Image projection unit and image projection device

Abstract

To provide an image projection unit and image projection device, which allow for enhancing light transmittance over an entire image even if a polarizing place is placed near an imager display unit.SOLUTION: The image projection unit (10) is provided, comprising an image display unit (12) for irradiating image light polarized in a first direction, a polarizing plate (20) located in a path of the image light and configured to transmit light polarized in the first direction and blocks light polarized in a second direction intersecting the first direction, and holders (11a, 11b, 11c) for bending and holding the polarizing plate (20).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image projection unit and 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 in order 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 the image projection devices disclosed in Patent Documents 1 and 2, an image projection unit emits light containing an image, which is reflected by a free-form mirror or the like, and 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 on the viewpoint. It has also been proposed to emit multiple beams of image light to form multiple virtual images at different distances from the windshield.

[0005] In such conventional image projection devices, when sunlight or other external light enters from outside, the external light is concentrated on the surface of the image display unit by the free-form surface mirror, which can cause the temperature of the image display unit to rise and deteriorate. Therefore, it has been proposed to place an external light filter on the path of the external light to cut out the ultraviolet and infrared light contained in the external light, thereby reducing the energy of the external light that reaches the image display unit and suppressing the temperature rise of the image display unit (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-119248 [Patent Document 2] Japanese Patent Application Publication No. 2019-119262 [Patent Document 3] Japanese Patent Publication No. 2023-055057 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional image projection devices, temperature rise in the image display unit can be suppressed by using an external light cut filter to cut out some wavelengths of external light, but visible light remains transmitted, limiting the extent to which temperature rise can be suppressed. The inventors of the present application therefore investigated using a polarizing plate as an external light cut filter, which transmits the light emitted from the image display unit and cuts light perpendicular to the polarization direction of the light. However, when a polarizing plate is placed near the image display unit, the divergence angle of the luminous flux of the irradiated light increases, and the transmittance varies depending on the angle of incidence of the light on the polarizing plate, making it difficult to maintain high transmittance of the irradiated light across the entire image.

[0008] Furthermore, although the image projection device is provided with a dust cover over the projection port of the irradiated light, there is also the problem that the external light reflected by the dust cover is reflected again by the windshield and reaches the viewpoint of the passenger.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide an image projection unit and an image projection device that can increase the light transmittance across the entire image area even when a polarizing plate is placed near the image display unit. [Means for solving the problem]

[0010] In order to solve the above problem, the image projection unit of the present invention is characterized by comprising an image display unit that irradiates image light polarized in a first direction, a polarizing plate that is arranged on the path of the image light and transmits polarized light in the first direction and blocks polarized light in a second direction that intersects with the first direction, and a holding unit that curves and holds the polarizing plate.

[0011] In the image projection unit of the present invention, the polarizing plate is curved and held by the holding section, so that the angle of incidence of the image light can be made close to a right angle throughout the entire surface of the polarizing plate, and even if the polarizing plate is placed near the image display section, it is possible to increase the light transmittance throughout the entire image.

[0012] In one aspect of the present invention, the display device further includes a housing that holds the image display unit, and the holding portion is provided on the housing and supports the polarizing plate at at least three points.

[0013] In one aspect of the present invention, the holding portion has a sliding portion arranged on both sides of the polarizing plate to slidably hold the polarizing plate, and an interference portion that interferes with and bends the polarizing plate inserted into the sliding portion.

[0014] In one aspect of the present invention, the polarizing plate includes a polarization surface through which the image light passes, a slide tab portion inserted into the slide portion, and a curved tab portion protruding from the polarization surface.

[0015] In addition, in order to solve the above problem, the image projection device of the present invention is characterized by comprising an image projection unit described in any one of the above, a primary mirror that reflects the image light irradiated from the image projection unit, a secondary mirror that reflects the image light reflected by the primary mirror, and a dustproof cover through which the image light reflected by the secondary mirror passes.

[0016] In one aspect of the present invention, the dust cover is disposed at an angle such that the rear side closer to the primary mirror is lower than the front side farther from the primary mirror.

