Optical system and display device

Abstract

An optical system according to the present invention, which turns light from a display panel into substantially collimated light at a pupil position of a user, forming an image at a retina position when combined with an eyeball, is provided with: a refractive lens; a first reflective face located between the pupil position and the refractive lens; and a second reflective face located between the refractive lens and the display panel, and is configured such that the light from the display panel passes through the refractive lens three times while going back and forth on an optical path. A peripheral section of the first reflective face has a positive partial curvature. A central section of the second reflective face has a negative partial curvature. The positive partial curvature is arranged to have a curvature center thereof on the display panel side. The negative partial curvature is arranged to have a curvature center thereof on the pupil position side.

Description

Optical system and display device

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

[0002] It is known that display devices such as head mounted displays (HMDs) use a so-called triple-path optical system in which light from a display panel is configured to fold its optical path and pass through the same refractive lens three times (see, for example, Patent Document 1).

[0003] International Publication No. 2023 / 153266

[0004] There is still room for further study on widening the angle of view of optical systems and display devices.

[0005] One aspect of the present disclosure enables a wider angle of view.

[0006] An optical system according to one aspect of the present disclosure is an optical system that converts light from a display panel into approximately parallel light at a user's pupil position and forms an image at the retina position when combined with the eyeball, the optical system comprising: a refractive lens; a first reflecting surface located between the pupil position and the refractive lens; and a second reflecting surface located between the refractive lens and the display panel, wherein light from the display panel is configured to turn its optical path and pass through the refractive lens three times, the peripheral portion of the first reflecting surface having a positive partial curvature and the central portion of the second reflecting surface having a negative partial curvature, the positive partial curvature being configured such that the center of curvature of the partial curvature is on the display panel side, and the negative partial curvature being configured such that the center of curvature of the partial curvature is on the pupil position side.

[0007] A display device according to one aspect of the present disclosure includes a display panel and an optical system that converts light from the display panel into approximately parallel light at a user's pupil position and forms an image at the retina when combined with the eyeball, the optical system including a refractive lens, a first reflective surface located between the pupil position and the refractive lens, and a second reflective surface located between the refractive lens and the display panel, and is configured so that light from the display panel folds its optical path and passes through the refractive lens three times, the peripheral portion of the first reflective surface has a positive partial curvature and the central portion of the second reflective surface has a negative partial curvature, the positive partial curvature is configured so that the center of curvature of the partial curvature is on the display panel side, and the negative partial curvature is configured so that the center of curvature of the partial curvature is on the pupil position side.

[0008] 1 is a diagram showing an example of a schematic configuration of a display device 1 according to a first embodiment; FIG. 1 is a diagram showing an example of a schematic configuration of an optical system 3; FIG. 1 is a diagram showing an example of an optical surface s3; FIG. 1 is a diagram showing an example of an optical surface s3; FIG. 1 is a diagram showing an example of an optical surface s5; FIG. 1 is a diagram showing an example of an optical surface s5; FIG. 1 is a diagram showing an example of an optical surface s6; FIG. 1 is a diagram showing an example of an optical surface s6; FIG. 1 is a diagram showing an example of an optical surface s18; FIG. 1 is a diagram showing an example of an optical surface s18; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 1 is a diagram showing a design example of the first embodiment; FIG. 10 is a diagram showing a design example of the fourth embodiment. FIG. 11 is a diagram showing a design example of the fourth embodiment. FIG. 12 is a diagram showing a design example of the fourth embodiment. FIG. 13 is a diagram showing an example of a schematic configuration of a display device 1 according to a fifth embodiment. FIG. 14 is a diagram showing a design example of the fifth embodiment. FIG. 15 is a diagram showing a design example of the fifth embodiment. FIG. 16 is a diagram showing a design example of the fifth embodiment. FIG. 17 is a diagram showing a design example of the fifth embodiment. FIG. 18 is a diagram showing a design example of the fifth embodiment. FIG. 19 is a diagram showing a design example of the sixth embodiment. FIG. 19 is a diagram showing a design example of the sixth embodiment. FIG. 19 is a diagram showing a design example of the sixth embodiment. FIG. 19 is a diagram showing a design example of the sixth embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each of the following embodiments, the same elements may be designated by the same reference numerals, and duplicated explanations may be omitted. Duplicate reference numerals may be used in different embodiments to have different meanings, and in such cases, they may be interpreted according to the explanation in the embodiment.

[0010] The present disclosure will be described in the following itemized order: 0. Introduction 1. First Embodiment 2. Second Embodiment 3. Third Embodiment 4. Fourth Embodiment 5. Fifth Embodiment 6. Sixth Embodiment 7. Conclusion

[0011] 0. Introduction Display devices such as HMDs include an optical system that, when combined with the user's pupil position, more specifically, the position on the retina of the eyeball, focuses light from a display panel onto the retina to display an image. For example, a triple-path optical system, such as that disclosed in Patent Document 1, is known. Achieving a wide angle of view requires significantly bending peripheral light flux, but achieving both physical constraints and aberration balance is not easy. For example, optical systems often already include many lenses, which poses physical constraints such as difficulty in ensuring edge thickness. Furthermore, flat reflective surfaces reduce aberration correction capabilities near the maximum image height. Issues remain, such as further widening the angle of view and downsizing the display panel.

[0012] The disclosed technology addresses at least some of the above-mentioned problems. As will be described in detail later, a wider angle of view is achieved by providing distinctive partial curvatures for the reflective surfaces that make up the triple-path optical system. For example, the reflective surface located on the pupil position side (pupil-side reflective surface) has a positive sag (positive sag) from the optical axis to an intermediate image height, facilitating aberration correction by other lenses. Near the maximum image height, the pupil-side reflective surface has a negative sag (negative sag), providing a strong positive power (light-gathering effect), facilitating an improvement in the viewing angle and a reduction in the size of the display panel. In one embodiment, a diffractive lens is also incorporated, further increasing the possibility of sufficiently reducing chromatic aberration.

[0013] 1. First Embodiment FIG. 1 is a diagram illustrating an example of the schematic configuration of a display device 1 according to a first embodiment. The display device 1 is, for example, an HMD device (which can also be called a virtual image observation device) that displays images for VR (Virtual Reality). FIG. 1A schematically illustrates the eye (eyeball) of a user U1 who wears and uses the display device 1. A position on the pupil of the eye is indicated by a symbol as pupil position P1. The pupil position P1 of the user U1 is located at or near a position where light from one point on the display device 1 becomes substantially parallel light, and an image is observed by the user U1. Note that the term "image" may also be interpreted as an image, and these terms may be interpreted interchangeably as appropriate.

[0014] An XYZ coordinate system is also shown. The display device 1 and user U1 are located in this order in the positive direction of the Z axis. Unless otherwise specified, each element of the display device 1 extends in the X-axis direction and the Y-axis direction (XY plane direction) and has a thickness in the Z-axis direction. (A) of FIG. 1 schematically shows a side view (which may be a cross section) of the display device 1 as viewed in the X-axis direction. (B) of FIG. 1 schematically shows the paths of several lights (which may also be called light rays, light beams, etc.).

[0015] The display device 1 includes a display panel 2 and an optical system 3. The display panel 2 and the optical system 3 are positioned (arranged) in this order in the positive direction of the Z axis. Note that Fig. 1A also shows an optical axis OA1 of the optical system 3.

