Image projection device

Abstract

To provide an image projection device capable of suppressing deterioration of visibility and glare caused by reflection of external light.SOLUTION: An image projection device (100) projects image light onto a display unit (WS) for displaying a virtual image (P), and includes an image irradiation unit (10) that irradiates the image light within a viewing range, projection optical units (20, 30) that project the image light onto the display unit (WS), and a housing unit (50) that houses the image irradiation unit (10) and the projection optical units (20, 30). The housing unit (50) is provided with a dust cover (60) at a position where the image light is extracted. The dust cover (60) is provided so as to be inclined at an angle β from a horizontal direction. and external light incident from outside is reflected by the dust cover (60) and reaches above the upper end of the viewing range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image projection device, and more particularly to an image projection device that projects a projection image onto a display unit for displaying a virtual image. [Background technology]

[0002] Conventionally, dashboards that light up icons have been used as devices for displaying various types of information inside a vehicle. As the amount of information to be displayed increases, it has been proposed to embed an image display device in the dashboard or to configure the entire dashboard with an image display device.

[0003] However, since the instrument panel is located below the vehicle's windshield, the driver must move his or her eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, a head-up display (hereinafter referred to as HUD) has been proposed that projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-119248 A [Patent Document 2] JP 2019-119262 A Summary of the Invention [Problem to be solved by the invention]

[0005] In such a conventional image projection device, image light is irradiated from an image irradiation unit, and the image light is projected onto the windshield by a projection optical unit, so that the image light reflected by the windshield reaches the driver's viewpoint. The driver visually recognizes a virtual image superimposed on the background through the windshield. In such an image projection device, a dust cover is provided below the windshield, and the image light passes through the dust cover and is projected upward from the projection optical unit onto the windshield. The image projection device has a dust cover, which can prevent dust and dirt from entering the inside of the image projection device.

[0006] However, external light such as sunlight may reach the image projection device from outside the vehicle through the windshield. Depending on the angle of incidence of the external light, the external light may be reflected by the surface of the dust cover and re-enter the windshield, eventually reaching the driver's viewpoint. Since the path of such external light to the viewpoint is similar to the path of image light to reach the driver's viewpoint, problems such as reduced visibility of virtual images and dazzling may occur.

[0007] SUMMARY OF THE PRESENT DISCLOSURE The present invention has been made in consideration of the above-mentioned problems with the conventional art, and has an object to provide an image projection device that can suppress the deterioration of visibility and the occurrence of glare caused by reflection of external light. [Means for solving the problem]

[0008] In order to solve the above problems, the image projection device of the present invention is an image projection device that projects image light onto a display unit for displaying a virtual image, and has an image irradiation unit that irradiates the image light within a range of a visual field, a projection optical unit that projects the image light onto the display unit, and a housing unit that accommodates the image irradiation unit and the projection optical unit, wherein a dust cover is provided on the housing unit at a position where the image light is extracted, and the dust cover is provided at an angle β from the horizontal direction, and external light incident from outside is reflected by the dust cover and reaches above the upper end of the visual field.

[0009] In the image projection device of the present invention, the dust cover is tilted at an angle β from the horizontal direction, and external light entering from the outside is reflected by the dust cover and reaches above the upper end of the viewing zone, thereby making it possible to suppress reduced visibility and glare due to reflection of external light.

[0010] In one aspect of the invention, the angle β of the dust cover from the horizontal direction is in the range of −45°<β<40°, with the inclination angle of the display unit from the horizontal direction being the positive direction.

[0011] In one aspect of the present invention, the angle β is in the range of −45°<β<−5°, 5°<β<40°.

[0012] In one aspect of the present invention, the dust cover is curved, and the maximum inclination angle within the plane of the dust cover is defined as the angle β.

[0013] In one aspect of the present invention, an anti-reflection layer made of a dielectric multilayer film is formed on the surface of the dust cover. Effect of the Invention

[0014] The present invention can provide an image projection device that can suppress the deterioration of visibility and the occurrence of glare caused by the reflection of external light. [Brief description 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. [Diagram 2] 10 is a schematic cross-sectional view showing the relationship between the reflection of external light LO by the dust cover 60 and the viewing area 40A. [Diagram 3] 10 is a schematic cross-sectional view showing an example of the structure of an image projection device 100 according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 given the same reference numerals, and duplicated descriptions are omitted as 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. As shown in FIG. 1, the image projection device 100 includes an image projection unit 10, a first mirror 20, a second mirror 30, a housing unit 50, and a dust cover 60. As shown in FIG. 1, the image light projected from the image projection device 100 is reflected by a windshield (display unit) WS and irradiated to a driver's viewpoint position 40. The driver visually recognizes the virtual image P formed on an extension of the optical path along which the image light is incident.

