Indication device

Abstract

To realize a diopter scale adjustment function.SOLUTION: A display device comprises: a display module configured to emit linear polarization display light; a first structure including a first retardation plate facing the display module, a holographic optical element facing the first retardation plate, and a second retardation plate facing the holographic optical element; a second structure including a reflection polarization plate facing the second retardation plate, and a transparent substrate facing the reflection polarization plate; and a variable mechanism for changing a gap between the first structure and the second structure.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a display device.

Background Art

[0002] In recent years, technologies that provide, for example, virtual reality (VR: Virtual Reality) using a head-mounted display worn on a user's head have attracted attention. The head-mounted display is configured such that an image is displayed on a display provided in front of the user's eyes. Thereby, a user wearing the head-mounted display can experience an immersive virtual reality space.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

[0005] According to one embodiment, the display device is The device comprises a display module configured to emit linearly polarized display light; a first structure comprising a first phase difference plate facing the display module, a holographic optical element facing the first phase difference plate, and a second phase difference plate facing the holographic optical element; a second structure comprising a reflective polarizing plate facing the second phase difference plate and a transparent substrate facing the reflective polarizing plate; and a variable mechanism for varying the distance between the first structure and the second structure.

[0006] According to one embodiment, the display device is The device comprises a display module configured to emit linearly polarized display light; a first structure comprising a first phase difference plate facing the display module, a semi-transparent layer facing the first phase difference plate, and a second phase difference plate facing the semi-transparent layer; a second structure comprising a reflective polarizing plate facing the second phase difference plate, a third phase difference plate facing the reflective polarizing plate, and a liquid crystal element having a lens effect facing the third phase difference plate; and a variable mechanism for varying the distance between the first structure and the second structure. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a perspective view showing an example of the appearance of the head-mounted display 1. [Figure 2] Figure 2 is a diagram illustrating the general configuration of the head-mounted display 1 shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing a first configuration example of a display device DSP. [Figure 4] Figure 4 is a diagram illustrating the optical operation of a display device DSP. [Figure 5] Figure 5 shows the second structure 4B before and after movement. [Figure 6] FIG. 6 is a diagram showing the optical system of the display device shown in FIG. 5 developed at the position of the reflective polarizing plate PR. [Figure 7] FIG. 7 is a cross-sectional view showing a second configuration example of the display device DSP. [Figure 8] FIG. 8 is a diagram showing the state before and after the movement of the structure BD. [Figure 9] FIG. 9 is a diagram showing the state before and after the movement of the first structure 4A. [Figure 10] FIG. 10 is a cross-sectional view showing a fourth configuration example of the display device DSP. [Figure 11] FIG. 11 is a cross-sectional view showing an example of the liquid crystal element 10 shown in FIG. 10. [Figure 12] FIG. 12 is a plan view showing an example of the alignment pattern in the liquid crystal layer LC1 shown in FIG. 11. [Figure 13] FIG. 13 is a diagram for explaining the optical action of the display device DSP. [Figure 14] FIG. 14 is a diagram showing the state before and after the movement of the second structure 4B. [Figure 15] FIG. 15 is a diagram showing the optical system of the display device shown in FIG. 14 developed at the positions of the reflective polarizing plate PR and the semi-transmissive layer HM. [Figure 16] FIG. 16 is a cross-sectional view showing a fifth configuration example of the display device DSP. [Figure 17] FIG. 17 is a diagram showing the state before and after the movement of the structure BD. [Figure 18] FIG. 18 is a diagram showing the state before and after the movement of the first structure 4A.

MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, this embodiment will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and any modifications that a person skilled in the art could easily conceive while maintaining the spirit of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment in order to clarify the explanation; however, these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and in each drawing, components that perform the same or similar functions as those described above in previously shown drawings are denoted by the same reference numerals, and redundant detailed explanations may be omitted as appropriate.

[0009] Furthermore, the drawings will include mutually orthogonal X, Y, and Z axes as needed to facilitate understanding. The direction along the X axis will be referred to as the first direction X, the direction along the Y axis as the second direction Y, and the direction along the Z axis as the third direction Z. The plane defined by the X and Y axes will be referred to as the XY plane, and viewing the XY plane will be called a plan view.

[0010] 《Basic configuration》 Figure 1 is a perspective view showing an example of the appearance of the head-mounted display 1.

[0011] 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 the user wears the head-mounted display 1 on their head, the display device DSPR is positioned in front of the user's right eye, and the display device DSPL is positioned in front of the user's left eye.

[0012] Figure 2 is a diagram illustrating the general configuration of the head-mounted display 1 shown in Figure 1.