[0016] The display panel 2 includes, for example, an OLED (Organic Light Emitting Diode), an LC (Liquid Crystal), an LED (Light Emitting Diode), etc. The display surface of the display panel 2 is illustrated as a display surface 2a.

[0017] When combined with the eye of a user U1, the optical system 3 converts light from the display panel 2 into substantially parallel light at the pupil position P1 of the eye, and forms an image on the retina of the eye. In the example shown in Fig. 1, the optical system 3 includes a refractive lens 4, a half mirror 5, a polarizer 6 (e.g., a polarizing plate), a QWP (quarter-wave plate) 7, and a diffractive lens 8. Note that the term "plate" may be interpreted to include a film.

[0018] At least some optical elements may be present in multiples: in this example, there are multiple refractive lenses 4, multiple polarizers 6, and multiple QWPs 7.

[0019] 1 illustrates three refractive lenses 4 as examples of the plurality of refractive lenses 4. The first refractive lens is referred to as a refractive lens 4-1 and is illustrated. The second refractive lens is referred to as a refractive lens 4-2 and is illustrated. The third refractive lens is referred to as a refractive lens 4-3 and is illustrated. When there is no particular need to distinguish between these lenses, they are simply referred to as refractive lenses 4.

[0020] 1 illustrates two polarizers 6 as examples of the multiple polarizers 6. The first polarizer is illustrated as 6-1. The second polarizer is illustrated as polarizer 6-2. When there is no need to distinguish between them, they are simply referred to as polarizers 6.

[0021] 1 illustrates three QWPs 7 as examples of multiple QWPs 7. The first QWP is referred to as QWP7-1 and is illustrated. The second QWP is referred to as QWP7-2 and is illustrated. The third QWP is referred to as QWP7-3 and is illustrated. When there is no need to distinguish between them, they are simply referred to as QWP7.

[0022] In this example, the refractive lens 4-3, diffractive lens 8, QWP 7-3, polarizer 6-2, QWP 7-2, half mirror 5, refractive lens 4-2, QWP 7-1, polarizer 6-1, and refractive lens 4-1 are arranged in this order in the positive direction of the Z axis. There are no particular limitations on the method for producing each optical element, and various known methods may be used. The refractive lens 4-1 may be produced using UV casting.

[0023] In the example shown in FIG. 1, the QWP 7-1 and the polarizer 6-1 are films provided on the surface of the refractive lens 4-1 facing the display panel 2 (negative Z-axis direction).

[0024] Light from the display panel 2 passes through the optical system 3 and becomes substantially parallel light at pupil position P1. In the following description, light traveling in the positive direction of the Z axis through the optical system 3 may also be simply referred to as light from the display panel 2.

[0025] The behavior of light from the display panel 2 can also be explained by tracking it in the reverse direction. In this case, it can be said that light from pupil position P1 passes through the optical system 3 and is collected on the display surface 2 a of the display panel 2.

[0026] Of the optical elements included in the optical system 3, the polarizer 6-2, QWP 7-2, half mirror 5, refractive lens 4-2, QWP 7-1, and polarizer 6-1 in particular constitute a so-called triple-pass optical system. The triple-pass configuration can be useful for making the optical system 3 thinner and more compact. As will be described in detail later, the optical system 3 is configured so that light from the display panel 2 turns its optical path and passes through the refractive lens 4-2 three times. Finally, the light further passes through the refractive lens 4-1 and is guided to become approximately parallel light at pupil position P1.

[0027] First, the refractive lens 4-2 and the half mirror 5 will be described. The refractive lens 4-2 is located between the half mirror 5 and the QWP 7-1, and collects light from the display panel 2. The half mirror 5 is located between the refractive lens 4-2 and the display panel 2, more specifically between the refractive lens 4-2 and the QWP 7-2 in this example, and transmits a portion of the incident light (for example, approximately 50%) and reflects the remainder. The half mirror 5 may be a film (half mirror film) provided on the surface of the refractive lens 4-2 facing the display panel 2. The optical system 3 will be further described with reference to FIG. 2.

[0028] 2 is a diagram showing an example of a schematic configuration of the optical system 3. The refractive lens 4-1 is not shown. Note that although some optical elements are depicted as being spaced apart, in reality they may be spaced apart at intervals shorter than those shown in the drawing, and may even be adjacently or overlappingly arranged.

[0029] In Figure 2, the direction of light at several locations in the optical system 3 is schematically indicated by white arrows. This light may contain various polarized light (polarization components). Examples of polarized light are linearly polarized light and circularly polarized light. The polarization direction is schematically indicated by black arrows. Of linearly polarized light, polarized light polarized in the X-axis direction is also referred to as X-polarized light. Light polarized in the Y-axis direction is also referred to as Y-polarized light. Of circularly polarized light, right-handed circularly polarized light is also referred to as RCP. Left-handed polarized light is illustrated as LCP.

[0030] The diffractive lens 8 is located between the refractive lens 4-2 and the display panel 2 ( FIG. 1 ), more specifically, in this example, between the QWP 7-3 and the refractive lens 4-3. The diffractive lens 8 is configured to output (emit) circularly polarized light in a direction corresponding to the polarization direction of the incident polarized light, and also has a lens function. In this example, Y-polarized light and X-polarized light are incident on the diffractive lens 8 and are output as right-handed circularly polarized light and left-handed circularly polarized light. The center of the diffractive lens 8 may have positive power. In other words, at least the center of the diffractive lens 8 can function as a focusing lens. Note that the center may be, for example, a portion corresponding to the range from the optical axis to the intermediate image height (a range excluding the vicinity of the maximum image height). The peripheral portion outside the center may be a portion corresponding to the maximum image height. To the extent consistent, the center and peripheral portions of other optical elements described below may also be interpreted in a similar manner.

[0031] The diffractive lens 8 may be a polarized diffractive lens. This makes it easier to deal with oblique incidence and wavelength variations. It is possible to guide light efficiently and also to cut flare and ghosts. It is possible to reduce chromatic aberration of magnification. Unless otherwise specified, the diffractive lens 8 is assumed to be a polarized diffractive lens.

[0032] The QWP 7-3 converts into linearly polarized light the circularly polarized light from the diffractive lens 8. In this example, the QWP 7-3 converts the left-handed circularly polarized light and the right-handed circularly polarized light from the diffractive lens 8 into Y-polarized light and X-polarized light.

[0033] The polarizer 6-2 passes only light of a specific polarization and reflects light of other polarizations. In this example, the polarizer 6-2 passes Y-polarized light.

[0034] By providing the polarizer 6-2, it is possible to limit the polarized light that is incident on the subsequent QWP 7-2. This is effective when the display panel 2 emits light containing various polarized lights, such as an OLED. If the display panel 2 emits only light containing specific polarized lights, such as an LCD, the polarizer 6-2 and QWP 7-2 may be unnecessary.

[0035] The QWP 7-2 converts the linearly polarized light from the polarizer 6-2 into circularly polarized light. In this example, the QWP 7-2 converts the Y-polarized light from the polarizer 6-2 into right-handed circularly polarized light.