[0017] In one aspect of the present invention, the dustproof cover has a larger inclination angle from the horizontal direction on the front side than on the rear side.

[0018] In one aspect of the present invention, the rear side of the dust cover is located below the primary mirror.

[0019] In one aspect of the present invention, the rear side of the dust cover is positioned lower than the front side by a distance in the range of 5 mm to 20 mm.

[0020] In one aspect of the present invention, the image light is intermediately imaged between the primary mirror and the secondary mirror. [Effects of the Invention]

[0021] The present invention can provide an image projection unit and an image projection device that can increase the light transmittance over the entire image area even when a polarizing plate is disposed near the image display section. [Brief explanation of the drawings]

[0022] [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] FIG. 1 is a schematic cross-sectional view illustrating an overview of an image projection device 100. [Figure 3]FIG. 2 is a schematic perspective view illustrating an overview of the image projection unit 10 with a polarizing plate 20 attached. [Figure 4] FIG. 2 is a schematic perspective view illustrating an overview of an image projection unit 10 in a state where a polarizing plate 20 is not attached. [Figure 5] 5A and 5B are schematic perspective views illustrating the structure and curvature of a polarizing plate 20, where FIG. 5A shows the polarizing plate in a flat, uncurved state, and FIG. 5B shows the polarizing plate in a curved state. [Figure 6] This is a process diagram showing the state before inserting the polarizing plate 20 into the holding portions 11a, 11b, and 11c, where Figure 6(a) is a side view, Figure 6(b) is a front view of the polarizing plate 20, and Figure 6(c) is a view from the sliding direction of the holding portions 11a and 11b. [Figure 7] This is a process diagram showing the state in the middle of inserting the polarizing plate 20 into the holding portions 11a, 11b, and 11c, where Figure 7(a) is a side view, Figure 7(b) is a front view of the polarizing plate 20, and Figure 7(c) is a view from the sliding direction of the holding portions 11a and 11b. [Figure 8] This is a process diagram showing the state in which a polarizing plate 20 is inserted into the holding portions 11a, 11b, and 11c, where Figure 8(a) is a side view, Figure 8(b) is a front view of the polarizing plate 20, and Figure 8(c) is a view from the sliding direction of the holding portions 11a and 11b. DETAILED DESCRIPTION OF THE INVENTION

[0023] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicated explanations will be omitted as appropriate. In the following description, an image projection unit 10 and an image projection device 100 according to the present invention will be described by way of example in which they are applied to a HUD mounted on a vehicle or the like.

[0024] 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 polarizing plate 20, a primary mirror 30, and a secondary mirror 40. As shown in FIG. 1, image light projected from the image projection device 100 is reflected by a windshield (display unit) WS and irradiated onto a driver's viewpoint E. The driver views a virtual image P formed on an extension of the optical path of the incident image light. The dashed lines in FIG. 1 schematically represent the luminous flux of the image light irradiated from the image projection device 100, the optical path of the image light reflected by the windshield WS and reaching the viewpoint E, and its extension. 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.

[0025] 1, each part is controlled by a control unit connected to the other parts so as to be able to communicate information with them. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for processing information, a memory device, a recording medium, an information communication device, etc. The control unit controls the operation of each part in accordance with a predetermined program, and sends information including an image (image information) to the image projection unit 10.

[0026] The image projection 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 projection unit 10 is not limited, and a conventionally known device such as a liquid crystal display device or an organic EL display device can be used. As an example, a device that irradiates light from a light emitting diode (LED) on the back side of a liquid crystal display device is used.

[0027] The polarizing plate 20 is an optical element having the optical property of transmitting polarized light in the transmission axis direction and reflecting or absorbing polarized light perpendicular to the transmission axis direction, and a known polarizing plate or polarizing film can be used. It is preferable that the transmittance of the transmission axis is uniform within the plane of the polarizing plate 20. Here, the transmission axis direction of the polarizing plate 20 corresponds to the first direction in the present invention, and the direction perpendicular to the transmission axis direction corresponds to the second direction in the present invention. It is also preferable that the transmission axis of the polarizing plate 20 is positioned so as to transmit P-polarized light with respect to the windshield WS.

