JP2023055057A - image projection device - Google Patents

Abstract

To provide an image projection device which can achieve space-saving and improvement of the design flexibility while displaying a meter or the like and projecting an auxiliary image as a virtual image.SOLUTION: An image projection device (100) for projecting a projection image (70) to a display unit (60) for displaying a virtual image comprises: an image irradiation unit (10) which irradiates an image with light; a light branching unit (20) which branches the light irradiated on the image into at least the first image light and the second image light; first optical units (31, 32) which emit the first image light via the display unit (60) in the view point direction as a projection image (70); and a second optical unit (33) which emits the second image light in the view point direction without the display unit (60).SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection device, and more particularly to an image projection device for projecting a projection image onto a display section for displaying a virtual image.

2. Description of the Related Art Conventionally, as a device for displaying various types of information in a vehicle, a dashboard that displays icons by lighting has been used. In addition, as the amount of information to be displayed increases, it has been proposed to embed an image display device in the instrument panel or to configure the entire instrument panel with an image display device.

However, since the instrument panel is located below the vehicle's windshield (windshield), it is necessary for the driver to move his or her line of sight downward while driving in order to see the information displayed on the instrument panel. I don't like it because Therefore, a head-up display (hereinafter referred to as HUD: Head Up Display) has been proposed that projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (for example, Patent Document 1). , 2).

JP 2019-119248 A JP 2019-119262 A

6A and 6B are schematic diagrams showing an information presentation method using a conventionally proposed HUD device 1. FIG. A displayed instrument image 2a is shown, and FIG. 6(c) shows an auxiliary image 3a projected as a virtual image 3. FIG. In the conventional information presentation method, a meter section 2 is installed in the vehicle separately from the HUD device 1, and the virtual image 3 is projected from the HUD device 1 through the windshield 4. FIG. Here, the meters stipulated by law are displayed in the meter section 2 as an image 2a of the meters. Also, an auxiliary image 3 a for assisting driving is projected as a virtual image 3 . In recent years, it has been proposed to use a liquid crystal display device or the like as the meter section 2 to improve the design of the gauges.

As shown in FIG. 6, while the vehicle is running, the virtual image 3 is projected several degrees (4 degrees in FIG. 6) downward from the horizontal direction. line of sight movement can be reduced. Further, by moving the line of sight further downward (20 degrees in FIG. 6), the gauges displayed on the meter section 2 can be visually recognized well. However, in the prior art, the HUD device 1 and the meter section 2 must be arranged in the instrument panel of the vehicle, so it is difficult to save space. In addition, since the position where the meter unit 2 is installed is inevitably determined at a position where the driver 5 can visually recognize it well, there is a problem that the degree of freedom in design when arranging the HUD device 1 is low.

Therefore, the present invention has been devised in view of the above-mentioned conventional problems, and it is possible to save space and improve the degree of design freedom while displaying instruments and projecting an auxiliary image as a virtual image. It is an object of the present invention to provide an image projection device that is

In order to solve the above problems, an image projection device according to the present invention is an image projection device for irradiating a projection image onto a display unit for displaying a virtual image, comprising: an image irradiating unit for irradiating an image; a light splitting unit that splits the light that irradiates the light into at least a first image light and a second image light; a first optical unit that irradiates the first image light as the projected image in a viewpoint direction through the display unit; and a second optical unit that irradiates the second image light in the viewpoint direction without passing through the display unit.

In such an image projection apparatus of the present invention, an image emitted from the image irradiation section is split into the first image light and the second image light by the light splitting section, and the first image light is transmitted to the display section by the first optical section. The second image light is emitted by the second optical section without passing through the display section. As a result, it is possible to display instruments with the second image light and project an auxiliary image (virtual image) as a projection image (virtual image) with the first image light, while achieving space saving and an improvement in design freedom. be.

Further, in one aspect of the present invention, the light branching section includes a prism arranged on a path of part of the light emitted from the image irradiation section.

Moreover, in one aspect of the present invention, the prism constitutes a part of the second optical section.

Moreover, in one aspect of the present invention, the prism constitutes a part of the first optical section.

