Image projection device

Abstract

Provided is an image projection device capable of saving space while increasing efficiency of utilization of irradiation light. An image projection device (10) comprises a light source unit (12) that emits unpolarized first irradiation light and second irradiation light, a first polarization conversion unit (15a) that converts the first irradiation light in a polarization direction along a first direction and emits the first irradiation light as first backlight light, a second polarization conversion unit (15b) that converts the second irradiation light in a polarization direction along the first direction and emits the second irradiation light as second backlight light, and an image display unit (110) on which the first backlight light and the second backlight light are incident from a back surface and which emits image light from a display surface, the irradiation direction of the first irradiation light and the second irradiation light from the light source unit (12) intersecting the emission direction of the first backlight light and the second backlight light.

Description

Image Projection Device

[0001] The present invention relates to an image projection device.

[0002] Conventionally, dashboards that illuminate icons have been used to display various types of information inside vehicles. As the amount of information to be displayed increases, it has been proposed to embed an image display device in the dashboard or to configure the entire dashboard with an image display device.

[0003] However, because the instrument panel is located below the vehicle's windshield, passengers such as the driver must undesirably move their eyes downward while driving to view the information displayed on the instrument panel. Therefore, image projection devices such as head-up displays (hereinafter referred to as HUDs) have been proposed that project images onto the windshield so that passengers can read information when they view the area ahead of the vehicle (see, for example, Patent Documents 1 and 2).

[0004] In the image projection devices disclosed in Patent Documents 1 and 2, an image projection unit emits light containing an image, and the light is reflected by a free-form mirror or the like, and the light reaches the viewpoint of the occupant so that the image is formed in space via a display unit such as a windshield. This allows the occupant to perceive the image as being displayed at the imaging position in the depth direction by the light incident on the viewpoint. It has also been proposed to project multiple beams of image light to form multiple virtual images at different distances from the windshield.

[0005] JP 2019-119248 A JP 2019-119262 A

[0006] In such conventional image projection devices, a projection image is displayed using an image display unit such as a liquid crystal display device, and the image light is projected by irradiating the image display unit with illumination light from the rear side. However, image display units such as liquid crystal display devices transmit only light polarized in a specific direction. Therefore, when unpolarized illumination light is incident, light polarized in directions other than the specific direction is not used to project the image, resulting in reduced light utilization efficiency. Optical components that convert the polarization of illumination light into a specific direction have been proposed, but these devices tend to be large in size in order to illuminate a large area.

[0007] SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and has as its object to provide an image projection device that can improve the utilization efficiency of irradiated light while saving space.

[0008] In order to solve the above problem, the image projection device of the present invention includes a light source unit that emits unpolarized first irradiation light and second irradiation light, a first polarization conversion unit that converts the first irradiation light into a polarization direction along a first direction and emits it as first backlight light, a second polarization conversion unit that converts the second irradiation light into a polarization direction along the first direction and emits it as second backlight light, and an image display unit into which the first backlight light and the second backlight light are incident from the back surface and which emits image light from a display surface, and is characterized in that the irradiation direction of the first irradiation light and the second irradiation light from the light source unit intersects with the emission direction of the first backlight light and the second backlight light.

[0009] In the image projection device of the present invention, the unpolarized first and second illumination lights are converted into polarization directions along the first direction by the first polarization conversion unit and the second polarization conversion unit, and the illumination directions of the first and second illumination lights intersect with the emission directions of the first and second backlight lights, making it possible to improve the utilization efficiency of the illumination light while saving space.

[0010] In one aspect of the present invention, the light source unit includes a first lens through which the first irradiation light passes and a second lens through which the second irradiation light passes, and the first lens and the second lens are integrally formed.

[0011] In one aspect of the present invention, the first polarization conversion unit and the second polarization conversion unit have different distances to the display surface, a light-blocking member that blocks light is arranged between the first polarization conversion unit and the second polarization conversion unit, and an opening is partially provided in the light-blocking member, so that the first irradiation light passes through the opening and enters the first polarization conversion unit.

[0012] In one aspect of the present invention, the first polarization conversion unit is closer to the display surface than the second polarization conversion unit and has an intersection region where the first irradiation light and the second backlight light intersect.

