Lens unit and display device

Abstract

To improve display quality.SOLUTION: A lens portion includes: a first lens element having a lens action of converging while converting first circularly polarized light of a first wavelength into second circularly polarized light of a reverse direction; and a second lens element having a lens action of converging while converting the second circularly polarized light of the first wavelength into the first circularly polarized light of the first wavelength. Each of the first lens element and the second lens element includes a liquid crystal layer cured in a state in which alignment directions of a plurality of liquid crystal molecules containing first liquid crystal molecules and second liquid crystal molecules are fixed, the liquid crystal layer includes a first annular area in which the plurality of first liquid crystal molecules is aligned in a same direction and a second annular area in which the plurality of second liquid crystal molecules is aligned in a same direction, a circle surrounding the first annular area and a circle surrounding the second annular area have same centers, an alignment direction of the first liquid crystal molecule is different from an alignment direction of the second liquid crystal molecule, and the alignment direction of the first liquid crystal molecule of the first lens element is line symmetry with the alignment direction of the first liquid crystal molecule of the second lens element with respect to a line passing the centers in a plan view.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a lens unit and a display device. [Background technology]

[0002] In recent years, attention has been focused on technology that provides virtual reality (VR) using a head-mounted display worn on the user's head. A head-mounted display is configured to display images on a display placed in front of the user's eyes. This allows a user wearing the head-mounted display to experience a realistic virtual reality space. There is an increasing demand for thinner and lighter head-mounted displays. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2003-504663 [Patent Document 2] Special Publication No. 2003-529795 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-106160 [Patent Document 4] Japanese Patent Application Publication No. 2019-53152 [Patent Document 5] Japanese Patent Application Publication No. 2019-148626 [Patent Document 6] Japanese Patent Application Publication No. 2019-148627 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments is to provide a lens unit and a display device that can improve display quality. [Means for solving the problem]

[0005] According to the embodiment, the following lens portion can be provided.

[0006] (1) a first lens element having a lens effect of converting a first circularly polarized light of a first wavelength into a second circularly polarized light of an opposite rotation while focusing the light; a second lens element that is stacked on the first lens element and has a lens effect of converting the second circularly polarized light of the first wavelength into the first circularly polarized light of the first wavelength and focusing the light, each of the first lens element and the second lens element has a liquid crystal layer that is hardened in a state in which the alignment direction of a plurality of liquid crystal molecules including first liquid crystal molecules and second liquid crystal molecules is fixed; the liquid crystal layer has, in a plan view, a first annular region in which a plurality of the first liquid crystal molecules are aligned in the same direction, and a second annular region outside the first annular region in which a plurality of the second liquid crystal molecules are aligned in the same direction; a circle surrounding the first annular region and a circle surrounding the second annular region have the same center; The alignment direction of the first liquid crystal molecules is different from the alignment direction of the second liquid crystal molecules, the first annular region of the first lens element overlaps the first annular region of the second lens element; a lens portion in which the alignment direction of the first liquid crystal molecules of the first lens element is symmetrical to the alignment direction of the first liquid crystal molecules of the second lens element with respect to a line passing through the center in a plan view;

[0007] (2) a first lens element having a lens effect of converting a first circularly polarized light of a first wavelength into a second circularly polarized light of an opposite rotation while focusing the light; a second lens element having a lens effect of converting a first circularly polarized light having a second wavelength different from the first wavelength into a second circularly polarized light having an opposite rotation while focusing the light; a third lens element having a lens effect of converting a first circularly polarized light having a third wavelength different from the first wavelength and the second wavelength into a second circularly polarized light having an opposite rotation while focusing the first circularly polarized light, When n is an integer greater than or equal to 1, the first lens element has a phase difference of (2n-1)π for the first wavelength and a phase difference of 2nπ for the second wavelength and the third wavelength; the second lens element has a phase difference of (2n-1)π for the second wavelength and a phase difference of 2nπ for the first wavelength and the third wavelength; the third lens element has a phase difference of (2n-1)π for the third wavelength and a phase difference of 2nπ for the first wavelength and the second wavelength; In the first to third lens elements, a phase difference for the second wavelength is smaller than a phase difference for the first wavelength, and a phase difference for the third wavelength is smaller than a phase difference for the second wavelength; Each of the first to third lens elements has a liquid crystal layer that is hardened in a state in which the alignment direction of a plurality of liquid crystal molecules, including first and second liquid crystal molecules, is fixed, the liquid crystal layer has, in a plan view, a first annular region in which a plurality of the first liquid crystal molecules are aligned in the same direction, and a second annular region outside the first annular region in which a plurality of the second liquid crystal molecules are aligned in the same direction; a circle surrounding the first annular region and a circle surrounding the second annular region have the same center; The alignment direction of the first liquid crystal molecules is different from the alignment direction of the second liquid crystal molecules.

[0008] (3) a first lens element having a lens action of focusing first circularly polarized light of a first wavelength while converting it into second circularly polarized light having a reverse rotation, focusing first circularly polarized light of a second wavelength different from the first wavelength while converting it into the second circularly polarized light having a reverse rotation, and focusing first circularly polarized light of a third wavelength different from the first wavelength and the second wavelength while converting it into the second circularly polarized light having a reverse rotation; a second lens element having a lens action of focusing the first circularly polarized light of the first wavelength while converting it into the second circularly polarized light, focusing the first circularly polarized light of the second wavelength while converting it into the second circularly polarized light, and diverging the second circularly polarized light of the third wavelength while converting it into the first circularly polarized light; a third lens element having a lens action of converging the first circularly polarized light of the first wavelength while converting it into the second circularly polarized light, diverging the second circularly polarized light of the second wavelength while converting it into the first circularly polarized light, and diverging the second circularly polarized light of the third wavelength while converting it into the first circularly polarized light; a first phase conversion element disposed between the first lens element and the second lens element, wherein, when n is an integer equal to or greater than 1, the first phase conversion element has a phase difference of (2n-1)π for the first wavelength and the second wavelength, and a phase difference of 2nπ for the third wavelength; a second phase conversion element disposed between the second lens element and the third lens element, the second phase conversion element having a phase difference of (2n-1)π for the first wavelength and the third wavelength, and a phase difference of 2nπ for the second wavelength; In the first phase change element and the second phase change element, a phase difference for the second wavelength is smaller than a phase difference for the first wavelength, and a phase difference for the third wavelength is smaller than a phase difference for the second wavelength; the first wavelength is shorter than the second wavelength, the second wavelength is shorter than the third wavelength, Each of the first to third lens elements has a liquid crystal layer that is hardened in a state in which the alignment direction of a plurality of liquid crystal molecules, including first and second liquid crystal molecules, is fixed, the liquid crystal layer has, in a plan view, a first annular region in which a plurality of the first liquid crystal molecules are aligned in the same direction, and a second annular region outside the first annular region in which a plurality of the second liquid crystal molecules are aligned in the same direction; a circle surrounding the first annular region and a circle surrounding the second annular region have the same center; The alignment direction of the first liquid crystal molecules is different from the alignment direction of the second liquid crystal molecules.

[0009] According to the embodiment, the following display device can be provided.

[0010] (4) a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; a reflective polarizer configured to transmit a first linearly polarized light and reflect a second linearly polarized light that is orthogonal to the first linearly polarized light; a second retardation plate disposed between the semi-transmissive layer and the reflective polarizer; The lens portion described in (1) above; a third retardation plate disposed between the reflective polarizer and the lens portion; Equipped with the lens portion is spaced from the reflective polarizer; The display device, wherein the first retardation plate, the second retardation plate, and the third retardation plate are quarter-wave plates.

[0011] (5) a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; The lens portion described in (1) above; a first selective reflection unit disposed between the semi-transmitting layer and the lens unit and spaced apart from the semi-transmitting layer; Equipped with the lens portion is spaced from the semi-transparent layer, the first retardation plate is a quarter wave plate, The first selective reflection portion is A display device comprising a first optical element having a first cholesteric liquid crystal layer that reflects first circularly polarized light of a first wavelength toward the semi-transparent layer and transmits second circularly polarized light of the first wavelength that is rotated in the opposite direction to the first circularly polarized light.

[0012] (6) a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; a reflective polarizer configured to transmit a first linearly polarized light and reflect a second linearly polarized light that is orthogonal to the first linearly polarized light; a second retardation plate disposed between the semi-transmissive layer and the reflective polarizer; The lens portion according to (2) or (3) above; a third retardation plate disposed between the reflective polarizer and the lens portion, the lens portion is spaced from the reflective polarizer; The display device, wherein the first retardation plate, the second retardation plate, and the third retardation plate are quarter-wave plates.

