Image projection device

Abstract

To provide an image projection device that can suppress degradation due to temperature rise in the image irradiation area. [Solution] An image projection device (100) for projecting a projected image onto a display unit for displaying a virtual image, comprising: an image illumination unit (10) for irradiating image light; projection optical units (20, 30) for imaging the image light at a first distance from the viewpoint position via the display unit; and a polarizing plate (51) that transmits polarization in a first direction and blocks polarization in a second direction intersecting the first direction, wherein the polarizing plate (51) is attached to a light-transmitting support plate (52).

Description

Technical Field

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

Background Art

[0002] Conventionally, as a device for displaying various information in a vehicle, an instrument panel that lights up icons has been used. In addition, with the increase in the amount of information to be displayed, it has also been proposed to embed an image display device in the instrument panel or to configure the entire instrument panel with an image display device.

[0003] However, since the instrument panel is located below the front glass (windshield) of the vehicle, in order for passengers such as the driver to view the information displayed on the instrument panel, it is necessary to move the line of sight downward during driving, which is not preferable. Therefore, an image projection device such as a head-up display (hereinafter referred to as HUD: Head Up Display) has been proposed that projects an image onto the front glass so that passengers can read the information when viewing the front of the vehicle (for example, see Patent Documents 1 and 2).

[0004] The image projection devices of Patent Documents 1 and 2 irradiate irradiation light including an image with the image projection device, reflect the irradiation light with a free-form surface mirror or the like, and cause an image to be formed in space through a display unit such as a windshield and reach the position of the passenger's viewpoint. As a result, the passenger can recognize that an image is displayed at the imaging position in the depth direction by the irradiation light incident on the viewpoint.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Such image projection devices use liquid crystal displays or the like as the image illumination unit that displays the image. However, because the image illumination unit needs to display the image and project image light, it is susceptible to heat generation from the light source and the influence of ambient light such as sunlight, which can cause its temperature to rise easily. The image illumination unit tends to degrade faster in high-temperature environments, so it is required to reduce its temperature as much as possible.

[0007] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and aims to provide an image projection device that can suppress deterioration due to temperature rise in the image irradiation section. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides an image projection device for projecting a projection image onto a display unit for displaying a virtual image, comprising: an image illumination unit for irradiating image light; a projection optical unit for imaging the image light at a first distance from the viewpoint position via the display unit; and a polarizing plate that transmits polarization in a first direction and blocks polarization in a second direction intersecting the first direction, wherein the polarizing plate is bonded to a light-transmitting support plate.

[0009] In the image projection apparatus of the present invention, by blocking the polarization in a second direction that does not affect the irradiation of image light in the image irradiation unit with a polarizing plate, the energy of the light reaching the image irradiation unit can be halved, thereby suppressing degradation due to temperature rise in the image irradiation unit.

[0010] Furthermore, in one aspect of the present invention, the polarizing plate is an absorptive polarizing plate that absorbs polarization in the second direction, and the support plate is made of a material with a thermal conductivity of 0.1 W / m·K or higher.

[0011] Furthermore, in one aspect of the present invention, the support plate is located on the side of the polarizing plate opposite to the image irradiation portion.

[0012] In addition, in one aspect of the present invention, the support plate is made of sapphire.

[0013] In addition, in one aspect of the present invention, the support plate has a light transmittance of 70% or more.

[0014] In addition, in one aspect of the present invention, the support plate has a thickness in the range of 1 mm or more and 5 mm or less.

[0015] In addition, in one aspect of the present invention, the polarizing plate is disposed on the optical path of the image light from the image irradiation unit to the display unit, and the polarization direction of the image light is the first direction.

[0016] In addition, in one aspect of the present invention, the polarizing plate is a reflective polarizing plate that reflects polarization in the second direction, and the support plate has a linear expansion coefficient of 100×10 -7 / K or less and is made of the following material.

[0017] In addition, in one aspect of the present invention, the support plate has a thickness in the range of 1 mm or more and 5 mm or less.

[0018] In addition, in one aspect of the present invention, a light scattering plate that scatters light is bonded to the surface of the support plate on the side opposite to the polarizing plate.

