WO2023189620A1

WO2023189620A1 - Image projection device

Info

Publication number: WO2023189620A1
Application number: PCT/JP2023/010162
Authority: WO
Inventors: 隆延豊嶋; 由莉濱田
Original assignee: 株式会社小糸製作所
Priority date: 2022-03-31
Filing date: 2023-03-15
Publication date: 2023-10-05

Abstract

An image generation device (12) comprises: an image generation part (123) that generates an image; a prism (124) having an incidence surface (124a) on which at least part of light emitted from the image generation part (123) is incident, an emission surface (124b) which emits light incident from the incidence surface (124a), and side surfaces (124c, 124d, 124e) which connect the incidence surface (124a) and the emission surface (124b); and a light-blocking part (125) which is provided on the emission surface (124b). The light-blocking part (125) blocks light reflected by the side surfaces.

Description

image projection device

The present disclosure relates to an image projection device.

Patent Document 1 discloses a head-up system in which light constituting an image displayed by a display element is projected onto a windshield using an optical system, the light is reflected by the windshield, and the image is superimposed as a virtual image on the real space in front of the vehicle. A display (Head-Up Display: HUD) is disclosed.

Japanese Patent Application Publication No. 2021-189411

Incidentally, although it has been considered to use a prism as an optical system to change the direction of light emitted from a display element, the light may be reflected on the side surface of the prism and become stray light.

An object of the present disclosure is to suppress the generation of stray light in an image projection device including a prism.

An image projection device according to one aspect of the present disclosure includes:
An image projection device that projects an image,
an image generation unit that generates an image;
a prism having an entrance surface into which at least part of the light emitted from the image generation section is incident, an exit surface through which the light incident from the entrance surface is output, and a side surface connecting the entrance surface and the exit surface; ,
a light shielding section provided on the output surface;
It is equipped with
The light blocking portion blocks light reflected from the side surface.

According to the present disclosure, it is possible to suppress the generation of stray light in an image projection device including a prism.

FIG. 1 is a schematic diagram of a head-up display (HUD) according to the present embodiment, viewed from the side of a vehicle. 1 is a schematic diagram illustrating the configuration of an image generation device according to an embodiment. FIG. 3 is a perspective view illustrating the configuration of a prism and a light shielding section in FIG. 2; FIG. 3 is a diagram for explaining the optical path of light from an image generation unit to an eyebox. FIG. 3 is a diagram showing a virtual image seen through the windshield. FIG. 3 is a cross-sectional view of a prism for explaining the shape of a light shielding part. FIG. 7 is a perspective view illustrating the configuration of a prism and a light shielding section according to a modified example. FIG. 7 is a cross-sectional view of a prism for explaining the shape of a light shielding part according to a modification. FIG. 7 is a cross-sectional view of a prism for explaining the shape of a light shielding part according to a modification. FIG. 7 is a perspective view illustrating the configuration of a prism and a light shielding section according to another modification. FIG. 7 is a cross-sectional view of a prism for explaining the shape of a light shielding part according to another modification.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, arrow U indicates the upward direction of the illustrated structure. Arrow D indicates the downward direction of the illustrated structure. Arrow F indicates the forward direction of the illustrated structure. Arrow B indicates the rearward direction of the illustrated structure. Arrow R indicates the right direction of the illustrated structure. Arrow L indicates the left direction of the illustrated structure. These directions are relative directions set for the image generation device 12 shown in FIG.

FIG. 1 is a schematic diagram of the HUD 10 according to the present embodiment viewed from the side of the vehicle 20. As illustrated in FIG. 1, the HUD 10 is installed in the cabin of a vehicle 20. For example, the HUD 10 is placed within the dashboard of the vehicle 20.

The HUD 10 functions as a visual interface between the vehicle 20 and the occupants of the vehicle 20. Specifically, the HUD 10 displays predetermined information as a virtual image toward the occupants of the vehicle 20 so that the information is superimposed on the real space outside the vehicle 20 (for example, the surrounding environment in front of the vehicle 20). is configured to do so. The predetermined information is displayed as a still image or a moving image (video).

The HUD 10 includes a HUD main body 11, a picture generation unit (PGU) 12, a concave mirror 13, and a control unit 14. The HUD main body 11 has a housing 111 and an exit window 112. Inside the housing 111, an image generation device 12, a concave mirror 13, and a control unit 14 are arranged. The exit window 112 is made of a transparent plate that transmits visible light.