[0036] A portion of the right-handed circularly polarized light from the QWP 7-2 passes through the half mirror 5, and then passes through the refractive lens 4-2 to enter the QWP 7-1.

[0037] QWP 7-1 converts the right-handed circularly polarized light that has passed through the refractive lens 4-2 into Y-polarized light. In this example, polarizer 6-1 passes X-polarized light and reflects Y-polarized light. Therefore, the Y-polarized light from QWP 7-1 is reflected by polarizer 6-1 and enters QWP 7-1 again. QWP 7-1 converts the Y-polarized light from polarizer 6-1 into right-handed circularly polarized light. This right-handed circularly polarized light passes through refractive lens 4-2, and a portion of it is reflected by half mirror 5. The reflected light becomes left-handed circularly polarized light, passes through refractive lens 4-2, and enters QWP 7-1. In this way, the light folds its optical path and passes through refractive lens 4-2 three times.

[0038] Furthermore, the QWP 7-1 converts the left-handed circularly polarized light that passed through the refractive lens 4-2 into X-polarized light. This X-polarized light passes through the polarizer 6-1 and enters the refractive lens 4-1 (FIG. 1). The light from the refractive lens 4-1 becomes approximately parallel at pupil position P1, and the image is observed by the user U1.

[0039] 2, several optical surfaces included in the optical system 3 are indicated by symbols. Specifically, the surface of the polarizer 6-1 is referred to as optical surface s3 and is illustrated. The surface of the refractive lens 4-2 on the pupil position P1 side is referred to as optical surface s5 and is illustrated. The surface of the half mirror 5 is referred to as optical surface s6 and is illustrated. The surface of the refractive lens 4-3 on the pupil position P1 side (positive Z-axis direction side) is referred to as optical surface s18 and is illustrated. These optical surfaces may correspond to the third, fifth, sixth, and eighteenth optical surfaces through which light traveling from pupil position P1 toward the display panel 2 (light traveling along the negative Z-axis direction) passes.

[0040] Some optical surfaces included in the optical system 3 are reflective surfaces. Of the above optical surfaces, the optical surface s3 is a first reflective surface (pupil-side reflective surface) located between the pupil position P1 and the refractive lens 4-2. The optical surface s6 is a second reflective surface (panel-side reflective surface) located between the refractive lens 4-2 and the display panel 2. The refractive lens 4-2 can also be said to be located between the optical surfaces s3 and s6. The refractive lens 4-1 (FIG. 1) can also be said to be located between the pupil position P1 and the optical surface s3. The refractive lens 4-3 can also be said to be located between the optical surface s6 and the display panel 2 (FIG. 1).

[0041] To achieve a wider angle of view, some optical surfaces are characterized by their partial curvature. The partial curvature is also referred to as the partial curvature κ. The partial curvature κ is the radially-based converted curvature of each portion of the optical surface (a value obtained by converting the amount of phase delay imparted to light into the curvature of an aspherical surface). In the case of a diffractive surface, the partial curvature κ indicates the value obtained by converting the amount of phase delay imparted to each portion of the optical surface into the curvature of an aspherical surface (also called the converted partial curvature). In other words, the partial curvature κ of a diffractive surface is the inverse of the phase partial curvature, and when it is positive, it becomes the focusing power. For example, light passing through a portion with a positive value of the partial curvature κ is directed toward the optical axis OA1 (focusing power).

[0042] In the optical system 3, a positive partial curvature κ means a configuration in which the center of curvature of the partial curvature κ is located on the display panel 2 side (negative Z-axis direction side), and a negative partial curvature κ means a configuration in which the center of curvature of the partial curvature κ is located on the pupil position P1 side (positive Z-axis direction side).

[0043] Some optical surfaces included in the optical system 3 are configured so that the partial curvature κ of each portion varies depending on the distance from the optical axis OA1. The distance from the optical axis OA1 is referred to as the distance h. The partial curvature κ may be specified (defined, etc.) as a function of the distance h. Specifically, the partial curvatures κ of the above-mentioned optical surfaces s3, s5, s6, and s18 will be described with reference to FIGS. 3 to 10.

[0044] 3 and 4 are diagrams showing examples of the optical surface s3. The optical surface s3, i.e., the polarizer 6-1, is shown schematically when viewed from the front (when viewed in the Z-axis direction). The optical surface s3 and the polarizer 6-1 may be interchangeable within the scope of no contradiction.

[0045] 3, the polarizer 6-1 has a circular shape whose center is located on the optical axis OA1. The radius of the polarizer 6-1 is referred to as radius D1.

[0046] The polarizer 6-1 includes a central portion 60 and a peripheral portion 61. The central portion 60 is a portion that includes the center of the polarizer 6-1. The peripheral portion 61 is a portion that is located outside the central portion 60. The peripheral portion 61 may include an edge portion of the polarizer 6-1.

[0047] In terms of distance h, the central portion 60 is a portion corresponding to a range of relatively small distances h from the optical axis OA1 to the intermediate image height (including distance h = 0). The peripheral portion 61 is a portion corresponding to a range of relatively large distances h near the maximum image height (which may include distance h = radius D1).

[0048] 4 represents the distance h. The horizontal axis of the graph represents the partial curvature κ. Distances h10 and h11 are shown as distances. Distance h10 is an arbitrary distance h within a range representing the central portion 60 of the polarizer 6-1. Distance h11 is an arbitrary distance h within a range representing the peripheral portion 61 of the polarizer 6-1.

[0049] The central portion 60 (h=h10) of the polarizer 6-1 has a negative partial curvature κ. The peripheral portion 61 (h=h11) has a positive partial curvature κ. The following conditions are met: partial curvature κ(h10)<0 partial curvature κ(h11)>0

[0050] 5 and 6 are diagrams showing examples of the optical surface s5. The optical surface s5, i.e., the refractive lens 4-2, is shown schematically when viewed from the front. To the extent that there is no contradiction, the optical surface s5 and the refractive lens 4-2 may be interpreted as interchangeable.

[0051] 5, the refractive lens 4-2 has a circular shape whose center is located on the optical axis OA1. The radius of the refractive lens 4-2 is referred to as radius D2.

[0052] The refractive lens 4-2 includes a central portion 40-2 and a peripheral portion 41-2. The central portion 40-2 is a portion that includes the center of the refractive lens 4-2. The peripheral portion 41-2 is a portion that is located outside the central portion 40-2. The peripheral portion 41-2 may include an edge portion of the refractive lens 4-2.

[0053] In terms of distance h, the central portion 40-2 is a portion corresponding to a range of relatively small distances h (including distance h = 0) from the optical axis OA1 to the intermediate image height. The peripheral portion 41-2 is a portion corresponding to a range of relatively large distances h (which may include distance h = radius D2) near the maximum image height.

[0054] 6 shows the partial curvature κ at distances h20 and h21. The distance h20 is an arbitrary distance h within a range indicating the central portion 40-2 of the refractive lens 4-2. The distance h21 is an arbitrary distance h within a range indicating the peripheral portion 41-2 of the refractive lens 4-2.

