JP2017173424A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decrease in resolution as the pitch of pixels of a projection type display device is narrowed.SOLUTION: A projection type display device 1 includes: at least one or more of reflection type display elements 30B, 30G, and 30R; a polarization separation element 12 that reflects light from the reflection type display element 30R; and a projection optical system 40 that projects light reflected on the polarization separation element 12. The polarization separation element 30R includes a dielectric multilayer film disposed between a pair of transparent base members. The total thickness of the dielectric multilayer film is larger than the pixel pitch of the reflection type display element 30R. Of the dielectric multilayer film, the thickness of the region to reflect light with a predetermined wavelength region is less than or equal to √2/2 times the pixel pitch.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a projection display device.

  As a display device, there is known a projection display device (so-called projector) that modulates light emitted from a light source with a reflective display element and enlarges and projects the modulated light onto a projection surface by a projection optical system. ing.

  In an optical system of such a projection display device, a polarization separation element (also referred to as a polarization beam splitter) that controls transmission or reflection of incident light according to the polarization direction of light is used. The projection type display device uses a dichroic filter that separates light at a wavelength or controls the polarization direction of light to separate the light of the light source into each color, and an image of each color is displayed on the reflective display element. After the generation, the enlarged projection image is synthesized.

  For example, in Patent Document 1 below, a phase difference plate that selectively rotates the polarization direction of light in a specific wavelength region is used to project light reflected by a projection lens or the like to return light. A projection display device that improves the contrast of an image to be displayed is disclosed.

JP 2011-154381 A

  However, in the projection display device disclosed in Patent Document 1 and the like, as the resolution of the reflective display element increases, the image is projected in two or three parts, or the projected image is blurred. Has occurred. In such a case, the resolution of the image projected by the projection display device is reduced.

  Therefore, the present disclosure proposes a new and improved projection display device that can prevent a reduction in resolution of a projected image.

  According to the present disclosure, at least one reflective display element, a polarization separation element that reflects light from the reflection display element, and a projection optical system that projects light reflected by the polarization separation element; The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates, and the entire thickness of the dielectric multilayer film is larger than the pixel pitch of the reflective display element. In the dielectric multilayer film, there is provided a projection display device in which a film thickness of a region that reflects light in a predetermined wavelength region is not more than √2 / 2 times the pixel pitch.

According to the present disclosure, at least one or more reflective display elements, a polarization separation element that reflects light from the reflection display element, and projection optics that projects light reflected by the polarization separation element The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates, and the total film thickness of the dielectric multilayer film is equal to the pixel pitch p of the reflective display element. The region of the dielectric multilayer film that reflects light in a predetermined wavelength region is formed of an N-layer multilayer film, and is the i-th multilayer counted from the light incident surface of the predetermined wavelength region. When the thickness of the predetermined refraction angle of the light in the wavelength region theta _i, i-th multilayer film in film and t _i, the dielectric multilayer film satisfies equation 1 below, provides a projection type display device Is done.

  According to the present disclosure, it is possible to prevent light incident on the polarization separation element after being reflected by the reflective display element from being divided into two or more by the dielectric multilayer film of the polarization separation element. Can do.

  As described above, according to the present disclosure, it is possible to prevent a decrease in resolution of an image projected by the projection display device.

  Note that the above effects are not necessarily limited, and any of the effects shown in the present specification, or other effects that can be grasped from the present specification, together with or in place of the above effects. May be played.

It is a schematic diagram which shows the optical system of the projection type display apparatus which concerns on 1st Embodiment of this indication. It is explanatory drawing explaining the reason for which resolution falls in the 1st polarization separation element. It is a schematic diagram explaining the 1st polarization separation element used for the projection type display apparatus which concerns on the same embodiment. It is explanatory drawing which examined the optical path of the green light in the green light reflection area | region of the embodiment in detail. It is an image which shows the improvement of the resolution by the same embodiment. It is an image which shows the fall of the resolution by the 1st polarization separation element. It is explanatory drawing explaining the reason for which resolution falls in the 2nd polarization separation element. It is a schematic diagram explaining the 2nd polarization separation element used for the projection type display apparatus which concerns on 2nd Embodiment. It is explanatory drawing which examined the optical path of the red light in the red light reflection area | region of the embodiment in detail. It is an image which shows the improvement of the resolution by the same embodiment. It is an image which shows the fall of the resolution by the 2nd polarization separation element.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. 1. First embodiment 1.1. Configuration of Projection Display Device 1.2. 1. Configuration of polarization separation element Second Embodiment 2.1. 2. Configuration of polarization separation element Summary

<1. First Embodiment>
[1.1. Configuration of Projection Display Device]
First, an overview of the projection display device 1 according to the first embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a schematic diagram showing an optical system of a projection display device according to this embodiment.

  In the following, the blue light 2B is light belonging to the blue wavelength region, for example, represents light having a wavelength of 430 nm to 500 nm, and the yellow light 2Y is light mainly in the yellow wavelength region, For example, it represents light having a wavelength of 500 nm to 660 nm. The red light 2R is light belonging to the red wavelength region, for example, representing light having a wavelength of 580 nm to 660 nm, and the green light 2G is light belonging to the green wavelength region, for example, 500 nm to 580 nm. Represents light having a wavelength of.

  As shown in FIG. 1, in the projection display device 1 according to the present embodiment, first, blue light 2 </ b> B and yellow light 2 </ b> Y are emitted from a light source 20.

  The blue light 2 </ b> B passes through the wavelength selective phase difference plate 21, is reflected by the reflective polarizing plate 22, and is guided to the wavelength selective phase difference plate 24 and the second polarization separation element 12. Subsequently, the blue light 2B is reflected by the second polarization separation element 12 and incident on the compensation plate 31B and the blue reflective display element 30B, thereby being modulated for a blue image. Thereafter, the modulated blue light 2 </ b> B passes through the second polarization separation element 12 and the wavelength selective phase difference plate 26, and is guided to the first polarization separation element 11.

