Indication device

Abstract

Suppresses the decrease in image visibility. [Solution] According to one embodiment, the display device comprises a transparent substrate having a first main surface and a second main surface, a display element facing the first main surface, a first optical element facing the display element via the transparent substrate and positioned on the second main surface, configured to reflect the display light transmitted through the transparent substrate, and a second optical element spaced apart from the first optical element and positioned on the second main surface, configured to reflect the display light propagated through the interior of the transparent substrate, wherein each of the first optical element and the second optical element comprises a first liquid crystal layer including a first cholesteric liquid crystal and a second liquid crystal layer including a second cholesteric liquid crystal swirled in the opposite direction to the first cholesteric liquid crystal, wherein in the first optical element, the second liquid crystal layer overlaps the first liquid crystal layer, and in the second optical element, the first liquid crystal layer and the second liquid crystal layer are aligned on the second main surface.

Description

【Technical Field】 【0001】 Embodiments of the present invention relate to a display device. 【Background Art】 【0002】 In recent years, head-mounted displays using a holographic optical element (hereinafter sometimes simply referred to as HOE) that diffracts display light from a display element and a light guide member have been variously studied. In one example, a technique of providing a holographic diffraction optical element on each surface of a light guide member is known. The HOE disposed on one surface of the light guide member diffracts the display light so as to be totally reflected by the light guide member, and the HOE disposed on the other surface of the light guide member diffracts the display light propagating inside the light guide member so as to be emitted to the outside. In such a head-mounted display, when the observation area where an image is displayed is narrow, the position of the user's eyes and the observation area are likely to be mismatched. In this case, the visibility of the image for the user is reduced. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2007-219106 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 An object of an embodiment is to provide a display device capable of suppressing a reduction in visibility of an image. 【Means for Solving the Problems】 【0005】 According to one embodiment, a display device includes The present invention comprises a transparent substrate having a first main surface and a second main surface opposite to the first main surface; a display element facing the first main surface and configured to emit display light toward the transparent substrate; a first optical element facing the display element via the transparent substrate and positioned on the second main surface, configured to reflect the display light transmitted through the transparent substrate; and a second optical element spaced apart from the first optical element and positioned on the second main surface, configured to reflect the display light propagated through the interior of the transparent substrate, wherein each of the first and second optical elements comprises a first liquid crystal layer including a first cholesteric liquid crystal and a second liquid crystal layer including a second cholesteric liquid crystal swirled in the opposite direction to the first cholesteric liquid crystal, wherein in the first optical element, the second liquid crystal layer overlaps the first liquid crystal layer, and in the second optical element, the first and second liquid crystal layers are aligned toward the second main surface. [Brief explanation of the drawing] 【0006】 [Figure 1] Figure 1 shows an example configuration of a display device DSP. [Figure 2] Figure 2 is a diagram illustrating the first optical element 10 of the display device DSP shown in Figure 1. [Figure 3] Figure 3 is a diagram illustrating the liquid crystal layer 21 of the second optical element 20 of the display device DSP shown in Figure 1. [Figure 4] Figure 4 is a diagram illustrating the liquid crystal layer 22 of the second optical element 20 of the display device DSP shown in Figure 1. [Figure 5] Figure 5 is a diagram illustrating the reflective surfaces 11R and 12R in the first optical element 10 shown in Figure 1. [Figure 6] Figure 6 is a cross-sectional view illustrating an example of cholesteric liquid crystal CL1 contained in the liquid crystal layer 11 and cholesteric liquid crystal CL2 contained in the liquid crystal layer 12 shown in Figure 5. [Figure 7] Figure 7 is a schematic plan view showing the liquid crystal layer 11 shown in Figure 5. [Figure 8] Figure 8 is a schematic plan view showing the liquid crystal layer 12 shown in Figure 5. [Figure 9] Figure 9 is a diagram illustrating the reflective surfaces 21R and 22R in the second optical element 20 shown in Figure 1. [Figure 10] Figure 10 is a plan view showing an example of image display in the DSP display device shown in Figure 1. [Figure 11] Figure 11 shows another example of a DSP display device configuration. [Figure 12] Figure 12 is a diagram illustrating the liquid crystal layer 211 and liquid crystal layer 212 of the display device DSP shown in Figure 11. [Figure 13] Figure 13 is a diagram illustrating the liquid crystal layer 221 and liquid crystal layer 222 of the display device DSP shown in Figure 11. [Figure 14] Figure 14 is a plan view showing an example of image display in the DSP display device shown in Figure 11. [Figure 15] Figure 15 shows another example of a DSP display device configuration. [Figure 16] Figure 16 is a diagram illustrating the reflective surfaces 11R and 12R in the first optical element 10 shown in Figure 15. [Figure 17] Figure 17 is a diagram illustrating the reflective surfaces 21R and 22R in the second optical element 20 shown in Figure 15. [Figure 18] Figure 18 is a plan view showing an example of image display in the DSP display device shown in Figure 15. [Figure 19] Figure 19 shows another example of a display device DSP configuration. [Figure 20] Figure 20 is a plan view showing an example of image display in the DSP display device shown in Figure 19. [Figure 21] Figure 21 shows another example of a DSP display device configuration. [Figure 22] Figure 22 is a diagram illustrating the first optical element 10 of the display device DSP shown in Figure 21. [Figure 23] Figure 23 is a diagram illustrating the first stacked layer 20A of the display device DSP shown in Figure 21. [Figure 24]FIG. 24 is a diagram for explaining the second laminate 20B of the display device DSP shown in FIG. 21. 【Embodiments for Carrying Out the Invention】 【0007】 Hereinafter, embodiments will be described with reference to the drawings. The disclosure is merely an example, and for those that can be easily conceived by those skilled in the art for appropriate modifications while maintaining the gist of the disclosure, they are naturally included in the scope of the present disclosure. In addition, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but it is merely an example and does not limit the interpretation of the present disclosure. Also, in this specification and each figure, components that exhibit the same or similar functions as those described above with respect to the already shown figures may be assigned the same reference numerals, and detailed descriptions that overlap may be appropriately omitted. 【0008】 Note that in the drawings, for ease of understanding as necessary, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are described. The direction along the X-axis is referred to as the first direction X, the direction along the Y-axis is referred to as the second direction Y, and the direction along the Z-axis is referred to as the third direction Z. The plane defined by the first direction X and the second direction Y is referred to as the X-Y plane, the plane defined by the second direction Y and the third direction Z is referred to as the Y-Z plane, and the plane defined by the first direction X and the third direction Z is referred to as the X-Z plane. Looking at various elements parallel to the third direction Z is referred to as a plan view. Note that terms indicating the positional relationship between two or more components such as above, upper, between, and facing include not only the case where the two or more target components are in direct contact, but also the case where they are separated from each other by a gap or other components in between. 【0009】 FIG. 1 is a diagram showing a configuration example of the display device DSP. 【0010】 The display device DSP includes a display module DM and a liquid crystal optical element 100. The liquid crystal optical element 100 includes a transparent substrate 1, a first optical element 10, and a second optical element 20. The display module DM includes a display element 2 and an optical system 3. 