JP2023136360A - image projection device - Google Patents

Abstract

To provide an image projection device with which it is possible to effectively suppress the temperature rise of an image irradiation unit due to external light and secure visibility when using polarizing sunglasses or the like.SOLUTION: Provided is an image projection device (100) that projects a projection image to a display unit in order to display a virtual image. The image projection device (100) comprises an image irradiation unit (11) that irradiates image light, and an irradiation optical unit (20) that irradiates image light as a projection image in the viewpoint direction via the display unit. The irradiation optical unit (20) is provided with a polarization unit (16) that passes light in the prescribed polarization direction of image light through, the image light irradiated from the irradiation optical unit (20) including P-polarized light for the display unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image projection device, and more particularly to an image projection device that reflects irradiation light from an image irradiation unit to reach a viewpoint.

2. Description of the Related Art Conventionally, an instrument panel that displays illuminated icons has been used as a device for displaying various information in a vehicle. Additionally, as the amount of information to be displayed increases, 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.

However, since the instrument panel is located below the vehicle's windshield, in order for the driver to see the information displayed on the instrument panel, the driver must move his/her line of sight downwards while driving. Undesirable. Therefore, image projection devices such as a head-up display (HUD) have been proposed, which project an image onto the windshield so that the driver can read information when looking in front of the vehicle. .

FIG. 7 is a schematic diagram showing the configuration of a conventional image projection device. As shown in FIG. 7, the conventional image projection device includes an image irradiation section 1 and free-form mirrors 2 and 3. In such an image projection device, the image irradiation unit 1 emits irradiation light L1 containing an image, the free-form mirrors 2 and 3 reflect the irradiation light L1, and the image is projected in space through the windshield 4. It is made to reach the position of the viewpoint 5 of the driver or the like so that an image is formed. Thereby, the driver and the like can perceive that the image is displayed at the imaging position in the depth direction by the irradiation light L1 that has entered the viewpoint 5.

However, in the image projection device shown in FIG. 7, when sunlight or the like is incident from the outside as external light LO, the external light LO is focused onto the surface of the image irradiation unit 1 by the free-form mirrors 2 and 3. Therefore, there was a possibility that the temperature of the image irradiation section 1 would rise and the image irradiation section 1 would deteriorate. Therefore, the irradiation light L1 is intermediately imaged between the plurality of free-form mirrors 2 and 3, and a shielding part is placed near the intermediate imaging position to reduce the influence of external light LO reaching the image irradiation part from the outside. There are also proposals to reduce this. (For example, see Patent Document 1)

International Publication No. 2017/195740

However, in the structure using the light shielding part described in Patent Document 1, it is inevitable that outside light reaches the image irradiation part from the space for securing the optical path of the irradiation light, and it is necessary to restrict the incidence of outside light. had its limits.

Furthermore, when reflecting light at the windshield 4, there is a tendency that the reflectance of the P-polarized light component is low and the reflectance of the S-polarized light component is high. Therefore, the polarization direction of the irradiation light L1 irradiated from the image irradiation unit 1 is set to be S-polarized light with respect to the windshield 4. As a result, the irradiation light L1 that reaches the position of the viewpoint 5 becomes only S-polarized light that does not contain P-polarized light.

However, in an environment with strong external light LO or when driving on a snowy road, the passenger may wear polarized sunglasses and visually check the outside through the windshield 4. At this time, since the light reflected by objects outside the vehicle is also S-polarized light, the polarized sunglasses are set to cut the S-polarized light and transmit the P-polarized light. Therefore, for passengers wearing polarized sunglasses, the S-polarized light of the irradiated light L1 reflected by the windshield 4 is cut by the polarized sunglasses, making it difficult to visually recognize the image formed by the irradiated light L1. There was a problem.

The present invention has been made in view of the above-mentioned conventional problems, and has an object to effectively suppress the temperature rise of the image irradiation section due to external light, and to ensure visibility even when using polarized sunglasses or the like. The purpose of the present invention is to provide an image projection device capable of

In order to solve the above problems, an image projection apparatus of the present invention is an image projection apparatus that projects a projection image onto a display section for displaying a virtual image, and includes an image irradiation section that irradiates image light; an irradiation optical section that irradiates the image light as the projection image to a display section, the irradiation optical section includes a polarization section that transmits light in a predetermined polarization direction of the image light, and the irradiation optical section The image light irradiated from the display section includes P-polarized light directed toward the display section.

