Optical system and display device

Abstract

And an optical system that images light from the display panel on the retina when combined with the eyeball, and that includes: a first refractive lens; a second refractive lens between the first refractive lens and the display panel; a third refractive lens between the second refractive lens and the display panel; and a diffractive lens located between the first refractive lens and the second refractive lens or between the second refractive lens and the third refractive lens. The optical system is configured such that light from the display panel passes three times through the second refractive lens by folding back an optical path, and the diffractive lens is configured such that a converted portion curvature of each portion varies according to a distance from an optical axis.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical system and a display device. BACKGROUND

[0002] A display device such as a head-mounted display (HMD) device uses a so-called three-pass optical system in which light from a display panel passes through the same refractive lens three times by making the light path fold back (for example, refer to Patent Literature 1).

[0003] LIST OF CITATIONS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: WO2021 / 106048A SUMMARY

[0006] TECHNICAL PROBLEM

[0007] In the display device and the optical system as described above, there is still room for research for improving the resolution and the viewing angle. Since the optical system already includes some lenses, it is not easy to achieve improvement in the resolution and the viewing angle by increasing the refractive lens while maintaining sufficient edge thickness. In addition, it is necessary to address the magnification chromatic aberration.

[0008] One aspect of the present disclosure is to achieve improvement in the resolution and the viewing angle while suppressing the magnification chromatic aberration.

[0009] SOLUTION TO PROBLEM

[0010] An optical system according to one aspect of the present disclosure is an optical system that images light from a display panel on a retina when combined with an eyeball, the optical system including: a first refractive lens; a second refractive lens between the first refractive lens and the display panel; a third refractive lens between the second refractive lens and the display panel; and a diffractive lens between the first refractive lens and the second refractive lens or between the second refractive lens and the third refractive lens, wherein in the optical system, the light from the display panel passes through the second refractive lens three times by making the light path fold back, and a conversion partial curvature of each portion of the diffractive lens varies according to a distance from an optical axis.

[0011] A display device according to one aspect of the present disclosure includes a display panel; and an optical system that, when combined with an eyeball, images light from the display panel on a retina, wherein the optical system includes a first refractive lens, a second refractive lens between the first refractive lens and the display panel, a third refractive lens between the second refractive lens and the display panel, and a diffractive lens between the first refractive lens and the second refractive lens or between the second refractive lens and the third refractive lens, in the optical system, light from the display panel passes through the second refractive lens three times by making a light path turn back, and a reduced partial curvature of each portion of the diffractive lens varies according to a distance from an optical axis. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 FIG. 1 is a set of diagrams showing an example of a schematic configuration of a display device 1 according to an embodiment.

[0013] Figure 2 FIG. 3 is a diagram showing an example of a schematic configuration of an optical system 3.

[0014] Figure 3 FIG. 8 is a diagram showing an example of a schematic configuration of a diffractive lens 8.

[0015] Figure 4 FIG. 10 is a diagram showing an example of a reduced partial curvature K of the diffractive lens 8.

[0016] Figure 5 FIG. 14 is a diagram showing an example of a schematic configuration of a refractive lens 4-1.

[0017] Figure 6 FIG. 16 is a diagram showing an example of a reduced partial curvature K of the refractive lens 4-1.

[0018] Figure 7 FIG. 18 is a diagram showing an example of a schematic configuration of a refractive lens 4-3.

[0019] Figure 8 FIG. 20 is a diagram showing an example of a reduced partial curvature K of the refractive lens 4-3.

[0020] Figure 9 FIG. 22 is a diagram showing a design example.

[0021] Figure 10 FIG. 24 is a diagram showing a design example.

[0022] Figure 11 FIG. 26 is a set of diagrams showing a design example.

[0023] Figure 12 FIG. 28 is a set of tables showing a design example.

[0024] Figure 13 is a set of tables showing design examples.

[0025] Figure 14 is a graph showing design examples.

[0026] Figure 15 is a set of tables showing design examples.

[0027] Figure 16 is a graph showing design examples.

[0028] Figure 17 is a set of graphs showing examples of the schematic configuration of the display device 1.

[0029] Figure 18 is a graph showing design examples.

[0030] Figure 19 is a graph showing design examples.

[0031] Figure 20 is a set of graphs showing design examples.

[0032] Figure 21 is a set of tables showing design examples.

[0033] Figure 22 is a set of tables showing design examples.

[0034] Figure 23 is a graph showing design examples.

[0035] Figure 24 is a set of tables showing design examples.

[0036] Figure 25 is a set of graphs showing design examples.

[0037] Figure 26 is a set of graphs showing examples of the schematic configuration of the display device 1.

[0038] Figure 27 is a graph showing design examples.

[0039] Figure 28 is a graph showing design examples.

[0040] Figure 29 is a set of graphs showing design examples.

[0041] Figure 30 is a set of tables showing design examples.

[0042] Figure 31 is a set of tables showing design examples.

[0043] Figure 32 is a graph showing design examples.

[0044] Figure 33 is a set of tables showing design examples.

[0045] Figure 34 is a set of diagrams showing design examples.

[0046] Figure 35 is a set of diagrams showing examples of schematic configurations of the display device 1.

[0047] Figure 36 is a diagram showing an example of a schematic configuration of the optical system 3.

[0048] Figure 37 is a diagram showing a design example.

[0049] Figure 38 is a diagram showing a design example.

[0050] Figure 39 is a set of diagrams showing design examples.

[0051] Figure 40 is a set of tables showing design examples.

[0052] Figure 41 is a set of tables showing design examples.

[0053] Figure 42 is a diagram showing a design example.

[0054] Figure 43 is a set of tables showing design examples.

[0055] Figure 44 is a set of diagrams showing design examples. DETAILED DESCRIPTION

[0056] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following embodiments, the same elements are denoted by the same reference numerals, and overlapping description can be omitted. The same reference numerals can be used for different meanings between different embodiments. In this case, the elements assigned with the same reference numerals can be interpreted according to the description in each embodiment.

[0057] The present disclosure will be described in the following item order.

[0058] 0. INTRODUCTION

[0059] 1. EMBODIMENT

[0060] 2. MODIFIED EXAMPLE

[0061] 3. SUMMARY

[0062] 0. INTRODUCTION

[0063] A display device such as an HMD includes an optical system that, when combined with an eyeball, serves to image light from a display panel on a retina and display an image. There are also many cases where the optical system has included a number of lenses. Thus, it is not easy to improve the resolution and the viewing angle by increasing the refractive lens while maintaining a sufficient edge thickness. Furthermore, there arises a problem to be solved in relation to the lateral chromatic aberration.

[0064] For example, a method of suppressing the lateral chromatic aberration by incorporating a concave lens and a convex lens into the optical system is considered. However, in this case, the distance from the pupil position to the reflecting surface in the optical system increases, and the effective diameter increases. This leads to a further reduction in the edge thickness. Thus, it is difficult to improve the resolution and the viewing angle.

[0065] At least some of the above problems are solved by the technology disclosed herein. Although details will be described later, by using a diffractive lens having a non-constant reduction portion curvature together with a refractive lens, it is possible to achieve an improvement in the resolution and the viewing angle while suppressing the lateral chromatic aberration. The specific refractive lens and the diffractive lens are balanced, and the contribution given by the balance of the lateral chromatic aberration in the optical system as a whole by the other refractive lenses is negligible. Thus, the reduction portion curvatures of the specific refractive lens and the diffractive lens can have the same sign on the same axis. In the intermediate image height band, the astigmatism and the field curvature are canceled by the negative partial curvature of the specific refractive lens, and the reduction portion curvature of the diffractive lens is also negative. Thus, the lateral chromatic aberration is balanced. As a result, it is possible to achieve an improvement in the resolution and the viewing angle while obtaining a high aberration correction effect.

[0066] Embodiment 1

[0067] Figure 1 is a set of drawings showing an example of a schematic configuration of a display device 1 according to an embodiment. The display device 1 is, for example, an HMD device that displays an image for virtual reality (VR), and Figure 1 (A) of FIG. 1 schematically shows an eyeball of a user U who wears and uses the display device 1. The eyeball (e.g., pupil) of the user U is located at or near a position where light from one point at the display device 1 is substantially parallel light, and the user U observes an image (which can be interpreted as containing a picture image). In the drawing, the position where the light is substantially parallel light is referred to as and shown as a pupil position P (pupil plane).

