CN116859562A

CN116859562A - Optical module and head-mounted display device

Info

Publication number: CN116859562A
Application number: CN202310639663.7A
Authority: CN
Inventors: 史柴源
Original assignee: Goer Optical Technology Qingdao Co ltd
Current assignee: Goer Optical Technology Qingdao Co ltd
Priority date: 2023-05-31
Filing date: 2023-05-31
Publication date: 2023-10-10

Abstract

The embodiment of the application provides an optical module and a head-mounted display device; the optical module comprises a lens group, a light splitting element, a first phase retarder and a polarization reflecting element, wherein the light splitting element, the first phase retarder and the polarization reflecting element are arranged between light paths of the lens group; wherein the first phase retarder is located between the light splitting element and the polarizing reflective element; the lens group at least comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along the same optical axis, and the combined focal power phi of the first lens, the second lens, the third lens and the fourth lens is more than or equal to 0.03 and less than or equal to 0.1. The optical module provided by the embodiment of the application has better imaging quality, and especially improves the image quality of the edge view field.

Description

Optical module and head-mounted display device

Technical Field

The embodiment of the application relates to the technical field of optical imaging, in particular to an optical module and head-mounted display equipment.

Background

The core component of the virtual reality technology is an internally-adopted optical system, and the quality of the display image effect of the optical system directly determines the quality of a virtual reality product. In order to reduce the volume and weight of the existing virtual reality products, few lenses or the size of the display screen is generally adopted, so that the image quality of the optical system is poor, especially the image quality of the edge view field is poor, and the visual experience of a user is affected, wherein the reduction of the size of the display screen also causes the view angle of the optical system to be limited.

Disclosure of Invention

The application aims to provide a novel technical scheme of an optical module and a head-mounted display device, and solves the problem that the image quality is affected by poor edge image quality of the existing optical module.

In a first aspect, the present application provides an optical module. The optical module comprises a lens group, a light splitting element, a first phase retarder and a polarization reflecting element, wherein the light splitting element, the first phase retarder and the polarization reflecting element are arranged between light paths of the lens group; wherein the first phase retarder is located between the light splitting element and the polarizing reflective element;

the lens group at least comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along the same optical axis, and the combined focal power phi of the first lens, the second lens, the third lens and the fourth lens is more than or equal to 0.03 and less than or equal to 0.1.

Optionally, the optical module further includes a display screen, where the display screen is located at a side of the first lens away from the second lens;

the outer diameter D3 of the first lens, the outer diameter D4 of the second lens, the outer diameter D5 of the third lens and the caliber D1 of the light emitting surface of the display screen satisfy the following conditions: the (D3+D4)/(D1+D5) is more than or equal to 0.5 and less than or equal to 2.

Optionally, the FOV of the optical module is equal to or greater than 95 °.

Optionally, a distance between a surface of the fourth lens, which is close to the display screen, and a surface of the third lens, which is close to the display screen, is L1, and the optical module meets 0< L1/(D1+D3+D4). Ltoreq.1.

Optionally, a distance between a surface of the fourth lens close to the display screen and a surface of the third lens close to the display screen is L1, a distance between a surface of the third lens close to the display screen and a light emitting surface of the display screen is L2, and the two distance values satisfy:

0<(L2+L1)/(L2-L1)≤1.2。

optionally, the first lens has a center thickness T ₁ The center thickness of the second lens is T ₂ The optical module satisfies: 0<D1/(T ₁ +T ₂ )≤4。

Optionally, the radius of the surface of the second lens close to the display screen is R1, the radius of the surface of the first lens far away from the display screen is R2, and then R1 and R2 satisfy:

0.1≤(R2-R1)/(R1+R2)≤0.5。

optionally, the combined optical power phi of the first lens and the second lens ₁₂ Phi is more than or equal to 0.01 ₁₂ ≤0.07。

Optionally, the combined optical power phi of the first, second and third lenses ₁₂₃ Phi is more than or equal to 0.02 ₁₂₃ ≤0.09。

Optionally, the first lens has an optical power phi ₁ Is 0.ltoreq.phi ₁ <0.05；

The focal power phi of the second lens ₂ Phi is more than or equal to-0.02 ₂ ≤0.02；

The focal power phi of the third lens ₃ Is 0 to<φ ₃ <0.1；

The focal power phi of the fourth lens ₄ Is 0 to<φ ₄ <0.1。

Optionally, the optical module further includes a first polarizing element, where the first phase retarder, the polarizing reflection element, and the first polarizing element are sequentially stacked to form a composite film; the light splitting element is arranged on the third lens, and the composite film is arranged on the fourth lens.

Optionally, the display screen is configured to be capable of emitting circularly polarized light or natural light;

when the light emitted by the display screen is natural light, a superposition element is arranged on any side of the second lens and used for converting the natural light into circularly polarized light;

the superposition element comprises a second phase retarder, a second polarizing element and a third phase retarder which are arranged in a superposition way; wherein the second polarizing element is located between the second phase retarder and the third phase retarder.

