JP2023101953A - Optical system and head-up display device - Google Patents

Abstract

To provide an optical system capable of preventing a video display element from reaching high temperature.SOLUTION: In an optical system 10, a light source 20, a light polarizer 21 with a reflective polarizing plate 30, a video display element 22, and an analyzer 23 are arranged in this order relative to an optical path of light source light L1 emitted from the light source 20. The light polarizer 21 is spaced apart from the video display element 22, and is inclined relative to the light source light L1 incident from the light source 20, and further, is arranged such that at least a part of external light L2 incident through the video display element 22 via the analyzer 23 is polarized and reflected.SELECTED DRAWING: Figure 2

Description

The present invention relates to optical systems and head-up display devices.

Patent Literature 1 discloses a head-up display device (vehicle image display device). A head-up display device is provided on a dashboard of a vehicle, projects image light onto a windshield as a projection plate, and displays driving information as a virtual image.

The head-up display device described above has a video display. The image display has a liquid crystal display panel and a light source, and the liquid crystal display panel has a liquid crystal cell and polarizing plates (polarizer, analyzer) attached to both sides of the liquid crystal cell.

WO2019/082920

However, in the liquid crystal display panel of the image display device, when external light (sunlight) is incident on the polarizing plate from the direction opposite to the light for displaying the image, the polarizing plate tends to absorb the light and generate heat. When the polarizing plate heats up, the temperature of the liquid crystal cell becomes high, and the operation of the liquid crystal cell becomes unstable or is damaged. In particular, the polarizer arranged on the light source side is exposed to a large amount of light from the light source, so that the load tends to increase and the heat generation tends to increase.

The present application has been made in view of this point, and an object of the present application is to provide an optical system and a head-up display device capable of suppressing an image display element such as a liquid crystal cell from becoming hot.

As a result of intensive research, the present inventor found that the above problem can be solved by separating the polarizer from the image display element and tilting it with respect to the light source light incident from the light source, and completed the present invention. That is, aspects of the present invention include the following.

(1) An optical system in which a light source, a polarizer having a reflective polarizing plate, an image display element, and an analyzer are arranged in this order with respect to the optical path of the light source light emitted from the light source, the polarizer is spaced apart from the image display element, inclined with respect to the light source light incident from the light source, and arranged so as to polarize and reflect at least part of external light incident through the image display element via the analyzer.
(2) The optical system according to (1), wherein the wall surface irradiated with the light source light reflected by the polarizer is at least partially covered with a light reflecting material.
(3) The optical system according to (1) or (2), wherein the wall surface irradiated with the external light polarized and reflected by the polarizer having the reflective polarizing plate is at least partially formed of a light-absorbing material or a member having a structure capable of diffuse reflection.
(4) The optical system according to any one of (1) to (3), wherein the polarizer comprises two reflective polarizers.
(5) The optical system of (4), wherein the polarizer comprises an absorptive polarizer positioned between the two reflective polarizers.
(6) The optical system according to (5), wherein the absorptive polarizer has a base material, and the thickness retardation value Rth of the base material in the absorptive polarizer is 40 nm or less.
(7) The optical system according to any one of (1) to (6), wherein the reflective polarizing plate has a wire grid structure on its surface.
(8) The optical system according to (4), wherein the reflective polarizing plate of the polarizer is a wire grid polarizing plate having a wire grid structure on the surface of a substrate, the polarizer includes two wire grid polarizing plates, and the sum of the substrate thickness retardation values Rth of the two wire grid polarizing plates is 40 nm or less.
(9) The optical system of (8), wherein the polarizer comprises an absorptive polarizer between the substrates of the two wire grid polarizers.
(10) The optical system according to any one of (1) to (9), further comprising a light guide, wherein the light guide is configured to guide external light polarized and reflected by the reflective polarizing plate of the polarizer and use it as the light source light.
(11) The optical system according to any one of (1) to (10), wherein the image display element includes two liquid crystal panels, and the pixel size of the liquid crystal panel on the polarizer side of the two liquid crystal panels is larger than the pixel size of the liquid crystal panel on the analyzer side, and the liquid crystal panel on the analyzer side has a color filter.
(12) The optical system according to (11), comprising a reflective polarizing plate between the two liquid crystal panels.
(13) A head-up display device comprising the optical system according to any one of (1) to (12).