The image generation device 12 is configured to generate a predetermined image for forming a virtual image and emit light constituting the image. The light emitted from the image generation device 12 is, for example, visible light.

The concave mirror 13 is placed on the optical path of the light emitted from the image generation device 12. In this example, the concave mirror 13 is placed in front of the image generation device 12. Concave mirror 13 is configured to reflect light emitted from image generation device 12 toward windshield 21 (for example, the front window of vehicle 20). The concave mirror 13 has a concavely curved reflective surface. The concave mirror 13 reflects the light emitted by the image generation device 12 so that an image of the light emitted and formed by the image generation device 12 is formed on the windshield 21 at a predetermined magnification. Note that the concave mirror 13 may be configured to be movable in its position and direction by a drive mechanism (not shown).

The control unit 14 is configured to control the operation of each part of the HUD 10. The control unit 14 is connected to a vehicle control unit (not shown) of the vehicle 20. The control unit 14 generates a control signal for controlling the operation of the image generation device 12 based on information regarding the running state of the vehicle 20 and the surrounding environment of the vehicle 20 transmitted from the vehicle control unit, and converts the control signal into an image. It is transmitted to the generation device 12.

The light emitted from the image generation device 12 is reflected by the concave mirror 13 and emitted from the exit window 112 of the HUD main body 11. The light emitted from the exit window 112 is irradiated onto the windshield 21. A portion of the light irradiated onto the windshield 21 from the exit window 112 is reflected toward the passenger's viewpoint E. As a result, the occupant recognizes the light emitted from the HUD 10 as a virtual image (predetermined image) formed at a predetermined distance in front of the windshield 21 . As a result of the image generated by the image generation device 12 being superimposed on the real space in front of the vehicle 20 through the windshield 21, the occupant can see that the virtual image object I formed by the predetermined image is outside the vehicle 20. It can be visually recognized as floating above the road where it is located.

In this example, the HUD 10 is configured to be able to form virtual images at two positions that are different in distance from the passenger's viewpoint E. Specifically, the image generation device 12 generates a first image for forming a first virtual image (virtual image object Ia) at a position that is long from the passenger's viewpoint E (for example, about 15 m, hereinafter referred to as “distant”). generate. Light La constituting the first image emitted from the image generation device 12 is reflected by the concave mirror 13 and emitted from the exit window 112 of the HUD main body 11 . The light emitted from the exit window 112 is reflected by the windshield 21 and is visually recognized as a virtual image object Ia. Note that optical elements such as lenses and mirrors for changing the focal length (apparent optical path length) of the light La may be appropriately placed on the optical path of the light La heading from the image generation device 12 to the concave mirror 13.

On the other hand, the image generation device 12 is configured to form a second virtual image (virtual image object Ib) at a position that is shorter from the passenger's viewpoint E than the first virtual image (for example, about 3 m, hereinafter referred to as near). A second image is generated. The light Lb constituting the second image emitted from the image generation device 12 is reflected by the concave mirror 13 and emitted from the exit window 112 of the HUD main body 11 . The light emitted from the exit window 112 is reflected by the windshield 21 and is visually recognized as a virtual image object Ib.

Next, the specific configuration of the image generation device 12 according to this embodiment will be described using FIGS. 2 to 6.
As illustrated in FIG. 2, the image generation device 12 includes a light source section 121, a lens 122, and an image generation section 123. In this example, the image generation device 12 has a deflection function, and further includes a prism 124 and a light shielding section 125. The light source section 121, lens 122, image generation section 123, prism 124, and light shielding section 125 are arranged inside a housing (not shown). The image generation device 12 is an example of an image projection device.

The light source section 121 has a light source 121A and a substrate 121B. The light source 121A is, for example, an LED light source or a laser light source. The LED light source is, for example, a white LED light source. The laser light source is, for example, an RGB laser light source configured to emit red laser light, green laser light, and blue laser light, respectively. The light source 121A is mounted on the substrate 121B. The board 121B is, for example, a printed board made of an insulator on which electrical circuit wiring is printed on the surface or inside.

The lens 122 emits the light emitted from the light source 121A toward the image generation unit 123. In addition to or instead of the lens 122, a diffuser plate, a magnifying glass, etc. may be arranged.

