Image projection device

Abstract

An HUD (10) has: a housing (11); an illuminance sensor (16) that is provided inside the housing (11); and a transparent member (17) that limits the optical path of the sunlight such that the sunlight reaches the illuminance sensor (16) when the sunlight enters the inside of the housing (11) at a specific angle from an opening (111) of the housing (11).

Description

Image Projection Device

[0001] The present disclosure relates to an image projection device.

[0002] Patent Document 1 discloses a head-up display device that uses a concave mirror to reflect light from an image emitted by a video display device toward a vehicle occupant on a windshield, thereby displaying a virtual image to the vehicle occupant. To prevent damage to the video display device due to sunlight, this head-up display device uses an illuminance sensor to detect the intensity of sunlight illuminating the video display device, and a blocking mechanism blocks sunlight from entering the video display device depending on the intensity of the sunlight. The illuminance sensor directly detects the brightness of the screen of the video display device to detect the intensity of sunlight illuminating the video display device.

[0003] Japanese Patent Application Publication No. 2020-52070

[0004] Incidentally, it is conceivable to arrange an illuminance sensor in the path of sunlight incident within a head-up display device, for example, to detect sunlight incident from a direction with a high risk of being concentrated on the image display device, and, if such sunlight is detected, to take measures to prevent the sunlight from being incident on the image display device. However, the illuminance sensor detects not only sunlight incident from a direction with a high risk of being concentrated on the image display device, but also the brightness of sunlight incident from a different direction.

[0005] An object of the present disclosure is to increase the directionality of the detection of sunlight incident inside an image projection device.

[0006] An image projection device according to one aspect of the present disclosure is an image projection device configured to display a predetermined image toward a vehicle occupant, and includes a housing, an illuminance sensor provided inside the housing, and a restricting member that restricts the optical path of sunlight so that the sunlight reaches the illuminance sensor when the sunlight enters the interior of the housing from an opening of the housing at a specific angle.

[0007] According to the above configuration, the optical path of the sunlight is restricted so that it reaches the illuminance sensor, and therefore the directivity of the detection of sunlight incident on the inside of the image projection device by the illuminance sensor can be improved.

[0008] According to the present disclosure, it is possible to improve the directivity of detection of sunlight entering the inside of an image projection device.

[0009] Fig. 1 is a schematic diagram showing the configuration of a head-up display (HUD) according to an embodiment; Fig. 2 is a schematic diagram showing the configuration of the HUD of Fig. 1; Fig. 3 is a schematic diagram showing the configuration of a HUD according to a reference embodiment; Fig. 4 is a schematic diagram showing the configuration of a HUD of a first modified example; Fig. 5 is a schematic diagram showing the configuration of a HUD of a second modified example; Fig. 6 is a schematic diagram showing the configuration of a HUD of a third modified example;

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the dimensions of each component shown in the drawings may differ from the actual dimensions of each component. In addition, 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. These directions are relative directions set with respect to the HUD 10 shown in FIG. 1.

[0011] Fig. 1 is a schematic diagram of a HUD 10 according to an embodiment, viewed from the side of a vehicle 20. Fig. 2 is a schematic diagram of the HUD 10 of Fig. 1 .

[0012] 1, the HUD 10 is provided in a vehicle 20. For example, the HUD 10 is disposed in the dashboard of the vehicle 20.

[0013] The HUD 10 functions as a visual interface between the vehicle 20 and the occupants of the vehicle 20. Specifically, the HUD 10 is configured to display predetermined information as a predetermined image so that the predetermined information is superimposed on the real space outside the vehicle 20 (particularly, the surrounding environment in front of the vehicle 20). The predetermined image may include a still image or a moving image (video). The information displayed by the HUD 10 may be, for example, vehicle driving information related to the driving of the vehicle 20 and / or surrounding environment information related to the surrounding environment of the vehicle 20 (particularly, information related to objects present outside the vehicle 20). The HUD 10 is an example of an image projection device.

