Indication device

Abstract

To suppress the decrease in display quality.SOLUTION: A display device includes a display panel configured to emit display light of linear polarization light, a first holographic optical element that faces the display panel, a second holographic optical element that faces the first holographic optical element, a polarization plate that faces the second holographic optical element, transmits first linear polarization light, and absorbs second linear polarization light that is orthogonal to the first linear polarization light, a lens element that faces the polarization plate and has a lens operation of condensing first circular polarized light out of the light having transmitted the second holographic optical element, a first retardation plate that exists between the first holographic optical element and the second holographic optical element, a second retardation plate that exists between the polarization plate and the lens element, and a third retardation plate that exists between the second holographic optical element and the polarization plate.SELECTED DRAWING: Figure 3

Description

Technical Field

[0005] , ,

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

Background Art

[0002] In recent years, technology for providing, for example, virtual reality (VR: Virtual Reality) using a head-mounted display worn on a user's head has 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

[0006] According to other embodiments, the display device is The device comprises: a display panel configured to emit linearly polarized display light; a first holographic optical element facing the display panel; a second holographic optical element facing the first holographic optical element; a polarizer facing the second holographic optical element, which transmits first linearly polarized light and absorbs second linearly polarized light perpendicular to the first linearly polarized light; a lens element facing the polarizer, which has a lens effect that focuses first circularly polarized light from the light transmitted through the second holographic optical element; a first phase difference plate located between the first holographic optical element and the second holographic optical element; a second phase difference plate located between the polarizer plate and the lens element; and a third phase difference plate located between the display panel and the first holographic optical element. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a perspective view showing an example of the appearance of a head-mounted display 1 to which a display device according to one embodiment is applied. [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 an example configuration of a display device DSP (Demand-Side Programming) system. [Figure 4] Figure 4 is a cross-sectional view showing an example of the lens element LE shown in Figure 3. [Figure 5] Figure 5 is a plan view showing an example of the orientation pattern in the liquid crystal layer LC1 shown in Figure 4. [Figure 6] Figure 6 is a diagram illustrating an example of the optical operation of the DSP display device shown in Figure 3. [Figure 7] Figure 7 is a diagram illustrating the first specific incident angle θ1 of the first holographic optical element HE1 and the second specific incident angle θ2 of the second holographic optical element HE2 shown in Figure 6. [Figure 8] Figure 8 is a plan view showing one example configuration of a lighting device 3 applicable to the display device DSP shown in Figure 3. [Figure 9] Figure 9 is a cross-sectional view showing one example configuration of the head-mounted display 1. [Figure 10] Figure 10 is a cross-sectional view showing an example configuration of a DSP display device, Part 2. [Figure 11] Figure 11 is a cross-sectional view showing example configuration 3 of a display device DSP. [Figure 12] Figure 12 is a cross-sectional view showing an example configuration 4 of a display device DSP. [Modes 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] In the drawings, for ease of understanding as necessary, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are described. The direction along the X-axis is referred to as the first direction X, the direction along the Y-axis is referred to as the second direction Y, and the direction along the Z-axis is referred to as the third direction Z. The plane defined by the X-axis and the Y-axis is referred to as the X-Y plane, and viewing the X-Y plane is referred to as a plan view.

[0010] FIG. 1 is a perspective view showing an example of the appearance of a head-mounted display 1 to which the display device according to the present 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 the user wears the head-mounted display 1 on the head, the display device DSPR is arranged to be positioned in front of the right eye of the user, and the display device DSPL is arranged to be positioned in front of the left eye of the user.

[0011] FIG. 2 is a diagram for explaining an outline of the configuration of the head-mounted display 1 shown in FIG. 1.

[0012] The display device DSPR includes a display panel 2R, a lighting device 3R, and an optical system 4R shown by a dotted line. The lighting device 3R is arranged on the back surface of the display panel 2R and is configured to illuminate the display panel 2R. The optical system 4R is arranged on the front surface of the display panel (or between the right eye ER of the user and the display panel 2R) and is configured to guide display light from the display panel 2R to the right eye ER.

[0013] The display panel 2R includes, for example, a liquid crystal panel and a polarizing plate. The display panel 2R is arranged between the lighting 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).

[0014] The display device DSPL comprises a display panel 2L, an illumination device 3L, and an optical system 4L, indicated by a dotted line. The illumination device 3L is located behind the display panel 2L and is configured to illuminate the display panel 2L. The optical system 4L is located 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 the display light from the display panel 2L to the left eye EL.

[0015] The display panel 2L includes, for example, a liquid crystal panel and a polarizing plate. The display panel 2L is positioned between the illumination device 3L and the optical system 4L. 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 operation of the display panel 2L (in particular, controls the display operation of the display panel 2L).

