Image Projection Device

Abstract

To provide an image projection device with which, even when irradiation light from an image irradiation unit is reflected by a plurality of free-form surface mirrors and reaches a viewpoint, it is possible to effectively utilize an empty space and achieve space-saving.SOLUTION: Provided is an image projection device comprising: an image irradiation unit (10) for radiating irradiation light that includes an image; a first free-form surface mirror (20) for reflecting irradiation light that enters from the image irradiation unit (10); a second free-form surface mirror (30) for reflecting irradiation light that enters from the first free-form mirror (20) and letting it reach a viewpoint (50). The irradiation light reflected by the first free-form surface mirror (20) is formed into an image for only one of its x-axis and y-axis components, between the first free-form surface mirror (20) and the second free-form surface mirror (30).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image projection device, and more particularly to an image projection device in which light emitted from an image projection unit is reflected by a plurality of free-form surface mirrors to reach a viewpoint. [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 vehicle's windshield, the driver must move his or her eyes downward while driving in order to visually confirm the information displayed on the instrument panel, 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 the driver can read information when viewing the area ahead of the vehicle (see, for example, Patent Document 1).

[0004] In such a conventional image projection device, the image projection unit irradiates irradiation light containing an image, and the irradiation light is reflected by one or more free-form surface mirrors so that the image reaches the viewpoint of the driver, etc., so that the image is formed in space. This allows the driver, etc., 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 2019-119262 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional image projection devices, it is necessary to arrange multiple free-form surface mirrors so as to face each other alternately, and it is necessary to secure space so that components such as the image projection unit do not block the light reflected by the free-form surface mirrors, making it difficult to save space. In addition, if the size of the free-form surface mirror is reduced in order to save space, there is a problem that the curvature of the free-form surface mirror increases, resulting in large aberrations.

[0007] Therefore, the present invention has been made in consideration of the above-mentioned conventional problems, and has an object to provide an image projection device that can effectively utilize space and save space, even if the irradiation light from an image irradiation unit is reflected by multiple free-form surface mirrors to reach the viewpoint. [Means for solving the problem]

[0008] In order to solve the above problem, the image projection device of the present invention comprises an image irradiation unit that irradiates irradiation light including an image, a first free-form surface mirror that reflects the irradiation light incident from the image irradiation unit, and a second free-form surface mirror that reflects the irradiation light incident from the first free-form surface mirror to reach a viewpoint, wherein when an optical path of the irradiation light from the image irradiation unit to the viewpoint is defined as a reference ray, a reflection direction of the reference ray on the first free-form surface mirror is defined as a z-axis, a direction perpendicular to the z-axis in a plane including the reference ray and the z-axis on the second free-form surface mirror is defined as a y-axis, and a direction perpendicular to the y-axis and the z-axis is defined as an x-axis, the irradiation light reflected by the first free-form surface mirror is imaged between the first free-form surface mirror and the second free-form surface mirror.

[0009] In the image projection device of the present invention, the first free-form surface mirror images only one of the x-axis component or the y-axis component of the irradiated light between the first free-form surface mirror and the second free-form surface mirror, thereby securing space for placing optical components in the space between the first free-form surface mirror and the second free-form surface mirror, thereby making effective use of the space and achieving space savings.

[0010] In one aspect of the present invention, the y-axis component is imaged between the first free-form curved mirror and the second free-form curved mirror.

[0011] In one aspect of the present invention, the image forming position of the irradiation light reflected by the second free-form surface mirror is the same for the x-axis component and the y-axis component. In one aspect of the present invention, the image irradiating unit is disposed between the first free-form curved mirror and the second free-form curved mirror at a position avoiding a region through which the irradiating light propagates.

[0012] In addition, in one aspect of the present invention, a transmissive reflector is provided that reflects the illumination light from the second free-form curved mirror that is incident on one surface in the direction of the viewpoint, and transmits external light that is incident on the other surface in the direction of the viewpoint.