[0019] In addition, in one aspect of the present invention, the image irradiation unit includes an image display unit that displays an image and a light source unit that irradiates irradiation light to the image display unit, and the polarizing plate is disposed between the image display unit and the light source unit.

Advantages of the Invention

[0020] In the present invention, it is possible to provide an image projection apparatus that can suppress deterioration due to temperature rise of the image irradiation unit.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic diagram showing projection of a virtual image P using the image projection apparatus 100 according to the first embodiment. [Figure 2] It is a schematic cross-sectional view for explaining the outline of the image projection device 100. [Figure 3] It is a schematic cross-sectional view for explaining the temperature rise of the polarizing plate 51 due to external light in the image projection device 100. [Figure 4] It is a schematic diagram for explaining heat dissipation in the support plate 52. [Figure 5] It is a schematic cross-sectional view for explaining the outline of the image irradiation unit 10 according to the second embodiment.

Embodiments for Carrying Out the Invention

[0022] (First Embodiment) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and repeated explanations will be omitted as appropriate. In the following description, a form in which the image projection device 100 according to the present invention is applied to a HUD mounted on a vehicle or the like will be exemplified and described.

[0023] FIG. 1 is a schematic diagram showing the projection of the virtual image P using the image projection device 100 according to the present embodiment. As shown in FIG. 1, the image light projected from the image projection device 100 is irradiated toward the windshield (display unit) WS through an opening provided in the dashboard DB, reflected by the windshield WS, and irradiated to the driver's viewpoint position E. The driver visually recognizes the virtual image P formed on the extension of the optical path through which the image light has entered. The solid lines and broken lines shown in FIG. 1 schematically represent the light beam of the image light irradiated from the image projection device 100, the optical path of the image light reflected by the windshield WS and reaching the viewpoint position E, and the extension thereof. The actual image light is displayed in a predetermined area in the image irradiation unit 10 and has a predetermined area in a direction perpendicular to the traveling direction.

[0024] The windshield WS is a visible light-transmitting part located in front of the driver's seat of the vehicle. On the inner surface of the vehicle, the windshield WS reflects the image light incident from the image projection device 100 toward the viewpoint direction and transmits light from outside the vehicle toward the viewpoint direction, thus corresponding to the display unit in this invention. Here, an example using the windshield WS as the display unit is shown, but a combiner may be prepared as a separate display unit from the windshield WS, and light from the second mirror 30 may be reflected toward the viewpoint direction. Furthermore, it is not limited to being located in front of the vehicle; it may be placed to the side or rear as long as it projects an image toward the occupant's viewpoint.

[0025] The virtual image P is an image that appears to be projected into space when the image light reflected by the windshield WS reaches the driver's or other viewpoint position E (eyebox). The position where the virtual image P is projected is determined by the angle of spread of the image light emitted from the image projection device 100 as it travels in the direction of the viewpoint after being reflected by the projection optical unit (not shown in Figure 1) and the windshield WS. The content of the image projected as the virtual image P may include warning images, auxiliary information related to driving such as emergency information, volume indicators, and direction of travel guides.

[0026] Figure 2 is a schematic cross-sectional view illustrating the outline of the image projection device 100. As shown in Figure 2, the image projection device 100 comprises an image irradiation unit 10, a first mirror 20, a second mirror 30, a cover unit 40, and a polarization blocking unit 50. The polarization blocking unit 50 also includes a polarizing plate 51 and a support plate 52.

[0027] Although not shown in Figure 2, the image projection device 100 includes a housing, and the image irradiation unit 10, the first mirror 20, and the second mirror 30 are housed within the housing. An opening is provided at the top of the housing, and the cover 40 covers this opening, sealing the interior. The shape and materials of the housing are not limited, and light-blocking resin or metal materials can be used.

[0028] In the image projection device 100 shown in Figure 2, each part is controlled by a control unit that is connected to each part via information communication. The configuration of the control unit is not limited, but one example is one that includes a CPU (Central Processing Unit) for information processing, a memory device, a recording medium, and an information communication device. The control unit controls the operation of each part according to a predetermined program and sends information containing images (image information) to the image projection unit 10.