[0028] The polarizing plate 20 is curved by holding portions 11a, 11b, and 11c as described below, and fixed to the image projection unit 10. Although the present embodiment shows an example in which the polarizing plate 20 is made of a single plate-like member, it may also have a structure in which a polarizing sheet is bonded to a light-transmitting substrate such as a resin. Furthermore, sheets that perform other optical functions may be bonded to the polarizing plate 20 to achieve multiple functions; one example is bonding an infrared light cut filter or an ultraviolet light cut filter. The polarizing plate 20 will be described in detail below.

[0029] The primary mirror 30 is an optical element that receives the image light emitted from the image projection unit 10 and reflects the image light toward the secondary mirror 40. In the example shown in FIG. 1, the primary mirror 30 is a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P. The secondary mirror 40 is an optical element that receives the image light reflected by the primary mirror 30 and reflects the image light toward the windshield WS. In the example shown in FIG. 1, the secondary mirror 40 is a free-form surface mirror with an optical design necessary for projecting the image light as a virtual image P. The tilt angle of the secondary mirror 40 with respect to the horizontal direction may be changeable, so that the projection direction of the image light can be changed and the projection position of the virtual image P can be moved up and down.

[0030] The reflective surfaces of primary mirror 30 and secondary mirror 40 are designed to expand the light diameter in the driver's line of sight in order to project the image light as a virtual image P through the windshield WS. Here, "expanding the light diameter in the line of sight" 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 primary mirror 30 and secondary mirror 40 has the function of projecting image light through the windshield WS, and corresponds to the projection mirror unit in this invention.

[0031] 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 the windshield WS, on the inside surface of the vehicle, reflects image light incident from the secondary mirror 40 toward the viewpoint and transmits light from outside the vehicle toward the viewpoint. While 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 secondary mirror 40 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.

[0032] The virtual image P is an image that appears as if it were formed in space when the image light reflected by the windshield WS reaches the viewpoint E (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 emitted from the image projection unit 10 as it travels toward the viewpoint after being reflected by the primary mirror 30, the secondary mirror 40, and the windshield WS. The display content of the image projected as the virtual image P may include auxiliary information related to driving such as a warning image or emergency information, a volume indicator, a driving direction guide, etc.

[0033] 2 is a schematic cross-sectional view illustrating an overview of the image projection device 100. As shown in FIG. 2, the image projection device 100 includes an image projection unit 10, a polarizing plate 20, a primary mirror 30, a secondary mirror 40, a housing part 50, and a dustproof cover 60.

[0034] The housing unit 50 is a housing that forms the outer shape of the image projection device 100 and houses the other components inside. An opening is provided at the top of the housing unit 50, and a dustproof cover 60 is provided over the opening to seal the interior. In FIG. 2, the cross-sectional shape of the housing unit 50 is shown as a box shape with a flat bottom and an inclined bottom, but the shape of the housing unit 50 is not limited. The material that forms the housing unit 50 is not limited, and a resin material or a metal material that blocks light can be used.

[0035] The dustproof cover 60 is made of a material that transmits image light and is a component disposed to cover the opening of the housing unit 50. Although not shown in FIG. 2, the dustproof cover 60 is fixed to the housing unit 50 in a structure that leaves no gap between them, preventing dust and dirt from entering the housing unit 50. There are no restrictions on the material that constitutes the dustproof cover 60, and known resin materials or glass that transmit image light can be used. Also, in FIG. 2, the rear and front ends of the dustproof cover 60 are indicated as a rear end 61 and a front end 62, respectively.

[0036] 2, dustproof cover 60 is disposed at an angle such that rear end 61 (rear side) closer to primary mirror 30 is lower than front end 62 (front side) farther from primary mirror 30. As a result, even if external light reaches dustproof cover 60 from windshield WS located above image projection device 100 and part of the external light is reflected by dustproof cover 60, the optical path of the reflected light can be made different from the optical path of the image light, preventing the reflected light from reaching viewpoint position E.

