Image projection device

Abstract

To provide an image projection device which suppresses stray light of external light so as to be able to improve the visibility of a virtual image.SOLUTION: An image projection device (100) which projects image light to a display part for displaying a virtual image includes: an image display part (10) for applying the image light; and a primary mirror (20) for reflecting the image light incident from the image display part (10). An optical path at the center of the image light between the image display part (10) and the primary mirror (20) is set as a reference line (LC). A direction vertical to a display surface of the image display part (10) is set as a normal direction (NV). The reference line (LC) differs from the normal direction (NV).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 that projects a projection image onto a display unit for displaying a virtual image. [Background technology]

[0002] Conventionally, dashboards that illuminate icons have been used to display various types of information inside vehicles. 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 their eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, a head-up display (hereinafter referred to as HUD) has been proposed, which projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-119248 [Patent Document 2] Japanese Patent Application Publication No. 2019-119262 Summary of the Invention [Problem to be solved by the invention]

[0005] In such conventional HUD devices, a projection image is projected through the windshield, which serves as the display unit, and light is projected upward from below the windshield. Therefore, when external light, such as sunlight, enters from above the windshield, the external light reaches the image projection unit that displays the image via the projection optical system. In this case, some of the external light that reaches the image display unit is reflected and becomes stray light, which then reaches the viewpoint via the projection optical system and the windshield, potentially reducing the visibility of the virtual image.

[0006] 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 suppress stray light from outside and improve the visibility of virtual images. [Means for solving the problem]

[0007] In order to solve the above problem, 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 equipped with 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 characterized in that the central optical path of the image light between the image display unit and the primary mirror is defined as a reference line, the direction perpendicular to the display surface of the image display unit is defined as a normal direction, and the reference line and the normal direction are different.

[0008] In the image projection device of the present invention, the reference line of the image light between the image display unit and the primary mirror is made different from the normal direction of the image display unit, thereby reducing the possibility that external light reaching the image display unit will be reflected back to the viewpoint, suppressing stray external light, and improving the visibility of the virtual image.

[0009] In one aspect of the present invention, the normal direction faces outward from the reflecting surface of the primary mirror.

[0010] In addition, one aspect of the present invention is provided with a secondary mirror onto which the image light reflected by the primary mirror is incident and reflected, and the image light is intermediately imaged in the height direction between the primary mirror and the secondary mirror.

[0011] In one aspect of the present invention, an intermediate mask having an opening is disposed between the primary mirror and the secondary mirror, and the image light passes through the opening.

[0012] In one aspect of the present invention, the normal direction is directed toward a direction other than the opening of the intermediate mask.

[0013] In addition, in one aspect of the present invention, a circuit board that controls the image display unit and a cable that electrically connects the image display unit and the circuit board are provided, and the circuit board is arranged on the back side of the secondary mirror. [Effects of the Invention]

[0014] The present invention can provide an image projection device that can suppress stray external light and improve the visibility of a virtual image. [Brief explanation of the drawings]

[0015] [Figure 1] 2 is a schematic diagram showing the projection of a virtual image P by the image projection device 100 according to the first embodiment. FIG. [Figure 2] 1 is a schematic diagram illustrating an example of the structure of an image projection device 100 according to a first embodiment. [Figure 3] FIG. 10 is a schematic diagram showing an example of the structure of an image projection device 100 according to a second embodiment. [Figure 4] FIG. 10 is a schematic diagram showing an example of the structure of an image projection device 100 according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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 will be denoted by the same reference numerals, and redundant explanations will be omitted where appropriate. Fig. 1 is a schematic diagram showing the projection of a virtual image P by an image projection device 100 according to this embodiment.

[0017] 1, image light projected from image projection device 100 is irradiated onto a driver's viewpoint E via a windshield WS (display unit), and a virtual image P is formed at a predetermined distance from the windshield WS. Image projection device 100 is a device for irradiating a projection image onto a display unit and displaying virtual image P to the driver, etc. The configuration of image projection device 100 will be described later.

[0018] The windshield WS is a part of the vehicle that is provided in front of the driver's seat and transmits visible light. The windshield WS corresponds to the display unit of the present invention because, on the inside surface of the vehicle, it reflects the image light incident from the image projection device 100 toward the viewpoint E and transmits light from outside the vehicle toward the viewpoint E. Although an example in which the windshield WS is used as the display unit is shown here, a combiner may be provided as a display unit separate from the windshield WS and reflect light from the image projection device 100 toward the viewpoint. Furthermore, the display unit is not limited to being located at the 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.

