Image Projection Device

Abstract

To provide an image projection device that can be made low-profile so that it can be housed in a limited space inside a dashboard. [Solution] An image projection device (100) that projects a projection image onto a display unit (WS) for displaying a virtual image (P), comprising an image irradiation unit (10) that irradiates image light, and a projection optical unit (20, 30) that forms an image of the image light at a first distance from a viewpoint position via the display unit (WS), the projection optical unit (20, 30) having a first mirror (20) that reflects the image light irradiated from the image irradiation unit (10) and a second mirror (30) that reflects the image light reflected by the first mirror (20) towards the display unit (WS), and the sum (θ) of the angle of incidence and the angle of reflection of the image light at the first mirror (20) is an obtuse angle.

Description

[Technical Field]

[0001] The present invention relates to an image projection device. [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, because the instrument panel is located below the vehicle's windshield, passengers such as the driver must undesirably move their eyes downward while driving to view the information displayed on the instrument panel. Therefore, image projection devices such as head-up displays (hereinafter referred to as HUDs) have been proposed that project images onto the windshield so that passengers can read information when they view the area ahead of the vehicle (see, for example, Patent Documents 1 and 2).

[0004] In conventional image projection devices, an image projection unit emits light containing an image, and the light is reflected by a free-form mirror or the like, and the light reaches the viewpoint of the occupant so that the image is formed in space via a display unit such as a windshield. This allows the occupant to perceive the image as being displayed at the imaging position in the depth direction due to the light incident at the viewpoint. [Prior art documents] [Patent documents]

[0005] [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]

[0006] When an image projection device is installed in a vehicle, it is usually housed in the dashboard located below the windshield. Furthermore, the dashboard of a vehicle also houses ducts for air conditioning equipment, and in order to project image light onto the windshield, the image projection device needs to be located above the duct. However, due to various restrictions on the location of the duct, it has been difficult to secure sufficient space above the duct to place the image projection device.

[0007] SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to provide an image projection device that can be made low-profile so that it can be housed in the limited space inside the dashboard. [Means for solving the problem]

[0008] In order to solve the above problem, the image projection device of the present invention is an image projection device that projects a projection image onto a display unit for displaying a virtual image, and is equipped with an image irradiation unit that irradiates image light, and a projection optical unit that forms an image of the image light at a first distance from a viewpoint position via the display unit, wherein the projection optical unit has a first mirror that reflects the image light irradiated from the image irradiation unit, and a second mirror that reflects the image light reflected by the first mirror toward the display unit, and the sum of the incident angle and reflection angle of the image light on the first mirror is an obtuse angle.

[0009] In such an image projection device of the present invention, the sum of the incident angle and reflection angle of the image light on the first mirror is an obtuse angle, which makes it possible to reduce the distance in the height direction between the image irradiation unit and the first mirror, thereby achieving a low height.

[0010] In one aspect of the present invention, the image projection unit includes an image display unit that displays an image, and the aspect ratio of the display area that displays the image is larger than the aspect ratio of the entire display area in the image display unit.

[0011] In one aspect of the present invention, the display area includes an area with the highest brightness among the entire display area.

[0012] In one aspect of the present invention, the first mirror is located above the image projection unit.

[0013] In one aspect of the present invention, the first mirror has a fixed angle relative to the image projection unit, and the second mirror has a variable angle relative to the display unit. [Effects of the Invention]

[0014] The present invention can provide an image projection device that can be made low-profile so that it can be housed in a limited space inside a dashboard. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing projection of a virtual image P using the image projection device 100 according to the first embodiment. [Figure 2] 1 is a schematic diagram showing the positional relationship between an image projection unit 10, a first mirror 20, and a second mirror 30, and the path of image light within an image projection device 100 according to a first embodiment. [Figure 3] 3A and 3B are schematic diagrams illustrating the display position of an image on the image display unit 11, where FIG. 3A is an example showing the position of a display area 11a, and FIG. 3B is an example showing the position of a high-brightness area 11b. [Figure 4] 10 is a schematic diagram showing alignment of the image projection unit 10 when the display area 11a of the image display unit 11 is different. FIG. [Figure 5] 10 is a schematic diagram showing the positional relationship between an image projection unit 10, a first mirror 20, and a second mirror 30, and the path of image light within an image projection device 100 according to a second embodiment. FIG. 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 are denoted by the same reference numerals, and redundant description will be omitted where appropriate. FIG. 1 is a schematic diagram showing the projection of a virtual image P using an image projection device 100 according to this embodiment. The solid line in FIG. 1 indicates the path of the center position of the image light. As shown in FIG. 1, the image projection device 100 includes an image projection unit 10, a first mirror 20, a second mirror 30, and a housing 40. Here, the combination of the first mirror 20 and the second mirror 30 corresponds to the projection optical unit in the present invention. As shown in FIG. 1, the image light projected from the image projection device 100 is reflected by the windshield WS and irradiated onto the driver's viewpoint E (eyebox). The driver views a virtual image P formed at a predetermined distance (first distance) from the viewpoint E on an extension of the image light reaching the viewpoint E.