[0013] The head-mounted display 1 comprises a housing HS that houses the display devices DSPR and DSPL, and a variable mechanism SL provided on each of the display devices DSPR and DSPL.

[0014] The DSPR display device is configured substantially the same as the DSPL display device. Each of the DSPR and DSPL displays comprises a display module DM and an optical system 4. The display module DM is configured to emit linearly polarized display light. The optical system 4 of the DSPR display device is configured to direct the display light from the display module DM to the right eye ER. The optical system 4 of the DSPL display device is configured to direct the display light from the display module DM to the left eye EL.

[0015] In one example, the display module DM consists of a liquid crystal panel and a lighting device, but is not limited to this. For example, the display module DM may be a display panel equipped with self-emissive light-emitting elements such as organic electroluminescent (EL) elements, micro-LEDs, or mini-LEDs. If the display module DM is a display panel equipped with light-emitting elements, the lighting device is omitted.

[0016] The variable mechanism SL is fixed to the housing HS. As will be described later, the variable mechanism SL is a mechanism for varying the distance between the first structure 4A and the second structure 4B of the optical system 4.

[0017] Next, some configuration examples of the display device DSP according to this embodiment will be described.

[0018] 《Example Configuration 1》 Figure 3 is a cross-sectional view showing a first configuration example of a display device DSP. The DSP display device described here can be applied to each of the above-mentioned DSPR and DSPL display devices.

[0019] The display module DM comprises a display panel 2 and an illumination device 3. The display panel 2 is a transmissive liquid crystal panel and is formed in a flat plate shape. The display panel 2 comprises 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 by a seal SE. The first polarizer PL1 is positioned between the illumination device 3 and the first substrate SUB1. The second polarizer PL2 is positioned between the second substrate SUB2 and the optical system 4.

[0020] The display panel 2 has a display area DA configured to emit linearly polarized display light DL. The display area DA 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. The surface of the second polarizer PL2 is referred to as the display surface DS.

[0021] The optical system 4 comprises a first structure 4A and a second structure 4B. The first structure 4A is spaced apart from the second structure 4B in the direction normal to the display surface DS. An air layer 4C is interposed between the first structure 4A and the second structure 4B. The display panel 2 is positioned between the illumination device 3 and the first structure 4A. The first structure 4A is positioned between the display panel 2 and the second structure 4B (or between the display panel 2 and the air layer 4C).

[0022] The first structure 4A comprises a first phase difference plate R1 facing the display module DM, a holographic optical element 20 facing the first phase difference plate R1, and a second phase difference plate R2 facing the holographic optical element 20. The holographic optical element 20 is located between the first phase difference plate R1 and the second phase difference plate R2. In one example, the first phase difference plate R1, the holographic optical element 20, and the second phase difference plate R2 are bonded to each other.

[0023] The first phase difference plate R1 and the second phase difference plate R2 are quarter-wave plates that impart a phase difference of 1 / 4 wavelength to the transmitted light. The holographic optical element 20 reflects and diffracts a portion of the incident light, and also has a lens-like effect that focuses the light. The holographic optical element 20 has an interference fringe pattern and diffracts the incident light in a predetermined direction.

[0024] The second structure 4B comprises a reflective polarizing plate PR facing the second phase difference plate R2, and a transparent substrate TS facing the reflective polarizing plate PR. In one example, the reflective polarizing plate PR is bonded to the transparent substrate TS. An air layer 4C is interposed between the second phase difference plate R2 and the reflective polarizing plate PR.

[0025] A reflective polarizer (PR) transmits the first linearly polarized light and reflects the second linearly polarized light that is perpendicular to the first. Examples of reflective polarizers include multilayer thin-film types and wire grid types. Transparent substrates (TS) are glass substrates or resin substrates.

[0026] The variable mechanism SL and support SP are fixed to the housing HS.

[0027] The first structure 4A is supported by a support SP and fixed to the housing HS at a certain distance. The display module DM is positioned between the housing HS and the first structure 4A. In this configuration, the display module DM and the first structure 4A are held relative to the housing HS without moving in the direction normal to the display surface DS.

[0028] The second structure 4B is supported by a variable mechanism SL. The variable mechanism SL is configured to move the second structure 4B in the direction normal to the display surface DS. When the second structure 4B moves, the variable mechanism SL slides the second structure 4B in the direction normal to the display surface DS without rotating the second structure 4B in the plane. This makes it possible to vary the distance between the first structure 4A and the second structure 4B.

[0029] Figure 4 is a diagram illustrating the optical operation of a display device DSP.

[0030] First, the display module DM emits a display light DL of first linear polarization LP1 from the display surface DS. The display light DL passes through the first phase difference plate R1 and is converted into first circular polarization CP1.