[0029] The image illumination unit 10 is the part that illuminates the image with image light based on image information from the control unit. The specific configuration of the image illumination unit 10 is not limited, and conventionally known devices such as liquid crystal displays and organic EL displays can be used. As an example, a device is used in which the illumination light is emitted from the back side of a liquid crystal display using a light-emitting diode (LED).

[0030] The first mirror 20 is an optical element that receives image light emitted from the image illumination unit 10 and reflects the image light toward the second mirror 30. In the example shown in Figure 2, a flat mirror is shown as the first mirror 20. Here, a flat mirror is shown as the first mirror 20, but a concave or convex reflecting mirror may also be used, or a free-form mirror may be used.

[0031] The second mirror 30 is an optical element that receives the image light reflected by the first mirror 20 and reflects the image light in the direction of the windshield WS. In the example shown in Figure 2, the second mirror 30 is shown as an optically designed free-form mirror necessary for projecting the image light as a virtual image P. In the example shown in Figure 2, the second mirror 30 is located below the cover portion 40. Furthermore, the second mirror 30 may be made capable of changing its tilt angle with respect to the horizontal direction, thereby changing the projection direction of the image light and moving the projection position of the virtual image P in the vertical direction.

[0032] The reflective surfaces of the first mirror 20 and the second mirror 30 are designed so that the optical diameter expands in the direction of the driver's viewpoint in order to project image light as a virtual image P through the windshield WS. Here, expansion of the optical diameter in the direction of the viewpoint includes not only cases where the optical diameter consistently expands after reflection, but also cases where the optical diameter contracts, forms an image at an intermediate point, and then expands. The combination of the first mirror 20 and the second mirror 30 has the function of projecting image light through the windshield WS and corresponds to the projection optics unit in the present invention.

[0033] The cover portion 40 is made of a material that transmits image light and is positioned to cover the opening of the housing portion. Although not shown in Figure 2, the cover portion 40 is fixed to the housing portion in a way that prevents any gaps from forming between the two, thereby preventing dust and dirt from entering the inside of the housing portion. The material that constitutes the cover portion 40 is not limited, and known resin materials or glass that transmit image light can be used.

[0034] The polarization blocking section 50 is an optical component formed by bonding a polarizing plate 51 and a support plate 52 together, which transmits image light, and is positioned on the optical path of the image light 1 from the image illumination section 10 to the windshield WS. Figure 2 shows an example in which the polarizing plate 51 of the polarization blocking section 50 is located on the image illumination section 10 side and the support plate 52 is located on the first mirror 20 side, but the support plate 52 may also be on the image illumination section 10 side. However, in order to suppress the temperature rise of the polarizing plate 51 due to ambient light, as will be described later, it is preferable that the support plate 52 be located on the side of the polarizing plate 51 opposite to the image illumination section 10. Also, Figure 2 shows an example in which the polarization blocking section 50 is flat, but it may also be curved. Also, Figure 2 shows an example in which the polarization blocking section 50 is positioned between the image illumination section 10 and the first mirror 20, but it may also be between the first mirror 20 and the second mirror 30, or between the second mirror 30 and the cover section 40.

[0035] As shown in Figure 2, it is preferable to position the polarization blocking section 50 at a predetermined angle with respect to the optical path of the image light. By tilting it with respect to the optical path of the image light, even if ambient light incident from above the cover section 40 is reflected by the second mirror 30 and the first mirror 20 and reaches the polarization blocking section 50, and a portion of the ambient light is re-reflected on its surface, it is possible to suppress it from reaching the viewpoint position E via the same optical path as the image light.

[0036] The polarizing plate 51 is an absorption-type polarizing plate having optical properties that transmit polarized light in the direction of the transmission axis and absorb polarized light in the direction of the absorption axis perpendicular to the transmission axis, and a known polarizing plate or polarizing film can be used. The polarizing plate 51 is bonded to the support plate 52, and the heat generated in the polarizing plate 51 is well transferred to the support plate 52. The method of bonding the polarizing plate 51 and the support plate 52 is not limited, and conventionally known adhesives can be used. In this case, it is preferable to use an adhesive material that transmits image light well.