  On the other hand, the yellow light 2Y passes through the wavelength selective phase difference plate 21, and then enters the reflective polarizing plate 22, and is separated into green light 2G and red light 2R depending on the polarization direction of the light. Specifically, among the yellow light 2 </ b> Y, the green light 2 </ b> G is transmitted through the reflective polarizing plate 22, and the red light 2 </ b> R is reflected by the reflective polarizing plate 22.

  The red light 2R reflected by the reflective polarizing plate 22 passes through the wavelength selective phase difference plate 24, then passes through the second polarization separation element 12, and passes through the compensation plate 31R and the red reflective display element 30R. Incident light is modulated for a red image. Thereafter, the modulated red light 2 </ b> R is reflected by the second polarization separation element 12, passes through the wavelength selective phase difference plate 26, and is guided to the first polarization separation element 11.

  The green light 2G transmitted through the reflective polarizing plate 22 is transmitted through the retardation plate 23, then reflected by the third polarization separation element 13, and incident on the compensation plate 31G and the green reflective display element 30G. , Modulated for a green image. Thereafter, the modulated green light 2 </ b> G passes through the third polarization separation element 13 and the phase difference plate 25 and is guided to the first polarization separation element 11.

  In the first polarization separation element 11, the blue light 2B and the red light 2R are transmitted, and the green light 2G is reflected, whereby the blue light 2B, the red light 2R, and the green light 2G are combined to generate a projection image. . The generated projection image is enlarged and projected from the projection optical system 40 onto the projection surface.

  Then, each structure of the projection type display apparatus which concerns on this embodiment is demonstrated. Note that P-polarized light represents polarized light having an electric field vibration direction in a plane parallel to the paper surface in FIG. 1, and S-polarized light represents polarized light having an electric field vibration direction in a surface perpendicular to the paper surface in FIG.

  The light source 20 is a light source that emits blue light 2 </ b> B and yellow light 2 </ b> Y that are substantially parallel and S-polarized. For example, the light source 20 may be a halogen lamp that emits non-polarized light, a xenon lamp, a metal halide lamp, a mercury lamp, or the like. In such a case, the non-polarized light emitted from the light source 20 is reflected by a reflector or the like and transmitted through the polarization conversion element and the color filter, so that the light emitted from the light source 20 is substantially parallel and is S-polarized blue. It can be converted into light 2B and yellow light 2Y. The light source 20 may be a semiconductor laser light source that emits blue light 2B and yellow light 2Y. Since the semiconductor laser light source can emit substantially parallel light in a predetermined polarization direction (for example, S-polarized light), when the semiconductor laser light source is used, a reflector, a polarization conversion element, a color filter, and the like can be omitted.

  The wavelength selective phase difference plate 21 rotates the polarization direction of light of a specific wavelength by 90 degrees. Specifically, the wavelength-selective retardation plate 21 converts the green light 2G included in the yellow light 2Y from S-polarized light to P-polarized light by rotating the polarization direction of the light in the green wavelength region by 90 degrees.

  The reflective polarizing plate 22 is a polarizing plate that reflects S-polarized light and transmits P-polarized light. Specifically, the reflective polarizing plate 22 reflects S-polarized blue light 2B and red light 2R, and transmits P-polarized green light 2G. Thereby, the yellow light 2Y incident on the reflective polarizing plate 22 is separated into red light 2R reflected by the reflective polarizing plate 22 and green light 2G transmitted through the reflective polarizing plate 22. In addition, the reflective polarizing plate 22 can be comprised with the glass substrate etc. which have arrange | positioned the metal which has free electrons, such as aluminum, in a grid | lattice form.

  The wavelength selective phase difference plate 24 rotates the polarization direction of light of a specific wavelength by 90 degrees. Specifically, the wavelength-selective retardation plate 24 converts the red light 2R from S-polarized light to P-polarized light by rotating the polarization direction of light in the red wavelength region by 90 degrees.

  The second polarization separation element 12 is an optical element in which a dielectric multilayer film is sandwiched between a pair of transparent substrates, and reflects S-polarized light and transmits P-polarized light. Specifically, the second polarization separation element 12 reflects the S-polarized blue light 2B before entering the blue reflective display element 30B and the P-polarized light before entering the red reflective display element 30R. The red light 2R is transmitted. Thereby, the blue light 2B incident on the second polarization separation element 12 is guided to the blue reflective display element 30B, and the red light 2R is guided to the red reflective display element 30R.

  The second polarization separation element 12 transmits the P-polarized blue light 2B after entering the blue reflective display element 30B and transmits the S-polarized red light after entering the red reflective display element 30R. Reflects 2R. Accordingly, the second polarization separation element 12 can guide the P polarization in the blue light 2B and the S polarization in the red light 2R to the first polarization separation element 11. As will be described later, the light incident on the second polarization separation element 12 from the blue reflective display element 30B and the red reflective display element 30R is converted from the blue light 2B in the bright display state to P-polarized light, thereby displaying brightly. The red light 2R in the state is converted to S-polarized light. Therefore, the second polarization separation element 12 can guide the blue light 2B and the red light 2R in the bright display state to the first polarization separation element 11.

  The compensation plates 31B and 31R are retardation plates that correct the polarization direction of the obliquely incident blue light 2B or red light 2R. The compensation plates 31B and 31R may be quarter wave plates, for example.

  The blue reflective display element 30B is, for example, a reflective liquid crystal panel, and modulates the blue light 2B for a blue image based on input image information. Specifically, the blue reflective display element 30B does not rotate the polarization of the incident blue light 2B in the dark display state (that is, the state where no light is projected onto the projection surface), and does not rotate the polarized light state. In a state where light is projected onto the surface), the polarization of the incident blue light 2B is rotated by 90 degrees. Thus, the blue light 2B reflected by the blue reflective display element 30B is P-polarized in the bright display state and S-polarized in the dark display state, so that only the blue light 2B in the bright display state is the second polarized light. The light passes through the separation element 12 and is guided to the first polarization separation element 11.