The image generation unit 123 generates a predetermined image displayed as a virtual image using the light emitted from the lens 122. The image generation unit 123 is, for example, a liquid crystal display (LCD). In a liquid crystal display, a drive circuit applies a voltage to the liquid crystal phase to switch between a state in which light is transmitted through the polarizing film and an opaque state in which light cannot be transmitted through the polarizing film. The liquid crystal phase and polarizing film are divided into a plurality of pixels, and each pixel can be switched between light transmission and non-transmission states. A predetermined image is generated by allowing light to pass through some pixels and not allowing light to pass through other pixels. Note that as the image generation unit 123, a DMD (Digital Mirror Device) or the like may be used instead of a liquid crystal display.

In this example, the image generation unit 123 has a first area 123A and a second area 123B. The first region 123A generates a first image for forming a first virtual image. Light La constituting the first image is emitted from the first area 123A. The second region 123B generates a second image for forming a second virtual image. Light Lb constituting the second image is emitted from the second region 123B. In addition, in FIG. 2, the dashed-dotted line in the image generation part 123 shows the first area|region 123A and the second area|region 123B. Further, the two-dot chain line extending from the output surface of the image generation unit 123 indicates a bundle of light La emitted from the first region 123A and a bundle of light Lb emitted from the second region 123B.

The prism 124 is configured to emit at least a portion of the light emitted from the image generation unit 123 toward the concave mirror 13. In this example, the prism 124 is arranged at a position through which the light La emitted from the first region 123A of the image generation unit 123 and directed toward the concave mirror 13 passes. The prism 124 is configured to change the traveling direction of the light La emitted from the first region 123A.

Specifically, the prism 124 has an entrance surface 124a, an exit surface 124b, and

side surfaces

124c, 124d, 124e, and 124f, as illustrated in FIGS. 2 and 3. The entrance surface 124a and the exit surface 124b face each other with their normal directions deviated from each other. The side surface 124c and the side surface 124d face each other with their normal directions aligned, and the side surface 124e and the side surface 124f face each other with their normal directions aligned. Light La emitted from the first region 123A of the image generation unit 123 is incident on the entrance surface 124a. The exit surface 124b faces the entrance surface 124a and is inclined with respect to the entrance surface 124a. The light La that has entered the incident surface 124a travels within the prism 124, and is emitted from the exit surface 124b in a direction different from the direction of incidence.

The side surfaces 124c, 124d, 124e, and 124f are surfaces that connect the entrance surface 124a and the exit surface 124b. As illustrated in FIG. 3, the side surface 124c is a surface connecting the right ends of the entrance surface 124a and the exit surface 124b. The side surface 124d is a surface connecting the left ends of the entrance surface 124a and the exit surface 124b. The side surface 124e is a surface that connects the front ends of the entrance surface 124a and the exit surface 124b. The side surface 124f is a surface connecting the rear ends of the entrance surface 124a and the exit surface 124b.

The light shielding part 125 is provided on the output surface 124b of the prism 124, and blocks light reflected from the side surface of the prism 124. For example, the light shielding part 125 is configured to be able to absorb light reflected from the side surface of the prism 124. Specifically, the light-shielding portion 125 may be formed of a plate-like member of metal such as aluminum or a light-shielding member such as resin, or the surface of the prism 124 may be painted black or the surface of the prism 124 may be coated with a laser or the like. It may also be formed by subjecting it to a blackening treatment or the like.

In this example, the prism 124 extends in the longitudinal direction (front-back direction in FIG. 3). Two

light shielding parts

125A and 125B are provided at both longitudinal ends of the peripheral area of the output surface 124b, and shield light reflected from the

side surfaces

124e and 124f of the prism 124. Moreover, the

light shielding parts

125A and 125B are in contact with the output surface 124b.

Here, the positions and orientations of the image generation section 123 and the optical members (prism 124, concave mirror 13, etc.) disposed on the optical path of the light emitted from the image generation section 123 are such that the light emitted from the image generation section 123 is It is set so that it is reflected by the windshield 21 via an optical member and reaches the eye box of the occupant of the vehicle 20. An eyebox is a fixed area centered on the position of a typical passenger's eyes. The occupant of the vehicle 20 can recognize the light reflected by the windshield 21 as a virtual image when the occupant's eyes are located within the eye box.