ADVANTAGE OF THE INVENTION According to this invention, the optical system and head-up display apparatus which can suppress that an image display element becomes high temperature can be provided.

It is an explanatory view showing an example of application of a head-up display device. It is a schematic diagram which shows an example of the optical system of a head-up display apparatus. It is a schematic diagram showing a polarizer having a glass substrate. It is a schematic diagram which shows the polarizer which has an absorption-type polarizing plate. 1 is a schematic diagram showing an optical system having an image display element with two liquid crystal panels; FIG. 1 is a schematic diagram showing an optical system with a light guide; FIG.

Embodiments of the present invention will be specifically described below. The following embodiments are examples for explaining the present invention, and the present invention is not limited only to these embodiments. The same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, unless otherwise specified, positional relationships such as top, bottom, left, and right in the drawings are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to the illustrated ratios.

FIG. 1 is an explanatory diagram showing an application example of a head-up display device 1 according to this embodiment. As shown in FIG. 1, a head-up display device 1 is provided, for example, on a dashboard 2 of a vehicle. The head-up display device 1 can project image light (display light) 3 onto a windshield 4 as a projection plate to display driving information as a virtual image 5 . A driver 6 can visually recognize the virtual image 5 superimposed on the scenery seen through the windshield 4 . Examples of the projection plate include a windshield of an automobile and a transflective plate called a combiner.

FIG. 2 shows an example of the optical system 10 of the head-up display device 1. As shown in FIG. The optical system 10 has a light source 20 , a polarizer 21 , an image display element 22 , an analyzer 23 , a first wall surface 24 , a second wall surface 25 and a third wall surface 26 .

The light source 20 , the polarizer 21 , the image display element 22 , and the analyzer 23 are arranged in this order along the optical path of the light source light L<b>1 emitted from the light source 20 . In this embodiment, the light source 20, the polarizer 21, the image display element 22, and the analyzer 23 are arranged on a straight line in one direction (vertical direction Y in FIG. 2).

The light source 20 is not particularly limited, and may be, for example, a light emitting diode (LED) that emits white light. There may be one or more light sources 20 . The light source 20 may be arranged so that most of the light source light L1 emitted from the light source 20 is directly incident on the polarizer 21, or the light source 20 may be arranged so that the light source light L1 irradiated and reflected by the first wall surface 24 is incident on the polarizer 21. It is also possible to arrange a plurality of blue, green, and red light-emitting diodes to synthesize the light source light L1, or to arrange a plurality of white light-emitting diodes to control the brightness of each area.

Polarizer 21 has a reflective polarizer. A reflective polarizing plate can transmit one polarized light of incident visible light and reflects the other polarized light. It is preferable to have a unique polarization axis in which the polarization direction of transmitted and reflected polarized light does not change depending on the direction and angle of incident visible light. It is also possible to superimpose two reflective polarizing plates 30 . The reflective polarizing plate 30 can be a wire grid polarizing plate that has a unique polarization (reflection) axis and is capable of polarization separation of light with wavelengths from visible light to infrared light. For example, when each reflective polarizing plate 30 is a wire grid polarizing plate, it has a substrate 40 and a wire grid structure 41 formed on the surface of the substrate 40 . The two reflective polarizers 30 are stacked and glued together such that the wire grid structure 41 is located outside and the substrate 40 is located inside. The two reflective polarizing plates 30 are bonded together with an adhesive. The sum of the thickness retardation values Rth of the substrates 40 of the two reflective polarizing plates 30 is 40 nm or less.

