Image projection device

Abstract

Provided is an image projection device capable of suppressing deterioration due to temperature rise of an image display unit. An image projection device (100) projects a projection image onto a display unit for displaying a virtual image, and comprises: an image irradiation unit (10) that performs irradiation with image light; a projection optical unit that forms an image of the image light at a first distance from a viewpoint position via the display unit; and a casing unit that accommodates the image irradiation unit (10) and the projection optical unit. The image irradiation unit (10) has: a light source unit (12) that performs irradiation with light; an image display unit (20) that displays an image; and a housing unit (14) that accommodates the light source unit (12) therein and holds the image display unit. The housing unit (14) has a temperature rise suppression unit (16) that suppresses heat transfer to the image display unit (20).

Description

Image projection device ,

[0007] ,

[0006] , ,

[0005] ,

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

[0002] Conventionally, an instrument panel that lights up icons has been used as a device for displaying various types of information inside a vehicle. 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 a passenger such as a driver to visually recognize 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 information can be read when the passenger visually recognizes the front of the vehicle. (See, for example, Patent Documents 1 and 2).

[0004] A conventional image projection device irradiates irradiation light including an image from an image irradiation unit, reflects the irradiation light with a free-form surface mirror or the like, and causes 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.

[0005] Japanese Patent Application Laid-Open No. 2019-119248, Japanese Patent Application Laid-Open No. 2019-119262

[0006] In such an image projection device, a liquid crystal display device or the like is used as an image display unit for displaying an image. However, since the image display unit needs to display an image and project image light, there is a problem that it is easily affected by heat generation from a light source unit that irradiates light and external light such as sunlight, and the temperature easily rises. The image display unit tends to deteriorate more rapidly in a high-temperature environment, and it is required to reduce the temperature as much as possible.

[0007] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an image projection device capable of suppressing deterioration due to temperature rise of an image display unit.

[0008] To solve the above problems, the present invention provides an image projection device for projecting a projected image onto a display unit for displaying a virtual image, comprising: an image irradiation 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 housing unit for housing the image irradiation unit and the projection optical unit, wherein the image irradiation unit comprises a light source unit for irradiating light, an image display unit for displaying an image, and a housing unit for housing the light source unit and holding the image display unit, and the housing unit is characterized by having a temperature rise suppression unit for suppressing heat transfer to the image display unit.

[0009] In the image projection apparatus of the present invention, the housing portion has a housing portion that holds the image display portion, and the housing portion has a temperature rise suppression portion that suppresses the transfer of heat to the image display portion, thereby suppressing deterioration of the image display portion due to temperature rise.

[0010] Furthermore, in one aspect of the present invention, the temperature rise suppression portion is composed of a two-layer structure consisting of an inner layer and an outer layer of the housing portion, and the inner layer is made of a material with a lower light absorption rate than the outer layer.

[0011] Furthermore, in one aspect of the present invention, the image irradiation unit has a heat sink unit that dissipates heat from the light source unit, and the heat sink unit is made of a material that has a higher light absorption rate than the inner layer on the inside of the housing unit.

[0012] Furthermore, in one aspect of the present invention, the housing portion has a heat dissipation portion on at least a part of its outer surface that has a higher thermal conductivity than the inner surface, and the heat dissipation portion is in contact with the image display portion.

[0013] Furthermore, in one aspect of the present invention, the heat dissipation portion is made of a metal material and is integrally molded with the inner surface.

[0014] Furthermore, in one aspect of the present invention, a partition wall is provided inside the housing portion that separates the space in which the light source portion is provided from the space in which the image display portion is provided, and the partition wall is made of a light-transmitting material.

[0015] Furthermore, in one aspect of the present invention, the housing portion is provided with a heat insulating layer above the image display portion.

[0016] Furthermore, in one aspect of the present invention, the heat insulating layer is provided on the top surface of the housing and has a double-layer structure with an air layer in between.

[0017] Furthermore, in one aspect of the present invention, the image display unit has a display area in which part of it displays the image, a non-display area in which part of it does not display the image, and a mask portion arranged on the display surface side of the image display unit, with an opening formed therein that corresponds to the display area, and the mask portion is provided with a temperature measuring unit near the opening.