[0017] In the image projection device 100 shown in Fig. 1, 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, and the like. 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 irradiation unit 10 is a part that irradiates image light containing an image based on image information from the control unit. The specific configuration of the image irradiation unit 10 is not limited, and a conventionally known one such as a liquid crystal display device or an organic EL display device can be used. As an example, a liquid crystal display device that irradiates light from the rear side using a light emitting diode (LED: Light Emitting Diode) is used. Here, when a combination of a liquid crystal display device and a light emitting diode is used as the image irradiation unit 10, the light emitting diode corresponds to the light source unit in the present invention. Also, when an organic EL display device is used as the image irradiation unit 10, the organic EL element itself corresponds to the light source unit in the present invention. Also, a semiconductor laser may be used as the light source unit.

[0019] The first mirror 20 is an optical member that receives the image light emitted from the image projection unit 10 and reflects the image light in the direction of the second mirror 30. In the example shown in FIG. 1, a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P is shown as the first mirror 20. The second mirror 30 is an optical member that receives the image light reflected by the first mirror 20 and reflects the image light in the direction of the windshield WS. In the example shown in FIG. 1, a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P is shown as the second mirror 30. In addition, the second mirror 30 may be configured to be able to change the inclination angle with respect to the horizontal direction, and the projection direction of the image light may be changed to move the projection position of the virtual image P in the vertical direction.

[0020] The reflecting surfaces of the first mirror 20 and the second mirror 30 are designed to expand the light diameter in the driver's viewpoint direction 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. The combination of the first mirror 20 and the second mirror 30 has the function of projecting the image light through the windshield WS, and corresponds to the projection optical unit in the present invention.

[0021] The housing unit 50 is a housing that constitutes the outer shape of the image projection device 100 and accommodates the other components therein. An opening is provided at the top of the housing unit 50, and a dust cover 60 is provided at the opening to seal the inside. In FIG. 1, the cross-sectional shape of the housing unit 50 is shown as a box shape having a flat bottom and inclined sides, but the shape of the housing unit 50 is not limited. The material that constitutes the housing unit 50 is not limited, and a resin material or a metal material that blocks light can be used.

[0022] The dust cover 60 is made of a light-transmitting material and is a member disposed to cover the opening of the housing part 50. Although not shown in FIG. 1, the dust cover 60 is fixed to the housing part 50 in a structure that does not create a gap between the two, thereby preventing dirt and dust from entering the inside of the housing part 50. As will be described later, the dust cover 60 is provided at an angle β with respect to the horizontal direction of the image projection device 100 when mounted on the vehicle. The material constituting the dust cover 60 is not limited, and a known resin material or glass that transmits image light can be used.

[0023] In Fig. 1, the optical path of the image light is drawn as a straight line. However, the actual image light is displayed with 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 and travel with its light diameter reduced, and may be intermediately imaged at an intermediate imaging position F (not shown) between the first mirror 20 and the second mirror 30. When the image light reflected by the first mirror 20 is imaged at the intermediate imaging position F, the cross-sectional area through which the image light passes is minimized at the intermediate imaging position F between the first mirror 20 and the second mirror 30.

[0024] The windshield WS is a part provided in front of the driver's seat of the vehicle and transmits visible light. The windshield WS corresponds to the display unit in the present invention because the inner surface of the vehicle reflects the image light incident from the second mirror 30 toward the viewpoint and transmits light from outside the vehicle toward the viewpoint. Here, an example is shown in which the windshield WS is used as the display unit, but a combiner may be prepared as a display unit separate from the windshield WS and may reflect light from the second mirror 30 toward the viewpoint. In addition, the display unit is not limited to being located in 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.

[0025] The virtual image P is an image that is displayed as if it were formed in space when the image light reflected by the windshield WS reaches the viewpoint (eyebox) of the driver or the like. The position at which the virtual image P is formed is determined by the spread angle of the light irradiated from the image irradiating unit 10 as it travels toward the viewpoint after being reflected by the first mirror 20, the second mirror 30, and the windshield WS. The display contents of the image projected as the virtual image P include auxiliary information related to driving such as a warning image or emergency information, a volume indicator, and a driving direction guide.

[0026] 2 is a schematic cross-sectional view showing the relationship between the reflection of external light LO by dust cover 60 and viewing zone 40A. The rectangle shown in the figure is viewing zone 40A, and indicates the range in which the driver's viewpoint 40 can view virtual image P. In other words, assuming an eyebox having a predetermined area as the driver's viewpoint 40, when the second mirror 30 is rotated to change the eyebox position in the vertical direction, the upper and lower ends of the eyebox within the movable range become viewing zone 40A.

