Near-eye optical system and head-mounted display device

Abstract

Embodiments of the present application provide a near-eye optical system and a head-mounted display device; wherein the near-eye optical system at least comprises a first lens, a polarization reflection element, a phase retarder, a second lens and a light splitting element arranged in sequence along the same optical axis, the surface of the first lens close to the second lens is a first surface, and the polarization reflection element is arranged on the first surface; the number of inflection points on the first surface is n, and n is greater than or equal to 1, the inflection point is a turning point at which the absolute value of sag increases and then decreases on the first surface, the maximum value in the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface is SAG2, the absolute value of the maximum sag of the first surface is SAG1, and SAG1 and SAG2 satisfy: 0.01≤SAG2 / SAG1<0.5.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of optical imaging technology, and more particularly, to a near-eye optical system and a head-mounted display device. BACKGROUND

[0002] With the development of the light and thin requirements of the VR device, the size of the display used in the VR device is getting smaller and smaller, and along with the requirement of the field of view angle getting larger and larger, leading to the decline of the imaging definition of the VR device. At present, large FOV and high definition are the trend of VR development, but generally speaking, the larger the FOV is, the worse the image quality of the edge field of view will be, and how to ensure the imaging quality while ensuring the large FOV is a problem to be solved. SUMMARY

[0003] The purpose of the present application is to provide a new technical solution of a near-eye optical system and a head-mounted display device.

[0004] In a first aspect, embodiments of the present application provide a near-eye optical system, the near-eye optical system comprising at least a first lens, a polarization reflection element, a phase retarder, a second lens and a light splitting element arranged in sequence along the same optical axis, the surface of the first lens close to the second lens being a first surface, and the polarization reflection element being arranged on the first surface.

[0005] The number of inflection points on the first surface is n, and n≥1, the inflection point being a turning point where the absolute value of sag increases and then decreases on the first surface, the maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface being SAG2, the absolute value of the maximum sag of the first surface being SAG1, and SAG1 and SAG2 satisfying: 0.01≤SAG2 / SAG1<0.5.

[0006] Optionally, SAG1 and SAG2 satisfy: 0.01<SAG2 / SAG1<0.1.

[0007] Optionally, SAG1 and SAG2 satisfy: 0.01<SAG2 / SAG1<0.07.

[0008] Optionally, the optical aperture of the first surface is D, and the minimum optical aperture of the position of the inflection point on the first surface is D1, and D1 and D satisfy: 0.3<D1 / D<1; wherein the first surface is a rotationally symmetric structure.

[0009] Optionally, the phase retarder and the polarization reflection element are arranged in layers to form a superposition element and are arranged on the first surface; or,

[0010] The phase retarder is arranged on a surface of the second lens close to the first lens.

[0011] Optionally, the light splitting element is arranged on a surface of the second lens away from the first lens.

[0012] Optionally, the near-eye optical system further comprises a display screen, the display screen is arranged on a side of the second lens away from the first lens, and at least one lens is arranged between the display screen and the light splitting element.

[0013] Optionally, an optical aperture D of the first surface, an optical total length T1 of the near-eye optical system, and a light emitting surface height H1 of the display screen satisfy: 0.5≤(D-H1) / T1≤1.5; wherein a direction of the light emitting surface height H1 of the display screen is perpendicular to a direction of the optical axis.

[0014] Optionally, a third lens is arranged between the display screen and the light splitting element.

[0015] Optionally, a double-layer protective glass is arranged on the light emitting surface of the display screen, and a thickness of the double-layer protective glass is greater than or equal to 0.5 mm.

[0016] Optionally, the display screen is configured to emit circularly polarized light or natural light.

[0017] In a case where the light emitted by the display screen is natural light, a composite film is further arranged on the light emitting surface of the display screen, the composite film is used to convert the natural light into circularly polarized light, and the composite film at least comprises a phase retarder and a linear polarizer.

[0018] Optionally, a polarizer is arranged on a side of the polarization reflection element away from the phase retarder, and the phase retarder, the polarization reflection element, and the polarizer are arranged in a stacked manner.

[0019] In a second aspect, the present application provides a head-mounted display device. The head-mounted display device comprises:

[0020] a housing; and

[0021] the near-eye optical system according to the first aspect.

[0022] The present application has the following beneficial effects:

[0023] According to the near-eye optical system provided in the embodiments of the present application, by optimizing the surface type of the polarization reflection surface in the light path, the image quality of the edge field of view can be improved under the premise of ensuring a large field of view FOV, so that the visual experience of the user can be improved; the volume of the entire near-eye optical system can be reduced based on the folded light path design, and the thin and light design of the near-eye optical system can be realized.

