Image projection device

Abstract

To provide an image projection device capable of achieving a space saving while enhancing utilization efficiency of irradiation light.SOLUTION: An image projection device (10) includes: a light source part (12) configured to emit non-polarized first irradiation light and second irradiation light; a first polarization conversion part (15a) configured to convert the first irradiation light into a polarization direction aligned with a first direction and emit as first backlight light; a second polarization conversion part (15b) configured to convert the second irradiation light into a polarization direction aligned with the first direction and emit as second backlight light; and an image display part (110) configured to receive the first backlight light and the second backlight light incident from a back side and emit image light from a display surface. An irradiation direction of the first irradiation light and the second irradiation light from the light source part (12) intersects an emission direction of the first backlight light and the second backlight light.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to 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 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 due to the light incident on the viewpoint. It has also been proposed to project multiple image lights and form multiple virtual images at different distances from the windshield. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-119248 [Patent Document 2] Japanese Patent Application Publication No. 2019-119262 Summary of the Invention

Problems to be Solved by the Invention

[0006] In such a conventional image projection apparatus, a projection image is displayed using an image display unit such as a liquid crystal display device, and irradiation light is irradiated from the back side of the image display unit to project image light. However, in an image display unit such as a liquid crystal display device, only polarized light in a specific direction is transmitted. Therefore, when unpolarized irradiation light is incident, polarized light other than the specific direction is not used for image projection, and the light utilization efficiency decreases. Although an optical member for converting the polarization of irradiation light into a specific direction has been proposed, the apparatus tends to be enlarged in order to irradiate a large area.

[0007] Therefore, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an image projection apparatus capable of improving the utilization efficiency of irradiation light and achieving space saving.

Means for Solving the Problems

[0008] In order to solve the above problems, an image projection apparatus according to the present invention includes a light source unit that irradiates 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 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.

[0009] In such an image projection apparatus of the present invention, the unpolarized first irradiation light and second irradiation light are converted into a polarization direction along the first direction by the first polarization conversion unit and the second polarization conversion unit, and the irradiation directions of the first irradiation light and the second irradiation light intersect the emission directions of the first backlight light and the second backlight light. Therefore, it is possible to improve the utilization efficiency of irradiation light and achieve space saving.

[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 embodiment 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 embodiment 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. [Effects of the Invention]

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

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[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, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. In the following explanation, 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, which will be 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. In this embodiment, an example is shown 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, but the number of virtual images is not limited.

[0020] The windshield WS is provided in front of the driver's seat of the vehicle and is a portion that transmits visible light. The windshield WS reflects the first image light L1 and the second image light L2 incident from the image projection device 100 in the vehicle inner side surface in the viewpoint direction and transmits the light from the outside of the vehicle in the viewpoint direction. Therefore, it corresponds to the display unit in the present invention. Here, an example using the windshield WS as the display unit is shown. However, a combiner may be prepared as the display unit separately from the windshield WS, and the light from the image projection device 100 may be reflected in the viewpoint direction. Further, it is not limited to being located in front of the vehicle, and it may be arranged on the side or rear as long as it projects an image with respect to the passenger's viewpoint.

[0021] The virtual images P1, P2 are images that are displayed as if they are formed in space when the first image light L1 and the second image light L2 reflected by the windshield WS reach the passenger's viewpoint (instrument panel). The position where the virtual images P1, P2 are formed is 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 the present embodiment, the distant image displayed in the distant display area of the image irradiation unit 10 is irradiated as the first image light L1, and the near image displayed in the near display area is irradiated as the second image light L2. Examples of the distant image displayed in the distant display area include auxiliary information related to driving such as an image for alerting or emergency information. Examples of the near image displayed in the near display area include a speed and volume indicator, a traveling direction guide, and the like.

[0023] Figure 2 is a schematic cross-sectional view for explaining the outline of the image projection apparatus 100 according to the present embodiment. As shown in Figure 2, the image projection apparatus 100 includes an image irradiation unit 10, a first mirror 20, a second mirror 30, and a housing 40. In the image projection apparatus 100, each unit is controlled using a control unit (not shown) that is communicably connected to each unit. The configuration of the control unit is not limited, but examples include those provided with a CPU (Central Processing Unit) for performing information processing, a memory device, a recording medium, an information communication device, and the like. The control unit controls the operation of each unit according to a predetermined program and sends information (image information) including an image to the image irradiation unit 10.