[0037] Here, the transmission axis direction corresponds to the first direction in the present invention, and the absorption axis direction corresponds to the second direction in the present invention. Furthermore, it is preferable that the transmittance of the transmission axis is uniform within the plane of the polarizing plate 51. In addition, it is preferable that the transmission axis of the polarizing plate 51 is arranged to transmit the polarization of the image light irradiated from the image irradiation unit 10. For example, when a liquid crystal display device is used as the image display unit 17 of the image irradiation unit 10, the polarization direction of the image light irradiated by the liquid crystal display device is set to be the direction of the transmission axis of the polarizing plate 51.

[0038] The support plate 52 is made of a light-transmitting material and is the part to which the polarizing plate 51 is bonded. The material that makes up the support plate 52 is not limited, but in order to dissipate the heat generated by the polarizing plate 51 well, as will be described later, it is preferable that the thermal conductivity is greater than that of the polarizing plate 51, more preferably that it is made of a material with a thermal conductivity of 0.1 W / m·K or more, and more preferably that it is 0.15 W / m·K or more. In addition, since the support plate 52 is placed in the optical path of the image light and the image light is transmitted through it, it is preferable that the light transmittance is 70% or more, and more preferably that it is 80% or more. Specific examples of the support plate 52 include sapphire, and it is particularly preferable to use a sapphire substrate with high thermal conductivity and light transmittance.

[0039] The shape and structure of the support plate 52 are not limited, but in order to minimize the influence on the optical path of image light and ambient light, it is preferable to use a flat plate as shown in Figure 2. Alternatively, a curved shape may be used to refract the image light. Furthermore, since the polarizing plate 51 is bonded to the support plate 52, it needs to have sufficient mechanical strength to support the polarizing plate 51. Therefore, the thickness of the support plate 52 is preferably in the range of 1 mm to 5 mm, and more preferably in the range of 2 mm to 3 mm. If the thickness of the support plate 52 is smaller than these ranges, handling performance will decrease in the process of bonding the polarizing plate 51, which is undesirable. Also, if the thickness of the support plate 52 is larger than these ranges, it will lead to an increase in weight and a decrease in light transmittance, which is undesirable.

[0040] Figure 3 is a schematic cross-sectional view illustrating the temperature rise of the polarizing plate 51 in the image projection device 100 due to ambient light. The arrows in Figure 3 schematically represent the optical path of ambient light, such as sunlight, that enters the image projection device 100 from above the windshield WS. A portion of the ambient light entering from the cover portion 40 of the image projection device 100 travels in the reverse direction of the optical path of the image light shown in Figure 2, is reflected by the second mirror 30 and the first mirror 20, and travels towards the image illumination unit 10. At this time, the ambient light reflected by the first mirror 20 and reaching the image illumination unit 10 passes through the polarizing plate 51, so only the transmission axis direction changes, and its energy is halved compared to before passing through the polarizing plate 51. As a result, the temperature rise due to ambient light reaching the image illumination unit 10 is suppressed.

[0041] In this case, since the polarizing plate 51 is an absorption type polarizing plate, polarization in the direction of the absorption axis is absorbed by the polarizing plate 51, causing the temperature of the polarizing plate 51 to rise. In particular, if the first mirror 20 or the second mirror 30 is made of a concave mirror, the ambient light reflected by the second mirror 30 and the first mirror 20 is focused, and ambient light may be concentrated in a part of the polarizing plate 51. When ambient light is concentrated in a part of the polarizing plate 51, the temperature rises locally. If the localized temperature rise in the polarizing plate 51 continues, deformation or discoloration of the polarizing plate 51 may occur. As described above, since the polarizing plate 51 is placed in the optical path of the image light, deformation or discoloration of the polarizing plate 51 is undesirable because it degrades the display quality of the virtual image P.