Optionally, the superposition element is disposed on a surface of the second lens, which is far away from the display screen, the light splitting element is disposed on a surface of the third lens, which is close to the display screen, and the composite film (9) is disposed on a surface of the fourth lens, which is close to the display screen.

Optionally, the effective focal length EFL of the optical module is 14mm less than or equal to EFL less than or equal to 25mm.

In a second aspect, the present application provides a head mounted display device. The head-mounted display device includes:

a housing; and

the optical module of the first aspect.

The beneficial effects of the application are as follows:

according to the optical module provided by the embodiment of the application, the optical module is of a folding optical path structure, and the image quality can be improved under the condition of ensuring the small volume of the optical module by reasonably designing the combined focal power range of the four lenses, and particularly, the image quality of an edge view field is greatly improved, so that the quality of the whole imaging picture is improved, and the visual experience of a user can be improved.

Other features of the present specification and its advantages will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the specification and together with the description, serve to explain the principles of the specification.

FIG. 1 is a schematic diagram of an optical module according to an embodiment of the present application;

FIG. 2 is a schematic diagram of the dimensional relationships of the first lens, the second lens, the third lens and the display screen according to the embodiment of the present application;

FIG. 3 is a schematic view of a fourth lens with a composite film thereon according to an embodiment of the present application;

FIG. 4 is a schematic view of a second lens with a lamination element thereon according to an embodiment of the present application;

FIG. 5 is a point diagram of the optical module shown in FIG. 1;

FIG. 6 is a graph of MTF for the optical module shown in FIG. 1;

FIG. 7 is a graph of field curvature distortion of the optical module shown in FIG. 1;

FIG. 8 is a vertical axis color difference plot of the optical module shown in FIG. 1;

FIG. 9 is a second schematic diagram of an optical module according to an embodiment of the application;

FIG. 10 is a point diagram of the optical module shown in FIG. 9;

FIG. 11 is a graph of MTF for the optical module shown in FIG. 9;

FIG. 12 is a graph of field curvature distortion of the optical module shown in FIG. 9;

FIG. 13 is a vertical axis color difference plot of the optical module shown in FIG. 9;

FIG. 14 is a third schematic diagram of an optical module according to an embodiment of the application;

FIG. 15 is a point diagram of the optical module shown in FIG. 14;

FIG. 16 is a graph of MTF for the optical module shown in FIG. 14;

FIG. 17 is a graph of field curvature distortion of the optical module shown in FIG. 14;

FIG. 18 is a vertical axis color difference plot of the optical module shown in FIG. 14;

reference numerals:

1. a display screen; 2. screen protection glass; 3. a first lens; 31. a first surface; 32. a second surface; 4. a second lens; 41. a third surface; 42. a fourth surface; 5. a third lens; 51. a fifth surface; 52. a sixth surface; 6. a fourth lens; 61. a seventh surface; 62. an eighth surface; 7. a laminating element; 71. a second phase retarder; 72. a second polarizing element; 73. a third phase retarder; 74. a second anti-reflection film; 8. a spectroscopic element; 9. a composite membrane; 90. a first anti-reflection film; 91. a first phase retarder; 92. a polarizing reflective element; 93. a first polarizing element; 01. and (5) human eyes.

Detailed Description

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

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

Techniques and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate.

In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of exemplary embodiments may have different values.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

Embodiments of the present application provide an optical module and a head-mounted display device described in detail below with reference to the accompanying drawings.

According to an aspect of an embodiment of the present application, there is provided an optical module, which may be suitably applied to a wearable device. The wearable device is for example a head mounted display device (Head mounted display, HMD), such as a VR head mounted display device. The VR head-mounted display device includes, for example, VR smart glasses or VR smart helmets, and the embodiment of the present application does not limit the specific form of the head-mounted display device.

Referring to fig. 1 to 4, the optical module according to the embodiment of the present application includes a lens group, and a light splitting element 8, a first phase retarder 91, and a polarization reflecting element 92 disposed between optical paths of the lens group; wherein the first phase retarder 91 is located between the light splitting element 8 and the polarizing reflecting element 92. The lens group at least comprises a first lens 3, a second lens 4, a third lens 5 and a fourth lens 6 which are sequentially arranged along the same optical axis, and the combined focal power phi of the first lens 3, the second lens 4, the third lens 5 and the fourth lens 6 is more than or equal to 0.03 and less than or equal to 0.1

According to the optical module provided in the above embodiment of the present application, the lens group is designed with four lenses, namely, the first lens 3, the second lens 4, the third lens 5 and the fourth lens 6 shown in fig. 1, and a folded light path is formed on the basis of the four lenses, so that the size of the optical module along the optical axis direction is not excessively increased, and the optical module can be made thinner.