  The red reflective display element 30R is, for example, a reflective liquid crystal panel, and modulates the red light 2R for a red image based on input image information. Specifically, the red reflective display element 30R does not rotate the polarization of the incident red light 2R in the dark display state, and rotates the polarization of the incident red light 2R by 90 degrees in the bright display state. As a result, the red light 2R reflected by the red reflective display element 30R is S-polarized light in the bright display state and P-polarized light in the dark display state, so only the red light 2R in the bright display state is the second polarized light. The light is reflected by the separation element 12 and guided to the first polarization separation element 11.

  The wavelength selective phase difference plate 26 rotates the polarization direction of light of a specific wavelength by 90 degrees. Specifically, the wavelength selective phase difference plate 26 converts the red light 2R from S-polarized light to P-polarized light by rotating the polarization direction of the light in the red wavelength region by 90 degrees.

  The phase difference plate 23 rotates the polarization direction of the incident light by 90 degrees. Specifically, the phase difference plate 23 is a half-wave plate, and converts the green light 2G from P-polarized light to S-polarized light by rotating the polarization direction of incident light by 90 degrees.

  The third polarization separation element 13 is an optical element in which a dielectric multilayer film is sandwiched between a pair of transparent substrates, and reflects S-polarized light and transmits P-polarized light. Specifically, the third polarization separation element 13 reflects S-polarized green light 2G before entering the green reflective display element 30G, and P-polarized light after entering the green reflective display element 30G. The green light 2G is transmitted. Accordingly, the third polarization separation element 13 guides the incident green light 2G to the green reflective display element 30G, and converts the P-polarized light out of the green light 2G incident from the green reflective display element 30G to the first. The light can be guided to the polarization separation element 11. As will be described later, as for light incident on the third polarization separation element 13 from the green reflective display element 30G, the green light 2G in the bright display state is converted into P-polarized light. Therefore, the third polarization separation element 13 can guide the green light 2G in the bright display state to the first polarization separation element 11.

  The compensation plate 31G is a retardation plate that corrects the polarization direction of the obliquely incident green light 2G. The compensation plate 31G may be, for example, a quarter wavelength plate.

  The green reflective display element 30G is, for example, a reflective liquid crystal panel, and modulates the green light 2G for a green image based on input image information. Specifically, the green reflective display element 30G does not rotate the polarization of the incident green light 2G in the dark display state, and rotates the polarization of the incident green light 2G by 90 degrees in the bright display state. Thus, the green light 2G reflected by the green reflective display element 30G is P-polarized in the bright display state and S-polarized in the dark display state, and therefore only the green light 2G in the bright display state is the third polarized light. The light passes through the separation element 13 and is guided to the first polarization separation element 11.

  The phase difference plate 25 rotates the polarization direction of the incident light by 90 degrees. Specifically, the phase difference plate 25 is a half-wave plate and converts the green light 2G from P-polarized light to S-polarized light by rotating the polarization direction of incident light by 90 degrees.

  The first polarization separation element 11 is an optical element in which a dielectric multilayer film is sandwiched between a pair of transparent base materials, and reflects S-polarized light and transmits P-polarized light. Specifically, the first polarization separation element 11 reflects S-polarized green light 2G and transmits P-polarized blue light 2B and red light 2R. Thereby, the blue light 2B, the red light 2R, and the green light 2G that have entered the first polarization separation element 11 are combined into a projection image and guided to the projection optical system 40.

  In the projection display device 1 according to the present embodiment, the reduction of the resolution of the projection display device 1 is prevented by controlling the S-polarized light reflection characteristics of the dielectric multilayer film included in the first polarization separation element 11. Can do. A specific configuration of the first polarization separation element 11 used in the projection display device 1 according to the present embodiment will be described later.

  The wavelength selective phase difference plate 27 rotates the polarization direction of light of a specific wavelength by 90 degrees. Specifically, the wavelength-selective retardation plate 27 converts the green light 2G from S-polarized light to P-polarized light by rotating the polarization direction of the light in the green wavelength region by 90 degrees. Thereby, the polarization directions of the blue light 2B, the red light 2R, and the green light 2G incident on the projection optical system 40 are all aligned with the P-polarized light.

  The projection optical system 40 includes a projection lens, and projects a projection image composed of incident blue light 2B, red light 2R, and green light 2G. According to the projection optical system 40, the projection display device according to the present embodiment projects images input to the blue reflective display element 30B, the red reflective display element 30R, and the green reflective display element 30G. Can be magnified on top.

[1.2. Configuration of polarization separation element]
Next, the configuration of the first polarization separation element 11 used in the projection display device 1 according to the present embodiment will be described with reference to FIGS.

  First, the background of the present embodiment will be described with reference to FIG. FIG. 2 is an explanatory diagram for explaining the reason why the resolution decreases in the first polarization separation element.

  The inventors of the present invention have made extensive developments in order to improve the resolution of the projection display device. When the pixel pitch of the reflective display element is extremely narrow (for example, 4 μm or less), the image is displayed on the projection surface. It has been found that the resolution of the image decreases.

  Specifically, as shown in FIG. 5B, the present inventors display a cross hatch image on the projection surface in the projection display device, and some lines are displayed twice. I found. In such a case, since the image of the pixel displayed doubly affects the image of the adjacent pixel, the resolution of the projection display device is lowered.

  As a result of further studies, the present inventors have found that the above-described decrease in resolution is due to the reflection position of S-polarized light incident on the polarization separation element being divided into a plurality of parts. This knowledge will be described more specifically with reference to FIG. 2 while explaining the configuration of the polarization separation element.