[0016] The DSPL display device is configured substantially the same as the DSPR display device. In other words, the display panel 2R, illumination device 3R, and optical system 4R that constitute the display device DSPR are configured in the same way as the display panel 2L, illumination device 3L, and optical system 4L that constitute the display device DSPL.

[0017] In the display device DSP according to this embodiment, the display panels 2R and 2L are not limited to examples including liquid crystal panels, but may also include display panels equipped with self-emissive light-emitting elements such as organic electroluminescent (EL) elements, micro-LEDs, and mini-LEDs. If the display panels 2R and 2L 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 polarizers as needed.

[0018] An externally located host computer H is connected to display panels 2L and 2R, respectively. Host computer H outputs image data corresponding to the images displayed on display panels 2L and 2R. The image displayed on display panel 2L is for the left eye (or the image seen by the user's left eye EL). The image displayed on display panel 2R is for the right eye (or the image seen by the user's right eye ER).

[0019] For example, when 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 display panel 2L is viewed by the user's left eye EL, and the image for the right eye displayed on display panel 2R is viewed by the user's right eye ER, the user can perceive a three-dimensional space as a virtual reality space.

[0020] Furthermore, display panels 2R and 2L may be configured as a single display panel extending across the front of the left eye EL and the right eye ER. Also, lighting devices 3R and 3L may be configured as a single lighting device extending across the front of the left eye EL and the right eye ER.

[0021] Next, some configuration examples of the display device DSP according to this embodiment will be described.

[0022] 《Configuration Example 1》 Figure 3 is a cross-sectional view showing an example configuration of a display device DSP (Demand-Side Programming) system. The display device DSP comprises a display panel 2, an illumination device 3, and an optical system 4. Detailed illustrations of the display panel 2 and illumination device 3 are omitted here. 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.

[0023] The display panel 2 is formed in a flat plate shape extending across the XY plane. 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 first substrate SUB1 and the second substrate SUB2 face each other in the third direction Z. 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 lighting device 3 and the first substrate SUB1 and is, for example, bonded to the first substrate SUB1. The second polarizer PL2 is positioned between the second substrate SUB2 and the optical system 4 and is, for example, bonded to the second substrate SUB2.

[0024] 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.

[0025] In this configuration example, and in other configuration examples as well, the display panel 2 is not limited to examples that include a liquid crystal panel. When the display panel 2 includes a display panel equipped with a self-emissive light-emitting element such as an organic EL element, the illumination device 3 is omitted as described above. In this case, the display light DL emitted from the light-emitting element is transmitted through the second polarizing plate PL2 and converted into linearly polarized display light DL.

[0026] 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 example shown in Figure 3, an air layer 4C is provided between the first structure 4A and the second structure 4B. 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).

[0027] The first structure 4A comprises a first holographic optical element HE1 and a first phase difference plate R1. The first holographic optical element HE1 faces the display panel 2 in the third direction Z.

[0028] The first holographic optical element HE1 and the first phase difference plate R1 extend over a wider area than the display area DA in the XY plane. The first holographic optical element HE1 and the first phase difference plate R1 are stacked along the third direction Z and bonded to each other. The first holographic optical element HE1 is bonded to the second polarizer PL2 of the display panel 2.

[0029] The second structure 4B comprises a second holographic optical element HE2, a polarizer PL, a lens element LE, a second phase difference plate R2, and a third phase difference plate R3. The second holographic optical element HE2 faces the first holographic optical element HE1 in the third direction Z. The polarizer PL faces the second holographic optical element HE2 in the third direction Z. The lens element LE faces the polarizer PL in the third direction Z.

[0030] The first phase difference plate R1 is located between the first holographic optical element HE1 and the second holographic optical element HE2 in the third direction Z. The air layer 4C is interposed between the first phase difference plate R1 and the second holographic optical element HE2 in the third direction Z. The second phase difference plate R2 is located between the polarizer PL and the lens element LE in the third direction Z. The third phase difference plate R3 is located between the second holographic optical element HE2 and the polarizer PL in the third direction Z.

[0031] The second holographic optical element HE2, the third phase difference plate R3, the polarizer PL, the second phase difference plate R2, and the lens element LE extend over a wider area than the display area DA in the XY plane. The second holographic optical element HE2, the third phase difference plate R3, the polarizer PL, the second phase difference plate R2, and the lens element LE are stacked along the third direction Z and bonded to each other.

[0032] The first phase difference plate R1, the second phase difference plate R2, and the third phase difference plate R3 are quarter-wave plates and are configured to impart a phase difference of 1 / 4 wavelength to the transmitted light.

[0033] The polarizing plate (PL) is configured to transmit first linearly polarized light and absorb second linearly polarized light that is orthogonal to the first linearly polarized light.

