Image projection apparatus

Abstract

The invention provides an image projection device capable of ensuring visibility even when polarized sunglasses and the like are used. An image projection device (100) for projecting a projection image onto a display unit (WS) for displaying a virtual image, the image projection device (100) being provided with: an image irradiation unit (10) for irradiating image light (L1); a projection optical unit (20) that projects image light (L1) to a display unit (WS) as a projection image, the image light (L1) irradiated from the projection optical unit (20) including P-polarized light with respect to the display unit (WS), and the image projection device (100) is provided with a polarized light adjustment unit (30) that adjusts the polarized light direction of the image light (L1).

Description

Technical Field

[0001] The present invention relates to an image projection device, and more particularly to an image projection device that reflects irradiation light from an image irradiation unit to allow the light to reach a viewpoint. Background Art

[0002] Conventionally, as a device for displaying various information in a vehicle, an instrument panel with illuminated display icons has been used. In addition, as the amount of information displayed increases, a scheme has been proposed to embed an image display device in the instrument panel so that the image display device constitutes the entire instrument panel.

[0003] However, since the instrument panel is located below the vehicle's front windshield (windshield), the driver must shift their gaze downward while driving in order to view the information displayed on the instrument panel, which is not ideal. Therefore, a head-up display (HUD) has been proposed that projects an image onto the front windshield, allowing the driver to read the information while visually viewing the area ahead of the vehicle (see, for example, Patent Documents 1 and 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-119248

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-119262 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] However, in conventional image projection devices, light reflected from the windshield tends to have a low reflectivity for the P-polarized light component and a high reflectivity for the S-polarized light component. Therefore, the polarization direction of the illumination light emitted from the image illumination unit is set to S-polarized light relative to the windshield. As a result, the illumination light reaching the viewpoint is exclusively S-polarized light, excluding P-polarized light.

[0010] However, when driving in environments with strong external light or on snowy roads, passengers may sometimes wear polarized sunglasses and observe the exterior through the windshield. In this case, since light reflected from objects outside the vehicle is also S-polarized light, the polarized sunglasses are set to block S-polarized light and transmit P-polarized light. Consequently, for passengers wearing polarized sunglasses, the S-polarized light reflected from the windshield is blocked by the polarized sunglasses, making it difficult to visually recognize the image formed by the incident light.

[0011] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an image projection device that can ensure visibility even when polarized sunglasses or the like are used.

[0012] Technical solutions to technical problems

[0013] In order to solve the above-mentioned technical problems, the image projection device of the present invention projects a projection image onto a display unit for displaying a virtual image, and is characterized in that the image projection device includes: an image irradiation unit that irradiates image light; a projection optical unit that projects the image light onto the display unit as the projected image; the image light irradiated from the projection optical unit includes P-polarized light relative to the display unit, and the image projection device includes a polarization adjustment unit that adjusts the polarization direction of the image light.

[0014] In such an image projection device of the present invention, since the polarization direction of the image light is adjusted by the polarization adjustment unit, the distribution of the polarization direction of the image light can be set to an appropriate distribution according to the curved surface shape of the display unit, and visual recognition can be ensured even when polarized sunglasses are used.

[0015] In one aspect of the present invention, the polarization adjusting section is a polarizing plate that transmits polarized light in a predetermined direction, and the predetermined direction intersects with a polarization direction of the image light emitted from the projection optical section.

[0016] In one aspect of the present invention, the polarization adjusting section is a polarization compensation plate that changes the polarization direction according to an incident angle.

[0017] Furthermore, in one aspect of the present invention, the polarization compensation plate is arranged in a curved manner.

[0018] In one aspect of the present invention, the polarization adjustment unit is provided between the projection optical unit and the display unit.

[0019] In one aspect of the present invention, the polarization adjusting unit adjusts the polarization direction of at least a portion of the image light emitted from the projection optical unit within a range of 30 degrees.

[0020] Effects of the Invention

[0021] The present invention can provide an image projection device that can ensure visibility even when polarized sunglasses or the like are used. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a schematic diagram showing the configuration of the image projection apparatus 100 according to the first embodiment.

[0023] Figure 2 : is a graph schematically showing an example of the reflection characteristics of P-polarized light and S-polarized light in the polarized light reflecting portion 40 .

[0024] Figure 3 Schematic diagram showing changes in the incident angle and polarization direction of the image light L1 in the polarization adjusting section 30 .