[0031] Of the first circularly polarized light CP1 that has passed through the first phase difference plate R1, some of the first circularly polarized light CP1 passes through the holographic optical element 20, while other first circularly polarized light CP1 is reflected by the holographic optical element 20. The first circularly polarized light CP1 that has passed through the holographic optical element 20 passes through the second phase difference plate R2 and is converted into second linearly polarized light LP2.

[0032] Furthermore, when the first circularly polarized light CP1 is reflected by the holographic optical element 20, it is converted into a second circularly polarized light CP2, which is polarized in the opposite direction to the first circularly polarized light CP1. The second circularly polarized light CP2 reflected by the holographic optical element 20 is transmitted through the first phase difference plate R1 and converted into a second linearly polarized light LP2, which is absorbed by the display module DM.

[0033] The second linearly polarized light LP2, which has passed through the second phase difference plate R2, is reflected by the reflective polarizer PR. The second linearly polarized light LP2 reflected by the reflective polarizer PR passes through the second phase difference plate R2 and is converted into the first circularly polarized light CP1.

[0034] Of the first circularly polarized light CP1 that passes through the second phase difference plate R2, some of the first circularly polarized light CP1 is reflected and diffracted by the holographic optical element 20, while other first circularly polarized light CP1 passes through the holographic optical element 20. When the first circularly polarized light CP1 is reflected and diffracted by the holographic optical element 20, it is converted into second circularly polarized light CP2. The second circularly polarized light CP2 reflected by the holographic optical element 20 passes through the second phase difference plate R2 and is converted into first linearly polarized light LP1. Furthermore, the first circularly polarized light CP1 that passes through the holographic optical element 20 is converted to the first linearly polarized light LP1 by passing through the first phase difference plate R1.

[0035] The first linearly polarized light LP1, having passed through the second phase difference plate R2, then passes through the reflective polarizer PR and, under the lens effect of the holographic optical element 20, is focused onto the user's pupil E.

[0036] In such a display device DSP, the optical system 4 has an optical path that passes through the holographic optical element 20 and the reflective polarizer PR three times. In other words, in the optical system 4, the optical distance between the holographic optical element 20 and the reflective polarizer PR is approximately three times the actual distance between the holographic optical element 20 and the reflective polarizer PR. As a result, when the display surface DS of the display module DM is considered as an object, the user can observe an enlarged virtual image of the object formed at a distance through the optical system 4.

[0037] Incidentally, users with poor eyesight cannot clearly see virtual images at a distance. For such users, it is necessary to bring the position of the virtual image closer to the user. The position of the virtual image can be adjusted by adjusting the distance between the first structure 4A and the second structure 4B. For example, by moving the optical position of the display surface DS, which corresponds to an object, to the side away from the focal point of the optical system 4, the position of the virtual image can be brought closer to the user.

[0038] In other words, according to this embodiment, a diopter adjustment function can be provided to adjust how the image appears according to the user's visual acuity. Furthermore, as shown in Figure 2, a variable mechanism SL is provided for both the right-eye display device DSPR and the left-eye display device DSPL. Therefore, the position of the virtual images on the DSPR and DSPL displays can be adjusted independently. As a result, the virtual images on the DSPR and DSPL displays can be displayed clearly according to the visual acuity of the right and left eyes, respectively.

[0039] Furthermore, when the variable mechanism SL moves the second structure 4B, the second structure 4B does not rotate in its plane. As a result, the transmission axis (or reflection axis) in the reflective polarizer PR does not rotate in its plane, which suppresses a decrease in display quality caused by misalignment and also suppresses a decrease in light utilization efficiency.

[0040] Furthermore, the first linearly polarized light LP1, as explained with reference to Figure 4, may be replaced with the second linearly polarized light LP2, or the first circularly polarized light CP1 may be replaced with the second circularly polarized light CP2.

[0041] Here, we will explain an example of adjusting the position of the virtual image.

[0042] Figure 5 shows the second structure 4B before and after movement. The second structure 4B here comprises a reflective polarizing plate PR and a transparent substrate TS.

[0043] The left side of the figure shows the second structure 4B positioned at the first position P1 (before movement), and the right side of the figure shows the second structure 4B positioned at the second position P2 (after movement). When the second structure 4B is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the second structure 4B is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by moving the variable mechanism SL so that the second structure 4B is close to the display module DM.

[0044] Figure 6 shows the optical system of the display device shown in Figure 5 unfolded at the position of the reflective polarizer PR.

[0045] The first focal point FP1 is defined as the position with a focal length f in front of the holographic optical element 20 (towards the user's pupil), and the second focal point FP2 is defined as the position with a focal length f in rear of the holographic optical element 20.