[0013] In one aspect of the present invention, the image display unit has a first region into which the first backlight light is incident and a second region into which the second backlight light is incident, and the first region and the second region are separated.

[0014] In one aspect of the present invention, the first area is larger than the second area, and the first image displayed in the first area is imaged at a position farther from the viewpoint than the second image displayed in the second area.

[0015] In one aspect of the present invention, the first polarization conversion unit and the second polarization conversion unit include a reflective polarization unit that reflects polarized light in the first direction and transmits polarized light in a second direction perpendicular to the first direction, a reflecting mirror that reflects light that has passed through the reflective polarization unit, and a half-wave plate arranged on the optical path of polarized light in the second direction.

[0016] The present invention can provide an image projection device that can improve the utilization efficiency of irradiated light while saving space.

[0017] FIG. 1 is a schematic diagram illustrating projection of a virtual image using the image projection device 100 according to the first embodiment. FIG. 2 is a schematic cross-sectional view illustrating an overview of the image projection device 100 according to the first embodiment. FIG. 3 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to the first embodiment. FIG. 4 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to the second embodiment. FIG. 5 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to the third embodiment. FIG. 6 is a schematic diagram illustrating modified examples of polarization conversion units 15a and 15b.

[0018] 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 will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In the following description, an image projection device 100 according to the present invention will be described by way of example in which it is applied to a HUD mounted on a vehicle or the like.

[0019] FIG. 1 is a schematic diagram illustrating the projection of virtual images P1 and P2 using an image projection device 100 according to this embodiment. The dashed line in FIG. 1 indicates the optical path of a first image light L1 (described later), and the dashed-dotted line indicates the optical path of a second image light L2. As shown in FIG. 1, the first image light L1 and the second image light L2 projected from the image projection device 100 are reflected by a windshield (display unit) WS and irradiated onto the driver's viewpoint. The driver visually recognizes virtual images P1 and P2 formed on an extension of the optical path along which the first image light L1 and the second image light L2 are incident. While this embodiment illustrates an example in which the image projection device 100 projects the first image light L1 and the second image light L2 to form two images P1 and P2, the number of virtual images is not limited.

[0020] The windshield WS is a portion of the vehicle that is provided in front of the driver's seat and transmits visible light. The windshield WS, on the interior surface of the vehicle, reflects the first image light L1 and the second image light L2 incident from the image projection device 100 toward the viewpoint and transmits light from outside the vehicle toward the viewpoint, and therefore corresponds to the display unit of the present invention. 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 image projection device 100 toward the viewpoint. Furthermore, the display unit is not limited to being located at the front of the vehicle, and may be located to the side or rear of the vehicle as long as it projects an image toward the viewpoint of the passenger.

[0021] The virtual images P1 and P2 are images that are displayed as if they were formed in space when the first image light L1 and the second image light L2 reflected by the windshield WS reach the viewpoint (eyebox) of the occupant. The positions at which the virtual images P1 and P2 are formed are determined by the combined focal length of the projection optical unit included in the image projection device 100 and the windshield WS.

[0022] In the image projection device 100 of this embodiment, a far image displayed in the far display area of ​​the image projection unit 10 is irradiated as a first image light L1, and a near image displayed in the near display area is irradiated as a second image light L2. Examples of far images displayed in the far display area include images calling attention to driving, emergency information, and other auxiliary information related to driving. Examples of near images displayed in the near display area include a speed and volume indicator, a driving direction guide, and the like.

[0023] FIG. 2 is a schematic cross-sectional view illustrating an overview of an image projection device 100 according to this embodiment. As shown in FIG. 2, the image projection device 100 includes an image projection unit 10, a first mirror 20, a second mirror 30, and a housing 40. In the image projection device 100, each unit is controlled using a control unit (not shown) connected to each unit so as to be able to communicate information with the unit. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for information processing, a memory device, a recording medium, an information communication device, and the like. The control unit controls the operation of each unit according to a predetermined program and sends information including an image (image information) to the image projection unit 10.

[0024] The image projection unit 10 is a part that, based on image information from the control unit, projects light containing an image onto the first mirror 20 as image light. In this embodiment, an example is shown in which two image lights displayed in two image display areas are projected onto the first mirror 20 as first image light L1 and second image light L2.