[0025] Figure 4 It is a schematic diagram showing the configuration of an image projection apparatus 110 according to the second embodiment.

[0026] Figure 5 It is a schematic diagram showing the configuration of an image projection device 120 according to the third embodiment. DETAILED DESCRIPTION

[0027] (First embodiment)

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same or equivalent components, members, and processes shown in the various drawings are denoted by the same reference numerals, and duplicate descriptions are omitted as appropriate. Figure 1 Schematic diagram showing the configuration of the image projection apparatus 100 according to this embodiment.

[0029] like Figure 1 As shown in FIG. 1 , the image projection device 100 includes an image irradiation unit 10, a free-form surface mirror 20, and a polarization adjustment unit 30. The free-form surface mirror 20 constitutes the projection optical unit of the present invention. Figure 1 , solid arrows schematically indicate representative optical paths of image light L1 emitted from the image irradiation unit 10 and external light L0, such as sunlight. Furthermore, a vehicle windshield WS and a polarized light reflecting unit 40 are provided outside the image projection apparatus 100, and the driver or the like visually recognizes an image based on the image light L1 from a viewpoint e via the polarized light reflecting unit 40.

[0030] The image irradiation unit 10 is a device that emits illumination light (image light) L1 containing image information in response to a signal containing image information supplied from an information processing unit (not shown). The image light L1 emitted from the image irradiation unit 10 enters the free-form surface mirror 20. Examples of the image irradiation unit 10 include liquid crystal displays, organic EL displays, micro-LED displays, DMDs (digital micro-mirror devices), and projectors using laser light sources. As indicated by the double arrows in the figure, the image light L1 emitted from the image irradiation unit 10 is configured to include light that is P-polarized relative to the windshield WS. When the image light L1 from the image irradiation unit 10 is polarized in a specific direction, the orientation of the display surface of the image irradiation unit 10 is set so that its polarization plane is P-polarized relative to the windshield WS. Examples of the image irradiation unit 10 that emits the specific polarized image light L1 include liquid crystal displays, projectors using laser light sources, and reflective liquid crystal projectors.

[0031] The free-curved mirror 20 is a mirror for receiving the image light L1 emitted from the image irradiation unit 10 and reflecting it toward the windshield WS. The shape of the reflecting surface of the free-curved mirror 20 is a free-curved surface whose curvature is not constant but changes in two dimensions. Figure 1 In FIG, a concave mirror is shown as the shape of the free-form mirror 20, but a convex mirror or a flat mirror can also be used. Figure 1 , an example in which the projection optical section is constituted by the free-form surface mirror 20 is shown. However, a plurality of reflecting mirrors may be used to repeatedly reflect the image light L1 and irradiate the windshield WS.

[0032] The polarization adjustment unit 30 is an optical component that adjusts the polarization direction of the image light L1. The specific structure of the polarization adjustment unit 30 is not limited; a polarization compensation plate that changes the polarization direction according to the incident angle of the light can be used. The polarization compensation plate is not limited in composition; known materials and structures can be used. For example, WV film or a holographic optical element (HOE) manufactured by Fujifilm can be used.

[0033] exist Figure 1 In the example shown, a polarization compensation plate is used as the polarization adjustment unit 30, and the polarization compensation plate is bent. As a result, the incident angle of the image light L1 on the polarization compensation plate within the irradiation area has a predetermined distribution, and the polarization direction of the image light L1 also has a predetermined distribution within the irradiation area. Figure 1, an example is shown in which the polarization adjusting unit 30 is disposed between the free-form surface mirror 20 and the windshield WS. However, the position of the polarization adjusting unit 30 is not limited, and the polarization adjusting unit 30 may be disposed between the free-form surface mirror 20 and the image irradiation unit 10. In order to determine the final polarization direction distribution of the image light L1 projected from the image projection device 100, the polarization adjusting unit 30 is preferably disposed at the emission position of the image light L1 in the image projection device 100.

[0034] The windshield WS is provided in front of the driver's seat of the vehicle and transmits light from outside the vehicle in the direction of the viewpoint e. In addition, the windshield WS transmits at least visible light from outside the vehicle. Therefore, when external light L0 such as sunlight enters the vehicle from above, part of the external light L0 also reaches the free-form surface mirror 20. In addition, a polarized light reflecting portion 40 is provided inside the windshield WS. Figure 1 In the figure, the cross-sectional shape of the windshield WS is depicted as a flat plate for simplicity. However, in an actual vehicle, it is composed of curved surfaces having curvature in the vertical and horizontal directions. Furthermore, the area of ​​the windshield WS onto which the image light L1 is projected is located on the driver's seat side, offset from the horizontal center of the windshield WS, and is composed of a horizontally asymmetric curved surface.

