JP2023149978A - image projection device - Google Patents

Abstract

To provide an image projection device with which it is possible to cut back the number of components while suppressing a rise of the temperature of an image irradiation unit due to external light.SOLUTION: Provided is an image projection device (100) comprising: an image irradiation unit (10) that radiates irradiation light having image information, a first mirror (21) that reflects irradiation light having entered from the image irradiation unit (10), and a second free-form surface mirror (22) that reflects irradiation light having entered from the first mirror (21) so as to reach a viewpoint (40). The first mirror (21) has a curvature in one axial direction and is flat in the other axis direction that is orthogonal to the one axis direction, with a polarization filter unit provided on the reflection surface of the mirror (21) that reflects polarized light in one direction and cuts polarized light in the other direction that is orthogonal to the one direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image projection device, and more particularly to an image projection device that projects a projected image onto a display unit for displaying a virtual image.

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. Therefore, it is undesirable. Therefore, a head-up display (hereinafter referred to as HUD) that projects an image onto the windshield so that the driver can read information when visually checking the front of the vehicle has also been proposed (for example, Patent Document 1 , 2).

JP2019-119248A JP 2019-119262 Publication

Such a conventional HUD device is equipped with a projection optical system that irradiates light from below to above the windshield in order to irradiate a projected image through the windshield that is the display section. Therefore, when external light such as sunlight enters from above the windshield, the external light reaches the image irradiation unit that displays the image via the projection optical system. At this time, there is a problem in that the external light that reaches the image irradiation unit via the projection optical system is condensed by the optical power of the projection optical system, causing deterioration due to temperature rise.

In order to suppress such a temperature rise, it has also been proposed to arrange a wavelength cut filter on the optical path of the projection optical system to cut out infrared light and ultraviolet light contained in external light. However, it is unavoidable that visible light contained in external light passes through the wavelength cut filter and reaches the display, and since the light transmittance of the wavelength cut filter is not 100%, the light irradiated from the display is also uniform. There is also the possibility that some parts of the light will be attenuated, causing a decrease in brightness in image projection.

Therefore, we are also considering placing a polarizing plate on the optical path that transmits only polarized light in a predetermined direction, allowing the polarization direction of the light irradiated from the image irradiation unit to pass through, and cutting out the polarized light that is orthogonal to the predetermined direction out of the external light. has been done. However, there is a problem in that a member for holding the polarizing plate on the optical path is required, resulting in an increase in the number of parts.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an image projection device that can reduce the number of parts while suppressing the temperature rise of the image irradiation section due to external light. purpose.

In order to solve the above problems, an image projection device of the present invention includes: an image irradiation section that irradiates irradiation light having image information; a first mirror that reflects the irradiation light that has entered from the image irradiation section; a second free-form surface mirror that reflects the irradiation light incident from the first mirror to reach the viewpoint, and the first mirror has a curvature in one axis direction and is flat in the other axis direction perpendicular to the one axis direction. The first mirror includes a polarizing filter section on the reflective surface of the first mirror that reflects polarized light in one direction and cuts polarized light in the other direction orthogonal to the one direction.

In such an image projection device of the present invention, since the first mirror has a curvature in one axis direction and is flat in the other axis direction, a polarizing filter section is provided on the reflective surface of the first mirror, so that the image produced by external light is It is possible to reduce the number of parts while suppressing the temperature rise of the irradiation section.

Further, in one aspect of the present invention, the polarizing filter section is configured by pasting a polarizing plate along the surface of the reflective surface with an adhesive layer.

Further, in one aspect of the present invention, the reference ray of the irradiation light from the image irradiation unit to the second free-form surface mirror constitutes the same traveling plane, and the uniaxial direction is included in the traveling plane.

Further, in one aspect of the present invention, the one direction of the polarizing filter portion coincides with the one axis direction or the other axis direction of the first mirror.

Moreover, in one aspect of the present invention, the irradiation light reflected by the second free-form surface mirror is intermediately imaged in the one-axis direction and/or the other-axis direction on the optical path to the viewpoint.

Further, in one aspect of the present invention, a third free-form surface mirror is provided that reflects the irradiation light incident from the second free-form surface mirror to reach a viewpoint.