Here, the thickness retardation value Rth can be measured using a retardation value measuring device (ellipsometer KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd.). In addition, the refractive index information of the substrate for measuring the thickness retardation value Rth can be obtained by using a refractive index measurement device (Laser refractive index measurement model 2010 manufactured by Metricon) to obtain a wavelength dispersion diagram of the refractive index from the measurement results of the refractive index at wavelengths of 532 nm, 633 nm and 824 nm using Cauchy's dispersion formula, and from the wavelength dispersion diagram, the refractive index at a wavelength of 550 nm can be obtained.

The polarizer 21 has a plate shape as a whole. The polarizer 21 is separated from the image display element 22, is inclined with respect to the light source light L1 incident from the light source 20, and is arranged so as to reflect at least part of the external light L2 that is incident through the image display element 22 via the analyzer 23. For example, the polarizer 21 is inclined so that one end 21a (first direction X1 of the horizontal direction X in FIG. 2) approaches the image display element 22, and the other end 21b (second direction X2 of the horizontal direction X in FIG. 2) approaches the light source 20. For example, the polarizer 21 is inclined at 45 degrees with respect to the horizontal direction X. Of the polarized light, it is preferable to adjust the direction of the polarization transmission axis so as to transmit the P wave, but it is necessary to consider the polarization state of the image to be displayed, etc., and the invention is not limited to this.

For example, the image display element 22 is a liquid crystal panel (liquid crystal cell) in which liquid crystal is sealed between a pair of translucent substrates on which transparent electrode films are formed. The image display element 22 has a thick flat plate shape.

The analyzer 23 preferably uses a polarizing plate having a unique polarization axis. Since the absorptive polarizing plate that absorbs the other polarized light can absorb and cut unnecessary light as image light out of the polarized light that has passed through the polarizer, it can prevent the generation of stray light and can be suitably used. On the other hand, external light is also absorbed, but in order to prevent this, measures such as providing a reflective polarizing plate on the external light incident side can be taken. The polarization axis directions of the polarizer 21 and the analyzer 23 are, for example, orthogonally arranged, so that the light source light L1 modulated by the image display element 22 is polarized and separated to generate an image. The analyzer 23 has a flat plate shape and is adhered to the surface of the image display element 22 opposite to the light source 20 (outside). The polarization axis means the polarization transmission axis and the polarization reflection axis in the reflective polarizing plate, and means the polarization transmission axis and the polarization absorption axis in the absorptive polarizing plate. In addition, when two polarizing plates are superimposed and arranged so that their polarization transmission axes are orthogonal to each other in the direction in which light is incident and transmitted, the polarization axis directions are said to be orthogonal to each other.

The first wall surface 24, the second wall surface 25, and the third wall surface 26 are arranged in a U shape around the polarizer 21 on the paper surface of FIG. Although not shown in this drawing, light-shielding walls can be appropriately provided in front of and behind the page of FIG. 2 to prevent stray light, but this is an arbitrary design matter.

For example, the first wall surface 24 is arranged around the light source 20 at a position on the light source 20 side of the polarizer 21 (under the polarizer 21 in FIG. 2). The first wall surface 24 is, for example, parallel to the image display element 22 and faces upward.

The second wall surface 25 is arranged on the side of the end portion 21a of the polarizer 21 (the first direction X1 of the horizontal direction X of the polarizer 21 in FIG. 2). The second wall surface 25 faces the polarizer 21 (second direction X2).

The first wall surface 24 and the second wall surface 25 are walls on which the light source light L1 reflected by the polarizer 21 is incident. A part or the whole of the first wall surface 24 and the second wall surface 25 is formed of a light reflecting material. The first wall surface 24 and the second wall surface 25 are mirror surfaces, for example. A specular surface is one that can reflect without changing the polarization state.