[0013] In one aspect of the present invention, the transmissive reflective portion is a windshield of a vehicle. Effect of the Invention

[0014] The present invention can provide an image projection device that can effectively utilize space and save space, even if the light emitted from the image irradiation unit is reflected by multiple free-form surface mirrors to reach the viewpoint. [Brief description of the drawings]

[0015] [Figure 1] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a configuration of an image projection device according to a first embodiment of the present invention, FIG. 1(a) being a schematic top view, and FIG. 1(b) being a schematic side view. [Diagram 2] 2 is a schematic diagram showing the arrangement of optical members and a reference light ray in the image projector according to the first embodiment. FIG. [Diagram 3] 3A and 3B are schematic diagrams showing reference rays and local coordinates in a free-form surface mirror, with FIG. 3A showing the free-form surface mirror 20 and FIG. 3B showing the free-form surface mirror 30. FIG. [Figure 4] 4A and 4B are schematic diagrams showing the arrangement of an image projection unit 10 and free-form surface mirrors 20 and 30 in the first embodiment, with FIG. 4A being a schematic side view and FIG. 4B being a schematic top view. [Diagram 5] 5A and 5B are schematic diagrams showing the arrangement of an image projection unit 10 and free-form surface mirrors 20 and 30 in a second embodiment, with FIG. 5A being a schematic side view and FIG. 5B being a schematic top view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (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 are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. FIG. 1 is a schematic diagram showing the configuration of an image projection device according to this embodiment, FIG. 1(a) is a schematic top view, and FIG. 1(b) is a schematic side view. As shown in FIG. 1, the image projection device includes an image projection unit 10, free-form surface mirrors 20 and 30, and a windshield 40, and allows a virtual image 60 to be viewed from a viewpoint 50 through the windshield 40.

[0017] The image projection unit 10 is a device that projects light containing image information when a signal containing image information is supplied from an information processing unit (not shown). The light projected from the image projection unit 10 is incident on a free-form surface mirror 20. Examples of the image projection unit 10 include a liquid crystal display device, an organic EL display device, a micro LED display device, and a projector device using a laser light source.

[0018] The free-form surface mirror 20 is a concave mirror onto which the illumination light emitted from the image illumination unit 10 is incident and reflected in the direction of the free-form surface mirror 30, and corresponds to the first free-form surface mirror in the present invention. The reflective surface of the free-form surface mirror 20 has different focal lengths for the x-axis component and the y-axis component in the plane, as described below, and is set so that only one of the x-axis component or the y-axis component forms an intermediate image before reaching the free-form surface mirror 30.

[0019] The free-form surface mirror 30 is a concave mirror onto which the irradiated light reflected by the free-form surface mirror 20 is incident and which reflects it in the direction of the windshield 40, and corresponds to the second free-form surface mirror in the present invention. The reflective surface of the free-form surface mirror 30 also has different focal lengths for the x-axis component and the y-axis component in the plane, and is set so that the x-axis component and the y-axis component of the irradiated light are imaged at the same position after being reflected by the free-form surface mirror 30.

[0020] The windshield 40 is provided in front of the driver's seat of the vehicle, and has a function as an optical member that reflects the irradiated light incident from the free-form surface mirror 30 toward the viewpoint 50 on the inner surface of the vehicle and transmits the light from the outside of the vehicle toward the viewpoint 50. Therefore, the windshield 40 corresponds to the transmission reflection part in the present invention. Here, an example is shown in which the windshield 40 is used as the transmission reflection part, but a combiner may be prepared as the transmission reflection part separately from the windshield 40 and reflect the light from the free-form surface mirror 30 toward the viewpoint 50. In addition, the windshield 40 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 50 of the passenger.

[0021] The viewpoint 50 is the eye (eyebox) of the driver or passenger of the vehicle, and the driver or passenger views the formed virtual image 60 as the irradiated light enters the eyebox and reaches the retina.