【0011】 The transparent substrate 1 is, for example, a glass substrate, but may also be a resin substrate. The transparent substrate 1 is formed in a flat plate shape and has a first main surface 1A and a second main surface 1B opposite to the first main surface 1A. The first main surface 1A and the second main surface 1B are planes substantially parallel to the XY plane and are opposite each other in a third direction Z. For example, each of the first main surface 1A and the second main surface 1B is formed in a rectangular shape with a pair of long sides extending in the first direction X and a pair of short sides extending in the second direction Y. The third direction Z corresponds to the thickness direction of the transparent substrate 1. 【0012】 The display element 2 is positioned on the side of the transparent substrate 1 facing the first main surface 1A in the third direction Z, and is configured to emit display light DL toward the transparent substrate 1. Such a display element 2 may be, for example, a display element equipped with a self-emissive element such as an organic electroluminescent element or a light-emitting diode, or it may be a display element that combines an optical switch such as a liquid crystal panel with an illumination device. 【0013】 The optical system 3 is positioned between the display element 2 and the transparent substrate 1 in the third direction Z. Such an optical system 3 includes at least one lens and is configured to collimate the divergent display light DL emitted from the display element 2. 【0014】 The first optical element 10 faces the display element 2 via the transparent substrate 1 in the third direction Z and is positioned on the second main surface 1B. In other words, the transparent substrate 1 is located between the display element 2 and the first optical element 10 in the third direction Z. In one example, the first optical element 10 is bonded to the transparent substrate 1. Such a first optical element 10 is configured to reflect the display light DL that has passed through the transparent substrate 1. The angle at which the display light DL is reflected by the first optical element 10 is set so that the display light DL undergoes total internal reflection within the transparent substrate 1. 【0015】 The second optical element 20 is spaced apart from the first optical element 10, faces the user's eye E in the third direction Z, and is positioned on the second main surface 1B. The first optical element 10 and the second optical element 20 are spaced apart in the first direction X. In one example, the second optical element 20 is bonded to the transparent substrate 1. Such a second optical element 20 is configured to reflect the display light DL propagated inside the transparent substrate 1. The angle at which the display light DL is reflected in the second optical element 20 is set so that the display light DL is emitted almost perpendicularly from the first main surface 1A. The reflection in the first optical element 10 and the second optical element 20 involves diffraction within each of the first optical element 10 and the second optical element 20, respectively. 【0016】 Each of the first optical element 10 and the second optical element 20 is, in one example, composed of a liquid crystal layer including a cholesteric liquid crystal, but may also be a diffracting element such as a holographic optical element (HOE) that diffracts incident light at a predetermined diffraction angle. 【0017】 The first optical element 10 comprises a liquid crystal layer 11 and a liquid crystal layer 12. The liquid crystal layer 11 is located on the second main surface 1B, and the liquid crystal layer 12 overlaps the liquid crystal layer 11. In other words, the first optical element 10 is configured as a laminate of multiple liquid crystal layers. 【0018】 The second optical element 20 comprises a liquid crystal layer 21 and a liquid crystal layer 22. The liquid crystal layers 21 and 22 are arranged on the second main surface 1B and aligned in the second direction Y. The liquid crystal layers 11, 12, 21, and 22 contain cholesteric liquid crystals, which will be described in detail later. 【0019】 Figure 2 is a diagram illustrating the first optical element 10 of the display device DSP shown in Figure 1. 【0020】 The liquid crystal layer 11 contains cholesteric liquid crystal CL1, as shown schematically in an enlarged view. The cholesteric liquid crystal CL1 has a helical pitch P1 along the third direction Z. The helical pitch represents one period of the helix (the layer thickness along the third direction Z required for the liquid crystal molecules to rotate 360 ​​degrees). 【0021】 The liquid crystal layer 12, as shown schematically in magnified view, contains a cholesteric liquid crystal CL2 that is spiraled in the opposite direction to the cholesteric liquid crystal CL1. The cholesteric liquid crystal CL2 has a helical pitch P2 along the third direction Z. The helical pitch P2 is equivalent to the helical pitch P1. 【0022】 Each of these liquid crystal layers 11 and 12 is configured to reflect circularly polarized light in a selective reflection band determined according to the helical pitch P and the refractive index anisotropy Δn of the liquid crystal film. 【0023】 The liquid crystal layer 11 has a reflective surface 11R that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL1 within the selective reflection band. The liquid crystal layer 12 has a reflective surface 12R that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL2 within the selective reflection band. Both the reflective surface 11R and the reflective surface 12R are inclined with respect to the XY plane. In this specification, circularly polarized light may be strictly circularly polarized light or circularly polarized light that approximates elliptical polarization. 【0024】 For example, let's consider the case where display light DL having a random polarization state is incident on liquid crystal layers 11 and 12. Liquid crystal layer 11 reflects light LT1, which is part of the display light DL, at its reflective surface 11R. Liquid crystal layer 12 also reflects light LT2, which is another part of the display light DL, at its reflective surface 12R. As described above, since the helical pitch P1 is equal to the helical pitch P2, light LT1 and light LT2 are light in the same wavelength band λ1. Furthermore, since the rotation direction of cholesteric liquid crystal CL1 and cholesteric liquid crystal CL2 are different from each other, light LT1 and light LT2 are circularly polarized in opposite directions. For example, light LT1 is clockwise circularly polarized λ1a, and light LT2 is counterclockwise circularly polarized λ1b. 【0025】 Each of the light rays LT1 and LT2 propagates through the transparent substrate 1, undergoing total internal reflection at the first main surface 1A and the second main surface 1B. As shown in Figure 1, each of the light rays LT1 and LT2 propagates in directions different from the first direction X and the second direction Y. More specifically, the light LT1 reflected by the liquid crystal layer 11 propagates toward the liquid crystal layer 21 of the second optical element 20. Similarly, the light LT2 reflected by the liquid crystal layer 12 propagates toward the liquid crystal layer 22 of the second optical element 20. 【0026】 In the third direction Z, the liquid crystal layer 11 has a thickness T11, and the liquid crystal layer 12 has a thickness T12. If diffraction efficiency is defined as the ratio of the intensity of reflected light (first-order diffracted light) in the liquid crystal layer to the intensity of incident light into the liquid crystal layer, then from the viewpoint of improving the diffraction efficiency in liquid crystal layer 11 and liquid crystal layer 12, it is desirable that the thicknesses T11 and T12, respectively, be several times to about 10 times the helical pitch. In one example, the thicknesses T11 and T12 are equivalent, and are approximately 3 μm. Furthermore, the diffraction efficiency of liquid crystal layer 12 is equivalent to the diffraction efficiency of liquid crystal layer 11. 【0027】 Figure 3 is a diagram illustrating the liquid crystal layer 21 of the second optical element 20 of the display device DSP shown in Figure 1. 【0028】 The liquid crystal layer 21 includes a cholesteric liquid crystal CL1, as shown schematically in an enlarged view. The cholesteric liquid crystal CL1 has a helical pitch P1 along the third direction Z. In other words, the liquid crystal layer 21 has the same configuration as the liquid crystal layer 11. The liquid crystal layer 21 has a reflective surface 21R that reflects circularly polarized light (e.g., right-handed circularly polarized light) corresponding to the rotation direction of the cholesteric liquid crystal CL1 within the selective reflection band. The reflective surface 21R is inclined with respect to the XY plane. Such a liquid crystal layer 21 is configured to reflect light LT1 along the normal to the second principal surface 1B. 【0029】 When the user's eye E faces the liquid crystal layer 21 in the third direction Z, the user can see the light LT1 reflected by the liquid crystal layer 21. The user can also see ambient light LTa through the liquid crystal layer 21. 【0030】 The liquid crystal layer 21 has a thickness T21 in the third direction Z. When the display device DSP is applied to an application that provides augmented reality, it is required to ensure sufficient transmittance of the liquid crystal layer 21. For this reason, it is desirable that the diffraction efficiency of the liquid crystal layer 21 in the second optical element 20 is smaller than the diffraction efficiency of the liquid crystal layer 11 in the first optical element 10. In other words, it is desirable that the liquid crystal layer 21 is thinner than the liquid crystal layer 11. To put it another way, it is desirable that the thickness T21 is smaller than the thickness T11. In one example, the thickness T21 is approximately 1 μm to 2 μm. 