[0046] When the second structure 4B is located at the first position P1, point P11 is defined as the point where the line passing through the end E11 of the display surface DS (shown by the solid line) and the second focal point FP2 intersects with the position of the holographic optical element 20. Point P12 is defined as the point where the line passing through the end 20E of the holographic optical element 20 and the first focal point FP1 intersects with the perpendicular line passing through point P11. In this case, the virtual image V1 is formed at the position of point P12, as shown by the solid line.

[0047] When the second structure 4B is located at the second position P2, point P21 is defined as the point where the line passing through the end E21 of the display surface DS (shown by the dashed line) and the second focal point FP2 intersects with the position of the holographic optical element 20. Point P22 is defined as the point where the line passing through the end 20E of the holographic optical element 20 and the first focal point FP1 intersects with the perpendicular line passing through point P21. In this case, the virtual image V2 is formed at the position of point P22, as shown by the dashed line.

[0048] In this way, as the second structure 4B moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for nearsighted users.

[0049] 《Example Configuration 2》 Figure 7 is a cross-sectional view showing a second configuration example of a display device DSP. The second configuration example shown in Figure 7 differs from the first configuration example shown in Figure 3 in that the first structure 4A and the display module DM are supported by the variable mechanism SL, and the second structure 4B is supported by the support SP. The following explanation will focus on these differences.

[0050] The second structure 4B is supported by a support SP fixed to the housing HS. Therefore, the second structure 4B is fixed to the housing HS at a certain distance.

[0051] The display module DM is positioned between the housing HS and the first structure 4A, and is fixed to the first structure 4A but not to the housing HS. The display module DM and the first structure 4A together constitute a single structure BD.

[0052] The structure BD (the block of the display module DM and the first structure 4A) is supported by a variable mechanism SL fixed to the housing HS. The variable mechanism SL is configured to move the structure BD in the direction normal to the display surface DS. When the structure BD moves, the variable mechanism SL slides the structure BD in the direction normal to the display surface DS without rotating the structure BD in the plane. This makes it possible to vary the distance between the first structure 4A and the second structure 4B (or the distance between the holographic optical element 20 and the reflective polarizer PR).

[0053] Figure 8 shows the structure BD before and after movement. The structure BD here comprises a display module DM, a first phase difference plate R1, a holographic optical element 20, and a second phase difference plate R2.

[0054] The left side of the figure shows the structure BD positioned at the first position P1 (before movement), and the right side of the figure shows the structure BD positioned at the second position P2 (after movement). When the structure BD is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the structure BD is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by the variable mechanism SL moving the structure BD closer to the reflective polarizer PR.

[0055] In this second configuration example, when the optical system 4 is deployed, a diagram similar to that described with reference to Figure 6 is obtained. That is, as the structure BD including the first structure 4A moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for myopic users.

[0056] 《Example of a third configuration》 Figure 9 shows the state of the first structure 4A before and after movement. The third configuration example differs from the second configuration example shown in Figure 7 in that the display module DM is fixed to the housing HS, and the variable mechanism SL is configured to move the first structure 4A. The first structure 4A here comprises a first phase difference plate R1, a holographic optical element 20, and a second phase difference plate R2.

[0057] The left side of the figure shows the state in which the first structure 4A is positioned at the first position P1 (before movement), and the right side of the figure shows the state in which the first structure 4A is positioned at the second position P2 (after movement). When the first structure 4A is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the first structure 4A is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by the variable mechanism SL moving the first structure 4A closer to the reflective polarizer PR.

[0058] In this third configuration example, when the optical system 4 is deployed, a diagram similar to that described with reference to Figure 6 is obtained. That is, as the first structure 4A moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for nearsighted users.

[0059] 《Example of the 4th configuration》 Figure 10 is a cross-sectional view showing a fourth configuration example of a display device DSP. The DSP display device described here can be applied to each of the above-mentioned DSPR and DSPL display devices.

[0060] The display module DM comprises a display panel 2 and a lighting device 3. The configuration of the display panel 2 is the same as in the first configuration example, and the same reference numerals are used, so its description is omitted.

[0061] The optical system 4 comprises a first structure 4A and a second structure 4B. The first structure 4A is spaced apart from the second structure 4B in the direction normal to the display surface DS. An air layer 4C is interposed between the first structure 4A and the second structure 4B. The display panel 2 is positioned between the illumination device 3 and the first structure 4A. The first structure 4A is positioned between the display panel 2 and the second structure 4B (or between the display panel 2 and the air layer 4C).

[0062] The first structure 4A comprises a first phase difference plate R1 facing the display module DM, a semi-transparent layer HM facing the first phase difference plate R1, and a second phase difference plate R2 facing the semi-transparent layer HM. The semi-transparent layer HM is located between the first phase difference plate R1 and the second phase difference plate R2. In one example, the first phase difference plate R1, the semi-transparent layer HM, and the second phase difference plate R2 are bonded to each other.