FIG. 4 shows an optical path diagram of light reaching the eyebox from the image generation unit 123. FIG. 5 shows a virtual image visually recognized by the occupant of the vehicle 20 through the windshield 21. In FIG. 4, the dotted hatched area indicates the maximum range of the optical path of the light that is emitted from the image generation unit 123 and reaches the eyebox (hereinafter referred to as the maximum optical path range). In FIG. 5, the range indicated by the two-dot chain line indicates the range A in which a virtual image can be formed by the light that has reached the eyebox.

For example, when displaying the virtual image object Ia within the virtual image formation possible range A as shown in FIG. 5, the first image for forming the virtual image object Ia from the first area 123A of the image generation unit 123 shown in FIG. It emits light that makes up the . At this time, most of the light emitted from the image generation unit 123 enters the entrance surface 124a of the prism 124 and travels inside the prism 124, as shown, for example, in the first optical path L1. The light is then emitted from the output surface 124b of the prism 124 and reaches the eyebox via an optical member such as the concave mirror 13. The light reaching the eyebox is visually recognized by the occupant of the vehicle 20 as a virtual image object Ia.

However, a part of the light emitted from the image generation unit 123, for example, light with a large emission angle from the light source, deviates from the maximum optical path range. A portion of the light having such a large output angle does not enter the prism 124, for example, as shown by the second optical path L2, and therefore does not reach the eye box and is not visually recognized by the occupant. However, as shown by the third optical path L3, for example, a portion of the light with a large exit angle is reflected by the side surface of the prism 124 and travels within the maximum optical path range again. When the light reaches the eyebox, it is visually recognized as an unintended virtual image object Ia' formed outside the virtual image object Ia, as illustrated in FIG. Alternatively, the light may become noise of the virtual image object Ia.

In contrast, according to the image generation device 12 according to the present embodiment, a light shielding portion 125 is provided on the exit surface 124b of the prism 124, as illustrated in FIG. This light blocking portion 125 blocks light reflected from the side surface of the prism 124. Thereby, it is possible to prevent the light reflected from the side surface of the prism 124 from becoming stray light and, for example, from forming an unintended virtual image object Ia'.

Furthermore, in this embodiment, since the light shielding portion 125 is in contact with the output surface 124b of the prism 124, it can more reliably block the light emitted from the output surface 124b. Note that the light shielding portion 125 may be provided on the output surface 124b of the prism 124 without being in contact with the output surface 124b. For example, the light shielding part 125 may be arranged with a gap in between the light emitting surface 124b of the prism 124, or may be arranged a predetermined distance apart. In other words, the state where the light shielding part 125 is not in contact with the output surface 124b means that the light shielding part 125 is disposed at a predetermined distance from the output surface 124b, and is also made of, for example, a metal plate-like member. This may also include a state in which a mounting gap is formed when the light shielding portion 125 is attached so as to be in contact with the light emitting surface 124b.

Furthermore, in the present embodiment, the prism 124 extends in the longitudinal direction, and the light shielding portions 125 are provided at both ends of the emission surface 124b in the longitudinal direction. When light is made incident on the prism 124, the wider the range of light incident on the prism 124, the more light is reflected from the side surfaces of the prism 124. Therefore, the light blocking portion 125 can block most of the light that may be reflected on the side surface of the prism 124 and become stray light.

The area on the output surface 124b of the prism 124 where the light shielding part 125 is provided is appropriately set according to the shape and arrangement of the image generating part 123 and the prism 124. For example, FIG. 6 shows a cross section of the prism 124 in a plane along the longitudinal direction (front-back direction in FIG. 6) and the light irradiation direction of the image generation unit 123 (upward direction in FIG. 6). As illustrated in FIG. 6, the light shielding portion 125A may be formed to extend from the position P1 to the front end in the longitudinal direction on the exit surface 124b of the prism 124. Further, the light shielding portion 125B may be formed to extend from the position P2 to the rear end in the longitudinal direction on the exit surface 124b of the prism 124.

At position P1, the image is emitted from the rear end in the longitudinal direction of the exit surface of the image generation unit 123 (first region 123A), enters the front end in the longitudinal direction of the entrance surface 124a of the prism 124, and the most image on the side surface 124e of the prism 124 This is the position where the light L11 reflected at a point close to the output surface of the generation unit 123 enters the output surface 124b. At position P2, the light is emitted from the front end in the longitudinal direction of the exit surface of the image generating section 123, enters the rear end in the longitudinal direction of the entrance surface 124a of the prism 124, and is located closest to the exit surface of the image generating section 123 on the side surface 124f of the prism 124. This is the position where the light L12 reflected at a point close to is incident on the exit surface 124b.