[0013] (7) a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; The lens portion according to (2) or (3) above; a first selective reflection unit disposed between the semi-transmitting layer and the lens unit and spaced apart from the semi-transmitting layer, the lens portion is spaced from the semi-transparent layer, the first retardation plate is a quarter wave plate, The first selective reflection portion is a first optical element including a first cholesteric liquid crystal layer that reflects first circularly polarized light of a first wavelength toward the semi-transmissive layer and transmits second circularly polarized light of the first wavelength that has an opposite rotation to the first circularly polarized light; a second optical element having a second cholesteric liquid crystal layer laminated on the first optical element, the second cholesteric liquid crystal layer reflecting first circularly polarized light of a second wavelength different from the first wavelength toward the semi-transmissive layer and transmitting second circularly polarized light of the second wavelength that has a rotation opposite to that of the first circularly polarized light; a third optical element stacked on the second optical element and having a third cholesteric liquid crystal layer that reflects first circularly polarized light of a third wavelength different from the first wavelength and the second wavelength toward the semi-transparent layer and transmits second circularly polarized light of the third wavelength that is rotated in the opposite direction to the first circularly polarized light. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a perspective view showing an example of the appearance of a head-mounted display 1 to which a display device according to an embodiment is applied. [Figure 2] FIG. 2 is a diagram for explaining an outline of the configuration of the head-mounted display 1 shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing a display device DSP according to a first embodiment. [Figure 4] FIG. 4 is a plan view showing an example of the lighting device 3 applicable to the display device DSP shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing a first configuration example of the lens unit 10 shown in FIG. [Figure 6] FIG. 6 is a diagram for explaining the lens function of first lens element 11 shown in FIG. [Figure 7] FIG. 7 is a diagram for explaining the lens action of second lens element 12 shown in FIG. [Figure 8] FIG. 8 is a diagram for explaining the lens action of first lens element 11 and second lens element 12 shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view showing an example of first lens element 11 and second lens element 12. As shown in FIG. [Figure 10] FIG. 10 is a diagram showing an example of the alignment pattern in the first liquid crystal layer LC11 and the second liquid crystal layer LC12 shown in FIG. [Figure 11] FIG. 11 is a diagram for explaining the wavelength characteristics of the liquid crystal layer that constitutes the lens element. [Figure 12] FIG. 12 is a diagram for explaining the optical action of the display device DSP. [Figure 13A] FIG. 13A is a cross-sectional view showing a second configuration example of the lens unit 10 shown in FIG. [Figure 13B] FIG. 13B is a cross-sectional view showing another example of the configuration of the lens unit 10 shown in FIG. [Figure 14] FIG. 14 is a diagram for explaining the lens action of the lens portion 10 shown in FIG. 13A. [Figure 15]FIG. 15 is a diagram for explaining the wavelength characteristics of the first phase conversion element PC1 and the second phase conversion element PC2. [Figure 16] FIG. 16 is a diagram for explaining the wavelength characteristics of the liquid crystal layer that constitutes the lens element. [Figure 17] FIG. 17 is a cross-sectional view showing a display device DSP according to a second embodiment. [Figure 18] FIG. 18 is a cross-sectional view showing an example of the configuration of the first selective reflecting portion 201 shown in FIG. [Figure 19] FIG. 19 is a cross-sectional view showing an example of the first optical element 21 shown in FIG. [Figure 20] FIG. 20 is a diagram for explaining the first optical element 21, the second optical element 22, and the third optical element 23 shown in FIG. [Figure 21] FIG. 21 is a diagram for explaining the optical action of the display device DSP. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present embodiment will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily make while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment for clarity of explanation, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are designated by the same reference numerals, and redundant detailed descriptions may be omitted as appropriate.

[0016] In the drawings, mutually perpendicular X-axis, Y-axis, and Z-axis are shown as necessary to facilitate understanding. 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 X-axis and Y-axis is referred to as the XY plane, and viewing the XY plane is referred to as planar view.

[0017] FIG. 1 is a perspective view showing an example of the appearance of a head-mounted display 1 to which a display device according to this embodiment is applied. The head mounted display 1 includes, for example, a display device DSPR for the right eye and a display device DSPL for the left eye. When a user wears the head mounted display 1 on his / her head, the display device DSPR is disposed so as to be located in front of the user's right eye, and the display device DSPL is disposed so as to be located in front of the user's left eye.

[0018] FIG. 2 is a diagram for explaining an outline of the configuration of the head-mounted display 1 shown in FIG. The display device DSPR is configured substantially similarly to the display device DSPL.

[0019] The display device DSPR includes a display panel 2R, an illumination device 3R, and an optical system 4R indicated by a dotted line. The illumination device 3R is disposed on the rear surface of the display panel 2R and is configured to illuminate the display panel 2R. The optical system 4R is disposed in front of the display panel 2R (or between the user's right eye ER and the display panel 2R) and is configured to guide display light from the display panel 2R to the right eye ER.

[0020] The display panel 2R includes, for example, a liquid crystal panel and a polarizing plate. The display panel 2R is disposed between the illumination device 3R and the optical system 4R. For example, a driver IC chip 5R and a flexible printed circuit board 6R are connected to the display panel 2R. The driver IC chip 5R controls the driving of the display panel 2R (particularly, controls the display operation of the display panel 2R).

[0021] The display device DSPL includes a display panel 2L, an illumination device 3L, and an optical system 4L indicated by dotted lines. The illumination device 3L is disposed on the rear surface of the display panel 2L and is configured to illuminate the display panel 2L. The optical system 4L is disposed in front of the display panel 2L (or between the user's left eye EL and the display panel 2L) and is configured to guide display light from the display panel 2L to the left eye EL.

[0022] The display panel 2L includes, for example, a liquid crystal panel and a polarizing plate. The display panel 2L is disposed between the illumination device 3L and the optical system 4L. For example, a driver IC chip 5L and a flexible printed circuit board 6L are connected to the display panel 2L. The driver IC chip 5L controls the driving of the display panel 2L (particularly, controls the display operation of the display panel 2L).

[0023] The display panel 2R, the illumination device 3R, and the optical system 4R that constitute the display device DSPR are configured in the same manner as the display panel 2L, the illumination device 3L, and the optical system 4L that constitute the display device DSPL, respectively.

[0024] In the display device DSP according to this embodiment, the display panels 2R and 2L are not limited to including liquid crystal panels, but may include display panels equipped with self-luminous light-emitting elements such as organic electroluminescence (EL) elements, micro LEDs, and mini LEDs. When the display panels are display panels equipped with light-emitting elements, the illumination devices 3R and 3L are omitted. As will be described in detail later, the display panels 2R and 2L are configured to emit linearly polarized display light and include polarizing plates as necessary.

[0025] An external host computer H is connected to the display panels 2L and 2R, respectively. The host computer H outputs image data corresponding to the images displayed on the display panels 2L and 2R. The image displayed on the display panel 2L is an image for the left eye (or an image viewed by the user's left eye EL). The image displayed on the display panel 2R is an image for the right eye (or an image viewed by the user's right eye ER).

[0026] For example, when the head mounted display 1 is used for VR, the image for the left eye and the image for the right eye are similar images that reproduce the parallax between the two eyes. When the image for the left eye displayed on the display panel 2L is viewed by the user's left eye EL and the image for the right eye displayed on the display panel 2R is viewed by the user's right eye ER, the user can perceive a stereoscopic space (three-dimensional space) as a virtual reality space.

[0027] Next, several examples of the display device DSP according to this embodiment will be described.

[0028] Example 1 FIG. 3 is a cross-sectional view showing a display device DSP according to a first embodiment. The display device DSP includes a display panel 2, an illumination device 3, and an optical system 4. The display device DSP described here can be applied to each of the above-mentioned display devices DSPR and DSPL. The display panel 2 can be applied to each of the above-mentioned display panels 2R and 2L. The illumination device 3 can be applied to each of the above-mentioned illumination devices 3R and 3L. The optical system 4 can be applied to each of the above-mentioned optical systems 4R and 4L.

[0029] The display panel 2 is formed in a flat plate shape extending across the XY plane. The display panel 2 includes a first substrate SUB1, a second substrate SUB2, a liquid crystal layer LC, a first polarizer PL1, and a second polarizer PL2. The liquid crystal layer LC is held between the first substrate SUB1 and the second substrate SUB2 and sealed with a seal SE. The first polarizer PL1 is disposed between the illumination device 3 and the first substrate SUB1. The second polarizer PL2 is disposed between the second substrate SUB2 and the optical system 4. The display area DA of the display panel 2 is configured to selectively modulate illumination light from the illumination device 3. A portion of the illumination light passes through the second polarizer PL2 and is converted into linearly polarized display light DL.

[0030] Not only in the first embodiment described here, but also in other embodiments, the display panel 2 is not limited to a liquid crystal panel. If the display panel 2 is a display panel equipped with self-luminous light-emitting elements, the illumination device 3 is omitted as described above. In this case, the display light DL emitted from the light-emitting elements passes through a polarizing plate and is converted into linearly polarized display light DL.

[0031] The optical system 4 includes a first structure 4A and a second structure 4B. The first structure 4A is spaced apart from the second structure 4B. In the example shown in Fig. 3, an air layer 4C is provided between the first structure 4A and the second structure 4B. The first structure 4A is disposed between the display panel 2 and the second structure 4B (or between the display panel 2 and the air layer 4C).

[0032] The first structure 4A includes a first retardation plate R1, a semi-transmitting layer HM, and a second retardation plate R2. The first retardation plate R1 and the second retardation plate R2 are quarter-wave plates that impart a phase difference of a quarter wavelength to transmitted light. The semi-transmitting layer HM transmits a portion of incident light and reflects the remaining light. As an example, the semi-transmitting layer HM is a thin film made of a metal material such as aluminum or silver. The transmittance of the semi-transmitting layer HM is approximately 50%.

[0033] The first retardation plate R1, the semi-transmitting layer HM, and the second retardation plate R2 extend over an area wider than the display area DA in the XY plane. The first retardation plate R1, the semi-transmitting layer HM, and the second retardation plate R2 are laminated in this order along the third direction Z. The first retardation plate R1 is in contact with the display panel 2 (or the second polarizer PL2), the semi-transmitting layer HM is in contact with the first retardation plate R1, and the second retardation plate R2 is in contact with the semi-transmitting layer HM. The first retardation plate R1 is disposed between the display panel 2 and the semi-transmitting layer HM, and the semi-transmitting layer HM is disposed between the first retardation plate R1 and the second retardation plate R2.