  As shown in FIG. 2, the first polarization separation element 1100 includes a pair of transparent base materials 1110 and 1120, a dielectric multilayer film 1130 sandwiched between the pair of transparent base materials 1110 and 1120, an adhesive layer 1140, and a reflective layer. A prevention layer 1150.

  The transparent base materials 1110 and 1120 are configured by a substantially triangular prism-shaped prism structure using a transparent glass material or resin material capable of transmitting incident light.

  The dielectric multilayer film 1130 has a structure in which a plurality of dielectric materials having different refractive indexes are laminated so that a dielectric material having a high refractive index and a dielectric material having a low refractive index are alternated. With such a laminated structure, the dielectric multilayer film 1130 can reflect light at the interface between dielectrics having different refractive indexes. Further, when the incident angle of incident light is near the Brewster angle, the reflectance of P-polarized light is 0, so that the dielectric multilayer film 1130 can reflect S-polarized light while transmitting P-polarized light. become.

  In addition, the thickness of each layer of the dielectric multilayer film 1130 is designed so that the phases of light reflected at the interfaces of the stacked layers are aligned with each other. Since the phases of the light reflected at the interfaces of the respective layers are aligned, the light reflected at the interfaces of the respective layers strengthen each other, so that the dielectric multilayer film 1130 can improve the reflectance of S-polarized light.

  The adhesive layer 1140 bonds the transparent base material 1120 on which the dielectric multilayer film 1130 is formed and the transparent base material 1110 on which the antireflection layer 1150 is formed. Specifically, the adhesive layer 1140 can be made of an ultraviolet curable resin or a thermosetting resin.

  The antireflection layer 1150 prevents light incident from the transparent base material 1110 side from being reflected at the interface between the transparent base material 1110 and the adhesive layer 1140. Any antireflection layer 1150 may be used as long as it has general antireflection ability.

  In the first polarization separation element 1100, it is necessary that the S-polarized light is reflected by the dielectric multilayer film 1130 and the P-polarized light is transmitted through the light incident from the transparent substrate 1110 side. However, since the adhesive layer 1140 exists, the light incident from the transparent base material 1110 side may be reflected at the interface between the transparent base material 1110 and the adhesive layer 1140 depending on the refractive index of the adhesive layer 1140. . Therefore, by providing the antireflection layer 1150, the light incident from the transparent base material 1110 side is prevented from being reflected.

  The inventors diligently studied the optical path of the green light 2G incident on the first polarization separation element 1100 having the above structure. As a result, when the thickness of the dielectric multilayer film 1130 of the first polarization separation element 1100 becomes larger than the pixel pitch of the reflective display element, the present inventors use the dielectric multilayer film 1130 for green light 2G. It has been found that the position where the S-polarized light is reflected is divided into a plurality of positions. Specifically, the position where the S-polarized light of the green light 2G incident on the first polarization separation element 1100 is reflected is near the interface between the dielectric multilayer film 1130 and the transparent substrate 1120, and inside the dielectric multilayer film 1130. It was found that it was divided into multiple places. The reflection characteristics of the dielectric multilayer film 1130 vary depending on the wavelength and incident angle of incident light. Therefore, when the angle distribution of the incident angles is increased in order to improve the characteristics of the projection display device, it is considered that incident light having a part of the wavelength is reflected on the surface other than the surface of the dielectric multilayer film 1130.

  When the reflection position of the incident light is separated, the S-polarized light of the green light 2G incident on the first polarization separation element 1100 is divided into two reflected lights 2Gr and 2gr and emitted from the first polarization separation element 1100. . As a result, the green light 2G guided to the projection optical system 40 after being modulated for an image by the reflective display element is divided into two reflected lights 2Gr and 2gr. Or, the pixels are doubled.

  Accordingly, the present inventors have intensively studied to prevent the above-described decrease in resolution, and as a result, have come up with a technique according to the present disclosure. The technology according to the present disclosure prevents a decrease in resolution particularly in a high-resolution projection display device in which the pixel pitch of the reflective display element is 4 μm or less.

  Below, with reference to FIG. 3, the 1st polarization splitting element 11 used for the projection type display apparatus based on this embodiment based on the said knowledge is demonstrated. FIG. 3 is a schematic diagram illustrating the first polarization separation element 11 used in the projection display device according to the present embodiment.

  As illustrated in FIG. 3, the first polarization separation element 11 includes a pair of transparent base materials 111 and 112, a dielectric multilayer film 113 sandwiched between the pair of transparent base materials 111 and 112, an adhesive layer 114, and a reflection A prevention layer 115. In addition, the dielectric multilayer film 113 includes, for example, a green light reflection region 113G, a blue light reflection region 113B, and a red light reflection region 113R.

  The transparent base materials 111 and 112 have a substantially triangular prism-shaped prism structure, and are formed of a transparent glass material or resin material that can transmit incident light. Specifically, the transparent base materials 111 and 112 are preferably formed of a glass material that has high transparency to light having a wavelength in the visible light region and a small photoelastic constant. For example, the transparent substrates 111 and 112 are preferably formed of optical glass PBH56 manufactured by OHARA.

  The adhesive layer 114 is an adhesive layer that adheres the transparent substrate 112 on which the dielectric multilayer film 113 is formed and the transparent substrate 111 on which the antireflection layer 115 is formed. Specifically, the adhesive layer 1140 can be formed of an adhesive containing an ultraviolet curable resin or a thermosetting resin. For example, the adhesive layer 114 may be formed of an ultraviolet curable acrylate resin or epoxy resin, or a thermosetting epoxy resin or isocyanate resin.

  The antireflection layer 115 prevents light incident from the transparent substrate 111 side from being reflected at the interface between the transparent substrate 111 and the adhesive layer 114. The antireflection layer 115 may have any configuration as long as it has an antireflection ability. For example, the antireflection layer 115 may be a dielectric multilayer film having a general antireflection ability.