[0018] The present invention provides an image projection device that can suppress deterioration due to temperature rise in the image display unit.

[0019] This is a schematic diagram showing the projection of a virtual image P using the image projection device 100 according to the first embodiment. This is a schematic diagram illustrating the heat insulation effect of the image projection device 100. This is a schematic cross-sectional diagram illustrating the structure of the image irradiation unit 10 according to the first embodiment. This is a schematic cross-sectional diagram illustrating the structure of the image irradiation unit 10 according to the second embodiment. This is a schematic cross-sectional diagram illustrating the structure of the image irradiation unit 10 according to the third embodiment. This is a schematic diagram illustrating the temperature measurement of the image display unit 20 according to the fourth embodiment. Figure 6(a) shows the positional relationship between the image display unit 20, the mask unit 80, the temperature measurement unit 81 and the opening 82, and Figure 6(b) schematically shows the entire display area of ​​the image display unit 20.

[0020] (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 will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Figure 1 is a schematic diagram showing the projection of a virtual image P using the image projection device 100 according to this embodiment. The solid line shown in Figure 1 indicates the path of the center position of the image light. As shown in Figure 1, the image projection device 100 includes an image irradiation unit 10, a mirror unit 30, a housing unit 40, a dustproof cover unit 50, a double ceiling unit 60, and an air layer 70. The image irradiation unit 10 also has an image display unit 20. Here, the mirror unit 30 corresponds to the projection optical unit in the present invention. As shown in Figure 1, the image light projected from the image projection device 100 is reflected by the windshield WS and irradiated onto the driver's viewpoint position E (eyebox). The driver views the virtual image P, which is formed at a predetermined distance (first distance) from the viewpoint position E, on the extension of the image light that has reached the viewpoint position E.

[0021] In the image projection device 100, each part is controlled by a control unit that is connected to each part for 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, an information communication device, etc. The control unit controls the operation of each part according to a predetermined program and sends information including an image (image information) to the image projection unit 10.

[0022] The image illumination unit 10 has an image display unit 20 and, based on image information from the control unit, illuminates the windshield WS with image light containing an image, and the image light reflected by the mirror unit 30 is then illuminated. The specific configuration of the image illumination unit 10 is not limited, but the image display unit 20 may be illuminated with backlight light from the light source unit 12, and the image displayed on the image display unit 20 may be illuminated as image light.

[0023] The image display unit 20 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 20, image light is emitted from the image display unit 20. The specific configuration of the image display unit 20 is not limited, and for example, a liquid crystal display device can be used.

[0024] The mirror section 30 is an optical element that reflects the image light arriving from the image illumination section 10 in the direction of the windshield WS. In the example shown in Figure 1, the mirror section 30 is a free-form concave mirror optically designed to project the image light as a virtual image P. The mirror section 30 projects the image light emitted from the image illumination section 10 onto the driver's viewpoint position E via the windshield WS, and images the image light at a first distance from the viewpoint position E, and therefore corresponds to the projection optical section in the present invention.

[0025] Figure 1 shows an example in which a mirror unit 30 is used as the projection optics unit, but the projection optics unit may also use multiple reflecting mirrors to fold and reflect the image light. Although not shown in Figure 1, the mirror unit 30 may have a variable relative angle to the windshield WS. The reflective surface of the mirror unit 30 is designed so that the optical diameter expands in the direction of the driver's viewpoint position E in order to project the image light as a virtual image P via the windshield WS. Here, expansion of the optical diameter in the viewpoint direction includes not only cases in which the optical diameter expands consistently after reflection, but also cases in which the optical diameter contracts, forms an image at an intermediate point, and then expands.

[0026] Furthermore, in Figure 1, the optical path of the image light is depicted as a single straight line. However, the actual image light is displayed in a predetermined area on the image display unit 20, and has a predetermined area in the direction perpendicular to the direction of propagation. In addition, the image light may travel while being reflected by multiple mirrors, reducing its optical diameter, and an intermediate image may be formed at an intermediate imaging position between the multiple mirrors.