According to such a configuration, for example, as shown by the chain double-dashed line in FIG. The light is blocked by the light blocking section 125B. Furthermore, the light L22 that is emitted from a position closer to the center than the front end in the longitudinal direction of the output surface of the image generation section 123 and reflected on the side surface 124f of the prism 124 is blocked by the light blocking section 125B. Similarly, light emitted from a position from the longitudinal rear end to the center of the output surface of the image generating section 123 and reflected on the side surface 124e of the prism 124 is blocked by the light blocking section 125A. Therefore, the light emitted from the image generation unit 123 and reflected on the side surface of the prism 124 can be prevented from becoming stray light.

Note that in the above embodiment, the light shielding portions 125 are provided at both ends in the longitudinal direction in the peripheral region of the output surface 124b of the prism 124. However, for example, the light shielding part 125 may be provided in the entire peripheral area of the output surface 124b. Thereby, it is possible to suppress the formation of an unintended virtual image object Ia' due to stray light not only outside the virtual image object Ia in the left-right direction but also outside the virtual image in the vertical direction.

Furthermore, in the above embodiment, the image generation device 12 may further include a light shielding section 126, as illustrated in FIG. Specifically, the light blocking section 126 is provided on the entrance surface 124a of the prism 124, and blocks light that is about to reach the side surface of the prism 124 from entering the prism 124. The light shielding part 126 may be formed of a metal plate member such as aluminum or a light shielding member such as resin, or the surface of the prism 124 may be painted black or the surface of the prism 124 may be subjected to blackening treatment using a laser or the like. It may be formed by applying.

In this example, two

light shielding parts

126A and 126B are provided at both end regions in the longitudinal direction in the peripheral region of the entrance surface 124a. That is, the

light shielding parts

126A and 126B block the light that is about to reach the

side surfaces

124e and 124f of the prism 124 from entering the prism 124. Moreover, the

light shielding parts

126A and 126B are in contact with the entrance surface 124a.

In this manner, by providing the light blocking portion 126 on the entrance surface 124a of the prism 124, light that may reach the side surface of the prism 124 and become stray light is blocked from entering the prism 124, so that the generation of stray light can be further suppressed.

The area where the light shielding section 126 is provided on the entrance surface 124a of the prism 124 is appropriately set according to the shape and arrangement of the image generating section 123 and the prism 124. For example, FIG. 8 shows a cross section of the prism 124 in a plane along the longitudinal direction (front-back direction in FIG. 8) and the light irradiation direction of the image generation unit 123 (upward direction in FIG. 8).

As illustrated in FIG. 8, the light blocking portion 126 may be formed to block part of the light that is about to reach the side surface of the prism 124 from entering the prism 124. For example, some of the light L32 that is emitted from the front end in the longitudinal direction of the output surface of the image generation unit 123 (first region 123A) and attempts to reach the side surface 124f of the prism 124 reaches the entrance surface 124a of the prism 124. However, the remaining light L33 is blocked by the light blocking portion 126B. Furthermore, the light L34 that is emitted from a position closer to the center than the front end in the longitudinal direction of the output surface of the image generation section 123 and attempts to reach the side surface 124f of the prism 124 is blocked by the light blocking section 126B. Note that the light L32 that is not blocked by the light blocking portion 126B is reflected by the side surface 124f of the prism 124, and is blocked by the light blocking portion 125B. Similarly, some of the light L31 that is emitted from the rear end in the longitudinal direction of the output surface of the image generation unit 123 (first region 123A) and attempts to reach the side surface 124e of the prism 124 is transmitted to the entrance surface of the prism 124. The light enters the light beam 124a, is reflected by the side surface 124e, and is blocked by the light blocking portion 125A. Light that is emitted from other positions from the longitudinal rear end to the center of the output surface of the image generation section 123 and attempts to reach the side surface 124e of the prism 124 is blocked by the light blocking section 126A.

Alternatively, as illustrated in FIG. 9, the light shielding portion 126A may be formed to extend from the position P3 to the front end in the longitudinal direction on the entrance surface 124a of the prism 124. The light shielding portion 126B may be formed, for example, on the entrance surface 124a of the prism 124 so as to extend from the position P4 to the rear end in the longitudinal direction.