[0024] Other features of the present specification, and the advantages thereof over existing systems and methods will become more readily apparent from the following detailed description, when read in conjunction with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings incorporated in and forming a part of the specification illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0026] Figure 1 Structure and optical path diagram of a near-eye optical system provided for an embodiment of the present application;

[0027] Figure 2 Schematic diagram of a film attached to a first surface of a first lens provided for an embodiment of the present application;

[0028] Figure 3 One of the sag and optical aperture curve diagrams of a first surface of a first lens provided for an embodiment of the present application;

[0029] Figure 4 One of the sag and optical aperture curve diagrams of a first surface of a first lens provided for an embodiment of the present application;

[0030] Figure 5 Optical architecture diagram of a near-eye optical system provided for an embodiment of the present application;

[0031] Figure 6 Sag and optical aperture curve diagram of a first surface provided for an embodiment of the present application;

[0032] Figure 7 Sag and optical aperture curve diagram of a first surface provided for another embodiment of the present application;

[0033] Figure 8 Sag and optical aperture curve diagram of a first surface provided for yet another embodiment of the present application;

[0034] Figure 9 For Figure 1 Point array diagram of a near-eye optical system shown;

[0035] Figure 10 For Figure 1 Modulation transfer function (MTF) curve diagram of a near-eye optical system shown;

[0036] Figure 11 For Figure 1 Field curvature and distortion diagram of a near-eye optical system shown;

[0037] Figure 12 For Figure 1 Axial chromatic aberration diagram of a near-eye optical system shown;

[0038] Figure 13This is the second structural and optical path diagram of the near-eye optical system provided in the embodiments of this application;

[0039] Figure 14 for Figure 13 The diagram shows a dot array of near-eye optical systems;

[0040] Figure 15 for Figure 13 The diagram shows the modulation transfer function (MTF) curve of the near-eye optical system.

[0041] Figure 16 for Figure 13 The field curvature and distortion diagrams of the near-eye optical system are shown;

[0042] Figure 17 for Figure 13 The diagram showing the transverse chromatic aberration of a near-eye optical system is shown.

[0043] Figure 18 The third structural and optical path diagram of the near-eye optical system provided in the embodiments of this application;

[0044] Figure 19 for Figure 18 The diagram shows a dot array of near-eye optical systems;

[0045] Figure 20 for Figure 18 The diagram shows the modulation transfer function (MTF) curve of the near-eye optical system.

[0046] Figure 21 for Figure 18 The field curvature and distortion diagrams of the near-eye optical system are shown;

[0047] Figure 22 for Figure 18 The diagram shows the chromatic aberration of the near-eye optical system.

[0048] Explanation of reference numerals in the attached figures:

[0049] 1. Display screen; 2. Double-layer protective glass; 3. Polarizer; 4. Third lens; 41. Fifth surface; 42. Sixth surface; 5. Second lens; 51. Third surface; 52. Fourth surface; 6. First lens; 61. First surface; 611. Anti-reflective film; 62. Second surface; 7. Polarizing reflective element; 8. Phase retarder; 9. Beam splitter; 01. Human eye. Detailed Implementation

[0050] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0051] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application or its application and uses.

[0052] Techniques and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification.

[0053] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of exemplary embodiments can have different values.

[0054] It should be noted that like reference numerals and letters refer to like items throughout the attached drawings, and once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0055] The near-eye optical system and the head-mounted display device provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0056] According to an aspect of the embodiments of the present application, a near-eye optical system is provided, which is applicable to a wearable device. The wearable device can be a head-mounted display (HMD), such as a VR head-mounted display device. The VR head-mounted display device includes, for example, a VR smart glasses or a VR smart helmet, and the form of the head-mounted display device is not limited in the embodiments of the present application.

[0057] The near-eye optical system provided by the embodiments of the present application is shown in Figure 1 and Figure 2 , and includes, in sequence along the same optical axis, a first lens 6, a polarization reflection element 7, a phase retarder 8, a second lens 5, and a light splitting element 9. The surface of the first lens 6 close to the second lens 5 is a first surface 61, and the polarization reflection element 7 is arranged on the first surface 61, as shown in Figure 3 . The number of inflection points on the first surface 61 is n, and n≥1. The inflection point is a turning point where the absolute value of sag increases and then decreases on the first surface 61. The maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface 61 is SAG2. The absolute value of the maximum sag of the first surface 61 is SAG1. SAG1 and SAG2 satisfy: 0.01≤SAG2 / SAG1<0.5, as shown in Figure 4 .

[0058] The near-eye optical system provided by the embodiments of the present application is shown in Figures 1 to 4, by performing new surface design on the first surface 61 of the first lens 6 provided with the polarization reflection element 7 in the folded optical path, the image quality of the edge field of view can be ensured on the premise of realizing a large field of view FOV. It should be noted that the large field of view FOV herein is, for example, 100° or more, and the FOV can even reach 105°.

[0059] That is to say, in the near-eye optical system provided in the embodiments of the present application, by reasonably controlling the surface type of the first surface 61 of the first lens 6 provided with the polarization reflection element 7, the imaging quality of the edge field of view can be improved on the premise of a large field of view angle.