[0025] The first mirror 20 is an optical member that reflects the first image light L1 and the second image light L2 arriving from the image irradiation unit 10 toward the second mirror 30. In the example shown in Fig. 2, the first mirror 20 is a flat reflecting mirror, but a concave or convex reflecting mirror may also be used. Furthermore, when the first mirror 20 is configured with a curved surface, it is not limited to one with a constant curvature, and a paraboloid of revolution, an ellipsoid, a free-form surface mirror, or the like may be used.

[0026] The second mirror 30 is an optical member that reflects the first image light L1 and the second image light L2 that have arrived from the first mirror 20 toward the windshield WS. In the example shown in Fig. 1, the second mirror 30 is a free-form mirror with an optically designed concave shape necessary for projecting the first image light L1 and the second image light L2 as virtual images P1 and P2.

[0027] The reflective surfaces of the first mirror 20 and the second mirror 30 are designed to expand the light diameter in the driver's viewing direction in order to project the first image light L1 and the second image light L2 as virtual images P1 and P2 through the windshield WS. Here, "expanding the light diameter in the viewing 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 first image light L1 and the second image light L2 through the windshield WS and corresponds to the irradiation optical unit in the present invention.

[0028] The housing 40 constitutes the outer shape of the image projection device 100 and is a container that houses each component. The housing 40 is provided with a light exit port for emitting the first image light L1 and the second image light L2. An angle adjustment unit for adjusting the angle of the second mirror 30 may be provided within the housing 40 to adjust the irradiation angle of the first image light L1 and the second image light L2 projected onto the windshield WS and change the imaging height of the virtual images P1 and P2. The housing 40 may also be provided with an optical filter that cuts out ultraviolet light and infrared light contained in light (external light) arriving from outside.

[0029] 2, the optical paths of the first image light L1 and the second image light L2 are depicted as a single straight arrow. However, the actual first image light L1 and the second image light L2 are displayed as a predetermined area in the image projection unit 10, and have a predetermined area in a direction perpendicular to the traveling direction, as indicated by the range indicated by the dashed line in the figure. Furthermore, the first image light L1 and the second image light L2 may be reflected by the first mirror 20, and their light diameters may be reduced as they travel, and they may be intermediately imaged at an intermediate image position F (not shown) between the first mirror 20 and the second mirror 30.

[0030] 3 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to this embodiment. As shown in FIG. 3, the image projection unit 10 according to this embodiment includes a substrate 11, a light source unit 12, a heat sink 13, a primary lens 14, polarization conversion units 15a and 15b, a light blocking member 16, meniscus lenses 17a and 17b, orientation lenses 18a and 18b, and an image display unit 110. The polarization conversion units 15a and 15b include reflective polarizers 151a and 151b, reflectors 152a and 152b, and half-wave plates 153a and 153b, respectively.

[0031] The substrate 11 is a member on one surface of which a wiring pattern is formed and on which the light source unit 12 is mounted. The substrate 11 may be mounted with electronic components for driving the light source unit 12 to form a drive circuit. The substrate 11 may also be provided with a terminal unit (not shown), and power and control signals may be supplied from a cable or the like connected to the terminal unit.

[0032] The light source unit 12 is mounted on the substrate 11 and emits light onto the image display unit 110 via the primary lens 14, polarization conversion units 15a and 15b, meniscus lenses 17a and 17b, and orientation lenses 18a and 18b. The light source unit 12 is, for example, a semiconductor light-emitting element such as an LED (light-emitting diode), and is arranged in a predetermined direction (the depth direction of the paper in FIG. 3 ). The light emitted by the light source unit 12 is not particularly limited, but in this embodiment, white light is used as an example. In the example shown in FIG. 3 , the light source unit 12 is composed of LEDs 12a and 12b. Here, the LEDs 12a and 12b emit the first and second irradiation lights, respectively, according to the present invention. While the LEDs 12a and 12b are arranged in one row in this embodiment, two or more rows may be used. The irradiation light emitted from the light source unit 12 is unpolarized.