Position P3 is a point on the side surface 124e of the prism 124 that is emitted from the rear end in the longitudinal direction of the output surface of the image generation unit 123 (first region 123A), enters the entrance surface 124a of the prism 124, and is closest to the exit surface 124b on the side surface 124e of the prism 124. This is the position where the light L31 that reaches the point enters the incident surface 124a. Further, at position P4, light L32 is emitted from the front end in the longitudinal direction of the output surface of the image generation unit 123, enters the input surface 124a of the prism 124, and reaches the point closest to the output surface 124b on the side surface 124f of the prism 124. is the position where the light is incident on the incident surface 124a.

By forming the light shielding part 126A to extend from the position P3 to the front end in the longitudinal direction and the light shielding part 126B to extend from the position P4 to the rear end in the longitudinal direction, light that can become stray light is prevented from entering the prism 124. This can be better prevented. Specifically, for example, as shown by the two-dot chain line in FIG. 9, the light L41 that is emitted from the front end in the longitudinal direction of the output surface of the image generation section 123 and is about to reach the side surface 124f of the prism 124 is transmitted through the light shielding section. 126B. Furthermore, the light L42 that is emitted from a position closer to the center than the front end in the longitudinal direction of the output surface of the image generation section 123 and attempts to reach the side surface 124f of the prism 124 is blocked by the light blocking section 126B. Similarly, light emitted from a position from the longitudinal rear end to the center of the output surface of the image generating section 123 and attempting to reach the side surface 124e of the prism 124 is blocked by the light blocking section 126A. Therefore, it is possible to prevent the light reflected from the side surface of the prism 124 from becoming stray light. Note that in such a configuration, the light shielding part 126 can sufficiently prevent stray light, so the light shielding part 125 may be omitted.

Note that the light shielding portions 126 are provided at both ends in the longitudinal direction in the peripheral region of the entrance surface 124a of the prism 124, but for example, the light shielding portions 126 may be provided in the entire peripheral region of the entrance surface 124a. . Thereby, it is possible to suppress the formation of an unintended virtual image object Ia' due to stray light not only outside the virtual image object Ia in the left-right direction but also outside the virtual image in the vertical direction.

Further, in the above embodiment, instead of providing the light shielding part 126 on the entrance surface 124a, as illustrated in FIG. 10, the area of the entrance surface 124a may be formed to be smaller than the area of the exit surface 124b. good. In this example, the prism 124A is formed such that the length W1 in the longitudinal direction of the entrance surface 124a is shorter than the length W2 in the longitudinal direction of the exit surface 124b, and the light from the image generation unit 123 is The side surfaces 124e and 124f are inclined so that the

side surfaces

124e and 124f are visible when viewed from the incident direction (viewed from below in FIG. 10).

By forming the area of the entrance surface 124a of the prism 124A to be smaller than the area of the exit surface 124b in this way, light that could become stray light is prevented from entering the prism 124, so the generation of stray light can be further suppressed.

The length W1 of the entrance surface 124a in the longitudinal direction is appropriately set according to the shape and arrangement of the image generation unit 123 and the prism 124A. For example, FIG. 11 shows a cross section of the prism 124A along the longitudinal direction (front-back direction in FIG. 11) and the light irradiation direction of the image generation unit 123 (upward direction in FIG. 11). As illustrated in FIG. 11, the side surface 124e of the prism 124A directs the light L51 incident from the rear end in the longitudinal direction of the output surface of the image generation unit 123 to the front end of the entrance surface 131 of the concave mirror 13 in the longitudinal direction or The light may be configured to be reflected toward the front side in the longitudinal direction. Further, the side surface 124f of the prism 124A reflects the light L52 incident from the front end in the longitudinal direction of the output surface of the image generation unit 123 to the rear end in the longitudinal direction of the entrance surface 131 of the concave mirror 13 or to the rear side in the longitudinal direction. It may be configured to do so.