[0027] 2, it is assumed that the image projection device 100 is placed inside the dashboard 70 of a vehicle, and the dustproof cover 60 is located at a depth H from the surface of the dashboard 70. An opening is provided above the dustproof cover 60 in the dashboard 70, and image light projected from the dustproof cover 60 reaches the windshield WS through the opening. The arrows shown by dashed lines in the figure show a schematic path of external light LO entering from outside the vehicle.

[0028] Hereinafter, the horizontal direction when the vehicle is placed on a flat road surface with no incline is simply referred to as the horizontal direction, and the same direction is also referred to as the horizontal direction in the image projection device 100 mounted on the vehicle. The left direction in FIG. 2 is the front of the vehicle, the right direction is the rear of the vehicle, and the direction perpendicular to the paper surface is the width direction of the vehicle. The inclination of the external light LO entering the vehicle from the windshield WS with respect to the horizontal direction is defined as angle α. The inclination of the dust cover 60 with respect to the horizontal direction is defined as angle β. The inclination of the windshield WS with respect to the horizontal direction is defined as angle γ. Here, the inclination angle of the windshield WS with respect to the horizontal direction is defined as an angle in the positive direction.

[0029] As shown in FIG. 2, the angle between the traveling direction of the external light LO and the dust cover 60 is (α+β), and the angle between the traveling direction and the direction perpendicular to the dust cover 60 (incident angle) is 90°-(α+β). When the external light LO is reflected by the dust cover 60, the reflection angle is the same as the incident angle, 90°-(α+β). The relative angle between the windshield WS and the dust cover 60 is (γ-β). Therefore, the incident angle of the external light LO that is reflected by the dust cover 60 and reaches the windshield WS is 90°-α-2β+γ. In addition, the reflection angle of the external light LO is the same as the incident angle, 90°-α-2β+γ. Therefore, the angle between the traveling direction of the external light LO reflected by the windshield WS and the horizontal direction is α++2β-2γ.

[0030] 2, the angle between the horizontal direction at the reflection position of the external light LO on the windshield WS and the line connecting the reflection position and the upper end of the viewing area 40A is defined as θ. In this case, if the external light LO reflected on the windshield WS reaches a position above the upper end of the viewing area 40A, the external light LO reflected on the dust cover 60 will not reach the viewing point 40. Therefore, by setting (α+2β-2γ-θ) to be greater than 0° and less than 90°, it is possible to suppress the dazzle and reduced visibility caused by the external light LO reflected on the windshield WS.

[0031] As shown in FIG. 2, if the distance from the outer periphery of the opening to the position where the external light LO passes near the outer periphery of the opening of the dashboard 70 and reaches the dust cover 60 is L, the angle α that the external light LO makes with the horizontal direction is tan -1 (H / L). In order to take into consideration only the component of the external light LO reflected by the dust cover 60 that is extracted in the direction of the windshield WS, the width of the opening in the dashboard 70 is 2L or more.

[0032] Here, in a vehicle equipped with the image projection device 100, the opening width 2L of the dashboard 70 is about 120 mm to 180 mm, and the depth H to the dust cover 60 is about 45 mm to 60 mm. Therefore, the angle α of the external light LO that is reflected by the dust cover 60 and reaches the windshield WS with the horizontal direction is in the range of 27° to 48°.

[0033] In addition, in a vehicle equipped with the image projection device 100, the angle γ that the windshield WS forms with the horizontal direction is in the range of about 28° to 58°. Here, as the strictest condition, consider the case where the angle θ=0, in which the upper end of the viewing zone 40A is at the same height as the incident position of the external light LO on the windshield WS, is assumed. Substituting the range of angles α and γ, and θ=0, into the traveling angle (α+2β-2γ-θ) of the external light LO described above, the angle β that the dust cover 60 forms with the horizontal direction is in the range of -45°<β<40°. By positioning the dust cover 60 so that the angle β is in this range, the external light LO reaches above the upper end of the viewing zone 40A, making it possible to suppress the decrease in visibility and the occurrence of dazzle due to the reflection of the external light LO.

[0034] Furthermore, even if stray light does occur due to the dust cover, it is desirable that the brightness of that stray light is low. Considering the Fresnel reflectance when the refractive index of air is 1 and the refractive index of WS is 1.52, the reflectance of the mixed wave of S waves and P waves increases sharply when the angle of incidence on the windshield WS is around 50°, so it is desirable to satisfy 90°-α-2β+γ<50. From this, From the ranges of 27°<α<45° and 28°<γ<58°, the ranges of β<-5° and 5°<β are preferable. Therefore, the angle β is more preferably in the ranges of -45°<β<-5° and 5°<β<40°.