[0037] Although the height difference between the front end 62 and the rear end 61 of the dust cover 60 is not limited, it is preferable that the rear end 61 (rear side) be located lower than the front end 62 (front side) by a range of 5 mm to 20 mm. If the height difference is less than 5 mm, it is undesirable because some of the external light scattered and reflected by the dust cover 60 may reach the viewpoint E. Furthermore, if the rear end 61 (rear side) is located lower than the front end 62 (front side) by more than 20 mm, it is difficult to ensure an optical path for the image light within the housing unit 50, which is also undesirable.

[0038] 2, the dust cover 60 is curved downward in the left-right direction in the figure, with the angle of inclination from the horizontal being greater and steeper at the front end 62 (front side) than at the rear end 61 (rear side). Because the front end 62 of the dust cover 60 is closer to the windshield WS than the rear end 61, making the inclination steeper near the front end 62 can effectively prevent external light reflected at the front end 62 from reaching the viewpoint E.

[0039] As shown in FIG. 2, image light emitted from image projection unit 10 passes through polarizing plate 20 and is reflected by primary mirror 30, reducing its light diameter as it travels. The image light reflected by primary mirror 30 forms an intermediate image at intermediate imaging position F before reaching secondary mirror 40, with the components in the vertical direction (height direction) in the figure. Because the image light reflected by primary mirror 30 forms an image at intermediate imaging position F between primary mirror 30 and secondary mirror 40, the cross-sectional area through which the image light passes is minimized at intermediate imaging position F between primary mirror 30 and secondary mirror 40. The image light intermediately formed at intermediate imaging position F reaches secondary mirror 40 while its light diameter is expanded, and after being reflected by secondary mirror 40, passes through dustproof cover 60 and is irradiated to the outside of image projection device 100.

[0040] 2, the rear end 61 (rear side) of the dustproof cover 60 is positioned below the primary mirror 30. As described above, the image light forms an intermediate image at intermediate image position F between the primary mirror 30 and the secondary mirror 40, and therefore the cross-sectional area through which the image light passes is minimum near intermediate image position F. Therefore, even if the rear end 61 of the dustproof cover 60 is positioned below the primary mirror 30, the image light is not blocked by the dustproof cover 60 or the housing part 50, which improves design freedom and enables miniaturization.

[0041] FIG. 3 is a schematic perspective view illustrating an overview of the image projection unit 10 with the polarizing plate 20 attached. FIG. 4 is a schematic perspective view illustrating an overview of the image projection unit 10 without the polarizing plate 20 attached. As shown in FIGS. 3 and 4, the image projection unit 10 includes a unit housing 11, an image display unit 12, and holders 11a, 11b, and 11c. The polarizing plate 20 is curved by the holders 11a, 11b, and 11c and fixed at an angle relative to the unit housing 11. The image display unit 12 is disposed on top of the unit housing 11 and displays an image in a display area 12a, which is a portion of the display surface. The display area 12a is located between the holders 11a and 11b and below the polarizing plate 20 held by the holders 11a, 11b, and 11c.

[0042] The unit housing 11 constitutes the outer shape of the image projection unit 10, and is a member that holds the image display unit 12 and the polarizing plate 20 at the top, and corresponds to the housing in the present invention. The unit housing 11 also houses a light source unit, a primary lens, a secondary lens, etc., and irradiates the image display unit 12 with light emitted from the light source unit. A heat dissipation member that dissipates heat generated by light emission from the light source unit may be arranged on the back surface of the unit housing 11.

[0043] The holding portions 11a, 11b, and 11c are provided on the upper portion of the unit housing 11 and are portions that hold the polarizing plate 20 above the display area 12a in a curved state. The shapes and structures of the holding portions 11a, 11b, and 11c are not limited, but it is preferable that the holding portion 11c be disposed between the holding portions 11a and 11b. Fig. 2 shows an example in which the holding portions 11a and 11b support both sides of the polarizing plate 20 in the width direction, and the holding portion 11c causes the central position of the polarizing plate 20 to protrude from both sides and bend.