[0017] In the image projection device 100, each part is controlled by a control unit connected to each part so as to be able to communicate information with the other parts. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for performing information processing, a memory device, a recording medium, an information communication device, etc. The control unit controls the operation of each part according to a predetermined program, and sends information including an image (image information) to the image projection unit 10.

[0018] The image projection unit 10 is a part that projects image light containing an image based on image information from the control unit, and projects the image light reflected by the first mirror 20 and the second mirror 30 onto the windshield WS. There are no particular limitations on the specific configuration of the image projection unit 10, and a liquid crystal display device can be used as an example.

[0019] The first mirror 20 is an optical member that reflects the image light arriving from the image projection unit 10 toward the second mirror 30. In the example shown in FIG. 1, the first mirror 20 is a flat reflecting mirror, but a concave or convex reflecting mirror may also be used. Furthermore, when the first mirror 20 is configured with a curved surface, it is not limited to a surface with a constant curvature, and a paraboloid of revolution, an ellipsoid, a free-form surface mirror, or the like may be used. In the example shown in FIG. 1, the relative angle of the first mirror 20 with respect to the image projection unit 10 is fixed.

[0020] The second mirror 30 is an optical member that reflects the image light arriving from the first mirror 20 toward the windshield WS. In the example shown in Fig. 1, the second mirror 30 is a free-form mirror with a concave shape that has been optically designed to project the image light as a virtual image P. In the example shown in Fig. 1, the angle of the second mirror 30 relative to the windshield WS is variable.

[0021] The reflecting surfaces of the first mirror 20 and the second mirror 30 are designed to expand the light diameter in the direction of the driver's viewpoint E in order to project the image light as a virtual image P through the windshield WS. Here, the expansion of the light diameter in the viewpoint direction includes not only the case where the light diameter expands consistently after reflection, but also the case where the light diameter shrinks and expands after forming an image at an intermediate point.

[0022] The projection optical unit, which is composed of a combination of the first mirror 20 and the second mirror 30, functions as an optical element that projects the image light irradiated from the image irradiation unit 10 onto the driver's viewpoint position E through the windshield WS and forms an image of the image light at a first distance from the viewpoint position E.

[0023] 1, the optical path of the image light is depicted as a single straight line. However, the actual image light is displayed in a predetermined area in the image projection unit 10, and has a predetermined area in a direction perpendicular to the traveling direction. The image light may be reflected by the first mirror 20, its light diameter reduced as it travels, and may form an intermediate image at an intermediate imaging position F (not shown) between the first mirror 20 and the second mirror 30.

[0024] The housing 40 is a housing that forms the outer shape of the image projection device 100 and accommodates the other components inside. An opening is provided at the top of the housing 40, and a dustproof cover is provided over the opening to seal the interior. In FIG. 1, the cross-sectional shape of the housing 40 is shown as a box shape with a flat bottom and a sloping top, but the shape of the housing 40 is not limited. The material that makes up the housing 40 is not limited, and a resin material or a metal material that blocks light can be used.

[0025] 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 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.

[0026] The virtual image P is an image that appears as if it were formed in space when image light reflected by the windshield WS reaches the passenger's viewpoint E. The position at which the virtual image P is formed is determined by the combined focal length of the projection optical unit included in the image projection device 100 and the windshield WS. The content of the image projected as the virtual image P may include images to alert drivers, auxiliary information related to driving such as emergency information, speed and volume indicators, and driving direction guides.