【0031】 Figure 4 is a diagram illustrating the liquid crystal layer 22 of the second optical element 20 of the display device DSP shown in Figure 1. 【0032】 The liquid crystal layer 22 includes a cholesteric liquid crystal CL2, as shown schematically in an enlarged view. The cholesteric liquid crystal CL2 has a helical pitch P2 along the third direction Z. In other words, the liquid crystal layer 22 has the same configuration as the liquid crystal layer 12. The liquid crystal layer 22 has a reflective surface 22R that reflects circularly polarized light (e.g., left-handed circularly polarized light) corresponding to the rotation direction of the cholesteric liquid crystal CL2 within the selective reflection band. The reflective surface 22R is inclined with respect to the XY plane. Such a liquid crystal layer 22 is configured to reflect light LT2 along the normal to the second principal surface 1B. 【0033】 When the user's eye E faces the liquid crystal layer 22 in the third direction Z, the user can see the light LT2 reflected by the liquid crystal layer 22. The user can also see ambient light LTa through the liquid crystal layer 22. 【0034】 The liquid crystal layer 22 has a thickness T22 in the third direction Z. In order to ensure sufficient transmittance of the liquid crystal layer 22, it is desirable that the diffraction efficiency of the liquid crystal layer 22 in the second optical element 20 is smaller than the diffraction efficiency of the liquid crystal layer 12 in the first optical element 10. In other words, it is desirable that the liquid crystal layer 22 is thinner than the liquid crystal layer 12. To put it another way, it is desirable that the thickness T22 is smaller than the thickness T12. In one example, the thickness T22 is approximately 1 μm to 2 μm. Furthermore, the diffraction efficiency of the liquid crystal layer 22 is equivalent to that of the liquid crystal layer 21, and the thickness T22 is equivalent to that of the thickness T21. 【0035】 Figure 5 is a diagram illustrating the reflective surfaces 11R and 12R in the first optical element 10 shown in Figure 1. 【0036】 Each of the reflective surfaces 11R and 12R is inclined with respect to a second principal surface 1B that is parallel to the XY plane. Furthermore, each of the reflective surfaces 11R and 12R is also inclined with respect to the XZ plane and the YZ plane. Moreover, the reflective surfaces 11R and 12R are non-parallel to each other. 【0037】 The line of intersection between the reflective surface 11R and the XY plane is parallel to direction D11 and intersects with the first direction X and the second direction Y. In the XZ plane, the angle θ1 between the reflective surface 11R and the XY plane is acute. The indicator light DL traveling along the third direction Z is reflected by the reflective surface 11R along direction D12, which is perpendicular to direction D11. In other words, the direction of propagation of the light LT1 reflected by the reflective surface 11R is parallel to direction D12 in the XY plane, unlike the first direction X and the second direction Y. 【0038】 The line of intersection between the reflective surface 12R and the XY plane is parallel to direction D21, intersects with the first direction X and the second direction Y, and also intersects with direction D11. In the XZ plane, the angle θ2 between the reflective surface 12R and the XY plane is acute. In one example, angle θ2 is equivalent to angle θ1, but it may be different from angle θ1. The indicator light DL traveling along the third direction Z is reflected by the reflective surface 12R along direction D22, which is perpendicular to direction D21. That is, the direction of propagation of the light LT2 reflected by the reflective surface 12R is different from the first direction X and the second direction Y in the XY plane, and is parallel to direction D22. 【0039】 Next, the configurations of the liquid crystal layer 11 and the liquid crystal layer 12 will be described. 【0040】 Figure 6 is a cross-sectional view illustrating an example of cholesteric liquid crystal CL1 contained in the liquid crystal layer 11 and cholesteric liquid crystal CL2 contained in the liquid crystal layer 12 shown in Figure 5. 【0041】 Focusing on one cholesteric liquid crystal CL1 enclosed by a dashed line in the liquid crystal layer 11, we see that the cholesteric liquid crystal CL1 is composed of multiple liquid crystal molecules LM1 that are spirally stacked along the third direction Z while rotating. For simplicity, the liquid crystal molecule LM1 constituting the cholesteric liquid crystal CL1 is shown as one of multiple liquid crystal molecules located in the same plane parallel to the XY plane. The orientation direction of the shown liquid crystal molecule LM1 corresponds to the average orientation direction of multiple liquid crystal molecules located in the same plane. 【0042】 In the illustrated XZ cross-section, the orientation directions of multiple adjacent cholesteric liquid crystals CL1 along the first direction X are different from each other. In multiple adjacent cholesteric liquid crystals CL1 along the first direction X, the orientation directions of liquid crystal molecules LM11 located on the same plane are different from each other. 【0043】 The reflective surface 11R, shown by the dashed line in the figure, corresponds to a surface where the orientation direction of the liquid crystal molecules LM1 is aligned, or a surface where the spatial phase is aligned (equal phase surface). 【0044】 In the liquid crystal layer 12, focusing on one cholesteric liquid crystal CL2 enclosed by a dashed line, we see that the cholesteric liquid crystal CL2 is composed of multiple liquid crystal molecules LM2 that are spirally stacked along the third direction Z while rotating. Note that, as with the liquid crystal layer 11, the liquid crystal molecules LM2 constituting the cholesteric liquid crystal CL2 in the liquid crystal layer 12 are shown in a simplified form. 【0045】 In the illustrated XZ cross-section, the orientation directions of multiple adjacent cholesteric liquid crystal CL2 molecules along the first direction X are different from each other. In multiple adjacent cholesteric liquid crystal CL2 molecules along the first direction X, the orientation directions of liquid crystal molecules LM21 located on the same plane are different from each other. 【0046】 The reflective surface 12R, shown by the dashed line in the figure, corresponds to a surface where the orientation directions of the liquid crystal molecules LM2 are aligned, or a surface where the spatial phases are aligned (equal phase surface). 【0047】 These liquid crystal layers 11 and 12 are cured with the orientation direction of the liquid crystal molecules fixed. In other words, the orientation direction of the liquid crystal molecules is not controlled according to the electric field, as is the case with typical liquid crystal elements. 【0048】 Figure 7 is a schematic plan view showing the liquid crystal layer 11 shown in Figure 5. 【0049】 Figure 7 shows an example of the spatial phase of cholesteric liquid crystal CL1. The spatial phase shown here is represented by the orientation direction of the liquid crystal molecules LM11 contained in the cholesteric liquid crystal CL1, indicated by the dashed circle. In the XY plane, directions D11 and D12 are orthogonal to each other. Direction D11 intersects the first direction X at an angle θ11. Angle θ11 is acute counterclockwise with respect to the first direction X. 【0050】 For each of the cholesteric liquid crystals CL1 aligned along direction D11, the orientation direction of the liquid crystal molecules LM11 is approximately the same. In other words, the spatial phase of the cholesteric liquid crystals CL1 is approximately the same in direction D11. 【0051】 For each of the cholesteric liquid crystals CL1 aligned along direction D12, the orientation direction of the liquid crystal molecules LM11 is different from that of the others. In other words, the spatial phase of the cholesteric liquid crystals CL1 differs along direction D12. 【0052】 In particular, focusing on the cholesteric liquid crystal CL1 aligned in direction D12, the orientation direction of each liquid crystal molecule LM11 differs by a certain angle. That is, the orientation direction of multiple liquid crystal molecules LM11 aligned along direction D12 changes linearly. As a result, a reflective surface 11R tilted with respect to the XY plane is formed, as shown in Figures 5 and 6. "Linear change" here means, for example, that the amount of change in the orientation direction of the liquid crystal molecules LM11 can be expressed by a linear function. Note that the orientation direction of the liquid crystal molecules LM11 here corresponds to the long axis direction of the liquid crystal molecules LM11 in the XY plane. 【0053】 Figure 8 is a schematic plan view showing the liquid crystal layer 12 shown in Figure 5. 