[0024] The image irradiation unit 10 is a part that irradiates light including an image as image light to the first mirror 20 based on the image information from the control unit. In the present embodiment, an example is shown in which two pieces of image light displayed in two image display areas are irradiated to the first mirror 20 as the first image light L1 and the 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 that have reached from the image irradiation unit 10 in the direction of the second mirror 30. In the example shown in Figure 2, the first mirror 20 is shown as a reflecting mirror on a flat plate, but a concave or convex reflecting mirror may be used. Further, when the first mirror 20 is configured with a curved surface, it is not limited to a constant curvature, and a paraboloid of revolution, an ellipsoid, a free-form surface mirror, or the like can 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 reached from the first mirror 20 in the direction of the windshield WS. In the example shown in Figure 1, the second mirror 30 is shown as a free-form surface mirror with a concave shape that is optically designed to project the first image light L1 and the second image light L2 as virtual images P1 and P2.

[0027] The reflecting surfaces of the first mirror 20 and the second mirror 30 are designed such that the optical paths expand 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, the expansion of the optical path in the viewing direction includes not only the case where the optical path consistently expands after reflection, but also the case where the optical path contracts and then 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 forms the outer shape of the image projection device 100 and is a container for housing each part. The housing 40 is provided with a light emission port for emitting the first image light L1 and the second image light L2. Further, an angle adjustment unit for adjusting the angle of the second mirror 30 may be provided inside the housing 40 to adjust the irradiation angles of the first image light L1 and the second image light L2 projected onto the windshield WS and change the imaging heights of the virtual images P1 and P2. An optical filter for cutting ultraviolet light and infrared light contained in the light (external light) reaching from the outside may be provided on the housing 40.

[0029] In FIG. 2, the optical paths of the first image light L1 and the second image light L2 are drawn as a single straight line arrow. However, the actual first image light L1 and second image light L2 are those displayed in a predetermined area at the image irradiation unit 10, and have a predetermined area in a direction perpendicular to the traveling direction, as shown by the dashed line in the figure. Further, the first image light L1 and the second image light L2 may be reflected by the first mirror 20 and travel while the optical path is reduced, and may be intermediate-imaged at an intermediate imaging position F (not shown) between the first mirror 20 and the second mirror 30.

[0030] FIG. 3 is a schematic cross-sectional view for explaining the outline of the image irradiation unit 10 according to the present embodiment. As shown in FIG. 3, the image irradiation unit 10 of the present 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 shielding 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 each include a reflective polarization unit 151a and 151b, a reflecting mirror 152a and 152b, and a half-wave plate 153a and 153b.

[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. Electronic components for driving the light source unit 12 may be mounted on the substrate 11 to form a driving circuit. Further, a terminal portion (not shown) is provided on the substrate 11, and power and a control signal may be supplied from a cable or the like connected to the terminal portion.

[0032] The light source unit 12 is mounted on the substrate 11 and irradiates the image display unit 110 with irradiation light via the primary lens 14, the polarization conversion units 15a and 15b, the meniscus lenses 17a and 17b, and the 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 surface in FIG. 3). The emission color of the light source unit 12 is not particularly limited, but is white as an example in the present embodiment. In the example shown in FIG. 3, an example in which the light source unit 12 is composed of LEDs 12a and 12b is shown. Here, the LEDs 12a and 12b irradiate the first irradiation light and the second irradiation light in the present invention, respectively. In the present embodiment, the number of arrangements of the LEDs 12a and 12b is one row, but may be two rows or more. The irradiation light irradiated from the light source unit 12 is unpolarized light.

[0033] The heat sink 13 is a member for dissipating the heat generated in the light source unit 12 due to the irradiation of the irradiation light through the substrate 11, and is disposed in contact with the back surface side of the substrate 11. The material constituting the heat sink 13 is not limited, and a metal material such as aluminum or a resin mixed with a filler having high thermal conductivity can be used. The shape of the heat sink 13 is not limited, but it is preferable to include a plurality of heat radiation fins in order to enhance the heat dissipation performance.

[0034] The primary lens 14 is an optical member that is disposed in the light emission direction of the light source unit 12, condenses the irradiation light irradiated from the light source unit 12, and has a function of emitting the light as, for example, parallel light or light close to parallel light (hereinafter, both are collectively referred to as "substantially parallel light"). In FIG. 3, the primary lens 14 shows an example in which a first lens 14a, a second lens 14b, and a plate-like portion 14c are integrally formed. By integrally forming the first lens 14a and the second lens 14b via the plate-like portion 14c, it becomes possible to easily perform alignment with the LEDs 12a and 12b and adjustment of the optical axes of the first irradiation light and the second irradiation light.