[0063] The first phase difference plate R1 and the second phase difference plate R2 are quarter-wave plates that impart a phase difference of 1 / 4 wavelength to the transmitted light. A semi-transparent layer (HM) transmits some of the incident light and reflects the rest. For example, a semi-transparent layer (HM) is a thin film made of a metallic material such as aluminum or silver. The transmittance of such a semi-transparent layer (HM) is approximately 50%.

[0064] The second structure 4B comprises a reflective polarizing plate PR facing the second phase difference plate R2, a third phase difference plate R3 facing the reflective polarizing plate PR, and a liquid crystal element 10 facing the third phase difference plate. The third phase difference plate R3 is located between the reflective polarizing plate PR and the liquid crystal element 10. In one example, the reflective polarizing plate PR, the third phase difference plate R3, and the liquid crystal element 10 are bonded to each other. An air layer 4C is interposed between the second phase difference plate R2 and the reflective polarizing plate PR.

[0065] A reflective polarizer PR transmits the first linearly polarized light from the incident light and reflects the second linearly polarized light that is perpendicular to the first linearly polarized light. The third phase difference plate R3 is a quarter-wave plate that imparts a phase difference of 1 / 4 wavelength to the transmitted light. The liquid crystal element 10 imparts a phase difference of half a wavelength to light of a specific wavelength and has a lens effect that focuses first circularly polarized light. While the liquid crystal element 10 is given here as an example of an element with a lens effect that focuses circularly polarized light, it is not limited to elements utilizing liquid crystals, as long as it has a similar lens effect.

[0066] The variable mechanism SL and support SP are fixed to the housing HS.

[0067] The first structure 4A is supported by a support SP and fixed to the housing HS at a certain distance. The display module DM is positioned between the housing HS and the first structure 4A. In this configuration, the display module DM and the first structure 4A are held relative to the housing HS without moving in the direction normal to the display surface DS.

[0068] The second structure 4B is supported by a variable mechanism SL. The variable mechanism SL is configured to move the second structure 4B in the direction normal to the display surface DS. When the second structure 4B moves, the variable mechanism SL slides the second structure 4B in the direction normal to the display surface DS without rotating the second structure 4B in the plane. This makes it possible to vary the distance between the first structure 4A and the second structure 4B.

[0069] Figure 11 is a cross-sectional view showing an example of the liquid crystal element 10 shown in Figure 10.

[0070] The liquid crystal element 10 comprises a substrate 11, an alignment film AL11, a liquid crystal layer (first liquid crystal layer) LC1, an alignment film AL12, and a substrate 12.

[0071] Substrates 11 and 12 are transparent substrates that transmit light, such as glass substrates or resin substrates. Substrate 11 is bonded to the third phase difference plate R3 shown in Figure 10, for example, but may be replaced by the third phase difference plate R3.

[0072] The alignment film AL11 is placed on the inner surface 11A of the substrate 11. In the example shown in Figure 11, the alignment film AL11 is in contact with the substrate 11, but other thin films may be interposed between the alignment film AL11 and the substrate 11. The alignment film AL12 is positioned on the inner surface 12A of the substrate 12. In the example shown in Figure 11, the alignment film AL12 is in contact with the substrate 12, but other thin films may be interposed between the alignment film AL12 and the substrate 12. The alignment film AL12 faces the alignment film AL11 in the third direction Z. The orientation films AL11 and AL12 are formed from, for example, polyimide, and are both horizontal orientation films that have orientation restricting forces along the XY plane.

[0073] The liquid crystal layer LC1 is positioned between the alignment films AL11 and AL12 and is in contact with them. The liquid crystal layer LC1 has a thickness d1 along the third direction Z. The liquid crystal layer LC1 has nematic liquid crystals whose orientation direction is aligned along the third direction Z.

[0074] In other words, the liquid crystal layer LC1 has multiple liquid crystal structures LMS1. Focusing on one liquid crystal structure LMS1, it has liquid crystal molecules LM11 located at one end and liquid crystal molecules LM12 located at the other end. Liquid crystal molecules LM11 are close to the alignment film AL11, and liquid crystal molecules LM12 are close to the alignment film AL12. The orientation direction of liquid crystal molecules LM11 and liquid crystal molecules LM12 are almost the same. Furthermore, the orientation direction of other liquid crystal molecules LM1 between liquid crystal molecules LM11 and LM12 is also almost the same as the orientation direction of liquid crystal molecule LM11. Note that the orientation direction of liquid crystal molecules LM1 here corresponds to the direction of the long axis of the liquid crystal molecule in the XY plane.