[0060] Among them, referring to Figure 1 , the first lens 6 is, for example, a lens near the human eye end.

[0061] In the near-eye optical system provided in the embodiments of the present application, there is at least one inflection point on the surface where the polarization reflection element 7 is located, that is, the first surface 61, and the maximum value SAG2 in the absolute value of the difference between the sagittal height at the inflection point on the first surface 61 and the sagittal height at the maximum aperture and the absolute value SAG1 of the maximum sagittal height of the first surface 61 satisfy the constraint condition 0.01≤SAG2 / SAG1<0.5. This parameter effectively solves the problem that the large FOV and high-definition imaging cannot be considered in the prior art, and especially improves the image quality of the edge field of view.

[0062] According to the near-eye optical system provided in the embodiments of the present application, referring to Figure 1 , the optical structure is shown, Figure 9 , the point array diagram of the near-eye optical system in Figure 1 is shown, and from Figure 9 , it can be seen that the maximum value of the image points in the point array diagram is less than 14μm in the full field of view range, that is, clear imaging can still be achieved in the edge field of view.

[0063] The near-eye optical system provided in the embodiments of the present application is a folded optical path, and the light splitting element 9, the phase retarder 8 and the polarization reflection element 7 are designed in the optical path, and the phase retarder 8 is located between the light splitting element 9 and the polarization reflection element 7.

[0064] Among them, the light splitting element 9 can transmit a part of light and reflect another part of light.

[0065] The light splitting element 9 is, for example, a semi-transmissive and semi-reflective film.

[0066] It should be noted that the reflectivity and transmissivity of the light splitting element 9 can be flexibly adjusted according to specific needs, which is not limited in the embodiments of the present application.

[0067] The phase retarder 8 is, for example, a quarter-wave plate.

[0068] Of course, the phase retarder 8 herein can also be set as other phase retarders such as a half-wave plate and the like according to requirements.

[0069] In the near-eye optical system provided by the embodiments of the present application, the phase retarder 8 is arranged in the folded light path on the side close to the human eye 01 and can be used to change the polarization state of light. For example, the phase retarder 8 can be used to convert linearly polarized light into circularly polarized light or convert circularly polarized light into linearly polarized light.

[0070] The polarization reflection element 7 is a polarization reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or a polarization reflector that reflects linearly polarized light at any specific angle and transmits linearly polarized light in the direction perpendicular to the specific angle.

[0071] It is emphasized that the optical elements of the light splitting element 9, the phase retarder 8, and the polarization reflection element 7 can form a folded light path on the side close to the human eye 01. The arrangement positions of the above-mentioned optical elements are flexible, but it is necessary to ensure that the phase retarder 8 is between the light splitting element 9 and the polarization reflection element 7.

[0072] According to the near-eye optical system provided by the embodiments of the present application, by optimizing the surface type of the polarization reflection surface in the light path, the image quality of the edge field of view can be improved under the premise of ensuring a large field of view FOV, so that the visual experience of the user can be improved. The entire light path is designed based on a folded light path, which can also reduce the volume of the entire near-eye optical system and achieve the lightweight design of the near-eye optical system.

[0073] The maximum value SAG2 of the absolute value of the difference between the sagittal height at the inflection point on the first surface 61 and the sagittal height at the maximum aperture and the absolute value SAG1 of the maximum sagittal height of the first surface 61 can also be optimized to satisfy the relationship: 0.01 < SAG2 / SAG1 < 0.1.

[0074] Further, the maximum value SAG2 of the absolute value of the difference between the sagittal height at the inflection point on the first surface 61 and the sagittal height at the maximum aperture and the absolute value SAG1 of the maximum sagittal height of the first surface 61 satisfy the relationship: 0.01 < SAG2 / SAG1 < 0.07.

[0075] By continuously optimizing the surface type of the first surface 61 provided with the polarization reflection element 7, the image quality of the edge field of view can be further improved, so that the entire picture seen by the user is clearer, thereby enabling the user to obtain better visual experience.

[0076] In a specific example, referring to Figure 6, the absolute value of the maximum sag of the first surface 61 is SAG1 = 3.467 mm, and the maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface 61 is SAG2 = 0.043 mm.

[0077] In a specific example, referring to Figure 7 , the absolute value of the maximum sag of the first surface 61 is SAG1 = 12.3 mm, and the maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface 61 is SAG2 = 0.509 mm.

[0078] In a specific example, referring to Figure 8 , the absolute value of the maximum sag of the first surface 61 is SAG1 = 2.35 mm, and the maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface 61 is 0.157 mm.

[0079] In some examples of the present application, referring to Figure 1 , Figure 3 and Figure 4 , the optical aperture of the first surface 61 is D, the minimum optical aperture at the position of the inflection point on the first surface 61 is D1, and the ratio between D1 and D satisfies: 0.3 < D1 / D < 1; wherein the first surface 61 is a rotationally symmetric structure.