The third wall surface 26 is arranged on the side of the end portion 21b of the polarizer 21 (second direction X2 of the horizontal direction X of the polarizer 21 in FIG. 2). The third wall surface 26 faces the polarizer 21 side (first direction X1). The third wall surface 26 is a wall surface on which the external light L2 reflected by the polarizer 21 is incident. A part or the whole of the third wall surface 26 is formed of a light absorbing material or a member having a structure capable of diffuse reflection. The light-absorbing material is, for example, a black material. A member having a diffusely reflective structure is, for example, a wall with a rough surface.

Next, the operation of the optical system 10 configured as above will be described.

The light source light L1 emitted from the light source 20 is incident on the polarizer 21 , and part of the light is transmitted through the polarizer 21 and is incident on the image display element 22 . The light source light L1 is modulated by the image display element 22, polarized and separated by the analyzer 23, and becomes image light. As shown in FIG. 1, this image light is projected onto a windshield 4 as a projection plate, and driving information is displayed as a virtual image 5. FIG. A driver 6 superimposes the virtual image 5 on the scenery through the windshield 4 and visually recognizes it.

As shown in FIG. 2, part of the light source light L1 reflected by the reflective polarizing plate 30 of the polarizer 21 is incident on the second wall surface 25 and reflected, reflected again by the reflective polarizing plate 30, and reflected by the first wall surface 24. This part of the light source light L1 passes through the polarizer 21, passes through the image display element 22 and the analyzer 23, and becomes image light.

On the other hand, external light L2 such as sunlight may enter the optical system 10 from the windshield 4 side. The external light L2 is polarized and transmitted through the analyzer 23 and enters the image display element 22, and the external light L2 reaching the reflective polarizing plate 30 of the polarizer 21 is polarized and reflected. The reflected outside light L2 enters the third wall surface 26 and is absorbed or diffused.

According to the present embodiment, the optical system 10 includes the polarizer 21 having the reflective polarizing plate 30. The polarizer 21 is separated from the image display element 22, is arranged so as to be inclined with respect to the light source light L1 incident from the light source 20, and to polarize and reflect at least part of the external light L2 incident through the image display element 22 via the analyzer 23. As a result, the external light L2 passes through the image display element 22, is reflected by the reflective polarizing plate 30 of the polarizer 21 away from the image display element 22, and leaves the optical path of the image light 3 or the light source light L1. This suppresses the image display element 22 from absorbing the external light L2 and generating heat, and suppresses the image display element 22 from becoming hot. Degradation of the analyzer 23 and the polarizer 21 can also be suppressed, and since polarized light is reflected in a direction away from the optical path, deterioration of image quality due to re-reflection of external light can be suppressed.

The second wall surface 25 is a wall surface on which the light source light L1 reflected by the polarizer 21 is incident, and at least a portion of the second wall surface 25 is covered with a light reflecting material. With such a configuration, the light source light L1 reflected by the second wall surface 25 can be returned to the polarizer 21 and the image display element 22 and reused, thereby improving the light utilization efficiency.

The third wall surface 26 is a wall surface on which the external light L2 reflected by the reflective polarizing plate 30 of the polarizer 21 is incident, and at least a portion thereof is made of a light-absorbing material or a member having a structure capable of diffuse reflection. With such a configuration, it is possible to prevent the external light L2 reflected by the third wall surface 26 from being re-reflected and becoming stray light.

Since the polarizer 21 includes the two reflective polarizing plates 30, it is possible to sufficiently reflect the light source light L1 and the external light L2.