[0014] 1 , the HUD 10 has a housing 11, an exit window 12, an image generation unit (PGU) 13, a control unit 14, and a concave mirror 15. The image generation unit 13, the control unit 14, and the concave mirror 15 are arranged inside the housing 11.

[0015] The exit window 12 is attached to the opening 111 of the housing 11. The exit window 12 is made of, for example, a transparent plate that transmits visible light.

[0016] The image generation unit 13 is configured to emit light for generating a predetermined image. The light emitted from the image generation unit 13 is, for example, visible light. The image generation unit 13 has a display device 131. The display device 131 generates a predetermined image using light emitted from a light source (not shown). The display device 131 may be, for example, a liquid crystal display (LCD), an organic electroluminescence (EL) display, or a digital mirror device (DMD).

[0017] The control unit 14 controls the operation of each unit 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 unit 13 based on, for example, vehicle driving information, surrounding environment information, etc. transmitted from the vehicle control unit, and transmits the control signal to the image generation unit 13. The control unit 14 is equipped with a processor such as a CPU (Central Processing Unit) and a memory. The control unit 14 controls the operation of the image generation unit 13, etc. by having the processor execute a computer program read from the memory.

[0018] The concave mirror 15 is disposed on the optical path of the light emitted from the image generation unit 13. Specifically, the concave mirror 15 is disposed in front of the image generation unit 13 inside the housing 11. The concave mirror 15 is configured to reflect the light emitted from the image generation unit 13 toward a windshield 21 (e.g., a front window) of the vehicle 20. The concave mirror 15 has a reflective surface that is curved concavely. The concave mirror 15 reflects the light image emitted from the image generation unit 13 and formed at a predetermined magnification. The concave mirror 15 is configured to be rotatable by a drive mechanism 151.

[0019] In the HUD 10 configured as described above, as illustrated in FIG. 1 , light L1 emitted from the image generation unit 13 is reflected by the concave mirror 15 and emitted from the exit window 12. The light L1 emitted from the exit window 12 is irradiated onto the windshield 21. A portion of the light irradiated from the exit window 12 onto the windshield 21 is reflected toward the occupant's viewpoint E. As a result, the occupant perceives 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 displayed by the HUD 10 being superimposed on the real space in front of the vehicle 20 through the windshield 21, the occupant can visually perceive a virtual image object I formed by the predetermined image as floating above the road located outside the vehicle.

[0020] The HUD 10 further includes an illuminance sensor 16 and a transparent member 17. The illuminance sensor 16 and the transparent member 17 are disposed inside the housing 11.

[0021] The illuminance sensor 16 detects the brightness inside the housing 11 and outputs brightness information indicating the detected brightness to the control unit 14. The illuminance sensor 16 is disposed in a position where sunlight L11, which enters the inside of the housing 11 at a specific angle, does not directly enter the interior of the housing 11.

[0022] The transparent member 17 is formed of, for example, acrylic resin or glass. The transparent member 17 is configured to restrict the optical path of the sunlight L11 so that the sunlight L11 reaches the illuminance sensor 16 when the sunlight L11 enters the interior of the housing 11 through the opening 111 of the housing 11 at a specific angle. Specifically, the transparent member 17 has a surface 171 that reflects the sunlight L11 incident at the specific angle toward the illuminance sensor 16. The transparent member 17 is disposed so that the surface 171 totally reflects the sunlight L11 incident at the specific angle toward the illuminance sensor 16. When the angle of incidence of the sunlight with respect to the surface 171 is less than a specific angle, the sunlight passes through the surface 171. When the angle of incidence of the sunlight with respect to the surface 171 is equal to or greater than a specific angle, the sunlight is totally reflected by the surface 171 and directed toward the illuminance sensor 16. The transparent member 17 is an example of a restricting member.

[0023] 2 , when sunlight enters the HUD 10, sunlight L11 and L12 may be reflected by the concave mirror 15 and enter the image generation unit 13. In particular, when sunlight L11 enters the interior of the housing 11 at a specific angle, if sunlight L11 is concentrated on the display device 131 of the image generation unit 13, it may cause a local temperature rise, which may lead to a disturbance in the image display or thermal damage to the display device 131.