【0054】 Figure 8 shows an example of the spatial phase of a cholesteric liquid crystal CL2. The spatial phase shown here is represented by the orientation direction of the liquid crystal molecules LM21 contained in the cholesteric liquid crystal CL2, indicated by the dashed circle. In the XY plane, directions D21 and D22 are orthogonal to each other. Direction D21 intersects the first direction X at an angle θ21. Angle θ21 is acute clockwise with respect to the first direction X. In one example, angle θ21 is equivalent to angle θ11, but it may be different from angle θ11. 【0055】 For each of the cholesteric liquid crystals CL2 aligned along direction D21, the orientation direction of the liquid crystal molecules LM21 is approximately the same. In other words, the spatial phase of the cholesteric liquid crystals CL2 is approximately the same in direction D21. 【0056】 For each of the cholesteric liquid crystals CL2 aligned along direction D22, the orientation direction of the liquid crystal molecules LM21 is different from that of the others. In other words, the spatial phase of the cholesteric liquid crystals CL2 differs along direction D22. 【0057】 In particular, focusing on the cholesteric liquid crystal CL2 aligned in direction D22, the orientation direction of each liquid crystal molecule LM21 differs by a certain angle. In other words, the orientation direction of multiple liquid crystal molecules LM21 aligned along direction D22 changes linearly. As a result, a reflective surface 12R that is inclined with respect to the XY plane is formed, as shown in Figures 5 and 6. 【0058】 Figure 9 is a diagram illustrating the reflective surfaces 21R and 22R in the second optical element 20 shown in Figure 1. 【0059】 Each of the reflective surfaces 21R and 22R is inclined with respect to the second principal surface 1B, which is parallel to the XY plane. Furthermore, each of the reflective surfaces 21R and 22R is also inclined with respect to the XZ plane and the YZ plane. Moreover, the reflective surfaces 21R and 22R are non-parallel to each other. 【0060】 The reflective surface 21R is non-parallel to the reflective surface 11R shown in Figure 5. The intersection line between the reflective surface 21R and the XY plane is parallel to direction D11. Light LT1 traveling along direction D12 is reflected by the reflective surface 21R along the third direction Z. The reflective surface 21R is formed in the same way as the reflective surface 11R of the liquid crystal layer 11, as explained with reference to Figure 6, etc. 【0061】 The reflective surface 22R is non-parallel to the reflective surface 12R shown in Figure 5. The intersection line between the reflective surface 22R and the XY plane is parallel to direction D21. Light LT2 traveling along direction D22 is reflected at the reflective surface 22R along the third direction Z. The reflective surface 22R is formed in the same way as the reflective surface 12R of the liquid crystal layer 12, as described with reference to Figure 6 and other figures. 【0062】 Figure 10 is a plan view showing an example of image display in the DSP display device shown in Figure 1. 【0063】 In the display element 2 shown in Figure 1, for example, when a heart-shaped image is displayed, the display light DL emitted from the display element 2 is reflected by the liquid crystal layer 11 of the first optical element 10 toward the liquid crystal layer 21 of the second optical element 20, and by the liquid crystal layer 12 toward the liquid crystal layer 22 of the second optical element 20. The light LT1 reflected by the liquid crystal layer 11 and the light LT2 reflected by the liquid crystal layer 12 propagate through the transparent substrate 1. Then, light LT1 is reflected by the liquid crystal layer 21, and light LT2 is reflected by the liquid crystal layer 22 at a different position than light LT1. As a result, two heart-shaped images aligned in the second direction Y are displayed. 【0064】 As shown in Figure 1, when eye E faces the liquid crystal layer 21 as indicated by the solid line, the user can perceive a heart-shaped image as light LT1. Furthermore, when eye E faces the liquid crystal layer 22 as indicated by the dashed line, the user can perceive a heart-shaped image as light LT2. 【0065】 According to the above-described DSP display device, the image displayed on the display element 2 is divided into two parts and displayed side by side in the second direction Y. This allows multiple users with different eye positions E to view the display light DL at an optimal location corresponding to their eye position E, even when using the DSP display device. Therefore, it is possible to avoid causing discomfort to users and suppress a decrease in image visibility. 【0066】 Furthermore, in the first optical element 10, since the diffraction efficiency of the liquid crystal layer 11 is equivalent to that of the liquid crystal layer 12, the intensity of light LT1 reflected by the liquid crystal layer 11 is equivalent to the intensity of light LT2 reflected by the liquid crystal layer 12. Moreover, in the second optical element 20, since the diffraction efficiency of the liquid crystal layer 21 is equivalent to that of the liquid crystal layer 22, the intensity of light LT1 reflected by the liquid crystal layer 21 is equivalent to the intensity of light LT2 reflected by the liquid crystal layer 22. Therefore, regardless of whether the user views light LT1 or light LT2, they can view an image with equivalent brightness. 【0067】 Furthermore, in the second optical element 20, the thickness of the liquid crystal layer 21 and the liquid crystal layer 22 are smaller than the thickness of the liquid crystal layer 11 and the liquid crystal layer 12. Therefore, the user can see ambient light through the second optical element 20. 【0068】 In this configuration example, liquid crystal layer 11 corresponds to the first liquid crystal layer of the first optical element 10, liquid crystal layer 12 corresponds to the second liquid crystal layer of the first optical element 10, liquid crystal layer 21 corresponds to the first liquid crystal layer of the second optical element 20, and liquid crystal layer 22 corresponds to the second liquid crystal layer of the second optical element 20. Furthermore, cholesteric liquid crystal CL1 corresponds to the first cholesteric liquid crystal, cholesteric liquid crystal CL2 corresponds to the second cholesteric liquid crystal, and helical pitches P1 and P2 correspond to the first helical pitch. Reflective surface 11R corresponds to the first reflective surface of the first optical element 10, reflective surface 12R corresponds to the second reflective surface of the first optical element 10, reflective surface 21R corresponds to the first reflective surface of the second optical element 20, and reflective surface 22R corresponds to the second reflective surface of the second optical element 20. 【0069】 Here, we will briefly describe an example of a method for manufacturing the liquid crystal layer applied to the first optical element 10 and the second optical element 20, respectively. 【0070】 First, an alignment film is formed on a support substrate different from the transparent substrate 1. The alignment film has an alignment axis of a predetermined alignment pattern. The desired alignment pattern is formed, for example, by applying interference exposure using right-circularly polarized and left-circularly polarized light. Then, a solution containing polymerizable liquid crystal material and a polymerization initiator is applied onto the alignment film. The solvent of the applied solution is removed by vacuum drying, and the polymerizable liquid crystal material is heated at a temperature not exceeding the NI point (Nematic-Isotropic transition temperature) and then cooled. In this process, the liquid crystal molecules contained in the polymerizable liquid crystal material are arranged in a spiral shape by the alignment restricting force of the alignment film. Then, by irradiating the polymerizable liquid crystal material and polymerization initiator with ultraviolet light, the liquid crystal molecules harden as a polymer liquid crystal material in a cholesteric liquid crystal phase. This forms a liquid crystal layer. The liquid crystal layer thus formed is peeled off from the alignment film and transferred to the transparent substrate 1. 【0071】 In the first optical element 10 and the second optical element 20, light can be reflected in a desired direction by adjusting the alignment pattern formed on the alignment film, adjusting the angle of the support substrate, or tilting the liquid crystal layer transferred to the transparent substrate 1 in the XY plane. 【0072】 Next, we will describe some other configuration examples. Note that components similar to those in the above examples will be given the same reference numerals, and redundant explanations may be omitted. 【0073】 Figure 11 shows another example of a DSP display device configuration. 【0074】 The configuration example shown in Figure 11 differs from the configuration example shown in Figure 1 in that the second optical element 20 has four liquid crystal layers. The first optical element 10 is configured as a laminate of liquid crystal layer 11 and liquid crystal layer 12, similar to the configuration example shown in Figure 1. 【0075】 The second optical element 20 comprises a liquid crystal layer 211, a liquid crystal layer 212, a liquid crystal layer 221, and a liquid crystal layer 222. The liquid crystal layers 211 and 221 are aligned in the second direction Y. The liquid crystal layers 211 and 212 are aligned in the first direction X. The liquid crystal layers 221 and 222 are aligned in the first direction X. The liquid crystal layers 212 and 222 are aligned in the second direction Y. 