[0075] Furthermore, in the liquid crystal layer LC1, multiple adjacent liquid crystal structures LMS1 along the first direction X have different orientation directions from one another. Similarly, multiple adjacent liquid crystal structures LMS1 along the second direction Y also have different orientation directions from one another. The orientation directions of multiple liquid crystal molecules LM11 aligned along the alignment film AL11, and the orientation directions of multiple liquid crystal molecules LM12 aligned along the alignment film AL12, change continuously (or linearly).

[0076] In this type of liquid crystal layer LC1, the orientation direction of the liquid crystal molecules LM1, including liquid crystal molecules LM11 and LM12, is fixed during curing. In other words, the orientation direction of the liquid crystal molecules LM1 is not controlled by the electric field. For this reason, the liquid crystal element 10 does not have electrodes for orientation control.

[0077] When the refractive index anisotropy or birefringence of the liquid crystal layer LC1 (the difference between the refractive index ne for extraordinary light and the refractive index no for ordinary light) is Δn, the retardation (phase difference) Δn·d1 of the liquid crystal layer LC1 is set to half of a specific wavelength λ.

[0078] Figure 12 is a plan view showing an example of the orientation pattern in the liquid crystal layer LC1 shown in Figure 11.

[0079] Figure 12 shows an example of the spatial phase of the liquid crystal layer LC1 in the XY plane. The spatial phase shown here represents the orientation direction of the liquid crystal molecules LM11 that are close to the alignment film AL11, among the liquid crystal molecules LM1 contained in the liquid crystal structure LMS1.

[0080] In the concentric circles indicated by the dotted lines in the figure, the spatial phases are aligned. Alternatively, in the annular region enclosed by two adjacent concentric circles, the orientation directions of the liquid crystal molecules LM11 are aligned. However, the orientation directions of the liquid crystal molecules LM11 in adjacent annular regions are different.

[0081] The liquid crystal layer LC1, in a plan view, has a first annular region C1 and a second annular region C2. The second annular region C2 is located outside the first annular region C1. The first annular region C1 is composed of first liquid crystal molecules LM111 oriented in the same direction. The second annular region C2 is composed of second liquid crystal molecules LM112 oriented in the same direction. The orientation direction of the first liquid crystal molecules LM111 is different from the orientation direction of the second liquid crystal molecules LM112.

[0082] Similarly, the orientation directions of the liquid crystal molecules LM11, aligned radially from the central region of the concentric circles, are different from each other and change continuously. In other words, within the illustrated XY plane, the spatial phase of the liquid crystal layer LC1 is different along the radial direction and changes continuously.

[0083] When first circularly polarized light is incident on a liquid crystal element 10 with this configuration, the first circularly polarized light is focused toward the center of the concentric circles, and the light transmitted through the liquid crystal element 10 is converted into second circularly polarized light, which is in the opposite direction to the first circularly polarized light.

[0084] Figure 13 is a diagram illustrating the optical operation of a display device DSP.

[0085] First, the display module DM emits a display light DL of first linear polarization LP1 from the display surface DS. The display light DL passes through the first phase difference plate R1 and is converted into first circular polarization CP1.

[0086] Of the first circularly polarized light CP1 that passes through the first phase difference plate R1, some of the first circularly polarized light CP1 passes through the semi-transparent layer HM, while the rest is reflected by the semi-transparent layer HM. The first circularly polarized light CP1 that passes through the semi-transparent layer HM passes through the second phase difference plate R2 and is converted into second linearly polarized light LP2.

[0087] Furthermore, when the first circularly polarized light CP1 is reflected by the semi-transparent layer HM, it is converted into a second circularly polarized light CP2, which is polarized in the opposite direction to the first circularly polarized light CP1. The second circularly polarized light CP2 reflected by the semi-transparent layer HM is transmitted through the first phase difference plate R1 and converted into a second linearly polarized light LP2, which is absorbed by the display module DM.

[0088] The second linearly polarized light LP2, which has passed through the second phase difference plate R2, is reflected by the reflective polarizer PR. The second linearly polarized light LP2 reflected by the reflective polarizer PR passes through the second phase difference plate R2 and is converted into the first circularly polarized light CP1.

[0089] Of the first circularly polarized light CP1 that passes through the second phase difference plate R2, some are reflected by the semi-transparent layer HM, and others pass through the semi-transparent layer HM. When the first circularly polarized light CP1 is reflected by the semi-transparent layer HM, it is converted into second circularly polarized light CP2. The second circularly polarized light CP2 reflected by the semi-transparent layer HM passes through the second phase difference plate R2 and is converted into first linearly polarized light LP1. Furthermore, the first circularly polarized light CP1 that passes through the semi-transparent layer HM is converted to the first linearly polarized light LP1 by passing through the first phase difference plate R1.