[0027] FIG. 2 is a schematic diagram showing the positional relationship among the image projection unit 10, the first mirror 20, and the second mirror 30 and the path of image light within the image projection device 100 according to this embodiment. In the example shown in FIG. 2, the image projection unit 10 has an image display unit 11, and projects image light in a predetermined direction from a display area 11a, which is a portion of the entire display area of ​​the image display unit 11. The display area 11a of the image display unit 11 will be described in detail later. The image display unit 11 is a part that displays a projected image in response to an image signal from the control unit. The projected image displayed on the image display unit 11 is irradiated with light from a backlight, whereby the image light is projected from the display area 11a of the image display unit 11. The specific configuration of the image display unit 11 is not limited, but a transmissive liquid crystal display device or the like can be used as an example.

[0028] The backlight is a part that irradiates light onto the image display unit 11, and may be, for example, a light emitting diode (LED) that emits light. The light emitted by the backlight is preferably white, but it may also be a light that emits a single color such as blue, green, or red. The backlight is not limited to an LED, and may also be a semiconductor laser, an organic EL (Electro Luminescence) element, or the like.

[0029] 2, the first mirror 20 is disposed above the image projection unit 10 and the second mirror 30. Therefore, the image projection unit 10 projects image light obliquely upward at a predetermined angle, and the image light incident on the first mirror 20 is reflected obliquely downward before reaching the second mirror 30. The image light that reaches the second mirror 30 is reflected and travels toward the windshield WS. At this time, the sum of the incident angle and reflection angle of the image light at the first mirror 20 is θ degrees, which is an obtuse angle of θ>90°.

[0030] By making the sum θ of the incident angle and reflection angle of the image light on the first mirror 20 an obtuse angle, it is possible to reduce the height of the housing 40 by reducing the distance in the height direction while ensuring the optical path length from the image irradiation unit 10 to the first mirror 20, thereby reducing the height of the entire image projection device 100. Therefore, even if a duct or the like is housed inside the dashboard of the vehicle, it is easier to ensure space for arranging the image projection device 100, improving design freedom.

[0031] Furthermore, by arranging the first mirror 20 above the image projection unit 10 and the second mirror 30, the angle of incidence of the image light reflected by the first mirror 20 onto the second mirror 30 can be made small with respect to the normal direction of the reflecting surface of the second mirror 30. This reduces distortion of the image light incident on the second mirror 30, and improves the degree of freedom in the optical design of the second mirror 30.

[0032] 3A and 3B are schematic diagrams illustrating the display position of an image on the image display unit 11, with Fig. 3A being an example showing the position of the display area 11a and Fig. 3B being an example showing the position of the high-brightness area 11b. As shown in Fig. 3A, the entire display area, which is the entire range in which an image can be displayed on the image display unit 11, has a height H and a width W, with an aspect ratio of H:W.

[0033] Display area 11a is a portion of the entire display area, and has a height of h1 and a width of w1, giving it an aspect ratio of h1:w1. In the example shown in Figure 3(a), the aspect ratio of h1:w1 is larger than the aspect ratio of H:W, making display area 11a wider than the entire display area. Therefore, the position of display area 11a has a degree of freedom in the height direction within the entire display area, and it is possible to arbitrarily set the position at which an image is displayed and display area 11a is set.

[0034] As shown in FIG. 3(b), the image display unit 11 has a high-brightness region 11b that can irradiate image light with higher brightness than other regions in the entire display area. The high-brightness region 11b includes the region with the highest brightness in the entire display area. Therefore, by positioning the display area 11a so that it overlaps with the high-brightness region 11b, the image light can be irradiated with the highest brightness, ensuring the brightness of the formed virtual image P and improving visibility.

[0035] The high-brightness region 11b may be intentionally configured as a high-brightness region in the entire display area, or may be detected by inspection when unintentional brightness unevenness occurs. One example is when the image display unit 11 is a transmissive liquid crystal display device that emits image light using light irradiated from a backlight, and unevenness occurs in the light distribution of the irradiated light or the light transmission characteristics of the liquid crystal display device. Even in the case of such unintentional brightness unevenness, it is possible to identify the high-brightness region 11b containing the brightest region by measuring the brightness distribution in the entire display area after assembling the image projection unit 10. Furthermore, if the structure of the image projection unit 10 is the same, the position of the high-brightness region 11b is likely to be the same, so the high-brightness region 11b may be set in the same position in image projection units 10 having similar structures.