【0076】 The liquid crystal layer 212 is located between the liquid crystal layer 211 and the first optical element 10, and is close to the liquid crystal layer 211. The liquid crystal layer 222 is located between the liquid crystal layer 221 and the first optical element 10, and is close to the liquid crystal layer 221. 【0077】 Figure 12 is a diagram illustrating the liquid crystal layer 211 and liquid crystal layer 212 of the display device DSP shown in Figure 11. 【0078】 As shown schematically in the magnified view, liquid crystal layers 211 and 212 contain the same cholesteric liquid crystal CL1. The cholesteric liquid crystal CL1 has a helical pitch P1 along the third direction Z. Liquid crystal layer 211 has a reflective surface 211R. Liquid crystal layer 212 has a reflective surface 212R. At reflective surfaces 211R and 212R, circularly polarized light (e.g., right-handed circularly polarized light) corresponding to the rotational direction of the cholesteric liquid crystal CL1 is reflected from the selected reflection band. 【0079】 The reflective surfaces 211R and 212R are inclined with respect to the XY plane. The liquid crystal layer 211 is configured to reflect a portion of the light LT1 along the normal to the second principal surface 1B. The liquid crystal layer 212 is configured to reflect the other portion of the light LT1 along the normal to the second principal surface 1B. 【0080】 When the user's eye E faces the liquid crystal layer 211 in the third direction Z, the user can see the light LT1. The user can also see the light LT1 when the user's eye E faces the liquid crystal layer 212 in the third direction Z. 【0081】 As described above, the liquid crystal layer 212 is closer to the first optical element 10 than the liquid crystal layer 211. Therefore, the light LT1 reaching the liquid crystal layer 211 is attenuated more than the light LT1 reaching the liquid crystal layer 212. From the viewpoint of suppressing the attenuation of light LT1, it is desirable that the diffraction efficiency of the liquid crystal layer 212 be lower than that of the liquid crystal layer 211. Also, from the viewpoint of equalizing the intensity of the visible light LT1 whether the eye E is facing the liquid crystal layer 211 or the liquid crystal layer 212, it is desirable that the diffraction efficiency of the liquid crystal layer 211 be higher than that of the liquid crystal layer 212. For this reason, in the illustrated example, the liquid crystal layer 211 is thicker than the liquid crystal layer 212. 【0082】 Figure 13 is a diagram illustrating the liquid crystal layer 221 and liquid crystal layer 222 of the display device DSP shown in Figure 11. 【0083】 As shown schematically in the magnified view, liquid crystal layers 221 and 222 contain the same cholesteric liquid crystal CL2. The cholesteric liquid crystal CL2 has a helical pitch P2 along the third direction Z. Liquid crystal layer 221 has a reflective surface 221R. Liquid crystal layer 222 has a reflective surface 222R. Reflective surfaces 221R and 222R reflect circularly polarized light (e.g., left-handed circularly polarized light) corresponding to the rotational direction of the cholesteric liquid crystal CL2 from the selected reflection band. 【0084】 The reflective surfaces 221R and 222R are inclined with respect to the XY plane. The liquid crystal layer 221 is configured to reflect a portion of the light LT2 along the normal to the second principal surface 1B. The liquid crystal layer 222 is configured to reflect the other portion of the light LT2 along the normal to the second principal surface 1B. 【0085】 When the user's eye E faces the liquid crystal layer 221 in the third direction Z, the user can see the light LT2. Similarly, when the user's eye E faces the liquid crystal layer 222 in the third direction Z, the user can also see the light LT2. 【0086】 As described above, the liquid crystal layer 222 is closer to the first optical element 10 than the liquid crystal layer 221. Therefore, the light LT2 reaching the liquid crystal layer 221 is attenuated more than the light LT2 reaching the liquid crystal layer 222. From the viewpoint of suppressing the attenuation of light LT2, it is desirable that the diffraction efficiency of the liquid crystal layer 222 be lower than that of the liquid crystal layer 221. Furthermore, from the viewpoint of equalizing the intensity of the visible light LT2 whether the eye E is facing the liquid crystal layer 221 or the liquid crystal layer 222, it is desirable that the diffraction efficiency of the liquid crystal layer 221 be higher than that of the liquid crystal layer 222. For this reason, in the illustrated example, the liquid crystal layer 221 is thicker than the liquid crystal layer 222. 【0087】 Figure 14 is a plan view showing an example of image display in the DSP display device shown in Figure 11. 【0088】 In the display element 2 shown in Figure 11, for example, when a heart-shaped image is displayed, the display light DL emitted from the display element 2 is reflected by the liquid crystal layer 11 of the first optical element 10 toward the liquid crystal layers 211 and 212 of the second optical element 20, and by the liquid crystal layer 12 toward the liquid crystal layers 221 and 222 of the second optical element 20. The light LT1 reflected by the liquid crystal layer 11 and the light LT2 reflected by the liquid crystal layer 12 propagate through the transparent substrate 1. The light LT1 is then reflected by the liquid crystal layers 211 and 212, and the light LT2 is reflected by the liquid crystal layers 221 and 222 at positions different from the light LT1. As a result, four heart-shaped images are displayed, aligned in the first direction X and the second direction Y. 【0089】 As shown in Figure 11, when eye E faces liquid crystal layer 211 as indicated by the solid line, or when eye E faces liquid crystal layer 212 as indicated by the dashed line, the user can perceive a heart-shaped image as light LT1. Furthermore, when eye E faces liquid crystal layer 221, or when eye E faces liquid crystal layer 222, the user can perceive a heart-shaped image as light LT2. 【0090】 According to the above-described DSP display device, the image displayed on the display element 2 is divided into four sections and displayed in the first direction X and the second direction Y. This allows multiple users with different eye positions E to view the display light DL at an optimal location corresponding to their eye position E, even when using the DSP display device. Therefore, it is possible to avoid causing discomfort to users and suppress a decrease in image visibility. 【0091】 Furthermore, in the second optical element 20, the diffraction efficiency of each of the liquid crystal layers 211, 212, 221, and 222 can be adjusted independently. Therefore, as explained with reference to Figure 12, an image of equivalent brightness can be viewed whether the light LT1 reflected by liquid crystal layer 211 or the light LT1 reflected by liquid crystal layer 212 is being viewed. Also, as explained with reference to Figure 13, an image of equivalent brightness can be viewed whether the light LT2 reflected by liquid crystal layer 221 or the light LT2 reflected by liquid crystal layer 222 is being viewed. 【0092】 Furthermore, in the second optical element 20, it is also possible to make the transmittance of each of the liquid crystal layers 211, 212, 221, and 222 the same. 【0093】 In this configuration example, liquid crystal layer 211 corresponds to the first liquid crystal layer of the second optical element 20, liquid crystal layer 221 corresponds to the second liquid crystal layer of the second optical element 20, liquid crystal layer 212 corresponds to the third liquid crystal layer of the second optical element 20, and liquid crystal layer 222 corresponds to the fourth liquid crystal layer of the second optical element 20. Furthermore, the cholesteric liquid crystal CL1 of liquid crystal layer 211 corresponds to the first cholesteric liquid crystal, the cholesteric liquid crystal CL2 of liquid crystal layer 221 corresponds to the second cholesteric liquid crystal, the cholesteric liquid crystal CL1 of liquid crystal layer 212 corresponds to the third cholesteric liquid crystal, and the cholesteric liquid crystal CL2 of liquid crystal layer 222 corresponds to the fourth cholesteric liquid crystal. 【0094】 Figure 15 shows another example of a DSP display device configuration. 【0095】 The configuration example shown in Figure 15 differs from the configuration example shown in Figure 1 in that, in the second optical element 20, the liquid crystal layer 21 and the liquid crystal layer 22 are aligned in the first direction X. The first optical element 10 is constructed as a laminate of liquid crystal layer 11 and liquid crystal layer 12, similar to the configuration example shown in Figure 1. 【0096】 The liquid crystal layer 22 is located between the liquid crystal layer 21 and the first optical element 10, and is in close proximity to the liquid crystal layer 21. The liquid crystal layer 21 contains cholesteric liquid crystal CL1, as described with reference to Figure 3. The liquid crystal layer 22 also contains cholesteric liquid crystal CL2, as described with reference to Figure 4. The diffraction efficiency of the liquid crystal layer 21 is equivalent to that of the liquid crystal layer 22. In other words, the liquid crystal layers 21 and 22 have equivalent thicknesses. 