[0042] Figure 4 is a schematic diagram illustrating heat dissipation in the support plate 52. The polarizing plate 51 bonded to the support plate 52 is not shown in the diagram. The circles shown in the figure schematically represent a locally high-temperature spot region 52a that is created when ambient light is concentrated in a part of the polarizing plate 51. The heat generated in the spot region 52a on the polarizing plate 51 is quickly transferred to the support plate 52, which has a higher thermal conductivity than the polarizing plate 51. In addition, as shown by the arrows in the figure, heat is transferred radially from the spot region 52a on the polarizing plate 51 in the in-plane direction. As a result, the localized spot region 52a on the polarizing plate 51 is efficiently cooled by the support plate 52, and the local temperature rise of the polarizing plate 51 and the resulting deformation and discoloration can be suppressed.

[0043] Figures 2 and 3 show an example in which the support plate 52 is placed on the side of the polarizing plate 51 facing the first mirror 20. However, the support plate 52 may also be placed on the side of the polarizing plate 51 facing the image irradiation section 10. However, since the temperature of the polarizing plate 51 tends to rise on the side of the first mirror 20 where ambient light is incident, it is preferable to place the support plate 52 on the side of the first mirror 20.

[0044] As described above, in the image projection device 100 of this embodiment, by blocking the polarization in a second direction that does not affect the irradiation of image light in the image irradiation unit 10 with the polarizing plate 51, the energy of the light reaching the image irradiation unit 10 is halved, and deterioration due to temperature rise in the image irradiation unit 10 can be suppressed. Furthermore, by bonding the polarizing plate 51 to a support plate 52 with a thermal conductivity of 0.1 W / m·K or higher, local temperature rise of the polarizing plate 51 can be suppressed, and deterioration of the display quality of the virtual image P due to deformation or discoloration of the polarizing plate 51 can be suppressed.

[0045] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figure 5. Details that overlap with the first embodiment will be omitted from the description. Figure 5 is a schematic cross-sectional view illustrating the outline of the image illumination unit 10 according to this embodiment. As shown in Figure 5, the image illumination unit 10 of this embodiment includes a substrate unit 11, a light source unit 12, a heat sink unit 13, a case unit 14, a lens unit 15, a polarization blocking unit 16, and an image display unit 17. The polarization blocking unit 16 also includes a support plate 16a, a light scattering plate 16b, and a polarizing plate 16c.

[0046] The substrate portion 11 is a component on which a wiring pattern is formed on one surface and on which the light source portion 12 is mounted. Electronic components for driving the light source portion 12 may be mounted on the substrate portion 11 to form a drive circuit. The substrate portion 11 may also be provided with terminal portions (not shown), and power and control signals may be supplied from cables or the like connected to these terminal portions.

[0047] The light source unit 12 is mounted on the substrate unit 11 and is a component that irradiates the image display unit 17 with backlight light via the lens unit 15 and the polarization blocking unit 16. The light source unit 12 is, for example, a semiconductor light-emitting element such as an LED (Light Emitting Diode). The light-emitting color of the light source unit 12 is not particularly limited, but in this embodiment, it is white as an example. In this embodiment, an example is shown in which three light source units 12 are mounted on the substrate unit 11, but the number and arrangement are not limited.

[0048] The heat sink section 13 is mounted on the surface side of the substrate section 11 and dissipates heat generated in the light source section 12 by backlight irradiation from the back side. The material and shape of the heat sink section 13 are not limited, and various conventionally proposed heat sinks can be used. In addition, multiple heat dissipation fins may be provided on the back side of the heat sink section 13. The material constituting the heat sink section 13 is not limited as long as it has high thermal conductivity, and examples include copper and aluminum.

[0049] The case portion 14 houses the substrate portion 11, the light source portion 12, the lens portion 15, and the polarization blocking portion 16, and also holds the image display portion 17. An opening is provided on the top surface of the case portion 14, and the image display portion 17 is positioned in the opening. Backlight light emitted from the light source portion 12 reaches the image display portion 17 through the opening, and image light is projected onto the outside of the image illumination portion 10.