[0055] The central portion 40-2 (h=h20) of the refractive lens 4-2 has a negative partial curvature κ. The peripheral portion 41-2 (h=h21) has a positive partial curvature κ. The following conditions are met: partial curvature κ(h20)<0 partial curvature κ(h21)>0

[0056] 7 and 8 are diagrams showing examples of the optical surface s6. The optical surface s6, i.e., the half mirror 5, is shown schematically when viewed from the front. Within the scope of no contradiction, the optical surface s6 and the half mirror 5 may be interpreted as interchangeable.

[0057] 7, the half mirror 5 has a circular shape whose center is located on the optical axis OA1. The radius of the half mirror 5 is referred to as radius D3.

[0058] The half mirror 5 includes a central portion 50 and a peripheral portion 51. The central portion 50 is a portion that includes the center of the half mirror 5. The peripheral portion 51 is a portion that is located outside the central portion 50. The peripheral portion 51 may include an edge portion of the half mirror 5.

[0059] In terms of distance h, the central portion 50 is a portion corresponding to a relatively small distance h (including distance h = 0) from the optical axis OA1 to the intermediate image height. The peripheral portion 51 is a portion corresponding to a range of a relatively large distance h (which may include distance h = radius D3) near the maximum image height.

[0060] 8 shows the partial curvature κ at distances h30 and h31. The distance h30 is an arbitrary distance h within a range indicating the center 50 of the half mirror 5. The distance h31 is an arbitrary distance h within a range indicating the peripheral portion 51 of the half mirror 5.

[0061] The central portion 50 (h=h30) of the half mirror 5 may have a negative partial curvature κ. The peripheral portion 51 (h=h31) may have a positive partial curvature κ. The following conditions are met: partial curvature κ(h30)<0 partial curvature κ(h31)>0

[0062] 9 and 10 are diagrams showing examples of the optical surface s18. The optical surface s18, i.e., the refractive lens 4-3, is shown schematically when viewed from the front. To the extent that there is no contradiction, the optical surface s18 and the refractive lens 4-3 may be interpreted as interchangeable.

[0063] 9, the refractive lens 4-3 has a circular shape whose center is located on the optical axis OA1. The radius of the refractive lens 4-3 is referred to as radius D4.

[0064] The refractive lens 4-3 includes a central portion 40-3 and a peripheral portion 41-3. The central portion 40-3 is a portion that includes the center of the refractive lens 4-3. The peripheral portion 41-3 is a portion that is located outside the central portion 40-3. The peripheral portion 41-3 may include an edge portion of the refractive lens 4-3.

[0065] In terms of distance h, the central portion 40-3 is a portion corresponding to a relatively small distance h (including distance h = 0) from the optical axis OA1 to the intermediate image height. The peripheral portion 41-3 is a portion corresponding to a relatively large distance h (which may include distance h = radius D4) near the maximum image height.

[0066] 10 shows the partial curvature κ at a distance h40 and a distance h41. The distance h40 is an arbitrary distance h within a range indicating the central portion 40-3 of the refractive lens 4-3. The distance h41 is an arbitrary distance h within a range indicating the peripheral portion 41-3 of the refractive lens 4-3.

[0067] The central portion 40-3 (h=h40) of the refractive lens 4-3 has a negative partial curvature κ. The peripheral portion 41-3 (h=h41) has a positive partial curvature κ. The following conditions are met: partial curvature κ(h40)<0 partial curvature κ(h41)>0

[0068] When at least some of the above conditions are satisfied, technical effects such as a wider angle of view can be easily obtained. For example, when the center portion 50 of the half mirror 5 has a negative partial curvature κ, a basic configuration is obtained in which the optical surface s5 (panel-side reflecting surface) located on the display panel 2 side has a large light-collecting power near the optical axis OA1.

[0069] Furthermore, since the central portion 60 of the polarizer 6-1 has a negative partial curvature κ, the optical surface s3 of the polarizer 6-1 is oriented in a natural direction relative to the traveling direction of light, thereby suppressing aberrations.

[0070] Consider tracking light from pupil position P1 toward the display panel 2. The refractive lens 4-2 also functions as a refractive surface. For this reason, if the partial curvature κ of the peripheral portion 51 of the half mirror 5 remains negative like the central portion 50, the refractive effect will be too strong, and the angle at which light at the maximum image height passes through the refractive lens 4-3 will be too steep, which could result in total reflection. To prevent this, the peripheral portion 51 of the half mirror 5 is configured to have a positive partial curvature κ. However, negative power is imparted to light at the maximum image height, which would actually cause the light to spread. Therefore, the peripheral portion 61 of the polarizer 6-1 is configured to have a positive partial curvature κ. This maintains the impartation of positive power to light at the maximum image height, making it possible to focus the light on the display panel 2.

[0071] The following explanation is also possible. That is, by having the polarizer 6-1 (optical surface s3) have a positive partial curvature κ in the vicinity of the maximum image height, it is possible to suppress abrupt fluctuations when light passes through that portion due to refraction. On the other hand, by having the corresponding portion of the half mirror 5 (optical surface s6) have a positive partial curvature κ so as to compensate for the insufficient curvature at the outermost periphery, it is possible to maintain the overall power balance.

[0072] To determine the performance of the optical system 3, the maximum object height and f ａｌｌ It is useful to compare it with sin(θ / 2). This allows us to judge the performance of the optical system 3, such as a wider angle of view and higher resolution. The maximum object height corresponds to the distance from the optical axis OA1 to the outermost part of the light incident portion of the display panel 2. ａｌｌ is the total focal length of the optical system 3, and θ is the maximum total angle of view. ａｌｌ The optical system 3 may be designed so that the following condition is met: maximum object height≦f ａｌｌ sin(θ / 2)

[0073] The optical system 3 having the configuration described above makes it possible to achieve a wider angle of view. A wider angle of view provides various advantages. For example, it is possible to increase the viewing angle and reduce the panel size of the display panel 2. It is also possible to achieve higher resolution. Specific design examples will be described with reference to FIGS. 11 to 17.

[0074] <Design Examples of First Embodiment> FIGS. 11 to 17 are diagrams showing design examples of the first embodiment.

[0075] 11 shows the phase characteristics of the diffractive lens 8. The horizontal axis of the graph represents the distance (mm) from the center of the diffractive lens 8. The vertical axis of the graph represents the phase amount (unit: wavelength λ). In this example, the diffractive lens 8 has positive power. The phase delay of light passing through the diffractive lens 8 (the amount of phase delay imparted to light) increases with increasing distance from the center of the diffractive lens 8.

[0076] 12 shows an example of the MTF (Modulation Transfer Function) (MTF equivalent to one pixel) at 80 lines / mm. The pseudo-aperture diameter at pupil position P1 is 8 mm. The light here includes components with wavelengths of 456 nm, 510 nm, 554 nm, 616 nm, and 658 nm, in the proportions (weights) shown in the graph.

[0077] Based on the dimensions when considering eyeball rotation, the resolving power for each incidence angle, more specifically the resolving power in the tangential direction (T) and radial direction (R) for each angle, is shown. Specifically, the value is shown at a position that is eye relief x tan (eyeball rotation angle) away from the optical axis OA1. The diffraction limit (Diff. Limit) is also shown. It can be seen that the eyeball rotation angle and resolving power obtained are within a practical range.