In such an image projection device of the present invention, the irradiation optical section includes a polarizing section, and in order to irradiate the display section with image light containing P-polarized light, a part of external light is cut by the polarizing section. It is possible to effectively suppress the temperature rise in the image irradiation section and to ensure visibility even when using polarized sunglasses or the like.

Further, in one aspect of the present invention, the irradiation optical section includes a retardation plate on the optical path of the image light.

Further, in one aspect of the present invention, the retardation plate is arranged closer to the display section than the polarizing section.

Further, in one aspect of the present invention, the polarizing section is arranged closer to the display section than the retardation plate.

Further, in one aspect of the present invention, the retardation plate is a quarter wavelength plate.

Further, in one aspect of the present invention, the image irradiation unit irradiates the display unit with the image light containing S-polarized light, and the retardation plate is a half-wave plate.

Further, in one aspect of the present invention, the image irradiation unit irradiates the display unit with the image light including P-polarized light, and the polarization unit transmits the P-polarized light.

Further, in one aspect of the present invention, the irradiation optical section includes a reflection section that reflects the image light irradiated from the image irradiation section, and the polarization section is disposed between the reflection section and the display section. has been done.

According to the present invention, it is possible to provide an image projection device that can effectively suppress the temperature rise of the image irradiation unit due to external light and ensure visibility even when using polarized sunglasses or the like.

FIG. 1 is a schematic diagram showing the configuration of an image projection device 100 according to a first embodiment. 7 is a graph schematically showing an example of reflection characteristics of P-polarized light and S-polarized light in the polarized light reflection adjustment unit 15. FIG. FIG. 2 is a schematic diagram showing the configuration of an image projection device 110 according to a second embodiment. FIG. 2 is a schematic diagram showing the configuration of an image projection device 120 according to a third embodiment. It is a schematic diagram showing the composition of image projection device 120 concerning a modification of a 3rd embodiment. It is a schematic diagram showing the composition of image projection device 130 concerning a 4th embodiment. FIG. 1 is a schematic diagram showing the configuration of a conventional image projection device.

(First embodiment)
Embodiments of the present invention will be described in detail below with reference to the drawings. Identical or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. FIG. 1 is a schematic diagram showing the configuration of an image projection apparatus 100 according to this embodiment.

As shown in FIG. 1, the image projection device 100 includes an image irradiation section 11, free-form mirrors 12 and 13, and a polarization section 16. The free-form mirrors 12 and 13 and the polarizing section 16 constitute an irradiation optical section 20 in the present invention. In FIG. 1, a typical optical path of the irradiation light L1 emitted from the image irradiation unit 11 is schematically shown by a solid line arrow, and a typical optical path of external light LO such as sunlight is shown by a broken line arrow. Further, a vehicle windshield 14 and a polarized reflection adjustment unit 15 are provided outside the image projection device 100, and a driver or the like can view an image using the irradiated light L1 from the viewpoint 5 via the polarized reflection adjustment unit 15. Visually recognize.

The image irradiation section 11 is a device that irradiates irradiation light (image light) L1 containing image information by being supplied with a signal containing image information from an information processing section (not shown). Irradiation light L1 irradiated from the image irradiation unit 11 enters the free-form surface mirror 12. Examples of the image irradiation unit 11 include a liquid crystal display device, an organic EL display device, a micro LED display device, a DMD (Digital Micro-mirror Device), a projector device using a laser light source, and the like. The irradiation light L1 irradiated from the image irradiation unit 11 is configured to include light that becomes P-polarized light with respect to the windshield 14, as indicated by the double-headed arrow in the figure. When the irradiation light L1 from the image irradiation unit 11 is polarized light in a specific direction, the orientation of the display surface of the image irradiation unit 11 is set so that the plane of polarization becomes P-polarized light with respect to the windshield 14. Examples of the image irradiation unit 11 that irradiates the irradiation light L1 with a specific polarization include a liquid crystal display device, a projector device using a laser light source, a reflective liquid crystal projector device, and the like.

