10b is reflected by the near distance primary mirror 30, the secondary mirror 40, and the windshield WS to reach the driver's viewpoint, and virtual image P2 is formed in the near distance. As a result, in the image projection device 100, the virtual image P1 is projected in the far distance several degrees below the horizontal direction, and the driver's line of sight movement to visually recognize the driving support information can be reduced. In addition, the virtual image P2 is projected further downward near, and the vehicle speed display and the like can be visually recognized well by moving the line of sight.

[0037] In the present embodiment shown in FIG. 3, the mirror position change unit 60 translates the far-field primary mirror 20 in a direction perpendicular to the reflecting surface to reduce the distance between the image display unit 10 and the far-field primary mirror 20. By translating the far-field primary mirror 20 from its position before the position change, the incident position of the far-field image light shown by the solid line in FIG. 3 on the far-field primary mirror 20 changes. This changes the incident position of the far-field image light on the secondary mirror 40 and the windshield WS, and the imaging position of the virtual image P1 also changes. At this time, since the distance from the far-field display area 10a to the far-field primary mirror 20 is shortened, the imaging position of the virtual image P1 becomes closer than the imaging position of the virtual image P1' before the change.

[0038] 4 is a flowchart for explaining an image projection method using the image projection device 100 according to this embodiment. As shown in FIG. 4, in the preparation process of step S11 in the image projection method of this embodiment, a far image and a near image are displayed in the far display area 10a and the near display area 10b of the image display unit 10, respectively, and virtual images P1 and P2 are projected via the windshield WS. In addition, the inter-vehicle distance acquisition unit 70 starts detecting the preceding vehicle C2 and starts acquiring information on the inter-vehicle distance from the preceding vehicle C2. In addition, the driver's viewpoint position is detected using an imaging device provided in the vehicle and image recognition technology, etc., as necessary.

[0039] Next, in the preceding vehicle detection process of step S12, it is determined whether or not a preceding vehicle C2 is present based on the following distance information acquired by the following distance acquisition unit 70. If a preceding vehicle C2 is present, the process proceeds to step S13; if not, step S12 is repeated to continue projecting the distant image and the close image.

[0040] Next, in the inter-vehicle distance measurement step in step S13, the distance between the host vehicle C1 and the preceding vehicle C2 is calculated or acquired from the inter-vehicle distance information acquired by the inter-vehicle distance acquisition unit 70, and the process proceeds to step S14. Here, the preceding vehicle detection step and the inter-vehicle distance measurement step are shown as separate steps, but they may be executed simultaneously as one step.

[0041] Next, in the overlap determination step of step S14, the vehicle distance acquired in the vehicle distance measurement step is compared with the distance between the imaging position of the virtual image P1 and the vehicle C1, and it is determined whether the rear end of the leading vehicle C2 is closer than the imaging position of the virtual image P1. If the rear end of the leading vehicle C2 is closer than the virtual image P1, the process proceeds to step S15, and if not, the process proceeds to step S12. Here, an example is shown in which the imaging position of the virtual image P1 is compared with the rear end position of the leading vehicle C2, but it may be determined whether a predetermined distance is secured between the imaging position of the virtual image P1 and the rear end position of the leading vehicle C2.

[0042] Next, in the mirror position changing process of step S15, the position where the virtual image P1 of the far-field image is formed is determined based on the vehicle distance acquired in the vehicle distance measuring process, and the mirror position changing unit 60 changes the position of the far-field primary mirror 20 based on the determined imaging position. Although the specific method of determining the imaging position of the virtual image P1 is not limited, an example is a method of determining in advance the correspondence relationship (vehicle-to-vehicle imaging position relationship) between the distance between the rear end position of the leading vehicle C2 and the vehicle C1, and the imaging position of the virtual image P1, and referring to the correspondence relationship. Furthermore, although the specific method of changing the position of the far-field primary mirror 20 is not limited, an example is a method of determining in advance the correspondence relationship (mirror imaging position relationship) between the distance between the far-field primary mirror 20 and the far display area 10a, and the imaging position of the virtual image P1, and referring to the correspondence relationship. After changing the position of the far-field primary mirror 20, the process proceeds to step S12 again.

[0043] As described above, in the image projection device 100 of this embodiment, the mirror position change unit 60 changes the relative position of the primary distant mirror 20 with respect to the image display unit 10, thereby changing the imaging position of the virtual image P1 to a position closer to the host vehicle C1 than the preceding vehicle C2, thereby improving visibility.

[0044] (Modification of the first embodiment) Next, a modified example of the first embodiment of the present invention will be described. Description of contents overlapping with the first embodiment will be omitted. In the first embodiment, a mirror position change unit 60 is provided on the primary mirror 20 for far distances to change the relative position of the primary mirror 20 for far distances with respect to the image display unit 10, but a mirror position change unit 60 may also be provided on the primary mirror 30 for near distances. In this case, not only the position of the virtual image P1 of the far image but also the position of the virtual image P2 of the near image can be changed individually, and visibility can be further improved.