[0034] The second structure 4B includes a reflective polarizer PR, a third retardation plate R3, and a lens unit 10. The reflective polarizer PR transmits a first linearly polarized light of incident light and reflects a second linearly polarized light that is orthogonal to the first linearly polarized light. As an example, the reflective polarizer PR is a multilayer thin film type or a wire grid type. The third retardation plate R3 is a quarter-wave plate that imparts a phase difference of a quarter wavelength to the transmitted light.

[0035] The lens unit 10 includes a plurality of lens elements, the details of which will be described later. Each lens element imparts a phase difference of 1 / 2 wavelength to light of a specific wavelength, and has a lens effect of converging or diverging either the first circularly polarized light or the second circularly polarized light. The second circularly polarized light is circularly polarized in the opposite direction to the first circularly polarized light.

[0036] The reflective polarizer PR, the third retardation plate R3, and the lens unit 10 extend over an area wider than the display area DA in the XY plane. The reflective polarizer PR, the third retardation plate R3, and the lens unit 10 are laminated in this order along the third direction Z. The third retardation plate R3 is in contact with the reflective polarizer PR, the lens unit 10 is in contact with the third retardation plate R3, the second retardation plate R2 is disposed between the semi-transmitting layer HM and the reflective polarizer PR, and the third retardation plate R3 is disposed between the reflective polarizer PR and the lens unit 10. The reflective polarizer PR is spaced apart from the second retardation plate R2 and faces the second retardation plate R2 in the third direction Z via an air layer 4C.

[0037] It is desirable that the display panel 2 and the first retarder R1 are in close contact with each other without an air gap therebetween. It is also desirable that the first retarder R1, the semi-transmissive layer HM, and the second retarder R2 constituting the first structure 4A are in close contact with each other without an air gap therebetween. It is also desirable that the reflective polarizer PR, the third retarder R3, and the lens unit 10 constituting the second structure 4B are in close contact with each other without an air gap therebetween. This makes it possible to suppress undesired reflection or refraction at the interfaces between the components.

[0038] The first retarder R1, the second retarder R2, and the third retarder R3 may, for example, impart a quarter-wave retardation to at least green wavelength light, but are not limited thereto. For example, the first retarder R1, the second retarder R2, and the third retarder R3 may be broadband retarders that impart approximately a quarter-wave retardation to red, green, and blue wavelength light as well. Such broadband retarders may include, for example, a quarter-wave plate and a half-wave plate bonded together such that the slow axes of the quarter-wave plate and the half-wave plate form a predetermined angle. This reduces the wavelength dependency of the first retarder R1, the second retarder R2, and the third retarder R3.

[0039] FIG. 4 is a plan view showing an example of the lighting device 3 applicable to the display device DSP shown in FIG. 4, only the main part of the lighting device 3 is shown.

[0040] The lighting device 3 includes a light guide plate LG and a plurality of light emitting elements LD. The plurality of light emitting elements LD face a side surface LGS of the light guide plate LG in the first direction or the second direction. The light emitting elements LD include a first light emitting element LD1 that emits light of a first wavelength, a second light emitting element LD2 that emits light of a second wavelength, and a third light emitting element LD3 that emits light of a third wavelength. The first light emitting element LD1, the second light emitting element LD2, and the third light emitting element LD3 are arranged at intervals. The first wavelength, the second wavelength, and the third wavelength are different from one another. In one example, the first wavelength corresponds to a blue wavelength B, the second wavelength corresponds to a green wavelength G, and the third wavelength corresponds to a red wavelength R, but this example is not limiting.

[0041] It is desirable that the light emitted from the light-emitting element LD has a narrow spectral width (or high color purity). For this reason, it is desirable to use a laser light source as the light-emitting element LD. The central wavelength of the blue laser light emitted from the first light-emitting element (first laser element) LD1 is λb, the central wavelength of the green laser light emitted from the second light-emitting element (second laser element) LD2 is λg, and the central wavelength of the red laser light emitted from the third light-emitting element (third laser element) LD3 is λr.

[0042] The illumination device 3 is not limited to the configuration shown in FIG. 4, and may be a direct illumination device including a plurality of light-emitting elements LD facing the display panel in the third direction.

[0043] <<First example of lens configuration>> FIG. 5 is a cross-sectional view showing a first configuration example of the lens unit 10 shown in FIG. Lens unit 10 includes a first lens element 11 having a first liquid crystal layer LC11, a second lens element 12 having a second liquid crystal layer LC12, a third lens element 13 having a third liquid crystal layer LC13, a fourth lens element 14 having a fourth liquid crystal layer LC14, a fifth lens element 15 having a fifth liquid crystal layer LC15, and a sixth lens element 16 having a sixth liquid crystal layer LC16.

[0044] In one example, first lens element 11 faces third retardation plate R3 in third direction Z. Furthermore, first lens element 11, second lens element 12, third lens element 13, fourth lens element 14, fifth lens element 15, and sixth lens element 16 are stacked in this order along third direction Z, but the stacking order may be different from that in the illustrated example.

[0045] First lens element 11 and second lens element 12 impart a phase difference of 1 / 2 wavelength to light of the first wavelength, and have a lens action of converging or diverging either the first circularly polarized light or the second circularly polarized light of the first wavelength. For example, first lens element 11 has a lens effect of converting first circularly polarized light B1 of a first wavelength (e.g., blue wavelength B) that has passed through third retardation plate R3 into second circularly polarized light B2 of the first wavelength, while converging this second circularly polarized light B2. Furthermore, second lens element 12 has a lens effect of converting second circularly polarized light B2 that has passed through first lens element 11 into first circularly polarized light B1, while converging this first circularly polarized light B1.

[0046] The third lens element 13 and the fourth lens element 14 impart a phase difference of 1 / 2 wavelength to the light of the second wavelength, and have a lens action of converging or diverging either the first circularly polarized light or the second circularly polarized light of the second wavelength. For example, third lens element 13 has a lens effect of converting first circularly polarized light G1 of a second wavelength (e.g., green wavelength G) that has passed through third retardation plate R3 into second circularly polarized light G2 of the second wavelength, while converging this second circularly polarized light G2. Furthermore, fourth lens element 14 has a lens effect of converting second circularly polarized light G2 that has passed through third lens element 13 into first circularly polarized light G1, while converging this first circularly polarized light G1.

[0047] Fifth lens element 15 and sixth lens element 16 impart a phase difference of 1 / 2 wavelength to light of the third wavelength, and have a lens action of converging or diverging either the first circularly polarized light or the second circularly polarized light of the third wavelength. For example, fifth lens element 15 has a lens action of converting first circularly polarized light R1 of a third wavelength (e.g., red wavelength R) that has passed through third retardation plate R3 into second circularly polarized light R2 of the third wavelength, while focusing this second circularly polarized light R2. Furthermore, sixth lens element 16 has a lens action of converting second circularly polarized light R2 that has passed through fifth lens element 15 into first circularly polarized light R1, while focusing this first circularly polarized light R1.

[0048] FIG. 6 is a diagram for explaining the lens function of first lens element 11 shown in FIG. First lens element 11 has first upper surface 11A and first lower surface 11B. Here, a case will be described in which first circularly polarized light B1 and second circularly polarized light B2 of a first wavelength are transmitted from first upper surface 11A to first lower surface 11B.

[0049] As shown on the left side of Figure 6, when first circularly polarized light B1 is incident on first lens element 11, first lens element 11 has a positive focal length f1, and the light transmitted through first lens element 11 is converted into second circularly polarized light B2 and focused. As shown on the right side of Figure 6, when second circularly polarized light B2 is incident on first lens element 11, first lens element 11 has a negative focal length f1, and the light transmitted through first lens element 11 is converted into first circularly polarized light B1 and diverged.

[0050] The configuration of second lens element 12 is substantially the same as the configuration of first lens element 11. That is, second lens element 12 also exhibits a lens action similar to that shown in FIG. 6 when first circularly polarized light B1 and second circularly polarized light B2 of the first wavelength are transmitted from second upper surface 12A to second lower surface 12B.

[0051] FIG. 7 is a diagram for explaining the lens action of second lens element 12 shown in FIG. Second lens element 12 has second upper surface 12A and second lower surface 12B. Here, a case will be described in which first circularly polarized light B1 and second circularly polarized light B2 of a first wavelength are transmitted from second lower surface 12B toward second upper surface 12A. In other words, second lens element 12 shown in Fig. 7 corresponds to first lens element 11 shown in Fig. 6 with the front and back reversed.

[0052] As shown on the left side of Figure 7, when second circularly polarized light B2 is incident on second lens element 12, second lens element 12 has a positive focal length f2, and the light transmitted through second lens element 12 is converted to first circularly polarized light B1 and focused. As shown on the right side of Figure 7, when first circularly polarized light B1 is incident on second lens element 12, second lens element 12 has a negative focal length f2, and the light transmitted through second lens element 12 is converted into second circularly polarized light B2 and diverged.

[0053] FIG. 8 is a diagram for explaining the lens action of first lens element 11 and second lens element 12 shown in FIG. The first lens element 11 and the second lens element 12 are aligned in the light propagation direction. The first lower surface 11B faces the second lower surface 12B. The composite focal length fs of the first lens element 11 and the second lens element 12 can be expressed by equation (1) shown in the figure based on the positive focal length f1 of the first lens element 11, the positive focal length f2 of the second lens element 12, and the inter-lens distance d between the first lens element 11 and the second lens element 12. In other words, when the focal length f1 is equal to the focal length f2 and the inter-lens distance d is extremely small, the composite focal length fs is approximately half the focal length f1. This means that the focal length can be shortened by combining the first lens element 11 and the second lens element 12 compared to when the first lens element 11 is used alone.