【0097】 However, in the first optical element 10, the reflective surfaces 11R of the liquid crystal layer 11 and 12R of the liquid crystal layer 12 have different shapes than those shown in Figure 5. Also, in the second optical element 20, the reflective surfaces 21R of the liquid crystal layer 21 and 22R of the liquid crystal layer 22 have different shapes than those shown in Figure 9. The reflective surfaces of the first optical element 10 and the second optical element 20 will be described below. 【0098】 Figure 16 is a diagram illustrating the reflective surfaces 11R and 12R in the first optical element 10 shown in Figure 15. 【0099】 Each of the reflective surfaces 11R and 12R is inclined with respect to a second principal surface 1B that is parallel to the XY plane. Furthermore, each of the reflective surfaces 11R and 12R is also inclined with respect to the XZ plane and the YZ plane. Moreover, the reflective surfaces 11R and 12R are parallel to each other. 【0100】 The line of intersection between the reflective surface 11R and the XY plane is parallel to direction D11 and parallel to the second direction Y. Direction D12, which is perpendicular to direction D11, is parallel to the first direction X. The indicator light DL traveling along the third direction Z is reflected by the reflective surface 11R along direction D12. In other words, the direction of propagation of the light LT1 reflected by the reflective surface 11R is parallel to the first direction X or direction D12 in the XY plane. 【0101】 The line of intersection between the reflective surface 12R and the XY plane is parallel to direction D21 and parallel to the second direction Y. Direction D21 is also parallel to direction D11. Direction D22, which is perpendicular to direction D21, is parallel to the first direction X and parallel to direction D12. The indicator light DL traveling along the third direction Z is reflected by the reflective surface 12R along direction D22. In other words, the direction of propagation of the light LT2 reflected by the reflective surface 12R is parallel to the first direction X or direction D22 in the XY plane. 【0102】 Figure 17 is a diagram illustrating the reflective surfaces 21R and 22R in the second optical element 20 shown in Figure 15. 【0103】 Each of the reflective surfaces 21R and 22R is inclined with respect to the second principal surface 1B, which is parallel to the XY plane. Furthermore, each of the reflective surfaces 21R and 22R is also inclined with respect to the XZ plane and the YZ plane. Moreover, the reflective surfaces 21R and 22R are parallel to each other. 【0104】 The reflective surface 21R is non-parallel to the reflective surface 11R shown in Figure 16. The line of intersection between the reflective surface 21R and the XY plane is parallel to direction D11. Light LT1 traveling along direction D12 is reflected at the reflective surface 21R along the third direction Z. 【0105】 The reflective surface 22R is non-parallel to the reflective surface 12R shown in Figure 16. The line of intersection between the reflective surface 22R and the XY plane is parallel to direction D21. Light LT2 traveling along direction D22 is reflected at the reflective surface 22R along the third direction Z. 【0106】 Figure 18 is a plan view showing an example of image display in the DSP display device shown in Figure 15. 【0107】 In the display element 2 shown in Figure 15, for example, when a heart-shaped image is displayed, the display light DL emitted from the display element 2 is reflected by the liquid crystal layer 11 of the first optical element 10 toward the liquid crystal layer 21 of the second optical element 20, and by the liquid crystal layer 12 toward the liquid crystal layer 22 of the second optical element 20. The light LT1 reflected by the liquid crystal layer 11 and the light LT2 reflected by the liquid crystal layer 12 propagate through the transparent substrate 1 along the first direction X. The light LT1 is then reflected by the liquid crystal layer 21. The light LT2 is reflected by the liquid crystal layer 22 at a different position than the light LT1. As a result, two heart-shaped images aligned in the second direction Y are displayed. Note that the optical rotation direction of the light LT1 is different from the optical rotation direction of the cholesteric liquid crystal CL2 that constitutes the liquid crystal layer 22, so the light LT1 is not reflected by the liquid crystal layer 22. 【0108】 As shown in Figure 15, when eye E faces the liquid crystal layer 21 as indicated by the solid line, the user can see a heart-shaped image as light LT1. Furthermore, when eye E faces the liquid crystal layer 22 as indicated by the dashed line, the user can see a heart-shaped image as light LT2. 【0109】 According to the above-described DSP display device, the image displayed on the display element 2 is divided into two parts and displayed side by side in the first direction X. As a result, even when multiple users with different eye positions E use the DSP display device, each user can view the display light DL at an optimal location corresponding to their eye position E. Therefore, it is possible to avoid causing discomfort to the user and suppress a decrease in image visibility. 【0110】 Furthermore, the diffraction efficiency of the liquid crystal layer 21 and the liquid crystal layer 22 can be adjusted independently. Therefore, an image with equivalent brightness can be viewed regardless of whether light LT1 or light LT2 is being viewed. 【0111】 Furthermore, in the second optical element 20, it is also possible to make the transmittance of the liquid crystal layer 21 and the liquid crystal layer 22 the same. 【0112】 Figure 19 shows another example of a display device DSP configuration. 【0113】 The configuration example shown in Figure 19 differs from the configuration example shown in Figure 15 in that the second optical element 20 is configured as a laminate of liquid crystal layers 21 and 22. The first optical element 10 is configured as a laminate of liquid crystal layers 11 and 12, similar to the configuration example shown in Figure 15. 【0114】 The liquid crystal layer 21 contains cholesteric liquid crystal CL1, as explained with reference to Figure 3. The liquid crystal layer 22 also contains cholesteric liquid crystal CL2, as explained with reference to Figure 4. 【0115】 In the first optical element 10, the reflective surfaces 11R of the liquid crystal layer 11 and 12R of the liquid crystal layer 12 have the same shape as shown in Figure 16. In the second optical element 20, the reflective surfaces 21R of the liquid crystal layer 21 and 22R of the liquid crystal layer 22 have the same shape as shown in Figure 17. 【0116】 Figure 20 is a plan view showing an example of image display in the DSP display device shown in Figure 19. 【0117】 In the display element 2 shown in Figure 19, for example, when a heart-shaped image is displayed, the display light DL emitted from the display element 2 is reflected by the liquid crystal layer 11 of the first optical element 10 toward the liquid crystal layer 21 of the second optical element 20, and by the liquid crystal layer 12 toward the liquid crystal layer 22 of the second optical element 20. The light LT1 reflected by the liquid crystal layer 11 and the light LT2 reflected by the liquid crystal layer 12 propagate through the transparent substrate 1 along the first direction X. The light LT1 is then reflected by the liquid crystal layer 21, and the light LT2 is reflected by the liquid crystal layer 22 at the same position as the light LT1. 【0118】 As shown in Figure 19, when the eye E faces the second optical element 20, the user can perceive a heart-shaped image as light LT1 and light LT2. In other words, it is possible to display a higher brightness image than in each of the above configuration examples. 【0119】 Figure 21 shows another example of a DSP display device configuration. 【0120】 The configuration example shown in Figure 21 differs from the configuration example shown in Figure 1 in that the display device DSP is configured to enable multi-color display. 【0121】 The first optical element 10 includes liquid crystal layers 11 and 12, as well as liquid crystal layers 13, 14, 15, and 16. In the illustrated example, liquid crystal layers 11, 12, 13, 14, 15, and 16 are stacked in this order along the third direction Z. 【0122】 The second optical element 20 includes liquid crystal layers 21 and 22, as well as liquid crystal layers 23, 24, 25, and 26. Liquid crystal layers 21, 23, and 25 are stacked in this order along the third direction Z to form the first laminate 20A. Liquid crystal layers 22, 24, and 26 are stacked in this order along the third direction Z to form the second laminate 20B. These first laminate 20A and second laminate 20B are aligned in the second direction Y. 【0123】 Note that the stacking order of the multiple liquid crystal layers in the first optical element 10 and the second optical element 20 is not limited to the example shown. 【0124】 Figure 22 is a diagram illustrating the first optical element 10 of the display device DSP shown in Figure 21. 【0125】 As shown schematically in an enlarged view, liquid crystal layers 11, 12, 13, 14, 15, and 16 each contain cholesteric liquid crystal CL1, cholesteric liquid crystal CL2, cholesteric liquid crystal CL3, cholesteric liquid crystal CL4, cholesteric liquid crystal CL5, and cholesteric liquid crystal CL6, respectively. 