According to the present invention, it is possible to provide an image projection device that can reduce the number of parts while suppressing the temperature rise of the image irradiation unit due to external light.

FIG. 1 is a schematic diagram showing the configuration of an image projection device 100 and the position of a formed virtual image according to the first embodiment. FIG. 2 is a schematic diagram showing the structure of the first mirror 21 in the first embodiment, with FIG. 2(a) showing a schematic perspective view and FIG. 2(b) showing a schematic cross-sectional view. FIG. 7 is a schematic perspective view showing the structure of a first mirror 21 in a second embodiment. FIG. 7 is a schematic diagram showing the configuration of an image projection device 110 and the position of a formed virtual image according to a third embodiment.

(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 and the position of a virtual image formed.

As shown in FIG. 1, the image projection device 100 includes an image irradiation section 10, a first mirror 21, and free-form mirrors 22 and 23. Here, a combination of the first mirror 21, the free-form surface mirror 22, and the free-form surface mirror 23 constitutes the irradiation optical section 20 in the present invention. Moreover, the free-form surface mirrors 22 and 23 correspond to a second free-form surface mirror and a third free-form surface mirror in the present invention, respectively. The light projected from the image projection device 100 is irradiated onto the driver's viewpoint 40 through the windshield 30 (display section), and a virtual image 50 is formed at a predetermined distance from the windshield 30.

The image projection apparatus 100 also includes a control unit (not shown) that is connected to each unit for information communication and controls each unit. Although the configuration of the control unit is not limited, one example includes a CPU (Central Processing Unit) for performing information processing, a memory device, a recording medium, an information communication device, and the like. The control section controls the operation of each section according to a predetermined program, and sends information including an image (image information) to the image irradiation section 10.

The image irradiation section 10 is a section that irradiates irradiation light having image information based on image information from the control section. The specific configuration of the image irradiation section 10 is not limited, and conventionally known devices such as a liquid crystal display device, an organic EL display device, a combination of a laser light source and a light modulation element, etc. can be used. In the example shown in FIG. 1, a light emitting diode (LED) is used to irradiate light from the back side of the liquid crystal display device. The image irradiation unit 10 may be configured to include a near display area and a far display area that display near images and far images, respectively. The far image displayed in the far display area is irradiated with the first image light, and the near image displayed in the near display area is irradiated with the second image light.

The first mirror 21 is an optical member into which the irradiation light emitted from the image irradiation unit 10 is incident and reflects the irradiation light in the direction of the free-form mirror 22 . Although details of the first mirror 21 will be described later, it has a curvature in a predetermined direction (one axial direction) and a flat reflective surface in a direction perpendicular to the predetermined direction (another axial direction). Further, on the reflective surface of the first mirror 21, there is provided a polarizing filter section that reflects polarized light in one direction and cuts polarized light in the other direction orthogonal to the one direction. Here, cutting the polarized light in the other direction means that the reflectance of the polarized light in the other direction is low, and the polarized light in the other direction is transmitted or absorbed. Further, the polarized light transmitted through the polarizing filter section is absorbed by the surface of the first mirror 21, etc., and the reflectance of the entire combination of the first mirror 21 and the polarizing filter section for polarized light in the other direction is low.

The free-form mirror 22 is an optical member into which the irradiated light reflected by the first mirror 21 is incident and reflects the irradiated light in the direction of the free-form mirror 23 . The reflective surface of the free-form mirror 22 is designed so that the light diameter expands in the direction of the driver's viewpoint 40 in order to project the irradiated light as a virtual image 50 through the windshield 30. Here, the expression "the light diameter expands in the direction of the viewpoint 40" includes not only the case where the light diameter consistently expands after reflection, but also the case where the light diameter shrinks and expands after forming an image at an intermediate point. FIG. 1 shows an example in which the irradiation light reflected by the free-form surface mirror 22 reaches the free-form surface mirror 23 after being imaged at an intermediate imaging position F. Here, the intermediate imaging position F is not limited as long as it is on the optical path of the irradiation light, but it is preferably set between the free-form surface mirror 22 and the free-form surface mirror 23.