The reflective polarizing plate 30 of the polarizer 21 has an anisotropic wire grid structure 41 on its surface. A wire grid structure is a structure in which thin metal wires extending in a predetermined direction are aligned. By setting the period of the metal fine wires to be about 1/3 or 1/4 or less of the wavelength of light for which polarization separation is desired, polarized light separation can be achieved in which polarized light parallel to the metal fine wires is reflected and polarized light perpendicular to the metal fine wires is transmitted. In order to polarization-separate visible light of 400 nm to 700 nm, it is preferable to set the period (pitch) of the fine metal wires of the wire grid structure to 100 nm to 140 nm. Thereby, the broadband external light L2 including infrared light can be appropriately polarized and separated. In addition, by using aluminum as the metal that forms the fine wires, it has a broadband polarization reflectivity, and the reflection of the external light L2 and the light source light L1 in the polarizer 21 can be increased and the absorption thereof can be reduced. As a result, the generation of heat can be suppressed. A wire grid structure can be obtained by providing a nano-sized concave-convex structure extending in a desired direction on the substrate surface and forming a metal film on one side surface of the convex portion of the periodic concave-convex structure. In this case, since the metal (fine metal wire) is formed on one side surface of the projections on the base material surface in the cross section in the direction in which the uneven structure extends, the shape is asymmetrical. Since light enters the polarizer 21 at an angle, when P-waves are to be polarized and transmitted, it is preferable to arrange such that the light enters the other side surface on which the convex metal (fine metal wire) is not formed, or the transmitted polarized light is emitted from the side surface.

The reflective polarizing plate 30 of the polarizer 21 is a wire grid polarizing plate having a wire grid structure 41 on the surface of the substrate 40. The polarizer 21 includes two wire grid polarizing plates, and the sum of the thickness retardation values Rth of the substrates 40 of the two wire grid polarizing plates is 40 nm or less. When the polarizer 21 includes two wire grid polarizing plates, has a wire grid structure 41 on the surface thereof, and is inclined with respect to the light source light L1 incident from the light source 20, the thickness direction retardation value Rth of the base material 40 tends to cause in-plane non-uniformity of transmitted light (amount). This is because there is a wire grid structure as a polarization separation layer on both surfaces of the polarizer 21, and the polarization state of light passing through the base material changes. By setting the sum of the thickness retardation values Rth of the base material 40 to 40 nm or less, the influence of the thickness direction retardation values Rth can be suppressed, the state of polarized light transmitted through the polarizer 21 can be appropriately maintained, and the uniformity of transmitted light (amount) can be ensured. Note that the reflective polarizing plate 30 may be a laminate film or the like in which birefringent films having mutually different birefringences are laminated.

In the above embodiment, the polarizer 21 may be provided with a glass substrate 60 as a core material between two reflective polarizing plates 30 as shown in FIG. By providing the glass substrate 60, it is possible to dissipate heat through heat conduction, and to prevent deformation of the polarizer 21 due to heat or impact.

In the above embodiment, the polarizer 21 may include an absorptive polarizer 70 between two reflective polarizers 30 as shown in FIG.

For example, the absorptive polarizing plate 70 has an absorptive polarizing layer 80 and two substrates 81 and 82 provided on both sides of the absorptive polarizing layer 80 . For example, the absorptive polarizing layer 80 includes a stretched layer of polyvinyl alcohol impregnated with a dichroic dye or iodine. The substrates 81 and 82 protect both sides of the absorptive polarizing layer 80, and include, for example, films made of triacetyl cellulose. The thickness retardation value Rth (sum) of the two substrates 81 and 82 is 40 nm or less.

The reflective polarizing plate 30 , the glass substrate 60 , the substrate 81 , the absorbing polarizing layer 80 , the substrate 82 , and the reflective polarizing plate 30 are arranged in this order from the light source 20 toward the image display element 22 . The glass substrate 60 and the absorptive polarizer 70, and the absorptive polarizer 70 and the reflective polarizer 30 are bonded with an adhesive. As the adhesive material, a material having a glass transition point of 0 degrees or less and being soft and non-oriented at room temperature is preferable.