[0078] FIG. 13 shows an example of lateral chromatic aberration during eye rotation. The horizontal axis of the graph represents the distance (difference) between the positions of light of two different wavelengths on the display panel 2 (e.g., on the display surface 2a). The vertical axis of the graph represents the angle (Field Angle) when viewing the optical system 3. The graph line Short-Long represents the difference between the positions of light with a wavelength of 456 nm and light with a wavelength of 658 nm on the display panel 2. The graph line Short-Ref represents the difference between the positions of light with a wavelength of 456 nm and light with a wavelength of 554 nm on the display panel 2. When the angle of eye rotation is small, the lateral chromatic aberration is very small. Although the lateral chromatic aberration increases with increasing angle, it is kept within a practical range and can be addressed by signal processing, etc.

[0079] Figure 14 shows examples of longitudinal aberration, astigmatism, and distortion. The longitudinal aberration is within a practical range and the fluctuation is small. The astigmatism is also within a practical range. The distortion is negative and changes monotonically (there is no inflection point).

[0080] Data for optical surfaces s1 to s21 is shown in Fig. 15. The specific locations of each optical surface are as shown in Fig. 16. Note that optical surface s1 corresponds to pupil position P1.

[0081] As shown in FIG. 15A, in this example, the diagonal length of the display panel 2 (panel diagonal) is 1.3 inches. The horizontal length (e.g., X-axis direction) of the display panel 2 (panel size horizontal) is 24.2 mm. This value is twice the maximum object height, and therefore the maximum object height is 12.1 mm. The maximum object height corresponds to the distance from the optical axis OA1 to the outermost portion of the light incident portion of the display panel 2. The field of view in the horizontal direction (horizontal FoVθ) is 100°. This θ corresponds to the maximum half angle of view. The rotation angle is 69°. The eye-relief is 15 mm. The total system focal length f of the optical system 3 ａｌｌ is 17.1 mm.

[0082] (B) of Figure 15 shows the surface type, radius of curvature, thickness, refractive index, Abbe number, and aperture (half value) of each of optical surfaces s1 to s21. Also shown are some of the main elements of the optical elements described above. The surface types are spherical, aspherical, aspherical reflective, diffractive, or flat. When the surface type is aspherical, the radius of curvature is the paraxial radius of curvature. Here, the thickness indicates the distance from the optical surface to the next optical surface. A thickness with a positive value corresponds to the length in the negative direction of the Z axis, and a 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 is the Abbe number for the difference between the C-line and the F-line, with the d-line as the reference. The aperture (half value) is the distance (radius) from the optical axis OA1, and indicates the distance to the outermost portion through which light can pass.

[0083] The correspondence between some optical surfaces and optical elements will be described. Optical surface s2 is a surface of the refractive lens 4-1 (surface on the pupil position P1 side). Optical surface s3 is a surface of the polarizer 6-1. Optical surface s5 is a surface of the refractive lens 4-2 (surface on the pupil position P1 side). Optical surface s6 is a surface of the half mirror 5. Optical surface s17 is a surface of the diffractive lens 8. Optical surfaces s18 and s19 are surfaces of the refractive lens 4-3 (surface on the pupil position P1 side and surface on the display panel 2 side).

[0084] A QWP 7-2, a polarizer 6-2, and a QWP 7-3 are stacked on the surface of the optical surface s15 on the optical surface s14 side.

[0085] FIG. 15C shows the above-mentioned index of high resolution and wide angle of view, f ａｌｌ The value of sin(θ / 2) is shown. In this example, f ａｌｌ The value of sin(θ / 2) is 13.1 mm. The maximum object height = 12.1 mm is f ａｌｌ It is equal to or less than the value of sin(θ / 2).

[0086] Further data on the optical surface s17 is shown in (D) of Figure 15. The optical surface s17 corresponds to the polarizing diffraction surface of the diffractive lens 8 described above, and imparts a phase delay to light passing through it. If the amount of phase delay is φ, then φ is expressed by the following equation (1): N is the diffraction order, λ is the diffraction order,０ is the normalized wavelength. ｎ An example of values ​​(n=1 to 8) is shown in FIG.

[0087] Further data on the aspherical optical surfaces is shown in (E) of Figure 15. Specifically, coefficients that define the aspherical sag of optical surface s2, optical surfaces s3 to s6, optical surfaces s18, and optical surfaces s19 are shown. The aspherical sag is expressed by the following formula (2). R is the radius of curvature, and h is the height from the optical axis OA1. C' in formula (2) ｎ Numerical examples (n=2 to 8) are shown in FIG.

[0088] Regarding other aspherical type optical surfaces, the aspherical sag amount of optical surfaces s7 and s14 may be similar to that of optical surface s6. The aspherical sag amount of optical surfaces s8 and s13 may be similar to that of optical surface s5. The aspherical sag amount of optical surfaces s9 and s12 may be similar to that of optical surface s4. The aspherical sag amount of optical surfaces s10 and s11 may be similar to that of optical surface s3. The aspherical sag amount of optical surface s12 may be similar to that of optical surface s4.

[0089] FIG. 17 shows the partial curvatures κ of several optical surfaces. Although some of the explanation overlaps with the explanations above, optical surface s2 corresponds to the surface of refractive lens 4-1. Optical surface s3 corresponds to the surface of polarizer 6-1. Optical surface s5 corresponds to the surface of refractive lens 4-2 on the pupil position P1 side (positive Z-axis direction side). Optical surface s6 corresponds to the surface of half mirror 5. Optical surface s17 corresponds to the surface of diffractive lens 8. Optical surfaces s18 and s19 correspond to the surfaces of refractive lens 4-3 on the pupil position P1 side (positive Z-axis direction side) and the display panel 2 side (negative Z-axis direction side). Note that in this example, optical surfaces s2 and s3 have the same aspheric coefficient, and their partial curvatures κ are shown by the same graph line. This also applies to FIGS. 26 and 42 described below.

[0090] For optical surfaces s3 and s6, the partial curvature κ becomes positive when the distance h is relatively large. In this example, the partial curvature κ becomes negative when the distance h is near 0. Furthermore, for optical surfaces s5 and s18, the partial curvature κ becomes positive when the distance h is relatively large. The technical significance is as explained above.

[0091] The disclosed technology is not limited to the first embodiment described above. Other embodiments will be described as second to fifth embodiments.

[0092] 2. Second Embodiment FIG. 18 is a diagram showing an example of the schematic configuration of a display device 1 according to a second embodiment. The optical system 3 of the display device 1 further includes an adhesive 9. The adhesive 9 is provided so as to fill the space between the optical surface s2 and the optical surface s3, i.e., in this example, between the refractive lens 4-1 and the polarizer 6-1. The adhesive 9 may have a refractive index of approximately 1.3 to 1.4. This refractive index value may be, for example, a value between the refractive index of air and the refractive lens 4-2. This reduces the air-lens interface and can reduce ghosting.

[0093] 19 is a diagram showing an example of a schematic configuration of a display device 1 according to a third embodiment. The refractive lens 4-1 of the optical system 3 of the display device 1 is an adhesive. In this example, the adhesive provided on the surface of the polarizer 6-1 on the positive side of the Z axis functions as the refractive lens 4-1.

[0094] 20 to 26 are diagrams showing design examples of the third embodiment. Portions of the design examples of the first embodiment that are not specifically described with respect to conditions, etc., may be the same as those of the first embodiment, and this also applies to the design examples of the fourth to sixth embodiments described below.