[0027] The housing 40 constitutes the outer shape of the image projection device 100 and houses the other parts inside. An opening is provided at the top of the housing 40, and a dust cover 50 is provided at this opening to seal the interior. In Figure 1, the cross-sectional shape of the housing 40 is shown as a box shape with a flat bottom and top surface, but the shape of the housing 40 is not limited. The material constituting the housing 40 is not limited, and light-blocking resin materials or metal materials can be used.

[0028] The dust cover portion 50 is made of a material that transmits image light and is positioned to cover the opening of the housing portion 40. Although not shown in Figure 1, the dust cover portion 50 is fixed to the housing portion 40 in a way that there is no gap between them, preventing dust and dirt from entering the inside of the housing portion 40. The material that makes up the dust cover portion 50 is not limited, and known resin materials or glass that transmit image light can be used.

[0029] The double ceiling portion 60 is a plate-like portion provided to cover the upper part of the top surface of the housing portion 40. The position in which the double ceiling portion 60 is provided is preferably above the image irradiation unit 10, and more preferably above the image display unit 20. The air layer 70 is a layer formed by air entering between the double structure of the top surface of the housing portion 40 and the double ceiling portion 60. In Figure 1, the structure in which the air layer 70 is sandwiched between the double structure of the top surface of the housing portion 40 and the double ceiling portion 60 corresponds to the heat insulating layer in the present invention. In Figure 1, the structure in which the air layer 70 is sandwiched between the double structure of the top surface of the housing portion 40 and the double ceiling portion 60 is shown as the heat insulating layer, but the structure and material of the heat insulating layer are not limited as long as it has a lower thermal conductivity than the top surface of the housing portion 40. For example, known heat insulating materials such as glass wool or foamed resin may be attached to the upper or lower surface of the top surface of the housing portion 40.

[0030] The windshield WS is a visible light-transmitting part located in front of the driver's seat of the vehicle. The windshield WS reflects the image light incident from the image projection device 100 toward the viewpoint position E on the inner surface of the vehicle, and transmits light from outside the vehicle toward the viewpoint position E, 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 the light from the image projection device 100 may be reflected toward the viewpoint. Furthermore, it is not limited to being located in front of the vehicle, but may be placed to the side or rear as long as it projects an image toward the occupant's viewpoint.

[0031] The virtual image P is an image that appears to be formed in space when the image light reflected by the windshield WS reaches the occupant's viewpoint position E. The position where the virtual image P is formed is determined by the combined focal length of the projection optics unit included in the image projection device 100 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, speed and volume indicators, and direction of travel guides.

[0032] Figure 2 is a schematic diagram illustrating the thermal insulation effect of the image projection device 100. As shown in Figure 2, the image projection device 100 is located inside the vehicle's dashboard DB, and the dustproof cover portion 50 is exposed into the vehicle interior through a light emission port provided in the dashboard DB. External light, such as sunlight, enters the vehicle interior through the windshield WS, and the dashboard DB is heated by the external light irradiated in the area indicated by the ellipse in the figure, causing the temperature inside the dashboard DB to rise. The temperature inside the dashboard DB is also transmitted to the image projection device 100.

[0033] The wavy arrows shown in Figure 2 represent the magnitude of the heat transmitted within the dashboard DB, indicated by the thickness of the arrows. In this embodiment, the enclosure has a double structure with the top surface of the housing 40 and the double ceiling 60 as an insulating layer, and an air layer 70 is interposed between the image irradiation unit 10 and the dashboard DB. Because the air layer 70 has low thermal conductivity and a large insulating effect, the amount of heat transmitted through the air layer 70 is smaller than when heat is transmitted directly from the dashboard DB to the top surface of the housing 40. As a result, the amount of heat transmitted to the image irradiation unit 10 via the top surface of the housing 40 is reduced, and the temperature rise of the image display unit 20 can be suppressed.

[0034] Figure 3 is a schematic cross-sectional view illustrating the structure of the image illumination unit 10 according to this embodiment. As shown in Figure 3, the image illumination unit 10 of this embodiment includes a substrate 11, a light source 12, a heat sink 13, a housing 14, a lens 15, a low-absorption layer 16, and an image display unit 20.