【0126】 The cholesteric liquid crystal CL1 has a helical pitch P1 along the third direction Z. The liquid crystal layer 11 has a reflective surface 11R. 【0127】 The cholesteric liquid crystal CL2 rotates in the opposite direction to the cholesteric liquid crystal CL1 and has a helical pitch P2 along the third direction Z. The helical pitch P2 is equivalent to the helical pitch P1. The liquid crystal layer 12 has a reflective surface 12R. 【0128】 The cholesteric liquid crystal CL3 has a helical pitch P3 along the third direction Z. The helical pitch P3 is different from the helical pitch P1. The liquid crystal layer 13 has a reflective surface 13R. 【0129】 The cholesteric liquid crystal CL4 rotates in the opposite direction to the cholesteric liquid crystal CL3 and has a helical pitch P4 along the third direction Z. The helical pitch P4 is equivalent to the helical pitch P3. The liquid crystal layer 14 has a reflective surface 14R. 【0130】 The cholesteric liquid crystal CL5 has a helical pitch P5 along the third direction Z. The helical pitch P5 is different from both the helical pitch P1 and the helical pitch P3. The liquid crystal layer 15 has a reflective surface 15R. 【0131】 The cholesteric liquid crystal CL6 rotates in the opposite direction to the cholesteric liquid crystal CL5 and has a helical pitch P6 along the third direction Z. The helical pitch P6 is equivalent to the helical pitch P5. The liquid crystal layer 16 has a reflective surface 16R. 【0132】 In the illustrated example, the helical pitch P3 is greater than the helical pitch P1, and the helical pitch P5 is greater than the helical pitch P3. 【0133】 The reflective surfaces 11R and 12R are configured to reflect light in the same first wavelength band λ1 as a selective reflection band. The light LT1 reflected by reflective surface 11R is, for example, right-handed circularly polarized λ1a in the first wavelength band λ1. The light LT2 reflected by reflective surface 12R is left-handed circularly polarized λ1b in the first wavelength band λ1. 【0134】 Reflecting surfaces 13R and 14R are configured to reflect light in the same second wavelength band λ2 as a selective reflection band. The second wavelength band λ2 has a longer wavelength than the first wavelength band λ1. The light LT3 reflected by reflecting surface 13R is, for example, right-handed circularly polarized light λ2a in the second wavelength band λ2. The light LT4 reflected by reflecting surface 14R is left-handed circularly polarized light λ2b in the second wavelength band λ2. 【0135】 Reflecting surfaces 15R and 16R are configured to reflect light in the same third wavelength band λ3 as a selective reflection band. The third wavelength band λ3 has a longer wavelength than the second wavelength band λ2. The light LT5 reflected by reflecting surface 15R is, for example, right-handed circularly polarized light λ3a in the third wavelength band λ3. The light LT6 reflected by reflecting surface 16R is left-handed circularly polarized light λ3b in the third wavelength band λ3. 【0136】 Liquid crystal layer 11, liquid crystal layer 13, and liquid crystal layer 15 are configured to reflect the display light DL toward the first laminate 20A. Each of the light LT1, light LT3, and light LT5 propagates in directions different from the first direction X and the second direction Y in the transparent substrate 1, while undergoing total internal reflection at the first main surface 1A and the second main surface 1B, and propagates toward the first laminate 20A as shown in Figure 21. 【0137】 Liquid crystal layer 12, liquid crystal layer 14, and liquid crystal layer 16 are configured to reflect the display light DL toward the second laminate 20B. Each of the light LT2, light LT4, and light LT6 propagates in directions different from the first direction X and the second direction Y in the transparent substrate 1, while undergoing total internal reflection at the first main surface 1A and the second main surface 1B, and propagates toward the second laminate 20B as shown in Figure 21. 【0138】 Figure 23 is a diagram illustrating the first stacked layer 20A of the display device DSP shown in Figure 21. 【0139】 As shown schematically in an enlarged view, liquid crystal layers 21, 23, and 25 each contain cholesteric liquid crystal CL1, CL3, and CL5, respectively. In other words, liquid crystal layer 21 has the same configuration as liquid crystal layer 11, liquid crystal layer 23 has the same configuration as liquid crystal layer 13, and liquid crystal layer 25 has the same configuration as liquid crystal layer 15. 【0140】 The liquid crystal layer 21 has a reflective surface 21R that reflects the light LT1 reflected by the liquid crystal layer 11. The light LT1 reflected by the reflective surface 21R is right-handed circularly polarized λ1a in the first wavelength band λ1. Such a liquid crystal layer 21 is configured to reflect the light LT1 along the normal to the second principal surface 1B. 【0141】 The liquid crystal layer 23 has a reflective surface 23R that reflects the light LT3 reflected by the liquid crystal layer 13. The light LT3 reflected by the reflective surface 23R is right-handed circularly polarized light λ2a in the second wavelength band λ2. Such a liquid crystal layer 23 is configured to reflect the light LT3 along the normal to the second principal surface 1B. 【0142】 The liquid crystal layer 25 has a reflective surface 25R that reflects the light LT5 reflected by the liquid crystal layer 15. The light LT5 reflected by the reflective surface 25R is right-handed circularly polarized light λ3a in the third wavelength band λ3. Such a liquid crystal layer 25 is configured to reflect the light LT5 along the normal to the second principal surface 1B. 【0143】 When the user's eye E faces the first laminate 20A in the third direction Z, the user can see the light LT1 in the first wavelength band λ1, the light LT3 in the second wavelength band λ2, and the light LT5 in the third wavelength band λ3. 【0144】 Figure 24 is a diagram illustrating the second stack 20B of the display device DSP shown in Figure 21. 【0145】 As shown schematically in an enlarged view, liquid crystal layers 22, 24, and 26 each contain cholesteric liquid crystal CL2, CL4, and CL6, respectively. In other words, liquid crystal layer 22 has the same configuration as liquid crystal layer 12, liquid crystal layer 24 has the same configuration as liquid crystal layer 14, and liquid crystal layer 26 has the same configuration as liquid crystal layer 16. 【0146】 The liquid crystal layer 22 has a reflective surface 22R that reflects the light LT2 reflected by the liquid crystal layer 12. The light LT2 reflected by the reflective surface 22R is left-handed circularly polarized λ1b in the first wavelength band λ1. Such a liquid crystal layer 22 is configured to reflect the light LT2 along the normal to the second principal surface 1B. 【0147】 The liquid crystal layer 24 has a reflective surface 24R that reflects the light LT4 reflected by the liquid crystal layer 14. The light LT4 reflected by the reflective surface 24R is left-handed circularly polarized light λ2b in the second wavelength band λ2. Such a liquid crystal layer 24 is configured to reflect the light LT4 along the normal to the second principal surface 1B. 【0148】 The liquid crystal layer 26 has a reflective surface 26R that reflects the light LT6 reflected by the liquid crystal layer 16. The light LT6 reflected by the reflective surface 26R is left-handed circularly polarized light λ3b in the third wavelength band λ3. Such a liquid crystal layer 26 is configured to reflect the light LT6 along the normal to the second principal surface 1B. 【0149】 When the user's eye E faces the second laminate 20B in the third direction Z, the user can see the light LT2 in the first wavelength band λ1, the light LT4 in the second wavelength band λ2, and the light LT6 in the third wavelength band λ3. 【0150】 According to the above-described display device DSP, as shown in Figure 21, the image displayed on the display element 2 is divided into two parts and displayed side by side in the second direction Y as a multicolor image. As a result, even when multiple users with different eye positions E use the display device DSP, each user can view the display light DL at an optimal location corresponding to their eye position E. Therefore, it is possible to avoid causing discomfort to the user and suppress a decrease in the visibility of the multicolor image. 【0151】 As described above, in the configuration example explained with reference to Figures 21 to 24, the liquid crystal layer 11 corresponds to the first liquid crystal layer of the first optical element 10, the liquid crystal layer 12 corresponds to the second liquid crystal layer of the first optical element 10, the liquid crystal layer 13 corresponds to the third liquid crystal layer of the first optical element 10, the liquid crystal layer 14 corresponds to the fourth liquid crystal layer of the first optical element 10, the liquid crystal layer 15 corresponds to the fifth liquid crystal layer of the first optical element 10, and the liquid crystal layer 16 corresponds to the sixth liquid crystal layer of the first optical element 10. 