The free-form surface mirror 12 is a mirror on which the irradiation light L1 emitted from the image irradiation unit 11 is incident and reflected in the free-form surface mirror 13 direction. The reflection surface shape of the free-form surface mirror 12 is composed of a free-form surface whose curvature is not constant but changes two-dimensionally. Although FIG. 1 shows a convex mirror as the shape of the free-form mirror 12, a concave mirror or a plane mirror may be used.

The free-form mirror 13 is a concave mirror into which the irradiation light L1 reflected by the free-form mirror 12 is incident and reflected in the direction of the windshield 14 via the polarizing section 16. The reflection surface shape of the free-form surface mirror 13 is composed of a free-form surface whose curvature is not constant but changes two-dimensionally. Although FIG. 1 shows a concave mirror as the shape of the free-form mirror 13, a convex mirror or a plane mirror may be used. The free-form mirrors 12 and 13 correspond to a reflecting section in the present invention.

The polarizing section 16 is an optical member having an optical property of transmitting polarized light in the transmission axis direction and blocking polarized light perpendicular to the transmission axis direction, and can use a known polarizing plate or polarizing film. Further, the polarizing section 16 is arranged between the free-form mirror 13 and the windshield 14. Although FIG. 1 shows an example in which the polarizing section 16 is arranged between the free-form mirror 13 and the windshield 14, the position of the polarizing section 16 is on the optical path of the irradiated light L1 from the polarized reflection adjustment section 15 to the windshield 14. If so, there are no limitations. Further, the transmission axis of the polarizing section 16 is arranged so as to transmit P-polarized light to the windshield 14.

The windshield 14 is provided in front of the driver's seat of the vehicle, and transmits light from outside the vehicle in the direction of the viewpoint 5. In addition, since the windshield 14 transmits at least visible light among the light from outside the vehicle, even when external light LO such as sunlight enters the interior of the vehicle from above, the In addition, the external light LO reaches the polarizing section 16 and the free-form mirror 13. Further, a polarized light reflection adjustment section 15 is provided on the inner surface of the windshield 14.

The polarization reflection adjustment unit 15 is an optical member provided on the inner surface of the windshield 14, and has an optical property of reflecting the S-polarized light component and the P-polarized light component of the incident light to the same extent. Further, the polarized light reflection adjustment unit 15 has an optical characteristic in which the reflectance changes depending on the angle of incidence, which is an angle of incidence from the direction perpendicular to the plane of incidence. Further, it is preferable that the saturation of the polarized light reflection adjustment section 15 is 20 or less. When the saturation satisfies this condition, the color of the irradiated light L1 is not deteriorated, and deterioration in the quality of the projected virtual image can be suppressed. In the example shown in FIG. 1, the polarized light reflection adjusting section 15 is configured as a substantially flat film shape, and is attached along the curvature of the inner surface of the windshield 14. Although FIG. 1 shows an example in which the polarization reflection adjustment unit 15 is provided in a part of the windshield 14, it may be attached to the front surface of the windshield 14.

FIG. 2 is a graph schematically showing an example of the reflection characteristics of P-polarized light and S-polarized light in the polarized light reflection adjustment section 15. The horizontal axis of the graph indicates a direction perpendicular to the surface of the polarized light reflection adjustment unit 15 as 0 degrees, and an angle inclined from 0 degrees as an incident angle. In addition, the vertical axis of the graph indicates the reflectance of polarized light (P-polarized light) in the in-plane direction including the 0 degree direction of the polarized light reflection adjustment unit 15 and the incident direction of light, and the reflectance of S-polarized light perpendicular to the P-polarized light. ing. As shown in FIG. 2, the polarization reflection adjustment unit 15 has a low reflectance (high transmittance) for light that is incident near the vertical direction with a small incident angle, and the reflectance increases as the incident angle increases. (the transmittance decreases), and the reflectance increases above a predetermined angle of incidence. Further, as shown in FIG. 2, the polarized light reflection adjustment unit 15 has a reflectance of the P polarized light and the S polarized light at approximately the same level in the incident angle range of 20 to 40 degrees.

As the polarized reflection adjustment unit 15 having the optical characteristics shown in FIG. 2, there is a laminated film manufactured by Toray Industries, Inc. (product name "PICASUS (registered trademark) VT"), a film described in Japanese Patent Application Publication No. 2021-54061, etc. A laminated film can be used. Although the example shown in FIG. 2 shows an example in which the reflectance approaches the maximum value when the incident angle is around 40 degrees, the maximum value of the reflectance and the incident angle at which the maximum value is reached are not limited to this.