[0095] Fig. 20 shows the phase amount of the diffractive lens 8. Fig. 21 shows the MTF. Fig. 22 shows the chromatic aberration of magnification when the eyeball rotates. Fig. 23 shows the longitudinal aberration, astigmatism, and distortion. It can be seen that the angle of eyeball rotation, resolving power, and chromatic aberration of magnification are within practical ranges.

[0096] FIG. 24 shows data for optical surfaces s1 to s21. The specific locations of each optical surface are as shown in FIG. 25. The design values ​​have been changed appropriately in accordance with the fact that optical surface s2 is realized by adhesive 9. As shown in FIG. 24(C), f ａｌｌ The value of sin(θ / 2) is 13 mm. The maximum object height of 12.1 mm as understood from FIG. 24A is f ａｌｌ The value is equal to or less than sin(θ / 2). Higher resolution and wider angle of view are achieved.

[0097] 26 shows the partial curvatures κ of several optical surfaces. For optical surfaces s3 and s6, the partial curvature κ becomes positive when the distance h is relatively large. In this example, the partial curvature κ becomes negative when the distance h is near 0. Furthermore, for optical surfaces s5 and s18, the partial curvature κ becomes positive when the distance h is relatively large.

[0098] 27 is a diagram showing an example of the schematic configuration of a display device 1 according to a fourth embodiment. When the optical system 3 of the display device 1 is viewed from the side (in this example, when viewed in the X-axis direction), the surface of the refractive lens 4-1 facing the pupil position P1 (positive Z-axis direction) and the surface facing the display panel 2 (negative Z-axis direction) have different shapes. In other words, the thickness of the refractive lens 4-1 is not constant.

[0099] <Design Example of Fourth Embodiment> Figures 28 to 34 are diagrams showing design examples of the fourth embodiment. Figure 28 shows the phase amount of the diffractive lens 8. Figure 29 shows the MTF. Figure 30 shows the chromatic aberration of magnification when the eyeball rotates. Figure 31 shows the longitudinal aberration, astigmatism, and distortion. It can be seen that the eyeball rotation angle, resolving power, and chromatic aberration of magnification are within a practical range.

[0100] FIG. 32 shows data for optical surfaces s1 to s21. The specific locations of each optical surface are as shown in FIG. 33. The design values ​​are changed as appropriate in accordance with the change in the shape of the refractive lens 4-1. As shown in FIG. 32(C), f ａｌｌ The value of sin(θ / 2) is 13.1 mm. The maximum object height of 12.1 mm as understood from FIG. 32A is f ａｌｌThe value is equal to or less than sin(θ / 2). Higher resolution and wider angle of view are achieved.

[0101] 34 shows the partial curvatures κ of several optical surfaces. For optical surfaces s3 and s6, the partial curvature κ becomes positive when the distance h is relatively large. In this example, the partial curvature κ becomes negative when the distance h is near 0. Furthermore, for optical surfaces s5 and s18, the partial curvature κ becomes positive when the distance h is relatively large.

[0102] 35 is a diagram showing an example of a schematic configuration of a display device 1 according to a fifth embodiment. The display device 1 differs from the first embodiment (FIG. 1) in that it does not include a diffractive lens 8.

[0103] <Design Example of Fifth Embodiment> Figures 36 to 42 are diagrams showing design examples of the fifth embodiment. Figures 36 and 37 show MTFs. Note that the light in the MTF shown in Figure 37 is green light that contains substantially only components with a wavelength of 554 nm. Figure 38 shows chromatic aberration of magnification when the eyeball rotates. Figure 39 shows longitudinal aberration, astigmatism, and distortion. It can be seen that the eyeball rotation angle, resolving power, and chromatic aberration of magnification are within practical ranges.

[0104] FIG. 40 shows data for optical surfaces s1 to s21. The specific locations of each optical surface are as shown in FIG. 41. The design values ​​have been changed appropriately in accordance with the fact that optical surface s2 is realized by adhesive 9. As shown in FIG. 40(C), f ａｌｌ The value of sin(θ / 2) is 12.8 mm, and the maximum object height of 12.1 mm as understood from FIG. 40A is f ａｌｌ The value is equal to or less than sin(θ / 2). Higher resolution and wider angle of view are achieved.

[0105] The QWP 7-2, polarizer 6-2, and QWP 7-3 are arranged within a 0.01 mm thickness of the optical surface s16. The optical surface s17 is the surface of these films.

[0106] 42 shows the partial curvatures κ of several optical surfaces. For optical surfaces s3 and s6, the partial curvature κ becomes positive when the distance h is relatively large. In this example, the partial curvature κ becomes negative when the distance h is near 0. Furthermore, for optical surfaces s5 and s18, the partial curvature κ becomes positive when the distance h is relatively large.

[0107] 6. Sixth Embodiment FIG. 43 is a diagram showing an example of the schematic configuration of a display device 1 according to a sixth embodiment. In the first embodiment ( FIG. 1 ), the refractive lens 4-1, polarizer 6-1, and QWP 7-1 are arranged separately from the refractive lens 4-2 and closer to the pupil position P1 than the refractive lens 4-2. In the display device 1 according to the sixth embodiment, such refractive lens 4-1, polarizer 6-1, and QWP 7-1 are not present. At least some of their functions are incorporated into the refractive lens 4-2. Specifically, the surface of the refractive lens 4-2 facing the pupil position P1 (the portion on the positive Z-axis direction side) is shown as surface 4a. Surface 4a is configured to have the functions of, for example, the refractive lens 4-1, polarizer 6-1, and QWP 7-1 described above ( FIGS. 1 and 2 , etc.).

[0108] <Design Example of Sixth Embodiment> Figures 44 to 50 are diagrams showing design examples of the sixth embodiment. Figure 44 shows the phase amount of the diffractive lens 8. Figure 45 shows the MTF. Figure 46 shows the chromatic aberration of magnification when the eyeball rotates. Figure 47 shows the longitudinal aberration, astigmatism, and distortion. It can be seen that the eyeball rotation angle, resolving power, and chromatic aberration of magnification are within a practical range.

[0109] FIG. 48 shows data for optical surfaces s101 to s116. The specific locations of each optical surface are as shown in FIG. 49. Optical surface s101 corresponds to pupil position P1. Regarding the correspondence between other optical surfaces and optical elements, optical surfaces s102 and s103 correspond to surface 4a (surface on the pupil position P1 side) of refractive lens 4-2. Optical surfaces s104, s105, and s108 are surfaces of the half mirror 5. Optical surfaces s106 and s107 are surfaces of the refractive lens 4-2. Optical surface s111 is a surface of the diffractive lens 8. Optical surfaces s113 and s114 are surfaces of the refractive lens 4-3. As shown in FIG. 48(C), f ａｌｌ The value of sin(θ / 2) is 12.5 mm, and the maximum object height of approximately 11.8 mm as understood from FIG. 48A is f ａｌｌ The value is equal to or less than sin(θ / 2). Higher resolution and wider angle of view are achieved.