[0033] The heat sink 13 is a member for dissipating heat generated in the light source unit 12 as a result of irradiation with irradiated light via the substrate 11, and is disposed in contact with the rear surface of the substrate 11. There are no limitations on the material that constitutes the heat sink 13, but metal materials such as aluminum, resins mixed with fillers with high thermal conductivity, etc. can be used. There are no limitations on the shape of the heat sink 13, but it is preferable that it be provided with multiple heat dissipation fins to improve heat dissipation.

[0034] The primary lens 14 is an optical element disposed in the light emission direction of the light source unit 12, and has the function of concentrating the light emitted from the light source unit 12 and emitting it as, for example, parallel light or light close to parallel light (hereinafter, both of these will be collectively referred to as "substantially parallel light"). Fig. 3 shows an example of the primary lens 14 in which a first lens 14a, a second lens 14b, and a plate-like portion 14c are integrally molded. The first lens 14a and the second lens 14b are integrally molded via the plate-like portion 14c, which makes it possible to easily align the LEDs 12a and 12b and adjust the optical axes of the first and second irradiation lights.

[0035] The first lens 14a and the second lens 14b extend along the arrangement direction of the LEDs 12a and 12b, respectively. In this embodiment, as an example of the first lens 14a and the second lens 14b, a TIR (Total Internal Reflection) lens is used, which has a refractive portion in the center that refracts light and reflective portions on both sides of the refractive portion that reflect light. The primary lens 14 may be provided with multiple collimating lenses, one for each of the LEDs 12a and 12b. Furthermore, as long as the light from the LEDs 12a and 12b can be made into approximately parallel light, the primary lens 14 is not limited to a lens; a combination of a reflector and a lens, or a configuration in which a reflector alone can be used to make the light into approximately parallel light, may also be used.

[0036] 3, the LEDs 12a and 12b that constitute the light source unit 12 are mounted on a common substrate 11, so the first lens 14a and the second lens 14b of the primary lens 14 can be integrally molded and disposed on one side of the image display unit 110. This allows the image projection unit 10 to be made smaller.

[0037] The polarization conversion units 15a and 15b are optical components disposed on the light exit side of the primary lens 14, converting unpolarized illumination light into a polarization direction along a specific direction (first direction) and emitting the light as first backlight light and second backlight light, respectively. The polarization conversion units 15a and 15b correspond to the first polarization conversion unit and the second polarization conversion unit of the present invention, respectively. The specific configuration of the polarization conversion units 15a and 15b is not limited, and although FIG. 3 shows a combination of reflective polarizers 151a and 151b, reflectors 152a and 152b, and half-wave plates 153a and 153b as the polarization conversion units 15a and 15b, prisms may be used instead of the reflectors 152a and 152b.

[0038] The reflective polarizers 151a and 151b are optical components that reflect light polarized in a first direction and transmit light polarized in a second direction orthogonal to the first direction. The polarization direction of light transmitted by the reflective polarizers 151a and 151b is not limited, and must match the polarization direction required for the backlight ultimately irradiated onto the image display unit 110. As an example, the reflective polarizers 151a and 151b may transmit light polarized in the horizontal direction in FIG. 3 (e.g., p-polarized light) and reflect light polarized in a direction perpendicular to the paper surface (e.g., s-polarized light). The reflective polarizers 151a and 151b are arranged at a predetermined angle with respect to the traveling direction of light emitted from the LEDs 12a and 12b.

[0039] The reflecting mirrors 152a and 152b are optical members that reflect incident light. In the example shown in Fig. 3, the reflecting mirrors 152a and 152b are arranged so as to be inclined at a predetermined angle with respect to the traveling direction of light that has passed through the reflective polarizing units 151a and 151b. Fig. 3 shows an example in which the reflective polarizing units 151a and 151b and the reflecting mirrors 152a and 152b are arranged substantially parallel to the traveling direction of light emitted from the LEDs 12a and 12b with the same inclination angle, but the inclination angles may be different.