In addition, although FIG. 1 shows an example in which the polarized reflection adjustment unit 15 is attached to the windshield 14 as a display unit, a combiner is prepared as a display unit separately from the windshield 14, and the polarized reflection adjustment unit is attached to the inner surface of the combiner. 15 may be attached to reflect the light from the free-form mirror 13 in the direction of the viewpoint. Furthermore, the display unit is not limited to being located at the front of the vehicle, but may be placed at the side or rear as long as it projects an image to the passenger's viewpoint 5. Viewpoint 5 is the eye (eye box) of the driver or passenger of the vehicle, and when the irradiation light L1 enters the eye box and reaches the retina, the driver or passenger can see the formed virtual image. visually confirm.

The virtual image is displayed as if it were formed in space when the irradiation light L1 reflected by the polarization reflection adjustment unit 15 reaches the viewpoint (eye box) 5 of the driver or the like. The position where the virtual image is formed is determined by the spread angle when the light emitted from the image irradiation unit 11 travels toward the viewpoint after being reflected by the free-form mirrors 12 and 13 and the polarization reflection adjustment unit 15. At this time, the driver or passenger recognizes that the virtual image exists at an imaging position farther from the windshield 14. Here, the imaging position of the virtual image mainly depends on the combined focal length of the free-form surface mirror 12 and the free-form surface mirror 13. Even if the windshield 14 is not a flat surface but a curved surface, the radius of curvature is larger than that of the free-form mirror 12 and the free-form mirror 13, so the influence of the optical power by the windshield 14 is negligible. .

As shown in FIG. 1, the irradiation light L1 from the image irradiation unit 11 includes P polarization toward the windshield 14, and the irradiation light L1 reflected by the free-form mirrors 12 and 13 also includes P polarization. Further, since the polarizing section 16 is arranged to transmit the P-polarized light to the windshield 14, the irradiation light L1 passes through the polarizing section 16 and reaches the polarized light reflection adjusting section 15. As shown in FIG. 2, the polarization reflection adjustment unit 15 has the same reflectance for S-polarized light and P-polarized light, so the P-polarized light component of the irradiated light L1 is also well reflected and reaches the viewpoint 5. Therefore, the virtual image is projected using P-polarized light, and can be clearly seen even when the passenger is wearing polarized sunglasses. Here, as shown in FIG. 2, the polarization reflection adjustment unit 15 has a small reflectance difference between S polarization and P polarization when the incident angle is in the range of 20 to 40 degrees. It is preferable to set the angle to 20 to 40 degrees.

Further, as shown in FIG. 1, external light LO such as sunlight enters from above the windshield 14, and a part of it passes through the polarization reflection adjustment section 15 and the polarization section 16, and is connected to the free-form mirror 13 and the free-form surface mirror 13. The light is reflected by the curved mirror 12 and reaches the image irradiation unit 11 . Here, although the external light LO incident from the outside of the vehicle is unpolarized light that includes components in all polarization directions, only the P-polarized light component can pass through the polarizing section 16 with respect to the windshield 14 . Therefore, the S-polarized component of the external light LO is cut by the polarizer 16, and the amount of light reaching the image irradiator 11 can be suppressed. Thereby, it is possible to suppress the temperature rise due to the external light LO reaching the image irradiation unit 11 and prevent deterioration.

As described above, in the image projection device 100 of the present embodiment, the irradiation optical section 20 includes the polarizing section 16 and projects the irradiation light L1 containing P-polarized light onto the display section, so that part of the external light LO is By cutting the portion with the polarizing portion 16, it is possible to effectively suppress the temperature rise of the image irradiation portion 11, and to ensure visibility even when using polarized sunglasses or the like.

(Second embodiment)
Next, a second embodiment of the present invention will be described using FIG. 3. Description of contents that overlap with those of the first embodiment will be omitted. FIG. 3 is a schematic diagram showing the configuration of the image projection device 110 according to this embodiment. As shown in FIG. 3, the image projection device 110 includes an image irradiation section 11, free-form mirrors 12 and 13, a polarization section 16, and a quarter-wave plate 17. The free-form mirrors 12 and 13, the polarizing section 16, and the quarter-wave plate 17 constitute the irradiation optical section 20 in the present invention.