[0034] The first holographic optical element HE1 and the second holographic optical element HE2 have an interference fringe pattern and a refractive index component with a period corresponding to the wavelength in the thickness direction (third direction Z). These first and second holographic optical elements HE1 and HE2 are configured to reflect and diffract a portion of the incident light. More specifically, the first holographic optical element HE1 has a virtual reflective surface RS1, and the second holographic optical element HE2 has a virtual reflective surface RS2. These reflective surfaces RS1 and RS2 are non-parallel to each other.

[0035] The first holographic optical element HE1 is configured to reflect light incident at a first specific incidence angle relative to the normal to the reflective surface RS1, and to transmit light incident at an incidence angle different from the first specific incidence angle. The light transmitted through the first holographic optical element HE1 is light incident at an incidence angle of ±10° or more relative to the first specific incidence angle.

[0036] The second holographic optical element HE2 is configured to reflect light incident at a second specific incidence angle relative to the normal of the reflective surface RS2, and to transmit light incident at an incidence angle different from the second specific incidence angle. The second specific incidence angle is a different angle from the first specific incidence angle. The light transmitted through the second holographic optical element HE2 is light incident at an incidence angle of ±10° or more relative to the second specific incidence angle.

[0037] The lens element LE, as will be described in detail later, includes a liquid crystal layer LC1. The liquid crystal layer LC1 is configured to impart a phase difference of half a wavelength to light of a specific wavelength and to have a lens effect that focuses first circularly polarized light. Note that elements having a lens effect that focuses circularly polarized light are not limited to elements that utilize liquid crystals.

[0038] The display area DA has a first end E1 and a second end E2 opposite to the first end E1 in a first direction X. The first holographic optical element HE1, the first phase difference plate R1, the second holographic optical element HE2, the third phase difference plate R3, the polarizer PL, the second phase difference plate R2, and the lens element LE each have a first portion P11 extending outward from the first end E1 and a second portion P12 extending outward from the second end E2. In the example shown in Figure 3, the first portion P11 and the second portion P12 extend along the first direction X. The width W1 of the first portion P11 along the first direction X is greater than the width W2 of the second portion P12 along the first direction X (W1 > W2).

[0039] In Figure 3, the first part P11 is located to the right of the display area DA, and the second part P12 is located to the left of the display area DA. The display light DL is emitted from the upper left to the lower right in Figure 3.

[0040] Figure 4 is a cross-sectional view showing an example of the lens element LE shown in Figure 3. The lens element LE comprises a substrate 11, an alignment film AL11, a liquid crystal layer LC1, an alignment film AL12, and a substrate 12. Substrates 11 and 12 are transparent substrates that transmit light, and are made of, for example, a transparent glass plate or a transparent synthetic resin plate.

[0041] The alignment film AL11 is positioned on the inner surface 11A of the substrate 11. In the example shown in Figure 4, 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 4, 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.

[0042] 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.

[0043] 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.

[0044] 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).

[0045] 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. Therefore, the lens element LE does not have electrodes for orientation control.

[0046] 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.

[0047] Figure 5 is a plan view showing an example of the orientation pattern in the liquid crystal layer LC1 shown in Figure 4. Figure 5 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.

[0048] 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.

[0049] For example, the liquid crystal layer LC1 has a first annular region C1 and a second annular region C2 in a plan view. 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 oriented in the same direction. The second annular region C2 is composed of a plurality 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.

[0050] 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.

[0051] When a first circularly polarized light of a specific wavelength λ is incident on a lens element LE with this configuration, the first circularly polarized light is focused toward the center of the concentric circles, and the light transmitted through the lens element LE is converted into a second circularly polarized light that rotates in the opposite direction to the first circularly polarized light.

[0052] Figure 6 is a diagram illustrating an example of the optical operation of the DSP display device shown in Figure 3. Note that the illumination device is omitted from the illustration, and the display panel 2 is shown in a simplified form.

[0053] First, the display panel 2 emits display light DL, which is a 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 plane of the paper. The display light DL is emitted obliquely to the normal NP of the display panel 2. The display light DL is incident on the first holographic optical element HE1. The incident angle θA of the first linearly polarized light LP1 incident on the first holographic optical element HE1 is different from the first specific incident angle θ1 in the first holographic optical element HE1. Here, the incident angle is the angle between the incident light and the normal N1 of the virtual reflective surface RS1. Therefore, the first linearly polarized light LP1 with an incident angle θA is transmitted through the first holographic optical element HE1.

[0054] The first linearly polarized light LP1, which has passed through the first holographic optical element HE1, has a phase difference of 1 / 4 wavelength added to it when it passes through the first phase difference plate R1. Therefore, the first linearly polarized light LP1 is converted to the first circularly polarized light CP1 when it passes through the first phase difference plate R1. Here, the first circularly polarized light CP1 is, for example, a left-handed circularly polarized light.