[0080] In the present application, the first lens 6 is a rotationally symmetric structure, and the first surface 61 thereof is also a rotationally symmetric structure. Referring to Figure 3 , the minimum optical aperture of the first surface 61 at the position of the inflection point is D1, and by constraining the ratio between the value of D1 and the optical aperture D of the first surface 61, the position of the inflection point can be further determined, which is beneficial to improving the image quality of the edge field of view.

[0081] Further, the optical aperture of the first surface 61 is D, the minimum optical aperture at the position of the inflection point on the first surface 61 is D1, and the ratio between D1 and D can satisfy the constraint relationship: 0.6 ≤ D1 / D < 1.

[0082] In one example, the optical aperture D of the first surface 61 is 41 mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 39 mm.

[0083] In one example, the optical aperture D of the first surface 61 is 50 mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 17.7 mm.

[0084] In one example, the optical aperture D of the first surface 61 is 44.4 mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 23 mm.

[0085] In some examples of the present application, referring to Figure 1 and Figure 2 , the phase retarder 8 and the polarization reflection element 7 can be stacked to form a combined element and arranged on the first surface 61; or, the phase retarder 8 is arranged on the surface of the second lens 5 close to the first lens 6.

[0086] Referring to Figure 1 , the first lens 6 is, for example, a lens close to the human eye 01, and the second lens 5 is arranged along the same optical axis as the first lens 6, and the second lens 5 is away from the human eye 01 relative to the first lens 6.

[0087] Among them, the first lens 6, for example, includes a first surface 61 away from the human eye 01 and a second surface 62 close to the human eye 01.

[0088] Among them, the second lens 5, for example, includes a third surface 51 away from the human eye 01 and a fourth surface 52 close to the human eye 01, and the fourth surface 52 of the second lens 5 is close to the first surface 61 of the first lens 6.

[0089] In one example, referring to Figure 1 and Figure 2 , the phase retarder 8 and the polarization reflection element 7 are sequentially stacked and arranged on the first surface 61, and the first surface 61 forms a polarization reflection surface. Here, the first lens 6 is used to support the phase retarder 8 and the polarization reflection element 7, which can eliminate the need to introduce a support in the optical path, and can simplify the optical path assembly.

[0090] Of course, in the present application, the phase retarder 8 and the polarization reflection element 7 can also be independently arranged with each other, for example, the phase retarder 8 can be arranged alone on the fourth surface 52.

[0091] In addition, the phase retarder 8 can also be independently arranged in the space between the second lens 5 and the first lens 6 through a support.

[0092] It should be noted that the phase retarder 8 is arranged between the beam splitting element 9 and the polarization reflection element 7.

[0093] For the above-mentioned phase retarder 8 and polarization reflection element 7, the two can be combined to form a combined element by optical adhesive. Among them, the phase retarder 8 is, for example, a quarter-wave plate, and the polarization reflection element 7 is, for example, a polarization reflection film.

[0094] In some examples of the present application, referring to Figure 1 , the light splitting element 9 is arranged on the surface of the second lens 5 away from the first lens 6.

[0095] Referring to Figure 1 , the surface of the second lens 5 away from the first lens 6 is a third surface 51, that is, the light splitting element 9 can be directly arranged on the third surface 51.

[0096] Among them, the light splitting element 9 is, for example, a half-mirror.

[0097] When the light splitting element 9 is arranged on the third surface 51, and the light splitting element 9 is, for example, a half-mirror, the half-mirror can be arranged on the third surface 51 by coating or pasting.

[0098] Of course, the light splitting element 9 can also be supported on the third surface 51 side by a support.

[0099] The light splitting element 9, the phase retarder 8 and the polarization reflection element 7, after being combined with a plurality of lenses, can form a folded light path.

[0100] In some examples of the present application, referring to Figure 1 , the near-eye optical system further comprises a display screen 1, the display screen 1 is arranged on the side of the second lens 5 away from the first lens 6, and at least one lens is arranged between the display screen 1 and the light splitting element 9.

[0101] That is, the number of lenses arranged between the light splitting element 9 (that is, the half-mirror) and the display screen 1 is at least one. The entire near-eye optical system uses at least three lenses.

[0102] It should be noted that when the lens is arranged between the display screen 1 and the light splitting element 9, the optical power of the lens can be positive or negative.

[0103] In some examples of the present application, referring to Figure 1 and Figure 5 , the optical aperture D of the first surface 61, the total optical length T1 of the near-eye optical system and the light emitting surface height H1 of the display screen 1 satisfy: 0.5≤(D-H1) / T1≤1.5; wherein the direction of the light emitting surface height H1 of the display screen 1 is perpendicular to the direction of the optical axis.

[0104] According to the above examples, by constraining the optical aperture D of the first surface 61, the total optical length T1 of the near-eye optical system and the light emitting surface height H1 of the display screen 1, Figure 5The relationship between the optical aperture D of the first surface 61 and the optical total length T1 of the near-eye optical system and the light-emitting surface height H1 of the display screen 1 satisfies 0.79≤(D-H1) / T1≤1.32. The field of view of the near-eye optical system can be further increased.