The quarter-wave plate 17 is an optical member that is placed on the optical path of the irradiation light (image light) L1 and generates a phase difference by a quarter wavelength in the fast axis and slow axis that are orthogonal to each other. This corresponds to the retardation plate in the invention. The quarter-wave plate 17 is preferably arranged closer to the display section than the polarizing section 16, and in the example shown in FIG. Further, the fast axis of the quarter-wave plate 17 is arranged to be different from the S-polarized light component and the P-polarized light component of the irradiated light L1 by 45 degrees, respectively.

As shown in FIG. 3, in the image projection device 110 of this embodiment, the irradiation light L1 from the image irradiation unit 11 includes S-polarized light directed toward the windshield 14, and the irradiation light L1 is reflected by the free-form mirrors 12 and 13. The light L1 also includes S-polarized light. Furthermore, since the polarizing section 16 is arranged to transmit the S-polarized light to the windshield 14, the irradiated light L1 passes through the polarizing section 16, and after passing through the quarter-wave plate 17, the polarized light reflection adjusting section Reach up to 15. In the quarter-wave plate 17, the polarization direction of the S-polarized light differs from the fast axis by 45 degrees, so the irradiation light L1 transmitted through the quarter-wave plate 17 becomes circularly polarized light C. The circularly polarized light C is light in which the P polarized light component and the S polarized light component are shifted by a quarter wavelength, and includes P polarized light.

As shown in FIG. 2, the polarization reflection adjustment unit 15 has the same reflectance for S-polarized light and P-polarized light, so that both the P-polarized light component and the S-polarized light component of the irradiated light L1 of the circularly polarized light C are well reflected. and reach viewpoint 5. Therefore, the virtual image is projected by the circularly polarized light C. At this time, the irradiated light L1 is irradiated with S-polarized light and the polarizing section 16 transmits the S-polarized light, so even if the irradiated light L1 passes through the polarizing section 16 and the quarter-wave plate 17, a specific polarized component is not cut. It never happens. Here, since the polarized sunglasses transmit the circularly polarized light C, the virtual image can be clearly viewed even when the passenger is wearing the polarized sunglasses.

Further, as shown in FIG. 3, external light LO such as sunlight enters from above the windshield 14, and a portion of it passes through the polarization reflection adjustment section 15, the quarter-wave plate 17, and the polarization section 16. Then, it is reflected by the free-form surface mirror 13 and the free-form surface mirror 12 and reaches the image irradiation section 11 . Here, the external light LO incident from the outside of the vehicle is unpolarized light that includes components in all polarization directions, and remains unpolarized light even if it passes through the quarter-wave plate 17. Further, the polarizing section 16 allows only the S-polarized light component to pass through the windshield 14 . Therefore, the P-polarized component of the external light LO is cut by the polarizer 16, and the amount of light reaching the image irradiator 11 can be suppressed. Thereby, it is possible to suppress the temperature rise due to the external light LO reaching the image irradiation unit 11 and prevent deterioration.

In FIG. 3, an example is shown in which the S-polarized irradiation light L1 is emitted from the image irradiation unit 11 and the S-polarized light is transmitted through the polarization unit 16. The polarization direction is not limited as long as it can be converted to C. As an example, even if P-polarized irradiation light L1 is emitted from the image irradiation unit 11 and the P-polarized light is transmitted through the polarization unit 16, the irradiation light L1 passes through the quarter-wave plate 17 and becomes circularly polarized light C. , the virtual image can be clearly recognized even through polarized sunglasses.

As described above, in the image projection device 110 of this embodiment, the irradiation optical section 20 includes the polarizing section 16 and the quarter-wave plate 17, and irradiates the display section with circularly polarized light C containing P-polarized light. Project the light L1. This makes it possible to cut part of the external light LO with the polarizing section 16 to effectively suppress the temperature rise of the image irradiating section 11, and to ensure visibility even when using polarized sunglasses or the like. Become.