[0035] 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.

[0036] The light source unit 12 is mounted on the substrate unit 11 and is a component that irradiates the image display unit 20 with backlight light via the lens unit 15. 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 two light source units 12 are mounted on the substrate unit 11, but the number and arrangement are not limited.

[0037] 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, but it is preferable that it is made of a material with a higher light absorption rate than the low absorption rate layer 16.

[0038] The housing portion 14 houses the substrate portion 11, the light source portion 12, and the lens portion 15, and also holds the image display portion 20. An opening is provided on the top surface of the housing portion 14, and the image display portion 20 is positioned in the opening. Backlight light emitted from the light source portion 12 reaches the image display portion 20 through the opening, and image light is emitted to the outside of the image illumination portion 10. The material constituting the outer layer of the housing portion 14 is not limited, but in order to suppress stray light arriving from outside the image illumination portion 10 from being diffusely reflected within the housing portion 40, it is preferable to use a material with a high light absorption rate, and as an example, a black-colored resin can be used.

[0039] 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 3 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 20.

[0040] The low-absorption layer 16 (inner layer) is provided on the inside of the housing portion 14 and is a layer made of a material with a lower light absorption rate than the housing portion 14 (outer layer). The material constituting the low-absorption layer 16 is not limited, but a white-colored resin material or the like can be used. By providing the low-absorption layer 16 on the inside of the housing portion 14, it is possible to suppress the absorption of stray light from the backlight emitted from the light source portion 12 by the housing portion 14. As a result, the temperature rise of the housing portion 14 due to light absorption and heat transfer to the image display portion 20 are suppressed, and the temperature rise of the image display portion 20 can be suppressed. In this embodiment, the low-absorption layer 16 has the function of suppressing heat transfer and temperature rise to the image display portion 20 and corresponds to the temperature rise suppression portion in the present invention.

[0041] The method for forming the two-layer structure of the housing portion 14 (outer layer) and the low absorption layer 16 (inner layer) is not limited, but it is preferable to use two-color molding technology for resin due to its high moldability and processing accuracy. Alternatively, the housing portion 14 may be applied after the low absorption layer 16 has been molded, or the low absorption layer 16 may be applied after the housing portion 14 has been molded. Furthermore, the housing portion 14 and the low absorption layer 16 may be constructed as separate parts and the two layers may be assembled by fitting or bonding.

[0042] Furthermore, the heat sink portion 13 is made of a material with a higher light absorption rate than the low absorption layer 16, and at least a portion of its surface is exposed inside the housing portion 14 around the substrate portion 11. Therefore, stray light reflected by the low absorption layer 16 is easily absorbed by the heat sink portion 13 and converted into heat. As described above, the heat sink portion 13 is made of a material with high thermal conductivity and is a component that dissipates heat from the back side, so the heat from the stray light absorbed by the heat sink portion 13 is efficiently dissipated and cooled from the back side. Therefore, even if stray light is absorbed by the heat sink portion 13, the amount of heat transmitted to the image display portion 20 is reduced, and the temperature rise of the image display portion 20 can be suppressed.

[0043] As described above, in the image projection apparatus 100 of the present embodiment, the housing portion 14 that holds the image display portion 20 is provided, and the housing portion 14 is provided with the low absorption rate layer 16 that suppresses heat transfer to the image display portion 20 as a temperature rise suppression portion, so that deterioration due to temperature rise of the image display portion 20 can be suppressed.

[0044] (Second Embodiment) Next, the second embodiment of the present invention will be described with reference to FIG. 4. Descriptions of the contents overlapping with the first embodiment will be omitted. FIG. 4 is a schematic cross-sectional view for explaining the structure of the image irradiation unit 10 according to the present embodiment. As shown in FIG. 4, the image irradiation unit 10 of the present embodiment includes a substrate portion 11, a light source portion 12, a heat sink portion 13, a housing portion 14, a lens portion 15, a heat radiation portion 17, and an image display portion 20.