[0068] An XYZ coordinate system is also shown in the drawing. The display device 1 and the user U are located in this order in the positive direction of the Z axis. Unless otherwise stated, it is assumed that each element of the display device 1 extends in the XY plane direction and has a thickness in the Z axis direction. In Figure 1In (A) of FIG. 1, a side surface (which can be a cross section) of the display device 1 when viewed in the X-axis direction is schematically shown. In (B) of FIG. 1, several light paths (also referred to as light rays, luminous fluxes, etc.) are schematically shown. Figure 1 In (B) of FIG. 1, several light paths (also referred to as light rays, luminous fluxes, etc.) are schematically shown.

[0069] The display device 1 includes a display panel 2 and an optical system 3. The display panel 2 and the optical system 3 are arranged in this order in the Z-axis positive direction. Note that, Figure 1 (A) of FIG. 1 shows the optical axis OA of the optical system 3 by using a single-dot chain line.

[0070] The display panel 2 includes, for example, an organic light-emitting diode (OLED), a liquid crystal (LC), or a light-emitting diode (LED). In the figure, the display surface of the display panel 2 is referred to as and shown as a display surface 2a.

[0071] The optical system 3 images light from the display panel 2 on the retina when combined with the eyeball. The optical system 3 includes a refractive lens 4, a semi-transparent mirror 5, a polarizer 6 (polarizing plate), a QWP 7 (1 / 4 wavelength plate), and a diffractive lens 8. The number of each of at least some of these optical elements can be two or more. In this example, there are multiple refractive lenses 4, multiple polarizers 6, and multiple QWPs 7. A plate can be interpreted as including a film.

[0072] In the figure, the first refractive lens of the multiple refractive lenses 4 is referred to as and shown as a refractive lens 4-1. In the figure, the second refractive lens is referred to as and shown as a refractive lens 4-2. In the figure, the third refractive lens is referred to as and shown as a refractive lens 4-3. When they are not particularly distinguished from each other, they are each simply referred to as a refractive lens 4.

[0073] The positional relationship between the refractive lenses 4 is as follows. The refractive lens 4-1 is located at a position opposite to the pupil position P. The refractive lens 4-2 is located between the refractive lens 4-1 and the display panel 2. The refractive lens 4-3 is located between the refractive lens 4-2 and the display panel 2.

[0074] Each refractive lens 4 is designed to make light from the display panel 2 as a whole approach the optical axis OA (i.e., to make the light converge toward the optical axis OA). For example, the refractive lens 4-1 has a positive focal length. This makes it possible to maintain the balance of chromatic aberration, particularly the balance of the optical power of the optical system as a whole. The refractive lens 4-2 has a positive optical power, and the semi-transparent mirror 5 (used as a semi-transmissive film surface) described later is disposed on the display panel 2 side (Z-axis positive direction side).

[0075] From the viewpoint of suppressing chromatic aberration at magnification, the Abbe number of each refractive lens 4 can be designed. The Abbe number is referred to as the Abbe number vd. Refractive lens 4-1 can have a predetermined value or a smaller Abbe number vd. From the viewpoint of balancing the amount of correction for chromatic aberration at magnification with the diffractive lens 8, the predetermined value can be set to a low value, and can be, for example, 30 or 20. Refractive lens 4-2 can have a predetermined value or a larger Abbe number vd, and refractive lens 4-3 can have a predetermined value or a smaller Abbe number vd. Chromatic aberration at magnification can be suppressed in the region including the optical axis OA while maintaining color balance.

[0076] In the figure, the first polarizer of the plurality of polarizers 6 is referred to as and shown as polarizer 6-1. The second polarizer is referred to as and shown as polarizer 6-2. When they are not specifically distinguished from each other, they are each simply referred to as polarizer 6. Polarizer 6 can be a polarizing plate. A plate can be interpreted as including a film.

[0077] The first of the multiple QWPs 7 is referred to as QWP 7-1. In the diagram, the second QWP is referred to as and shown as QWP 7-2. When they are not specifically distinguished from each other, they are each simply referred to as QWP 7.

[0078] exist Figure 1 In the example shown in (A), the refractive lens 4-3, polarizer 6-2, QWP 7-2, diffractive lens 8, translucent mirror 5, refractive lens 4-2, QWP 7-1, polarizer 6-1, and refractive lens 4-1 are arranged in this order along the positive Z-axis. Light from display panel 2 passes through these optical elements and is approximately parallel at the pupil position P. Note that in the following description, light traveling along the positive Z-axis in optical system 3 can be simply referred to as light from display panel 2.

[0079] The refractive lens 4-3 is located between the display panel 2 and the polarizer 6-2. Light from the display panel 2 passes through the refractive lens 4-3 and enters the polarizer 6-2.

[0080] Polarizer 6-2, QWP 7-2, diffractive lens 8, translucent mirror 5, refracting lens 4-2, QWP 7-1, polarizer 6-1, and refracting lens 4-1 constitute a so-called triple-pass optical system. For example, this configuration can contribute to the thinning and miniaturization of optical system 3. Although details will be described later, optical system 3 is configured such that light from display panel 2 passes three times through refracting lens 4-2 by reversing the light path. Finally, the light further passes through refracting lens 4-1 and is guided into approximately parallel light at pupil position P.

[0081] Among the components related to the three-pass optical system 3, first, the refractive lens 4-2 and the semi-transparent mirror 5 will be described. The refractive lens 4-2 is located between the semi-transparent mirror 5 and the QWP 7-1, and collects light from the display panel 2. The semi-transparent mirror 5 is located between the diffractive lens 8 and the refractive lens 4-2, and allows a portion (e.g., about 50%) of the incident light to pass through, and reflects the remaining portion. The semi-transparent mirror 5 can be a film (semi-transparent mirror film) provided on the surface of the refractive lens 4-2 on the side (Z-axis negative direction side) of the display panel 2.

[0082] One of the features of the optical system 3 shown is that the three-pass optical system 3 incorporates the diffractive lens 8. The diffractive lens 8 is located at least on the side (eyeball side, Z-axis positive direction side) of the pupil position P with respect to the refractive lens 4-3. In the example shown in Figure 1 In the example shown in

[0083] The thickness of the diffractive lens 8 can be smaller than the thickness of the refractive lens 4. This configuration can contribute to the thinness and smallness of the optical system 3, compared to the case where the optical system 3 incorporates an additional refractive lens. Further details of the optical system 3 including the diffractive lens 8 will be described with reference to Figure 2

[0084] Figure 2 is a diagram showing an example of a schematic configuration of the optical system 3. The illustration of the refractive lens 4-3 is omitted. Figure 2 Several optical elements are shown spaced apart; however, in actuality, the optical elements can be arranged at a smaller spacing than shown, and further, can be arranged adjacent to each other or overlapping each other.

[0085] In Figure 2 In the example shown in

[0086] The polarizer 6-2 passes only a specific polarized light, and reflects other polarized light. The polarizer 6-2 is, for example, a polarizer or a wire-grid polarizer. In this example, the polarizer 6-2 passes Y-polarized light.

[0087] ​The polarizer 6-2 is configured to limit the polarized light entering the subsequent QWP 7-2. This configuration is effective, for example, when the display panel 2, such as an OLED, emits light including various types of polarized light. When the display panel 2, such as an LCD, emits only light including a specific polarized light, the polarizer 6-2 can be omitted.

[0088] QWP 7-2 converts linearly polarized light from polarizer 6-2 into circularly polarized light. In this example, QWP 7-2 converts Y-polarized light from polarizer 6-2 into counterclockwise circularly polarized light.

[0089] Counterclockwise circularly polarized light from QWP 7-2 enters diffraction lens 8. Diffraction lens 8 can be a polarizing diffraction lens. This configuration makes it easy to handle oblique incidence and wavelength changes. Furthermore, it can effectively guide the light and easily shear off light spots and ghosting. Unless otherwise stated, diffraction lens 8 is a polarizing diffraction lens.

[0090] The diffraction lens 8 is configured such that the diffraction order is reversed according to the polarization direction of the incident circularly polarized light. The diffraction lens 8 functions as a lens. The polarization direction (rotation direction) of the circularly polarized light exiting the diffraction lens 8 is opposite to the polarization direction of the circularly polarized light incident on the diffraction lens 8. Figure 2 In the example shown, counterclockwise circularly polarized light from QWP 7-2 enters diffraction lens 8. Therefore, the circularly polarized light exiting diffraction lens 8 is clockwise circularly polarized light.