[0040] The half-wave plates 153a and 153b are optical elements arranged on the path of the second-direction polarized light that has passed through the reflective polarizing units 151a and 151b, and are made of a birefringent material with different refractive indices in the slow axis and the fast axis. The half-wave plates 153a and 153b are designed so that a phase difference of half the wavelength of the incident light occurs between the slow axis and the fast axis before the incident light exits. The slow axis and the fast axis of the half-wave plates 153a and 153b are arranged in directions that differ by 45 degrees from the polarization direction of the first irradiation light and the second irradiation light that have passed through the reflective polarizing units 151a and 151b.

[0041] Here, the combination of the light reflected by the reflective polarizing units 151a and 151b and the light whose polarization direction has been converted by the half-wave plates 153a and 153b of the first and second irradiation lights corresponds to the first backlight light and the second backlight light, respectively. While Fig. 3 shows an example in which the half-wave plates 153a and 153b are disposed between the reflecting mirrors 152a and 152b and the meniscus lenses 17a and 17b, the positions of the half-wave plates 153a and 153b are not limited as long as they are located on the path of the second-direction polarized light that has passed through the reflective polarizing units 151a and 151b. As an example, the half-wave plates 153a and 153b may be disposed between the reflective polarizing units 151a and 151b and the reflecting mirrors 152a and 152b.

[0042] The light-blocking member 16 is disposed between the polarization conversion units 15a and 15b and is made of a light-blocking material. The light-blocking member 16 has a partial opening 16a, through which the first irradiation light emitted from the LED 12a passes and enters the polarization conversion unit 15a. By disposing the light-blocking member 16 between the polarization conversion units 15a and 15b, stray light between the polarization conversion units 15a and 15b is prevented, and the first backlight and the second backlight can be appropriately irradiated onto the far display region 110a and the near display region 110b of the image display unit 110, respectively. While FIG. 3 shows the light-blocking member 16 having a substantially plate-like shape, the shape and material are not limited thereto.

[0043] The meniscus lenses 17a and 17b are optical components that adjust the light distribution of the first backlight light and the second backlight light emitted from the polarization conversion units 15a and 15b. The meniscus lenses 17a and 17b are formed to extend in a direction perpendicular to the plane of the paper in FIG. 3 . In the example shown in FIG. 3 , the meniscus lenses 17a and 17b include a first lens region and a second lens region. Light reflected by the polarization conversion units 15a and 15b enters the first lens region, and light reflected by the reflecting mirrors 152a and 152b enters the second lens region. While the optical characteristics of the first and second lens regions are not limited, it is preferable that the optical characteristics be such that the light reflected by the polarization conversion units 15a and 15b and the reflecting mirrors 152a and 152b travels in a direction such that the display region of the image display unit 110 is uniformly illuminated. Although FIG. 3 shows an example in which the meniscus lenses 17a and 17b are used, the meniscus lenses 17a and 17b may be omitted if the light distribution of the first backlight and the second backlight is appropriate.

[0044] The orientation lenses 18a and 18b are optical members disposed between the meniscus lenses 17a and 17b and the image display unit 110, and adjust the light distribution of the first backlight light and the second backlight light. Although an example using the orientation lenses 18a and 18b is shown in Fig. 3, the orientation lenses 18a and 18b may be omitted if the light distribution of the first backlight light and the second backlight light is appropriate.

[0045] The image display unit 110 functions as a spatial light modulation unit that receives first and second backlights emitted from the polarization conversion units 15a and 15b from the rear surface and emits light modulated by image information from the display surface. The image display unit 110 also has a far display area 110a onto which the first backlight is incident and a near display area 110b onto which the second backlight is incident. The far display area 110a and the near display area 110b are separately provided. Here, the far display area 110a and the near display area 110b correspond to the first and second areas, respectively, in the present invention. The specific configuration of the image display unit 110 is not limited, but an example would be a transmissive liquid crystal display device that transmits light incident from the rear surface and emits it from the front surface. In a transmissive liquid crystal display device, only light polarized in a specific direction incident on the rear surface is transmitted, so the polarization direction of the polarization conversion units 15a and 15b is aligned with the specific direction.