[0045] Second embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 5. Descriptions of contents overlapping with the first embodiment will be omitted. This embodiment differs from the first embodiment in that the emission position of the far-field image light in the far-field display area 10a is changed in conjunction with a change in the relative position of the far-field primary mirror 20 with respect to the image display unit 10. Fig. 5 is a schematic cross-sectional view for explaining an overview of an image projection device 100 according to this embodiment.

[0046] In this embodiment, in the mirror position changing step of step S15, the mirror position changing unit 60 changes the position of the far-field primary mirror 20 based on the imaging position of the virtual image P1 of the far-field image, and the control unit changes the display position of the far-field image displayed in the far-field display area 10a. In the example shown in FIG. 5, the display position of the far-field image is translated in the direction of the arrow shown in the far-field display area 10a. Although a specific method for determining the display position of the far-field image is not limited, one example is a method in which a correspondence relationship (mirror display position relationship) between the distance between the far-field primary mirror 20 and the far-field display area 10a and the display position of the far-field image in the far-field display area 10a is determined in advance, and the correspondence relationship is referred to. Here, as shown in FIG. 5, it is preferable to determine the mirror display position relationship so that the path of the far-field image light from the windshield WS to the viewpoint position is the same before and after the movement of the far-field primary mirror 20.

[0047] In the image projection device 100 of this embodiment, the mirror position change unit 60 also changes the relative position of the far-distance primary mirror 20 with respect to the image display unit 10, so that the imaging position of the virtual image P1 can be changed to a position closer to the host vehicle C1 than the leading vehicle C2, thereby improving visibility. In addition, by changing the emission position of the far-distance image light in the far-distance display area 10a in conjunction with the change in the relative position of the far-distance primary mirror 20 with respect to the image display unit 10 by the mirror position change unit 60, it becomes possible to correct the change in the line of sight when the imaging distance of the virtual image P1 is changed.

[0048] Third embodiment Next, a third embodiment of the present invention will be described with reference to Fig. 6. Descriptions of contents overlapping with the first embodiment will be omitted. This embodiment differs from the first embodiment in that when changing the relative position of the far-field primary mirror 20 with respect to the image display unit 10, the far-field primary mirror 20 is rotated in addition to being translated. Fig. 6 is a schematic cross-sectional view for explaining the outline of an image projection device 100 according to this embodiment.

[0049] As shown in FIG. 6, in this embodiment, in the mirror position changing process of step S15, the mirror position changing unit 60 translates and rotates the far-field primary mirror 20 based on the imaging position of the virtual image P1 of the far-field image. In the example shown in FIG. 6, the distance between the far-field primary mirror 20 and the far-field display area 10a is changed, and at the same time, the angle of the far-field primary mirror 20 with respect to the incident direction of the far-field image light is changed. In addition, the mirror position changing unit 60 may change the position and angle of the far-field primary mirror 20, and the control unit may change the display position of the far-field image displayed in the far-field display area 10a. Although a specific method for determining the angle of the far-field primary mirror 20 is not limited, one example is a method in which a correspondence relationship (angular imaging position relationship) between the angle of the far-field primary mirror 20 and the imaging position of the virtual image P1 is previously determined, and the correspondence relationship is referred to. In addition, the angular imaging position relationship may be determined in advance to include the above-mentioned vehicle-to-vehicle imaging position relationship, mirror imaging position relationship, and mirror display position relationship. Here, as shown in FIG. 6, the angular imaging positional relationship may be determined so that the path along which the far-distance image light travels from the windshield WS to the viewpoint position is the same before and after the far-distance primary mirror 20 is moved.

[0050] In the image projection device 100 of this embodiment, the mirror position change unit 60 also changes the relative position of the far-distance primary mirror 20 with respect to the image display unit 10, so that the imaging position of the virtual image P1 can be changed to a position closer to the host vehicle C1 than the leading vehicle C2, thereby improving visibility. Also, by changing the relative angle of the far-distance primary mirror 20, it becomes possible to correct the change in the line of sight when the imaging distance of the virtual image P1 is changed.

[0051] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described with reference to Figs. 7 to 9. Descriptions of contents overlapping with those of the first embodiment will be omitted. This embodiment differs from the third embodiment in that when changing the relative position of the primary mirror 20 for far-field use with respect to the image display unit 10, the primary mirror 20 for far-field use is rotated in addition to being translated, and the imaging position of the virtual image P1 is moved vertically to change the depression angle. Fig. 7 is a schematic diagram for explaining the imaging positions of the virtual images P1 and P2 by the image projection device 100 according to this embodiment, Fig. 7(a) shows a case where a sufficient distance between the vehicles is secured, and Fig. 7(b) shows a case where a sufficient distance between the vehicles is not secured.