Moreover, in one aspect of the present invention, the prism contains an infrared light absorbing material.

In one aspect of the present invention, the second optical section includes a retardation film that converts the second image light into circularly polarized light.

Moreover, in one aspect of the present invention, the second optical section includes a transmissive screen having a rear surface irradiated with the second image light.

In one aspect of the invention, the second optical section includes an enlarging optical section that magnifies and irradiates the second image light.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an image projection device capable of saving space and improving the degree of design freedom while displaying instruments and projecting an auxiliary image as a virtual image.

1 is a schematic diagram showing the configuration of an image projection device 100 according to a first embodiment; FIG. 3 is a schematic diagram showing an image irradiated from an image irradiation unit 10; FIG. 4 is a graph showing the relationship between the angle of incidence of light on the windshield 60 and reflectance. FIG. 3 is a schematic diagram showing the configuration of an image projection device 110 according to a second embodiment; FIG. 11 is a schematic diagram showing the configuration of an image projection device 120 according to a third embodiment; It is a schematic diagram showing an information presentation method using a conventionally proposed HUD device 1, FIG. 6(a) shows the device arrangement inside the vehicle, and FIG. A similar image 2a is shown, and FIG. 6(c) shows an auxiliary image 3a projected as a virtual image 3. FIG.

(First embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. FIG. 1 is a schematic diagram showing the configuration of an image projection device 100 according to this embodiment. As shown in FIG. 1, the image projection device 100 includes an image irradiation unit 10, a light branching unit 20, a reflecting mirror 31, a free-form surface mirror 32, a free-form surface mirror 33, a direct display unit 40, and an external light cutoff unit. It has a filter 50 and projects a virtual image 70 through a windshield (display unit) 60 . The image projection apparatus 100 also includes a control section (not shown) that is connected to each section so as to be able to communicate with each other and controls each section. Although the configuration of the control unit is not limited, one 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 section controls the operation of each section according to a predetermined program, and sends information (image information) including an image to the image irradiation section 10 .

The image irradiation section 10 is a section that irradiates light containing an image based on the image information from the control section. The specific configuration of the image irradiation unit 10 is not limited, and conventionally known devices such as a liquid crystal display device, an organic EL display device, and a combination of a laser light source and an optical modulation element can be used. In the example shown in FIG. 1, light is emitted from the rear side of the liquid crystal display device using a light emitting diode (LED). As will be described later, the image irradiation section 10 includes a first area 11 and a second area 12 that display a first image and a second image, respectively.

The light splitting unit 20 is an optical member that splits the image light emitted from the image irradiating unit 10 . At least the first image displayed in the first area 11 is set as the first image light, and the light is displayed in the second area 12 . The resulting second image is branched as second image light. The structure of the light splitting unit 20 is not limited as long as it is an optical member that splits light. A prism may be used, or a technique such as using a reflecting mirror to make the incident angle and the reflection angle of light different may be used. In the example shown in FIG. 1, a prism is used as the light branching section 20 and the prism is arranged to overlap the second region of the image irradiation section 10 . Therefore, the first image light emitted from the first region 11 reaches the reflecting mirror 31, and the second image light emitted from the second region 12 is free to follow a path different from that of the first image light by the light splitter 20. A curved mirror 33 is reached.

Here, arranging the light branching unit 20 so as to overlap the image irradiation unit 10 means that the area where the light branching unit 20 is arranged overlaps the image display area of the image irradiation unit 10 in plan view. In addition, both the case where the light branching unit 20 and the image irradiation unit 10 are in contact with each other and the case where they are not in contact are included in the overlapping arrangement. Also, a case in which an optical member that transmits light or a holding member that maintains the distance between the light branching unit 20 and the image irradiation unit 10 is interposed is also included in the overlapping arrangement.

The reflecting mirror 31 is an optical member that receives the first image light emitted from the image irradiation unit 10 and reflects the first image light toward the free-form surface mirror 32 . In the example shown in FIG. 1, a flat mirror is shown as the reflecting mirror 31, but it is possible to use a mirror that is optically designed to project the first image light as the virtual image 70, and if necessary A concave mirror, a convex mirror, a free-form surface mirror, or the like can be used. Alternatively, the reflecting mirror 31 may be omitted, and the first image light from the image irradiation unit 10 may directly enter the free-form surface mirror 32 .