[0090] The first linearly polarized light LP1, having passed through the second phase difference plate R2, then passes through the reflective polarizer PR, and further passes through the third phase difference plate R3 to be converted into the first circularly polarized light CP1. The first circularly polarized light CP1, having passed through the third phase difference plate R3, is converted into the second circularly polarized light CP2 in the liquid crystal element 10 and, under the lens effect, is focused towards the user's pupil E.

[0091] In this fourth configuration example, the same effects as in the first configuration example described above can be obtained.

[0092] Furthermore, the first linearly polarized light LP1, as explained with reference to Figure 13, may be replaced with the second linearly polarized light LP2, or the first circularly polarized light CP1 may be replaced with the second circularly polarized light CP2.

[0093] Here, we will explain an example of adjusting the position of the virtual image.

[0094] Figure 14 shows the state of the second structure 4B before and after movement. The second structure 4B here comprises a reflective polarizing plate PR, a third phase difference plate R3, and a liquid crystal element 10.

[0095] The left side of the figure shows the second structure 4B positioned at the first position P1 (before movement), and the right side of the figure shows the second structure 4B positioned at the second position P2 (after movement). When the second structure 4B is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the second structure 4B is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by moving the variable mechanism SL so that the second structure 4B is close to the display module DM.

[0096] Figure 15 is a diagram showing the optical system of the display device shown in Figure 14, unfolded at the positions of the reflective polarizing plate PR and the semitransparent layer HM.

[0097] The position with a focal length f in front of the liquid crystal element 10 (towards the user's eye) is defined as the first focal point FP1, and the position with a focal length f in rear of the liquid crystal element 10 is defined as the second focal point FP2.

[0098] When the second structure 4B is located at the first position P1, point P11 is defined as the point where the line passing through the end E11 of the display surface DS (shown by a solid line) and the second focal point FP2 intersects with the position of the liquid crystal element 10, and point P12 is defined as the point where the line passing through the end 10E of the liquid crystal element 10 and the first focal point FP1 intersects with the perpendicular line passing through point P11. At this time, the virtual image V1 is formed at the position of point P12, as shown by the solid line.

[0099] When the second structure 4B is located at the second position P2, point P21 is defined as the point where the line passing through the end E21 of the display surface DS (shown by the dashed line) and the second focal point FP2 intersects with the position of the liquid crystal element 10. Point P22 is defined as the point where the line passing through the end 10E of the liquid crystal element 10 and the first focal point FP1 intersects with the perpendicular line passing through point P21. In this case, the virtual image V2 is formed at the position of point P22, as shown by the dashed line.

[0100] In this way, as the second structure 4B moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for nearsighted users.

[0101] 《Example of Configuration #5》 Figure 16 is a cross-sectional view showing a fifth configuration example of a display device DSP. The fifth configuration example shown in Figure 16 differs from the fourth configuration example shown in Figure 10 in that the first structure 4A and the display module DM are supported by the variable mechanism SL, and the second structure 4B is supported by the support SP. The following explanation will focus on these differences.

[0102] The second structure 4B is supported by a support SP fixed to the housing HS. Therefore, the second structure 4B is fixed to the housing HS at a certain distance.

[0103] The display module DM is positioned between the housing HS and the first structure 4A, and is fixed to the first structure 4A but not to the housing HS. The display module DM and the first structure 4A together constitute a single structure BD.

[0104] The structure BD (the block of the display module DM and the first structure 4A) is supported by a variable mechanism SL fixed to the housing HS. The variable mechanism SL is configured to move the structure BD in the direction normal to the display surface DS. When the structure BD moves, the variable mechanism SL slides the structure BD in the direction normal to the display surface DS without rotating the structure BD in the plane. This makes it possible to vary the distance between the first structure 4A and the second structure 4B (or the distance between the semitransparent layer HM and the reflective polarizer PR).

[0105] Figure 17 shows the structure BD before and after movement. The structure BD here comprises a display module DM, a first phase difference plate R1, a semi-transparent layer HM, and a second phase difference plate R2.

[0106] The left side of the figure shows the structure BD positioned at the first position P1 (before movement), and the right side of the figure shows the structure BD positioned at the second position P2 (after movement). When the structure BD is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the structure BD is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by the variable mechanism SL moving the structure BD closer to the reflective polarizer PR.

[0107] In this fifth configuration example, when the optical system 4 is deployed, a diagram similar to that described with reference to Figure 15 is obtained. That is, as the structure BD including the first structure 4A moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for nearsighted users.