  The dielectric multilayer film 113 is a multilayer film in which dielectric materials having different refractive indexes are alternately stacked. Specifically, the dielectric multilayer film 113 can function as a reflective film by laminating a dielectric material having a high refractive index and a dielectric material having a low refractive index alternately. Further, when the incident angle of incident light is near the Brewster angle, the reflectivity of P-polarized light is 0. Therefore, the dielectric multilayer film 113 has a polarization separation function of transmitting P-polarized light and reflecting S-polarized light. Can fulfill.

  The dielectric multilayer film 113 can be formed using, for example, a high refractive index dielectric material such as titanium oxide or tantalum oxide and a low refractive index dielectric material such as silicon oxide. In addition, a dielectric material such as aluminum oxide having a refractive index in the middle of the above materials or M2 manufactured by Merck Ltd. may be used.

  In the projection display device 1 according to the present embodiment, the pixel pitch of the reflective display element is reduced for high resolution, and the dielectric polarization is improved in order to improve the polarization separation characteristic of the first polarization separation element 11. The film thickness of the body multilayer film 113 is large. Therefore, the dielectric multilayer film 113 is formed so that the entire film thickness is larger than the pixel pitch of the reflective display element.

  The dielectric multilayer film 113 is divided into a plurality of regions for each function. Specifically, the dielectric multilayer film 113 is formed by laminating a green light reflecting region that reflects the green light 2G and a region that reflects visible light (for example, the red light 2R and the blue light 2B) other than the green light 2G. Has a structure. For example, as shown in FIG. 3, the dielectric multilayer film 113 may have a structure in which a green light reflection region 113G, a blue light reflection region 113B, and a red light reflection region 113R are sequentially stacked from the transparent substrate 112 side. .

  The dielectric multilayer film 113 may have a structure in which a green light reflecting region that reflects green light 2G and a blue-red light reflecting region that reflects red light 2R and blue light 2B are stacked. In addition, the dielectric multilayer film 113 has a structure in which a green light reflecting region that reflects green light 2G and a red light reflecting region that reflects red light 2R are stacked, and the green light reflecting region receives blue light 1B. You may provide the function to reflect. The order of stacking the regions that reflect each color light in the dielectric multilayer film 113 is not particularly limited, but the green light reflection region 113G that reflects the green light 2G is to avoid scattering inside the dielectric multilayer film 113. It is preferable to be provided on the surface on the transparent base material 112 side on which the green light 2G enters.

  The green light reflection region 113G reflects the S-polarized light of the green light 2G incident from the transparent base material 112 side. Specifically, the green light reflection region 113G has a film thickness equal to or less than √2 / 2 times the pixel pitch of the green reflective display element 30G, and reflects the S-polarized light of the green light 2G. In such a case, the first polarization separation element 11 can reflect the S-polarized light of the incident green light 2G in a narrow film thickness range, and thus can prevent the reflected light from being divided into a plurality of parts. .

  Since the green light 2G enters the green light reflection region 113G at an incident angle centered at 45 degrees, for example, the S-polarized light of the green light 2G is approximately equal to or less than the pixel pitch in terms of the distance in the incident direction. It is reflected by. According to this, the green light reflection region 113G can reduce the expansion of one pixel of the green light 2G in the projection image to a pixel pitch or less. When the spread of one pixel of the reflected green light 2G is equal to or smaller than the pixel pitch, the first polarization separation element 11 can prevent a decrease in resolution because leakage to adjacent pixels is eliminated.

  Here, the film thickness of the green light reflection region 113G will be described more specifically with reference to FIG. FIG. 4 is an explanatory diagram in which the optical path of the green light 2G in the green light reflection region 113G is examined in more detail.

  As shown in FIG. 4, strictly speaking, the S-polarized light of the green light 2G that has entered the green light reflection region 113G is repeatedly refracted by each film of the dielectric multilayer film and then reflected to reflect the green light. The light is emitted from the region 113G. Therefore, in order to make the separation amount of the S-polarized light of the green light 2G reflected from the surface of the green-light reflecting area 113G and the S-polarized light of the green light 2G reflected inside the green-light reflecting area 113G equal to or less than the pixel pitch p. The film thickness of the green light reflecting region 113G may satisfy the following formula 1.

That is, since the incident angle of the green light 2G is 45 degrees, the dielectric multilayer film 113 until the S-polarized light of the green light 2G that enters the green light reflection region 113G is reflected by the green light reflection region 113G. The in-plane movement distance may be √2p / 2 or less with respect to the pixel pitch p. Accordingly, in the green light reflection region 113G formed of the N-layer multilayer film, the refraction angle of the green light 2G in the i-th multilayer film counting from the incident surface side of the green light 2G is θ _i , and the i-th multilayer film When the film thickness and t _i, the thickness of the green light reflection region 113G will satisfy the equation 1 below.

Θ _i in Equation 1 above satisfies the relationship of Equation 2 below from Snell's law. Therefore, by substituting 45 degrees into θ ₀ that is the incident angle to the dielectric multilayer film 113, θ _i can be obtained as shown in the following Expression 3.

  The film structure of the green light reflection region 113G is made of a material of each film so as to reflect S-polarized light incident near the Brewster angle in the wavelength region of green light 2G and transmit P-polarized light using simulation or the like. It is possible to design by optimizing the film thickness.

  The blue light reflection region 113B reflects the S-polarized light of the blue light 2B incident from the transparent substrate 111 side. The red light reflecting region 113R reflects the S-polarized light of the red light 2R that has entered from the transparent base material 111 side.

  Here, the S-polarized light of the blue light 2B and the red light 2R reflected by the blue light reflection region 113B and the red light reflection region 113R is light that is not guided to the projection optical system 40. Therefore, there is no particular problem even if the reflection positions of the S-polarized light of the blue light 2B and the red light 2R reflected by the blue light reflection region 113B and the red light reflection region 113R are divided into a plurality of portions. Therefore, the film thicknesses of the blue light reflection region 113B and the red light reflection region 113R are not particularly limited, and are optimized using simulation or the like so that the reflectance of the S-polarized light incident near the Brewster angle becomes higher. Any film thickness may be used.