[0054] As described above, the combination of the first lens element 11 and the second lens element 12 has been described with reference to Figures 6 to 8, but the combination of the third lens element 13 and the fourth lens element 14, and the combination of the fifth lens element 15 and the sixth lens element 16 also exhibit the same lens action as the combination of the first lens element 11 and the second lens element 12.

[0055] In other words, fourth lens element 14 is equivalent to the front and back of third lens element 13. As a result, the focal length can be shortened by combining third lens element 13 and fourth lens element 14 compared to when third lens element 13 is used alone. Additionally, sixth lens element 16 corresponds to fifth lens element 15 with the front and back reversed. As a result, the focal length can be shortened by combining fifth lens element 15 and sixth lens element 16 compared to when fifth lens element 15 is used alone.

[0056] FIG. 9 is a cross-sectional view showing an example of first lens element 11 and second lens element 12. As shown in FIG. Here, we will explain the first liquid crystal layer LC11 of first lens element 11 and the second liquid crystal layer LC12 of second lens element 12. Note that each of first lens element 11 and second lens element 12 may include a transparent substrate and an alignment film, but illustration and explanation thereof will be omitted here.

[0057] The first liquid crystal layer LC11 and the second liquid crystal layer LC12 each have the same thickness d along the third direction Z. The first liquid crystal layer LC11 and the second liquid crystal layer LC12 each contain nematic liquid crystals whose alignment direction is aligned along the third direction Z.

[0058] Each of the first liquid crystal layer LC11 and the second liquid crystal layer LC12 has a plurality of liquid crystal structures LS1. Focusing on one liquid crystal structure LS1, the liquid crystal structure LS1 has a liquid crystal molecule LM11 located at one end and a liquid crystal molecule LM12 located at the other end. The alignment direction of the liquid crystal molecule LM11 and the alignment direction of the liquid crystal molecule LM12 are substantially the same. Furthermore, the alignment direction of the other liquid crystal molecule LM1 between the liquid crystal molecule LM11 and the liquid crystal molecule LM12 is also substantially the same as the alignment direction of the liquid crystal molecule LM11. Note that the alignment direction of the liquid crystal molecule LM1 here corresponds to the direction of the long axis of the liquid crystal molecule in the XY plane.

[0059] Furthermore, the alignment directions of the liquid crystal structures LS1 adjacent to each other along the first direction X are different from each other. Similarly, the alignment directions of the liquid crystal structures LS1 adjacent to each other along the second direction Y are also different from each other. The alignment directions of the liquid crystal molecules LM11 aligned along the first direction X change continuously (or linearly).

[0060] Each of the first liquid crystal layer LC11 and the second liquid crystal layer LC12 is cured in a state in which the alignment direction of the liquid crystal molecules LM1, which include liquid crystal molecules LM11 and LM12, is fixed. In other words, the alignment direction of the liquid crystal molecules LM1 is not controlled in response to an electric field. Similarly, each of the third liquid crystal layer LC13 of the third lens element 13, the fourth liquid crystal layer LC14 of the fourth lens element 14, the fifth liquid crystal layer LC15 of the fifth lens element 15, and the sixth liquid crystal layer LC16 of the sixth lens element 16 is cured in a state in which the alignment direction of the liquid crystal molecules LM1, which include liquid crystal molecules LM11 and LM12, is fixed, similar to the first liquid crystal layer LC11. Therefore, first lens element 11, second lens element 12, third lens element 13, fourth lens element 14, fifth lens element 15, and sixth lens element 16 do not have electrodes for orientation control.

[0061] For each of the first liquid crystal layer LC11, the second liquid crystal layer LC12, the third liquid crystal layer LC13, the fourth liquid crystal layer LC14, the fifth liquid crystal layer LC15, and the sixth liquid crystal layer LC16, when the refractive index anisotropy or birefringence (the difference between the refractive index ne for extraordinary light and the refractive index no for ordinary light) is Δn and the thickness is d, the phase difference Γ is set to be equivalent to 1 / 2 of the specific wavelength λ. That is, the phase difference Γ is defined by the following equation: Γ=(2π / λ)·(Δn·d)=π …(2) For example, when the central wavelength λb of the blue laser light emitted from the first light-emitting element LD1 is defined as the first wavelength, the phase difference Γ of each of the first liquid crystal layer LC11 and the second liquid crystal layer LC12 is set to be equivalent to ½ of the wavelength λb. Similarly, when the central wavelength λg of the green laser light emitted from the second light-emitting element LD2 is defined as the second wavelength, the phase difference Γ of each of the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 is set to be equivalent to 1 / 2 of the wavelength λg. Furthermore, when the central wavelength λr of the red laser light emitted from the third light-emitting element LD3 is defined as a third wavelength, the phase difference Γ of each of the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 is set to correspond to ½ of the wavelength λr.

[0062] The first liquid crystal layer LC11 and the second liquid crystal layer LC12 have the same refractive index anisotropy Δn and thickness d, the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 have the same refractive index anisotropy Δn and thickness d, and the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 have the same refractive index anisotropy Δn and thickness d. However, the first liquid crystal layer LC11, the third liquid crystal layer LC13, and the fifth liquid crystal layer LC15 may have different refractive index anisotropies Δn. Furthermore, the first liquid crystal layer LC11, the third liquid crystal layer LC13, and the fifth liquid crystal layer LC15 may have different thicknesses d.

[0063] FIG. 10 is a diagram showing an example of the alignment pattern in the first liquid crystal layer LC11 and the second liquid crystal layer LC12 shown in FIG. 10 shows an example of the spatial phase in the XY plane of each of the first liquid crystal layer LC11 and the second liquid crystal layer LC12. The spatial phase shown here is shown as the alignment direction of the liquid crystal molecules LM1 included in the liquid crystal structure LS1.

[0064] The spatial phases of the concentric circles indicated by dotted lines in the figure are uniform. Alternatively, the alignment directions of the liquid crystal molecules LM1 are uniform in the annular regions surrounded by two adjacent concentric circles. However, the alignment directions of the liquid crystal molecules LM1 in the adjacent annular regions are different from each other.

[0065] For example, the first liquid crystal layer LC11 has a first annular region C1 and a second annular region C2 in the XY plane. The second annular region C2 is located outside the first annular region C1. The first annular region C1 is composed of a plurality of first liquid crystal molecules LM111 aligned in the same direction. The second annular region C2 is composed of a plurality of second liquid crystal molecules LM112 aligned in the same direction. The alignment direction of the first liquid crystal molecules LM111 is different from the alignment direction of the second liquid crystal molecules LM112.

[0066] The alignment directions of the liquid crystal molecules LM1 aligned in the radial direction from the center O of the concentric circle are different from each other and change continuously. That is, in the illustrated XY plane, the spatial phase of the first liquid crystal layer LC11 differs along the radial direction and changes continuously.

[0067] Similarly, the second liquid crystal layer LC12 has a first annular region C1 and a second annular region C2 in the XY plane. The second annular region C2 is located outside the first annular region C1. The first annular region C1 is composed of a plurality of first liquid crystal molecules LM111 aligned in the same direction. The second annular region C2 is composed of a plurality of second liquid crystal molecules LM112 aligned in the same direction. The alignment direction of the first liquid crystal molecules LM111 is different from the alignment direction of the second liquid crystal molecules LM112.

[0068] The alignment directions of the liquid crystal molecules LM1 aligned in the radial direction from the center O of the concentric circle are different from each other and change continuously. That is, in the illustrated XY plane, the spatial phase of the second liquid crystal layer LC12 differs along the radial direction and changes continuously.

[0069] Focusing on the relationship between the first liquid crystal layer LC11 and the second liquid crystal layer LC12, the first annular region C1 of the second liquid crystal layer LC12 overlaps the first annular region C1 of the first liquid crystal layer LC11 in the third direction Z. The second annular region C2 of the second liquid crystal layer LC12 overlaps the second annular region C2 of the first liquid crystal layer LC11 in the third direction Z. The center O of a circle surrounding the first annular region C1 and the second annular region C2 in the second liquid crystal layer LC12 overlaps the center O of a circle surrounding the first annular region C1 and the second annular region C2 in the first liquid crystal layer LC11 in the third direction Z.

[0070] However, the first liquid crystal molecules LM111 in the first annular region C1 of the second liquid crystal layer LC12 are aligned in a different direction in the XY plane from the first liquid crystal molecules LM111 in the first annular region C1 of the first liquid crystal layer LC11. Also, the second liquid crystal molecules LM112 in the second annular region C2 of the second liquid crystal layer LC12 are aligned in a different direction in the XY plane from the second liquid crystal molecules LM112 in the second annular region C2 of the first liquid crystal layer LC11.

[0071] The alignment direction of the first liquid crystal molecules LM111 in the second liquid crystal layer LC12 is symmetrical to the alignment direction of the first liquid crystal molecules LM111 in the first liquid crystal layer LC11 in the XY plane with respect to a line OL passing through the center O. Furthermore, the alignment direction of the second liquid crystal molecules LM112 in the second liquid crystal layer LC12 is symmetrical to the alignment direction of the second liquid crystal molecules LM112 in the first liquid crystal layer LC11 in the XY plane with respect to the line OL.

[0072] In this way, the first liquid crystal layer LC11 of the first lens element 11 described in Figures 9 and 10 exhibits a lens action with a focal length f1 as described with reference to Figure 6, and the second liquid crystal layer LC12 of the second lens element 12 exhibits a lens action with a focal length f2 as described with reference to Figure 7.

[0073] Now, let us focus on the first liquid crystal layer LC11. For simplicity, let us denote the focal length as f, the radius from the center O in the XY plane as r, and the tilt of the liquid crystal molecule LM1 at the position of radius r from the center O as θ(r), then the relationship in equation (3) in the figure holds. In other words, the focal length f does not depend on the phase difference, but varies depending on the wavelength λ.