[0105] Further, the relationship between the optical aperture D of the first surface 61 and the optical total length T1 of the near-eye optical system and the light-emitting surface height H1 of the display screen 1 satisfies 0.79≤(D-H1) / T1≤1.32. The field of view of the near-eye optical system can be further increased.

[0106] In one example, the optical aperture D of the first surface 61 is 41 mm, the optical total length T1 of the near-eye optical system is 18.7 mm, and the light-emitting surface height H1 of the display screen 1 is 26.1 mm.

[0107] In one example, the optical aperture D of the first surface 61 is 50 mm, the optical total length T1 of the near-eye optical system is 18.2 mm, and the light-emitting surface height H1 of the display screen 1 is 26 mm.

[0108] In one example, the optical aperture D of the first surface 61 is 44.4 mm, the optical total length T1 of the near-eye optical system is 18.5 mm, and the light-emitting surface height H1 of the display screen 1 is 27.2 mm.

[0109] In some examples of the present application, a third lens 4 is arranged between the display screen 1 and the light splitting element 9.

[0110] According to the near-eye optical system provided by the embodiments of the present application, at least three lenses can be used in the entire optical path design, which are the first lens 6 close to the eye 01, the third lens 4 close to the display screen 1, and the second lens 5 between the first lens 6 and the third lens 4. The optical scheme of the present application can realize the image quality of the edge field under a large field of view on the basis of the folded optical path by matching the three lenses and optimizing the surface shape of the polarization reflecting mirror.

[0111] It should be noted that the number of lenses used in the near-eye optical system provided by the embodiments of the present application can be adjusted as needed, for example, the number of lenses on the side close to the display screen 1 can be increased.

[0112] That is, the near-eye optical system provided by the embodiments of the present application can further include four or more lenses. With the increase of the number of lenses, the total length of the system can be reduced and the image quality can be further improved, but the weight of the product can be affected.

[0113] In some examples of the present application, a double-layer protective glass 2 is arranged on the light-emitting surface of the display screen 1, and the thickness of the double-layer protective glass 2 is greater than or equal to 0.5 mm.

[0114] The near-eye optical system provided by the embodiments of the present application has double-layer protective glass 2 designed in front of the display screen 1, so that the optical scheme can effectively improve the tolerance of the screen surface to dirt.

[0115] That is, referring to Figure 1 , the light emitted by the display screen 1 is transmitted through the double-layer protective glass 2 on the surface, then transmitted through the third lens 4 and the second lens 5, reflected through the first surface 61 of the first lens 6, reflected through the third surface 51 of the second lens 5, and finally transmitted through the second lens 5 and the first lens 6 to hit the human eye 01.

[0116] In some examples of the present application, the display screen 1 is configured to emit circularly polarized light or natural light. In the case where the light emitted by the display screen 1 is natural light, the light-emitting surface of the display screen 1 is further provided with a composite film material (not shown in the figure) for converting natural light into circularly polarized light, and the composite film material at least includes a phase retardation plate and a linear polarizer. Figure 1

[0117] The near-eye optical system further includes a display screen 1 that can emit light for imaging display.

[0118] For example, the display screen 1 can emit RGB light to form a color image.

[0119] The display screen 1 can be an LCD, LED, OLED, Micro-OLED, ULED, etc. self-luminous screen, or a DMD, etc. reflective screen.

[0120] When the display screen 1 emits natural light, the natural light needs to be first converted in polarization state, so that the natural light is first converted into circularly polarized light before being emitted into each optical element on the left, and finally the light emitted through the first lens 6 hits the human eye 01 for imaging.

[0121] According to the above example, the phase retardation plate and the linear polarizer are combined into a stacked element and attached to the light-emitting surface of the display screen 1, so that the assembly difficulty can be reduced, and two optical elements can be placed at the same time by one assembly.

[0122] The transmission axis direction of the linear polarizer can be along the horizontal direction, the vertical direction, or any other direction. The phase retardation plate is, for example, a quarter-wave plate, which can realize the conversion of linearly polarized light into circularly polarized light and the conversion of circularly polarized light into linearly polarized light.

[0123] Specifically, the fast axis or slow axis direction of the phase retardation plate arranged on the light-emitting surface of the display screen 1 is at an angle of 45° with the transmission axis direction of the linear polarizer.

[0124] ​In some examples of the present application, referring to Figure 2 The side of the polarization reflection element 7 away from the phase retarder 8 is provided with a polarizer 3, and the phase retarder 8, the polarization reflection element 7 and the polarizer 3 are stacked.

[0125] The polarizer 3 is, for example, a linear polarizer, and the transmission axis direction can be along the horizontal direction, the vertical direction or any other direction. The introduction of the polarizer 3 can reduce stray light, which is advantageous for improving the final imaging quality.