The external light blocking section is a member made of a light blocking material, has an opening in a part thereof, and is arranged so that the opening is located on the optical path of the irradiated light. Therefore, the irradiated light passes through the opening and is projected without being blocked by the external light blocking section. Furthermore, even if external light such as sunlight that enters the vehicle from above the windshield 30 is reflected by the free-form mirror 23 and proceeds in the direction of the free-form mirror 22, the external light blocking portion will reduce the amount of light that enters the vehicle. part is blocked. This makes it possible to effectively block external light with the external light blocking section, reduce external light reaching the image irradiation section 10, and suppress deterioration of the image irradiation section 10 due to temperature rise. Furthermore, when the external light blocking section is arranged at the intermediate imaging position F, the area through which the irradiation light passes becomes the smallest. Therefore, the area of the opening formed in the external light blocking section can be made as small as possible, and external light can be blocked more efficiently.

The free-form mirror 23 is an optical member into which the irradiated light reflected by the free-form mirror 22 is incident and reflects the irradiated light in the direction of the windshield 30 . The reflective surface of the free-form mirror 23 is designed so that its light diameter expands in the direction of the driver's viewpoint 40 in order to project the irradiated light as a virtual image 50 through the windshield 30 . Here, the expression "the light diameter expands in the direction of the viewpoint 40" includes not only the case where the light diameter consistently expands after reflection, but also the case where the light diameter shrinks and expands after forming an image at an intermediate point.

The windshield 30 is a portion provided in front of the driver's seat of the vehicle and transmits visible light. The windshield 30 reflects the irradiated light incident from the free-form mirror 23 toward the viewpoint 40 on the inner surface of the vehicle, and transmits the light from the outside of the vehicle toward the viewpoint 40. It corresponds to the department. Here, an example is shown in which the windshield 30 is used as the display section, but a combiner may be prepared as the display section separately from the windshield 30, and the light from the free-form mirror 23 may be reflected in the direction of the viewpoint 40. Furthermore, it is not limited to being located at the front of the vehicle, but may be located at the side or rear as long as it projects an image to the passenger's viewpoint 40.

The virtual image 50 is an image that is displayed as if it were formed in space when the irradiated light reflected by the windshield 30 reaches the viewpoint 40 (eye box) of the driver or the like. The position where the virtual image 50 is formed is determined by the optical path length of the light emitted from the image irradiation unit 10 and the viewpoint 40 after being reflected by the first mirror 21, free-form mirror 22, free-form mirror 23, and windshield 30. It is determined by the spread angle when traveling in the direction.

In the example shown in FIG. 1, a combination of the first mirror 21, free-form surface mirror 22, and free-form surface mirror 23 is shown as the irradiation optical section, but the configuration of the irradiation optical section is not limited to this. For example, in addition to the free-form mirrors 22 and 23, an additional free-form mirror or lens may be used, or a wavelength filter that cuts ultraviolet light or infrared light may be used.

FIG. 2 is a schematic diagram showing the structure of the first mirror 21 in this embodiment, with FIG. 2(a) showing a schematic perspective view and FIG. 2(b) showing a schematic cross-sectional view. As shown in FIGS. 2A and 2B, on the reflective surface of the first mirror 21, the normal direction is the Z axis, and the directions orthogonal to the Z axis are the X axis direction and the Y axis direction. The X-axis direction and the Y-axis direction are also orthogonal to each other. The X-axis direction is a substantially horizontal direction, and in FIG. 1 corresponds to a direction perpendicular to the paper surface. The YZ plane including the Y axis and the Z axis corresponds to the in-plane direction in FIG.

As shown in FIGS. 2A and 2B, the first mirror 21 has a curvature in the Y-axis direction and a flat reflective surface in the X-axis direction. Here, the curvature of the first mirror 21 in the Y-axis direction is not limited, and the entire irradiation optical section 20 including the free-form mirror 22 and the free-form mirror 23 can be designed to have appropriate optical power. Further, the curvature of the first mirror 21 in the Y-axis direction is not limited to a constant value, and the cross section may be a parabolic shape, an elliptical shape, a free-form surface, or the like.