[0091] The diffractive lens 8 is also known as a polarization-orientation plane lens, a Pancharatnam-Berry phase lens, a geometric phase lens, etc. Various known configurations can be employed. Some examples are briefly described below. For instance, the diffractive lens 8 can have a configuration where a photoalignment film and a liquid crystal layer are sequentially disposed on a substrate (single-layer planar configuration). The photoalignment film is exposed by polarization interference, and the liquid crystal layer is aligned along the photoalignment film. Additional photoalignment films and additional liquid crystal layers can be disposed on the liquid crystal layer (two-layer planar configuration). Furthermore, various known configurations, such as a two-layer twisted configuration, can be employed. Various known manufacturing methods can be used to manufacture the diffractive lens 8.

[0092] A portion of the clockwise circularly polarized light from the diffraction lens 8 passes through the semi-transparent mirror 5, further through the refractive lens 4-2, and enters the QWP 7-1.

[0093] The QWP 7-1 converts the clockwise circularly polarized light that has passed through the refractive lens 4-2 into Y-polarized light. In this example, the polarizer 6-1 passes X-polarized light and reflects Y-polarized light. Thus, the Y-polarized light from the QWP 7-1 is reflected by the polarizer 6-1 and enters the QWP 7-1 again. The QWP 7-1 converts the Y-polarized light from the polarizer 6-1 into clockwise circularly polarized light. This clockwise circularly polarized light passes through the refractive lens 4-2, and a portion thereof is reflected by the semi-transparent mirror 5. The reflected light becomes counterclockwise circularly polarized light, passes through the refractive lens 4-2, and enters the QWP 7-1. In this way, the light passes through the refractive lens 4-2 three times by making the optical path return.

[0094] The QWP 7-1 also converts the counterclockwise circularly polarized light that has passed through the refractive lens 4-2 into X-polarized light. This X-polarized light passes through the polarizer 6-1 and enters the Figure 1 The above-described refractive lens 4-1 shown in FIG. 6A. The light from the refractive lens 4-1 is substantially parallel light at the pupil position P, and the user U observes an image.

[0095] The QWP 7-1 and the polarizer 6-1 can each be a film provided on a surface on the display panel 2 side of the refractive lens 4-1.

[0096] The three-pass optical system 3 using polarized light as described above can prevent a decrease in efficiency and reduce the influence of a flare caused by light propagating on an undesired path.

[0097] According to the above-described configuration, since the optical system 3 includes not only the refractive lens 4 but also the diffractive lens 8, the lens function can be improved accordingly. With the improvement in the lens function, the possibility of achieving an increase in resolution and viewing angle increases.

[0098] It is also important to address the magnification chromatic aberration. To increase the resolution and viewing angle while suppressing the magnification chromatic aberration, a design of the conversion partial curvature of the diffractive lens 8 is conceived. The conversion partial curvature is also referred to as a conversion partial curvature K. The conversion partial curvature K is a value obtained by converting the phase retardation amount given to light into the curvature of an aspherical surface for each portion of the lens.

[0099] The conversion partial curvature K represents a value obtained by converting the phase retardation amount given by each portion of the lens (specifically, the surface of the lens) into the curvature of an aspherical surface. In other words, the conversion partial curvature K is obtained by performing positive / negative inversion on the phase partial curvature. When positive, the conversion partial curvature K indicates condensing power. For example, light that has passed through a portion for which the value of the conversion partial curvature K is positive is oriented close to the optical axis OA (i.e., condensing power).

[0100] A specific description will be given of the reduced partial curvature K of the diffractive lens 8, the refractive lens 4-1, and the refractive lens 4-3 included in the lenses in the optical system 3.

[0101] The diffractive lens 8 is configured so that the reduced partial curvature K of each portion varies (is not constant) according to the distance from the optical axis OA. The distance from the optical axis OA is referred to as the distance h. The reduced partial curvature can be expressed by a function of the distance h. This will be described with reference to Figure 3 and Figure 4 .

[0102] Figure 3 is a diagram showing an example of a schematic configuration of the diffractive lens 8. The diffractive lens 8 is schematically shown as viewed from the front (viewed in the Z-axis direction). In this example, the diffractive lens 8 has a circular shape with a center on the optical axis OA. The radius of the diffractive lens 8 is referred to as the radius D.

[0103] The diffractive lens 8 has a central portion 80, an intermediate portion 81, and an outer peripheral portion 82. The central portion 80 is a portion including the center of the diffractive lens 8. The outer peripheral portion 82 is a portion including the outermost periphery of the diffractive lens 8 (also referred to as an edge portion including an edge). The intermediate portion 81 is a portion located between the central portion 80 and the outer peripheral portion 82. Using the distance h, the central portion 80 is a portion corresponding to a range of the distance h that is relatively small (including h = 0). The outer peripheral portion 82 is a portion corresponding to a range of the distance h that is relatively large (including h = D). The intermediate portion 81 is a portion corresponding to a range of the distance h that is between the two (excluding h = 0 or h = D).

[0104] The reduced partial curvature K of each portion of the diffractive lens 8 in the direction of the distance h is not constant, and continuously varies, for example, according to the distance h.

[0105] Figure 4 is a diagram showing an example of the reduced partial curvature K of the diffractive lens 8. The vertical axis of the diagram represents the distance h. The horizontal axis of the diagram represents the reduced partial curvature K. As the distance, the distance h0, the distance h1, and the distance h2 are shown.

[0106] The distance h0 is an arbitrary distance h within the range of the central portion 80 of the diffractive lens 8. The distance h1 is an arbitrary distance h within the range of the intermediate portion 81 of the diffractive lens 8. The distance h2 is an arbitrary distance h within the range of the outer peripheral portion 82 of the diffractive lens 8.

[0107] The central portion 80 of the diffractive lens 8 (at a distance h0) can have a positive reduced partial curvature K. The intermediate portion 81 of the central portion 80 (at a distance h1) can have a negative reduced partial curvature K. The outer peripheral portion 82 of the diffractive lens 8 (at a distance h2) can have a positive reduced partial curvature K. The following can hold.

[0108] K(h0) > 0

[0109] K(h1) < 0

[0110] K(h2) > 0

[0111] The reduced partial curvature K(h1) of the intermediate portion 81 of the diffractive lens 8 can be smaller than the reduced partial curvature K(h0) of the central portion 80, and can be smaller than the reduced partial curvature K(h2) of the outer peripheral portion 82. The following can hold.

[0112] K(h1) < K(h0)

[0113] K(h1) < K(h2)

[0114] For example, by designing the diffractive lens 8 such that the reduced partial curvature K of each portion of the diffractive lens 8 varies (is not constant) according to the distance h as described above, it is possible to achieve an increase in resolution and viewing angle while reducing the magnification chromatic aberration. More specifically, since the diffractive lens 8 includes the intermediate portion 81 having a negative reduced partial curvature K(h1), it is possible to reduce the magnification chromatic aberration. In addition, since the diffractive lens 8 includes the outer peripheral portion 82 having a positive reduced partial curvature K(h2) (the reduced partial curvature K of the maximum image height portion is positive), the diffractive lens 8 can correspond to the refractive lens 4-3 described later, and it is possible to reduce the astigmatism and the curvature of field.

[0115] The refractive lens 4-1 is also configured such that the reduced partial curvature of each portion varies (is not constant) according to the distance h from the optical axis OA. This will be described with reference to Figure 5 and Figure 6 .

[0116] Figure 5 is a diagram showing an example of a schematic configuration of the refractive lens 4-1. The refractive lens 4-1 is schematically shown as viewed from the front (viewed in the Z-axis direction). In this example, the refractive lens 4-1 has a circular shape with a center on the optical axis OA. The radius of the refractive lens 4-1 is referred to as the radius D1.

[0117] The refractive lens 4-1 includes a central portion 40-1, an intermediate portion 41-1, and a peripheral portion 42-1. The central portion 40-1 is a portion including the center of the refractive lens 4-1. The peripheral portion 42-1 is a portion including the peripheral portion of the refractive lens 4-1. The intermediate portion 41-1 is a portion located between the central portion 40-1 and the peripheral portion 42-1. Using a distance h, the central portion 40-1 is a portion corresponding to a range of the distance h being relatively small (including h = 0). The peripheral portion 42-1 is a portion corresponding to a range of the distance h being relatively large (including h = D1). The intermediate portion 41-1 is a portion corresponding to a range of the distance h between the two (neither including h = 0 nor including h = D1).

[0118] At least a portion of the light passing through the central portion 40-1 of the refractive lens 4-1 can be the same light as the light passing through the central portion 80 of the above-described diffractive lens 8. The same can apply to the intermediate portion 41-1 of the refractive lens 4-1 and the intermediate portion 81 of the diffractive lens 8, and the peripheral portion 42-1 of the refractive lens 4-1 and the peripheral portion 82 of the diffractive lens 8.