【0152】 Liquid crystal layer 21 corresponds to the first liquid crystal layer of the second optical element 20, liquid crystal layer 22 corresponds to the second liquid crystal layer of the second optical element 20, liquid crystal layer 23 corresponds to the third liquid crystal layer of the second optical element 20, liquid crystal layer 24 corresponds to the fourth liquid crystal layer of the second optical element 20, liquid crystal layer 25 corresponds to the fifth liquid crystal layer of the second optical element 20, and liquid crystal layer 26 corresponds to the sixth liquid crystal layer of the second optical element 20. 【0153】 Cholesteric liquid crystal CL1 corresponds to the first cholesteric liquid crystal, cholesteric liquid crystal CL2 corresponds to the second cholesteric liquid crystal, cholesteric liquid crystal CL3 corresponds to the third cholesteric liquid crystal, cholesteric liquid crystal CL4 corresponds to the fourth cholesteric liquid crystal, cholesteric liquid crystal CL5 corresponds to the fifth cholesteric liquid crystal, and cholesteric liquid crystal CL6 corresponds to the sixth cholesteric liquid crystal. Helical pitches P1 and P2 correspond to the first helical pitch, helical pitches P3 and P4 correspond to the second helical pitch, and helical pitches P5 and P6 correspond to the third helical pitch. 【0154】 As described above, this embodiment provides a display device and a light guide element that can suppress a decrease in the visibility of images. 【0155】 While several embodiments of this disclosure have been described, these embodiments are presented as examples only and are not intended to limit the scope of the disclosure. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications are permitted without departing from the gist of the disclosure. These embodiments and their variations are included in the scope and gist of the disclosure, as well as in the disclosures described in the claims and their equivalents. [Explanation of Symbols] 【0156】 DSP…display device 1…Transparent substrate 1A…First main surface 1B…Second main surface DM...Display module 100...Liquid crystal optical element 10…First optical element 20…Second optical element 11...First liquid crystal layer CL1...First cholesteric liquid crystal 12...Second liquid crystal layer CL2...Second cholesteric liquid crystal

Claims

[Claim 1] A transparent substrate having a first main surface and a second main surface opposite to the first main surface, A display element facing the first main surface and configured to emit display light toward the transparent substrate, A first optical element is positioned opposite the display element via the transparent substrate, on the second main surface, and configured to reflect the display light that has passed through the transparent substrate. The device comprises a second optical element spaced apart from the first optical element, positioned on the second main surface, and configured to reflect the display light propagated through the interior of the transparent substrate, Each of the first optical element and the second optical element is A first liquid crystal layer including a first cholesteric liquid crystal, The device comprises a second liquid crystal layer including a second cholesteric liquid crystal that is swirled in the opposite direction to the first cholesteric liquid crystal, In the first optical element, the second liquid crystal layer overlaps the first liquid crystal layer. In the second optical element, the first liquid crystal layer and the second liquid crystal layer are arranged in the second main surface. Display device. [Claim 2] The first cholesteric liquid crystal and the second cholesteric liquid crystal have equivalent first helical pitches. The display device according to claim 1. [Claim 3] The first liquid crystal layer of the second optical element is configured to reflect the display light reflected by the first liquid crystal layer of the first optical element along the normal to the second main surface. The second liquid crystal layer of the second optical element is configured to reflect the display light reflected by the second liquid crystal layer of the first optical element along the normal to the second main surface. The display device according to claim 1. [Claim 4] The first optical element and the second optical element are arranged with an interval between them in the first direction. In the second optical element, the first liquid crystal layer and the second liquid crystal layer are arranged in a second direction intersecting the first direction. The display device according to claim 1. [Claim 5] In each of the first optical element and the second optical element, The first liquid crystal layer has a first reflective surface that is inclined with respect to the second main surface, The second liquid crystal layer has a second reflective surface that is inclined with respect to the second main surface, The first reflective surface and the second reflective surface are non-parallel to each other. The display device according to claim 4. [Claim 6] The first liquid crystal layer in the second optical element is thinner than the first liquid crystal layer in the first optical element. The second liquid crystal layer in the second optical element is thinner than the second liquid crystal layer in the first optical element. The display device according to claim 1. [Claim 7] The above second optical element further, A third liquid crystal layer including a third cholesteric liquid crystal identical to the first cholesteric liquid crystal, The fourth liquid crystal layer includes a fourth cholesteric liquid crystal identical to the second cholesteric liquid crystal, In the second optical element, the first liquid crystal layer and the third liquid crystal layer are aligned in the first direction, and the second liquid crystal layer and the fourth liquid crystal layer are aligned in the first direction. The display device according to claim 4. [Claim 8] The first liquid crystal layer is thicker than the third liquid crystal layer. The second liquid crystal layer is thicker than the fourth liquid crystal layer. The display device according to claim 7. [Claim 9] The first optical element and the second optical element are arranged with an interval between them in the first direction. In the second optical element, the first liquid crystal layer and the second liquid crystal layer are aligned in the first direction. The display device according to claim 1. [Claim 10] The first liquid crystal layer and the second liquid crystal layer have equivalent thicknesses. The display device according to claim 9. [Claim 11] In each of the first optical element and the second optical element, The first liquid crystal layer has a first reflective surface that is inclined with respect to the second main surface, The second liquid crystal layer has a second reflective surface that is inclined with respect to the second main surface, The first reflective surface and the second reflective surface are parallel to each other. The display device according to claim 9. [Claim 12] Each of the first optical element and the second optical element further comprises: A third liquid crystal layer including a third cholesteric liquid crystal, A fourth liquid crystal layer including a fourth cholesteric liquid crystal that is rotated in the opposite direction to the third cholesteric liquid crystal, A fifth liquid crystal layer including a fifth cholesteric liquid crystal, The device comprises a sixth liquid crystal layer including a sixth cholesteric liquid crystal that is rotated in the opposite direction to the fifth cholesteric liquid crystal, The first cholesteric liquid crystal and the second cholesteric liquid crystal have equivalent first helical pitches. The third cholesteric liquid crystal and the fourth cholesteric liquid crystal have equivalent second helical pitches. The fifth cholesteric liquid crystal and the sixth cholesteric liquid crystal have equivalent third helical pitches. The first helical pitch, the second helical pitch, and the third helical pitch are different from each other. The first optical element is a laminate of the first liquid crystal layer, the second liquid crystal layer, the third liquid crystal layer, the fourth liquid crystal layer, the fifth liquid crystal layer, and the sixth liquid crystal layer. The second optical element comprises a first laminate of the first liquid crystal layer, the third liquid crystal layer, and the fifth liquid crystal layer, and a second laminate of the second liquid crystal layer, the fourth liquid crystal layer, and the sixth liquid crystal layer. The display device according to claim 1. [Claim 13] In the first optical element, The first liquid crystal layer, the third liquid crystal layer, and the fifth liquid crystal layer are configured to reflect the display light toward the first laminate. The second liquid crystal layer, the fourth liquid crystal layer, and the sixth liquid crystal layer are configured to reflect the display light toward the second laminate. The display device according to claim 12. [Claim 14] In the second optical element, Each of the first liquid crystal layer, the second liquid crystal layer, the third liquid crystal layer, the fourth liquid crystal layer, the fifth liquid crystal layer, and the sixth liquid crystal layer is configured to reflect the display light propagated through the interior of the transparent substrate along the normal to the second main surface. The display device according to claim 13.

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