Image projection device

Abstract

Provided is an image projection device with which it is possible to reduce double images even if the inclination angle difference of laminated glass is small. An image projection device (100) which projects a projection image to a display unit (WS) for displaying a virtual image (P) comprises an image emission unit (10) which emits image light, and projection optical units (20, 30) which, by means of the display unit (WS), form an image from the image light at a first distance from a viewpoint position, wherein: the image emission unit (10) comprises an image display unit (11) which displays an image; the image display unit (11) is such that a portion of an entire display area is a display area which displays the image; and given ASP1 = W / H as the aspect ratio between the height H and width W of the virtual image (P), and ASP2 = W1 / H1 as the aspect ratio between the height H1 and width W1 of the display area, ASP1 < ASP2.

Description

Image projection device

[0001] This invention relates to an image projection device.

[0002] Traditionally, instrument panels that display various information within vehicles have been used, typically by illuminating icons. Furthermore, with the increasing amount of information to be displayed, proposals have been made to embed image display devices within the instrument panel, or even to construct the entire instrument panel using image display devices.

[0003] However, since the instrument panel is located below the vehicle's windshield, it is undesirable for the driver or other passengers to shift their gaze downwards while driving in order to see the information displayed on the instrument panel. Therefore, image projection devices such as head-up displays (HUDs) have been proposed that project images onto the windshield so that passengers can read the information when they look ahead at the vehicle (see, for example, Patent Documents 1 and 2).

[0004] Conventional image projection devices emit light containing an image from an image projection unit, reflect the light using a free-form mirror or the like, and direct it to the occupant's viewpoint so that the image is formed in space via a display unit such as a windshield. As a result, the occupant can perceive that the image is displayed at the image formation position in the depth direction by the light incident on their viewpoint.

[0005] Japanese Patent Publication No. 2019-119248 Japanese Patent Publication No. 2019-119262

[0006] Generally, vehicle windshields use two layers of laminated glass. When image light is reflected from the inner surface on the inside of the vehicle and the outer surface on the outside, a difference in the optical path of the reflected image light occurs, resulting in a double image being projected, which reduces visibility. To reduce such double images, it has been proposed to vary the thickness of the interlayer sandwiched between the laminated glass layers in the height direction to slightly alter the tilt angle of the laminated glass. However, depending on the tilt angle of the windshield relative to the horizontal direction, the difference in the tilt angle of the laminated glass required to eliminate the double image becomes large, which increases the difficulty of manufacturing.

[0007] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and aims to provide an image projection device that can reduce double images even when the difference in the tilt angle of laminated glass is reduced.

[0008] To solve the above problems, the present invention provides an image projection device that projects a projection image onto a display unit for displaying a virtual image, comprising an image illumination unit that illuminates with image light, and a projection optical unit that forms the image light at a first distance from the viewpoint position via the display unit, wherein the image illumination unit comprises an image display unit for displaying an image, the image display unit having a display area where a part of the entire display area is the display area for displaying the image, the aspect ratio of the height H and width W of the virtual image is ASP1 = W / H, and the height H of the display area １ and width W １ The aspect ratio is ASP2 = W １ / H １ In this case, the relationship ASP2 < ASP1 is characterized by this condition.

[0009] In the image projection apparatus of the present invention, the aspect ratio ASP1 of the virtual image and the aspect ratio ASP2 of the display area are in the relationship ASP2 < ASP1. This suppresses the positional shift of the virtual image caused by image light reflected from the inside and outside of the windshield, and makes it possible to reduce double images even when the difference in the tilt angle of the laminated glass is small.

[0010] Furthermore, in one aspect of the present invention, the display area includes the area with the highest brightness among the entire display area.

[0011] Furthermore, in one aspect of the present invention, the height H of the entire display area is ２ and width W ２ The aspect ratio of ASP3 = W ２ / H ２ In this case, ASP3 < ASP2.

[0012] Furthermore, in one aspect of the present invention, the display unit is made of laminated glass in which a translucent interlayer is sandwiched between two sheets of glass.