[0126] The polarizer 3 can be provided on the side of the polarization reflection element 7 away from the phase retarder 8, and the polarizer 3, the polarization reflection element 7 and the phase retarder 8 are stacked to form a stacked element.

[0127] Of course, please continue to refer to Figure 2 The above-mentioned stacked element can also introduce an anti-reflection film 611.

[0128] The anti-reflection film 611 can be, for example, glued to the side of the polarization reflection element 7 away from the phase retarder 8.

[0129] The near-eye optical system provided by the embodiments of the present application uses at least three lenses, namely the first lens 6, the second lens 5 and the third lens 4 shown in the figure. Of course, the near-eye optical system includes but is not limited to three lenses, and the use of lenses can be adjusted as needed.

[0130] The near-eye optical system provided by the embodiments of the present application uses three lenses, namely the first lens 6, the second lens 5 and the third lens 4 mentioned above, and the refractive index and dispersion coefficient of the material used by the three lenses are in the range of 1.4 < n < 2.0, 20 < v < 75.

[0131] In one example, the refractive index of the first lens 6 is 1.54, and the dispersion coefficient is 56.3; the refractive index and dispersion coefficient of the second lens 5 and the third lens 4 are the same, and the refractive index of both can be designed to be 1.54, and the dispersion coefficient can be designed to be 55.7.

[0132] The central thickness T1 of the first lens 6 is in the range of 1 mm ≤ T1 ≤ 8 mm, which includes two optical surfaces, namely the first surface 61 and the second surface 62, and the two surfaces can be aspherical surfaces. The first surface 61 is close to the display screen 1, and the second surface 62 is away from the display screen 1.

[0133] In the first surface 61 of the first lens 6, a structure as shown in Figure 2The phase retarder 8, the polarization reflection element 7 (trans P light and reflects S light) and the polarizer 3 (trans P light) shown can also be provided with an anti-reflection film 611.

[0134] An anti-reflection film can be optionally provided on the second surface 62 of the first lens 6.

[0135] The central thickness T2 of the second lens 5 is in the range of 1mm≤T2≤10mm, and includes two optical surfaces, i.e. the third surface 51 and the fourth surface 52, which can be aspherical or planar. The third surface 51 is close to the display screen 1, and the fourth surface 52 is away from the display screen 1.

[0136] The light splitting element 9 can be provided on the third surface 51 of the second lens 5.

[0137] An anti-reflection film can be optionally provided on the fourth surface 52 of the second lens 5.

[0138] The central thickness T3 of the third lens 4 is in the range of 1mm≤T3≤8mm, and includes two optical surfaces, i.e. the fifth surface 41 and the sixth surface 42, which can be aspherical or planar. The fifth surface 41 is close to the display screen 1, and the sixth surface 42 is away from the display screen 1.

[0139] An anti-reflection film can be respectively provided on the two surfaces of the third lens 4.

[0140] Referring to Figure 1 , the light propagation process of the near-eye optical system is as follows:

[0141] The display screen 1 emits circularly polarized light, which is transmitted through the double-layer protective glass 2, the third lens 4 and the second lens 5, and is changed into linearly polarized light (S light) by the phase retarder 8 on the first surface 61 of the first lens 6. After being reflected by the polarization reflection element 7, the circularly polarized light is changed into linearly polarized light (P light) again by the phase retarder 8, and is transmitted through the second surface 62 of the first lens 6 and enters the human eye 01.

[0142] The optical performance of the near-eye optical system provided in the embodiments of the present application is described below by way of Examples 1 to 3.

[0143] Example 1

[0144] Referring to Figure 1 and Figure 2The near-eye optical system comprises a first lens 6, a polarizer 3, a polarized reflection element 7, a phase retarder 8, a second lens 5, a light splitting element 9, a third lens 4, a double-layer protective glass 2 and a display screen 1 arranged along the same optical axis.

[0145] The double-layer protective glass 2 is arranged on the light-emitting surface of the display screen 1, the light splitting element 9 is arranged on the third surface 51 of the second lens 5, the phase retarder 8, the polarized reflection element 7 and the polarizer 3 form a superposition element arranged on the first surface 61 of the first lens 6, and the phase retarder 8 is located between the light splitting element 9 and the polarized reflection element 7; the third lens 4 is located between the display screen 1 and the light splitting element 9.

[0146] The number of inflection points on the first surface 61 is n, and n≥1, the inflection point is a turning point where the absolute value of the sag of the first surface 61 increases and then decreases; see Figure 6 The absolute value of the maximum sag of the first surface 61 SAG1 is 3.467mm, and the maximum value SAG2 of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface 61 is 0.043mm.

[0147] See Figure 3 The optical aperture D of the first surface 61 is 41mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 39mm.

[0148] See Figure 5 The optical aperture D of the first surface 61 is 41mm, the total optical length T1 of the near-eye optical system is 18.7mm, and the light-emitting surface height H1 of the display screen 1 is 26.1mm.