[0055] The first circularly polarized light CP1, transmitted through the first phase difference plate R1, is incident on the second holographic optical element HE2. The angle of incidence θC of the first circularly polarized light CP1 incident on the second holographic optical element HE2 is approximately equal to the second specific angle of incidence θ2 in the second holographic optical element HE2. Here, the angle of incidence is the angle between the incident light and the normal N2 of the virtual reflective surface RS2. The first circularly polarized light CP1 at the angle of incidence θC is reflected back towards the first holographic optical element HE1 by the reflective surface RS2 of the second holographic optical element HE2. The reflected light at the reflective surface RS2 is the second circularly polarized light CP2, which is polarized in the opposite direction to the first circularly polarized light CP1.

[0056] The second circularly polarized light CP2, reflected by the second holographic optical element HE2, is converted back into the second linearly polarized light LP2 when it passes through the first phase difference plate R1. Here, the second linearly polarized light LP2 is, for example, linearly polarized light that vibrates in a direction parallel to the plane of the paper. The second linearly polarized light LP2 that has passed through the first phase difference plate R1 is incident on the first holographic optical element HE1. The incident angle θB of the second linearly polarized light LP2 incident on the first holographic optical element HE1 is approximately equal to the first specific incident angle θ1 in the first holographic optical element HE1. Therefore, the second linearly polarized light LP2 with an incident angle θB is reflected by the reflective surface RS1 of the first holographic optical element HE1 toward the second holographic optical element HE2.

[0057] The second linearly polarized light LP2, reflected by the first holographic optical element HE1, is converted back into the second circularly polarized light CP2 when it passes through the first phase difference plate R1. The second circularly polarized light CP2 that has passed through the first phase difference plate R1 is incident on the second holographic optical element HE2. The incident angle θD of the second circularly polarized light CP2 incident on the second holographic optical element HE2 is different from the second specific incident angle θ2 in the second holographic optical element HE2. Therefore, the second circularly polarized light CP2 with an incident angle θD is transmitted through the second holographic optical element HE2.

[0058] The second circularly polarized light CP2, having passed through the second holographic optical element HE2, is converted to the first linearly polarized light LP1 when it passes through the third phase difference plate R3. The first linearly polarized light LP1, having passed through the third phase difference plate R3, passes through the polarizer PL. The first linearly polarized light LP1, having passed through the polarizer PL, is converted to the first circularly polarized light CP1 when it passes through the second phase difference plate R2. The first circularly polarized light CP1, having passed through the second phase difference plate R2, is converted to the second circularly polarized light CP2 in the lens element LE and, under the lens effect, is focused towards the user's pupil E.

[0059] In such a display device DSP, the optical system 4 has an optical path that passes between the first holographic optical element HE1 and the second holographic optical element HE2 three times. Moreover, this optical path includes an oblique optical path from the first holographic optical element HE1 to the second holographic optical element HE2, and an oblique optical path from the second holographic optical element HE2 to the first holographic optical element HE1. In other words, in the optical system 4, the optical distance between the first holographic optical element HE1 and the second holographic optical element HE2 is more than three times the actual distance between the first holographic optical element HE1 and the second holographic optical element HE2 (or the thickness of the air layer 4C). The display panel 2 is positioned inside the focal point of the lens element LE, which has a lensing effect. This allows the user to observe a magnified virtual image.

[0060] In order to realize an optical path that passes three times between the first holographic optical element HE1 and the second holographic optical element HE2, it is important that the display light DL is emitted from the display panel 2 at an angle such that it passes through the first holographic optical element HE1 and is reflected by the second holographic optical element HE2.

[0061] If a portion of the display light DL is emitted from the display panel 2 at an angle that allows it to pass through the first holographic optical element HE1 and the second holographic optical element HE2, it may be observed by the user at a different magnification than light that has passed through the normal optical path, potentially causing multiple images (so-called ghosting).

[0062] In contrast, according to Configuration Example 1, light transmitted through the first holographic optical element HE1 and the second holographic optical element HE2 is absorbed by the polarizer PL. That is, the first linearly polarized light LP1 transmitted through the first holographic optical element HE1 is converted to the first circularly polarized light CP1 when it passes through the first phase difference plate R1. This first circularly polarized light CP1 passes through the second holographic optical element HE2 and, when it passes through the third phase difference plate R3, is converted to the second linearly polarized light and absorbed by the polarizer PL. Light that has passed through the normal optical path is converted to the first linearly polarized light LP1 when it passes through the third phase difference plate R3 and passes through the polarizer PL. As a result, unwanted light is not observed by the user, and a decrease in display quality can be suppressed.