[0119] The refractive lens 4-1 is not constant in the refractive lens 4-1, and for example, continuously varies according to the distance h.

[0120] Figure 6 is a graph showing an example of the refractive lens 4-1. More specifically, the refractive lens 4-1 is illustrated on the sum of the refractive lens 4-1 on the surface of the pupil position P side of the refractive lens 4-1 and the surface of the display panel 2 side (for example, the surface including the polarizer 6-1) of the refractive lens 4-1. The distance h 10 is an arbitrary range of the distance h within the range of the central portion 40-1 of the refractive lens 4-1. The distance h 11 is an arbitrary range of the distance h within the range of the intermediate portion 41-1 of the refractive lens 4-1. The distance h 12 is an arbitrary distance h within the range of the peripheral portion 42-1 of the refractive lens 4-1.

[0121] The central portion 40-1 of the refractive lens 4-1 (at the distance h 10 ) can have a positive refractive portion curvature K. The intermediate portion 41-1 of the refractive lens 4-1 (at the distance h 11 ) can have a negative refractive portion curvature K. The peripheral portion 42-1 of the refractive lens 4-1 (at the distance h 12 ) can have a negative refractive portion curvature K. The following can be true.

[0122] K(h 10 ) > 0

[0123] κ(h 11 ) < 0

[0124] κ(h 12 ) < 0

[0125] In the refractive lens 4-1, the reduced portion curvature K (at a distance h 10 from the optical axis OA) of the intermediate portion 41-1 can be smaller than the reduced portion curvature K (at a distance h 11 from the optical axis OA) of the central portion 40-1. The reduced portion curvature K (at a distance h 12 from the optical axis OA) of the outer peripheral portion 42-1 can be smaller than the reduced portion curvature (at a distance h 11 from the optical axis OA) of the intermediate portion 41-1. The following can hold.

[0126] κ(h 11 ) < K(h 10 )

[0127] κ(h 12 ) < K(h 11 )

[0128] For example, by combining the use of the refractive lens 4-1 as described above and the above-described diffractive lens 8, it is possible to achieve an increase in resolution and viewing angle while reducing the lateral chromatic aberration. More specifically, since the refractive lens 4-1 includes the intermediate portion 41-1 having a negative reduced portion curvature (h 11 ), it is possible to maintain the aberration balance, in particular, the astigmatism and the curvature of field.

[0129] The refractive lens 4-3 is also configured so that the reduced portion curvature of each portion varies (is not constant) according to the distance h from the optical axis OA. This will be described with reference to Figure 7 and Figure 8 .

[0130] Figure 7 is a diagram showing an example of a schematic configuration of the refractive lens 4-3. The refractive lens 4-3 is schematically shown as viewed from the front (viewed in the Z-axis direction). In this example, the refractive lens 4-3 has a circular shape with a center located on the optical axis OA. The radius of the refractive lens 4-3 is referred to as the radius D3.

[0131] The refractive lens 4-3 includes a central portion 40-3, an intermediate portion 41-3, and a peripheral portion 42-3. The central portion 40-3 is a portion including the center of the refractive lens 4-3. The peripheral portion 42-3 is a portion including the peripheral portion of the refractive lens 4-3. The intermediate portion 41-3 is a portion located between the central portion 40-3 and the peripheral portion 42-3. Using a distance h, the central portion 40-3 is a portion corresponding to a range of the distance h being relatively small (including h = 0). The peripheral portion 42-3 is a portion corresponding to a range of the distance h being relatively large (including h = D3). The intermediate portion 41-3 is a portion corresponding to a range of the distance h being between the two (not including h = 0 nor h = D3).

[0132] At least a portion of the light passing through the central portion 40-3 of the refractive lens 4-3 can be the same light as the light passing through the central portion 80 of the above-described diffractive lens 8. The same can apply to the intermediate portion 41-3 of the refractive lens 4-3 and the intermediate portion 81 of the diffractive lens 8, and the peripheral portion 42-3 of the refractive lens 4-3 and the peripheral portion 82 of the diffractive lens 8.

[0133] The refractive lens 4-3 is not constant in the refractive lens 4-3, and for example, continuously varies according to the distance h.

[0134] Figure 8 is a graph showing an example of the refractive lens 4-3. More specifically, the refractive lens 4-3 is illustrated on the surface of the pupil position P side. The distance h 30 is the distance h in any range within the range of the central portion 40-3 of the refractive lens 4-3. The distance h 31 is the distance h in any range within the range of the intermediate portion 41-3 of the refractive lens 4-3. The distance h 32 is the distance h in any range within the range of the peripheral portion 42-3 of the refractive lens 4-3.

[0135] The central portion 40-3 of the refractive lens 4-3 (at the distance h 30 ) can have a negative refractive portion curvature K. The intermediate portion 41-3 of the refractive lens 4-3 (at the distance h 31 ) can have a positive refractive portion curvature K. The peripheral portion 42-3 of the refractive lens 4-3 (at the distance h 32 ) can have a positive refractive portion curvature K. The following can be true.

[0136] K(h 30 ) < 0

[0137] K(h 31 ) > 0

[0138] κ(h 32 ) > 0

[0139] In the refractive lens 4-3, the reduced portion curvature K (at a distance h 31 from the optical axis OA) of the intermediate portion 41-3 is larger than the reduced portion curvature K (at a distance h 30 from the optical axis OA) of the central portion 40-3. The reduced portion curvature K (at a distance h 31 from the optical axis OA) of at least a portion of the intermediate portion 41-3 is larger than the reduced portion curvature K (at a distance h 32 from the optical axis OA) of the outer peripheral portion 42-3. It can also be said that there is a portion in the intermediate portion 41-3 that satisfies the following condition.

[0140] κ(h 31 ) > K(h 30 )

[0141] κ(h 31 ) > K(h 32 )

[0142] For example, by combining the use of the refractive lens 4-3 as described above and the above-described diffractive lens 8, it is possible to achieve an increase in resolution and viewing angle while reducing the lateral chromatic aberration. More specifically, on the surface on the pupil position P side of the refractive lens 4-3, the reduced portion curvature K (at a distance h 31 from the optical axis OA) of the intermediate portion 41-3 is larger than the reduced portion curvature K (at a distance h 30 from the optical axis OA) of the central portion 40-3. This can suppress total reflection of light even in a case where the panel size is relatively small with respect to the projection angle. In addition, the reduced portion curvature K (at a distance h 31 from the optical axis OA) of at least a portion of the intermediate portion 41-3 is larger than the reduced portion curvature K (at a distance h 32 from the optical axis OA) of the outer peripheral portion 42-3. This can prevent a deficiency in the thickness of the refractive lens 4-3 at the maximum image height portion.

[0143] Returning to Figure 1 , it is possible to determine whether the resolution and the viewing angle are increased by comparing the maximum object height in the optical system 3 with f all sin(θ / 2). The maximum object height corresponds to the distance from the optical axis OA to the outermost portion of the light incident portion in the display panel 2. Here, f all is the focal length of the entire optical system 3, and θ is the maximum half viewing angle. In one embodiment, the maximum object height can be f all sin(θ / 2) or less. That is, the optical system 3 can be designed so that the following holds.

[0144] Maximum object height ≤ f all sin(θ / 2)

[0145] With the optical system 3 designed as described above, a large viewing angle can be obtained with a small panel size. That is, an improvement in resolution and viewing angle can be achieved. As specific design examples, a first design example to a third design example will be described below.

[0146] <First design example>

[0147] Figures 9 to 16 are graphs, tables, and diagrams showing design examples. The size of one pixel of the display panel 2 is 6.3 μm.

[0148] Figure 9 An example of a modulation transfer function (MTF) of 80 lp / mm (corresponding to the MTF of one pixel) is shown. At this time, the pseudo-aperture diameter at the pupil position P is 8 mm. Here, the wavelength of light is 554 nm. Based on the size taking into account the eye rotation, the resolution per incidence, more specifically, the resolution per angle in the tangential direction (T) and the radial direction (R) is indicated. Specifically, the value at a position that is away from the optical axis OA by a distance obtained by the eye gap x tan (eye rotation angle) is indicated. The diffraction limit (diffraction limit) is also indicated. It can be seen that a sufficient resolution of about 40% is obtained in a range up to, for example, an eye rotation angle of 30°.