According to this example, since the absorptive polarizing plate 70 is included between the reflective polarizing plates 30 of the polarizer 21, stray light reflected between the reflective polarizing plates 30 when the light source light L1 is transmitted through the polarizer 21 can be suppressed. Further, since the thickness retardation value Rth of the substrates 81 and 82 of the absorbing polarizing plate 70 is 40 nm or less, the decrease (non-uniformity) of the transmittance of the polarizer 21 can be suppressed. When the absorbing polarizing plate 70 has one base material, the thickness retardation value Rth of the one base material is set to 40 nm or less.

In the above embodiment, the image display element 22 may have two liquid crystal panels 90 and 91 as shown in FIG. Also, the image display element 22 may include a reflective polarizing plate 92 between the two liquid crystal panels 90 and 91 . The polarization axis direction of the reflective polarizing plate 92 is preferably parallel to the polarization axis direction of the polarizer 21 . Also, an absorptive polarizer may be provided on the side of the liquid crystal panel 91 of the reflective polarizer 92, and the absorptive polarizer may have a relatively low polarization splitting property to prevent stray light.

The liquid crystal panel 90 is arranged on the polarizer 21 side of the reflective polarizing plate 92 , and the liquid crystal panel 91 is arranged on the analyzer 23 side of the reflective polarizing plate 92 . The pixel size of the liquid crystal panel 90 on the polarizer 21 side is larger than the pixel size of the liquid crystal panel 91 on the analyzer 23 side. Liquid crystal panel 91 has a color filter, and liquid crystal panel 90 does not have a color filter. Thereby, the liquid crystal panel 90 performs switching between the image display area and the image non-display area, and the liquid crystal panel 91 creates an image.

According to this example, the image display element 22 includes two liquid crystal panels 90 and 91, the pixel size of the liquid crystal panel 90 is larger than the pixel size of the liquid crystal panel 91, and the liquid crystal panel 91 has a color filter. As a result, the image quality (contrast ratio) is improved, and the image display element 22 can create a high-quality image.

Since the image display element 22 is provided with a reflective polarizing plate 92 between the two liquid crystal panels 90 and 91, the unnecessary light source light L1 in the image non-display area transmitted through the liquid crystal panel 90 is reflected by the reflective polarizing plate 92, reflected by the polarizer 21, and exits the system. As a result, the unnecessary light source light L1 is not reflected multiple times and becomes stray light, so that deterioration of image quality can be suppressed. Further, since the light source light L1 does not reach the image non-display area of the liquid crystal panel 91, unnecessary heat generation can be suppressed.

Since the liquid crystal panel 90 does not have a color filter, unnecessary heat generation can be suppressed.

In the above embodiment, as shown in FIG. 6, the optical system 10 includes a light guide 100, and the light guide 100 may be configured to guide the external light L2 polarized and reflected by the reflective polarizing plate 30 of the polarizer 21 and use it as the light source light L1.

A light guide 100 is arranged on the third wall surface 26 . For example, the light guide 100 has a light guide plate 101 having a finely shaped surface and a reflector 102 that reflects light passing through the light guide plate 101 toward the first wall surface 24 . Note that the light guide 100 may be a diffusion plate, a diffraction grating, or the like. For example, the light source 20 may be arranged on the second wall surface 25 opposite to the third wall surface 26 and directed toward the first wall surface 24 . The first wall surface 24 is provided with a diffuse reflection plate 110 that reflects the light source light L1 emitted from the light source 20 and the reflection plate 102 toward the polarizer 21 side. In order to brighten the image light, the diffuse reflection plate 110 can control the reflection direction of the light from the light source by providing a diffusion structure such as forming uneven shapes with a relatively small period in an uneven shape with a large period. A lens 111 is provided between the polarizer 21 and the image display element 22 to adjust the light reflected by the diffuse reflector 110 and passing through the polarizer 21 . The front retardation value of the lens 111 is preferably 20 nm or less, and the thickness direction retardation value is preferably 40 nm or less. In place of the lens 111, a light control plate having a prism-shaped surface or a diffusion plate with a low haze value may be used between the light source 20 and the polarizer 21 in order to control the irradiation direction of the light source light L1.