[0074] In other words, even if the first liquid crystal layer LC11 is configured to exhibit a lens action with a focal length f for light of the first wavelength, in some cases it may exhibit a lens action with a focal length different from the focal length f for light of the second wavelength and the third wavelength. For this reason, while the first liquid crystal layer LC11 exhibits a lens action with a focal length f for light of the first wavelength, it exhibits almost no lens action for light of the second wavelength and the third wavelength. This will be described in detail with reference to FIG. 11.

[0075] Like the first liquid crystal layer LC11, the third liquid crystal layer LC13, the fourth liquid crystal layer LC14, the fifth liquid crystal layer LC15, and the sixth liquid crystal layer LC16 also have multiple annular regions in which the alignment direction of the liquid crystal molecules is aligned, and the alignment directions of the liquid crystal molecules in adjacent annular regions are different from each other.

[0076] The orientation pattern of the liquid crystal molecules LM1 in the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 is set based on equation (3) in the figure so as to exhibit a lens action with a focal length f for light of the second wavelength. Furthermore, the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 exhibit almost no lens action for light of the first wavelength and the third wavelength. More specifically, this will be described with reference to FIG. 11.

[0077] The orientation pattern of the liquid crystal molecules LM1 in the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 is set based on equation (3) in the figure so as to exert a lens action with a focal length f for light of the third wavelength. Furthermore, the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 exert almost no lens action for light of the first wavelength and the second wavelength. More specifically, this will be described with reference to FIG. 11.

[0078] FIG. 11 is a diagram for explaining the wavelength characteristics of the liquid crystal layer that constitutes the lens element. The upper part of Fig. 11 shows wavelength characteristics of the first liquid crystal layer LC11 and the second liquid crystal layer LC12 that are suitable for the first wavelength (blue wavelength: 450 nm). The middle part of Fig. 11 shows wavelength characteristics of the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 that are suitable for the second wavelength (green wavelength: 530 nm). The lower part of Fig. 11 shows wavelength characteristics of the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 that are suitable for the third wavelength (red wavelength: 630 nm).

[0079] In each graph showing wavelength characteristics, the horizontal axis is wavelength (nm) and the vertical axis is Δn·d (nm).

[0080] As described above, the first liquid crystal layer LC11 and the second liquid crystal layer LC12 are required to exhibit a lens action with a focal length f for light of the first wavelength, and to exhibit almost no lens action for light of the second and third wavelengths. The third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 are required to exhibit a lens action with a focal length f for light of the second wavelength, and to exhibit almost no lens action for light of the first wavelength and third wavelength. The fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 are required to exhibit a lens action with a focal length f for light of the third wavelength, and to exhibit almost no lens action for light of the first wavelength and second wavelength.

[0081] As explained in the above formula (2), when the phase difference Γ satisfies the condition of π or (2n-1)π, each of the first liquid crystal layer LC11, the second liquid crystal layer LC12, the third liquid crystal layer LC13, the fourth liquid crystal layer LC14, the fifth liquid crystal layer LC15, and the sixth liquid crystal layer LC16 exhibits a desired lens action, where n is an integer greater than or equal to 1. On the other hand, when the phase difference Γ satisfies the condition of 2π or 2nπ, each of the first liquid crystal layer LC11, the second liquid crystal layer LC12, the third liquid crystal layer LC13, the fourth liquid crystal layer LC14, the fifth liquid crystal layer LC15, and the sixth liquid crystal layer LC16 exhibits almost no lens action.

[0082] Therefore, the first liquid crystal layer LC11 and the second liquid crystal layer LC12 are configured to have a phase difference of (2n-1)π for the first wavelength and a phase difference of 2nπ for the second and third wavelengths. In the example shown in the upper part of FIG. 11 , the first liquid crystal layer LC11 and the second liquid crystal layer LC12 have a phase difference of 9π for the first wavelength (Δn·d=2025 nm), a phase difference of 6π for the second wavelength (Δn·d=1590 nm), and a phase difference of 4π for the third wavelength (Δn·d=1260 nm). The phase difference for the second wavelength is smaller than the phase difference for the first wavelength, and the phase difference for the third wavelength is smaller than the phase difference for the second wavelength. In other words, the wavelength characteristics of the first liquid crystal layer LC11 and the second liquid crystal layer LC12 are such that the phase difference monotonically decreases as the wavelength increases. The first liquid crystal layer LC11 and the second liquid crystal layer LC12 having such wavelength characteristics can be easily fabricated.

[0083] The third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 are configured to have a phase difference of (2n-1)π with respect to the second wavelength and a phase difference of 2nπ with respect to the first wavelength and the third wavelength. In the example shown in the middle of FIG. 11, the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 have a phase difference of 6π with respect to the first wavelength (Δn·d=1350 nm), a phase difference of 3π with respect to the second wavelength (Δn·d=795 nm), and a phase difference of 2π with respect to the third wavelength (Δn·d=630 nm). The phase difference with respect to the second wavelength is smaller than the phase difference with respect to the first wavelength, and the phase difference with respect to the third wavelength is smaller than the phase difference with respect to the second wavelength. In other words, the wavelength characteristics of the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 are such that the phase difference monotonically decreases as the wavelength increases. The third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 having such wavelength characteristics can also be easily fabricated.

[0084] The fifth and sixth liquid crystal layers LC15 and LC16 are configured to have a phase difference of (2n-1)π with respect to the third wavelength and a phase difference of 2nπ with respect to the first and second wavelengths. In the example shown in the lower part of FIG. 11 , the fifth and sixth liquid crystal layers LC15 and LC16 have a phase difference (Δn·d=1350 nm) corresponding to 6π with respect to the first wavelength, a phase difference (Δn·d=1060 nm) corresponding to 4π with respect to the second wavelength, and a phase difference (Δn·d=945 nm) corresponding to 3π with respect to the third wavelength. The phase difference with respect to the second wavelength is smaller than the phase difference with respect to the first wavelength, and the phase difference with respect to the third wavelength is smaller than the phase difference with respect to the second wavelength. In other words, the wavelength characteristics of the fifth and sixth liquid crystal layers LC15 and LC16 are such that the phase difference monotonically decreases as the wavelength increases. Fifth and sixth liquid crystal layers LC15 and LC16 having such wavelength characteristics can also be easily fabricated.

[0085] 11 is an example, and it is sufficient if the phase difference monotonically decreases with increasing wavelength. For example, the first liquid crystal layer LC11 and the second liquid crystal layer LC12 may be configured to have a phase difference corresponding to 7π or 5π for the first wavelength, a phase difference corresponding to 4π for the second wavelength, and a phase difference corresponding to 2π for the third wavelength.

[0086] As a result, the first liquid crystal layer LC11 and the second liquid crystal layer LC12 can focus light of the first wavelength at a position with a focal length f, the third liquid crystal layer LC13 and the fourth liquid crystal layer LC14 can focus light of the second wavelength at a position with a focal length f, and the fifth liquid crystal layer LC15 and the sixth liquid crystal layer LC16 can focus light of the third wavelength at a position with a focal length f.

[0087] By applying the first configuration example of the lens section 10 described above with reference to Figures 5 to 11, the focal length f can be made to match for each of the light of the first wavelength, the second wavelength, and the third wavelength.

[0088] FIG. 12 is a diagram for explaining the optical action of the display device DSP. Here, the optical action on the light of the first wavelength out of the display light DL emitted from the display panel 2 will be described, and also the lens action of the first lens element 11 and the second lens element 12 of the lens portion 10 will be described.

[0089] First, the display panel 2 emits display light DL as first linearly polarized light LP1. Here, the first linearly polarized light LP1 is, for example, linearly polarized light that vibrates in a direction perpendicular to the paper surface. When the display light DL passes through the first retardation plate R1, a phase difference of 1 / 4 wavelength is imparted to the display light DL. As a result, the display light DL is converted into first circularly polarized light CP1 after passing through the first retardation plate R1. Here, the first circularly polarized light CP1 is, for example, left-handed circularly polarized light.

[0090] Of the first circularly polarized light CP1 that passes through the first retardation plate R1, a portion of the first circularly polarized light CP1 passes through the semi-transmitting layer HM, while the other portion is reflected by the semi-transmitting layer HM. When the first circularly polarized light CP1 that passes through the semi-transmitting layer HM passes through the second retardation plate R2, a phase difference of ¼ wavelength is imparted to the first circularly polarized light CP1, and the first circularly polarized light CP1 is converted into second linearly polarized light LP2. The second linearly polarized light LP2 here is linearly polarized light that vibrates in a direction perpendicular to the first linearly polarized light LP1, that is, in a direction parallel to the plane of the paper.

[0091] When the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM, it is converted into second circularly polarized light CP2, which has a rotation opposite to that of the first circularly polarized light CP1. Here, the second circularly polarized light CP2 is, for example, clockwise circularly polarized light. The second circularly polarized light CP2 reflected by the semi-transmitting layer HM passes through the first retardation plate R1 and is converted into second linearly polarized light LP2, which is then absorbed by the display panel 2.

[0092] The second linearly polarized light LP2 that has passed through the second retardation plate R2 is reflected by the reflective polarizer PR, and the second linearly polarized light LP2 that has been reflected by the reflective polarizer PR passes through the second retardation plate R2 and is converted into the first circularly polarized light CP1.

[0093] Of the first circularly polarized light CP1 that has passed through the second retardation plate R2, some of the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM, while the other first circularly polarized light CP1 passes through the semi-transmitting layer HM. When the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM, it is converted into second circularly polarized light CP2. The second circularly polarized light CP2 that has been reflected by the semi-transmitting layer HM passes through the second retardation plate R2 and is converted into first linearly polarized light LP1. The first circularly polarized light CP1 that has passed through the semi-transmissive layer HM passes through the first retardation plate R1 and is converted into first linearly polarized light LP1.