The free-form surface mirror 32 is a concave mirror that receives the first image light reflected by the reflecting mirror 31 and reflects the first image light in the direction of the windshield 60 . The reflecting surface of the free-form surface mirror 32 is designed so that the light diameter expands in the direction of the driver's viewpoint in order to project the virtual image 70 through the windshield 60 . Here, the expansion of the light diameter in the viewing direction includes not only the case where the light diameter is consistently expanded after reflection, but also the case where the light diameter is reduced and expanded after forming an image at an intermediate point.

The free-form surface mirror 33 is an optical member that receives the second image light through the light branching section 20 and directly reflects the second image light toward the display section 40 . The free-form surface mirror 33 constitutes an enlarging optical unit that directly reaches the display unit 40 while enlarging the light diameter of the reflected second image light. The area of the second image can be displayed directly on the display unit 40 .

The direct display unit 40 is an optical member that receives the second image light reflected by the free-form surface mirror 33 and allows the driver to directly view the second image light. The configuration of the direct display unit 40 is not limited as long as the driver can visually recognize the second image light that has reached the direct display unit 40, and a sheet glass that transmits visible light, a retardation film, a transmissive screen, or the like can be used. can. When a transmissive screen is used as the direct display unit 40, the second image light irradiated to the back is diffused by the transmissive screen, so visibility is improved even when viewed through polarized glasses or viewed from an oblique direction. can be made When a retardation film is used as the direct display section 40, it is preferable to make the plane of polarization of the second image light and the first axis of the retardation film differ by a predetermined angle (typically 45 degrees). By making the first axis different from the plane of polarization, the second image light is converted into circularly polarized light and travels in the viewing direction, so visibility can be improved even when the driver wears polarized glasses.

The external light cut filter 50 is arranged on the path of the first image light between the image irradiation unit 10 and the windshield 60, and has a wavelength characteristic of blocking infrared light and/or ultraviolet light and transmitting visible light. It is an optical member having FIG. 1 shows an example in which the external light cut filter 50 is arranged between the windshield 60 and the free-form surface mirror 32. Not limited. By arranging the external light cut filter 50 , infrared light and/or ultraviolet light contained in external light such as sunlight entering from above the windshield 60 is blocked. Thereby, it is possible to suppress temperature rise and deterioration of the display surface when sunlight reaches the image display area of the image irradiation unit 10 via the free-form surface mirror 32 and the reflecting mirror 31 . In addition, since the external light cut filter 50 transmits visible light, the first image light passes well through the external light cut filter 50 and does not affect the projection of the virtual image 70 .

The windshield 60 is a member provided in front of the driver's seat of the vehicle and transmitting visible light. The windshield 60 reflects the first image light incident from the free-form surface mirror 32 on the inner surface of the vehicle in the viewing direction, and transmits light from the outside of the vehicle in the viewing direction. corresponds to the department. Although an example using the windshield 60 as the display section is shown here, a combiner may be prepared as the display section separately from the windshield 60 to reflect the light from the free-form surface mirror 32 in the direction of the viewpoint. Further, the position is not limited to the position in front of the vehicle, and may be positioned to the side or rear as long as it projects an image to the viewpoint of the passenger.

The virtual image 70 is an image that is displayed as if it were formed in space when the first image light reflected by the windshield 60 reaches the visual point (eye box) of the driver or the like. The position where the virtual image 70 is formed is determined by the spread angle when the light irradiated from the image irradiation unit 10 travels in the direction of the viewpoint after being reflected by the reflecting mirror 31, the free-form surface mirror 32, and the windshield 60. .