[0036] FIG. 4 is a schematic diagram illustrating the alignment of the image projection unit 10 when the display area 11a of the image display unit 11 is different. In FIG. 4, solid and dashed lines indicate exemplary arrangements of the image projection units 10 in which the position of the display area 11a within the entire display area is different. The left-right direction in FIG. 4 corresponds to the height H direction of the image display unit 11 shown in FIGS. 3(a) and 3(b). The two image projection units 10 shown by solid and dashed lines in FIG. 4 have different positions of the high-brightness area 11b and the display area 11a in the height direction within the entire display area. However, by adjusting the position of the image projection unit 10 within the housing 40 so that the relative position of the display area 11a with respect to the first mirror 20 is the same, image projection can be performed without changing the positions of the first mirror 20 and the second mirror 30.

[0037] Here, because display area 11a overlaps with high-brightness area 11b, which includes the area with the highest brightness within the entire display area of ​​image display unit 11, it is possible to irradiate image light with the highest brightness simply by changing the position of image projection unit 10. Furthermore, because the sum θ of the angle of incidence and the angle of emission of image light at first mirror 20 is an obtuse angle, even if image projection unit 10 is moved left or right in the figure, it is unlikely to interfere with the optical path of image light from first mirror 20 to second mirror 30, improving the degree of freedom in design.

[0038] As described above, in the image projection device 100 of this embodiment, the sum θ of the incident angle and reflection angle of the image light at the first mirror 20 is an obtuse angle, which makes it possible to reduce the distance in the height direction between the image irradiation unit 10 and the first mirror 20, thereby achieving a low height.

[0039] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 5. Description of content that overlaps with the first embodiment will be omitted. Fig. 5 is a schematic diagram showing the positional relationship between the image projection unit 10, first mirror 20, and second mirror 30 and the path of image light within the image projection device 100 according to this embodiment.

[0040] In the example shown in FIG. 5, the first mirror 20 is disposed below the image projection unit 10 and the second mirror 30. Therefore, the image projection unit 10 projects image light obliquely downward at a predetermined angle, and the image light incident on the first mirror 20 is reflected obliquely upward to reach the second mirror 30. The image light that reaches the second mirror 30 is reflected and travels toward the windshield WS. At this time, the sum of the angle of incidence and the angle of reflection of the image light at the first mirror 20 is θ degrees, which is an obtuse angle of θ>90°. The image projection unit 10 also includes an image display unit 11, and the image light is projected from a display area 11a that is a part of the image display unit 11.

[0041] In this embodiment, too, since the sum θ of the incident angle and reflection angle of the image light at the first mirror 20 is an obtuse angle, it is possible to reduce the height of the housing 40 by reducing the vertical distance while maintaining the optical path length from the image irradiation unit 10 to the first mirror 20, thereby reducing the height of the entire image projection device 100.

[0042] Furthermore, by overlapping display region 11a with high-brightness region 11b, which includes the region with the highest brightness among the entire display region of image display unit 11, it is possible to irradiate image light with the highest brightness simply by changing the position of image projection unit 10. Furthermore, because the sum θ of the incident angle and emission angle of image light at first mirror 20 is an obtuse angle, even if image projection unit 10 is moved left or right in the figure, it is unlikely to interfere with the optical path of image light from first mirror 20 to second mirror 30, improving design freedom.

[0043] 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]

[0044] 100...Image projection device 10...Image irradiation unit 11...Image display section 11a...display area 11b...High brightness area 20...1st mirror 30...Second mirror 40…Housing

Claims

1. An image projection device that projects a projection image onto a display unit that displays a virtual image, an image irradiating unit that irradiates image light; a projection optical unit that forms an image of the image light at a first distance from a viewpoint position via the display unit; the projection optical unit includes a first mirror that reflects the image light irradiated from the image irradiating unit, and a second mirror that reflects the image light reflected by the first mirror toward the display unit; an image projection device, wherein the sum of the incident angle and the reflection angle of the image light on the first mirror is an obtuse angle;

2. 2. The image projection device according to claim 1, the image projection unit includes an image display unit that displays an image, An image projection device, wherein an aspect ratio of a display area for displaying the image is greater than an aspect ratio of the entire display area of ​​the image display unit.

3. 3. The image projection device according to claim 2, An image projection device, wherein the display area includes an area with the highest brightness among the entire display area.

4. 2. The image projection device according to claim 1, The image projection device, wherein the first mirror is located above the image projection unit.

5. 5. The image projection device according to claim 1, the first mirror has a fixed angle relative to the image projection unit, The image projection device is characterized in that the second mirror has a variable angle relative to the display unit.

Images