[0149] Figure 10 An example of the magnification chromatic aberration at the time of eye rotation is shown. The ordinate of the graph represents the angle (field angle) when viewing the optical system 3. The abscissa of the graph represents the distance (difference) between the position of light having a certain wavelength on the display panel 2 (for example, on the display surface 2a) and the position of light having a different wavelength. The graph line short-long indicates the difference between the position of light having a wavelength of 456 nm and the position of light having a wavelength of 658 nm on the display panel 2. The graph line short-Ref indicates the difference between the position of light having a wavelength of 456 nm and the position of light having a wavelength of 554 nm on the display panel 2. The magnification chromatic aberration is very small when the eye rotation angle is small, and is a good value of one pixel or less. When the angle is large, the magnification chromatic aberration increases, but the magnification chromatic aberration is suppressed to about 5 pixels in a range up to, for example, an eye rotation angle of 30°. Thus, the increased magnification chromatic aberration can be addressed by signal processing or the like. For example, the magnification chromatic aberration can be reduced to one pixel or less by signal processing. The axial aberration performance is also sufficiently ensured. It can be seen that a practical magnification chromatic aberration is obtained.

[0150] Figure 11 Examples of longitudinal aberration, astigmatism, and distortion are provided. The longitudinal aberration falls within ±0.1, and its variation is small. The astigmatism also falls within ±0.1. The distortion tends to the negative side, and varies monotonically (without an inflection point).

[0151] Figures 12 to 14 Examples of data of several optical surfaces are provided or shown. Figure 12 and Figure 13 Examples of data of optical surfaces s1 to s20 are provided. The specific positions of the optical surfaces are as shown in Figure 14 . Note that the optical surface s1 is an optical surface at the pupil position P (e.g., the pupil of the user U).

[0152] As provided in (A) of Figure 12 , the diagonal length of the display panel 2 (panel diagonal) in this example is 1.3 inches. The length of the panel in the lateral direction (e.g., the X-axis direction) (panel width) of the display panel 2 is 24.2 mm. This value is twice the maximum object height, and thus the maximum object height is 12.1 mm. The maximum object height corresponds to the distance from the optical axis OA to the outermost portion of the light incident portion in the display panel 2. The field of view in the lateral direction (lateral FoV θ) is 95°. This θ corresponds to the above-described maximum half viewing angle. The rotation angle is 70°. The eye relief is 15 mm. The focal length f all of the optical system 3 as a whole is 17.5 mm.

[0153] In (B) of Figure 12 , the surface type, the radius of curvature, the thickness, the refractive index, the Abbe number, the reflecting surface, and the aperture (half value) of each of the optical surfaces s1 to s20 are listed. Some of the above-described optical elements are also expressed in association. The surface type is any one of a spherical surface, an aspherical surface, and a diffractive surface. In the case of the aspherical surface type, the radius of curvature is the paraxial radius of curvature. The thickness used here indicates the distance from the optical surface in question to the subsequent optical surface. The thickness with a positive value corresponds to the length in the negative direction of the Z-axis, and the thickness with a negative value corresponds to the length in the positive direction of the Z-axis. The refractive index is the refractive index at the d line. The Abbe number vd number is the Abbe number obtained based on the difference between the C line and the F line with the d line as the reference. In the case of the reflecting surface, “reflection” is entered in the “reflecting surface” column. The aperture (half value) indicates the distance (radius) from the optical axis OA to the outermost portion of the portion through which light can pass.

[0154] Among the main optical elements, particularly with respect to the lenses, the surface of the refractive lens 4-1 on the pupil position P side corresponds to the optical surface s2. The diffractive lens 8 corresponds to the optical surface s15. The surfaces of the refractive lens 4-2 on the pupil position P side correspond to the optical surfaces s5, s8, and s13. The surfaces of the refractive lens 4-2 on the display panel 2 side correspond to the optical surfaces s7 and s14. The surface of the refractive lens 4-3 on the pupil position P side corresponds to the optical surface s18. The surface of the refractive lens 4-3 on the display panel 2 side corresponds to the optical surface s19.

[0155] In (C) of the above, Figure 13 f all sin(θ / 2) as an index of the improvement of the aforementioned resolution and viewing angle. In this example, f all sin(θ / 2) is 12.9 mm, and the maximum object height = 12.1 mm is f all sin(θ / 2) or less.

[0156] In (D) of the above, Figure 13 Additional data of the optical surface s15 is provided. The optical surface s15 corresponds to the polarization diffraction surface of the above-described diffractive lens 8, and gives a phase delay to the passing light. When the amount of phase delay is defined as φ, is represented by the following equation (1). Here, N is the diffraction order, and λ0is the normalized wavelength. Figure 13 The value of c n (n = 1 to 8) in equation (1) in (D) of the above is provided.

[0157]

[0158] Figure 13 Additional data of the optical surface whose surface type is aspherical is provided in (E) of the above. Specifically, coefficients defining the aspherical sag height of each of the optical surfaces s2, s5, s6, s18, and s19 are provided. The aspherical sag height is represented by the following equation (2). Here, R represents the radius of curvature, and h represents the height from the optical axis OA. Figure 13 The value of C n (n = 2 to 10) in equation (2) in (E) of the above is provided.

[0159]

[0160] As for the other aspherical optical surfaces, the aspherical sag height of the optical surfaces s7 and s14 can be the same or similar to that of the optical surface s6. The aspherical sag height of the optical surfaces s8 and s13 can be the same or similar to that of the optical surface s5.

[0161] In (F) of the above, Figure 13 The central resolving power is provided. The central resolving power = 50 pixels per degree (PPD) is obtained, which is a high resolving power.

[0162] Figure 15Some additional data of optical surfaces are provided. In response to incorporating the diffractive lens 8 in the optical system 3, parameters related to some of the optical surfaces as indicated are adjusted. The focal length f L1 is 111 mm. Here, y denotes a tracking amount of a chief ray in paraxial ray tracing, and y-bar denotes a tracking amount of an ambient ray. The reduced portion curvature K(0) on the axis is the reduced portion curvature K(distance h = 0) on the optical axis OA. The reduced portion curvature K on the diffractive surface is obtained by inverting the sign of the portion curvature obtained by reducing the phase retardation amount. The Abbe number vd is as described above. The refractive index N din is the refractive index on the light incident side (Z-axis negative direction side). The refractive index N dout is the refractive index on the light exit side (Z-axis positive direction side).

[0163] According to each of the above parameters, parameters related to the primary magnification chromatic aberration are calculated. Specifically, Figure 15 The calculated values of the primary magnification chromatic aberration proportion coefficient and the primary magnification chromatic aberration amount are provided. For the primary magnification chromatic aberration, the optical surface s2 (the surface of the refractive lens 4-1 on the pupil position P side) and the optical surface s15 (the diffractive lens 8) are dominant, and the optical surface s2 has the primary magnification chromatic aberration proportion coefficient and the primary magnification chromatic aberration amount with signs opposite to those of the optical surface s15, respectively, so as to cancel each other out. The reduced portion curvatures of the corresponding portions of the optical surfaces S2 and S15 can have the same sign.

[0164] The magnification chromatic aberration other than the primary magnification chromatic aberration is also related to the primary magnification chromatic aberration proportion coefficient to some extent.

[0165] Figure 16 The reduced portion curvatures K of some of the optical surfaces are indicated. At an arbitrary position in the intermediate image height band, the reduced portion curvature K of the optical surface s2 (the surface of the refractive lens 4-1) and the reduced portion curvature K of the optical surface s15 (the diffractive lens 8) have the same sign. For example, as described above, the reduced portion curvature K(h 11 ) of the intermediate portion 41-1 of the refractive lens 4-1 can be negative, and the reduced portion curvature K(h1) of the intermediate portion 81 of the diffractive lens 8 can also be negative. In the graph of Figure 16 , in the case of, for example, distance h = 14 mm, both of the reduced portion curvatures K are negative.

[0166] The negative reduced portion curvature K of the optical surface s2 reduces the image surface curvature and the image spread. The optical surface s18 (surface of the refractive lens 4-3 on the side of the pupil position P) has a larger positive value as the distance h increases (as the distance h approaches the outer portion). The optical surface s18 having a large positive value bends the light rays toward the center. When the distance h further increases (approaches the edge), the reduced portion curvature K decreases, but this is due to the limitation of the sag height and the tilt angle.

[0167] <Second design example>

[0168] In the second design example, the surface of the refractive lens 4-1 on the side of the display panel 2 (more specifically, the polarizer 6-1 and the QWP 7-1) is aspherical.