(Third embodiment)
Next, a third embodiment of the present invention will be described using FIG. 4. Description of contents that overlap with those of the first embodiment will be omitted. FIG. 4 is a schematic diagram showing the configuration of the image projection device 120 according to this embodiment. As shown in FIG. 4, the image projection device 120 includes an image irradiation section 11, free-form mirrors 12 and 13, a polarization section 16, and a half-wave plate 18. The free-form mirrors 12 and 13, the polarizing section 16, and the half-wave plate 18 constitute the irradiation optical section 20 in the present invention.

The half-wave plate 18 is an optical member that is disposed on the optical path of the irradiation light (image light) L1 and generates a phase difference by a half wavelength in a fast axis and a slow axis that are orthogonal to each other. It corresponds to a retardation plate. The half-wave plate 18 is preferably arranged closer to the display section than the polarizing section 16, and in the example shown in FIG. 4, it is arranged between the polarizing section 16 and the polarization reflection adjusting section 15. Further, the fast axis of the half-wave plate 18 is arranged to be different from the S-polarized light component and the P-polarized light component of the irradiation light L1 by 45 degrees, respectively.

As shown in FIG. 4, in the image projection device 120 of this embodiment, the irradiation light L1 from the image irradiation unit 11 includes S-polarized light directed toward the windshield 14, and the irradiation light L1 is reflected by the free-form mirrors 12 and 13. The light L1 also includes S-polarized light. Furthermore, since the polarizing section 16 is arranged to transmit the S-polarized light to the windshield 14, the irradiation light L1 passes through the polarizing section 16, and after passing through the half-wave plate 18, the polarized light reflection adjustment section 15 reach up to. In the half-wave plate 18, the polarization direction of the S-polarized light differs from the fast axis by 45 degrees, so the irradiation light L1 transmitted through the half-wave plate 18 becomes P-polarized light.

As shown in FIG. 2, the polarization reflection adjustment unit 15 has the same reflectance for S-polarized light and P-polarized light, so the P-polarized light component of the irradiated light L1 is well reflected and reaches the viewpoint 5. Therefore, the virtual image is projected by P-polarized light. Here, since polarized sunglasses transmit P-polarized light, even when the passenger is wearing polarized sunglasses, it is possible to visually recognize the virtual image well.

Further, as shown in FIG. 4, external light LO such as sunlight enters from above the windshield 14, and a portion of it passes through the polarization reflection adjustment section 15, the half-wave plate 18, and the polarization section 16. , is reflected by the free-form surface mirror 13 and the free-form surface mirror 12, and reaches the image irradiation section 11. Here, the external light LO incident from outside the vehicle is unpolarized light containing components in all polarization directions, and remains unpolarized even if it passes through the half-wave plate 18. Further, the polarizing section 16 allows only the S-polarized light component to pass through the windshield 14 . Therefore, the P-polarized component of the external light LO is cut by the polarizer 16, and the amount of light reaching the image irradiator 11 can be suppressed. Thereby, it is possible to suppress the temperature rise due to the external light LO reaching the image irradiation unit 11 and prevent deterioration.

As described above, in the image projection device 120 of this embodiment, the irradiation optical section 20 includes the polarizing section 16 and the half-wave plate 18, and projects the P-polarized irradiation light L1 onto the display section. This makes it possible to cut part of the external light LO with the polarizing section 16 to effectively suppress the temperature rise of the image irradiating section 11, and to ensure visibility even when using polarized sunglasses or the like. Become.

(Modification of third embodiment)
Next, a modification of the third embodiment of the present invention will be described using FIG. 5. FIG. 5 is a schematic diagram showing the configuration of an image projection device 120 according to this modification. In this modification, the half-wave plate 18 is arranged between the polarizing section 16 and the free-form mirror 13, and the third point is that the polarizing section 16 is arranged so as to transmit P-polarized light to the windshield 14. It is different from the embodiment.

As shown in FIG. 5, in the image projection device 120 of this embodiment, the irradiation light L1 from the image irradiation unit 11 includes S-polarized light directed toward the windshield 14, and the irradiation light L1 is reflected by the free-form mirrors 12 and 13. The light L1 also includes S-polarized light. In the half-wave plate 18, the polarization direction of the S-polarized light differs from the fast axis by 45 degrees, so the irradiation light L1 transmitted through the half-wave plate 18 becomes P-polarized light. Since the polarizing section 16 is arranged to transmit the P-polarized light to the windshield 14, the irradiation light L1 reaches the polarized light reflection adjusting section 15 after passing through the polarizing section 16.