[0035] The first lens 14a and the second lens 14b extend along the arrangement directions of the LEDs 12a and 12b, respectively. In the present embodiment, as an example of the first lens 14a and the second lens 14b, a TIR (Total Internal Reflection) lens provided with a refraction portion that refracts light at the center and reflection portions that reflect light on both sides of the refraction portion is used. The primary lens 14 may be provided with a plurality of collimating lenses for each of the LEDs 12a and 12b. Further, as long as the light from the LEDs 12a and 12b can be made into substantially parallel light, it is not limited to a lens, and a configuration in which a combination of a reflector and a lens or a reflector alone is used to form substantially parallel light may be adopted.

[0036] In the example shown in FIG. 3, since the LEDs 12a and 12b, which are the light source units 12, are mounted on the common substrate 11, the first lens 14a and the second lens 14b of the primary lens 14 can be integrally formed and disposed on one side of the image display unit 110. Thereby, the image irradiation unit 10 can be downsized.

[0037] The polarization converters 15a and 15b are optical components disposed on the light-exiting 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 and second backlight, respectively. The polarization converters 15a and 15b correspond to the first polarization converter and the second polarization converter of the present invention, respectively. The specific configuration of the polarization converters 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 converters 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 disposed at a predetermined angle with respect to the traveling direction of the 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 at the same inclination angle, but the inclination angles may be different.

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

[0041] Here, among the first irradiation light and the second irradiation light, the combination of the light reflected by the reflective polarizing parts 151a and 151b and the light whose polarization direction has been converted by the half-wave plates 153a and 153b corresponds to the first backlight light and the second backlight light in the present invention, respectively. In FIG. 3, an example in which the half-wave plates 153a and 153b are arranged between the reflecting mirrors 152a and 152b and the meniscus lenses 17a and 17b is shown, but the position is not limited as long as it is on the path of the polarized light in the second direction that has passed through the reflective polarizing parts 151a and 151b. As an example, the half-wave plates 153a and 153b may be arranged between the reflective polarizing parts 151a and 151b and the reflecting mirrors 152a and 152b.

[0042] The light shielding member 16 is a member made of a material that shields light and is arranged between the polarization conversion parts 15a and 15b. The light shielding member 16 is partially provided with an opening 16a, and the first irradiation light irradiated from the LED 12a can pass through the opening 16a and enter the polarization conversion part 15a. By arranging the light shielding member 16 between the polarization conversion parts 15a and 15b, stray light between the polarization conversion parts 15a and 15b can be prevented, and the first backlight light and the second backlight light can be appropriately irradiated to the distant display area 110a and the near display area 110b of the image display unit 110, respectively. In FIG. 3, the light shielding member 16 is shown in a substantially plate-like shape, but the shape and material are not limited.

[0043] Meniscus lenses 17a and 17b are optical components that adjust the light distribution of the first backlight and second backlight emitted from polarization conversion units 15a and 15b. Meniscus lenses 17a and 17b are formed to extend in a direction perpendicular to the plane of FIG. 3. In the example shown in FIG. 3, meniscus lenses 17a and 17b include a first lens region and a second lens region. Light reflected by polarization conversion units 15a and 15b enters the first lens region, and light reflected by 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 light reflected by polarization conversion units 15a and 15b and reflecting mirrors 152a and 152b travel in a direction such that the display region of image display unit 110 is uniformly illuminated. Although FIG. 3 shows an example in which the meniscus lenses 17a and 17b are used, if the light distribution of the first backlight and the second backlight is appropriate, the meniscus lenses 17a and 17b may be omitted.

[0044] Orienting lenses 18a and 18b are optical members disposed between meniscus lenses 17a and 17b and image display unit 110, and adjust the light distribution of the first backlight light and the second backlight light. Although Fig. 3 shows an example in which orientation lenses 18a and 18b are used, 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 distant display area 110a, into which the first backlight is incident, and a near display area 110b, into which the second backlight is incident. The distant display area 110a and the near display area 110b are separately provided. The distant display area 110a and the near display area 110b correspond to the first and second areas, respectively, in the present invention. While the specific configuration of the image display unit 110 is not limited, an example is 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, and the polarization direction of the polarization conversion units 15a and 15b is aligned with the specific direction.

[0046] Furthermore, a diffusion plate (not shown) that diffuses and transmits backlight may be disposed on the side (rear side) of the image display unit 110 where the backlight is incident. The diffusion plate diffuses the highly directional light polarized by the first lens 14a, the second lens 14b and the meniscus lenses 17a, 17b and outputs the light to the image display unit 110, thereby enabling the image display unit 110 to be illuminated more uniformly. 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 15a, 15b while maintaining the polarization direction of the light.