[0050] The lens unit 15 is an optical element positioned in the direction of light emission from the light source unit 12, which focuses the light emitted from the light source unit 12 and emits it as, for example, parallel light or light that is close to parallel light (hereinafter, both are collectively referred to as "approximately parallel light"). Figure 5 shows an example using one lens unit 15, but multiple lenses may be combined to adjust the light distribution of the light emitted onto the image display unit 17.

[0051] The polarization blocking section 16 is an optical component formed by bonding a support plate 16a, a light scattering plate 16b, and a polarizing plate 16c together, and is placed between the light source section 12 and the image display section 17. Figure 5 shows a flat plate example of the polarization blocking section 16, but it may also be curved. Also, Figure 5 shows an example in which the polarization blocking section 16 is placed between the lens section 15 and the image display section 17, but it may also be placed between the light source section 12 and the lens section 15.

[0052] The support plate 16a is made of a light-transmitting material, with a light-scattering plate 16b bonded to one side and a polarizing plate 16c bonded to the other side, and it is the part that supports both. The method of bonding the light-scattering plate 16b and the polarizing plate 16c to the support plate 16a is not limited, and conventionally known adhesives can be used.

[0053] The light scattering plate 16b is positioned on the back side of the image display unit 17 and is an optical element that diffuses and transmits backlight light. The light scattering plate 16b diffuses the highly directional light refracted by the lens unit 15 and emits it to the image display unit 17, functioning to illuminate the image display unit 17 more uniformly. It is preferable to use an optical element as the light scattering plate 16b that diffuses and transmits backlight light while maintaining the polarization direction of the backlight light that has passed through the polarizing plate 16c.

[0054] The polarizing plate 16c is a polarizing plate having optical properties that transmit polarized light in the direction of the transmission axis and block polarized light perpendicular to the direction of the transmission axis, and a known polarizing plate or polarizing film can be used. Here, the direction of the transmission axis of the polarizing plate 16c corresponds to the first direction in the present invention, and the direction perpendicular to the transmission axis corresponds to the second direction in the present invention. Furthermore, the transmission axis of the polarizing plate 16c is set to be the same as the polarization direction transmitted by the polarizing filter provided on the incident side of the image display unit 17. The polarizing plate 16c may be an absorbing polarizing plate that absorbs polarized light perpendicular to the direction of the transmission axis, or a reflective polarizing plate that reflects polarized light perpendicular to the direction of the transmission axis. In order to suppress the temperature rise due to light absorption in the polarization blocking unit 16, it is preferable to use a reflective polarizing plate as the polarizing plate 16c.

[0055] The image display unit 17 is the part that displays a projected image in response to an image signal from the control unit. When backlight light is shone onto the projected image displayed on the image display unit 17, image light is emitted from the image display unit 17. The specific configuration of the image display unit 17 is not limited, and for example, a liquid crystal display device can be used.

[0056] The backlight light emitted from the light source unit 12 is refracted by the lens unit 15, passes through the polarization blocking unit 16, and enters the image display unit 17. At this time, the backlight light is unpolarized until it enters the polarizing plate 16c of the polarization blocking unit 16, and when it passes through the polarizing plate 16c, only the polarization in the direction of the transmission axis is transmitted. The backlight light that enters the image display unit 17 is polarized in the direction of the transmission axis of the polarizing plate 16c, but since the polarization direction matches the transmission axis of the polarizing filter provided on the incident side of the image display unit 17, the image light can be projected by the backlight light. Here, the unpolarized backlight light emitted from the light source unit 12 has the polarization perpendicular to the transmission axis blocked by the polarizing plate 16c, so no absorption of backlight light occurs in the polarizing filter of the image display unit 17. This makes it possible to suppress the temperature rise of the image display unit 17 due to the unpolarized backlight light.

[0057] The material constituting the support plate 16a is not limited, but in order to suppress deformation of the light scattering plate 16b or polarizing plate 16c due to temperature changes, the coefficient of linear expansion should be 100 × 10 -7 It is preferable that the material is composed of a material with a temperature of / K or less. The support plate 16a is 100 × 10 -7 The material is composed of materials with a coefficient of thermal expansion of 1 / K or lower, and a light scattering plate 16b and a polarizing plate 16c are bonded to both sides of it. This suppresses deformation of the light scattering plate 16b and the polarizing plate 16c due to the difference in their coefficients of thermal expansion when high-temperature or low-temperature tests are performed.