[0013] The present invention provides an image projection device that can reduce double images even when the difference in the tilt angle of laminated glass is small.

[0014] This is a schematic diagram showing the projection of a virtual image P using the image projection device 100 according to the first embodiment. This is a schematic diagram showing the reflection of image light and backray tracing in the windshield WS according to the first embodiment. This is a schematic diagram explaining the aspect ratio of the virtual image P and the display area 11a, where Figure 3(a) shows the aspect ratio ASP2 of the display area 11a and Figure 3(b) shows the aspect ratio ASP1 of the virtual image P. This is a schematic diagram explaining the display position of the image in the image display unit 11, where Figure 4(a) is an example showing the position of the display area 11a and Figure 4(b) is an example showing the position of the high-brightness area 11b.

[0015] (First Embodiment) Hereinafter, embodiments 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 as appropriate. Figure 1 is a schematic diagram showing the projection of a virtual image P using the image projection device 100 according to this embodiment. The solid line shown in Figure 1 indicates the path of the center position of the image light. As shown in Figure 1, the image projection device 100 comprises an image irradiation 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 Figure 1, the image light projected from the image projection device 100 is reflected by the windshield WS and irradiated onto the driver's viewpoint position E (eyebox). The driver views a virtual image P formed at a predetermined distance (first distance) from the viewpoint position E on the extension of the image light that has reached the viewpoint position E.

[0016] In the image projection device 100, each part is controlled by a control unit that is connected to each part for information communication. The configuration of the control unit is not limited, but one example is one that includes a CPU (Central Processing Unit) for 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.

[0017] The image irradiation unit 10 is a part that irradiates image light including an image based on the image information from the control unit, and irradiates the image light reflected by the first mirror 20 and the second mirror 30 onto the windshield WS. The specific configuration example of the image irradiation unit 10 is not limited, and for example, a liquid crystal display device can be used.

[0018] The first mirror 20 is an optical member that reflects the image light reaching from the image irradiation unit 10 in the direction of the second mirror 30. In the example shown in FIG. 1, the first mirror 20 is shown as a flat mirror, but a concave or convex mirror may be used. Also, when the first mirror 20 is configured with a curved surface, the curvature is not limited to a constant one, and a paraboloid of revolution, an ellipsoid, a free-form surface mirror, etc. can be used. In the example shown in FIG. 1, the relative angle of the first mirror 20 with respect to the image irradiation unit 10 is fixed.

[0019] The second mirror 30 is an optical member that reflects the image light reaching from the first mirror 20 in the direction of the windshield WS. In the example shown in FIG. 1, a free-form surface mirror with a concave shape that is optically designed to project the image light as a virtual image P is shown as the second mirror 30. In the example shown in FIG. 1, the relative angle of the second mirror 30 with respect to the windshield WS is variable.

[0020] The reflecting surfaces of the first mirror 20 and the second mirror 30 are designed such that the optical path diameter expands in the direction of the driver's viewpoint position E in order to project the image light as a virtual image P through the windshield WS. Here, the expansion of the optical path diameter in the viewpoint direction includes not only the case where the optical path diameter continuously expands after reflection, but also the case where the optical path diameter shrinks and forms an image at an intermediate point and then expands.

[0021]

[0022] ​Furthermore, in Figure 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 on the image illumination unit 10, and has a predetermined area in the direction perpendicular to the direction of propagation. In addition, the image light may be reflected by the first mirror 20, reducing its optical diameter as it propagates, and an intermediate image may be formed at an intermediate imaging position F (not shown) between the first mirror 20 and the second mirror 30.

[0023] The housing 40 constitutes the outer shape of the image projection device 100 and is a housing that accommodates the other parts inside. An opening is provided at the top of the housing 40, and a dust cover is provided at this opening to seal the interior. In Figure 1, the cross-sectional shape of the housing 40 is shown as a box shape with a flat bottom and an inclined top, but the shape of the housing 40 is not limited. The material that makes up the housing 40 is not limited, and light-blocking resin materials or metal materials can be used.