[0047] In the image projection device 100 described above, the first and second illumination lights emitted from the LEDs 12a and 12b are unpolarized lights with no particular polarization direction. The first and second illumination lights are collimated by the first lens 14a and the second lens 14b, respectively, and then enter the polarization converters 15a and 15b. The first and second illumination lights incident on the polarization converters 15a and 15b are polarized in a first direction by the reflective polarizers 151a and 151b toward the meniscus lenses 17a and 17b, and the second illumination lights polarized in a second direction are transmitted through the reflective polarizers 151a and 151b. The illumination lights (first light) reflected by the reflective polarizers 151a and 151b are 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) that passes 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 reflective polarization units 151a and 151b as second light, reflected by reflectors 152a and 152b, and directed toward image display unit 110. The second light is then transmitted through 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 reflective polarization units 151a and 151b and the second light transmitted through half-wave plates 153a and 153b are irradiated as first backlight and second backlight, each polarized in the same first direction. Half-wave plates 153a and 153b do not need to have a phase difference of exactly 50% relative to the wavelength of light; as long as they produce a phase difference close to 50%, they can rotate the polarization direction in-plane.

[0049] The first backlight light and the second backlight light polarized in the first direction pass through the meniscus lenses 17a and 17b and the orientation lenses 18a and 18b, and the light distribution is adjusted and reaches the diffusion plate respectively. In the diffusion plate, the first backlight light and the second backlight light polarized in the first direction are diffused and transmitted. As a result, the backlight light polarized in the first direction is uniformly irradiated on the back surface of the image display unit 110. Thereby, it is possible to reduce the polarization component in the second direction that is absorbed by the image display unit 110 and improve the light utilization efficiency.

[0050] In the example shown in FIG. 3, the first backlight light and the second backlight light irradiated from the polarization conversion units 15a and 15b are irradiated on the far display area 110a and the near display area 110b, which are different areas of the image display unit 110. Therefore, the first image light L1 and the second image light L2 that have passed through the far display area 110a and the near display area 110b can be separated. Thereby, an additional optical member for separating the first image light L1 and the second image light L2 can be omitted, and the image projection apparatus 100 can be downsized.

[0051] In the image projection apparatus 100 of the present embodiment, the irradiation directions of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 intersect the emission directions of the first backlight light and the second backlight light with respect to the image display unit 110. Thereby, the light source unit 12 can be disposed on the side of the image display unit 110, and while thinning the image irradiation unit 10 and increasing the utilization efficiency of the irradiation light, it is possible to save space.

[0052] In the example shown in FIG. 3, the polarization conversion unit 15a is disposed 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, and the first irradiation light incident on the polarization conversion unit 15a and the second backlight light emitted from the polarization conversion unit 15b intersect in 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 disposed are generated below the polarization conversion unit 15a and to the right of the polarization conversion unit 15b. This allows the housing (not shown) to be compact 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, thereby 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 arranged closer to the display surface of the image display unit 110 than the polarization conversion unit 15a.

[0055] As shown in FIG. 4, the LED 12b of the light source unit 12 is arranged closer to the display surface of the image display unit 110 than the LED 12a. Further, the opening 16a provided in the light shielding member 16 is provided between the LED 12a and the polarization conversion unit 15a. In the present embodiment, no space (intersection region) is provided between the meniscus lenses 17a and 17b and the polarization conversion units 15a and 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, also in the image projection apparatus 100 of the present embodiment, the irradiation directions of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 intersect the emission directions of the first backlight light and the second backlight light with respect to the image display unit 110. Thereby, the light source unit 12 can be arranged on the side of the image display unit 110, and it is possible to reduce the thickness of the image irradiation unit 10, improve the utilization efficiency of the irradiation light, and save space.

[0057] (Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. 5. Description of the content overlapping with the first embodiment will be omitted. FIG. 5 is a schematic cross-sectional view for explaining the outline of the image irradiation unit 10 according to the present embodiment. In the present embodiment, it is different from the first embodiment in that the area of the far display region 110a of the image display unit 110 is larger than that of the near display region 110b.

[0058] As shown in FIG. 4, since the area of the distant display region 110a is larger than that of the near display region 110b, the distance between the reflective polarizing portion 151a and the mirror 152a in the polarization conversion unit 15a is increased to increase the irradiation area of the first backlight light to be irradiated. At this time, the areas of the reflective polarizing portion 151a, the mirror 152a, the half-wavelength plate 153a, the meniscus lens 17a, and the alignment lens 18a are also increased as necessary. Further, since the luminance decreases due to the increase in the irradiation area of the first backlight light emitted from the polarization conversion unit 15a, the amount of light irradiated from the LED 12a may be increased to compensate for the decrease in luminance. Specifically, the number of the LEDs 12a is increased, and the mounting density on the substrate 11 is made larger than that of the LED 12a.