[0094] The first linearly polarized light LP1 that has passed through the second retardation plate R2 passes through the reflective polarizer PR and is further converted into the first circularly polarized light CP1 by passing through the third retardation plate R3. The first circularly polarized light CP1 that has passed through the third retardation plate R3 is converted into the second circularly polarized light CP2 by the first lens element 11 of the lens unit 10 and is focused by the lens action. The second circularly polarized light that has passed through the first lens element 11 is further converted into the first circularly polarized light CP1 by the second lens element 12 and is focused on the user's pupil E by the lens action.

[0095] Furthermore, the light of the second wavelength out of the display light DL, like the light of the first wavelength, is focused onto the user's pupil E by the lens action of the third lens element 13 and the fourth lens element 14 of the lens unit 10. The light of the third wavelength out of the display light DL, like the light of the first wavelength, is also focused onto the user's pupil E by the lens action of the fifth lens element 15 and the sixth lens element 16 of the lens unit 10.

[0096] In such a display device DSP, the optical system 4 has an optical path that passes three times between the semi-transmitting layer HM and the reflective polarizer PR. That is, in the optical system 4, the optical distance between the semi-transmitting layer HM and the reflective polarizer PR is approximately three times the actual distance between the semi-transmitting layer HM and the reflective polarizer PR (or the thickness of the air layer 4C). The display panel 2 is installed inside the focal point of the lens unit 10, which has a lens function. This allows the user to view a magnified virtual image.

[0097] Furthermore, the illumination device 3 includes a laser light source that emits light with a narrow spectral width, and the focal length of each lens element of the lens unit 10 is optimized to match the central wavelength of the light emitted from the laser light source. This allows the light of the first wavelength, second wavelength, and third wavelength to be focused efficiently at the same focal length, allowing the user to view a clear image.

[0098] Furthermore, compared to optical systems that include optical components formed of glass, resin, or the like, the thickness along the third direction Z can be made thinner, and weight can be reduced.

[0099] The first linearly polarized light LP1 described with reference to FIG. 12 may be replaced with the second linearly polarized light LP2, and the first circularly polarized light CP1 may be replaced with the second circularly polarized light CP2.

[0100] <<Second example of lens configuration>> FIG. 13A is a cross-sectional view showing a second configuration example of the lens unit 10 shown in FIG. The lens unit 10 includes a first lens element 111 having a first liquid crystal layer LC111, a second lens element 112 having a second liquid crystal layer LC112, a third lens element 113 having a third liquid crystal layer LC113, a first phase conversion element PC1 arranged between the first lens element 111 and the second lens element 112, and a second phase conversion element PC2 arranged between the second lens element 112 and the third lens element 113.

[0101] In one example, first lens element 111 faces third retardation plate R3 in third direction Z. Furthermore, first lens element 111, first phase conversion element PC1, second lens element 112, second phase conversion element PC2, and third lens element 113 are stacked in this order along third direction Z.

[0102] Each of first lens element 111, second lens element 112, and third lens element 113 in the second configuration example has a lens action of, for example, converging first circularly polarized light while converting it into second circularly polarized light, and diverging second circularly polarized light while converting it into the first circularly polarized light, similar to first lens element 11 in the first configuration example described with reference to Fig. 6. First liquid crystal layer LC111 of first lens element 111, second liquid crystal layer LC112 of second lens element 112, and third liquid crystal layer LC113 of third lens element 113 are configured similarly to first liquid crystal layer LC11 described with reference to Figs. 9 and 10. This allows each of first lens element 111, second lens element 112, and third lens element 113 to exhibit its lens action.

[0103] The first phase conversion element PC1 and the second phase conversion element PC2 control the rotation direction of the circularly polarized light for each wavelength.

[0104] FIG. 14 is a diagram for explaining the lens action of the lens portion 10 shown in FIG. 13A. First lens element 111 has a phase difference of π or (2n-1)π for light of a first wavelength (blue wavelength) B, a second wavelength (green wavelength) G, and a third wavelength (red wavelength) R, respectively. First lens element 111 has a lens action of focusing first circularly polarized light B1 of the first wavelength B while converting it into second circularly polarized light B2, focusing first circularly polarized light G1 of the second wavelength G while converting it into second circularly polarized light G2, and focusing first circularly polarized light R1 of the third wavelength R while converting it into second circularly polarized light R2. The focal length f1B for light of the first wavelength B is greater than the focal length f1G for light of the second wavelength G, and the focal length f1G for light of the second wavelength G is greater than the focal length f1R for light of the third wavelength R (f1B>f1G>f1R).

[0105] The first phase conversion element PC1 has a phase difference of π or (2n-1)π for the light of the first wavelength B and the second wavelength G, respectively, and a phase difference of 2π or 2nπ for the light of the third wavelength R. Therefore, the first phase conversion element PC1 converts the second circularly polarized light B2 that has passed through the first lens element 111 into the first circularly polarized light B1, converts the second circularly polarized light G2 into the first circularly polarized light G1, and maintains the polarization state of the second circularly polarized light R2.

[0106] Second lens element 112 has a phase difference of π or (2n-1)π for light of the first wavelength B, second wavelength G, and third wavelength R, respectively. Second lens element 112 has a lens action of focusing first circularly polarized light B1 that has passed through first phase conversion element PC1 while converting it to second circularly polarized light B2, focusing first circularly polarized light G1 while converting it to second circularly polarized light G2, and diverging second circularly polarized light R2 while converting it to first circularly polarized light R1. The focal length f2B for light of the first wavelength B is greater than the focal length f2G for light of the second wavelength G, and the focal length f2G for light of the second wavelength G is greater than the focal length f2R (absolute value) for light of the third wavelength R (f2B>f2G>f2R).

[0107] The second phase conversion element PC2 has a phase difference of π or (2n-1)π for the light of the first wavelength B and the third wavelength R, respectively, and a phase difference of 2π or 2nπ for the light of the second wavelength G. Therefore, the second phase conversion element PC2 converts the second circularly polarized light B2 that has passed through the second lens element 112 into the first circularly polarized light B1, maintains the polarization state of the second circularly polarized light G2, and converts the first circularly polarized light R1 into the second circularly polarized light R2.

[0108] Third lens element 113 has a phase difference of π or (2n-1)π for light of the first wavelength B, second wavelength G, and third wavelength R, respectively. Third lens element 113 has a lens action of converging first circularly polarized light B1 that has passed through second phase conversion element PC2 while converting it into second circularly polarized light B2, diverging second circularly polarized light G2 while converting it into first circularly polarized light G1, and diverging second circularly polarized light R2 while converting it into first circularly polarized light R1. The focal length f3B for light of the first wavelength B is greater than the focal length f3G (absolute value) for light of the second wavelength G, and the focal length f3G for light of the second wavelength G is greater than the focal length f3R (absolute value) for light of the third wavelength R (f3B>f3G>f3R).

[0109] The focal lengths f1B, f1G, and f1R of first lens element 111, the focal lengths f2B, f2G, and f2R of second lens element 112, and the focal lengths f3B, f3G, and f3R of third lens element 113 are set to satisfy equations (4), (5), and (6) in the figure. Note that it is assumed here that the inter-lens distance is extremely small. As a result, the focal length fB of first wavelength B, the focal length fG of second wavelength G, and the focal length fR of third wavelength R in lens unit 10 all have the same focal length f. In other words, the light of first wavelength B, second wavelength G, and third wavelength R are focused at the same focal length.

[0110] FIG. 15 is a diagram for explaining the wavelength characteristics of the first phase conversion element PC1 and the second phase conversion element PC2. The upper part of Fig. 15 shows the wavelength characteristics of the first phase conversion element PC1. The lower part of Fig. 15 shows the wavelength characteristics of the second phase conversion element PC2. In each diagram showing wavelength characteristics, the horizontal axis is wavelength (nm) and the vertical axis is Δn·d (nm).

[0111] As described above, the first phase conversion element PC1 is required to convert the direction of rotation of circularly polarized light for light of the first wavelength (blue wavelength: 450 nm), convert the direction of rotation of circularly polarized light for light of the second wavelength (green wavelength: 530 nm), and maintain the direction of rotation of circularly polarized light for light of the third wavelength (red wavelength: 630 nm). The second phase conversion element PC2 is required to convert the direction of rotation of circular polarization for light of the first wavelength, maintain the direction of rotation of circular polarization for light of the second wavelength, and convert the direction of rotation of circular polarization for light of the third wavelength.

[0112] Therefore, when n is an integer greater than or equal to 1, the first phase conversion element PC1 is configured to have a phase difference of (2n-1)π for the first wavelength, a phase difference of (2n-1)π for the second wavelength, and a phase difference of 2nπ for the third wavelength. In the example shown in the upper part of FIG. 15, the first phase conversion element PC1 has a phase difference (Δn·d=1575 nm) corresponding to 7π for the first wavelength, a phase difference (Δn·d=1325 nm) corresponding to 5π for the second wavelength, and a phase difference (Δn·d=1260 nm) corresponding to 4π for the third wavelength. The phase difference for the second wavelength is smaller than the phase difference for the first wavelength, and the phase difference for the third wavelength is smaller than the phase difference for the second wavelength. In other words, the wavelength characteristics of the first phase conversion element PC1 show that the phase difference monotonically decreases as the wavelength increases.