[0045] The heat radiation portion 17 is provided at a position on the outer surface of the housing portion 14 that holds the image display portion 20, and is a member made of a material having a higher thermal conductivity than the inner surface of the housing portion 14. At least a part of the heat radiation portion 17 is exposed on the outer surface of the housing portion 14, and is in contact with the image display portion 20 at the exposed position. The material and structure constituting the heat radiation portion 17 are not limited, but as an example, a metal material such as a bus bar integrally formed with the housing portion 14 can be used. More specifically, it can be formed by using an insert molding technique or the like in which a metal plate such as a bus bar is processed into a shape covering the outer periphery of the housing portion 14, and the metal plate is placed in a mold and a resin material is injected. Also, after the housing portion 14 is molded, a method of printing a heating wire or the like on the outer peripheral surface of the housing portion 14 may be used.

[0046] Since the heat radiation portion 17 is in contact with the image display portion 20 on the outer peripheral surface of the housing portion 14, even if the backlight light or external light reaching the image display portion 20 is converted into heat, it is radiated from the image display portion 20 through the heat radiation portion 17, and the temperature rise of the image display portion 20 can be suppressed. In the present embodiment, the heat radiation portion 17 functions to suppress the temperature rise due to heat radiation from the image display portion 20, and corresponds to the temperature rise suppression portion in the present invention.

[0047] Even in the image projection device 100 of the present embodiment, it has a housing portion 14 that holds the image display portion 20, and the housing portion 14 includes a heat dissipation portion 17 that suppresses a temperature rise due to heat dissipation from the image display portion 20 as a temperature rise suppression portion, thereby suppressing deterioration due to a temperature rise of the image display portion 20.

[0048] (Third Embodiment) Next, the third embodiment of the present invention will be described with reference to FIG. 5. Descriptions of the contents overlapping with the first embodiment will be omitted. FIG. 5 is a schematic cross-sectional view for explaining the structure of the image irradiation unit 10 according to the present embodiment. As shown in FIG. 5, the image irradiation unit 10 of the present embodiment includes a substrate portion 11, a light source portion 12, a heat sink portion 13, a housing portion 14, a lens portion 15, a second lens portion 18, a partition portion 19, and an image display portion 20.

[0049] The second lens portion 18 is an optical member that is housed within the housing portion 14 and further refracts the backlight light that has passed through the lens portion 15 to irradiate the image display portion 20. Although the specific configuration of the second lens portion 18 is not limited, an example is adjusting the light distribution of the substantially parallel light irradiated from the lens portion 15 so that the backlight light is uniformly irradiated on the display area of the image display portion 20. FIG. 5 shows an example in which the second lens portion 18 is provided, but it is also possible to omit the second lens portion 18 and adjust the light distribution only with the lens portion 15.

[0050] The partition portion 19 is provided inside the housing portion 14 and is a portion that separates the space on the side where the light source portion 12 is provided from the space on the side where the image display portion 20 is provided. Also, the partition portion 19 is provided on the path until the backlight light irradiated from the light source portion 12 reaches the image display portion 20 and is composed of a light-transmissive material that transmits the backlight light. Here, separating the space by the partition portion 19 means separating it so that the inflow and outflow of air between the space provided on one surface side of the partition portion 19 and the space provided on the other surface side can be ignored. As an example, a structure in which the entire circumference of the inner surface of the housing portion 14 and the partition portion 19 are in contact is mentioned. Also, even if there is a small gap between the inner surface of the housing portion 14 and the partition portion 19, it may be considered that there is substantially no inflow and outflow of air through the gap.

[0051] Figure 5 shows an example in which the partition wall 19 is provided between the lens unit 15 and the second lens unit 18. However, it may also be provided between the lens unit 15 and the light source unit 12, or between the second lens unit 18 and the image display unit 20. Furthermore, the specific shape of the partition wall 19 is not limited, but in order to reduce its influence on the light distribution characteristics of the backlight, it is preferable to make it a plate shape with a uniform thickness. The thickness of the partition wall 19 is not limited, but as an example, it may be about 0.1 mm to 1 cm thick.