[0019] The virtual image P is an image that appears as if it were formed in space when the image light reflected by the windshield WS reaches the viewpoint (eyebox) of the driver or the like. The position at which the virtual image P is formed is determined by the optical path length of the image light emitted from the image projection device 100 and the spread angle when it travels toward the viewpoint after being reflected by the windshield WS. Examples of images that may be formed as the virtual image P include auxiliary information related to driving, such as speed and volume indicators, driving direction guides, cautionary images, and emergency information.

[0020] In the figure, the path of the image light is indicated by a reference line L C,Top line L U ,bottom line L B The reference line L C is the path of the image light at the center position in the width direction and height direction in the area where the virtual image P can be displayed. In FIG. 1, a reference line L runs from the viewpoint position E to the position of the virtual image P through the windshield WS. C The upper line L is shown as an extension. U is the path of the image light at the center in the width direction and at the top position in the area where the virtual image P can be displayed. B is the path of the image light at the center in the width direction and at the bottom position in the area where the virtual image P can be displayed. In this embodiment, U The image light is irradiated from the far side to the bottom line L B The image light is irradiated.

[0021] FIG. 2 is a schematic diagram showing an example of the structure of an image projection device 100 according to this embodiment. As shown in FIG. 2, the image projection device 100 includes an image display unit 10, a primary mirror 20, a secondary mirror 30, a circuit board 40, and a cable 50. The combination of the primary mirror 20 and the secondary mirror 30 constitutes the projection optical unit of the present invention. In the example shown in FIG. 2, the combination of the primary mirror 20 and the secondary mirror 30 is shown as the projection optical unit, but the configuration of the projection optical unit is not limited to this. As an example, a reflecting mirror may be used in addition to the primary mirror 20 and the secondary mirror 30, or a wavelength filter that cuts ultraviolet light and infrared light may be used.

[0022] The image display unit 10 is a part that displays a projected image based on image information from the circuit board 40. The specific configuration of the image display unit 10 is not limited, and conventionally known devices such as a liquid crystal display device, an organic EL display device, or a light modulation element can be used. In the example shown in FIG. 2, a liquid crystal display device is used as the image display unit 10. The image displayed on the display surface of the image display unit 10 is irradiated onto the primary mirror 20 as image light.

[0023] When a transmissive liquid crystal display device is used as the image display unit 10, a light source unit (not shown) is provided to irradiate light from the rear side of the display surface. The irradiated light passes through the image display unit 10, thereby irradiating the image light of the image displayed on the display unit. Alternatively, a reflective image display unit 10 may be used, and a light source unit may be disposed on the display surface side to irradiate the light. The specific configuration of the light source unit is not limited, and a light emitting diode (LED) or a laser light source may be used. When an organic EL display device is used as the image display unit 10, the light source unit and the image display unit 10 are integrally configured.

[0024] The primary mirror 20 is an optical member onto which image light emitted from the image display unit 10 is incident and which reflects it in the direction of the secondary mirror 30. In the example shown in FIG. 2, the primary mirror 20 is a free-form mirror with a concave shape optically designed to project the image light as a virtual image P. The reflective surface of the primary mirror 20 is concave in the short side direction (first direction), which is the height direction. Furthermore, the reflective surface of the primary mirror 20 is set so that the height direction component of the image light forms an intermediate image at an intermediate image position F before reaching the secondary mirror 30. Furthermore, the reflective surface of the primary mirror 20 may also be concave in the long side direction (second direction), which is the width direction.

[0025] The secondary mirror 30 is an optical component that receives the image light reflected by the primary mirror 20 and reflects it in the direction of the windshield WS. In the example shown in FIG. 2, the secondary mirror 30 is a free-form mirror with a concave shape optically designed to project the image light as a virtual image P. The reflective surface of the secondary mirror 30 is concave in the short side direction (first direction), which is the height direction. The reflective surface of the secondary mirror 30 may also be concave in the long side direction (second direction), which is the width direction.

[0026] The circuit board 40 is a control unit that is connected to the image display unit 10 via a cable 50 so as to be able to communicate information with the image display unit 10 and controls each unit. The configuration of the circuit board 40 is not limited, but one example includes a CPU (Central Processing Unit) for processing information, a memory device, a recording medium, an information communication device, etc. The circuit board 40 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. In the example shown in FIG. 2, the circuit board 40 is disposed upright on the back side of the secondary mirror 30, but the position and orientation of the circuit board 40 are not limited.

[0027] The cable 50 is a member that electrically connects the image display unit 10 and the circuit board 40 to enable information communication between them. There are no specific limitations on the shape or structure of the cable 50, and a conventionally known flexible cable or the like can be used. Although not shown in FIG. 2, a portion of the cable 50 may be branched and connected to the outside of the image projection device 100 to transmit power and control signals.

[0028] Image projection device 100 may also include a housing (not shown), with each component housed in the housing. The housing is provided with a projection opening that transmits light, and image light reflected by secondary mirror 30 is irradiated onto windshield WS through the projection opening. There are no limitations on the material that can be used to form the housing, and resin or metal materials that block visible light can be used.