[0113] The second phase conversion element PC2 is configured to have a phase difference of (2n-1)π for the first wavelength, a phase difference of 2nπ for the second wavelength, and a phase difference of (2n-1)π for the third wavelength. In the example shown in the lower part of FIG. 15, the second phase conversion element PC2 has a phase difference (Δn·d=1125 nm) corresponding to 5π for the first wavelength, a phase difference (Δn·d=530 nm) corresponding to 2π for the second wavelength, and a phase difference (Δn·d=315 nm) corresponding to π for the third wavelength. The phase difference for the second wavelength is smaller than the phase difference for the first wavelength, and the phase difference for the third wavelength is smaller than the phase difference for the second wavelength. In other words, the wavelength characteristics of the second phase conversion element PC2 show that the phase difference monotonically decreases as the wavelength increases.

[0114] 15 is an example, and the phase difference may simply decrease with increasing wavelength. For example, the first phase conversion element PC1 may be configured to have a phase difference corresponding to 5π for the first wavelength, a phase difference corresponding to 3π for the second wavelength, and a phase difference corresponding to 2π for the third wavelength.

[0115] FIG. 16 is a diagram for explaining the wavelength characteristics of the liquid crystal layer that constitutes the lens element. The horizontal axis is wavelength (nm) and the vertical axis is Δn·d (nm).

[0116] As described above, each of first lens element 111, second lens element 112, and third lens element 113 is required to convert the direction of rotation of circularly polarized light for light of a first wavelength (blue wavelength: 450 nm), convert the direction of rotation of circularly polarized light for light of a second wavelength (green wavelength: 530 nm), and convert the direction of rotation of circularly polarized light for light of a third wavelength (red wavelength: 630 nm).

[0117] Therefore, first lens element 111, second lens element 112, and third lens element 113 are each configured to have a phase difference of (2n-1)π for the first wavelength, a phase difference of (2n-1)π for the second wavelength, and a phase difference of (2n-1)π for the third wavelength, where n is an integer greater than or equal to 1.

[0118] Fig. 16 shows ideal wavelength characteristics of each of first lens element 111, second lens element 112, and third lens element 113. In the example shown in Fig. 16, first lens element 111, second lens element 112, and third lens element 113 each have a phase difference corresponding to π for the first wavelength, the second wavelength, and the third wavelength, respectively. The phase difference for the second wavelength is smaller than the phase difference for the first wavelength, and the phase difference for the third wavelength is smaller than the phase difference for the second wavelength. In other words, the wavelength characteristics shown here correspond to inverse wavelength dispersion characteristics in which the phase difference monotonically increases as the wavelength increases.

[0119] Even when the second configuration example of such a lens section 10 is applied, the display device DSP exhibits the same optical effect as that described with reference to Figure 12, and can obtain the same effect as the first configuration example.

[0120] The first and second configuration examples described above may be combined. Specifically, as shown in Fig. 13B, lens unit 10 further includes a fourth lens element to be combined with first lens element 111, a fifth lens element to be combined with second lens element 112, and a sixth lens element to be combined with third lens element 113. The fourth lens element has the same configuration as first lens element 111 and corresponds to first lens element 111 with the front and back reversed. The fifth lens element has the same configuration as second lens element 112 and corresponds to second lens element 112 with the front and back reversed. The sixth lens element has the same configuration as third lens element 113 and corresponds to third lens element 113 with the front and back reversed. According to this configuration example, a synergistic effect of the first and second configuration examples can be obtained.

[0121] Example 2 FIG. 17 is a cross-sectional view showing a display device DSP according to a second embodiment. Example 2 shown in FIG. 17 differs from Example 1 shown in FIG. 3 in that the second retardation plate R2, the reflective polarizer PR, and the third retardation plate R3 are replaced with a first selective reflection section 201.

[0122] That is, the display device DSP includes a display panel 2, an illumination device 3, and an optical system 4. The display panel 2 and the illumination device 3 are denoted by the same reference numerals as those in the first embodiment shown in Fig. 3 and detailed description thereof will be omitted, but the display panel 2 is configured to emit linearly polarized display light DL in the display area DA.

[0123] The first structural body 4A of the optical system 4 includes a first retardation plate R1 and a semi-transmitting layer HM. The first retardation plate R1 is a quarter-wave plate. The semi-transmitting layer HM transmits a portion of incident light and reflects the remaining light. The first retardation plate R1 and the semi-transmitting layer HM are laminated in this order along the third direction Z. The first retardation plate R1 is in contact with the display panel 2, the semi-transmitting layer HM is in contact with the first retardation plate R1, and the first retardation plate R1 is disposed between the display panel 2 and the semi-transmitting layer HM.

[0124] The second structure 4B of the optical system 4 includes a first selective reflecting portion 201 and a lens portion 10. As will be described in detail later, the first selective reflecting portion 201 includes an optical element having a cholesteric liquid crystal layer. The lens portion 10 can be configured as the first example configuration described above with reference to FIG. 5 and the like, or as the second example configuration described above with reference to FIG. 13A and the like, or as another example configuration described above with reference to FIG. 13B.

[0125] The first selective reflection portion 201 and the lens portion 10 are laminated in this order along the third direction Z. The lens portion 10 is in contact with the first selective reflection portion 201. The first selective reflection portion 201 is spaced apart from the semi-transparent layer HM and faces the semi-transparent layer HM in the third direction Z via an air layer 4C. The first selective reflection portion 201 is disposed between the semi-transparent layer HM and the lens portion 10.

[0126] FIG. 18 is a cross-sectional view showing an example of the configuration of the first selective reflecting portion 201 shown in FIG. The first selective reflecting portion 201 includes a first optical element 21, a second optical element 22, and a third optical element .

[0127] In one example, the third optical element 23 faces the lens unit 10 in the third direction Z. Furthermore, the first optical element 21, the second optical element 22, and the third optical element 23 are stacked in this order along the third direction Z, but the stacking order may be different from that in the illustrated example.

[0128] The first optical element 21 has a first cholesteric liquid crystal layer LC21 that reflects a first circularly polarized light component of light of a first wavelength (for example, blue wavelength B) toward the semi-transmissive layer HM and transmits a second circularly polarized light component. The second optical element 22 has a second cholesteric liquid crystal layer LC22 that reflects a first circularly polarized light component of light of a second wavelength (for example, a green wavelength G) toward the semi-transmissive layer HM and transmits a second circularly polarized light component. The third optical element 23 has a third cholesteric liquid crystal layer LC23 that reflects the first circularly polarized light of the third wavelength (for example, red wavelength R) toward the semi-transmissive layer HM and transmits the second circularly polarized light.

[0129] FIG. 19 is a cross-sectional view showing an example of the first optical element 21 shown in FIG. Here, we will explain the first cholesteric liquid crystal layer LC21 of the first optical element 21. Note that the first optical element 21 may include a transparent substrate and an alignment film, but illustration and explanation thereof will be omitted here.

[0130] The first cholesteric liquid crystal layer LC21 has a thickness d2 along the third direction Z. In Fig. 19, for the sake of simplicity, one liquid crystal molecule LM2 is shown as a representative liquid crystal molecule that is aligned in the average alignment direction among multiple liquid crystal molecules positioned in the XY plane.

[0131] That is, the first cholesteric liquid crystal layer LC21 has a plurality of liquid crystal structures LS21. Focusing on one liquid crystal structure LS21, the liquid crystal structure LS21 has a liquid crystal molecule LM21 located at one end side thereof and a liquid crystal molecule LM22 located at the other end side thereof. A plurality of liquid crystal molecules LM2, including the liquid crystal molecule LM21 and the liquid crystal molecule LM22, are stacked in a spiral shape along the third direction Z while rotating. The alignment direction of the liquid crystal molecule LM21 and the alignment direction of the liquid crystal molecule LM22 are substantially the same. The liquid crystal structure LS21 has a helical pitch P. The helical pitch P represents one period (360 degrees) of the helix. For example, the thickness d2 of the first cholesteric liquid crystal layer LC21 is several times or more the helical pitch P.

[0132] In the first cholesteric liquid crystal layer LC21, the alignment directions of the liquid crystal structures LS21 adjacent to each other along the first direction X are aligned in the same direction. Similarly, the alignment directions of the liquid crystal structures LS21 adjacent to each other along the second direction Y are aligned in the same direction. That is, the alignment directions of the liquid crystal molecules LM21 are substantially aligned. The alignment directions of the liquid crystal molecules LM22 are also substantially aligned.

[0133] The first cholesteric liquid crystal layer LC21 has a plurality of reflecting surfaces LMR indicated by dashed lines. The reflecting surfaces LMR are formed along the XY plane and are substantially parallel to one another. In accordance with Bragg's law, the reflecting surfaces LMR reflect some circularly polarized light of incident light and transmit other circularly polarized light. The reflecting surfaces LMR here correspond to surfaces on which the liquid crystal molecules LM2 are aligned in the same direction or surfaces on which the spatial phases are aligned (equal phase surfaces).

[0134] The liquid crystal structure LS21 reflects, of the light of the first wavelength, circularly polarized light having the same rotation direction as the rotation direction of the liquid crystal structure LS21. For example, when the rotation direction of the liquid crystal structure LS21 is clockwise, of the light of the first wavelength, right-handed circularly polarized light is reflected and left-handed circularly polarized light is transmitted. Similarly, when the rotation direction of the liquid crystal structure LS21 is counterclockwise, of the light of the first wavelength, left-handed circularly polarized light is reflected and right-handed circularly polarized light is transmitted.

[0135] The first cholesteric liquid crystal layer LC21 is hardened in a state in which the alignment direction of the liquid crystal molecules LM2, including the liquid crystal molecules LM21 and LM22, is fixed. In other words, the alignment direction of the liquid crystal molecules LM2 is not controlled in response to an electric field. For this reason, the first optical element 21 does not include electrodes for alignment control.