[0063] Furthermore, if absorption by each component constituting the display device DSP and reflection between components are ignored, almost 100% of the display light DL emitted from the display panel 2 can be focused onto the pupil E, thereby improving the efficiency of light utilization.

[0064] Furthermore, compared to optical systems that utilize optical components made of glass or resin, this system allows for a thinner thickness along the third direction Z, and also achieves weight reduction.

[0065] Furthermore, the first linearly polarized light LP1, as explained with reference to Figure 6, 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.

[0066] Figure 7 is a diagram illustrating the first specific incident angle θ1 of the first holographic optical element HE1 and the second specific incident angle θ2 of the second holographic optical element HE2 shown in Figure 6.

[0067] In the first holographic optical element HE1, the angle between the normal N1 of the reflective surface RS1 and the reference plane (XY plane) is defined as γ1, and the angle between the incident light at incident angle β and the normal N1 is defined as α1. In the second holographic optical element HE2, the angle between the normal N2 of the reflective surface RS2 and the reference plane (XY plane) is defined as γ2, the angle between the reflected light from the reflective surface RS2 and the reference plane is defined as φ2, and the angle between the reflected light from the reflective surface RS1 and the normal N2 is defined as α2.

[0068] As shown by c in the figure, the following equation is derived based on the condition that light at a first specific incident angle θ1 is reflected by the reflective surface RS1. γ1 = π / 2 - θ1 As shown in b in the figure, the following equation is derived based on the condition that light at a second specific incident angle θ2 is reflected by the reflective surface RS2. γ2 = θ2 - 2·θ1 + π / 2 As shown in a in the figure, the conditions for transmission through the first holographic optical element HE1 are as follows: δ1 = α1 - θ1 ≠ 0 Furthermore, the following relationship holds true. α1=2·θ2+φ2-γ1, φ2=π / 2-2·θ1 Based on these relationships, the following equation can be derived for δ1. δ1 = 2·(θ1-θ2)≠0 Therefore, θ1 ≠ θ2.

[0069] As shown by d in the figure, the conditions for transmission through the second holographic optical element HE2 are as follows: δ² = α² - θ² ≠ 0 Furthermore, the following relationship holds true. α² = π / 2 - γ² The following equation can be derived for δ². δ² = 2·(θ1-θ²)≠0 Therefore, θ1 ≠ θ2.

[0070] In other words, the optical system 4 of Configuration Example 1 is established because the first specific incident angle θ1 is different from the second specific incident angle θ2. Furthermore, the larger the difference between the first specific incident angle θ1 and the second specific incident angle θ2, the more relaxed the conditions for transmission through the first holographic optical element HE1 and the second holographic optical element HE2, which is preferable.

[0071] At this time, the angle of incidence β is as follows: β = α1 + γ1 - π / 2 = 2·(θ2 - θ1)

[0072] Figure 8 is a plan view showing one example configuration of a lighting device 3 applicable to the display device DSP shown in Figure 3. Note that only the main parts of the lighting device 3 are shown in Figure 8. The lighting device 3 comprises a light guide plate LG, a first light source unit LS1, and a second light source unit LS2.

[0073] The light guide plate LG has a side surface S1 and a side surface S2. Side surfaces S1 and S2 face each other in a first direction X. The light guide plate LG also has regions A1, A2, and A3. The thickness of region A2 along a third direction Z is approximately constant. The thickness of region A1 gradually increases from side surface S1 toward region A2. The thickness of region A3 gradually increases from side surface S2 toward region A2.

[0074] The first light source unit LS1 is arranged along the side surface S1. The second light source unit LS2 is arranged along the side surface S2. Each of the first light source unit LS1 and the second light source unit LS2 is equipped with a plurality of light-emitting elements LDs. Specifically, the first light source unit LS1 and the second light source unit LS2 are equipped with a first light-emitting element LDB configured to emit blue wavelength (first wavelength) light, a second light-emitting element LDG configured to emit green wavelength (second wavelength) light, and a third light-emitting element LDR configured to emit red wavelength (third wavelength) light. The first light-emitting element LDB, the second light-emitting element LDG, and the third light-emitting element LDR are arranged at intervals.

[0075] The light emitted from the light-emitting element LD should preferably have a narrow spectral width (or high color purity). For this reason, it is desirable to use a laser element as the light-emitting element LD. Let λb be the central wavelength of the blue laser light emitted from the first light-emitting element (first laser element) LDB, λg be the central wavelength of the green laser light emitted from the second light-emitting element (second laser element) LDG, and λr be the central wavelength of the red laser light emitted from the third light-emitting element (third laser element) LDR.