[0035] The polarized light reflecting portion 40 is an optical component provided inside the windshield WS, and has optical characteristics of low reflectivity of the S-polarized light component of the incident light and high reflectivity of the P-polarized light component. Figure 1 In the example shown, the polarized light reflecting portion 40 is formed in a substantially flat film shape and is embedded in the windshield WS. Figure 1 , an example is shown in which the polarized light reflecting portion 40 is provided on a portion of the windshield WS, but the polarized light reflecting portion 40 may be provided on the entire surface of the windshield WS.

[0036] Figure 2 This is a graph schematically showing an example of the reflection characteristics of P-polarized light and S-polarized light in the polarized light reflecting portion 40. The horizontal axis of the graph represents the direction perpendicular to the surface of the polarized light reflecting portion 40 as 0 degrees, and the angle inclined from 0 degrees is represented as the incident angle. In addition, the vertical axis of the graph represents the reflectivity of polarized light (P-polarized light) in the in-plane direction of the polarized light reflecting portion 40 including the 0-degree direction and the incident direction of light as a solid line, and the reflectivity of S-polarized light perpendicular to the P-polarized light as a dotted line. Figure 2 As shown, the polarized light reflecting portion 40 has an optical characteristic that the reflectivity of P polarized light is high and the reflectivity of S polarized light is low relative to the windshield WS. In addition, the reflectivity of P polarized light is low when the incident angle is small, and the reflectivity increases as the incident angle increases. Figure 2As shown, the polarized light reflecting portion 40 has a high reflectivity of 75% or more for P polarized light and a low reflectivity of about 10% for S polarized light near the Brewster angle of the windshield WS. Figure 2 As the polarized light reflecting portion 40 having the optical characteristics shown, a polarized light reflecting film (WCF-PVB) manufactured by 3M or a polarized light reflecting film described in Japanese Patent Application Publication No. 2006-512622 can be used.

[0037] In addition, Figure 1 The figure shows an example of a display unit with a polarized light reflecting unit 40 installed inside the windshield WS. However, a separate combiner may be provided as the display unit, with the polarized light reflecting unit 40 installed inside the combiner to reflect light from the free-form mirror 20 toward the viewpoint. Furthermore, the display unit is not limited to being located in front of the vehicle; it may also be located to the side or rear, as long as it projects an image toward the passenger's viewpoint e. The viewpoint e is the eye (eye movement area) of the driver or passenger of the vehicle. Image light L1 enters the eye movement area, causing the light to reach the retina, and the driver or passenger visually perceives the resulting virtual image.

[0038] A virtual image is displayed spatially when image light L1 reflected by the polarized light reflecting unit 40 reaches the driver's or other person's viewpoint (eye movement range) e. The position of the virtual image is determined by the angle of spread of light emitted from the image irradiation unit 10 as it travels in the viewpoint direction after being reflected by the free-form mirror 20 and the polarized light reflecting unit 40. At this point, the driver or passenger perceives the virtual image as being located at a position farther from the windshield WS. The position of the virtual image depends primarily on the synthetic focal length of the projection optical unit. Even though the windshield WS is curved rather than flat, the effect of the windshield WS's optical power is negligible due to its larger radius of curvature than the free-form mirror 20.

[0039] like Figure 1 As shown, the image light L1 from the image irradiation unit 10 includes P polarized light relative to the windshield WS, and the image light L1 reflected by the free-form mirror 20 also includes P polarized light. In addition, the polarization direction of a portion of the image light L1 is changed by the polarization adjustment unit 30, but it mainly includes P polarized light. Therefore, the image light L1 including P polarized light passes through the polarization adjustment unit 30 and reaches the polarization reflection unit 40. Figure 2 As shown, the polarized light reflecting unit 40 has a high reflectivity for P-polarized light, so the P-polarized light component of the image light L1 is also well reflected and reaches the viewpoint e. Therefore, a virtual image is projected using P-polarized light, allowing good visual recognition even when the passenger wears polarized sunglasses.