In the example shown in FIG. 1, the combination of the reflecting mirror 31, the free-form surface mirror 32 and the external light cut filter 50 constitutes the first optical section in the present invention. Image light is emitted in the direction of the viewpoint as a projection image. The combination of the light splitter 20, the free-form surface mirror 33, and the direct display unit 40 constitutes the second optical unit of the present invention. to irradiate. A convex lens or a concave lens may be arranged in the first optical section or the second optical section as necessary to enlarge or reduce the light diameter.

FIG. 2 is a schematic diagram showing an image irradiated from the image irradiation section 10. As shown in FIG. The first image is displayed in the first area 11 and the second image is displayed in the second area 12 of the entire image display area of the image irradiation unit 10 . In the example shown in FIG. 2, the first image displayed in the first area 11 presents supplementary information regarding driving such as a speed and volume indicator and a traveling direction guide. Also, as a second image displayed in the second area 12, a speedometer, a car navigation screen, and instruments such as driving mode information are presented.

In the image projection apparatus 100 shown in FIG. 1, a prism, which is the light branching unit 20, is arranged at a position overlapping the second area 12, and the first image light from the first area 11 and the second image from the second area 12 are arranged. It splits the path of light. The first image displayed in the first area 11 reaches the driver's viewpoint via the reflecting mirror 31 , the free-form surface mirror 32 , the external light cut filter 50 and the windshield 60 . As described above, since the first image light travels with its light diameter expanding in the direction of the viewpoint, the driver visually recognizes that the virtual image 70 is displayed as a projection image farther than the windshield 60 . Also, the second image displayed in the second area 12 reaches the driver's viewpoint via the light branching section 20 , the free-form surface mirror 33 and the direct display section 40 . Thereby, the driver visually recognizes that the second image is displayed on the direct display unit 40 .

FIG. 3 is a graph showing the relationship between the angle of incidence of light on the windshield 60 and reflectance. The horizontal axis of FIG. 3 indicates the incident angle of light on the windshield 60, and the vertical axis indicates the relative reflectance when the incident angle of 90 degrees is 100%. The solid and dashed lines in the figure indicate theoretical values for P-polarized light and S-polarized light, respectively, and the plotted white circles and black circles indicate measured values for P-polarized light and S-polarized light, respectively. As shown in FIG. 3, the reflectance of P-polarized light drops significantly when the angle of incidence on the windshield 60 is around 60 degrees. is preferably placed.

When the free-form surface mirror 32 is arranged so that the incident angle of the first image light to the windshield 60 is 55 degrees or less or 65 degrees or more, the reflected light has a high proportion of P-polarized light as shown in FIG. Become. Accordingly, even when the driver wears polarizing glasses and cuts S-polarized light with the polarizing glasses, the virtual image 70 projected by the first image light can be visually recognized.

As described above, in the image projection apparatus of the present invention, the image projected from the image irradiation unit 10 is split into the first image light and the second image light by the light splitting unit 20, and the first image light is split by the first optical unit. The light is emitted through the windshield 60 and the second image light is emitted by the second optical section without the windshield 60 . As a result, the first image and the second image can be displayed by one image irradiation unit 10, and space can be saved and the degree of freedom in design can be improved. Since the second image light is directly displayed while projecting the virtual image 70 with the first image light, the instruments are displayed with the second image light, and the auxiliary image is the projection image (virtual image) of the first image light. It is possible to save space and improve the degree of freedom in design while projecting with .

In addition, by using a prism as the light branching section 20, the optical design for partially covering the image irradiation section 10 and branching a portion of the light is facilitated. In addition, compared to the case of using a reflecting mirror to split light, the use of a prism as the light splitting unit 20 reduces the volume to be secured for splitting the light, thereby miniaturizing the device. can. In particular, when the light branching unit 20 is arranged so as to overlap the second region 12, the area ratio of the second region 12 to the image irradiation unit 10 is larger than that of the first region 11. It is advantageous for miniaturization using a prism. In addition, although chromatic aberration occurs when a lens or prism is used, the chromatic aberration of the prism has a high degree of regularity with the angle as a parameter.

(Second embodiment)
Next, a second embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 4 is a schematic diagram showing the configuration of the image projection device 110 according to this embodiment. This embodiment differs from the first embodiment in that the light branching section 20 is included in the first optical section.