[0169] Figure 17 is a set of diagrams showing an example of a schematic configuration of the display device 1. In Figure 17 (A) of FIG. 1, an example of a schematic configuration of the display device 1 is shown. In Figure 17 (B) of FIG. 1, several light paths are schematically shown. In particular, the shapes of the polarizer 6-1 and the QWP 7-1 are different from those in the above-described Figure 1

[0170] Figures 18 to 25 is a set of graphs, tables, and diagrams showing design examples. Conditions not specifically described can be the same as those in the above-described first design example, and similarly apply to other design examples described later. Figure 18 Examples of the MTF are provided. Figure 19 Examples of the magnification chromatic aberration at the time of eyeball rotation are provided. Figure 20 Examples of the longitudinal aberration, the image spread, and the distortion are provided. Similarly to the first design example, it can be seen that a sufficient resolving power of about 40% is obtained in a range up to, for example, an eyeball rotation angle of 30°. The magnification chromatic aberration is also suppressed to about 5 pixels.

[0171] Figure 21 and Figure 22 Examples of data of the optical surfaces s1 to s20 are provided. The specific positions of the optical surfaces are as shown in Figure 23 . The design values are appropriately changed in accordance with the aspheric polarizer 6-1 and the QWP 7-1. As provided in Figure 22 (C), f all sin(θ / 2) is 12.8 mm, and the maximum object height = 12.1 mm understood from Figure 21 (A) is f all sin(θ / 2) or less. As a result, an improvement in the resolution and the viewing angle is achieved. As provided in Figure 22 (F), a center resolution = 49 PPD, which is a high resolving power, is obtained.​

[0172] As Figure 24 shown in (A) of FIG. 12, the optical surfaces s2, s3, and s4 (surfaces of the refractive lens 4-1) and the optical surface s15 (the diffractive lens 8) dominate, and the optical surfaces s2, s3, and s4 and the optical surface s15 each have a primary magnification chromaticity proportion coefficient and a primary magnification chromaticity amount so as to cancel each other out.

[0173] In Figure 25 (A) of FIG. 13, the reduced partial curvature κ of some of the optical surfaces is indicated. In Figure 25 (B) of FIG. 13, a graph with an enlarged horizontal axis is provided. The difference (s2-s3) between the reduced partial curvature κ of the optical surface s2 and the reduced partial curvature κ of the optical surface s3 is also indicated. The difference (s2-s3) and the reduced partial curvature κ of the optical surface s15 have the same sign at any position in the intermediate image height band. For example, as described above, the reduced partial curvature κ (h 11 ) of the intermediate portion 41-1 of the refractive lens 4-1 can be negative, and the reduced partial curvature κ (h1) of the intermediate portion 81 of the diffractive lens 8 can also be negative. The reduced partial curvature κ (h 11 ) used here can be the sum of the reduced partial curvature κ of the surface of the refractive lens 4-1 on the side of the pupil position P and the reduced partial curvature κ of the surface of the refractive lens 4-1 on the side of the display panel 2 (for example, the surface including the polarizer 6-1). In Figure 25 the graph of (A) of FIG. 13, both of these reduced partial curvatures κ are negative in the case of, for example, a distance h = 15 mm. The negative difference (s2-s3) reduces the image surface curvature and the astigmatism.

[0174] <Third Design Example>

[0175] In the third design example, the panel size is 1.88 inches, which is larger than the above-mentioned 1.3 inches.

[0176] Figure 26 is a set of graphs showing an example of a schematic configuration of the display device 1. In Figure 26 (A) of FIG. 14, an example of a schematic configuration of the display device 1 is shown. In Figure 26 (B) of FIG. 14, several light paths are schematically shown.

[0177] Figures 27 to 34 is a graph, a table, and a graph showing a design example. Figure 27 An example of the MTF is provided. Figure 28 An example of the magnification chromaticity when the eyeball rotates is provided. Figure 29Examples of longitudinal aberration, astigmatism, and distortion are provided. It can be seen that approximately 35% resolution is achieved up to, for example, an eye rotation angle of 35°. Magnification chromatic aberration is also suppressed to approximately 5 pixels.

[0178] Figure 30 and Figure 31 Examples of data for optical surfaces s1 to s20 are provided. The specific locations of the optical surfaces are as follows: Figure 32 As shown in the diagram. The field of view (lateral FoV θ) is 110°. The design values ​​are adjusted appropriately in response to changes in panel size. Figure 31 The f provided in (C) all The value of sin (θ / 2) is 17.9 mm, and from Figure 30 The maximum height of the object understood in (A) is 16.7 mm, which is f. all The value of sin(θ / 2) is either smaller. As a result, improvements in resolution and viewing angle are achieved. For example... Figure 31 As provided in (F), a center resolution of 62 PPD was obtained, which is high resolution.

[0179] like Figure 33 The optical surfaces s2, s3 and s4 (the surfaces of the refractive lens 4-1) and s15 (the diffractive lens 8) provided herein are dominant, and each of the optical surfaces s2, s3 and s4 and s15 has a primary magnification chromatic aberration ratio coefficient and a primary magnification chromatic aberration amount, so as to cancel each other out.

[0180] exist Figure 34 In (A), the equivalent curvature κ of some optical surfaces is indicated. Figure 34 In (B), a graph with an enlarged horizontal axis is provided. Since the trend of this graph is similar to that of the second design example, its description will be omitted.

[0181] For example, in the first to third design examples as described above, in the configuration where the optical system 3 incorporates the diffraction lens 8, improvements in resolution and viewing angle can be achieved.

[0182] 2. Modify the example

[0183] As a modification example, the diffractive lens 8 can be positioned between the refracting lens 4-1 and the refracting lens 4-2. In such a modification example, improvements in resolution and viewing angle can also be achieved. This will refer to... Figures 35 to 44 Describe it.

[0184] Figure 35 This is a set of diagrams illustrating an example of a schematic configuration of display device 1. Figure 35 In (A), an example of a schematic configuration of display device 1 is shown.Figure 35 In (B), several light paths are schematically shown. In this example, the diffractive lens 8 is located between the refractive lens 4-1 and the refractive lens 4-2. The refractive lens 4-2 has a positive optical power as described above. Further, the QWP 7-1 is a pair of QWPs, which are referred to in the figure as QWP 7-1a and QWP 7-1b and are illustrated as QWP 7-1a and QWP 7-1b. When they are not particularly distinguished from each other, they are simply referred to as QWP 7-1.

[0185] In the optical system 3, the refractive lens 4-3, the polarizer 6-2, the QWP 7-2, the semi-transparent mirror 5, the refractive lens 4-1, the QWP 7-1a, the polarizer 6-1, the QWP 7-1b, the diffractive lens 8, and the refractive lens 4-1 are arranged in this order in the positive direction of the Z axis.

[0186] Figure 36 is a figure showing an example of a schematic configuration of the optical system 3. In this example, the QWP 7-2 converts the Y-polarized light from the polarizer 6-2 into clockwise circularly polarized light. A part of the clockwise circularly polarized light passes through the semi-transparent mirror 5, further passes through the refractive lens 4-1, and enters the QWP 7-1a.

[0187] The QWP 7-1a converts the clockwise circularly polarized light that has passed through the refractive lens 4-1 into Y-polarized light. In this example, the polarizer 6-1 passes the X-polarized light and reflects the Y-polarized light. Thus, the Y-polarized light from the QWP 7-1a is reflected by the polarizer 6-1 and enters the QWP 7-1a again. The QWP 7-1a converts the Y-polarized light from the polarizer 6-1 into clockwise circularly polarized light. This clockwise circularly polarized light passes through the refractive lens 4-1, and a part of it is reflected by the semi-transparent mirror 5. This reflected light becomes counterclockwise circularly polarized light, passes through the refractive lens 4-1, and enters the QWP 7-1a. The QWP 7-1a converts the counterclockwise circularly polarized light that has passed through the refractive lens 4-1 into X-polarized light. The X-polarized light passes through the polarizer 6-1 and enters the QWP 7-1b.

[0188] The QWP 7-1b converts the X-polarized light from the polarizer 6-1 into clockwise circularly polarized light. The clockwise circularly polarized light enters the diffractive lens 8.

[0189] The clockwise circularly polarized light from the QWP 7-1b enters the diffractive lens 8. Thus, the circularly polarized light from the diffractive lens 8 is counterclockwise circularly polarized light. The counterclockwise circularly polarized light enters the refractive lens 4-1 Figure 35 ). The light from the refractive lens 4-1 is substantially parallel light at the pupil position P, and the user U observes an image.

[0190] <Fourth design example>

[0191] The fourth design example is a design example based on the configuration of the above-described modification example. The panel size is 1.3 inches.