[0110] 50 shows the partial curvatures κ of several optical elements. In the sixth embodiment, the optical surface s103 corresponds to the surface 4a of the refractive lens 4-2, and therefore corresponds to the optical surface s3 (FIG. 17) of the first embodiment. The optical surface s104 corresponds to the surface of the half mirror 5, and therefore corresponds to the optical surface s6 (FIG. 17) of the first embodiment. The optical surface s111 corresponds to the surface of the diffractive lens 8, and therefore corresponds to the optical surface s17 (FIG. 17) of the first embodiment. The optical surfaces s113 and s114 correspond to the surfaces of the refractive lens 4-3 on the pupil position P1 side (positive Z-axis direction) and the display panel 2 side (negative Z-axis direction), and therefore correspond to the optical surfaces s18 and s19 (FIG. 17) of the first embodiment.

[0111] The optical surfaces s103 and s104 have a positive partial curvature κ when the distance h is relatively large. In this example, the partial curvature κ becomes negative when the distance h is near 0. Furthermore, the optical surface s113 has a positive partial curvature κ when the distance h is relatively large, and in this example, the partial curvature κ is positive even when the distance h is near 0.

[0112] <Modification of Sixth Embodiment> The refractive lens 4-3 may be configured to have not only the optical surface s113 described above, but also the optical surfaces s109 to s112. It can be said that the functions of the optical surfaces s109 to s112 are integrated onto the optical surface s113. Alternatively, it can be said that the functions of the QWP 7-2, polarizer 6-2, QWP 7-3, and diffractive lens 8 are incorporated into the refractive lens 4-3. This reduces the number of interfaces between air and glass, which can reduce the amount of ghosting and increase contrast.

[0113] 7. Summary The techniques described above can be specified, for example, as follows. One of the techniques disclosed is an optical system 3. In the following description, the first reflecting surface in the optical system 3 will be described as the optical surface s3 of the polarizer 6-2 in the first to fifth embodiments, and the second reflecting surface will be described as the optical surface s6 of the half mirror 5 in the first to fifth embodiments. The sixth embodiment will be described by appropriately replacing the optical surface s3 and the optical surface s6 with the optical surface s103 of the refractive lens 4-2 and the optical surface s104 of the half mirror 5. As described with reference to FIGS. 1 to 4 , 7 to 8 , 16 to 19 , 25 to 27 , 33 to 35 , 41 to 44 , etc., the optical system 3 converts light from the display panel 2 into substantially parallel light at the pupil position P1 of the user U1, and forms an image at the retina when combined with the eyeball. The optical system 3 includes a refractive lens 4-2, an optical surface s3 (first reflecting surface) of a polarizer 6-1 located between the pupil position P1 and the refractive lens 4-2, and an optical surface s6 (second reflecting surface) of a half mirror 5 located between the refractive lens 4-2 and the display panel 2. The optical system 3 is configured so that light from the display panel 2 passes through the refractive lens 4-2 three times after folding back its optical path (triple-pass type). The peripheral portion of the optical surface s3, i.e., the peripheral portion 61 of the polarizer 6-1, has a positive partial curvature k (partial curvature κ(h11)>0). The center portion of the optical surface s6, i.e., the center portion 50 of the half mirror 5, has a negative partial curvature k (partial curvature κ(h30)<0). A positive partial curvature κ is a configuration in which the center of curvature of the partial curvature κ is located on the display panel 2 side (negative side of the Z axis), and a negative partial curvature κ is a configuration in which the center of curvature of the partial curvature κ is located on the pupil position P1 side (positive side of the Z axis). As described above, it is possible to widen the angle of view of the optical system 3.

[0114] As described with reference to Figures 7, 8, 17, 26, 34, 42, 50, etc., the optical surface s6, i.e., the peripheral portion 51 of the half mirror 5, may have a positive partial curvature κ (partial curvature κ(h31)>0). As described with reference to Figures 3, 4, 17, 26, 34, 42, 50, etc., the central portion of the optical surface s3, i.e., the central portion 60 of the polarizer 6-1, may have a negative partial curvature κ (partial curvature κ(h10)<0). This further increases the possibility of achieving a wider angle of view.

[0115] 1 and 2, the optical system 3 may include a diffractive lens 8 located between the refractive lens 4-2 and the display panel 2. The center of the diffractive lens 8 may have positive power, which can reduce, for example, chromatic aberration of magnification.

[0116] As described with reference to FIGS. 1 and 2 , the optical system 3 may include, in addition to the refractive lens 4-2 (second refractive lens), a refractive lens 4-1 (first refractive lens) located between the pupil position P1 and an optical surface s3 (first reflective surface) of the polarizer 6-1, and a refractive lens 4-3 (third refractive lens) located between an optical surface s6 (second reflective surface) of the half mirror 5 and the display panel 2. Such a configuration including three lenses can further increase the possibility of achieving a wide angle of view. As described with reference to FIGS. 5 , 6 , 17 , 26 , 34 , and 42 , the peripheral portion 41-2 of the optical surface s5 of the refractive lens 4-2 on the pupil position P1 side may have a positive partial curvature κ (partial curvature κ(h21)>0). 9, 10, 17, 26, 34, 42, etc., the peripheral portion 41-3 of the optical surface s18 on the pupil position P1 side (positive Z-axis direction side) of the refractive lens 4-3 may have a positive partial curvature κ (partial curvature κ(h41)>0), which can further enhance the aberration reduction effect, for example.

[0117] 1, 15, 24, 32, 40, 48, etc., the optical system 3 may be designed so that maximum object height≦total system focal length×sin (maximum half angle of view), thereby obtaining a large angle of view with a small panel size.

[0118] 18 and other drawings, the optical system 3 may include an adhesive 9 provided so as to fill the gap between the optical surface s3 (first reflecting surface) of the polarizer 6-1 and the refractive lens 4-1. This reduces the air-lens interface and reduces ghosting.

[0119] As described with reference to Fig. 19 etc., the refractive lens 4-1 may be an adhesive material. In this way, a design using an adhesive as one of the refractive lenses is also possible. For example, this can contribute to simplifying the configuration, making it smaller and thinner, etc.

[0120] 27 and other figures, when viewed from the side (when viewed in the X-axis direction), the surface of the refractive lens 4-1 facing the pupil position P1 (positive Z-axis direction side) and the surface facing the display panel 2 (Z-axis direction side) may have different shapes. In this way, a design using a refractive lens 4-1 with a non-constant thickness is also possible.

[0121] The display device 1 described with reference to Figures 1 to 4, 7 to 8, 16 to 19, 25 to 27, 33 to 35, 41 to 44, etc., is also one of the disclosed technologies. The display device 1 (for example, a head-mounted display device) includes a display panel 2 and an optical system 3 that converts light from the display panel 2 into substantially parallel light at a pupil position P1 of a user U1 and forms an image at the retina when combined with the eyeball. An example configuration of the optical system 3 is as described above. This enables the display device 1 to have a wider angle of view.

[0122] The effects described in this disclosure are merely examples and are not limited to the disclosed content. Other effects may be achieved. Furthermore, the technical scope of this disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of this disclosure. For example, the QWP 7-1 and the polarizer 6-1 may be provided on the surface of the refractive lens 4-1 on the pupil position P1 side (positive Z-axis direction side) rather than on the surface on the display panel 2 side (negative Z-axis direction side).