[0029] In image projection device 100 of this embodiment, image light emitted from image display unit 10 is reflected by primary mirror 20 and secondary mirror 30 and is then emitted onto windshield WS. At this time, the height component of the image light is collected at intermediate imaging position F located between primary mirror 20 and secondary mirror 30, and the height component is expanded from intermediate imaging position F toward secondary mirror 30. The image light reaches the viewpoint after its light diameter is expanded by primary mirror 20 and secondary mirror 30 included in the projection optical unit, so the driver visually recognizes a virtual image P formed by the image light as if it were formed at a predetermined distance.

[0030] 2, the direction perpendicular to the display surface of the image display unit 10 is indicated by an arrow as a normal direction NV. As shown in FIG. 2, the normal direction NV is a reference line L C Therefore, even if external light is incident from above the windshield WS, is reflected by the secondary mirror 30 and the primary mirror 20, and reaches the image display unit 10, the external light that is reflected by the image display unit 10 and becomes stray light will not be reflected by the reference line L C As a result, in image projection device 100, the possibility that stray external light will be reflected by primary mirror 20, secondary mirror 30, and windshield WS and reach viewpoint position E is reduced, and the visibility of virtual image P can be improved.

[0031] Furthermore, it is preferable that the normal direction NV of the image display unit 10 faces outward from the reflecting surface of the primary mirror 20. This ensures that stray light that is specularly reflected by the display surface, out of the external light that reaches the image display unit 10, reaches a position away from the primary mirror 20.

[0032] The normal direction NV of the image display unit 10 is the upper edge line L of the image light projecting the virtual image P. U Reference line L on the side C This makes it easy to form the virtual image P vertically in space and make it face the viewpoint position E directly.

[0033] The normal direction NV of the image display unit 10 is parallel to the reference line L C The image display unit 10 may be tilted from the side of the secondary mirror 30. In this case, it is preferable to connect the cable 50 to the side of the image display unit 10 closest to the secondary mirror 30, and to arrange the circuit board 40 upright on the back side of the secondary mirror 30. By aligning the tilt direction of the image display unit 10 with the extension direction of the cable 50, it is possible to simplify the wiring of the cable 50, thereby saving space and improving design flexibility. Furthermore, by arranging the circuit board 40 on the side opposite to the reflective surface of the secondary mirror 30 (the back side), it is possible to effectively utilize the space within the housing and reduce the size of the image projection device 100.

[0034] As described above, in the image projection device 100 of this embodiment, the reference line L of the image light between the image display unit 10 and the primary mirror 20 is C and the normal direction NV of the image display unit 10, the possibility that external light reaching the image display unit 10 will be reflected up to the viewpoint position E is reduced, stray external light is suppressed, and the visibility of the virtual image P can be improved.

[0035] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. 3. Description of content that overlaps with the first embodiment will be omitted. FIG. 3 is a schematic diagram showing an example of the structure of an image projection device 100 according to this embodiment. This embodiment differs from the first embodiment in that an intermediate mask 60 is provided between the primary mirror 20 and the secondary mirror 30. As shown in FIG. 3, the image projection device 100 includes an image display unit 10, the primary mirror 20, the secondary mirror 30, a circuit board 40, a cable 50, and the intermediate mask 60. An opening 61 is also provided in the intermediate mask 60.

[0036] The intermediate mask 60 is disposed between the primary mirror 20 and the secondary mirror 30 and is a member made of a light-blocking material. By providing the intermediate mask 60, even if external light reaches the housing from outside the image projection device 100, a portion of the light can be blocked by the intermediate mask 60. While the intermediate mask 60 is shown in FIG. 3 as having a flat plate shape, it may also have a curved shape and is not limited in shape. The position and orientation of the intermediate mask 60 are also not limited, and it is preferable to place the intermediate mask 60 in a position and orientation that effectively blocks external light from reaching the image display unit 10. An opening 61 is formed in a portion of the intermediate mask 60.

[0037] The opening 61 is an opening or a notch formed in the intermediate mask 60. A light-transmitting material may be disposed in the opening 61. The opening 61 is located on the path of the image light reflected by the primary mirror 20, and the image light passes through the opening 61 to reach the secondary mirror 30. The opening 61 is also provided near an intermediate imaging position F of the image light reflected by the primary mirror 20.