[0024] Therefore, the illuminance sensor 16 is used to detect sunlight L11 that enters the inside of the housing 11 at an angle that poses a high risk of being focused on the display device 131 of the image generation unit 13, and when the sunlight L11 is detected, the control unit 14 performs control to avoid thermal damage to the image generation unit 13 caused by the sunlight L11.

[0025] Specifically, for example, when control unit 14 receives brightness information from illuminance sensor 16, it determines whether the brightness detected by illuminance sensor 16 is equal to or greater than a threshold value. If the brightness detected by illuminance sensor 16 is equal to or greater than the threshold value, control unit 14 determines that there is a risk of heat damage to image generation unit 13.

[0026] When the control unit 14 determines that there is a risk of heat damage to the image generation unit 13, it performs control to avoid the heat damage. For example, the control unit 14 generates a control signal for controlling the operation of the drive mechanism 151 and outputs the control signal to the drive mechanism 151. This causes the drive mechanism 151 to change the orientation and / or posture of the concave mirror 15, making it possible to prevent sunlight L11 reflected by the concave mirror 15 from being concentrated on the display device 131.

[0027] Now, consider the placement of the illuminance sensor 16. Fig. 3 shows a HUD 100 according to a reference embodiment. In the HUD 100, the illuminance sensor 16 is placed at a position inside the housing 11 where sunlight L11 directly enters. When the illuminance sensor 16 is placed at a position where sunlight L11 directly enters in this way, not only sunlight L11 that enters from an angle with a high risk of being focused on the display device 131 but also sunlight L12 that enters from a different angle with a low risk of being focused on the display device 131 enters the illuminance sensor 16.

[0028] In contrast, in the image projection device 10 according to the present disclosure illustrated in FIG. 2 , the illuminance sensor 16 is disposed at a position where sunlight L11 does not directly enter the interior of the housing 11, and the transparent member 17 restricts the optical path of the sunlight so that only sunlight L11 reaches the illuminance sensor 16. That is, an angle at which there is a high risk of sunlight being concentrated on the display device 131 of the image generation unit 13 is set as the specific angle at which the optical path of the sunlight is restricted. As a result, sunlight L11 incident at the specific angle is totally reflected by the surface 171 of the transparent member 17 and enters the illuminance sensor 16. On the other hand, sunlight L12, which has a smaller angle of incidence than sunlight L11, is refracted by the transparent member 17 and passes through the transparent member 17, and does not enter the illuminance sensor 16. Note that sunlight with a larger angle of incidence than sunlight L11 is also totally reflected by the surface 171 of the transparent member 17, but it can be prevented from entering the illuminance sensor 16 by, for example, providing a shade around the illuminance sensor 16 that blocks only sunlight with a larger angle of incidence.

[0029] As described above, the image projection device 10 according to the present disclosure can improve the directionality of detection of sunlight incident on the inside of the HUD 10 by the illuminance sensor 16. Furthermore, since the surface 171 of the transparent member 17 reflects sunlight L11 incident at a specific angle toward the illuminance sensor 16, there is no need to orient the illuminance sensor 16 toward the sunlight L11, increasing the degree of freedom in the position and orientation of the illuminance sensor 16. Furthermore, sunlight L12 incident at angles other than the specific angle passes through the transparent member 17, and therefore the sunlight L12 is prevented from entering the illuminance sensor 16.

[0030] In this embodiment, the limiting member is a transparent member 17. However, for example, instead of the transparent member 17, a reflective member such as a mirror or a reflector may be used as the limiting member.

[0031] 4 shows the configuration of the HUD 30 of Modification 1. For convenience of explanation, the description of the members having the same reference numerals as those already explained in the above embodiment will be omitted.