[0192] Figures 37 to 44 are graphs, tables, and diagrams showing design examples. Figure 37 Examples of MTF are provided. Figure 38 Examples of chromatic aberration of magnification at the time of eyeball rotation are provided. Figure 39 Examples of longitudinal aberration, astigmatism, and distortion are provided. It can be seen that sufficient resolution of about 40% is obtained in a range up to, for example, an eyeball rotation angle of 30°. The chromatic aberration of magnification is also suppressed to about 5 pixels.

[0193] Figure 40 and Figure 41 Examples of data of optical surfaces s1 to s20 are provided. The specific positions of the optical surfaces are as shown in Figure 42 The field of view in the lateral direction (lateral FoV θ) is 95°. The design values are appropriately changed in response to a change in the panel size. As provided in Figure 41 (C), f all The value of sin(θ / 2) is 13 mm, and the maximum object height = 12.1 mm understood from Figure 40 (A) is the value of f all sin(θ / 2) or less. As a result, improvement in resolution and viewing angle is achieved. As provided in Figure 41 (F), a center resolution = 49 PPD, which is a high resolution, is obtained.

[0194] Among the main optical elements, particularly with respect to the lenses, the surface of the refractive lens 4-1 on the pupil position P side corresponds to the optical surface s2. The diffractive lens 8 corresponds to the optical surface s3. The surface of the refractive lens 4-2 on the pupil position P side corresponds to the optical surfaces s5, s8, and s13. The surface of the refractive lens 4-2 on the display panel 2 side corresponds to the optical surfaces s7 and s14. The surface of the refractive lens 4-3 on the pupil position P side corresponds to the optical surface s18. The surface of the refractive lens 4-3 on the display panel 2 side corresponds to the optical surface s19.

[0195] As provided in Figure 43 , the optical surfaces s2, s3, and s4 (surfaces of the refractive lens 4-1) and the optical surface s3 (diffractive lens 8) are dominant, and the optical surfaces s2, s3, and s4 and the optical surface s3 each have a primary chromatic aberration of magnification proportion coefficient and a primary chromatic aberration of magnification amount so as to cancel each other out.

[0196] In (A) of Figure 44 , the converted partial curvature κ of some of the optical surfaces is indicated. In Figure 44In (B), a graph having an enlarged horizontal axis is provided. The trend of this graph is the same as or similar to the trend of the above-described second design example. As an example, in the case of a distance h = 14 mm, the reduced partial curvature K of the optical surface s3 and the difference (s2-s3) between the reduced partial curvature K of the optical surface s2 and the reduced partial curvature K of the optical surface s3 have the same sign, and they are both negative.

[0197] 3. Summary

[0198] For example, the above-described techniques are explained as follows. One of the disclosed techniques is an optical system 3. As described with reference to Figures 1 to 4 , Figure 16 , Figure 17 , Figure 25 , Figure 26 , Figures 34 to 36 , Figure 44 and the like, the optical system 3 images light from the display panel 2 on the retina when combined with the eyeball. The optical system 3 includes a refractive lens 4-1 (first refractive lens), a refractive lens 4-2 (second refractive lens) located between the refractive lens 4-1 and the display panel 2, a refractive lens 4-3 (third refractive lens) located between the refractive lens 4-2 and the display panel 2, and a diffractive lens 8 located between the refractive lens 4-1 and the refractive lens 4-2 or between the refractive lens 4-2 and the refractive lens 4-3. The optical system 3 is configured so that light from the display panel 2 passes through the refractive lens 4-2 three times by making the optical path turn back. The diffractive lens 8 is configured so that the reduced partial curvature K of each portion varies depending on the distance h from the optical axis OA.

[0199] According to the above-described optical system 3, since not only the refractive lens 4 but also the diffractive lens 8 is included, the lens function can be improved accordingly, and an improvement in resolution and viewing angle can be achieved. In addition, since the reduced partial curvature K of each portion of the diffractive lens 8 varies depending on the distance h from the optical axis OA (is not constant), a magnification chromatic aberration can be suppressed. Thus, an improvement in resolution and viewing angle can be achieved while suppressing a magnification chromatic aberration.

[0200] As described with reference to Figure 3 , Figure 4 , Figure 16 , Figure 25 , Figure 34 , Figure 44 and the like, the diffractive lens 8 can include a central portion 80 having a positive reduced partial curvature K(h0) and an intermediate portion 81 located between the central portion 80 and the outer peripheral portion 82 and having a negative reduced partial curvature K(h1). For example, by using the diffractive lens 8 as described above, a magnification chromatic aberration can be suppressed.

[0201] As described with reference toFigure 3 , Figure 4 , Figure 16 , Figure 25 , Figure 34 , Figure 44 and the like, the outer peripheral portion 82 of the diffractive lens 8 can have a positive reduced portion curvature K(h2). This makes it possible to reduce the astigmatism and the curvature of field in relation to the refractive lens 4-3, for example.

[0202] As described with reference to Figure 1 and the like, the refractive lens 4-1 can have an Abbe number of 30 or less. The refractive lens 4-2 can have an Abbe number of 30 or more, and the refractive lens 4-3 can have an Abbe number of 30 or less. With this configuration, it is possible to suppress the chromatic aberration of magnification in the region including the optical axis OA while maintaining the color balance.

[0203] As described with reference to Figure 1 and the like, the refractive lens 4-1 can have a positive focal length. This makes it possible to maintain the balance of chromatic aberration, particularly the balance of the optical power of the entire optical system.

[0204] As described with reference to Figure 5 , Figure 6 , Figure 16 , Figure 25 , Figure 34 , Figure 44 and the like, the refractive lens 4-1 can include an intermediate portion 41-1 located between the central portion 40-1 and the outer peripheral portion 42-1 and having a negative reduced portion curvature K(h 11 ). For example, by combining the use of the refractive lens 4-1 as described above and the diffractive lens 8 described above, it is possible to achieve an increase in resolution and an increase in angle of view while reducing the chromatic aberration of magnification.

[0205] As described with reference to Figure 7 , Figure 8 , Figure 16 , Figure 25 , Figure 34 , Figure 44 and the like, the refractive lens 4-3 can include an intermediate portion 41-3 located between the central portion 40-3 and the outer peripheral portion 42-3 and having a reduced portion curvature K(h 30 ) on the surface on the eyeball side (pupil position P side, Z-axis positive direction side) that is larger than the reduced portion curvature K(h 31 ) of the central portion 40-3. For example, by combining the use of the refractive lens 4-3 as described above and the diffractive lens 8 described above, it is possible to achieve an increase in resolution and an increase in angle of view while reducing the chromatic aberration of magnification. Also, in the case where the panel size is relatively small with respect to the projection angle, it is possible to suppress total reflection of light.

[0206] As described with reference to Figure 7 ,Figure 8 、 Figure 16 、 Figure 25 、 Figure 34 、 Figure 44 At least a portion of the intermediate portion 41-3 of the refractive lens 4-3 can have a larger reduced portion curvature K(h 32 ) on the surface on the eyeball side than the reduced portion curvature K(h 31 ) of the peripheral portion 42-3 of the refractive lens 4-3. This makes it possible to prevent a deficiency in the thickness of the refractive lens 4-3 at the maximum image height portion.

[0207] As described with reference to Figure 1 、 Figure 12 、 Figure 13 、 Figure 21 、 Figure 22 、 Figure 30 、 Figure 31 、 Figure 40 、 Figure 41 The optical system 3 can be designed so that the maximum object height ≤ the focal length of the entire optical system × sin (the maximum half viewing angle) is satisfied. As a result, a large viewing angle can be obtained with a small panel size.

[0208] As described with reference to Figure 1 and Figure 2 The refractive lens 4-2 can have a positive refractive power, and the diffractive lens 8 can be located between the refractive lens 4-2 and the refractive lens 4-3. For example, by arranging the diffractive lens 8 in this way, it is possible to achieve an improvement in resolution and viewing angle while reducing the magnification chromatic aberration.

[0209] As described with reference to Figure 35 and Figure 36 The refractive lens 4-2 can have a positive refractive power, and the diffractive lens 8 can be located between the refractive lens 4-1 and the refractive lens 4-2. Also in this case, it is possible to achieve an improvement in resolution and viewing angle while suppressing the magnification chromatic aberration.

[0210] As described with reference to Figure 2 The diffractive lens 8 can be a polarization diffractive lens. This configuration makes it easy to handle oblique incidence and wavelength variation. It also has the advantage that light can be effectively guided, and that a spot and ghosting can be easily cut.