According to such a configuration, the light L52 emitted from the front end in the longitudinal direction of the output surface of the image generation unit 123 and reflected by the side surface 124f of the prism 124 does not enter the input surface 131 of the concave mirror 13. Furthermore, as shown by the two-dot chain line in FIG. 11, for example, the light L61 that is emitted from a position closer to the center than the front end in the longitudinal direction on the emission surface of the image generation unit 123 and reflected on the side surface 124f of the prism 124 is It does not enter the incident surface 131 of the concave mirror 13. Similarly, light emitted from a position from the longitudinal rear end to the center of the output surface of the image generation unit 123 and reflected by the side surface 124e of the prism 124 does not enter the input surface 131 of the concave mirror 13. Therefore, the light reflected on the side surface of the prism 124 can be prevented from being emitted from the prism 124 and entering the incident surface 131 of the concave mirror 13. Note that in such a configuration, the light shielding part 125 may be omitted because the shape of the entrance surface 124a can sufficiently prevent stray light.

In addition, although the prism 124A is formed such that the length W1 in the longitudinal direction of the entrance surface 124a is shorter than the length W2 in the longitudinal direction of the exit surface 124b, the length in the lateral direction of the entrance surface 124a also It may be formed to be shorter than the length of the surface 124b in the lateral direction. Thereby, it is possible to suppress the formation of an unintended virtual image object Ia' due to stray light not only outside the virtual image object Ia in the left-right direction but also outside the virtual image in the vertical direction.

Although the embodiments of the present invention have been described above, it goes without saying that the technical scope of the present invention should not be interpreted to be limited by the description of the present embodiments. This embodiment is merely an example, and those skilled in the art will understand that various modifications can be made within the scope of the invention as set forth in the claims. The technical scope of the present invention should be determined based on the scope of the invention described in the claims and the equivalent scope thereof.

The shapes of the

prisms

124, 124A are not limited to the shapes shown in the drawings. In addition, there is a possibility that a mounting structure is added to the

prisms

124 and 124A, but in that case, there is no side surface to which the mounting structure is added, so the light rays pass in the direction of the additional shape without total reflection, and as shown in FIG. Since stray light such as L3 that passes only within the maximum optical path range within the HUD housing does not necessarily occur, it is only necessary to design it appropriately.

In addition to or instead of the concave mirror 13, an optical member such as a plane mirror may be placed on the optical path of light between the image generation device 12 and the windshield 21.

In the above embodiment, the image generation device 12 has a deflection function, and the

prisms

124 and 124A are arranged in the housing of the image generation device 12 and constitute a part of the image generation device 12. However, the image generation device 12 may also be configured without a deflection function. That is, the

prisms

124 and 124A may be arranged outside the housing of the image generation device 12 and configured separately from the image generation device 12. In this case, the HUD 10 constitutes an image projection device.

The HUD 10 is configured to form virtual images at different distances from the viewpoint E of the occupant of the vehicle 20. However, the HUD 10 may be configured to form a virtual image at a predetermined distance. In such a configuration, all of the light emitted from the image generation unit 123 is incident on the entrance surface 124a of the

prisms

124, 124A.

The present disclosure includes the following embodiments.
(Additional note)
(1) An image projection device that projects an image,
an image generation unit that generates an image;
a prism having an entrance surface into which at least part of the light emitted from the image generation section is incident, an exit surface through which the light incident from the entrance surface is output, and a side surface connecting the entrance surface and the exit surface; , is equipped with
The image projection device, wherein the area of the exit surface is larger than the area of the entrance surface.

This application is based on Japanese Patent Application No. 2022-059769 filed on March 31, 2022, the contents of which are incorporated herein by reference.

Claims

An image projection device that projects an image,
an image generation unit that generates an image;
a prism having an entrance surface into which at least part of the light emitted from the image generation section is incident, an exit surface through which the light incident from the entrance surface is output, and a side surface connecting the entrance surface and the exit surface; ,
a light shielding section provided on the output surface;
It is equipped with
In the image projection device, the light blocking section blocks light reflected from the side surface.
The image projection device according to claim 1, wherein the light shielding portion is in contact with the exit surface of the prism.
The image projection device according to claim 1 or 2, wherein the light shielding section is provided in at least a part of a peripheral area of the output surface.
the prism extends longitudinally;
The image projection device according to claim 3, wherein the light shielding portion is provided in regions at both ends of the output surface in the longitudinal direction.
It is equipped with an additional light shielding part provided on the incident surface,
The image projection device according to any one of claims 1 to 4, wherein the additional light blocking section blocks light attempting to reach the side surface from entering the prism.
The image projection device according to any one of claims 1 to 4, wherein the area of the exit surface is larger than the area of the entrance surface.