[0044] The holding portions 11a and 11b of this embodiment are arranged on both sides of the polarizing plate 20 to slidably hold the polarizing plate 20. The holding portion 11c of this embodiment interferes with and bends the polarizing plate 20 inserted between the holding portions 11a and 11b. The bending of the polarizing plate 20 by the holding portions 11a, 11b, and 11c will be described in detail below.

[0045] The image display unit 12 functions as a spatial light modulation unit that receives light emitted from a light source unit, modulates the light according to image information, and emits the modulated light from the display area 12a. The specific configuration of the image display unit 12 is not limited, but one example is a transmissive liquid crystal display device that transmits light incident from the back surface and emits it from the front surface. In a transmissive liquid crystal display device, only light polarized in a predetermined direction that is incident on the back surface is transmitted. When a transmissive liquid crystal display device is used as the image display unit 12, the transmission axis of the polarizer 20 is oriented in a direction that corresponds to the polarization direction of the image light emitted from the image display unit 12.

[0046] Display area 12a is an area within the display surface of image display unit 12 that displays an image to be projected as virtual image P. In the example shown in Fig. 3, display area 12a is a substantially rectangular area that is elongated in the width direction of image projection unit 10, but the shape is not limited thereto. There is no limitation on the method of using only a portion of the display surface of image display unit 12 as display area 12a, and an image may be displayed only in a portion, or a light-shielding plate having an opening formed therein that is positioned and shaped to correspond to display area 12a may be placed on the display surface of image display unit 12.

[0047] In the image projection unit 10 shown in FIGS. 3 and 4, light emitted from the light-emitting unit is refracted by the primary lens and secondary lens within the unit housing 11, and is then irradiated onto the image display unit 12 with a predetermined light distribution. The light irradiated onto the image display unit 12 is modulated by the image displayed in the display area 12a and is then irradiated onto the polarizing plate 20 as image light. At this time, if the image display unit 12 is a transmissive liquid crystal display device, the image light is polarized in a predetermined direction. The transmission axis of the polarizing plate 20 corresponds to the polarization direction of the image light, so the image light passes through the polarizing plate 20. The image light that has passed through the polarizing plate 20 is reflected by the primary mirror 30 and secondary mirror 40 as described above, and is then irradiated onto the windshield WS via the dustproof cover 60.

[0048] Furthermore, in the image projection device 100 of this embodiment, external light arriving from above the windshield WS enters the housing unit 50 via the dustproof cover 60. A portion of the external light is reflected by the secondary mirror 40 to reach the primary mirror 30, and is then reflected by the primary mirror 30 to reach the image display unit 12 via the polarizing plate 20. At this time, although the external light is unpolarized, the polarization direction that passes through the transmission axis of the polarizing plate 20 is limited, and the polarized component perpendicular to the transmission axis is cut. Therefore, the amount of external light that reaches the image display unit 12 is halved, and the temperature rise of the image display unit 12 can be suppressed.

[0049] The diameter of the light irradiated onto the image display unit 12 is enlarged by the secondary lens as it travels, and therefore the image light irradiated from the display region 12a onto the polarizing plate 20 also travels enlarged. In particular, in the width direction (longitudinal direction), as the distance from the center increases, the angle with respect to the vertical direction also increases, and the image light expands in a fan shape.