As shown in FIG. 2, the polarization reflection adjustment unit 15 has the same reflectance for S-polarized light and P-polarized light, so the P-polarized light component of the irradiated light L1 is well reflected and reaches the viewpoint 5. Therefore, the virtual image is projected by P-polarized light. Here, since polarized sunglasses transmit P-polarized light, even when the passenger is wearing polarized sunglasses, it is possible to visually recognize the virtual image well.

Further, as shown in FIG. 5, external light LO such as sunlight enters from above the windshield 14, and a portion of it passes through the polarization reflection adjustment section 15, the polarization section 16, and the half-wave plate 18. , is reflected by the free-form surface mirror 13 and the free-form surface mirror 12, and reaches the image irradiation section 11. Here, the polarizing section 16 allows only the P-polarized light component to pass through the windshield 14. Therefore, the S-polarized component of the external light LO is cut by the polarizer 16, and the amount of light reaching the image irradiator 11 can be suppressed. Here, the P-polarized light that has passed through the polarizing section 16 passes through the half-wave plate 18 and is converted into S-polarized light, but the amount of light does not change significantly. Thereby, it is possible to suppress the temperature rise due to the external light LO reaching the image irradiation unit 11 and prevent deterioration.

As described above, also in the image projection device 120 of this modification, the irradiation optical section 20 includes the half-wave plate 18 and the polarizing section 16, and projects the P-polarized irradiation light L1 onto the display section. This makes it possible to cut part of the external light LO with the polarizing section 16 to effectively suppress the temperature rise of the image irradiating section 11, and to ensure visibility even when using polarized sunglasses or the like. Become.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described using FIG. 6. Description of contents that overlap with those of the first embodiment will be omitted. FIG. 6 is a schematic diagram showing the configuration of the image projection device 130 according to this embodiment. As shown in FIG. 6, the image projection device 130 includes an image irradiation section 11, free-form mirrors 12 and 13, a polarization section 16, and a retardation plate 19. The free-form mirrors 12 and 13, the polarizing section 16, and the retardation plate 19 constitute an irradiation optical section 20 in the present invention.

The retardation plate 19 is an optical member that is disposed on the optical path of the irradiation light (image light) L1 and generates a phase difference between a fast axis and a slow axis that are orthogonal to each other. The retardation plate 19 is preferably arranged closer to the display section than the polarizing section 16, and in the example shown in FIG. Furthermore, it is preferable that the fast axis of the retardation plate 19 be arranged to differ by 45 degrees from the S-polarized component and the P-polarized component of the irradiation light L1, but the angle is not limited.

As shown in FIG. 6, in the image projection device 130 of this embodiment, the irradiation light L1 from the image irradiation unit 11 includes S-polarized light directed toward the windshield 14, and the irradiation light L1 is reflected by the free-form mirrors 12 and 13. The light L1 also includes S-polarized light. Furthermore, since the polarizing section 16 is arranged to transmit the S-polarized light to the windshield 14, the irradiated light L1 passes through the polarizing section 16, passes through the retardation plate 19, and then reaches the polarized light reflection adjustment section 15. reach. In the retardation plate 19, the polarization direction of the S-polarized light is different from the fast axis, so the irradiation light L1 transmitted through the retardation plate 19 becomes elliptically polarized light E. The elliptically polarized light E is light in which the P-polarized light component and the S-polarized light component are out of phase, and includes the P-polarized light.

As shown in FIG. 2, the polarization reflection adjustment unit 15 has the same reflectance for S-polarized light and P-polarized light, so that both the P-polarized light component and the S-polarized light component of the elliptically polarized light E are well reflected. and reach viewpoint 5. Therefore, the virtual image is projected by the elliptically polarized light E. Here, since the polarized sunglasses transmit the elliptically polarized light E, even when the passenger is wearing the polarized sunglasses, the virtual image can be clearly viewed.