[0040] In addition, the incident angle of the image light L1 with respect to the windshield WS is preferably set to the Brewster angle. At the Brewster angle, the P-polarized light of the image light L1 is hardly reflected by the surface of the windshield WS and can enter the interior of the glass constituting the windshield WS. Figure 2 As shown, the polarized light reflecting portion 40 has a high reflectivity even at a Brewster angle of approximately 50 degrees. Therefore, the brightness of the image light L1 reflected by the polarized light reflecting portion 40 is higher than the brightness of the image light L1 slightly reflected by the surface of the windshield WS. This can prevent the P-polarized light of the image light L1 from being reflected by both the surface of the windshield WS and the polarized light reflecting portion 40, thereby preventing the double visual perception of a virtual image.

[0041] In addition, if Figure 1 As shown, external light L0, such as sunlight, enters from above the windshield WS. Here, the external light L0 entering from outside the vehicle is unpolarized light, containing components of all polarization directions. The P-polarized light component is reflected toward the exterior of the vehicle by the polarized light reflecting unit 40, while only the S-polarized light component passes through the windshield WS and reaches the free-form surface mirror 20. Therefore, the P-polarized light component in the external light L0 is blocked by the polarized light reflecting unit 40, reducing the amount of light reaching the image irradiation unit 10. This reduces the temperature rise caused by the external light L0 reaching the image irradiation unit 10, thereby preventing degradation of the image irradiation unit 10.

[0042] As described above, the windshield WS has curvature in both the vertical and horizontal directions, and the area illuminated by the image light L1 is located off-center from the windshield WS. Specifically, the inclination of the image light L1 on the surface of the windshield WS and the area illuminated by the polarized light reflector 40 differ slightly within the plane. When image light L1, all polarized in the same direction, is projected onto these surfaces with different inclinations, the polarization components are separated according to the inclination of the incident position, resulting in a P-polarized light component and an S-polarized light component. This separation of the polarization components based on the incident position of the image light L1 causes the S-polarized light component to be reflected by the surface of the windshield WS, while the P-polarized light component reflected by the polarized light reflector 40 is reduced, resulting in a double virtual image and poor visual recognition.

[0043] Therefore, in this embodiment, the polarization adjusting unit 30 is curved to achieve a polarization direction that matches the tilt angle between the windshield WS and the polarization reflecting unit 40. This modifies the polarization distribution of the image light L1 that passes through the polarization adjusting unit 30. Modifying the polarization distribution of the image light L1 here means adjusting the polarization direction within a range of 30 degrees for at least a portion of the image light L1 emitted from the free-form mirror 20. The shape of the windshield WS varies depending on the vehicle model and individual differences. Therefore, by adjusting the polarization direction using the polarization adjusting unit 30, image light L1 with an appropriate polarization distribution corresponding to the vehicle model and individual differences can be projected onto the windshield WS. Furthermore, by providing the polarization adjusting unit 30 at the emission position of the image light L1 in the image projection device 100, alignment with respect to the tilt of the windshield WS can be performed at the end of the assembly process for mounting the image projection device 100 on the vehicle.

[0044] Figure 3 is a schematic diagram showing changes in the incident angle and polarization direction of the image light L1 in the polarization adjustment unit 30. Figure 3 As shown, a curved polarization compensation plate is used as the polarization adjusting section 30. The arrow in the figure indicates the traveling direction of the image light L1, and the double arrow in the figure schematically indicates the polarization direction of the image light L1.

[0045] like Figure 3 As shown, in the polarization adjustment unit 30, since the polarization compensation plate is bent, the incident angle varies depending on the position of the image light L1. In the area of ​​the image light L1 that is incident vertically on the polarization compensation plate, P polarization is maintained even when passing through the polarization compensation plate. With this P polarization as a reference, the conversion of the polarization direction at other positions is described. In the area that is incident at an oblique angle relative to the normal direction of the polarization compensation plate, a part of the P polarization component is converted into an S polarization component according to the oblique angle, and the polarization direction becomes a polarization direction containing a P polarization component and an S polarization component that are different from the reference P polarization direction. Figure 3 , at the position shown on the left, after the P-polarized light passes through the polarization compensation plate, the polarization direction is P1+S1, and at the position shown on the right, the polarization direction is P2+S2.

[0046] Therefore, the image light L1 transmitted through the polarization adjustment unit 30 has a distribution of polarization directions that differ depending on the position within the plane of the illuminated area. This distribution of polarization directions is determined by the optical properties and curved shape of the polarization compensation plate serving as the polarization adjustment unit 30. Therefore, by aligning the curved shape of the polarization compensation plate with the tilt direction of the windshield WS within the illuminated area of ​​the image light L1, the tilt direction of the windshield WS and the polarization direction of the image light L1 can be appropriately set at each position.