As shown in FIG. 4, the image projection device 110 includes an image irradiation unit 10, a light branching unit 20, a reflecting mirror 31, a free-form surface mirror 32, a free-form surface mirror 33, and a direct display unit 40. A virtual image 70 is projected through a windshield (display unit) 60 . In this embodiment, the light branching unit 20 is arranged between the image irradiation unit 10 and the reflecting mirror 31, the light branching unit 20 is composed of a prism, and the material constituting the prism contains an infrared light absorbing material. I am letting

In the example shown in FIG. 4, the combination of the light branching section 20, the reflecting mirror 31 and the free-form surface mirror 32 constitutes the first optical section in the present invention. Light is emitted as a projected image in the direction of the viewpoint. Also, the combination of the free-form surface mirror 33 and the direct display section 40 constitutes the second optical section of the present invention, which irradiates the second image light in the viewing direction without passing through the windshield (display section) 60 .

In the image projection device 110 shown in FIG. 4, a prism, which is the light branching unit 20, is arranged at a position overlapping the first area 11, and the first image light from the first area 11 and the second image from the second area 12 are projected. It splits the path of light. The first image displayed in the first area 11 reaches the driver's viewpoint via the light splitter 20 , the reflecting mirror 31 , the free-form surface mirror 32 and the windshield 60 . As described above, since the first image light travels with its light diameter expanding in the direction of the viewpoint, the driver visually recognizes that the virtual image 70 is displayed as a projection image farther than the windshield 60 . Also, the second image displayed in the second area 12 reaches the driver's viewpoint via the free-form surface mirror 33 and the direct display unit 40 . Thereby, the driver visually recognizes that the second image is displayed on the direct display unit 40 .

The prism constituting the light branching section 20 is made of resin or glass that transmits visible light and has a high refractive index as a base material, and the base material contains an infrared light absorbing material that absorbs infrared light. contained. Further, the light branching portion 20 may contain an ultraviolet light absorbing material. As a result, the infrared light and/or ultraviolet light contained in external light such as sunlight entering from above the windshield 60 is can be blocked, and the temperature rise of the image irradiation unit 10 can be suppressed.

Also in the image projection device 110 of this embodiment, the image projected from the image irradiation unit 10 is split into the first image light and the second image light by the light splitting unit 20, and the first image light is windshielded by the first optical unit. 60 , and the second image light is emitted by the second optical section without passing through the windshield 60 . As a result, it is possible to display instruments with the second image light and project an auxiliary image (virtual image) as a projection image (virtual image) with the first image light, while achieving space saving and an improvement in design freedom. be.

(Third embodiment)
Next, a third embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 5 is a schematic diagram showing the configuration of the image projection device 120 according to this embodiment. This embodiment differs from the first embodiment in that a plurality of optical branching units 20 are provided.

As shown in FIG. 5, the image projection device 120 includes an image irradiation unit 10, light branching units 20a and 20b, a reflector 31, a free-form surface mirror 32, a free-form surface mirror 33, a reflector 34, and a free-form surface. It has a mirror 35 , a direct display section 40 and an external light cut filter 50 , and projects virtual images 70 a and 70 b through a windshield (display section) 60 . In this embodiment, in the display area of the image irradiation unit 10, the first area 11 displays the first image, the second area 12 displays the second image, and the third area displays the third image.

The light branching units 20 a and 20 b are optical members that branch the image light emitted from the image irradiation unit 10 . In the example shown in FIG. 5, prisms are used as the light branching units 20a and 20b, and the prisms are arranged to overlap the second region 12 and the third region of the image irradiation unit 10, respectively. The reflecting mirror 34 is an optical member that receives the third image light emitted from the image irradiation unit 10 and reflects the third image light toward the free-form surface mirror 35 . The free-form surface mirror 35 is a concave mirror that receives the third image light reflected by the reflecting mirror 34 and reflects the third image light in the direction of the windshield 60 . The reflecting surface of the free-form surface mirror 35 is designed so that the light diameter expands in the direction of the driver's viewpoint in order to project the virtual image 70b through the windshield 60 .