[0059] As shown in FIG. 1, the virtual image P1 of the distant image (first image) displayed in the distant display region 110a (first region) 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 region 110b (second region). Therefore, by making the distant display region 110a have a larger area than the near display region 110b, the visibility of the virtual image P1 of the distant image can be improved.

[0060] Also in the image projection apparatus 100 of the present embodiment, the irradiation directions of the first irradiation light and the second irradiation light irradiated from the LEDs 12a and 12b of the light source unit 12 intersect the emission directions of the first backlight light and the second backlight light with respect to the image display unit 110. Thereby, the light source unit 12 can be arranged on the side of the image display unit 110, and it is possible to reduce the thickness of the image irradiation unit 10, increase the utilization efficiency of the irradiation light, and save space.

[0061] (Modification examples of the polarization conversion units 15a and 15b) Next, a modified example of the polarization conversion units 15a and 15b will be described with reference to FIG. 6. Descriptions of the content overlapping with the first embodiment will be omitted. FIG. 6 is a schematic diagram for explaining a modified example of the polarization conversion units 15a and 15b shown in the first to third embodiments. As shown in FIG. 6, between the reflective polarizing parts 151a and 151b and the reflecting mirrors 152a and 152b, half-wave plates 153a and 153b are arranged on the back side of the reflective polarizing parts 151a and 151b.

[0062] In the modified example of the polarization conversion units 15a and 15b shown in FIG. 6, for the incident first irradiation light and second irradiation light, the polarization in the first direction is reflected by the reflective polarizing parts 151a and 151b in the direction of the meniscus lenses 17a and 17b, and the polarization in the second direction passes through the reflective polarizing parts 151a and 151b. Here, the polarization of the irradiation light (first light) reflected by the reflective polarizing parts 151a and 151b is polarized in the first direction that passes through the image display unit 110. Also, the polarization of the irradiation light (second light) passing through the reflective polarizing parts 151a and 151b is polarized in the second direction that is substantially orthogonal to the first direction.

[0063] Also, for the first irradiation light and second irradiation light, the second light whose polarization in the second direction passes through the reflective polarizing parts 151a and 151b further passes through the half-wave plates 153a and 153b, and the polarization is rotated by 90 degrees in the plane and converted into the polarization in the first direction. Also, the second light passing through the half-wave plates 153a and 153b is reflected by the reflecting mirrors 152a and 152b and irradiated in the direction of the image display unit 110. Thereby, the first light reflected by the reflective polarizing parts 151a and 151b and the second light passing through the half-wave plates 153a and 153b are irradiated as the first backlight light and the second backlight light whose polarization directions are the same first direction.

[0064] Even when using the polarization conversion units 15a and 15b of this modification example, the first backlight light and the second backlight light polarized in the first direction pass through the meniscus lenses 17a and 17b and the alignment lenses 18a and 18b, and the light distribution is adjusted and reaches the diffusion plate respectively. In the diffusion plate, the first backlight light and the second backlight light polarized in the first direction are diffused and transmitted. As a result, the backlight light polarized in the first direction is uniformly irradiated on the back surface of the image display unit 110. Thereby, it is possible to reduce the polarization component in the second direction that is absorbed by the image display unit 110 and improve the light utilization efficiency.

[0065] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in 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 Reference Numerals

[0066] 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-like part 151a, 151b…Reflective polarizing part 152a, 152b…Mirror 153a, 153b…Half-wave plate 15a, 15b…Polarization conversion unit 16…Light shielding member 16a…Opening 17a, 17b…Meniscus lens 18a, 18b…Alignment lens 110…Image display unit 110a…Distant display area 110b... near display area

Claims

1. A light source unit that irradiates first irradiation light and second irradiation light without polarization, 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, An image display unit having the first backlight light and the second backlight light incident from the back surface and emitting image light from the display surface, An image projection apparatus, characterized in that 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, 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, The image projection apparatus, characterized in that the first lens and the second lens are integrally formed.

3. The image projection apparatus according to claim 1, 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, The light shielding member is partially provided with an opening, and the first irradiation light passes through the opening and enters the first polarization conversion unit. The image projection apparatus is characterized in that.

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

5. The image projection apparatus according to claim 1, The image display unit has a first region where the first backlight light is incident and a second region where the second backlight light is incident, The image projection apparatus, characterized in that the first region and the second region are separated.

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

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

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