[0022] The virtual image 60 is displayed as if it were formed in space when the irradiated light reflected by the windshield 40 reaches the viewpoint (eyebox) 50 of the driver or the like. The position at which the virtual image 60 is formed is determined by the spread angle of the light irradiated from the image irradiating unit 10 as it travels toward the viewpoint 50 after being reflected by the free-form surface mirror 20 and the free-form surface mirror 30. As shown in Figs. 1(a) and (b), the irradiated light reflected by the free-form surface mirror 30 reaches the viewpoint 50 while the light beam is expanding after being reflected by the windshield 40.

[0023] At this time, the driver or passenger at viewpoint 50 recognizes that virtual image 60 exists at an imaging position farther away than windshield 40. Here, the imaging position of virtual image 60 depends mainly on the composite focal length of free-form surface mirror 20 and free-form surface mirror 30. Even if windshield 40 is curved rather than a flat surface, the radius of curvature is larger than that of free-form surface mirror 20 and free-form surface mirror 30, so the effect of the optical power of windshield 40 is negligible.

[0024] FIG. 2 is a schematic diagram showing the arrangement of optical members and a reference ray in the image projection device of the embodiment. As shown in FIG. 2, the light emitted from the image projection unit 10 is reflected by the free-form surface mirrors 20 and 30 and the windshield 40 and reaches the viewpoint 50. At this time, the trajectory of the light reaching the viewpoint 50 from the direction in which the virtual image 60 is viewed is taken as the reference ray, and is shown by a broken line in FIG. 2. In other words, this reference ray can be considered to be substantially the same as the trajectory of the light emitted from the center of the effective area from which the light is emitted in the image projection unit 10 when it reaches the viewpoint 50. The actual irradiation light is light that is irradiated from the image projection unit 10 with a predetermined area, and the light beam spreads from each position on the display surface, and is condensed with positive power by the reflecting surfaces of the free-form surface mirrors 20 and 30. Therefore, the reference ray shown in FIG. 2 does not show the path along which the irradiation light in the entire area of ​​the image projection unit 10 travels. Also, the distance from the free-form surface mirror 20 to the free-form surface mirror 30 along the reference ray is defined as D.

[0025] Fig. 3 is a schematic diagram showing reference rays and local coordinates in a free-form surface mirror, with Fig. 3(a) showing the free-form surface mirror 20 and Fig. 3(b) showing the free-form surface mirror 30. The dashed lines shown in Fig. 3(a) and (b) are reference rays of the irradiated light shown by the dashed lines in Fig. 2. In addition, of the reference rays, the direction in which the irradiated light is incident on the free-form surface mirror 20 and the free-form surface mirror 30 is referred to as the incident ray, and the direction in which it is reflected is referred to as the reflected ray.

[0026] As shown in FIGS. 3(a) and 3(b), the reflection direction of the reference ray on the free-form mirror 20 is defined as the z-axis. Also, in the plane including the reflection direction of the reference ray on the free-form mirror 30 and the z-axis, the direction perpendicular to the z-axis is defined as the y-axis. Further, the direction perpendicular to the y-axis and the z-axis is defined as the x-axis.

[0027] The free-form mirror 20 has a surface with different curvatures in the x-axis direction and the y-axis direction. The reflected irradiation light is focused at different focal lengths in the x-axis component and the y-axis component, and only one of the x-axis component or the y-axis component is intermediate-imaged between the free-form mirror 20 and the free-form mirror 30. In the example shown in FIG. 1, the substantially horizontal direction of the vehicle is the x-axis direction, and the substantially vertical direction is the y-axis. Therefore, only one of the x-axis component, which is the horizontal direction of the vehicle, or the y-axis component, which is the vertical direction, is intermediate-imaged.

[0028] Here, when parallel light is incident on the free-form mirror 20 from the image irradiation unit 10, if the distance from the light that has received the positive power by the free-form mirror 20 to the position where the light forms a focus is defined as the focal length f1, the focal length in the x-axis component is fx1, and the focal length in the y-axis component is fy1. Thus, when compared with the distance D between the free-form mirror 20 and the free-form mirror 30 along the reference ray, the relational expression 0 < fy1 ≦ D ≦ fx1 or 0 < fx1 ≦ D ≦ fy1 is satisfied.