[0052] Furthermore, when a transmissive liquid crystal display device is used as the image display unit 20, the polarization direction transmitted through the image display unit 20 may be limited to one direction. In such cases, it is preferable to equip the partition wall 19 with a polarizing plate function to limit the polarization direction of the backlight light to the polarization direction used by the image display unit 20. This allows the partition wall 19 to cut off the polarization direction of the backlight light that reaches and is absorbed by the image display unit 20, thereby suppressing the temperature rise of the image display unit 20.

[0053] Furthermore, the light source 12 may emit backlight light containing wavelengths not used for image display in the image display unit 20, such as ultraviolet or infrared light. In such cases, it is preferable to equip the partition wall 19 with a wavelength cut filter function to limit the wavelength of the backlight light to the wavelengths used by the image display unit 20. This allows the partition wall 19 to cut off the wavelengths of backlight light that reach and are absorbed by the image display unit 20, thereby suppressing the temperature rise of the image display unit 20.

[0054] The partition wall 19 divides the space within the housing 14 into the light source 12 side and the image display unit 20 side. This prevents the heated air from reaching the image display unit 20 side, even if the air surrounding the light source 12 is heated by the heat generated by the light emission. Furthermore, since a heat sink 13 is provided on the back side of the substrate 11, the air on the light source 12 side of the partition wall 19 is efficiently cooled by heat dissipation from the heat sink 13. This suppresses the transfer of heat to the image display unit 20, thereby suppressing the temperature rise of the image display unit 20. In this embodiment, the partition wall 19 suppresses the transfer of heat from the light source 12 to the image display unit 20 and suppresses the temperature rise, corresponding to the temperature rise suppression unit in the present invention.

[0055] In this embodiment, instead of using the lens portion 15 or the second lens portion 18, a partition portion 19 is used to separate the space on the light source portion 12 side from the space on the image display portion 20 side. This minimizes the lens shape of the lens portion 15 and the second lens portion 18, thereby reducing the weight of the image illumination portion 10.

[0056] In this embodiment of the image projection device 100, there is a housing portion 14 that holds the image display portion 20, and a partition wall portion 19 that separates the space on the light source portion 12 side and the image display portion 20 side is provided inside the housing portion 14 as a temperature rise suppression portion, thereby suppressing deterioration of the image display portion 20 due to temperature rise.

[0057] (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to Figure 6. Details that overlap with the first embodiment will be omitted from the explanation. Figure 6 is a schematic diagram illustrating the temperature measurement of the image display unit 20 according to this embodiment. This embodiment differs from the first to third embodiments in that a mask unit 80 and a temperature measurement unit 81 are provided on the display surface side of the image display unit 20 to measure the temperature of the image display unit 20. Figure 6(a) shows the positional relationship between the image display unit 20, the mask unit 80, the temperature measurement unit 81 and the opening 82, and Figure 6(b) schematically shows the entire display area of ​​the image display unit 20.

[0058] The mask portion 80 is a plate-shaped member made of a light-blocking material and is positioned in contact with the display surface side of the image display unit 20. An opening 82 is formed in the mask portion 80, and a temperature measuring unit 81 is positioned near the opening 82. The material constituting the mask portion 80 is not limited, but it is preferable to use a metal material with high thermal conductivity in order to conduct heat from the image display unit 20 well. In addition, it is preferable that a light-absorbing layer is formed on both sides of the mask portion 80 in order to absorb stray light. As an example, a plate made of aluminum coated with a black resist can be used as the mask portion 80. Although not shown in Figure 6, a wiring pattern may be formed on the black resist to constitute a circuit for electrical connection with the temperature measuring unit 81.

[0059] The temperature measuring unit 81 is provided in contact with the mask unit 80 near the opening 82 and measures the temperature of the image display unit 20. The temperature measuring unit 81 is electrically connected to the control unit and sends temperature information to the control unit, which forms the basis for temperature control of the image display unit 20. Based on the temperature information from the temperature measuring unit 81, the control unit controls each part of the image projection device 100 so that the temperature of the image display unit 20 is below a certain temperature. The specific configuration of the temperature measuring unit 81 is not limited, but thermocouples, thermistors, etc., can be used.