[0149] Table 1 shows the specific optical parameters of the near-eye optical system of the present embodiment 1.

[0150] Table 1

[0151]

[0152]

[0153] The optical performance of the near-eye optical system provided in the present embodiment 1 can be as shown in Figures 9 to 12 Figure 9 is a point diagram, Figure 10 is an MTF curve, Figure 11 is a field curvature distortion diagram, Figure 12 is a vertical axis chromatic aberration diagram.

[0154] ​Point spread diagram refers to a diffused diagram formed by a point emitting many light rays, which are no longer concentrated on the same point on the image plane due to aberration after passing through the near-eye optical system, and can be used to evaluate the imaging quality of the near-eye optical system. See Figure 9 As shown in the figure, the maximum value of the image point in the point spread diagram of the near-eye optical system provided in Embodiment 1 is less than 15μm, and the imaging of the entire field of view is clear.

[0155] MTF curve is a modulation transfer function diagram, which represents the imaging clarity of the near-eye optical system through the contrast of black and white lines. See Figure 10 As shown in the figure, the MTF of the near-eye optical system provided in Embodiment 1 is >0.5 at 20lp / mm, and the imaging is clear.

[0156] See Figure 11 As shown in the figure, the maximum distortion of the near-eye optical system provided in Embodiment 1 occurs at 1 field of view, and the absolute value is less than 45%.

[0157] The vertical chromatic aberration, also known as the magnification chromatic aberration, mainly refers to a root of a complex color main light ray in the object side, which becomes multiple light rays when exiting the image side due to the dispersion of the refractive system, and the difference between the focal point positions of blue light and red light on the image plane. See Figure 12 As shown in the figure, the maximum chromatic aberration value of the near-eye optical system provided in Embodiment 1 is less than 220μm.

[0158] Embodiment 2

[0159] See Figure 13 The optical structure proposed in Embodiment 2 is basically the same as the optical structure of Embodiment 1 described above, and the main difference between the two is:

[0160] The number of inflection points on the first surface 61 is n, and n≥1, and the inflection point is a turning point where the absolute value of sag increases and then decreases on the first surface 61; see Figure 7 The absolute value of the maximum sag of the first surface 61 SAG1 is 12.3mm, and the maximum value SAG2 of the absolute value of the difference between the sag at the inflection point on the first surface 61 and the sag at the maximum aperture;

[0161] See Figure 3 The optical aperture D of the first surface 61 is 50mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 17.7mm;

[0162] See Figure 5 The optical aperture D of the first surface 61 is 50mm, and the optical total length T1 of the near-eye optical system is 18.2mm, and the light emitting surface height H1 of the display screen 1 is 26mm.

[0163] Table 2 shows the specific optical parameters of the near-eye optical system of this embodiment 2.

[0164] Table 2

[0165]

[0166] The optical performance of the near-eye optical system provided for this embodiment 2 can be shown as follows: Figures 14 to 17 Figure 14 is a schematic diagram of a spot diagram, Figure 15 is a MTF curve diagram, Figure 16 is a field curvature distortion diagram, Figure 17 is an axial chromatic aberration diagram.

[0167] Referring to Figure 14 , the maximum value of the image point in the spot diagram of the near-eye optical system provided by this embodiment 2 is less than 13 μm, and the imaging of the entire field of view is clear.

[0168] Referring to Figure 15 , the MTF of the near-eye optical system provided by this embodiment 2 is >0.3 at 20 lp / mm, and the imaging is clear.

[0169] Referring to Figure 16 , the maximum distortion of the near-eye optical system provided by this embodiment 2 occurs at 1 field of view, and the absolute value is less than 45%.

[0170] Referring to Figure 17 , the maximum chromatic aberration value of the near-eye optical system provided by this embodiment 2 is less than 220 μm.

[0171] Embodiment 3

[0172] Referring to Figure 18 , the optical structure of this embodiment 3 is basically the same as the optical structure of the above-mentioned embodiment 1, and the main difference between the two is that:

[0173] The number of inflection points on the first surface 61 is n, and n≥1, and the inflection point is a turning point where the absolute value of sag increases and then decreases on the first surface 61;

[0174] Referring to Figure 8 , the absolute value of the maximum sag of the first surface 61 SAG1 is 2.35 mm, and the maximum value SAG2 of the absolute value of the difference between the sag at the inflection point on the first surface 61 and the sag at the maximum aperture is 0.157 mm;

[0175] Referring to Figure 3 , the optical aperture D of the first surface 61 is 44.4 mm, and the minimum optical aperture D1 of the first surface 61 at the position of the inflection point is 23 mm;

[0176] Referring to​Figure 5 The optical aperture D of the first surface 61 is 44 mm, the total optical length T1 of the near-eye optical system is 18.5 mm, and the height H1 of the light-emitting surface of the display screen 1 is 27.2 mm.