  As described above, according to the first polarization separation element 11 according to this embodiment, the S-polarized light of the green light 2G is reflected at different reflection positions, so that the pixels are doubled in the projection image. It is possible to prevent separation and to prevent the resolution of the projection display device from being lowered. Specifically, according to the first polarization separation element 11, as shown in FIG. 5A, when a cross hatch image is displayed on the projection surface in the projection display device, the image is blurred or doubled. It is possible to obtain an image that has not become.

  Therefore, according to the projection display device according to the present embodiment, it is possible to prevent a decrease in resolution when a pixel pitch of the reflective display element is narrow and a high-definition image is projected. In addition, the pixel pitch of the reflection type display element with which the projection type display apparatus which concerns on this embodiment is provided is 4 micrometers or less, for example.

<2. Second Embodiment>
Next, a projection display device according to the second embodiment of the present disclosure will be described with reference to FIGS. 6 to 9B.

  Unlike the first embodiment shown in FIG. 1, the projection display device according to the present embodiment is not the first polarization separation element 11 but the second polarization separation element 12 and the S-polarized light of the red light 2R. This prevents the reflection position from being separated. In addition, since the whole structure of the projection type display apparatus which concerns on 2nd Embodiment is the same as that of the projection type display apparatus 1 which concerns on 1st Embodiment demonstrated in FIG. 1, description here is abbreviate | omitted.

[2.1. Configuration of polarization separation element]
First, the background of the present embodiment will be described with reference to FIG. FIG. 6 is an explanatory diagram for explaining the reason why the resolution decreases in the second polarization separation element.

  As for the projection display device according to the second embodiment, the present inventors have made extensive developments in order to improve the resolution. As in the first embodiment, the pixel pitch of the reflective display element is also improved. It has been found that the resolution of the image displayed on the projection surface is lower than expected when is extremely narrow (for example, 4 μm or less).

  Specifically, as shown in FIG. 9B, the present inventors display a cross hatch image on the projection surface in the projection display device, and some lines are displayed twice. I found. In such a case, since the image of the pixel displayed doubly affects the image of the adjacent pixel, the resolution of the projection display device is lowered. This is because, as in the first embodiment, the reflection position of the S-polarized light incident on the second polarization separation element is divided into a plurality of positions. This point will be described more specifically with reference to FIG.

  As shown in FIG. 6, the second polarization separation element 1200 includes a pair of transparent base materials 1210 and 1220, a dielectric multilayer film 1230 sandwiched between the pair of transparent base materials 1210 and 1220, an adhesive layer 1240, and a reflective layer. A prevention layer 1250.

  The transparent base materials 1210 and 1220 are substantially the same as the transparent base materials 1110 and 1120, the dielectric multilayer film 1230 is substantially the same as the dielectric multilayer film 1130, and the adhesive layer 1240 is the same as the adhesive layer 1140. Since the antireflection layer 1250 is substantially the same as the antireflection layer 1150, a detailed description thereof is omitted here.

  The present inventors have also intensively studied the optical path of light incident on the second polarization separation element 1200. As a result, when the thickness of the dielectric multilayer film 1230 of the second polarization separation element 1200 is larger than the pixel pitch of the reflective display element, the S-polarized light of the red light 2R is reflected by the dielectric multilayer film 1230. It was found that the position to be divided into multiple.

  Specifically, when the reflection position of the incident light is separated, the S-polarized light of the red light 2R incident on the second polarization separation element 1200 is divided into two reflected lights 2Rr and 2rr, and the second polarization separation element It is emitted from 1200. As a result, the red light 2R guided to the projection optical system 40 after being modulated for an image by the reflective display element is divided into two reflected lights 2Rr and 2rr, so that the pixel is blurred on the projection surface 50. Or, the pixels are doubled.

  Therefore, in the projection display device according to the second embodiment, as in the first embodiment, the second polarization separation element 12 is configured so that the reflection position of the incident red light 2R is not divided. Therefore, it is possible to prevent a decrease in resolution.

  Below, with reference to FIG. 7, the 2nd polarization separation element 12 used for the projection type display apparatus which concerns on this embodiment is demonstrated. FIG. 7 is a schematic diagram illustrating the second polarization separation element 12 used in the projection display device according to the present embodiment.

  As shown in FIG. 7, the second polarization separation element 12 includes a pair of transparent base materials 121 and 122, a dielectric multilayer film 123 sandwiched between the pair of transparent base materials 121 and 122, an adhesive layer 124, and a reflection A prevention layer 125. In addition, the dielectric multilayer film 123 includes, for example, a blue light reflection region 123B and a red light reflection region 123R.

  The transparent base materials 121 and 122 are substantially the same as the transparent base materials 111 and 112, the adhesive layer 124 is substantially the same as the adhesive layer 114, and the antireflection layer 125 is substantially the same as the antireflection layer 115. The detailed description here will be omitted.

  Similar to the dielectric multilayer film 113 described in the first embodiment, the dielectric multilayer film 123 is a multilayer film in which dielectric materials having different refractive indexes are alternately stacked. The dielectric multilayer film 123 can be formed of the same dielectric material as the dielectric multilayer film 113 described in the first embodiment. The dielectric multilayer film 123 is formed with a film thickness larger than the pixel pitch of the reflective display element in order to improve the polarization separation characteristic.