[0076] Such an illumination device 3 is configured to illuminate the display panel 2, and the angle of incidence of the display light DL emitted from the display panel 2 to the first holographic optical element HE1 satisfies the relationship of the angle of incidence β described with reference to Figure 7.

[0077] Figure 9 is a cross-sectional view showing one example configuration of the head-mounted display 1. The head-mounted display 1 comprises a single display panel 2, a single illumination device 3 as shown in Figure 8, optical systems 4R and 4L, and a frame FR. The display panel 2 functions as a display panel 2R for the right eye and a display panel 2L for the left eye, as shown in Figure 2. The illumination device 3 functions as an illumination device 3R for the right eye and an illumination device 3L for the left eye.

[0078] The lighting device 3 comprises a first light source unit LS1 and a second light source unit LS2, a light guide plate LG, a prism sheet PS, and a diffusion sheet DS. The prism sheet PS is positioned between the light guide plate LG and the diffusion sheet DS in a third direction Z. The diffusion sheet DS is positioned between the prism sheet PS and the display panel 2 in a third direction Z.

[0079] The first light source LS1 is located on the left side of the figure and primarily emits light guided to the optical system 4R. The second light source LS2 is located on the right side of the figure and primarily emits light guided to the optical system 4L. Each of the first light source LS1 and the second light source LS2 comprises a first light-emitting element LDB, a second light-emitting element LDG, and a third light-emitting element LDR, as described with reference to Figure 8.

[0080] 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 systems 4R and 4L.

[0081] The optical system 4L comprises a first holographic optical element HE1L, a first phase difference plate R1L, a second holographic optical element HE2L, a third phase difference plate R3L, a polarizing plate PLL, a second phase difference plate R2L, and a lens element LEL. The optical system 4R comprises a first holographic optical element HE1R, a first phase difference plate R1R, a second holographic optical element HE2R, a third phase difference plate R3R, a polarizing plate PLR, a second phase difference plate R2R, and a lens element LER.

[0082] Each of the first holographic optical elements HE1L and HE1R is configured to reflect light of the blue wavelength (first wavelength) λb, the green wavelength (second wavelength) λg, and the red wavelength (third wavelength) λr at a first specific incident angle θ1, respectively, with its reflective surface RS1.

[0083] Each of the second holographic optical elements HE2L and HE2R is configured to reflect light of the blue wavelength (first wavelength) λb at a second specific incident angle θ2, light of the green wavelength (second wavelength) λg at a second specific incident angle θ2, and light of the red wavelength (third wavelength) λr at a second specific incident angle θ2, respectively, with the reflective surface RS2.

[0084] Each of the lens elements LEL and LER comprises a first liquid crystal layer LCB, a second liquid crystal layer LCG, and a third liquid crystal layer LCR. The first liquid crystal layer LCB, the second liquid crystal layer LCG, and the third liquid crystal layer LCR are stacked along the third direction Z. Note that the stacking order of the first liquid crystal layer LCB, the second liquid crystal layer LCG, and the third liquid crystal layer LCR is not limited to the example shown.

[0085] Each of the first liquid crystal layer LCB, the second liquid crystal layer LCG, and the third liquid crystal layer LCR corresponds to the liquid crystal layer LC1 described with reference to Figures 4 and 5, and is cured with the orientation direction of multiple liquid crystal molecules fixed.

[0086] The first liquid crystal layer LCB is configured to focus the first circularly polarized light with a blue wavelength (first wavelength) λb from the incident light and to impart a phase difference of half a wavelength. The second liquid crystal layer LCG is configured to focus the first circularly polarized light with a green wavelength (second wavelength) λg from the incident light and to impart a phase difference of half a wavelength. The third liquid crystal layer LCR is configured to focus the first circularly polarized light with a red wavelength (third wavelength) λr from the incident light and to impart a phase difference of half a wavelength.

[0087] Optical systems 4R and 4L, configured in this way, exhibit the optical effects described with reference to Figure 6.

[0088] In the head-mounted display 1 described above, the first light source LS1 of the illumination device 3 emits light toward side S1, and the second light source LS2 emits light toward side S2. Light incident from side S1 and light incident from side S2 propagates while repeatedly reflecting between the upper surface T1 and lower surface B1 of the light guide plate LG. Of the light incident from side S1, light that does not meet the total internal reflection conditions at the upper surface T1 is emitted obliquely toward the optical system 4R, forming illumination light for the right eye. Of the light incident from side S2, light that does not meet the total internal reflection conditions at the upper surface T1 is emitted obliquely toward the optical system 4L, forming illumination light for the left eye.