[0029] Similarly, the free-form mirror 30 also has a surface with different curvatures in the x-axis direction and the y-axis direction, and the reflected irradiation light has different focal lengths in the x-axis component and the y-axis component. Here, when parallel light is incident on the free-form mirror 30, if the distance from the light that has received the positive power by the free-form mirror 30 to the position where the light forms a focus is defined as the focal length f2, the focal length in the x-axis component is fx2, and the focal length in the y-axis component is fy2.

[0030] As described above, the focal length fx1 and the focal length fy1 in the free-form surface mirror 20 are set so that only one of them forms an intermediate image between the free-form surface mirror 20 and the free-form surface mirror 30. The focal length fx2 and the focal length fy2 in the free-form surface mirror 30 are set so that the irradiated light reflected by the free-form surface mirror 30 is imaged at the same position in the x-axis component and the y-axis component. As a result, the virtual image 60 viewed at the viewpoint 50 is imaged at the same position in the x-axis component and the y-axis component, and the virtual image 60 can be appropriately recognized as an image existing at the image formation position. In addition, by appropriately setting the curved surface shape of the free-form surface mirror 30, it is also possible to correct aberrations occurring in the irradiated light reflected by the free-form surface mirror 20.

[0031] Fig. 4 is a schematic diagram showing the arrangement of the image projection unit 10 and the free-form surface mirrors 20 and 30 in this embodiment, Fig. 4(a) is a schematic side view, and Fig. 4(b) is a schematic top view. As shown in Fig. 4(a) and (b), in this embodiment, the y-axis component of the irradiation light reflected by the free-form surface mirror 20 is imaged at a position f between the free-form surface mirror 20 and the free-form surface mirror 30, and the x-axis component is not imaged.

[0032] Therefore, as shown by the dashed line in Fig. 4(a), the irradiation light irradiated from the entire display surface of the image irradiation unit 10 is reflected by the free-form surface mirror 20 and then focused at position f in the y-axis direction, and there is a space for arranging an optical member in the space in the y-axis direction between the free-form surface mirror 20 and the free-form surface mirror 30. This makes it possible to arrange the image irradiation unit 10 at a position that avoids the area where the irradiation light propagates between the free-form surface mirror 20 and the free-form surface mirror 30. Also, as shown in Fig. 4(a), by partially inserting the image irradiation unit 10 between the free-form surface mirror 20 and the free-form surface mirror 30, it is possible to effectively utilize the space and achieve space saving.

[0033] If an image projection device were to intermediately image both the x-axis component and the y-axis component of the irradiated light, aberration would increase in both the x-axis component and the y-axis component, making it more difficult to correct the aberration with the free-form surface mirror 30. Furthermore, in order to intermediately image both the x-axis component and the y-axis component, it is necessary to reduce the radii of curvature of the free-form surface mirror 20 in the x-axis and y-axis directions, which increases the displacement in the thickness direction of the free-form surface mirror 20, making it difficult to miniaturize the image projection device.

[0034] In contrast, in this embodiment, an intermediate image is formed of only either the x-axis component or the y-axis component of the irradiated light between the free-form surface mirror 20 and the free-form surface mirror 30. As a result, with regard to the aberration caused by the positive power of the free-form surface mirror 20, only either the x-axis component or the y-axis component becomes large, and the optical design for correcting the aberration with the free-form surface mirror 30 becomes simple. In addition, since the radius of curvature of the free-form surface mirror 20 can be increased in the x-axis or y-axis direction, the displacement in the thickness direction of the free-form surface mirror 20 can be reduced, thereby enabling the image projection device to be made more compact.

[0035] 4(b), in this embodiment, the image projection unit 10 and the free-form surface mirror 20 are arranged so that their central positions in the x-axis direction are approximately aligned, and the reference ray of the projection light has a path only within the yz plane, with no displacement in the x-axis direction. This makes it possible to reduce the aberration of the x-axis component in the free-form surface mirror 20. In addition, the reference ray from the free-form surface mirror 30 to the windshield 40 also has a path only within the yz plane, and it is only necessary to consider the displacement of the y-axis component, making it easy to correct the aberration.