[0047] exist Figure 3 In the example shown, of the image light L1 that is perpendicularly incident on and transmitted through the polarization compensation plate, only the reference P-polarized light reaches the windshield WS, and only the P-polarized light component is present in the direction oblique to the windshield WS. The direction of the reference P-polarized light at this position is the in-plane polarization that includes the incident direction of image light L1 and the normal direction to the windshield WS.

[0048] Image light L1, incident on the polarization compensation plate at a predetermined tilt angle, reaches the windshield WS with a polarization direction (P1+S1 or P2+S2), which differs from the reference P-polarized light. At this position, the normal to the windshield WS has a component tilted more horizontally than the position at which the reference P-polarized light enters, canceling out the S1 and S2 components of the P1+S1 or P2+S2 polarization directions. Therefore, at this position, the relationship between the normal to the windshield WS and the polarization direction of the image light L1 is solely the P-polarized component (P1 or P2). This suppresses reflection of the S-polarized light component from the surface of the windshield WS, allowing the P-polarized light component to enter the windshield WS at the Brewster's angle and be effectively reflected by the polarized light reflecting unit 40.

[0049] As described above, in the image projection device 100 of this embodiment, the polarization direction of the image light L1 is adjusted using the polarization adjustment unit 30, so that the distribution of the polarization direction of the image light L1 can be set to an appropriate distribution according to the curved surface shape of the windshield WS, and visual recognition can be ensured even when polarized sunglasses are used.

[0050] (Second embodiment)

[0051] Next, use Figure 4 A second embodiment of the present invention will be described, with the description of the contents overlapping with the first embodiment omitted. Figure 4 Schematic diagram showing the structure of the image projection device 110 of this embodiment. Figure 4As shown, the image projection device 110 includes an image irradiation unit 10, a free-form mirror 20, a polarization adjustment unit 30, and a half-wave plate 50. In this embodiment, the half-wave plate 50 is disposed between the image irradiation unit 10 and the free-form mirror 20.

[0052] Half-wave plate 50 is placed on the optical path of illumination light (image light) L1. It is an optical component that produces a phase difference of half a wavelength between its orthogonal fast and slow axes. The fast axis of half-wave plate 50 is positioned 45 degrees out of phase with each of the S- and P-polarized components of image light L1.

[0053] like Figure 4 As shown, in the image projection device 110 of this embodiment, image light L1 from the image irradiation unit 10 becomes S-polarized light with respect to the windshield WS. In the half-wave plate 50, the polarization direction of the S-polarized light is 45 degrees different from the fast axis. Therefore, image light L1 that passes through the half-wave plate 50 becomes P-polarized light.

[0054] The image light L1 converted into P polarized light by the half-wave plate 50 is reflected by the free-form mirror 20 and passes through the polarization adjustment unit 30, and is projected onto the windshield WS. Figure 4 As shown, the image light L1 that has passed through the polarization adjusting unit 30 is converted into a polarization distribution within the irradiation area and reaches the windshield WS. Therefore, the S-polarized light component included in the image light L1 is canceled by the horizontal tilt angle at each position of the windshield WS.

[0055] In the image projection device 110 of this embodiment, the polarization direction of the image light L1 is also adjusted by the polarization adjustment unit 30, so that the distribution of the polarization direction of the image light L1 can be set to an appropriate distribution according to the curved surface shape of the windshield WS, and visual recognition can be ensured even when using polarized sunglasses, etc.

[0056] (Third embodiment)

[0057] Next, use Figure 5 A third embodiment of the present invention will be described, with the description of the contents overlapping with the first embodiment omitted. Figure 5 Schematic diagram showing the structure of the image projection device 120 of this embodiment. Figure 5 As shown, the image projection device 120 includes an image irradiation unit 10, a free-form mirror 20, a polarization adjustment unit 30, and a half-wave plate 50. In this embodiment, the half-wave plate 50 is disposed between the free-form mirror 20 and the polarization adjustment unit 30.

[0058] like Figure 5As shown, in the image projection device 120 of this embodiment, image light L1 from the image irradiation unit 10 is S-polarized light with respect to the windshield WS. The S-polarized image light L1 is reflected by the free-form surface mirror 20 and reaches the half-wave plate 50. In the half-wave plate 50, the polarization direction of the S-polarized light is 45 degrees different from the fast axis. Therefore, the image light L1 that passes through the half-wave plate 50 becomes P-polarized light.