[0060] The opening 82 is an opening formed in the mask portion 80 at a position facing the image display portion 20. The opening 82 is smaller than the entire display area of ​​the image display portion 20 and has a shape and area corresponding to the display area for displaying the projected image on the image display portion 20. Within the opening 82, image light can pass through the mask portion 80, but outside the opening 82, the mask portion 80 blocks the light.

[0061] In Figure 6(a), the area labeled 20 and shown by a dashed line represents the entire display area of ​​the image display unit 20. The area shown by a solid line, where the opening 82 is provided, is the display area for displaying images. Within the entire display area of ​​the image display unit 20, the area located between the solid and dashed lines in Figure 6(a) is an area other than the display area and is a non-display area. In Figure 6(a), an example is shown in which the temperature measuring unit 81 is located in a position corresponding to the non-display area, but the temperature measuring unit 81 may also be located outside the entire display area.

[0062] In this embodiment, since the temperature measurement unit 81 is provided in the mask unit 80, the accuracy and response characteristics of temperature measurement of the image display unit 20 can be improved. Furthermore, since the temperature measurement unit 81 is provided near the opening 82, the temperature of the display area of ​​the image display unit 20 can be measured efficiently.

[0063] 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.

[0064] This international application claims priority based on Japanese Patent Application No. 2024-168790, filed on 27 September 2024, and the entire contents of said Japanese Patent Application No. 2024-168790 are incorporated herein by reference.

[0065] The above description of specific embodiments of the present invention is provided for illustrative purposes only. It is not intended to be exhaustive or to limit the invention to the forms described. Numerous modifications and changes are possible in light of the above description, as will be obvious to those skilled in the art.

[0066] 100...Image projection device, 10...Image irradiation unit, 11...Substrate unit, 12...Light source unit, 13...Heat sink unit, 14...Housing unit, 15...Lens unit, 16...Low absorption layer, 17...Heat dissipation unit, 18...Second lens unit, 19...Partition wall unit, 20...Image display unit, 30...Mirror unit, 40...Housing unit, 50...Dustproof cover unit, 60...Double ceiling unit, 70...Air layer, 80...Mask unit, 81...Temperature measurement unit, 82...Opening.

Claims

1. An image projection device for projecting a projected 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 housing unit for housing the image illumination unit and the projection optical unit, wherein the image illumination unit comprises a light source unit for irradiating light, an image display unit for displaying an image, and a housing unit for housing the light source unit and holding the image display unit, and the housing unit comprises a temperature rise suppression unit for suppressing heat transfer to the image display unit.

2. An image projection apparatus according to claim 1, wherein the temperature rise suppression unit is composed of a two-layer structure consisting of an inner layer and an outer layer of the housing unit, and the inner layer is composed of a material with a lower light absorption rate than the outer layer.

3. An image projection apparatus according to claim 2, wherein the image irradiation unit has a heat sink unit that dissipates heat from the light source unit, and the heat sink unit is made of a material that has a higher light absorption rate than the inner layer on the inside of the housing unit.

4. An image projection apparatus according to claim 1, wherein the housing portion has a heat dissipation portion on at least a part of its outer surface that has a higher thermal conductivity than the inner surface, and the heat dissipation portion is in contact with the image display portion.

5. An image projection apparatus according to claim 4, characterized in that the heat dissipation section is made of a metal material and is integrally molded with the inner surface.

6. An image projection device according to claim 1, characterized in that a partition wall is provided inside the housing portion that separates the space in which the light source portion is provided from the space in which the image display portion is provided, and the partition wall portion is made of a light-transmitting material.

7. An image projection device according to claim 1, characterized in that the housing portion is provided with a heat insulating layer above the image display portion.

8. An image projection device according to claim 7, characterized in that the heat insulating layer is provided on the top surface of the housing and has a double structure with an air layer in between.

9. An image projection device according to any one of claims 1 to 8, wherein the image display unit is a display area in which part of the image is displayed, and the area other than the display area is a non-display area, and has a mask unit arranged on the display surface side of the image display unit and having an opening corresponding to the display area, and the mask unit is provided with a temperature measuring unit near the opening.

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