[0035] As described above, in the image projection device 100 of this embodiment, the dust cover 60 is tilted at an angle β from the horizontal direction, and external light LO incident from the outside is reflected by the dust cover 60 and reaches above the upper end of the viewing zone 40A, making it possible to suppress the reduction in visibility and the occurrence of glare due to the reflection of the external light LO.

[0036] Second embodiment Next, a second embodiment of the present invention will be described with reference to FIG. 3. Descriptions of contents overlapping with the first embodiment will be omitted. FIG. 3 is a schematic cross-sectional view showing an example of the structure of an image projection device 100 according to this embodiment. The image projection device 100 includes an image irradiation unit 10, a first mirror 20, a second mirror 30, a housing unit 50, and a dust cover 60. This embodiment differs from the first embodiment in that the dust cover 60 has a curved shape.

[0037] In Fig. 3, the tangential direction near the outer periphery of the dust cover 60 and the horizontal direction of the vehicle are indicated by dashed lines. Since the dust cover 60 is curved, the tangents near the outer periphery of the dust cover 60 are inclined at angles β1 and β2 with respect to the horizontal direction. Within the plane of the dust cover 60, the tangential direction near the center is close to the horizontal direction, and the inclination increases toward the outer periphery, so the angle of the tangential direction within the dust cover 60 is maximum near the outer periphery. In the example shown in Fig. 3, the larger of β1 and β2 is the maximum inclination angle β within the plane of the dust cover 60.

[0038] Therefore, by setting the maximum inclination angle within the plane of the dust cover 60 to angle β and setting it within the numerical range shown in the first embodiment, external light LO entering from the outside is reflected by the dust cover 60 and reaches above the upper end of the viewing zone 40A, making it possible to suppress the reduction in visibility and the occurrence of glare due to the reflection of external light LO.

[0039] 2, the dust cover 60 is disposed at a depth H within the dashboard 70, and external light LO incident with α less than 90° does not reach the outermost periphery of the dust cover 60. External light LO incident with α equal to or less than a predetermined angle is blocked by the dashboard 70 and does not reach the windshield WS even if it is reflected by the dust cover 60. Therefore, it is preferable to set β as the maximum inclination angle within the area of ​​the dust cover 60 where the external light LO is not blocked by the dashboard 70 and reaches the windshield WS.

[0040] Third embodiment Next, a third embodiment of the present invention will be described. Descriptions of contents that overlap with the first embodiment will be omitted. In this embodiment, an anti-reflection layer made of a dielectric multilayer film is formed on the surface of the dust cover 60 (not shown). As described above, by arranging the dust cover 60 at an inclination angle β with respect to the horizontal direction, the external light LO incident from the outside reaches above the upper end of the viewing zone 40A, but it is also assumed that the viewpoint position 40 may deviate from the viewing zone 40A due to a temporary change in the driver's posture, etc.

[0041] The antireflection layer is composed of a dielectric multilayer film in which dielectric films with different refractive indices are laminated in multiple layers. By appropriately setting the film thickness of each dielectric film according to the wavelength, the reflectance of a specific wavelength band in the antireflection layer can be reduced. The specific material and film thickness constituting the antireflection layer are not limited, and a dielectric multilayer film designed by a conventionally known method can be used.

[0042] In the image projection device 100 of this embodiment, an anti-reflection layer made of a dielectric multilayer film is formed on the surface of the dust cover 60, so that anti-glare and reduced visibility can be suppressed even when the viewpoint position 40 is outside the viewing zone 40A.

[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 20…1st mirror 30…2nd mirror 40…Viewpoint position 40A…Viewing area 50…Housing section 60…Dust cover 70…Dashboard

Claims

1. An image projection device that projects image light onto a display unit for displaying a virtual image, an image irradiating unit that irradiates the image light within a range of a visual field; a projection optical unit that projects the image light onto the display unit; a housing portion that houses the image irradiation portion and the projection optical portion; a dust cover is provided on the housing portion at a position where the image light is extracted; The dust cover is inclined at an angle β from the horizontal direction, An image projection device, characterized in that external light incident from the outside is reflected by the dust cover and reaches a position above an upper end of the viewing area.

2. 2. The image projection device according to claim 1, an angle β of the dust cover from the horizontal direction being in a range of −45°<β<40°, with the inclination angle of the display unit from the horizontal direction being taken as a positive direction;

3. 3. The image projection device according to claim 2, The image projection device according to the present invention is characterized in that the angle β is in the range of −45°<β<−5°, 5°<β<40°.

4. 2. The image projection device according to claim 1, 11. An image projection device, comprising: the dust cover being curved; and a maximum inclination angle within a plane of the dust cover being the angle β.

5. 5. The image projection device according to claim 1, An image projection device, characterized in that an anti-reflection layer made of a dielectric multilayer film is formed on a surface of the dustproof cover.

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