[0046] A diffusion plate (not shown) that diffuses and transmits backlight may be disposed on the side (rear side) of the image display unit 110 onto which backlight is incident. The diffusion plate diffuses the highly directional light polarized by the first lens 14 a, the second lens 14 b and the meniscus lenses 17 a, 17 b and outputs the light to the image display unit 110, thereby enabling the image display unit 110 to be more uniformly illuminated. As the diffusion plate, it is preferable to use an optical member that diffuses and transmits the first backlight and second backlight converted by the polarization conversion units 15 a, 15 b while maintaining the polarization direction of the light.

[0047] In the image projection device 100 described above, the first and second irradiation lights emitted from the LEDs 12a and 12b are unpolarized lights with no particular polarization direction. The first and second irradiation lights are collimated by the first lens 14a and the second lens 14b, respectively, and then enter the polarization conversion units 15a and 15b. The first and second irradiation lights incident on the polarization conversion units 15a and 15b are polarized in a first direction by the reflective polarization units 151a and 151b toward the meniscus lenses 17a and 17b, and the second polarized lights are transmitted through the reflective polarization units 151a and 151b. The polarization of the irradiation light (first light) reflected by the reflective polarization units 151a and 151b is polarized in the first direction, which is the direction of transmission through the image display unit 110. Moreover, the polarization of the illumination light (second light) transmitted through the reflective polarizing units 151a and 151b is polarized in a second direction that is substantially perpendicular to the first direction.

[0048] The first and second irradiation lights are polarized in the second direction and pass through the reflective polarizers 151a and 151b as second light, reflected by the reflectors 152a and 152b, and irradiated toward the image display unit 110. The second light is then transmitted through the half-wave plates 153a and 153b, where its polarization is rotated 90 degrees in-plane and converted into polarization in the first direction. As a result, the first light reflected by the reflective polarizers 151a and 151b and the second light transmitted through the half-wave plates 153a and 153b are irradiated as first backlight light and second backlight light, each polarized in the same first direction. The half-wave plates 153a and 153b do not need to have a phase difference of exactly 50% relative to the wavelength of the light; as long as they produce a phase difference close to 50%, they can function to rotate the polarization direction in-plane.

[0049] The first backlight and second backlight polarized in the first direction pass through meniscus lenses 17a, 17b and orientation lenses 18a, 18b, and their light distributions are adjusted before reaching the diffusers. The diffusers diffuse and transmit the first backlight and second backlight polarized in the first direction. This allows the backlight polarized in the first direction to be uniformly irradiated onto the rear surface of image display unit 110. This reduces the polarized component in the second direction that is absorbed by image display unit 110, thereby improving light utilization efficiency.

[0050] 3 , the first backlight light and the second backlight light emitted from the polarization conversion units 15 a and 15 b are irradiated onto the far display area 110 a and the near display area 110 b, which are different areas of the image display unit 110. Therefore, the first image light L1 and the second image light L2 transmitted through the far display area 110 a and the near display area 110 b can be separated. This eliminates the need for additional optical components for separating the first image light L1 and the second image light L2, thereby enabling the image projection device 100 to be made smaller.

[0051] In the image projection device 100 of this embodiment, the irradiation direction of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 intersects with the emission direction of the first backlight light and the second backlight light toward the image display unit 110. This allows the light source unit 12 to be disposed to the side of the image display unit 110, making it possible to reduce the thickness of the image irradiation unit 10 and improve the utilization efficiency of the irradiation light while also saving space.

[0052] In the example shown in FIG. 3 , the polarization conversion unit 15a is positioned closer to the display surface of the image display unit 110 than the polarization conversion unit 15b. A space (intersection region) is provided between the meniscus lens 17b and the polarization conversion unit 15b, where the first irradiation light incident on the polarization conversion unit 15a and the second backlight light emitted from the polarization conversion unit 15b intersect at the intersection region. By providing the intersection region to allow the first irradiation light and the second backlight light to intersect, the space within the image projection unit 10 can be effectively utilized. Specifically, in FIG. 3 , surplus regions where no components are placed are created below the polarization conversion unit 15a and to the right of the polarization conversion unit 15b. This allows for the miniaturization of a housing (not shown) when the entire image projection unit 10 is housed in the housing.

[0053] As described above, in the image projection device 100 of this embodiment, the unpolarized first and second irradiation lights are converted into polarization directions along the first direction by the polarization conversion units 15a and 15b, and the irradiation directions of the first and second irradiation lights intersect with the emission directions of the first and second backlight lights, making it possible to improve the utilization efficiency of the irradiation light while saving space.