[0211] As described with reference to Figure 1 The thickness of the diffractive lens 8 can be smaller than the thickness of the refractive lens 4. This configuration can contribute to the thinness and smallness of the optical system 3.

[0212] With reference to Figures 1 to 4 、 Figure 16 、 Figure 17 、 Figure 25 、 Figure 26、 Figures 34 to 36 、 Figure 44 The display device 1 described above is also one of the disclosed technology. The display device 1 includes a display panel 2 and an optical system 3 that, when combined with an eyeball, serves to image light from the display panel 2 on a retina. Details of the optical system 3 are as described above. The display device 1 can be a head-mounted display device. Also, with the display device 1 as described above, as described above, it is possible to achieve an increase in resolution and viewing angle while suppressing chromatic aberration of magnification.

[0213] The effects described in this disclosure are merely illustrative and not limited to the disclosed effects. Other effects can be provided.

[0214] Note that the present technology can also have the following configurations.

[0215] (1) An optical system that, when combined with an eyeball, serves to image light from a display panel on a retina, the optical system including:

[0216] a first refractive lens;

[0217] a second refractive lens located between the first refractive lens and the display panel;

[0218] a third refractive lens located between the second refractive lens and the display panel; and

[0219] a diffractive lens located between the first refractive lens and the second refractive lens or between the second refractive lens and the third refractive lens, wherein

[0220] in the optical system, light from the display panel passes through the second refractive lens three times by making the optical path turn back, and

[0221] a conversion partial curvature of each portion of the diffractive lens varies depending on a distance from an optical axis.

[0222] (2) The optical system according to (1), wherein

[0223] the diffractive lens includes:

[0224] a central portion having a positive conversion partial curvature, and

[0225] an intermediate portion located between the central portion and an outer peripheral portion and having a negative conversion partial curvature.

[0226] (3) The optical system according to (2), wherein

[0227] the outer peripheral portion of the diffractive lens has a positive conversion partial curvature.

[0228] (4) The optical system according to (2) or (3), wherein

[0229] The first refractive lens has an Abbe number of 30 or less.

[0230] (5) The optical system according to (4), wherein

[0231] The second refractive lens has an Abbe number of 30 or more, and

[0232] The third refractive lens has an Abbe number of 30 or less.

[0233] (6) The optical system according to any one of (2) to (5), wherein

[0234] The first refractive lens has a positive focal length.

[0235] (7) The optical system according to (6), wherein

[0236] The first refractive lens includes an intermediate portion between the central portion and the peripheral portion and having a negative reduced portion curvature.

[0237] (8) The optical system according to (6) or (7), wherein

[0238] The third refractive lens includes an intermediate portion between the central portion and the peripheral portion and having a reduced portion curvature larger than that of the central portion on the eyeball-side surface.

[0239] (9) The optical system according to (8), wherein

[0240] At least a portion of the intermediate portion of the third refractive lens has a reduced portion curvature larger than that of the peripheral portion of the third refractive lens on the eyeball-side surface.

[0241] (10) The optical system according to any one of (2) to (9), wherein

[0242] The optical system is designed to have a maximum object height < focal length of the optical system as a whole x sin (maximum half viewing angle).

[0243] (11) The optical system according to any one of (2) to (10), wherein

[0244] The second refractive lens has a positive refractive power, and

[0245] The diffractive lens is located between the second refractive lens and the third refractive lens.

[0246] (12) The optical system according to any one of (2) to (10), in which

[0247] The second refractive lens has a positive power, and

[0248] The diffractive lens is located between the first refractive lens and the second refractive lens.

[0249] (13) The optical system according to any one of (2) to (12), in which

[0250] The diffractive lens is a polarization diffractive lens.

[0251] (14) The optical system according to any one of (1) to (13), in which

[0252] The thickness of the diffractive lens is smaller than the thickness of a refractive lens.

[0253] (15) A display device comprising:

[0254] a display panel; and

[0255] an optical system that, when combined with an eyeball, images light from the display panel on a retina, in which

[0256] The optical system includes:

[0257] a first refractive lens,

[0258] a second refractive lens located between the first refractive lens and the display panel,

[0259] a third refractive lens located between the second refractive lens and the display panel, and

[0260] a diffractive lens located between the first refractive lens and the second refractive lens, or between the second refractive lens and the third refractive lens,

[0261] in the optical system, light from the display panel passes through the second refractive lens three times by making a light path turn back, and

[0262] a conversion partial curvature of each portion of the diffractive lens varies according to a distance from an optical axis.

[0263] (16) The display device according to (15), in which

[0264] The display device is a head-mounted display device.

[0265] List of Reference Signs

[0266] 1 display device

[0267] 2 display panel

[0268] 2a display surface

[0269] 3 optical system

[0270] 4 refractive lens

[0271] 4-1 refractive lens (first refractive lens)

[0272] 40-1 central portion

[0273] 41-1 intermediate portion

[0274] 42-1 peripheral portion

[0275] 4-2 refractive lens (second refractive lens)

[0276] 4-3 refractive lens (third refractive lens)

[0277] 40-3 central portion

[0278] 41-3 intermediate portion

[0279] 42-3 peripheral portion

[0280] 5 semi-transparent mirror

[0281] 6 polarizer

[0282] 6-1 polarizer

[0283] 6-2 polarizer

[0284] 7 QWP

[0285] 7-1 QWP

[0286] 7-1a QWP

[0287] 7-1b QWP

[0288] 7-2 QWP

[0289] 8 diffraction lens

[0290] 80 central portion

[0291] 81 intermediate portion

[0292] 82 peripheral portion

[0293] OA optical axis

[0294] P pupil position

[0295] U user

Claims

1. An optical system that images light from a display panel on a retina when combined with an eyeball, the optical system comprising: a first refractive lens; a second refractive lens between the first refractive lens and the display panel; a third refractive lens between the second refractive lens and the display panel; and a diffractive lens between the first refractive lens and the second refractive lens, or between the second refractive lens and the third refractive lens, wherein in the optical system, light from the display panel passes through the second refractive lens three times by making a light path turn back, and a reduced partial curvature of each portion of the diffractive lens varies according to a distance from an optical axis.

2. The optical system according to claim 1, wherein the diffractive lens includes: a central portion having a positive reduced partial curvature, and an intermediate portion between the central portion and an outer peripheral portion, and having a negative reduced partial curvature.

3. The optical system according to claim 2, wherein the outer peripheral portion of the diffractive lens has a positive reduced partial curvature.

4. The optical system according to claim 2, wherein the first refractive lens has an Abbe number of 30 or less.

5. The optical system according to claim 4, wherein the second refractive lens has an Abbe number of 30 or more, and the third refractive lens has an Abbe number of 30 or less.

6. The optical system according to claim 2, wherein the first refractive lens has a positive focal length.

7. The optical system according to claim 6, wherein the first refractive lens includes an intermediate portion between a central portion and an outer peripheral portion, and having a negative reduced partial curvature.

8. The optical system according to claim 6, wherein the third refractive lens includes an intermediate portion between a central portion and an outer peripheral portion, and having a reduced partial curvature on an eyeball-side surface that is larger than a reduced partial curvature of the central portion.

9. The optical system according to claim 8, wherein at least a portion of the intermediate portion of the third refractive lens has a reduced partial curvature on the eyeball-side surface that is larger than a reduced partial curvature of the outer peripheral portion of the third refractive lens.

10. The optical system according to claim 2, wherein the optical system is designed to have a maximum object height < a focal length of the optical system as a whole x sin (a maximum half viewing angle).

11. The optical system according to claim 2, wherein the second refractive lens has a positive optical power, and the diffractive lens is between the second refractive lens and the third refractive lens.

12. The optical system according to claim 2, wherein the second refractive lens has a positive optical power, and the diffractive lens is between the first refractive lens and the second refractive lens.

13. The optical system according to claim 2, wherein the diffractive lens is a polarization diffractive lens.

14. The optical system according to claim 1, wherein ​ The thickness of the diffractive lens is smaller than the thickness of the refractive lens.

15. A display device comprising: a display panel; and an optical system that, when combined with an eyeball, images light from the display panel on a retina, wherein the optical system comprises: a first refractive lens, a second refractive lens between the first refractive lens and the display panel, a third refractive lens between the second refractive lens and the display panel, and a diffractive lens between the first refractive lens and the second refractive lens, or between the second refractive lens and the third refractive lens, in the optical system, light from the display panel passes through the second refractive lens three times by folding the optical path, and a scaled partial curvature of each portion of the diffractive lens varies according to a distance from an optical axis.

16. The display device according to claim 15, wherein the display device is a head-mounted display device.

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