[0177] Table 3 shows the specific optical parameters of the near-eye optical system in this embodiment 3.

[0178] Table 3

[0179]

[0180]

[0181] The optical performance of the near-eye optical system provided in Embodiment 3 is as follows: Figures 19 to 21 As shown: Figure 19 This is a schematic diagram of a dot-matrix diagram. Figure 20 It is an MTF curve. Figure 21 It is a distortion diagram. Figure 22 It is a vertical axis color difference diagram.

[0182] See Figure 19 As shown, the near-eye optical system provided in this embodiment 3 has a maximum image size of less than 8μm in the dot matrix diagram, and the imaging of the entire field of view is very clear.

[0183] See Figure 20 As shown, the near-eye optical system provided in this embodiment 3 has an MTF of >0.7 at 20 lp / mm, and produces clear images.

[0184] See Figure 21 As shown, in the near-eye optical system provided in this embodiment 3, the maximum distortion occurs in the 1 field of view, and the absolute value is less than 45%.

[0185] See Figure 22 As shown, the near-eye optical system provided in this embodiment 3 has a maximum chromatic difference value of less than 220μm.

[0186] According to another embodiment of this application, a head-mounted display device is provided.

[0187] The head-mounted display device includes a housing and a near-eye optical system as described above.

[0188] The head-mounted display device includes VR smart glasses or VR smart helmets, etc., and this application embodiment does not limit this.

[0189] The specific implementation of the head-mounted display device in this application can refer to the above-described near-eye optical system embodiments, and therefore has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0190] The above embodiments mainly describe the differences between the various embodiments, and the optimization features different between the various embodiments can be combined to form a better embodiment without contradiction. For the sake of brevity, details are not repeated here.

[0191] Although some specific embodiments of the present application have been described in detail by way of example with reference to the accompanying drawings, it is to be understood that the examples are for illustration only and are not intended to limit the scope of the present application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A near-eye optical system, characterized by, The near-eye optical system comprises at least a first lens (6), a polarization reflection element (7), a phase retarder (8), a second lens (5) and a light splitting element (9) arranged in sequence along the same optical axis, the surface of the first lens (6) close to the second lens (5) is a first surface (61), and the polarization reflection element (7) is arranged on the first surface (61); The number of inflection points on the first surface (61) is n, and n≥1, the inflection point is a turning point where the absolute value of the sag increases and then decreases on the first surface (61), the maximum value of the absolute value of the difference between the sag at the inflection point and the sag at the maximum aperture on the first surface (61) is SAG2, the absolute value of the maximum sag of the first surface (61) is SAG1, and SAG1 and SAG2 satisfy: 0.01≤SAG2 / SAG1<0.07; The near-eye optical system further comprises a display screen (1), and a third lens (4) is arranged between the display screen (1) and the light splitting element (9).

2. The near-eye optical system of claim 1, wherein, The optical aperture of the first surface (61) is D, and the minimum optical aperture of the position where the inflection point is located on the first surface (61) is D1, and D1 and D satisfy: 0.3<D1 / D<1; wherein the first surface (61) is a rotationally symmetric structure.

3. The near-eye optical system of claim 1, wherein, The phase retarder (8) and the polarization reflection element (7) are arranged in layers to form a superposition element and are arranged on the first surface (61); or, The phase retarder (8) is arranged on the surface of the second lens (5) close to the first lens (6).

4. The near-eye optical system of claim 1, wherein, The light splitting element (9) is arranged on the surface of the second lens (5) away from the first lens (6).

5. The near-eye optical system of any one of claims 1-4, wherein, The display screen (1) is arranged on the side of the second lens (5) away from the first lens (6), and at least one lens is arranged between the display screen (1) and the light splitting element (9).

6. The near-eye optical system of claim 5, wherein, The optical aperture D of the first surface (61), the total optical length T1 of the near-eye optical system and the light emitting surface height H1 of the display screen (1) satisfy: 0.5≤(D-H1) / T1≤1.5; wherein the direction of the light emitting surface height H1 of the display screen (1) is perpendicular to the direction of the optical axis.

7. The near-eye optical system of claim 5, wherein, A double-layer protective glass (2) is arranged on the light emitting surface of the display screen (1), and the thickness of the double-layer protective glass (2) is ≥0.5mm.

8. The near-eye optical system of claim 5, wherein, The display screen (1) is configured to emit circularly polarized light or natural light; In the case that the light emitted by the display screen (1) is natural light, a composite film material is further arranged on the light emitting surface of the display screen (1) to convert the natural light into circularly polarized light, and the composite film material at least comprises a phase retarder and a linear polarizer.

9. The near-eye optical system of claim 1, wherein, A polarizer (3) is arranged on the side of the polarization reflection element (7) away from the phase retarder (8), and the phase retarder (8), the polarization reflection element (7) and the polarizer (3) are arranged in layers.

10. A head-mounted display device, comprising: Comprise: a housing; and The near-eye optical system of any one of claims 1-9.

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