[0059] The image light L1 converted into P polarized light by the half-wave plate 50 passes through the polarization adjustment unit 30 and is projected onto the windshield WS. Figure 5 As shown, the image light L1 that has passed through the polarization adjusting unit 30 is converted into a polarization distribution within the irradiation area and reaches the windshield WS. Therefore, the S-polarized light component included in the image light L1 is canceled by the horizontal tilt angle at each position of the windshield WS.

[0060] In the image projection device 120 of this embodiment, the polarization direction of the image light L1 is also adjusted by the polarization adjustment unit 30, so that the distribution of the polarization direction of the image light L1 can be set to an appropriate distribution according to the curved surface shape of the windshield WS, and visual recognition can be ensured even when polarized sunglasses are used.

[0061] (Fourth embodiment)

[0062] Next, a fourth embodiment of the present invention will be described. Details overlapping with the first embodiment will be omitted. While the first through third embodiments illustrate examples using a polarization compensation plate as the polarization adjustment unit 30, a polarization plate that transmits polarized light in a predetermined direction may also be used as the polarization adjustment unit 30.

[0063] As an example, consider a situation where image light L1 is irradiated from image irradiation unit 10 with polarized light in a predetermined direction. However, due to vehicle model or manufacturing errors, the tilt of windshield WS may not align with the polarization direction of image light L1. In this case, image light L1 reaching windshield WS contains both P-polarized and S-polarized components corresponding to the tilt direction. Consequently, a double virtual image is formed by the S-polarized light reflected by the surface of windshield WS and the P-polarized light reflected by polarized light reflecting unit 40, resulting in reduced visual recognition.

[0064] Therefore, by arranging the polarization direction of light transmitted by the polarizing plate serving as the polarization adjusting unit 30 to correspond to the inclination of the windshield WS, the S-polarized light component in the inclination direction of the windshield WS is cut. As a result, the image light L1 reaching the windshield WS becomes P-polarized light with respect to the inclination direction of the windshield WS, thereby suppressing the formation of double virtual images and improving visual recognition.

[0065] If the angular difference between the polarization direction of the polarizing plate and the image light L1 exceeds 30 degrees, the amount of image light L1 transmitted through the polarizing plate decreases, and the brightness of the virtual image decreases. Therefore, the angular difference between the polarization direction of the polarizing plate as the polarization adjustment unit 30 and the polarization direction of the image light L1 emitted by the image irradiation unit 10 is preferably within a range of 30 degrees.

[0066] 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 technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0067] This international application claims priority based on Japanese Patent Application No. 2023-018730, filed on February 9, 2023, the entire contents of which are incorporated herein by reference.

[0068] The above descriptions of the specific embodiments of the present invention are provided for the purpose of illustration. They are not exhaustive or intended to limit the present invention to the described embodiments. It is obvious to those skilled in the art that various modifications and variations can be made according to the above descriptions.

[0069] Description of Reference Numerals

[0070] 100, 110, 120... Image projection device

[0071] 10…Image irradiation unit

[0072] 20…Free-form surface mirror (projection optics)

[0073] 30…Polarization adjustment unit

[0074] 40…Polarized light reflecting portion

[0075] 50…half-wavelength plate

Claims

1. An image projection device for projecting an image onto a display unit for displaying a virtual image, characterized in that: The image projection device comprises: an image irradiation unit that irradiates image light; a projection optical unit configured to project the image light onto the display unit as the projection image; The image light emitted from the projection optical unit includes P-polarized light with respect to the display unit. The image projection device includes a polarization adjustment unit that adjusts the polarization direction of the image light.

2. The image projection device according to claim 1, wherein The polarization adjusting unit is a polarizing plate that transmits polarized light in a predetermined direction. The predetermined direction intersects with the polarization direction of the image light emitted from the projection optical section.

3. The image projection device according to claim 1, wherein The polarization adjusting section is a polarization compensation plate that changes the polarization direction according to an incident angle.

4. The image projection device according to claim 3, wherein: The polarization compensation plate is bent.

5. The image projection device according to claim 1, wherein The polarization adjustment unit is disposed between the projection optical unit and the display unit.

6. The image projection device according to any one of claims 1 to 5, characterized in that The polarization adjusting unit adjusts the polarization direction of at least a portion of the image light emitted from the projection optical unit within a range of 30 degrees.

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