[0032] As illustrated in FIG. 4 , the HUD 30 of the first modification includes a reflective member 18. The reflective member 18 is configured to restrict the optical path of sunlight L11 so that the sunlight L11 reaches the illuminance sensor 16 when the sunlight L11 enters the interior of the housing 11 through the opening 111 of the housing 11 at a specific angle. Specifically, the reflective member 18 has a reflective surface 181 that reflects the sunlight L11 incident at the specific angle toward the illuminance sensor 16. For example, the reflective surface 181 is formed with a total reflection coating that totally reflects the sunlight on the reflective surface 181 when the angle of incidence of the sunlight with respect to the reflective surface 181 is equal to or greater than a specific angle. Alternatively, the shape of the reflective surface 181 may be adjusted to focus the sunlight L11 incident at a specific angle onto the illuminance sensor 16. As a result, the sunlight L11 incident at the specific angle is reflected by the reflective surface 181 of the reflective member 18 and enters the illuminance sensor 16. On the other hand, sunlight L12, which has a smaller angle of incidence than sunlight L11, is reflected by the reflecting surface 181 of the reflecting member 18 in a direction different from the direction toward the illuminance sensor 16, and does not enter the illuminance sensor 16. Similarly, sunlight which has a larger angle of incidence than sunlight L11 is reflected by the reflecting surface 181 of the reflecting member 18 in a direction different from the direction toward the illuminance sensor 16, and does not enter the illuminance sensor 16. Therefore, even with this configuration, the directionality of detection of sunlight entering the interior of the HUD 10 by the illuminance sensor 16 can be improved.

[0033] The transparent member 17 and the reflecting member 18, which function as limiting members, are arranged to reflect, toward the illuminance sensor 16, sunlight L11 that enters through the opening 111 through which light L1 of a predetermined image emitted from the image generating unit 13 is emitted. However, the transparent member 17 and the reflecting member 18 may be arranged to reflect, toward the illuminance sensor 16, sunlight L11 that enters through an opening different from the opening 111 of the housing 11.

[0034] 5 shows the configuration of the HUD 40 of Modification 2. For convenience of explanation, the description of the members having the same reference numerals as those already explained in the above embodiment will be omitted.

[0035] 5 , in the HUD 40 of the second modification, the housing 11 has an opening 112 at a position different from the opening 111. An exit window 121 is attached to the opening 112. The opening 111 is an example of a first opening, and the opening 112 is an example of a second opening.

[0036] Transparent member 17 is disposed so as to reflect sunlight L11 incident through opening 112 toward illuminance sensor 16. With this configuration, transparent member 17 and illuminance sensor 16 can be disposed regardless of the position of opening 111, which increases the degree of freedom in the position and orientation of transparent member 17 and illuminance sensor 16.

[0037] 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 construed as being limited by the description of the present embodiments. The present embodiments are merely examples, and it will be understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described 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 its equivalents.

[0038] In the above embodiment, the limiting member is the transparent member 17 or the reflective member 18 that reflects sunlight L11 that is incident into the housing 11 at a specific angle toward the illuminance sensor 16. However, the limiting member may be, for example, a member that is disposed between the housing 11 and the illuminance sensor 16 and that narrows the range of the optical path of the incident sunlight.

[0039] For example, Fig. 6 shows the configuration of a HUD 50 according to a third modification. As illustrated in Fig. 6, the HUD 50 according to the third modification includes a cylindrical member 19 having openings 191 on both the top and bottom surfaces. The cylindrical member 19 is configured so that only sunlight that passes through the two openings 191 can pass through the cylindrical member 19. In other words, the cylindrical member 19 is positioned so that only sunlight L11 that enters the housing 11 at a specific angle can pass through. Note that in this example, the radii of the two openings 191 are smaller than the radius of the space connecting the two openings 191; however, the radii of the two openings 191 and the radius of the space connecting the two openings 191 may be the same; that is, the cylindrical member 19 may be a cylindrical member having a single through-hole.

[0040] With this configuration, sunlight L11 incident at a specific angle passes through the cylindrical member 19 having the through-hole 191 and enters the illuminance sensor 16. On the other hand, sunlight L12 incident at an angle other than the specific angle cannot enter the cylindrical member 19 through the through-hole 191 and therefore does not enter the illuminance sensor 16. Therefore, even with this configuration, the directionality of detection of sunlight entering the interior of the HUD 10 by the illuminance sensor 16 can be improved.