[0038] 3, intermediate mask 60 is disposed so as to avoid the optical path of the image light, and opening 61 is provided on the optical path of the image light. Therefore, the image light reflected by primary mirror 20 passes through opening 61 without being blocked by intermediate mask 60, and is projected from secondary mirror 30. Furthermore, even if external light incident from above windshield WS is reflected by secondary mirror 30 and travels toward primary mirror 20, most of the light is blocked by intermediate mask 60. As a result, external light is effectively blocked by intermediate mask 60, reducing the amount of external light that reaches image display unit 10, and deterioration of image display unit 10 due to temperature rise can be suppressed.

[0039] Furthermore, since the image light reflected by primary mirror 20 is intermediately imaged at intermediate image position F, the cross-sectional area through which the image light passes is smallest at intermediate image position F. Therefore, by providing opening 61 near intermediate image position F, the area of ​​opening 61 required to pass the image light can be reduced, and the amount of external light that reaches image display unit 10 can be further reduced.

[0040] Furthermore, it is preferable that the normal direction NV of the image display unit 10 is directed away from the opening 61 of the intermediate mask 60. As a result, even if external light that reaches the image display unit 10 is reflected and becomes stray light, the stray light is blocked by the intermediate mask 60, reducing the possibility that the stray light will be reflected by the primary mirror 20, the secondary mirror 30, and the windshield WS and reach the viewpoint E, thereby improving the visibility of the virtual image P.

[0041] As described above, in the image projection device 100 of this embodiment, the reference line L of the image light between the image display unit 10 and the primary mirror 20 is C and the normal direction NV of the image display unit 10, the possibility that external light reaching the image display unit 10 will be reflected up to the viewpoint position E is reduced, stray external light is suppressed, and the visibility of the virtual image P can be improved.

[0042] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. 4. Description of content that overlaps with the first embodiment will be omitted. FIG. 4 is a schematic diagram showing an example of the structure of an image projection device 100 according to this embodiment. This embodiment differs from the first embodiment in that image light is not intermediately imaged between the primary mirror 20 and the secondary mirror 30. As shown in FIG. 4, the image projection device 100 includes an image display unit 10, a primary mirror 20, a secondary mirror 30, a circuit board 40, and a cable 50.

[0043] In this embodiment, the bottom line L B The image light is irradiated from the far side to the upper edge line L U In this embodiment, the normal direction NV of the image display unit 10 is also the same as the reference line L of the image light between the image display unit 10 and the primary mirror 20. C As a result, in image projection device 100, the possibility that stray external light will be reflected by primary mirror 20, secondary mirror 30, and windshield WS and reach viewpoint position E is reduced, and the visibility of virtual image P can be improved.

[0044] Also in this embodiment, the normal direction NV of the image display unit 10 is parallel to the reference line L C The image display unit 10 is tilted from the side closest to the secondary mirror 30, with the cable 50 connected to the side of the image display unit 10 closest to the secondary mirror 30, and the circuit board 40 is disposed upright on the back surface of the secondary mirror 30. By aligning the tilt direction of the image display unit 10 with the extension direction of the cable 50, it is possible to simplify the wiring of the cable 50, thereby saving space and improving design freedom. Furthermore, by disposing the circuit board 40 on the opposite side (back surface side) from the reflective surface of the secondary mirror 30, it is possible to effectively utilize the space within the housing and reduce the size of the image projection device 100.

[0045] As described above, in the image projection device 100 of this embodiment, the reference line L of the image light between the image display unit 10 and the primary mirror 20 is Cand the normal direction NV of the image display unit 10, the possibility that external light reaching the image display unit 10 will be reflected up to the viewpoint position E is reduced, stray external light is suppressed, and the visibility of the virtual image P can be improved.

[0046] 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]

[0047] 100...Image projection device 10...Image display section 20...Primary mirror 30...Secondary mirror 40...Circuit board 50…Cable 60...Intermediate mask 61...Opening

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; a central optical path of the image light between the image display unit and the primary mirror is defined as a reference line; a direction perpendicular to a display surface of the image display unit is defined as a normal direction; An image projection device, wherein the reference line and the normal line direction are different from each other.

2. 2. The image projection device according to claim 1, 10. An image projection device, wherein the normal direction is directed outward from the reflecting surface of the primary mirror.

3. 2. The image projection device according to claim 1, a secondary mirror onto which the image light reflected by the primary mirror is incident and reflected; 10. An image projection device, wherein the image light is intermediately imaged in a height direction between the primary mirror and the secondary mirror.

4. 4. The image projection device according to claim 3, an intermediate mask having an opening disposed between the primary mirror and the secondary mirror; The image projection device is characterized in that the image light passes through the opening.

5. 5. The image projection device according to claim 4, An image projection device, wherein the normal direction is directed toward a direction other than the opening of the intermediate mask.

6. 6. The image projection device according to claim 3, a circuit board for controlling the image display unit; a cable electrically connecting the image display unit and the circuit board; The image projection device is characterized in that the circuit board is disposed on the rear side of the secondary mirror.

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