As shown in FIG. 1, the first mirror 21, free-form surface mirror 22, and free-form surface mirror 23 constituting the irradiation optical section 20 are each arranged within the YZ plane. Therefore, in the irradiation light that reaches the windshield 30 from the image irradiation unit 10 via the first mirror 21 and the free-form mirror 22, the reference light beam travels within the YZ plane. In such an arrangement of the irradiation optical section 20, it is preferable that the first mirror 21 has a curvature in the Y-axis direction included in the YZ plane, which is the plane of movement. When the reference light beam of the irradiation light is reflected multiple times with the YZ plane as its traveling plane, aberrations tend to occur in the irradiation light within the YZ plane. Aberrations can be well corrected in the axial direction.

As shown in FIG. 2(b), the first mirror 21 has a laminated structure of a reflective mirror portion 21a, an adhesive layer 21b, and a polarizing filter portion 21c. The reflective mirror portion 21a is a plate-shaped portion made of resin or the like, and has a highly reflective film such as a metal film formed on the reflective surface to reflect the irradiated light on the reflective surface. The adhesive layer 21b is a layer for attaching and fixing the polarizing filter section 21c to the reflective surface of the reflecting mirror section 21a, and is a layer of adhesive or adhesive tape made of a resin material or the like that absorbs irradiated light. . The polarizing filter section 21c is an optical member that reflects polarized light in a predetermined direction and blocks polarized light perpendicular to the predetermined direction, and corresponds to a polarizing plate in the present invention. An example of the polarizing filter section 21c is a flexible thin polarizing film, and an adhesive tape or the like formed in advance on the back surface of the polarizing film can be used as the adhesive layer 21b. Here, an example has been shown in which a polarizing film is used as the polarizing plate and is attached to the reflecting mirror portion 21a, but the polarizing plate may be constructed by directly forming slits or the like on the reflecting surface of the reflecting mirror portion 21a.

In the image projection device 100 of this embodiment, since the polarizing filter section 21c is attached along the reflective surface of the reflecting mirror section 21a with the adhesive layer 21b, it is not necessary to separately provide a member for holding the polarizing filter section 21c. The number of parts can be reduced. Moreover, since the first mirror 21 has a curvature only in the Y-axis direction and is flat in the X-axis direction, even if the polarizing filter part 21c is attached along the surface of the reflecting mirror part 21a, It is possible to suppress the occurrence of distortion and wrinkles in the polarizing filter section 21c.

The polarization direction of the polarized light reflected by the polarizing filter section 21c is not limited to a specific direction as long as it corresponds to the polarization direction of the irradiation light irradiated from the image irradiation section 10. It may also be along a direction inclined at a predetermined angle. However, in order to function as a polarizing plate in a wide area regardless of the incident angle of the irradiated light, it is preferable to reflect polarized light in the direction along the Y-axis or the X-axis.

In the image projection device 100 of this embodiment, the irradiation light irradiated from the image irradiation unit 10 is incident on the first mirror 21 . Since the polarizing filter section 21c provided on the first mirror 21 is provided to reflect the polarization direction of the irradiated light, the irradiated light is not cut by the first mirror 21 and has optical power in the Y-axis direction. The light is then focused or expanded and reflected. The irradiation light reflected by the first mirror 21 is reflected by the free-form surface mirror 22, the free-form surface mirror 23, and the windshield 30, and reaches the viewpoint 40, where a virtual image 50 is formed.

External light such as sunlight entering from above the windshield 30 is reflected by the free-form mirror 23 and the free-form mirror 22 and reaches the first mirror 21 . Since the first mirror 21 is provided with a polarizing filter section 21c, the polarized light in the direction along the reflection axis of the polarizing filter section 21c included in the external light is reflected, but the polarized light in the direction perpendicular to the reflection axis is reflected. be cut. As a result, the intensity of external light that is reflected by the first mirror 21 and reaches the image irradiation section 10 is reduced to about half, and a rise in temperature of the image irradiation section 10 can be suppressed.

As described above, in the image projection device 100 of the present embodiment, the first mirror 21 has a curvature in one axis direction and is flat in the other axis direction orthogonal to the one axis direction, and the first mirror 21 has a curvature on the reflective surface of the first mirror 21. By including a polarizing filter section 21c that reflects polarized light in one direction and cuts polarized light in the other orthogonal direction, it is possible to reduce the number of parts while suppressing the temperature rise of the image irradiation section 10 due to external light. becomes.

(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 perspective view showing the structure of the first mirror 21 in this embodiment. In this embodiment, as shown in FIG. 3, the first mirror 21 has a curvature in the X-axis direction and a flat reflective surface in the Y-axis direction.