[0054] Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. 4. Description of content that overlaps with the first embodiment will be omitted. FIG. 4 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to this embodiment. This embodiment differs from the first embodiment in that the polarization conversion unit 15b is disposed closer to the display surface of the image display unit 110 than the polarization conversion unit 15a.

[0055] 4, the LED 12b of the light source unit 12 is disposed closer to the display surface of the image display unit 110 than the LED 12a. The opening 16a provided in the light blocking member 16 is provided between the LED 12a and the polarization conversion unit 15a. In this embodiment, no space (intersection area) is provided between the meniscus lenses 17a, 17b and the polarization conversion units 15a, 15b, and the first irradiation light and the second backlight light, or the second irradiation light and the first backlight light, do not intersect.

[0056] However, even in the image projection device 100 of this embodiment, the irradiation direction of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 intersects with the emission direction of the first backlight light and the second backlight light toward the image display unit 110. This allows the light source unit 12 to be disposed to the side of the image display unit 110, making it possible to reduce the thickness of the image irradiation unit 10 and improve the utilization efficiency of the irradiation light while also saving space.

[0057] Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. 5. Description of content that overlaps with the first embodiment will be omitted. FIG. 5 is a schematic cross-sectional view illustrating an overview of the image projection unit 10 according to this embodiment. This embodiment differs from the first embodiment in that the area of ​​the far display region 110a of the image display unit 110 is larger than the near display region 110b.

[0058] As shown in FIG. 4 , because the area of ​​the far display region 110a is larger than the near display region 110b, the distance between the reflective polarizer 151a and the reflector 152a in the polarization converter 15a is increased to increase the area illuminated by the first backlight. At this time, the areas of the reflective polarizer 151a, the reflector 152a, the half-wave plate 153a, the meniscus lens 17a, and the orientation lens 18a are also increased as necessary. Furthermore, because the increased illumination area of ​​the first backlight emitted from the polarization converter 15a reduces brightness, the amount of light illuminated by the LEDs 12a may be increased to compensate for the reduced brightness. Specifically, the number of LEDs 12a may be increased to increase the mounting density on the substrate 11 relative to the number of LEDs 12a.

[0059] 1, the virtual image P1 of the far image (first image) displayed in the far display area 110a (first area) is formed at a position farther from the viewpoint than the virtual image P2 of the near image (second image) displayed in the near display area 110b (second area). Therefore, by making the far display area 110a larger than the near display area 110b, the visibility of the virtual image P1 of the far image can be improved.

[0060] In the image projection device 100 of this embodiment, the irradiation direction of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 also intersects with the emission direction of the first backlight light and the second backlight light toward the image display unit 110. This allows the light source unit 12 to be disposed to the side of the image display unit 110, making it possible to reduce the thickness of the image irradiation unit 10 and improve the utilization efficiency of the irradiation light while also saving space.

[0061] (Modifications of Polarization Converters 15a and 15b) Next, modifications of the polarization converters 15a and 15b will be described with reference to FIG. 6. Descriptions of content that overlaps with the first embodiment will be omitted. FIG. 6 is a schematic diagram illustrating modifications of the polarization converters 15a and 15b shown in the first to third embodiments. As shown in FIG. 6, the polarization converters 15a and 15b have half-wave plates 153a and 153b disposed on the back side of the reflective polarizers 151a and 151b between the reflective polarizers 151a and 151b and the reflectors 152a and 152b.

[0062] 6, the first and second irradiation lights incident on the reflective polarizers 151a and 151b are polarized in a first direction and reflected by the reflective polarizers 151a and 151b toward the meniscus lenses 17a and 17b, respectively, and the second irradiation lights polarized in a second direction are transmitted through the reflective polarizers 151a and 151b. The irradiation lights (first light) reflected by the reflective polarizers 151a and 151b are polarized in a first direction, which is the direction of transmission through the image display unit 110. The irradiation lights (second light) transmitted through the reflective polarizers 151a and 151b are polarized in a second direction that is substantially perpendicular to the first direction.