  Here, the dielectric multilayer film 123 is divided into a plurality of regions for each function. Specifically, the dielectric multilayer film 123 has a structure in which a red light reflecting region that reflects red light 2R and a region that reflects visible light (for example, blue light 2B) other than the red light 2R are stacked. . For example, as shown in FIG. 7, the dielectric multilayer film 123 may have a structure in which a blue light reflection region 123B and a red light reflection region 123R are sequentially stacked from the transparent base material 122 side. The stacking order of the blue light reflection region 123B and the red light reflection region 123R in the dielectric multilayer film 123 is not particularly limited, but the red light reflection region 123R that reflects the red light 2R is within the dielectric multilayer film 123. In order to avoid scattering, it is preferable to be provided on the surface of the transparent substrate 121 side on which the red light 2R is incident.

  The red light reflection region 123R reflects the S-polarized light of the red light 2R incident from the transparent base material 121 side. Specifically, the red light reflection region 123R has a film thickness equal to or less than √2 / 2 times the pixel pitch of the red reflective display element 30R, and reflects the S-polarized light of the red light 2R. In such a case, since the second polarization separation element 12 can reflect the S-polarized light of the incident red light 2R in a narrow film thickness range, it is possible to prevent the reflected light from being divided into a plurality of parts. .

  Since the red light 2R is incident on the red light reflection region 123R at an incident angle centered at 45 degrees, for example, the S-polarized light of the red light 2R is approximately equal to or less than the pixel pitch in terms of the distance in the incident direction. Will be reflected. According to this, the red light reflection region 123R can reduce the expansion of one pixel of the red light 2R in the projection image to a pixel pitch or less. When the spread of one pixel of the reflected red light 2R is equal to or smaller than the pixel pitch, the second polarization separation element 12 can prevent a decrease in resolution because leakage to adjacent pixels is eliminated.

  Here, the film thickness of the red light reflection region 123R will be described more specifically with reference to FIG. FIG. 8 is an explanatory diagram in which the optical path of the red light 2R in the red light reflection region 123R is examined in more detail.

As shown in FIG. 8, strictly speaking, the S-polarized light of the red light 2R that has entered the red light reflecting region 123R is repeatedly refracted by each film of the dielectric multilayer film and then reflected to reflect the red light. The light is emitted from the region 123R.
Therefore, in order to make the separation amount between the S-polarized light of the red light 2R reflected by the surface of the red light reflecting region 123R and the S-polarized light of the red light 2R reflected inside the red light reflecting region 123R less than the pixel pitch p. The film thickness of the red light reflection region 123R satisfies the following expression 1 similarly to the green light reflection region 113G in the first embodiment.

Θ _i in Equation 1 above satisfies the relationship of Equation 2 below from Snell's law. Therefore, by substituting 45 degrees into θ ₀ that is the angle of incidence on the dielectric multilayer film 123, θ _i can be obtained as shown in Equation 3 below.

  The film structure of the red light reflection region 123R is made of a material of each film so as to reflect S-polarized light incident near the Brewster angle and transmit P-polarized light in the wavelength region of the red light 2R using simulation or the like. It is possible to design by optimizing the film thickness.

  The blue light reflection region 123B reflects the S-polarized light of the blue light 2B incident from the transparent base material 122 side. Here, the S-polarized light of the blue light 2B reflected by the blue light reflection region 123B is light incident on the blue reflective display element 30B and is light before being modulated for a blue image. Therefore, there is no particular problem even if the reflection position of the S-polarized light of the blue light 2B reflected by the blue light reflection region 123B is divided into a plurality of positions. Accordingly, the film thickness of the blue light reflection region 123B is not particularly limited as long as it is optimized using simulation or the like so that the reflectance of the S-polarized light incident near the Brewster angle becomes higher. Good.

  As described above, according to the second polarization separation element 12 according to the present embodiment, the S-polarized light of the red light 2R is reflected at different reflection positions, so that the pixels are doubled in the projection image. It is possible to prevent separation and to prevent the resolution of the projection display device from being lowered. Specifically, according to the second polarization separation element 12, as in the first embodiment, as shown in FIG. 9A, when a cross-hatch image is displayed on the projection surface in the projection display device. It is possible to obtain an image that is not blurred or doubled.

  Therefore, according to the projection display device according to the present embodiment, as in the first embodiment, the pixel pitch of the reflective display element is narrow, and when a high-definition image is projected, a reduction in resolution is prevented. It is possible. In addition, the pixel pitch of the reflection type display element with which the projection type display apparatus which concerns on this embodiment is provided is 4 micrometers or less, for example.

<3. Summary>
As described above, the projection display device according to each embodiment of the present disclosure can prevent a decrease in resolution that occurs when a reflective display element with a narrow pixel pitch is used for higher resolution. Is possible.

  In addition, the technology according to the present disclosure can be implemented by combining the first embodiment and the second embodiment. Specifically, each of the first polarization separation element 11 and the second polarization separation element 12 includes a dielectric multilayer film having an overall film thickness larger than the pixel pitch of the reflective display element, and the dielectric of each polarization separation element. The body multilayer film may reflect light from the reflective display element in a region having a film thickness equal to or less than √2 / 2 times the pixel pitch of the reflective display element. In such a case, each of the first polarization separation element 11 and the second polarization separation element 12 can prevent the reflected light from being divided into a plurality of parts, so that the resolution of the projection display device is reduced. More can be prevented.