In the example shown in FIG. 5, the combination of the reflecting mirror 31, the free-form surface mirror 32 and the external light cut filter 50 constitutes the first optical section in the present invention. Image light is emitted in the direction of the viewpoint as a projection image. Also, the combination of the light branching portion 20a, the free-form surface mirror 33, and the direct display portion 40 constitutes the second optical portion of the present invention, and the second image light is projected in the direction of the viewpoint without passing through the windshield (display portion) 60. to irradiate. The combination of the light branching portion 20b, the reflecting mirror 31, the free-form surface mirror 32, and the external light cut filter 50 constitutes the third optical portion of the present invention. Light is emitted as a projected image in the direction of the viewpoint. Although an example in which the free-form surface mirror 32 and the free-form surface mirror 35 are formed separately is shown here, a free-form surface mirror formed by integrally forming two free-form surface surfaces may be used.

In the image projection device 120 shown in FIG. 5, prisms serving as the light branching units 20a and 20b are arranged at positions overlapping the second region 12 and the third region, respectively, and the first image light from the first region 11 and the second The paths of the second image light from the region 12 and the third image light from the third region are branched. The first image displayed in the first area 11 reaches the driver's viewpoint via the reflecting mirror 31 , the free-form surface mirror 32 , the external light cut filter 50 and the windshield 60 . Also, the second image displayed in the second area 12 reaches the driver's viewpoint via the light splitter 20a, the free-form surface mirror 33, and the direct display 40. FIG. Thereby, the driver visually recognizes that the second image is displayed on the direct display unit 40 . Also, the third image displayed in the third area reaches the driver's viewpoint via the light branching portion 20b, the reflecting mirror 34, the free-form surface mirror 35, the external light cut filter 50, and the windshield 60. As described above, since the first image light and the third image light travel with their light diameters enlarged in the direction of the viewpoint, the driver will perceive that the virtual images 70a and 70b are displayed as projection images farther than the windshield 60. Visualize.

In the image projection device 120 of the present embodiment as well, the image irradiated from the image irradiation unit 10 is branched into the first image light, the second image light and the third image light by the light branching units 20a and 20b. The third image light is irradiated through the windshield 60 by the first optical section and the third optical section, respectively, and the second image light is irradiated by the second optical section without the windshield 60 . As a result, while displaying instruments with the second image light and projecting an auxiliary image as a projection image (virtual image) with the first image light and the third image light, it is possible to save space and improve the degree of freedom in design. It is possible to plan

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

100, 110, 120... Image projection device 10... Image irradiation unit 11... First area 12... Second area 20, 20a, 20b... Light branching parts 31, 34... Reflecting mirrors 32, 33, 35... Free curved surface mirror 40... Direct display unit 50 External light cut filter 60 Windshield 70, 70a, 70b Virtual image

Claims (8)

An image projection device for projecting a projection image onto a display unit for displaying a virtual image,
an image irradiation unit that irradiates an image;
a light splitting unit that splits the light for irradiating the image into at least first image light and second image light;
a first optical unit that irradiates the first image light as the projected image in a viewpoint direction through the display unit;
and a second optical unit that irradiates the second image light in the viewpoint direction without passing through the display unit. The image projection device according to claim 1,
The image projection apparatus according to claim 1, wherein the light branching section includes a prism arranged on a path of part of the light emitted from the image irradiation section. The image projection device according to claim 2,
The image projection device, wherein the prism constitutes a part of the second optical section. The image projection device according to claim 2,
The image projection device, wherein the prism constitutes a part of the first optical section. The image projection device according to claim 4,
The image projection apparatus, wherein the prism contains an infrared light absorbing material. The image projection device according to any one of claims 1 to 5,
The image projection device, wherein the second optical unit includes a retardation film that converts the second image light into circularly polarized light. The image projection device according to any one of claims 1 to 5,
The image projection device, wherein the second optical unit has a transmissive screen on the rear surface of which the second image light is irradiated. The image projection device according to any one of claims 1 to 7,
The image projection device, wherein the second optical section includes an enlarging optical section that magnifies and irradiates the second image light.

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