[0041] In the above embodiment, the control unit 14 is configured to detect whether the brightness detected by the illuminance sensor 16 is equal to or greater than a threshold value. However, the illuminance sensor 16 may be configured to output a brightness signal to the control unit 14 when the detected brightness is equal to or greater than the threshold value. In this case, when the control unit 14 receives the brightness signal from the illuminance sensor 16, it determines that there is a risk of heat damage to the image generation unit 13.

[0042] In the above embodiment, the light emitted from the image generation unit 13 is configured to be reflected by the concave mirror 15 and irradiated onto the windshield 21, but this is not limiting. For example, the light reflected by the concave mirror 15 may be irradiated onto a combiner (not shown) provided inside the windshield 21. The combiner may be formed, for example, of a transparent plastic disk. A portion of the light irradiated onto the combiner from the image generation unit 13 is reflected toward the occupant's viewpoint E, similar to when light is irradiated onto the windshield 21.

[0043] In the above embodiment, only the concave mirror 15 is arranged in the optical path between the image generating unit 13 and the exit window 12. However, a plane mirror may be arranged in place of the concave mirror 15 in the optical path between the image generating unit 13 and the exit window 12. Furthermore, a plane mirror, a concave mirror, or an optical element may also be arranged in the optical path between the image generating unit 13 and the exit window 12.

[0044] The configurations described in the following items also constitute part of the present disclosure. Item 1: An image projection device configured to display a predetermined image toward a vehicle occupant, the image projection device comprising: a housing; an illuminance sensor provided inside the housing; and a limiting member that limits an optical path of sunlight so that the sunlight reaches the illuminance sensor when the sunlight enters the interior of the housing through an opening of the housing at a specific angle. Item 2: The image projection device described in Item 1, wherein the limiting member has a surface that reflects sunlight incident at the specific angle toward the illuminance sensor. Item 3: The image projection device described in Item 2, wherein the limiting member is a transparent member that is positioned so that the surface of the transparent member totally reflects sunlight incident at the specific angle. Item 4: The image projection device described in Item 2, wherein the limiting member is a reflective member that has a reflective surface that reflects sunlight incident at the specific angle toward the illuminance sensor. Item 5: The image projection device described in any one of Items 2 to 4, wherein the illuminance sensor is positioned so that sunlight does not directly enter the interior of the housing. Item 6: The image projection device according to any one of Items 1 to 5, further comprising an image generation unit provided inside the housing and emitting light of the predetermined image, wherein the housing is provided with a first opening through which the light of the predetermined image is emitted and a second opening through which the sunlight is incident to be detected by the illuminance sensor.

[0045] This application is based on Japanese Patent Application No. 2023-172898 filed on October 4, 2023, the contents of which are incorporated herein by reference.

Claims

1. An image projection device configured to display a predetermined image toward an occupant of a vehicle, comprising: a housing; an illuminance sensor provided inside the housing; and a limiting member that limits the optical path of sunlight so that the sunlight reaches the illuminance sensor when the sunlight enters the interior of the housing from an opening of the housing at a specific angle.

2. The image projection device according to claim 1, wherein the limiting member has a surface that reflects sunlight incident at the specific angle toward the illuminance sensor.

3. The image projection device according to claim 2, wherein the limiting member is a transparent member, and the transparent member is arranged so as to totally reflect sunlight incident on the surface at the specific angle.

4. The image projection device according to claim 2, wherein the limiting member is a reflective member having a reflective surface that reflects sunlight incident at the specific angle toward the illuminance sensor.

5. The image projection device according to claim 2, wherein the illuminance sensor is disposed at a position where sunlight does not directly enter the inside of the housing.

6. An image projection device as described in claim 1, comprising an image generating unit provided inside the housing and emitting light of the specified image, the housing being provided with a first opening through which the light of the specified image is emitted and a second opening through which the sunlight is admitted for detection by the illuminance sensor.

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