[0024] The windshield WS is a visible light-transmitting part located in front of the driver's seat of the vehicle. On the inner surface of the vehicle, the windshield WS reflects the image light incident from the image projection device 100 toward the viewpoint position E, and transmits light from outside the vehicle toward the viewpoint position E, thus corresponding to the display unit in this invention. Here, an example using the windshield WS as the display unit is shown, but a combiner may be prepared as a separate display unit from the windshield WS, and the light from the image projection device 100 may be reflected toward the viewpoint. Furthermore, it is not limited to being located in front of the vehicle, but may be placed to the side or rear as long as it projects an image toward the occupant's viewpoint. The detailed structure of the windshield WS will be described later.

[0025] The virtual image P is an image that appears to be formed in space when the image light reflected by the windshield WS reaches the occupant's viewpoint position E. The position where the virtual image P is formed is determined by the combined focal length of the projection optics 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 warning images, auxiliary information related to driving such as emergency information, speed and volume indicators, and direction of travel guides.

[0026] Figure 2 is a schematic diagram showing the reflection of image light and backlight ray tracing in the windshield WS according to the present embodiment. As shown in Figure 2, the virtual image P visible from the viewpoint position E has a height H, a width W, and an aspect ratio of ASP1 = W / H. In the example shown in Figure 2, the image irradiation unit 10 has an image display unit 11, and irradiates image light in a predetermined direction from a display area la which is a part of the entire display area in the image display unit 11. Details of the display area 11a in the image display unit 11 will be described later. The image display unit 11 is a part that displays a projection image according to an image signal from the control unit. The irradiation light from the backlight is irradiated onto the projection image displayed on the image display unit 11, so that image light is irradiated from the display area 11a of the image display unit 11. The specific configuration of the image display unit 11 is not limited, but as an example, a transmissive liquid crystal display device or the like can be used.

[0027] The backlight is a part that irradiates irradiation light onto the image display unit 11, and for example, one that irradiates light by a light emitting diode (LED: Light Emitting Diode) can be used. The light irradiated by the backlight is preferably white, but a light emitting a single color such as blue, green, or red may be used. Further, the backlight is not limited to an LED, and may be a semiconductor laser, an organic EL (Electro Luminescence) element, or the like. <T

[0028] As shown in Figure 2, the windshield WS has a structure of laminated glass in which a translucent intermediate film WS is sandwiched between the glass WS on the vehicle interior side ＩＮ and the glass WS on the vehicle exterior side. ＯＵＴ The image light irradiated from the image projection device 100 is mainly reflected at the interface between the glass WS <00000l1>and air and reaches the viewpoint position E, but a part passes through the glass WS ＩＮ and the intermediate film WS ＩＮ and reaches the glass WS ｍｉｄ The image light that reaches the glass WS ＯＵＴ [[ID=2l]]is reflected at the interface between the glass WS ＯＵＴ and air and reaches the viewpoint position E. ＯＵＴ

[0028]

[0029] In Figure 2, the line of sight direction is shown by a solid line when the predetermined position of the virtual image P is viewed from viewpoint position E. Furthermore, the light reaching viewpoint position E from this line of sight direction is shown by the glass WS. ＩＮ The backlight tracing through the inner surface is shown by a dashed line, and the glass WS ＯＵＴ The solid line shows the backray tracing via the outer surface. Since the image light is reflected by the first mirror 20 and the second mirror 30 and reaches the windshield WS, the surface position S in the display area 11a is as shown in Figure 2. ｉｎ and S ｏｕｔ Light emitted from will be incident on the same viewpoint position E from the same direction. As a result, the driver will be able to see the surface position S in the same line of sight. ｉｎ The content displayed and the surface position S ｏｕｔ The displayed content appears as a superimposed double image.

[0030] Therefore, the driver is positioned at the surface position S in the display area 11a. ｉｎ and surface position S ｏｕｔ The difference in the displayed content is perceived as a difference in the double image. Therefore, surface position S ｉｎ and surface position S ｏｕｔ By reducing the difference in the displayed content, double images can be suppressed. In other words, the aspect ratio ASP2 of the display area 11a is made smaller than the aspect ratio ASP1 of the formed virtual image P, so that ASP2 < ASP1.