  The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

  Further, the effects described in the present specification are merely illustrative or exemplary and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
At least one reflective display element;
A polarization separation element that reflects light from the reflective display element;
A projection optical system for projecting the light reflected by the polarization separation element;
With
The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates,
The total thickness of the dielectric multilayer film is larger than the pixel pitch of the reflective display element,
The projection display device, wherein a film thickness of a region that reflects light in a predetermined wavelength region in the dielectric multilayer film is not more than √2 / 2 times the pixel pitch.
(2)
The polarization separation element reflects S-polarized light out of the green light from the green reflective display element and guides it to the projection optical system,
The polarization separation element reflects S-polarized light out of red light and blue light incident on the dielectric multilayer film from a surface facing the surface on which the green light is incident, and guides the light out of the projection optical system. The projection display device according to (1), wherein polarized light is transmitted and guided to the projection optical system.
(3)
In the dielectric multilayer film, a region that reflects green light, a region that reflects blue light, and a region that reflects red light are laminated in any order.
The projection display device according to (2), wherein a film thickness of the region that reflects the green light is equal to or less than √2 / 2 times the pixel pitch.
(4)
The polarization separation element reflects S-polarized light out of red light from the red reflective display element and guides it to the projection optical system,
The polarization separation element reflects S-polarized light out of blue light incident on the dielectric multilayer film from a surface facing the surface on which the red light is incident, and guides it to a blue reflective display device. The projection display device according to (1), wherein P-polarized light from the reflective display element is transmitted and guided to the projection optical system.
(5)
In the dielectric multilayer film, a region that reflects red light and a region that reflects blue light are laminated in an arbitrary order,
The projection display device according to (4), wherein a film thickness of the region that reflects the red light is equal to or less than √2 / 2 times the pixel pitch.
(6)
The projection display device includes a plurality of the polarization separation elements,
Each of the polarization separation elements reflects light from each of the reflective display elements in a region having a film thickness equal to or less than √2 / 2 times the pixel pitch in the dielectric multilayer film. The projection type display device described in 1.
(7)
The projection display device according to any one of (1) to (6), wherein the pixel pitch is 4 μm or less.
(8)
The projection display device according to any one of (1) to (7), wherein the dielectric multilayer film is a multilayer film in which a plurality of dielectrics having different refractive indexes are alternately stacked.
(9)
The said transparent base material is a projection type display apparatus as described in any one of said (1)-(8) which is a triangular prism-shaped glass prism.
(10)
At least one reflective display element;
A polarization separation element that reflects light from the reflective display element;
A projection optical system for projecting the light reflected by the polarization separation element;
With
The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates,
The total thickness of the dielectric multilayer film is larger than the pixel pitch p of the reflective display element,
Of the dielectric multilayer film, a region that reflects light in a predetermined wavelength region is composed of an N-layer multilayer film,
When the refractive angle of light of the predetermined wavelength region in the i-th multilayer film counted from the light incident surface of the predetermined wavelength region is θ _i and the film thickness of the i-th multilayer film is t _i , the dielectric The multilayer film satisfies the following formula 1 and is a projection display device.

DESCRIPTION OF SYMBOLS 1 Projection type display apparatus 2B Blue light 2G Green light 2R Red light 2Y Yellow light 11 1st polarization separation element 12 2nd polarization separation element 13 3rd polarization separation element 20 Light source 30B Blue reflective display element 30G For green Reflective display element 30R Reflective display element for red 40 Projection optical system 111, 112, 121, 122 Transparent base material 113, 123 Dielectric multilayer film 114, 124 Adhesive layer 115, 125 Antireflection layer

Claims (10)

At least one reflective display element;
A polarization separation element that reflects light from the reflective display element;
A projection optical system for projecting the light reflected by the polarization separation element;
With
The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates,
The total thickness of the dielectric multilayer film is larger than the pixel pitch of the reflective display element,
The projection display device, wherein a film thickness of a region that reflects light in a predetermined wavelength region in the dielectric multilayer film is not more than √2 / 2 times the pixel pitch. The polarization separation element reflects S-polarized light out of the green light from the green reflective display element and guides it to the projection optical system,
The polarization separation element reflects S-polarized light out of red light and blue light incident on the dielectric multilayer film from a surface facing the surface on which the green light is incident, and guides the light out of the projection optical system. The projection display device according to claim 1, wherein the projection display device transmits polarized light and guides the polarized light to the projection optical system. In the dielectric multilayer film, a region that reflects green light, a region that reflects blue light, and a region that reflects red light are laminated in any order.
The projection display device according to claim 2, wherein a film thickness of the region that reflects the green light is equal to or less than √2 / 2 times the pixel pitch. The polarization separation element reflects S-polarized light out of red light from the red reflective display element and guides it to the projection optical system,
The polarization separation element reflects S-polarized light out of blue light incident on the dielectric multilayer film from a surface facing the surface on which the red light is incident, and guides it to a blue reflective display device. The projection display device according to claim 1, wherein P-polarized light from the reflective display element is transmitted and guided to the projection optical system. In the dielectric multilayer film, a region that reflects red light and a region that reflects blue light are laminated in an arbitrary order,
The projection display device according to claim 4, wherein a film thickness of the region that reflects the red light is equal to or less than √2 / 2 times the pixel pitch. The projection display device includes a plurality of the polarization separation elements,
Each of the said polarization separation elements reflects the light from each of the said reflection type display elements in the area | region of the film thickness below 2/2 times of the said pixel pitch among the said dielectric multilayer films. The projection type display device described.   The projection display device according to claim 1, wherein the pixel pitch is 4 μm or less.   The projection display device according to claim 1, wherein the dielectric multilayer film is a multilayer film in which a plurality of dielectrics having different refractive indexes are alternately stacked.   The projection display device according to claim 1, wherein the transparent substrate is a triangular prism-shaped glass prism. At least one reflective display element;
A polarization separation element that reflects light from the reflective display element;
A projection optical system for projecting the light reflected by the polarization separation element;
With
The polarization separation element includes a dielectric multilayer film disposed between a pair of transparent substrates,
The total thickness of the dielectric multilayer film is larger than the pixel pitch p of the reflective display element,
Of the dielectric multilayer film, a region that reflects light in a predetermined wavelength region is composed of an N-layer multilayer film,
When the refractive angle of light of the predetermined wavelength region in the i-th multilayer film counted from the light incident surface of the predetermined wavelength region is θ _i and the film thickness of the i-th multilayer film is t _i , the dielectric The multilayer film satisfies the following formula 1 and is a projection display device.