[0050] In the polarizing plate 20, the transmittance of polarized light in the transmission axis direction depends on the incident angle, and the transmittance tends to decrease when the incident angle is large (largely deviated from the perpendicular). However, in this embodiment, the polarizing plate 20 is curved along the longitudinal direction by the holding portions 11a, 11b, and 11c, and is disposed so that the concave shape faces the side on which the image light emitted from the image display unit 12 is incident. Furthermore, the transmission axis of the polarizing plate 20 is in the lateral direction, which is perpendicular to the longitudinal direction of the curve. Therefore, the incident angle of the image light that propagates while expanding on the polarizing plate 20 becomes smaller at each position, and it reaches the polarizing plate 20 at an angle close to perpendicular. Even if the image light reaches the polarizing plate 20 while expanding in a fan-like shape, the image light can be made to enter the polarizing plate 20 at an angle close to perpendicular at each position. This suppresses the difference in transmittance between the central region and the edge regions of the polarizing plate 20, thereby uniformly increasing the transmittance of the image light throughout the entire region.

[0051] 5A and 5B are schematic perspective views illustrating the structure and curvature of polarizing plate 20, with Fig. 5A showing the polarizing plate in a flat, uncurved state and Fig. 5B showing the polarizing plate in a curved state. As shown in Figs. 5A and 5B, polarizing plate 20 of this embodiment includes polarizing surface 21, curved tab portion 22, and slide tab portions 23a and 23b.

[0052] The polarization surface 21 is a portion that has optical properties of transmitting polarized light in the transmission axis direction when image light is incident thereon and reflecting or absorbing polarized light orthogonal to the transmission axis direction. In this embodiment, the polarization surface 21 is shaped like a rectangle, with the width direction of the image projection unit 10 being the longitudinal direction. The transmission axis of the polarization surface 21 is aligned with the short side direction and is curved along the longitudinal direction. Slide tab portions 23a, 23b are integrally formed on both ends of the polarization surface 21, and a curved tab portion 22 is integrally formed at approximately the center in the longitudinal direction. In the example shown in Figures 5(a) and (b), a notch is formed in part of the polarization surface 21, making it asymmetrical, but it may also be shaped symmetrically.

[0053] The curved tab portion 22 is a portion provided so as to protrude from approximately the center of one of the long sides of the polarization surface 21. In the examples shown in Figures 3 and 5, the curved tab portion 22 is shown as a triangle having two sides inclined at a certain angle with respect to the longitudinal direction of the polarization surface 21, but the shape and size are not limited thereto and it may be a semicircular or rectangular shape. Furthermore, in the example shown in Figures 5(a) and (b), the curved tab portion 22 is an extended surface having the same plane as the polarization surface 21, but the curved tab portion 22 may be formed by bending it at a predetermined angle with respect to the polarization surface 21.

[0054] The slide tab portions 23a and 23b are portions that protrude from the short sides at both ends in the width direction of the polarization plane 21. In the example shown in Fig. 5, the slide tab portions 23a and 23b are rectangular, but the shape and size are not limited thereto and they may be semicircular or triangular. In addition, in the example shown in Fig. 5(a) and (b), the slide tab portions 23a and 23b are provided asymmetrically, but they may be provided at symmetrical positions.

[0055] As shown in FIG. 5(b), when the polarizing plate 20 is held by the slide tab portions 23a and 23b on both sides, and a force is applied in a direction in which the curved tab portion 22 interferes with the holding portion 11c and is pushed out to one side, the central portion of the polarization plane 21 and the curved tab portion 22 are pushed out and curved. At this time, the curved shape of the polarizing plate 20 can be adjusted by the distance the curved tab portion 22 is pushed out. The curved shape of the polarizing plate 20 depends on the spread angle of the image light emitted from the display region 12a of the image display unit 12, and examples of the curved shape include an arc, an ellipse, a parabola, a hyperbola, and a free curve. The curvature may also vary partially depending on the spread angle of the image light.

[0056] FIG. 6 is a process diagram showing the state before the polarizing plate 20 is inserted into the holders 11a, 11b, and 11c, where FIG. 6(a) is a side view, FIG. 6(b) is a front view of the polarizing plate 20, and FIG. 6(c) is a view from the sliding direction of the holders 11a and 11b. Here, the left direction in FIG. 6(a) is the front, the right direction is the rear, and the up-down direction is the sliding direction. Also, the left-right direction in FIG. 6(b) is the width direction or longitudinal direction, and the up-down direction is the sliding direction. In FIG. 6(c), the left-right direction corresponds to the width direction or longitudinal direction, the up direction corresponds to the rear, and the down direction corresponds to the front.