[0031] Figure 3 is a schematic diagram illustrating the aspect ratio of the virtual image P and the display area 11a. Figure 3(a) shows the aspect ratio ASP2 of the display area 11a, and Figure 3(b) shows the aspect ratio ASP1 of the virtual image P. Here, the height of the virtual image P visible from the viewpoint position E is H, and its width is W, so the aspect ratio ASP1 = W / H. Also, the height of the display area 11a is H. １ , width W １ Assuming the aspect ratio ASP2 = W １ / H １ As shown in Figures 3(a) and 3(b), aspect ratios ASP1 and ASP2 represent the ratio of width to height, respectively, and a larger aspect ratio indicates that the width is greater than the height, resulting in a wider image.

[0032] Therefore, aspect ratio ASP1 is greater than aspect ratio ASP2, and ASP2 < ASP1 means that the virtual image P is wider than the display area 11a, and the height of the display area 11a is compressed in the virtual image P. In this case, the surface position S on the display area 11a is... ｉｎ and surface position S ｏｕｔ The difference in displayed content is relatively smaller than when ASP2 is larger.

[0033] As an example, surface position S ｉｎ and surface position S ｏｕｔ Let's assume the case where the distance Δ = 0.1 cm on the display area 11a. Also, the virtual image P has W = 10 cm, H = 5 cm and aspect ratio ASP1 = 2, and the display area 11a is W １ = 10 cm, H １ Let's assume a case where the distance is 5 cm and the aspect ratio ASP2 = 2. In this case, ASP1 = ASP2, and the difference in distance Δ in the display area 11a is the height H. １ This corresponds to 2% of the total. In this case, at a predetermined position of the windshield WS, the glass WS ＩＮ The inner surface and glass WS ＯＵＴ The double image seen by the driver due to the reflected image light from the outer surface has a 2% shift in the height direction.

[0034] In contrast, the virtual image P has W = 10 cm, H = 5 cm, and aspect ratio ASP1 = 2, and the display area 11a is W １ = 10 cm, H １ Let's assume a height of 8 cm and an aspect ratio of ASP2 = 1.25. In this case, ASP2 < ASP1, and the difference in distance Δ in the display area 11a is the height H. １ This corresponds to 1.25% of the total. In this case, at a predetermined position of the windshield WS, the glass WS ＩＮ The inner surface and glass WS ＯＵＴ The double image seen by the driver due to the reflected image light from the outer surface has a 1.25% shift in the height direction.

[0035] Therefore, by making the aspect ratio ASP2 of the display area 11a smaller than the aspect ratio ASP1 of the virtual image P that is formed, and setting ASP2 < ASP1, the glass WS ＩＮ The inner surface and glass WS ＯＵＴ This can suppress double images caused by image light reflected from the outer surface. In addition, to correct double images, the interlayer WS ｍｉｄ Even when the thickness is varied in the height direction to create a wedge-shaped cross-section, the difference in the tilt angle of the laminated glass can be reduced because the amount of height displacement of the corrected double image is small.

[0036] As described above, in the image projection device 100 of this embodiment, the aspect ratio ASP1 of the virtual image P and the aspect ratio ASP2 of the display area 11a are in the relationship ASP2 < ASP1, which suppresses the positional shift of the virtual image P caused by image light reflected from the inside and outside of the windshield WS, and makes it possible to reduce double images even if the difference in the tilt angle of the laminated glass is small.

[0037] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figure 4. Details that overlap with the first embodiment will be omitted from the explanation. This embodiment differs from the first embodiment in that the display area 11a includes the area with the highest brightness among the entire display area of ​​the image display unit 11.