[0036] As described above, in the image projection device of this embodiment, the free-form surface mirror 20 forms an image of only either the x-axis component or the y-axis component of the irradiated light between the free-form surface mirror 20 and the free-form surface mirror 30, so that a space for arranging an optical member can be secured in the space between the free-form surface mirror 20 and the free-form surface mirror 30, and it is possible to effectively use the space and achieve space saving. In addition, it becomes easier to correct aberrations in the image projection device, and it is also possible to achieve a compact design.

[0037] 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. Fig. 5 is a schematic diagram showing the arrangement of the image projection unit 10 and the free curved surface mirrors 20 and 30 in this embodiment, Fig. 5(a) is a schematic side view, and Fig. 5(b) is a schematic top view.

[0038] As shown in Figures 5(a) and (b), in this embodiment, the illumination light reflected by the free-form surface mirror 20 is imaged at position f between the free-form surface mirror 20 and the free-form surface mirror 30 in terms of its x-axis component and its y-axis component.

[0039] Therefore, as shown by the dashed line in Fig. 5(a), the irradiation light irradiated from the entire display surface of the image irradiation unit 10 is reflected by the free-form surface mirror 20 and then focused at position f in the x-axis direction, and there is a space for arranging an optical member in the space in the x-axis direction between the free-form surface mirror 20 and the free-form surface mirror 30. This makes it possible to arrange the image irradiation unit 10 at a position between the free-form surface mirror 20 and the free-form surface mirror 30 that avoids the area where the irradiation light propagates. Also, as shown in Fig. 5(b), by partially inserting the image irradiation unit 10 between the free-form surface mirror 20 and the free-form surface mirror 30, it is possible to effectively utilize the space and achieve space saving.

[0040] In this embodiment, the reference ray is displaced in the x-axis direction from image projection unit 10 to free-form surface mirror 20, but is not displaced in the x-axis direction from free-form surface mirror 20 to free-form surface mirror 30, windshield 40, and viewpoint 50. Therefore, it is more difficult to correct the aberration of the x-axis component at free-form surface mirror 30 than in the first embodiment, but since image projection devices generally often project horizontally long images, it is possible to increase the space that can be secured between free-form surface mirror 20 and free-form surface mirror 30.

[0041] 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]

[0042] 10...Image irradiation unit 20,30…Freeform mirror 40…Windshield 50… Viewpoint 60...Virtual Image

Claims

1. an image projection unit that projects light including an image, a first free-form curved mirror that reflects the light incident from the image projection unit, and a second free-form curved mirror that reflects the light incident from the first free-form curved mirror to reach a viewpoint; A light path of the irradiation light from the image irradiation unit to the viewpoint is defined as a reference light ray, A reflection direction of the reference light beam on the first free-form surface mirror is defined as a z-axis, a direction perpendicular to the z-axis in a plane including the reference ray and the z-axis on the second free-form curved mirror is defined as a y-axis; When the direction perpendicular to the y-axis and the z-axis is the x-axis, an x-axis component or a y-axis component of the illumination light reflected by the first free-form surface mirror is focused into an image between the first free-form surface mirror and the second free-form surface mirror,

2. 2. The image projection device according to claim 1, an image projection device, wherein the y-axis component is imaged between the first free-form surface mirror and the second free-form surface mirror;

3. 3. The image projection device according to claim 1, an imaging position of the irradiation light reflected by the second free-form surface mirror being the same for the x-axis component and the y-axis component;

4. 4. The image projection device according to claim 1, an image projection device, characterized in that the image irradiation unit is disposed between the first free-form curved mirror and the second free-form curved mirror at a position avoiding a region through which the irradiation light propagates;

5. 5. The image projection device according to claim 1, An image projection device comprising a transmission / reflection section that reflects the illumination light from the second free-form surface mirror that is incident on one surface toward the direction of the viewpoint, and transmits external light that is incident on the other surface toward the direction of the viewpoint.

6. 6. The image projection device according to claim 5, 11. An image projection device, wherein the transmission / reflection portion is a windshield of a vehicle.

Images