[0057] As shown in FIG. 6(a), the holding portions 11a and 11b have plate-like portions facing each other, and a slit is formed between the plate-like portions. The extending direction of the slits of the holding portions 11a and 11b corresponds to the inclination angle of the polarizing plate 20 relative to the unit housing 11. The slits of the holding portions 11a and 11b are inclined at the same inclination angle relative to the unit housing 11, and both slits are located in the same plane. One surface of the holding portion 11c is a tapered surface that is inclined from the rear to the front of the slit. In addition, the other surface of the holding portion 11c is located at a position different from the plane formed by the slits on both sides, and is a protruding surface that protrudes further forward than the holding portions 11a and 11b.

[0058] 6(a) to 6(c), polarizing plate 20 is placed at positions where slide tab portions 23a and 23b correspond to holding portions 11a and 11b, respectively, and slide tab portions 23a and 23b are inserted along the slits. The slits of holding portions 11a and 11b are arranged on both sides of polarizing plate 20 and have the function of slidably holding polarizing plate 20, and correspond to the slide portions in the present invention.

[0059] 7A and 7B are process diagrams showing the state in the middle of inserting polarizing plate 20 into holding portions 11a, 11b, and 11c, where Fig. 7A is a side view, Fig. 7B is a front view of polarizing plate 20, and Fig. 7C is a view from the sliding direction of holding portions 11a and 11b. The front, rear, sliding direction, width direction or length direction, and sliding direction in the figures are the same as those in Fig. 6.

[0060] 7(a) to 7(c), when slide tab portions 23a and 23b are inserted by sliding along the slits of holding portions 11a and 11b, respectively, the tip of curved tab portion 22 abuts against the tapered surface of holding portion 11c. When polarizing plate 20 is inserted along the slits in this state, curved tab portion 22 interferes with the tapered surface of holding portion 11c, and a force is applied to curved tab portion 22 to push it forward. At this time, because curved tab portion 22 is formed integrally with polarizing surface 21, the force applied to curved tab portion 22 is also transmitted to the center of polarizing surface 21 in the width direction, and the centers of curved tab portion 22 and polarizing surface 21 are pushed forward and bent.

[0061] 8A and 8B are process diagrams showing the state in which polarizing plate 20 is inserted into holding portions 11a, 11b, and 11c, with Fig. 8A being a side view, Fig. 8B being a front view of polarizing plate 20, and Fig. 8C being a view from the sliding direction of holding portions 11a and 11b. The front, rear, sliding direction, width direction or length direction, and sliding direction in the figure are the same as those in Fig. 6.

[0062] 8(a) to 8(c), when polarizing plate 20 is inserted up to the end of the slits in holding portions 11a and 11b, the back side of curved tab portion 22 abuts against the protruding surface of holding portion 11c. In this state, slide tab portions 23a and 23b are held by holding portions 11a and 11b, respectively, on both sides of polarizing plate 20, and curved tab portion 22 interferes with the protruding surface of holding portion 11c, applying a force pushing curved tab portion 22 forward. As a result, curved tab portion 22 and the center of polarization surface 21 of polarizing plate 20 are pushed forward and curved, and polarizing plate 20 is held in a state inclined at a predetermined angle relative to unit housing 11.

[0063] 6 to 8, retaining portions 11a and 11b may be provided with locking pieces at the upper ends of the slits to restrict sliding in the opposite direction after slide tab portions 23a and 23b are inserted until they abut the end portions. As described above, the tapered surface and protruding surface of retaining portion 11c have the function of interfering with and curving polarizing plate 20 inserted into the slits of retaining portions 11a and 11b, and correspond to the interference portion in the present invention.