[0038] Figure 4 is a schematic diagram illustrating the image display position in the image display unit 11. Figure 4(a) is an example showing the position of the display area 11a, and Figure 4(b) is an example showing the position of the high-brightness area 11b. As shown in Figure 4(a), the entire display area, which is the entire range in which an image can be displayed in the image display unit 11, has a height H ２ , width W ２ The aspect ratio is ASP3 = W ２ / H ２ That's how it is.

[0039] In the example shown in Figure 4(a), the aspect ratio ASP3 = W ２ / H ２ Rather than ASP2 = W １ / H １The aspect ratio of ASP3 is large, so ASP2 < ASP3, and the display area 11a is wider than the entire display area. Therefore, within the entire display area, the position of the display area 11a has flexibility in the height direction, and it is possible to arbitrarily set where to display the image and set the display area 11a.

[0040] As shown in Figure 4(b), the image display unit 11 has a high-brightness region 11b in the entire display area that can be illuminated with image light at a higher brightness than other areas. The high-brightness region 11b includes the area with the highest brightness in the entire display area. Therefore, by setting the display area 11a to overlap with the high-brightness region 11b, the image light can be illuminated at the highest brightness, ensuring the brightness of the formed virtual image P and improving visibility.

[0041] The high-brightness region 11b may be intentionally configured to be a region with high brightness across the entire display area, or it may be discovered by inspection when brightness unevenness occurs unintentionally. For example, in a structure where the image display unit 11 is a transmissive liquid crystal display device and emits image light using light irradiated from a backlight, unevenness may occur 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, which includes the region with the highest brightness, by measuring the brightness distribution across the entire display area after assembling the image illumination unit 10. Furthermore, if the structure of the image illumination unit 10 is the same, there is a high probability that the position of the high-brightness region 11b will be the same, so the high-brightness region 11b may be set in the same position in image illumination units 10 having a similar structure.

[0042] As described above, in the image projection device 100 of this embodiment, the aspect ratio ASP1 of the virtual image P and the aspect ratio ASP2 of the display area 11a have the relationship ASP2 < ASP1, which suppresses the positional shift of the virtual image P caused by image light reflected from the inside and outside of the windshield WS, and makes it possible to reduce double images even if the difference in the tilt angle of the laminated glass is small. In addition, since the display area 11a includes the area with the highest brightness among the entire display area of ​​the image display unit 11, the image light can be irradiated with the highest brightness, ensuring the brightness of the formed virtual image P and improving visibility.

[0043] The present invention is not limited to the embodiments described above, 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.

[0044] This international application claims priority based on Japanese Patent Application No. 2024-157064, filed on 10 September 2024, and the entire contents of said Japanese Patent Application No. 2024-157064 are incorporated herein by reference.

[0045] The above description of specific embodiments of the present invention is provided for illustrative purposes only. It is not intended to be exhaustive or to limit the invention to the forms described. Numerous modifications and changes are possible in light of the above description, as will be obvious to those skilled in the art.

[0046] 100...Image projection device 10...Image illumination unit 11...Image display unit 11a...Display area 11b...High-brightness area 20...First mirror 30...Second mirror 40...Housing

Claims

1. An image projection device for projecting a projected image onto a display unit for displaying a virtual image, comprising: an image illumination unit for irradiating image light; and a projection optical unit for focusing the image light at a first distance from the viewpoint position via the display unit; the image illumination unit comprises an image display unit for displaying an image; the image display unit has a display area where a part of the entire display area is used for displaying the image; the aspect ratio of the height H and width W of the virtual image is ASP1 = W / H; and the height H of the display area is... １ and width W １ The aspect ratio is ASP2 = W １ / H １ An image projection device characterized in that, when this is the case, the relationship ASP2 < ASP1 holds true.

2. An image projection device according to claim 1, characterized in that the display area includes the area with the highest brightness among the entire display area.

3. An image projection device according to claim 1, wherein the height H of the entire display area ２ and width W ２ The aspect ratio of ASP3 = W ２ / H ２ An image projection device characterized in that ASP3 < ASP2.

4. An image projection device according to any one of claims 1 to 3, wherein the display unit is made of laminated glass with a translucent interlayer sandwiched between two pieces of glass.

Images