The virtual image 50 projected from the image irradiation unit 10 is often a horizontally long image because it presents information for driving support. Therefore, since the first mirror 21 has a curvature in the X-axis direction, it is possible to condense or expand the irradiated light in the X-axis direction, and to perform optical adjustment of the projected image in the horizontal direction favorably.

Also in the image projection device 100 of this embodiment, the first mirror 21 has a curvature in one axis direction and is flat in the other axis direction orthogonal to the one axis direction, and the reflective surface of the first mirror 21 has a curvature in one direction. By providing the polarizing filter section 21c that reflects the polarized light and cuts the polarized light in the other orthogonal direction, it is possible to reduce the number of parts while suppressing the temperature rise of the image irradiating section 10 due to external light.

(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 according to this embodiment and the position of the virtual image formed. As shown in FIG. 4, the image projection device 110 includes an image irradiation section 10, a first mirror 21, and free-form mirrors 22 and 23. The light projected from the image projection device 110 is irradiated onto the driver's viewpoint 40 through the windshield 30 (display section), and a virtual image 50 is formed at a predetermined distance from the windshield 30.

In the image projection device 110 of this embodiment, the irradiation light emitted from the image irradiation unit 10 is reflected by the first mirror 21 and then reflected by the free-form mirrors 22 and 23. Further, the optical path of the irradiation light intersects between the image irradiation unit 10 and the first mirror 21 and between the free-form mirror 22 and the free-form mirror 23. The first mirror 21 is provided with a polarizing filter section 21c, similar to that shown in FIG. 2 in the first embodiment.

Also in this embodiment, since the polarizing filter section 21c is provided on the reflective surface of the first mirror 21, there is no need to separately provide a member for holding the polarizing filter section 21c, and the number of parts can be reduced. Furthermore, since the polarizing filter section 21c is not separately arranged within the space of the irradiation optical section 20, it is possible to intersect the optical path of the irradiation light, and the degree of freedom in designing the arrangement of each member can be increased.

Also in the image projection device 110 of this embodiment, the first mirror 21 has a curvature in one axis direction and is flat in the other axis direction orthogonal to the one axis direction, and the reflective surface of the first mirror 21 has a curvature in one direction. By providing the polarizing filter section 21c that reflects the polarized light and cuts the polarized light in the other orthogonal direction, it is possible to reduce the number of parts while suppressing the temperature rise of the image irradiating section 10 due to external light.

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...Image projection device 10...Image irradiation section 20...Irradiation optical section 30...Windshield 40...Viewpoint 50...Virtual image 21...First mirror 21a...Reflector section 21b...Adhesive layer 21c...Polarizing filter section 22, 23... free-form mirror

Claims (6)

an image irradiation unit that irradiates irradiation light having image information;
a first mirror that reflects the irradiation light incident from the image irradiation unit;
comprising a second free-form surface mirror that reflects the irradiation light incident from the first mirror to reach a viewpoint;
The first mirror has a curvature in one axis direction and is flat in another axis direction perpendicular to the one axis direction,
The image projection device is characterized in that a polarizing filter section is provided on the reflective surface of the first mirror to reflect polarized light in one direction and cut polarized light in another direction orthogonal to the one direction. The image projection device according to claim 1,
The image projection device is characterized in that the polarizing filter section is a polarizing plate pasted along the surface of the reflective surface with an adhesive layer. The image projection device according to claim 1 or 2,
The reference ray of the irradiation light from the image irradiation unit to the second free-form mirror constitutes the same traveling plane,
The image projection device is characterized in that the one-axis direction is included in the traveling plane. The image projection device according to any one of claims 1 to 3,
The image projection device, wherein the one direction of the polarizing filter portion coincides with the one-axis direction or the other-axis direction of the first mirror. The image projection device according to any one of claims 1 to 4,
The image projection device is characterized in that the irradiation light reflected by the second free-form surface mirror is intermediately imaged in the one axis direction and/or the other axis direction on the optical path to the viewpoint. The image projection device according to any one of claims 1 to 5,
An image projection apparatus comprising a third free-form surface mirror that reflects the irradiation light incident from the second free-form surface mirror and causes it to reach a viewpoint.

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