Further, as shown in FIG. 6, external light LO such as sunlight enters from above the windshield 14, and a part of it passes through the polarization reflection adjustment section 15, the retardation plate 19, and the polarization section 16, and is freely transmitted. The light is reflected by the curved mirror 13 and the free-form mirror 12 and reaches the image irradiation unit 11 . Here, the external light LO incident from the outside of the vehicle is unpolarized light containing components in all polarization directions, and remains unpolarized even if it passes through the retardation plate 19. Further, the polarizing section 16 allows only the S-polarized light component to pass through the windshield 14 . Therefore, the P-polarized component of the external light LO is cut by the polarizer 16, and the amount of light reaching the image irradiator 11 can be suppressed. Thereby, it is possible to suppress the temperature rise due to the external light LO reaching the image irradiation unit 11 and prevent deterioration.

In FIG. 6, an example is shown in which the S-polarized irradiation light L1 is emitted from the image irradiation unit 11 and the S-polarized light is transmitted through the polarization unit 16, but the polarization of the irradiation light L1 is converted into elliptically polarized light E by the retardation plate 19. The polarization direction is not limited as long as it can be used. For example, even if P-polarized light L1 is emitted from the image irradiation unit 11 and the P-polarized light is transmitted through the polarizing unit 16, the emitted light L1 passes through the retardation plate 19 and becomes elliptically polarized light E, and polarized sunglasses The virtual image can be clearly recognized even through the .

As described above, in the image projection device 130 of the present embodiment, the irradiation optical section 20 includes the polarizing section 16 and the retardation plate 19, and emits the irradiation light L1 as elliptically polarized light E including P-polarized light to the display section. Project. This makes it possible to cut part of the external light LO with the polarizing section 16 to effectively suppress the temperature rise of the image irradiating section 11, and to ensure visibility even when using polarized sunglasses or the like. Become.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. In the first to fourth embodiments, the optical characteristics of the polarization reflection adjustment section 15 are such that the S-polarized light component and the P-polarized light component of the incident light are reflected to the same extent. However, it is also possible to use the polarization reflection adjustment section 15 having optical characteristics that reflect the P-polarized light component with a higher reflectance than the S-polarized light component.

In the examples shown in FIGS. 1, 4, and 5, the irradiation light irradiated onto the windshield 14 from the image projection device is P-polarized light. Further, in the example shown in FIG. 6, elliptically polarized light is used as the irradiation light, and the elliptically polarized light can be such that the P polarized light component is larger than the S polarized light component. Therefore, even if the polarization reflection adjustment unit 15 that reflects the P-polarized light component with a higher reflectance than the S-polarized light component is used, it is possible to project an image with the P-polarized light component with a high reflectance, and it is possible to project an image using the P-polarized light component with a high reflectance. It is possible to ensure visibility even in the case of

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

100, 110, 120, 130...Image projection device 11...Image irradiation section 12, 13...Free-form mirror 14...Windshield 15...Polarized light reflection adjustment section 16...Polarizing section 17...Quarter wavelength plate 18...Half Wave plate 19... Retardation plate 20... Irradiation optical section

Claims (8)

An image projection device that projects a projection image onto a display unit for displaying a virtual image,
an image irradiation unit that irradiates image light;
an irradiation optical section that irradiates the image light as the projected image to the display section,
The irradiation optical section includes a polarizing section that transmits light in a predetermined polarization direction of the image light,
An image projection device characterized in that the image light irradiated from the irradiation optical section includes P-polarized light directed toward the display section. The image projection device according to claim 1,
The image projection device is characterized in that the irradiation optical section includes a retardation plate on the optical path of the image light. The image projection device according to claim 2,
The image projection device is characterized in that the retardation plate is disposed closer to the display unit than the polarizing unit. The image projection device according to claim 2,
The image projection device is characterized in that the polarizing section is arranged closer to the display section than the retardation plate. The image projection device according to any one of claims 2 to 4,
An image projection device characterized in that the retardation plate is a quarter wavelength plate. The image projection device according to any one of claims 2 to 4,
The image irradiation unit irradiates the image light containing S-polarized light to the display unit,
An image projection device characterized in that the retardation plate is a half-wave plate. The image projection device according to claim 1,
The image irradiation unit irradiates the image light including P-polarized light to the display unit,
The image projection device is characterized in that the polarizing section transmits the P-polarized light. The image projection device according to any one of claims 1 to 7,
The irradiation optical section includes a reflection section that reflects the image light irradiated from the image irradiation section,
The image projection device is characterized in that the polarizing section is disposed between the reflecting section and the display section.

Images