In this case, the external light L2 passes through the analyzer 23 and the image display element 22, is polarized and reflected by the reflective polarizing plate 30 of the polarizer 21, and enters the light guide 100 on the third wall surface 26. FIG. The light incident on the light guide 100 passes through the light guide plate 101, is reflected by the reflector 102, is emitted toward the first wall surface 24, is reflected by the diffuse reflector 110 on the first wall surface 24, and is reused as light source light L1. That is, the light source light L1 originating from the external light L2 passes through the polarizer 21 and the lens 111, passes through the image display element 22 and the analyzer 23, and becomes image light.

According to this example, the external light L2 can be reused as the light source light L1.

In the above embodiment, the reflective polarizing plate 30 has the wire grid structure 41 on its surface, but it may be another reflective polarizing plate that does not have the wire grid structure. In the above embodiment, the polarizer 21 has two reflective polarizing plates 30, but may have one reflective polarizing plate. The optical system 10 and the head-up display device 1 can be applied to other than vehicles.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. Various modifications are possible without departing from the gist of the present invention. For example, some components in one embodiment can be added to other embodiments within the scope of ordinary creativity of those skilled in the art. Also, some components in one embodiment may be replaced with corresponding components in other embodiments.

INDUSTRIAL APPLICABILITY The present invention is useful in providing an optical system capable of suppressing an image display element from becoming hot.

Reference Signs List 1 head-up display device 10 optical system 20 light source 21 polarizer 22 image display element 23 analyzer 30 reflective polarizing plate L1 light source light L2 outside light

Claims (13)

A light source, a polarizer having a reflective polarizing plate, an image display element, and an analyzer are arranged in this order with respect to the optical path of the light source light emitted from the light source,
The optical system, wherein the polarizer is spaced apart from the image display element, is inclined with respect to light source light incident from the light source, and is disposed so as to polarize and reflect at least part of external light incident through the image display element via the analyzer. The wall surface irradiated with the light source light reflected by the polarizer is configured such that at least a portion thereof is covered with a light reflective material.
2. The optical system of claim 1. At least a part of the wall surface irradiated with the external light polarized and reflected by the polarizer having the reflective polarizing plate is formed of a light-absorbing material or a member having a structure capable of diffuse reflection.
3. An optical system according to claim 1 or 2. The polarizer comprises two of the reflective polarizing plates,
4. An optical system according to any one of claims 1-3. the polarizer comprises an absorptive polarizer positioned between the two reflective polarizers;
5. Optical system according to claim 4. The absorptive polarizing plate has a base material,
The thickness retardation value Rth of the substrate in the absorptive polarizing plate is 40 nm or less.
6. Optical system according to claim 5. The reflective polarizing plate has a wire grid structure on its surface,
7. An optical system according to any one of claims 1-6. The reflective polarizing plate of the polarizer is a wire grid polarizing plate having a wire grid structure on the surface of the base material,
The polarizer comprises two wire grid polarizers,
The sum of the thickness retardation values Rth of the substrates of the two wire grid polarizers is 40 nm or less.
5. Optical system according to claim 4. The polarizer has an absorptive polarizer between the substrates of the two wire grid polarizers.
9. Optical system according to claim 8. further comprising a light guide,
The light guide is configured to guide external light polarized and reflected by the reflective polarizing plate of the polarizer and use it as the light source light.
10. An optical system according to any one of claims 1-9. The image display element includes two liquid crystal panels,
Among the two liquid crystal panels, the pixel size of the liquid crystal panel on the polarizer side is larger than the pixel size of the liquid crystal panel on the analyzer side,
The liquid crystal panel on the analyzer side has a color filter,
11. An optical system according to any one of claims 1-10. A reflective polarizing plate is provided between the two liquid crystal panels,
12. Optical system according to claim 11. having an optical system according to any one of claims 1 to 12,
Head-up display device.

Images