[0089] The display panel 2 selectively modulates the illumination light from the illumination device 3. A portion of the illumination light for the left eye passes through the second polarizer PL2 and is converted into display light DLL, which is linearly polarized for the left eye. A portion of the illumination light for the right eye passes through the second polarizer PL2 and is converted into display light DLR, which is linearly polarized for the right eye.

[0090] The display light DLL is focused to the user's left eye by the optical action of the optical system 4L described above. The display light DLR is focused to the user's right eye by the optical action of the optical system 4R described above.

[0091] In this head-mounted display 1, the illumination device 3 is equipped with a laser element that emits light with a narrow spectral width, and the first holographic optical element HE1, the second holographic optical element HE2, and the lens element LE are optimized to match the central wavelength of the light emitted from the laser element. As a result, light of each wavelength can be efficiently focused, chromatic aberration can be reduced, and a clear image can be viewed by the user.

[0092] Next, other configuration examples of the display device DSP will be described. Note that in the following description, configurations identical to those in Configuration Example 1 may be given the same reference numerals and their explanation may be omitted.

[0093] 《Configuration Example 2》 Figure 10 is a cross-sectional view showing an example configuration of a DSP display device, Part 2. Configuration Example 2 shown in Figure 10 differs from Configuration Example 1 shown in Figure 3 in that the first phase difference plate R1 constitutes the second structure 4B, and an air layer 4C is interposed between the first holographic optical element HE1 and the first phase difference plate R1.

[0094] The first structure 4A is composed of the first holographic optical element HE1. The first holographic optical element HE1 is bonded to the second polarizing plate PL2 of the display panel 2.

[0095] The second structure 4B comprises a first phase difference plate R1, a second holographic optical element HE2, a second phase difference plate R2, a polarizer PL, a third phase difference plate R3, and a lens element LE. The first phase difference plate R1, the second holographic optical element HE2, the third phase difference plate R3, the polarizer PL, the second phase difference plate R2, and the lens element LE are stacked along the third direction Z and bonded to each other.

[0096] In this configuration example 2, the same effects as in the configuration example 1 described above can be obtained.

[0097] 《Configuration Example 3》 Figure 11 is a cross-sectional view showing example configuration 3 of a display device DSP. Configuration Example 3 shown in Figure 11 differs from Configuration Example 1 shown in Figure 3 in that the third phase difference plate R3 is located between the display panel 2 and the first holographic optical element HE1.

[0098] The first structure 4A comprises a first holographic optical element HE1, a first phase difference plate R1, and a third phase difference plate R3. The third phase difference plate R3, the first holographic optical element HE1, and the first phase difference plate R1 are stacked along the third direction Z and bonded to each other. The third phase difference plate R3 is bonded to the second polarizing plate PL2 of the display panel 2.

[0099] The second structure 4B comprises a second holographic optical element HE2, a polarizing plate PL, a second phase difference plate R2, and a lens element LE. An air layer 4C is interposed between the first phase difference plate R1 and the second holographic optical element HE2 in the third direction Z. The second holographic optical element HE2, the polarizing plate PL, the second phase difference plate R2, and the lens element LE are stacked and bonded to each other along the third direction Z.

[0100] In this configuration example 3, the same effects as in the configuration example 1 described above can be obtained.

[0101] 《Configuration Example 4》 Figure 12 is a cross-sectional view showing an example configuration 4 of a display device DSP. Configuration Example 4 shown in Figure 12 differs from Configuration Example 3 shown in Figure 11 in that the first phase difference plate R1 constitutes the second structure 4B, and an air layer 4C is interposed between the first holographic optical element HE1 and the first phase difference plate R1.

[0102] The first structure 4A comprises a first holographic optical element HE1 and a third phase difference plate R3. The third phase difference plate R3 and the first holographic optical element HE1 are stacked along the third direction Z and bonded to each other. The third phase difference plate R3 is bonded to the second polarizing plate PL2 of the display panel 2.

[0103] The second structure 4B comprises a first phase difference plate R1, a second phase difference plate R2, a second holographic optical element HE2, a polarizer PL, and a lens element LE. The first phase difference plate R1, the second holographic optical element HE2, the polarizer PL, the second phase difference plate R2, and the lens element LE are stacked along the third direction Z and bonded to each other.

[0104] In this configuration example 4, the same effects as in the configuration example 1 described above can be obtained.

[0105] The optical system 4 described in the above configuration examples 2 to 4 can also be applied to the head-mounted display 1 described with reference to Figure 9.

[0106] As described above, this embodiment provides a display device that can suppress a decrease in display quality.