[0052] In the image projection device 100 of this embodiment, as shown in Fig. 7(a), when the distance between the vehicle C1 and the vehicle in front C2 is greater than the distance between the position where the virtual image P1 is normally formed and the vehicle C1, the virtual image P1 is formed at the normal image forming position. Also, as shown in Fig. 7(a), when the distance between the vehicle C1 and the vehicle in front C2 is smaller than the distance between the position where the virtual image P1 is normally formed and the vehicle C1, the position where the virtual image P1 is formed is changed to be closer to the vehicle C1 and moved downward to change the depression angle. In Figs. 7(a) and 7(b), an example is shown in which the image forming position and depression angle of the virtual image P2 are not changed regardless of the distance between the vehicle C1 and the vehicle in front C2, but the image forming position and depression angle of the virtual image P2 may be changed.

[0053] FIG. 8 is a schematic cross-sectional view for explaining an overview of the image projection device 100 according to this embodiment. As shown in FIG. 8, in this embodiment, in the mirror position changing process of step S15, the mirror position changing unit 60 translates and rotates the far-field primary mirror 20 based on the imaging position of the virtual image P1 of the far-field image. In the example shown in FIG. 8, the distance between the far-field primary mirror 20 and the far-field display area 10a is changed, and at the same time, the angle of the far-field primary mirror 20 with respect to the incident direction of the far-field image light is changed. In addition, the mirror position changing unit 60 may change the position and angle of the far-field primary mirror 20, and the control unit may change the display position of the far-field image displayed in the far-field display area 10a.

[0054] Fig. 9 is a flowchart for explaining an image projection method using the image projection device 100 according to this embodiment. As shown in Fig. 9, the preparation step of step S21, the preceding vehicle detection step of step S22, and the inter-vehicle distance measurement step of step S23 in the image projection method according to this embodiment are the same as those in the first embodiment.

[0055] In the overlap determination step of step S24, the viewpoint position acquired in the preparation step, the vehicle distance acquired in the vehicle distance measurement step, and the distance between the imaging position of the virtual image P1 and the vehicle C1 are compared to determine whether the imaging position of the virtual image P1 overlaps with the rear end of the leading vehicle C2. If the rear end of the leading vehicle C2 overlaps with the virtual image P1, the process proceeds to step S25, and if not, the process proceeds to step S22.

[0056] Next, in the mirror position changing process of step S25, the position where the virtual image P1 of the far image is formed is determined based on the inter-vehicle distance acquired in the inter-vehicle distance measuring process, and the mirror position changing unit 60 translates and rotates the far-field primary mirror 20 based on the imaging position. The control unit may also change the display position of the far-field image displayed in the far-field display area 10a. Here, the imaging position and depression angle of the virtual image P1 are determined by the display position of the far-field image displayed in the far-field display area 10a, the distance between the far-field primary mirror 20 and the far-field display area 10a, and the angle of the far-field primary mirror 20. Therefore, the control unit determines the position and angle of the far-field primary mirror 20 and the display position of the far-field display area 10a so that the virtual image P1 does not overlap the rear end position of the leading vehicle C2. After changing the position and angle of the far-field primary mirror 20, the process proceeds to step S22 again.

[0057] As described above, in the image projection device 100 of this embodiment, the mirror position change unit 60 changes the relative position and angle of the primary distant mirror 20 with respect to the image display unit 10, and changes the display position of the distant image, thereby changing the imaging position of the virtual image P1 to a depression angle that does not overlap with the preceding vehicle C2, thereby improving visibility.

[0058] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0059] 100...Image projection device 10...Image display section 10a…Far display area 10b…Near display area 20…Primary mirror for distant objects 30…Primary mirror for near vision 40…Secondary mirror 50…Prism 60…Mirror position change section 70…Following distance acquisition unit C1…Own vehicle C2: Leading vehicle

Claims

1. An image projection device that projects image light onto a display unit for displaying a virtual image, an image display unit that irradiates the image light; a primary mirror that reflects the image light incident from the image display unit; 13. An image projection device comprising: a mirror position change unit that changes a relative position of the primary mirror with respect to the image display unit.

2. 2. The image projection device according to claim 1, The image projection device, wherein the mirror position changing unit translates the primary mirror.

3. 3. The image projection device according to claim 2, The image projection device according to claim 1, wherein the mirror position changing unit further rotates the primary mirror.

4. 2. The image projection device according to claim 1, An image projection device, comprising: a mirror position change unit that changes an emission position of the image light on the image display unit in response to an operation of the mirror position change unit.

5. 2. The image projection device according to claim 1, the image light includes near image light that forms the virtual image at a first distance and far image light that forms the virtual image at a second distance that is farther than the first distance, the primary mirror includes a near primary mirror that reflects the near image light and a far primary mirror that reflects the far image light, 2. An image projection device, comprising: a first mirror for projecting a light beam from a first light source to a second light source;

6. 6. The image projection device according to claim 5, an image projection device comprising: a secondary mirror that receives the near image light and the far image light and reflects them toward the display unit;

7. 7. The image projection device according to claim 1, A vehicle distance acquisition unit is provided for acquiring vehicle distance information, The image projection device, wherein the mirror position changing unit changes a position of the primary mirror in accordance with the following distance information.

Images