[0108] 《Example 6》 Figure 18 shows the state of the first structure 4A before and after movement. The sixth configuration example differs from the fifth configuration example shown in Figure 16 in that the display module DM is fixed to the housing HS, and the variable mechanism SL is configured to move the first structure 4A. The first structure 4A here comprises a first phase difference plate R1, a semi-transparent layer HM, and a second phase difference plate R2.

[0109] The left side of the figure shows the state in which the first structure 4A is positioned at the first position P1 (before movement), and the right side of the figure shows the state in which the first structure 4A is positioned at the second position P2 (after movement). When the first structure 4A is positioned at the first position P1, a first gap G1 is formed between the second phase difference plate R2 and the reflective polarizer PR. When the first structure 4A is positioned at the second position P2, a second gap G2 is formed between the second phase difference plate R2 and the reflective polarizer PR. The second gap G2 is smaller than the first gap G1. This state is achieved by the variable mechanism SL moving the first structure 4A closer to the reflective polarizer PR.

[0110] In this sixth configuration example, when the optical system 4 is deployed, a diagram similar to that described with reference to Figure 15 is obtained. That is, as the first structure 4A moves to the second position P2, the display surface DS moves away from the second focal point FP2, and the position of the virtual image V2 moves closer to the user's pupil. Therefore, a clear image can be displayed for myopic users.

[0111] As described above, according to this embodiment, a display device equipped with a diopter adjustment function can be provided.

[0112] Although several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented 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 variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0113] 1…Head-mounted display DSP…Display device DM…Display module 2…Display panel 3…Lighting device 4…Optical system 4A…First structure 4B…Second structure 4C…Air layer R1...First retardation plate R2...Second retardation plate R3...Third retardation plate HM...Semi-transparent layer PR...Reflective polarizing plate TS...Transparent substrate 10...Liquid crystal element 20...Holographic optical element SL... Variable mechanism SP... Support

Claims

1. A display module configured to emit linearly polarized display light, A first structure comprising a first phase difference plate facing the display module, a holographic optical element facing the first phase difference plate, and a second phase difference plate facing the holographic optical element, A second structure comprising a reflective polarizing plate facing the second phase difference plate, and a transparent substrate facing the reflective polarizing plate, A variable mechanism for varying the distance between the first structure and the second structure, A display device equipped with the following features.

2. The display device according to claim 1, wherein the first phase difference plate and the second phase difference plate are quarter-wave plates.

3. A display module configured to emit linearly polarized display light, A first structure comprising a first phase difference plate facing the display module, a semi-transparent layer facing the first phase difference plate, and a second phase difference plate facing the semi-transparent layer, A second structure comprising a reflective polarizing plate facing the second phase difference plate, a third phase difference plate facing the reflective polarizing plate, and a liquid crystal element facing the third phase difference plate and having a lens effect, A variable mechanism for varying the distance between the first structure and the second structure, A display device equipped with the following features.

4. The display device according to claim 3, wherein the first phase difference plate, the second phase difference plate, and the third phase difference plate are quarter-wave plates.

5. The liquid crystal element has a liquid crystal layer in which the orientation direction of a plurality of liquid crystal molecules, including a first liquid crystal molecule and a second liquid crystal molecule, is fixed and cured. The liquid crystal layer, in a plan view, has a first annular region in which a plurality of the first liquid crystal molecules are oriented 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 oriented in the same direction. The display device according to claim 3, wherein the orientation direction of the first liquid crystal molecule is different from the orientation direction of the second liquid crystal molecule.

6. Furthermore, it comprises a housing and a support fixed to the housing, The first structure is supported by the support, The display module is positioned between the housing and the first structure. The second structure is supported by the variable mechanism, The display device according to claim 1 or 3, wherein the variable mechanism is fixed to the housing and configured to move the second structure.

7. Furthermore, it comprises a housing and a support fixed to the housing, The second structure is supported by the support, The display module is positioned between the housing and the first structure and is fixed to the first structure. The first structure and the display module are supported by the variable mechanism, The display device according to claim 1 or 3, wherein the variable mechanism is fixed to the housing and configured to move the first structure and the display module.

8. Furthermore, it comprises a housing and a support fixed to the housing, The second structure is supported by the support, The display module is positioned between the housing and the first structure and is fixed to the housing. The first structure is supported by the variable mechanism, The display device according to claim 1 or 3, wherein the variable mechanism is fixed to the housing and configured to move the first structure.

9. The display device according to claim 1 or 3, wherein the display module comprises a lighting device and a liquid crystal panel disposed between the lighting device and the first structure.

10. The display device according to claim 1 or 3, wherein an air layer is interposed between the second phase difference plate and the reflective polarizing plate.

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