[0063] Furthermore, the first irradiation light and the second irradiation light are polarized in the second direction and transmitted through the reflective polarizing units 151 a and 151 b, and the second light is further polarized through the half-wave plates 153 a and 153 b, where the polarization is rotated 90 degrees in-plane and converted to polarization in the first direction. Furthermore, the second light that has transmitted through the half-wave plates 153 a and 153 b is reflected by the reflecting mirrors 152 a and 152 b and is irradiated toward the image display unit 110. As a result, the first light reflected by the reflective polarizing units 151 a and 151 b and the second light that has transmitted through the half-wave plates 153 a and 153 b are irradiated as first backlight light and second backlight light having the same polarization direction, that is, the first direction.

[0064] Even when the polarization conversion units 15a and 15b of this modified example are used, the first backlight and second backlight polarized in the first direction are transmitted through the meniscus lenses 17a and 17b and the orientation lenses 18a and 18b, and their light distributions are adjusted before reaching the diffusers. The diffusers diffuse and transmit the first backlight and second backlight polarized in the first direction. This allows the backlight polarized in the first direction to be uniformly irradiated onto the back surface of the image display unit 110. This reduces the polarized component in the second direction that is absorbed by the image display unit 110, thereby improving light utilization efficiency.

[0065] 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.

[0066] This international application claims priority based on Japanese Patent Application No. 2024-006443, filed on January 18, 2024, the entire contents of which are incorporated herein by reference.

[0067] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0068] DESCRIPTION OF SYMBOLS 100...Image projection device 10...Image irradiation unit 20...First mirror 30...Second mirror 40...Housing 11...Substrate 12...Light source unit 12a, 12b...LED 13...Heat sink 14...Primary lens 14a...First lens 14b...Second lens 14c...Plate-shaped unit 151a, 151b...Reflective polarization unit 152a, 152b...Reflector 153a, 153b...Half-wave plate 15a, 15b...Polarization conversion unit 16...Light-shielding member 16a...Opening 17a, 17b...Meniscus lens 18a, 18b...Orientation lens 110...Image display unit 110a...Far display area 110b...Near display area

Claims

1. An image projection apparatus, comprising: a light source unit that irradiates non-polarized first irradiation light and second irradiation light; a first polarization conversion unit that converts the first irradiation light into polarized light in a first direction and emits it as first backlight light; a second polarization conversion unit that converts the second irradiation light into polarized light in the first direction and emits it as second backlight light; and an image display unit that receives the first backlight light and the second backlight light from the back and emits image light from a display surface, wherein the irradiation directions of the first irradiation light and the second irradiation light from the light source unit intersect the emission directions of the first backlight light and the second backlight light.

2. The image projection apparatus according to claim 1, wherein the light source unit includes a first lens through which the first irradiation light passes and a second lens through which the second irradiation light passes, and the first lens and the second lens are integrally formed.

3. The image projection apparatus according to claim 1, wherein the distances from the first polarization conversion unit and the second polarization conversion unit to the display surface are different, a light shielding member that blocks light is disposed between the first polarization conversion unit and the second polarization conversion unit, and the light shielding member is partially provided with an opening, and the first irradiation light enters the first polarization conversion unit through the opening.

4. The image projection apparatus according to claim 3, wherein the distance from the first polarization conversion unit to the display surface is closer than that of the second polarization conversion unit, and the image projection apparatus includes an intersection region where the first irradiation light and the second backlight light intersect.

5. The image projection apparatus according to claim 1, wherein the image display unit has a first region where the first backlight light enters and a second region where the second backlight light enters, and the first region and the second region are separated.

6. The image projection apparatus according to claim 5, wherein the area of the first region is larger than that of the second region, and a first image displayed in the first region is imaged at a position farther from the viewpoint than a second image displayed in the second region.

7. The image projection apparatus according to any one of claims 1 to 6, wherein the first polarization conversion unit and the second polarization conversion unit include a reflective polarizing unit that reflects polarized light in the first direction and transmits polarized light in a second direction orthogonal to the first direction, a reflecting mirror that reflects light transmitted through the reflective polarizing unit, and a half-wave plate disposed on the optical path of the polarized light in the second direction.

Images