[0136] If the helical pitch of the liquid crystal structure LS21 is denoted by P, the refractive index for extraordinary light by ne, and the refractive index for ordinary light by no, then the selective reflection band Δλ of the cholesteric liquid crystal layer for perpendicularly incident light is generally expressed as "(no-ne)*P." Therefore, the helical pitch P1, refractive indexes ne and no of the liquid crystal structure LS21 are set so that the first wavelength is included in the selective reflection wavelength band Δλ of the first cholesteric liquid crystal layer LC21 in order to efficiently reflect circularly polarized light of the first wavelength at the reflecting surface LMR.

[0137] Similar to the first cholesteric liquid crystal layer LC21, the second cholesteric liquid crystal layer LC22 of the second optical element 22 also has a plurality of liquid crystal structures LS22. The helical pitch P2 and refractive indexes n e and n o of the liquid crystal structures LS22 are set so that the second wavelength falls within the selective reflection wavelength band Δλ of the second cholesteric liquid crystal layer LC22, in order to efficiently reflect circularly polarized light of the second wavelength from the reflective surface LMR of the second cholesteric liquid crystal layer LC22.

[0138] Similar to the first cholesteric liquid crystal layer LC21, the third cholesteric liquid crystal layer LC23 of the third optical element 23 also has a plurality of liquid crystal structures LS23. The helical pitch P3 and refractive indexes n e and n o of the liquid crystal structures LS23 are set so that the third wavelength is included in the selective reflection wavelength band Δλ of the third cholesteric liquid crystal layer LC23, in order to efficiently reflect circularly polarized light of the third wavelength from the reflective surface LMR of the third cholesteric liquid crystal layer LC23.

[0139] FIG. 20 is a diagram for explaining the first optical element 21, the second optical element 22, and the third optical element 23 shown in FIG.

[0140] The first optical element 21 is configured to reflect a first circularly polarized light of a first wavelength (blue wavelength) and transmit a second circularly polarized light of the first wavelength. That is, the helical pitch P1 of the liquid crystal structure LS21 included in the first cholesteric liquid crystal layer LC21 is optimized to correspond to the central wavelength λb of the blue laser light emitted from the first light-emitting element LD1 of the illumination device 3.

[0141] The second optical element 22 is configured to reflect the first circularly polarized light of the second wavelength (green wavelength) and transmit the second circularly polarized light of the second wavelength. That is, the helical pitch P2 of the liquid crystal structure LS22 included in the second cholesteric liquid crystal layer LC22 is optimized to correspond to the central wavelength λg of the green laser light emitted from the second light-emitting element LD2 of the illumination device 3. Therefore, the helical pitch P2 of the second optical element 22 is larger than the helical pitch P1 of the first optical element 21.

[0142] The third optical element 23 is configured to reflect the first circularly polarized light of the third wavelength (red wavelength) and transmit the second circularly polarized light of the third wavelength. That is, the helical pitch P3 of the liquid crystal structure LS23 included in the third cholesteric liquid crystal layer LC23 is optimized to correspond to the central wavelength λr of the red laser light emitted from the third light-emitting element LD3 of the illumination device 3. Therefore, the helical pitch P3 of the third optical element 23 is larger than the helical pitch P2 of the second optical element 22.

[0143] 20 is an enlarged schematic view of the liquid crystal structure rotated in the first rotation direction. Liquid crystal structure LS21, liquid crystal structure LS22, and liquid crystal structure LS23 are all rotated in the same direction and are configured to reflect the first circularly polarized light.

[0144] FIG. 21 is a diagram for explaining the optical action of the display device DSP. Here, the optical effect on the light of the first wavelength out of the display light DL emitted from the display panel 2 will be described.

[0145] First, the display panel 2 emits the display light DL with the first linearly polarized light LP1. The display light DL passes through the first retardation plate R1 and is converted into the first circularly polarized light CP1.

[0146] Of the first circularly polarized light CP1 that has passed through the first retardation plate R1, a portion of the first circularly polarized light CP1 passes through the semi-transmitting layer HM, and the other portion of the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM. The first circularly polarized light CP1 that has passed through the semi-transmitting layer HM is reflected by the first selective reflecting portion 201.

[0147] When the first circularly polarized light CP1 is reflected by the semi-transmissive layer HM, it is converted into the second circularly polarized light CP2. The second circularly polarized light CP2 reflected by the semi-transmissive layer HM passes through the first retardation plate R1 and is converted into the second linearly polarized light LP2, which is then absorbed by the display panel 2.

[0148] Of the first circularly polarized light CP1 reflected by the first selective reflecting unit 201, a portion of the first circularly polarized light CP1 passes through the semi-transmitting layer HM, and the other portion of the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM. When the first circularly polarized light CP1 is reflected by the semi-transmitting layer HM, it is converted into second circularly polarized light CP2. The first circularly polarized light CP1 that has passed through the semi-transmissive layer HM passes through the first retardation plate R1 and is converted into first linearly polarized light LP1.

[0149] The second circularly polarized light CP2 reflected by the semi-transmissive layer HM is transmitted through the first selective reflecting unit 201. The second circularly polarized light CP2 transmitted through the first selective reflecting unit 201 is focused on the pupil E of the user by the lens action of the lens unit 10.

[0150] In this embodiment 2 as well, the same effects as those of the above-described embodiment 1 can be obtained. In addition, the number of parts constituting the optical system 4 can be reduced.

[0151] The first linearly polarized light LP1 described with reference to FIG. 21 may be replaced with the second linearly polarized light LP2, and the first circularly polarized light CP1 may be replaced with the second circularly polarized light CP2.

[0152] As described above, according to this embodiment, it is possible to provide a lens unit and a display device that can improve display quality.

[0153] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0154] 1...head-mounted display 2...display panel 3...illumination device 4...optical system DSP…display device R1...First retardation plate R2...Second retardation plate R3...Third retardation plate HM...Semi-transparent layer PR...Reflective polarizing plate 10... Lens portion 11... First lens element 12... Second lens element 13... Third lens element 14... Fourth lens element 15... Fifth lens element 16... Sixth lens element 201...first selective reflection portion 21...first optical element LC21...first cholesteric liquid crystal layer 22...second optical element LC22...second cholesteric liquid crystal layer 23...third optical element LC23...third cholesteric liquid crystal layer

Claims

1. a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; a reflective polarizer configured to transmit a first linearly polarized light and reflect a second linearly polarized light that is orthogonal to the first linearly polarized light; a second retardation plate disposed between the semi-transmissive layer and the reflective polarizer; A lens part, a third retardation plate disposed between the reflective polarizer and the lens portion; Equipped with The lens portion is a first lens element having a lens effect of converting a first circularly polarized light having a first wavelength into a second circularly polarized light having an opposite rotation while focusing the light; a second lens element that is stacked on the first lens element and has a lens action of converting the second circularly polarized light of the first wavelength into the first circularly polarized light of the first wavelength and focusing the light, each of the first lens element and the second lens element has a liquid crystal layer that is hardened in a state in which the alignment directions of a plurality of liquid crystal molecules, including first liquid crystal molecules and second liquid crystal molecules, are fixed; the liquid crystal layer has, in a plan view, a first annular region in which a plurality of the first liquid crystal molecules are aligned in the same direction, and a second annular region outside the first annular region in which a plurality of the second liquid crystal molecules are aligned in the same direction; a circle surrounding the first annular region and a circle surrounding the second annular region have the same center; The alignment direction of the first liquid crystal molecules is different from the alignment direction of the second liquid crystal molecules, the first annular region of the first lens element overlaps the first annular region of the second lens element; an alignment direction of the first liquid crystal molecules of the first lens element is symmetrical to an alignment direction of the first liquid crystal molecules of the second lens element with respect to a line passing through the center in a plan view; the lens portion is spaced from the reflective polarizer; The display device, wherein the first retardation plate, the second retardation plate, and the third retardation plate are quarter-wave plates.

2. a display panel including a polarizing plate and configured to emit linearly polarized display light; a semi-transparent layer; a first retardation plate disposed between the display panel and the semi-transmissive layer; A lens part, a first selective reflection unit disposed between the semi-transmitting layer and the lens unit and spaced apart from the semi-transmitting layer; Equipped with The lens portion is a first lens element having a lens effect of converting a first circularly polarized light having a first wavelength into a second circularly polarized light having an opposite rotation while focusing the light; a second lens element that is stacked on the first lens element and has a lens action of converting the second circularly polarized light of the first wavelength into the first circularly polarized light of the first wavelength and focusing the light, each of the first lens element and the second lens element has a liquid crystal layer that is hardened in a state in which the alignment directions of a plurality of liquid crystal molecules, including first liquid crystal molecules and second liquid crystal molecules, are fixed; the liquid crystal layer has, in a plan view, a first annular region in which a plurality of the first liquid crystal molecules are aligned in the same direction, and a second annular region outside the first annular region in which a plurality of the second liquid crystal molecules are aligned in the same direction; a circle surrounding the first annular region and a circle surrounding the second annular region have the same center; The alignment direction of the first liquid crystal molecules is different from the alignment direction of the second liquid crystal molecules, the first annular region of the first lens element overlaps the first annular region of the second lens element; an alignment direction of the first liquid crystal molecules of the first lens element is symmetrical to an alignment direction of the first liquid crystal molecules of the second lens element with respect to a line passing through the center in a plan view; the lens portion is spaced from the semi-transparent layer, the first retardation plate is a quarter wave plate, The first selective reflection portion is A display device comprising a first optical element having a first cholesteric liquid crystal layer that reflects first circularly polarized light of a first wavelength toward the semi-transparent layer and transmits second circularly polarized light of the first wavelength that is rotated in the opposite direction to the first circularly polarized light.

Images