[0107] 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]

[0108] 1…Head-mounted display DSP…Display device 2…Display panel 3…Lighting device 4…Optical system HE1...First holographic optical element RS1...Reflective surface HE2...Second holographic optical element RS2...Reflective surface PL...Polarizing plate LE...Lens element LC1...Liquid crystal layer R1…First retardation plate R2…Second retardation plate R3…Third retardation plate

Claims

1. A display panel configured to emit linearly polarized display light, A first holographic optical element facing the display panel, A second holographic optical element facing the first holographic optical element, A polarizing plate facing the second holographic optical element, which transmits first linearly polarized light and absorbs second linearly polarized light perpendicular to the first linearly polarized light, A lens element facing the polarizing plate and having a lens action that focuses the first circularly polarized light among the light transmitted through the second holographic optical element, A first phase difference plate located between the first holographic optical element and the second holographic optical element, A second phase difference plate located between the polarizing plate and the lens element, A third phase difference plate is located between the second holographic optical element and the polarizing plate, A display device equipped with the following features.

2. The first holographic optical element and the first phase difference plate are stacked, The display device according to claim 1, wherein an air layer is interposed between the first phase difference plate and the second holographic optical element.

3. The display device according to claim 2, wherein the second holographic optical element, the third phase difference plate, the polarizing plate, the second phase difference plate, and the lens element are stacked.

4. The first phase difference plate, the second holographic optical element, the third phase difference plate, the polarizing plate, the second phase difference plate, and the lens element are stacked, The display device according to claim 1, wherein an air layer is interposed between the first holographic optical element and the first phase difference plate.

5. A display panel configured to emit linearly polarized display light, A first holographic optical element facing the display panel, A second holographic optical element facing the first holographic optical element, A polarizing plate facing the second holographic optical element, which transmits first linearly polarized light and absorbs second linearly polarized light perpendicular to the first linearly polarized light, A lens element facing the polarizing plate and having a lens action that focuses the first circularly polarized light among the light transmitted through the second holographic optical element, A first phase difference plate located between the first holographic optical element and the second holographic optical element, A second phase difference plate located between the polarizing plate and the lens element, A third phase difference plate is located between the display panel and the first holographic optical element, A display device equipped with the following features.

6. The third phase difference plate, the first holographic optical element, and the first phase difference plate are stacked, The display device according to claim 5, wherein an air layer is interposed between the first phase difference plate and the second holographic optical element.

7. The display device according to claim 6, wherein the second holographic optical element, the polarizing plate, the second phase difference plate, and the lens element are stacked.

8. The third phase difference plate and the first holographic optical element are stacked, The display device according to claim 5, wherein an air layer is interposed between the first phase difference plate and the first holographic optical element.

9. The display device according to claim 8, wherein the first phase difference plate, the second holographic optical element, the polarizing plate, the second phase difference plate, and the lens element are stacked.

10. The display device according to any one of claims 1 to 9, wherein the first phase difference plate, the second phase difference plate, and the third phase difference plate are quarter-wave plates.

11. The first holographic optical element reflects light at a first specific incident angle and transmits light at an incident angle different from the first specific incident angle. The display device according to any one of claims 1 to 9, wherein the second holographic optical element reflects light at a second specific incident angle different from the first specific incident angle and transmits light at an incident angle different from the second specific incident angle.

12. When the angle of incidence of the display light onto the first holographic optical element is β, the first specific incidence angle is θ1, and the second specific incidence angle is θ2, β=2・(θ2−θ1) The display device according to claim 11, wherein the following relationship holds true.

13. Furthermore, it is equipped with a lighting device located on the back of the display panel, The display device according to claim 12, wherein the illumination device comprises a first light-emitting element configured to emit light of a first wavelength, a second light-emitting element configured to emit light of a second wavelength different from the first wavelength, and a third light-emitting element configured to emit light of a third wavelength different from the first and second wavelengths, and is configured to form light at the incident angle β.

14. The display device according to claim 13, wherein the first light-emitting element, the second light-emitting element, and the third light-emitting element are each laser elements.

15. The lens element comprises a first liquid crystal layer, a second liquid crystal layer superimposed on the first liquid crystal layer, and a third liquid crystal layer superimposed on the second liquid crystal layer. Each of the first liquid crystal layer, the second liquid crystal layer, and the third liquid crystal layer is cured in a state in which the orientation direction of the plurality of liquid crystal molecules is fixed. The first liquid crystal layer focuses the first circularly polarized light of the first wavelength, The second liquid crystal layer focuses the first circularly polarized light of the second wavelength, The display device according to claim 13, wherein the third liquid crystal layer focuses the first circularly polarized light of the third wavelength.

16. Each of the first liquid crystal layer, the second liquid crystal layer, and the third liquid crystal layer has, in a plan view, a first annular region in which a plurality of 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 second liquid crystal molecules are oriented in the same direction. The display device according to claim 15, wherein the orientation direction of the first liquid crystal molecule is different from the orientation direction of the second liquid crystal molecule.

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