[0123] Note that the present technology can also have the following configurations. (1) An optical system that converts light from a display panel into approximately parallel light at a user's pupil position and forms an image at a retina position when combined with the eyeball, comprising: a refractive lens; a first reflecting surface located between the pupil position and the refractive lens; and a second reflecting surface located between the refractive lens and the display panel, wherein light from the display panel is configured to turn its optical path and pass through the refractive lens three times, a peripheral portion of the first reflecting surface has a positive partial curvature, and a central portion of the second reflecting surface has a negative partial curvature, the positive partial curvature has a center of curvature on the display panel side, and the negative partial curvature has a center of curvature on the pupil position side. (2) The optical system according to (1), wherein the peripheral portion of the second reflecting surface has a positive partial curvature. (3) The optical system according to (1) or (2), wherein a central portion of the first reflecting surface has a negative partial curvature. (4) The optical system according to (3), comprising a diffractive lens located between the refractive lens and the display panel. (5) The optical system according to (4), wherein a central portion of the diffractive lens has positive power. (6) The optical system according to any of (3) to (5), wherein the refractive lens is a second refractive lens, and wherein the optical system comprises: a first refractive lens located between the pupil position and the first reflecting surface; and a third refractive lens located between the second reflecting surface and the display panel. (7) The optical system according to (6), wherein a peripheral portion of a surface of the second refractive lens on the pupil position side has a positive partial curvature. (8) The optical system according to (7), wherein a peripheral portion of a surface of the third refractive lens on the pupil position side has a positive partial curvature. (9) The optical system according to any one of (3) to (8), which is designed so that maximum object height≦total system focal length×sin (maximum half angle of view). (10) The optical system according to any one of (1) to (9), wherein the refractive lens is a second refractive lens, and the optical system includes: a first refractive lens located between the pupil position and the first reflecting surface; and an adhesive provided so as to fill a gap between the first reflecting surface and the first refractive lens.(11) The optical system according to any one of (1) to (10), wherein the refractive lens is a second refractive lens, and the optical system includes a first refractive lens located between the pupil position and the first reflecting surface, and the first refractive lens is an adhesive. (12) The optical system according to any one of (1) to (11), wherein the refractive lens is a second refractive lens, and the optical system includes a first refractive lens located between the pupil position and the first reflecting surface, and a surface of the first refractive lens facing the pupil position and a surface facing the display panel have mutually different shapes when viewed from the side. (13) The optical system according to any one of (1) to (12), wherein the optical system includes a polarizer having the first reflecting surface. (14) The optical system according to any one of (1) to (13), wherein the optical system includes a half mirror having the second reflecting surface. (15) A display device comprising: a display panel; and an optical system that converts light from the display panel into approximately parallel light at a pupil position of a user and forms an image at a retina position when combined with the eyeball, wherein the optical system includes: a refractive lens, a first reflecting surface located between the pupil position and the refractive lens, and a second reflecting surface located between the refractive lens and the display panel, wherein light from the display panel is configured to turn its optical path and pass through the refractive lens three times, a peripheral portion of the first reflecting surface has a positive partial curvature, and a central portion of the second reflecting surface has a negative partial curvature, wherein the positive partial curvature has a center of curvature on the display panel side, and the negative partial curvature has a center of curvature on the pupil position side. (16) The display device according to (15), which is a head-mounted display device.

[0124] REFERENCE SIGNS LIST 1 display device 2 display panel 2a display surface 3 optical system 4 refractive lens 4-1 refractive lens (first refractive lens) 4-2 refractive lens (second refractive lens) 4-3 refractive lens (third refractive lens) 40-2 center portion 40-3 center portion 41-2 peripheral portion 41-3 peripheral portion 5 half mirror 50 center portion 51 peripheral portion 6 polarizer 6-1 polarizer 6-2 polarizer 60 center portion 61 peripheral portion 7 QWP 7-1 QWP 7-2 QWP 8 diffractive lens 9 adhesive OA1 optical axis P1 pupil position U1 user s3 optical surface (first reflecting surface) s5 optical surface s6 optical surface (second reflecting surface) s18 optical surface s103 Optical surface (first reflecting surface) s104 Optical surface (second reflecting surface)

Claims

1. An optical system that makes the light from a display panel into substantially parallel light at the user's pupil position and forms an image at the retina position when combined with the eyeball, comprising: a refractive lens; a first reflecting surface located between the pupil position and the refractive lens; a second reflecting surface located between the refractive lens and the display panel, wherein the light from the display panel is configured to fold back its optical path and pass through the refractive lens three times, the peripheral portion of the first reflecting surface has a positive partial curvature, the central portion of the second reflecting surface has a negative partial curvature, the positive partial curvature is configured such that the center of curvature of the partial curvature is on the display panel side, and the negative partial curvature is configured such that the center of curvature of the partial curvature is on the pupil position side.

2. The optical system according to claim 1, wherein the peripheral portion of the second reflecting surface has a positive partial curvature.

3. The optical system according to claim 1, wherein the central portion of the first reflecting surface has a negative partial curvature.

4. The optical system according to claim 3, further comprising a diffractive lens located between the refractive lens and the display panel.

5. The optical system according to claim 4, wherein the central portion of the diffractive lens has a positive power.

6. The refractive lens is a second refractive lens, and the optical system further comprises a first refractive lens located between the pupil position and the first reflecting surface, and a third refractive lens located between the second reflecting surface and the display panel, according to claim 3.

7. The optical system according to claim 6, wherein the peripheral portion of the surface of the second refractive lens on the pupil position side has a positive partial curvature.

8. The optical system according to claim 7, wherein the peripheral portion of the surface of the third refractive lens on the pupil position side has a positive partial curvature.

9. The optical system according to claim 3, designed such that the maximum object height ≤ the focal length of the entire system × sin (maximum half field angle).

10. The refractive lens is a second refractive lens, and the optical system further comprises a first refractive lens located between the pupil position and the first reflecting surface, and an adhesive provided to fill the space between the first reflecting surface and the first refractive lens, according to claim 1.

11. The refractive lens is a second refractive lens, and the optical system includes a first refractive lens positioned between the pupil position and the first reflecting surface, and the first refractive lens is an adhesive. The optical system according to claim 1.

12. The refractive lens is a second refractive lens, and the optical system includes a first refractive lens positioned between the pupil position and the first reflecting surface. When viewed from the side, the surface of the first refractive lens on the pupil position side and the surface on the display panel side have different shapes. The optical system according to claim 1.

13. The optical system according to claim 1, comprising a polarizer having the first reflecting surface.

14. The optical system according to claim 1, comprising a half mirror having the second reflecting surface.

15. A display device comprising a display panel and an optical system that makes the light from the display panel into substantially parallel light at the pupil position of the user and forms an image at the retina position when combined with the eyeball. The optical system includes a refractive lens, a first reflecting surface positioned between the pupil position and the refractive lens, and a second reflecting surface positioned between the refractive lens and the display panel. The light from the display panel is configured to be folded back and pass through the refractive lens three times. The peripheral portion of the first reflecting surface has a positive partial curvature, and the central portion of the second reflecting surface has a negative partial curvature. The positive partial curvature is configured such that the center of curvature of the partial curvature is on the display panel side, and the negative partial curvature is configured such that the center of curvature of the partial curvature is on the pupil position side.

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

Images