[0064] As described above, in the image projection unit 10 and image projection device 100 of this embodiment, the polarizing plate 20 is curved and held by the holding portions 11a, 11b, and 11c, so that the angle of incidence of the image light can be made close to a right angle throughout the entire surface of the polarizing plate 20, and even if the polarizing plate 20 is placed near the image display unit 12, it is possible to increase the light transmittance throughout the entire image.

[0065] Furthermore, the image projection unit 10 and the image projection device 100 of this embodiment have a unit housing 11 that holds the image display unit 12, and holding portions 11a, 11b, and 11c are provided on the unit housing 11, which support the polarizing plate 20 at at least three locations. This makes it easy to arrange the polarizing plate 20 in an appropriate curved shape at a predetermined position and angle relative to the unit housing 11.

[0066] Furthermore, holding portions 11a and 11b are arranged on both sides of polarizing plate 20 and have slits, and holding portion 11c has tapered surfaces and protruding surfaces that interfere with and bend polarizing plate 20 inserted into the slits. Polarizing plate 20 also has polarizing surface 21 through which image light passes, slide tab portions 23a and 23b that are inserted into the slits of holding portions 11a and 11b, and curved tab portion 22 that protrudes from polarizing surface 21. As a result, simply by inserting polarizing plate 20 into holding portions 11a and 11b, curved tab portion 22 and holding portion 11c interfere with each other to bend and hold polarizing plate 20, thereby simplifying the assembly process.

[0067] Furthermore, in image projection device 100 of this embodiment, dustproof cover 60 is disposed at an angle so that the rear side closer to primary mirror 30 is lower than the front side farther from primary mirror 30. This reduces the possibility that external light reflected by dustproof cover 60 will reach viewpoint position E.

[0068] 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]

[0069] 100...Image projection device 10...Image projection unit 20...Polarizing plate 30...Primary mirror 40...Secondary mirror 50...Housing section 60...Dustproof cover 11...Unit housing 11a, 11b, 11c...holding part 12...Image display section 12a...display area 21...polarization plane 22...Curved tab section 23a, 23b...Slide tab section 61...Rear end 62...Front end

Claims

1. an image display unit that irradiates image light polarized in a first direction; a polarizing plate disposed on a path of the image light, the polarizing plate transmitting light polarized in the first direction and blocking light polarized in a second direction intersecting the first direction; An image projection unit comprising: a holder that holds the polarizing plate in a curved state.

2. 2. The image projection unit according to claim 1, a housing for holding the image display unit; The image projection unit is characterized in that the holding portion is provided on the housing and supports the polarizing plate at at least three points.

3. 3. The image projection unit according to claim 2, The image projection unit is characterized in that the holding portion has a sliding portion arranged on both sides of the polarizing plate to slidably hold the polarizing plate, and an interference portion that interferes with and bends the polarizing plate inserted into the sliding portion.

4. 4. The image projection unit according to claim 3, The image projection unit is characterized in that the polarizing plate has a polarization surface through which the image light passes, a slide tab portion that is inserted into the slide portion, and a curved tab portion that protrudes from the polarization surface.

5. An image projection unit according to any one of claims 1 to 4; a primary mirror that reflects the image light emitted from the image projection unit; a secondary mirror that reflects the image light reflected by the primary mirror; an image projection device comprising: a dustproof cover through which the image light reflected by the secondary mirror passes;

6. 6. The image projection device according to claim 5, 10. An image projection device, wherein the dustproof cover is disposed at an angle such that a rear side closer to the primary mirror is lower than a front side farther from the primary mirror.

7. 7. The image projection device according to claim 6, The image projection device, wherein the dustproof cover has a larger inclination angle from the horizontal direction on the front side than on the rear side.

8. 7. The image projection device according to claim 6, The image projection device, wherein the rear side of the dustproof cover is located below the primary mirror.

9. 7. The image projection device according to claim 6, The dustproof cover is characterized in that the rear side is positioned lower than the front side by a range of 5 mm to 20 mm.

10. 7. The image projection device according to claim 6, 10. An image projection device, wherein the image light is intermediately imaged between the primary mirror and the secondary mirror.

Images