[0058] Furthermore, the thickness of the support plate 16a is preferably in the range of 1 mm to 5 mm, and more preferably in the range of 2 mm to 3 mm. If the thickness of the support plate 16a is smaller than these ranges, it is undesirable because there will be insufficient mechanical strength to suppress deformation of the light scattering plate 16b or polarizing plate 16c due to temperature changes. Also, if the thickness of the support plate 16a is larger than these ranges, it is undesirable because it is more likely to affect the backlight light due to a decrease in light transmittance and internal reflection. A specific example of the support plate 16a is a glass substrate. The shape and structure of the support plate 16a are not limited, but in order to minimize the effect on the backlight light, it is preferable to use a flat plate as shown in Figure 5.

[0059] As described above, in the image projection device 100 of this embodiment, by blocking the polarization in the second direction, which does not affect the irradiation of image light in the image irradiation unit 10, with the polarizing plate 16c, the energy of the light reaching the image irradiation unit 10 is halved, and deterioration due to temperature rise of the image irradiation unit 10 can be suppressed. Also, the coefficient of linear expansion is 100 × 10 -7 By bonding a light scattering plate 16b and a polarizing plate 16c to both sides of a support plate 16a with a coefficient of thermal expansion of 0.5K or less, deformation due to the difference in coefficients of thermal expansion can be suppressed.

[0060] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0061] 100…Image projection device 10…Image illumination area 20…First Mirror 30...Second Mirror 40...Cover part 16,50... Polarization blocking section 11... Circuit board section 12...Light source section 13… Heatsink section 14…Case section 15…Lens part 16a...Support plate 16b...Light scattering plate 16c,51...Polarizing plate 17…Image display section 52...Support plate 52a... Spot area

Claims

1. An image projection device that projects a projected image onto a display unit for displaying a virtual image, An image illumination unit that emits image light, A projection optical unit that projects the image light onto a first distance from the viewpoint position via the display unit, It comprises a polarizing plate that transmits polarization in a first direction and blocks polarization in a second direction intersecting the first direction, The image projection device is characterized in that the polarizing plate is bonded to a light-transmitting support plate.

2. An image projection device according to claim 1, The polarizing plate is an absorption type polarizing plate that absorbs polarization in the second direction, The image projection device is characterized in that the support plate is made of a material with a thermal conductivity of 0.1 W / m·K or higher.

3. An image projection device according to claim 2, The image projection apparatus is characterized in that the support plate is located on the side of the polarizing plate opposite to the image irradiation portion.

4. An image projection device according to claim 2, The image projection device is characterized in that the support plate is made of sapphire.

5. An image projection device according to claim 2, The image projection device is characterized in that the support plate has a light transmittance of 70% or more.

6. An image projection device according to claim 2, The image projection device is characterized in that the support plate has a thickness in the range of 1 mm to 5 mm.

7. An image projection device according to any one of claims 2 to 6, The image projection apparatus is characterized in that the polarizing plate is arranged on the optical path of the image light from the image irradiation unit to the display unit, and the polarization direction of the image light is the first direction.

8. An image projection device according to claim 1, The polarizing plate is a reflective polarizing plate that reflects polarization in the second direction, The support plate has a coefficient of thermal expansion of 100 × 10 －７ An image projection device characterized by being composed of materials with a temperature of / K or lower.

9. An image projection device according to claim 8, An image projection device characterized in that the thickness of the support plate is in the range of 1 mm to 5 mm.

10. An image projection device according to claim 8, The image projection device is characterized in that a light-scattering plate is attached to the support plate on the side opposite to the polarizing plate.

11. An image projection device according to any one of claims 8 to 10, The image illumination unit comprises an image display unit that displays an image and a light source unit that illuminates the image display unit with illumination light. The image projection device is characterized in that the polarizing plate is arranged between the image display unit and the light source unit.

Images