According to the embodiment of the application, an optical module based on a folded optical path (path) is provided, and the optical module can be applied to virtual reality products such as VR products.

According to the optical module provided by the embodiment of the application, the combined focal power formed by the four lenses in the lens group is larger than zero, particularly the above-mentioned 0.03-0.1, and the design is beneficial to correcting the image quality, especially improving the image quality of the marginal view field, so that the final imaging picture has higher picture quality, and the visual experience of a user can be improved.

The optical module provided in the above embodiment of the present application is a folded optical path, and includes, in addition to the lens group, optical elements for forming the folded optical path, such as the light splitting element 8, the first phase retarder 91, and the polarization reflecting element 92. The optical elements (optical films) can be used for forming a folded light path among four lenses of the lens group, so that light rays are folded back in the folded light path to prolong the propagation path of the light rays, which is beneficial to final clear imaging and simultaneously beneficial to reducing the volume of the whole optical module.

For the lens group, the number of lenses used can be flexibly adjusted according to specific needs. Along with the increase of the number of lenses in the folded light path, although the imaging quality of the optical module can be improved, the size and the production cost of the optical module along the optical axis direction (transverse direction) can be affected, so that the optical module has larger size, increased weight and increased cost.

As a preferred mode of the present application, the lens group may be composed of four lenses, see fig. 1. That is, the lens group is composed of a first lens 3, a second lens 4, a third lens 5 and a fourth lens 6. The design ensures that the optical module has good image quality under the condition of smaller volume.

The spectroscopic element 8 is, for example, a semi-transparent and semi-reflective film. The light splitting element 8 may transmit a part of the light, and reflect another part of the light.

Optionally, the reflectance of the spectroscopic element 8 is 47% -53%.

The reflectivity and transmissivity of the light-splitting element 8 may be flexibly adjusted according to specific needs, which is not limited in the embodiment of the present application.

Wherein the first phase retarder 91 is for example a quarter wave plate. Of course, the first phase retarder 91 herein may be configured as other phase retarders such as a half wave plate, etc., as desired.

In the optical module set according to the embodiment of the present application, the first phase retarder 91 is disposed in a folded optical path near one side of the human eye 01, so as to change the polarization state of light. For example for converting linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light.

The polarizing reflection element 92 is, for example, a polarizing reflection film/sheet. The polarizing reflection element 92 is a polarizing reflector that reflects horizontally linearly polarized light, transmits vertically linearly polarized light, or reflects linearly polarized light at any other specific angle, and transmits linearly polarized light in a direction perpendicular to the angle.

In an embodiment of the present application, the first phase retarder 91, in conjunction with the polarizing reflective element 92, can be used to resolve and transmit light.

It should be emphasized that the optical elements of the light splitting element 8, the first phase retarder 91 and the polarizing reflection element 92 may form a folded optical path in the lens group near the human eye 01, and the arrangement positions of the optical elements are flexible, but it is ensured that the first phase retarder 91 is interposed between the light splitting element 8 and the polarizing reflection element 92.

According to some examples of the application, referring to fig. 1, the optical module further comprises a display screen 1, the display screen 1 being located on a side of the first lens 3 facing away from the second lens 4.

Referring to fig. 2, the outer diameter D3 of the first lens 3, the outer diameter D4 of the second lens 4, the outer diameter D5 of the third lens 5, and the aperture D1 of the light emitting surface of the display screen 1 satisfy: the (D3+D4)/(D1+D5) is more than or equal to 0.5 and less than or equal to 2.

According to the above example, referring to fig. 1 and 2, the lens group design in the optical module comprises four lenses, and the four lenses are located between the display screen 1 and the human eye 01, wherein the first lens 3 is a first lens close to the display screen 1, and the second lens 4 and the third lens 5 are a second lens and a third lens close to the display screen 1. In the optical solution of the embodiment of the present application, the dimensional relationships among the first lens 3, the second lens 4, the third lens 5 and the display screen 1 are designed completely, and the dimensional relationships among the four are 0.5 (d3+d4)/(d1+d5) 2 which is designed in the above example, and the parameter design realizes that the field angle FOV of the optical module can be increased and the image quality of the edge field can be considered at the same time when the size of the display screen 1 is smaller. This can enhance the user's immersive experience.

According to the above example, the FOV value of the optical module is equal to or greater than 95 °.

For example, when (d3+d4)/(d1+d5) is 0.5, the optical module can be adapted to a display screen of 1 inch while ensuring that the angle of field is not less than 95 degrees.

For example, when (d3+d4)/(d1+d5) is 1.18, the optical module can be adapted to a display screen of 1.3 inches while ensuring that the angle of field is not less than 95 degrees.

For example, when (d3+d4)/(d1+d5) is 2, the optical module may be adapted to a 2.1 inch display screen while ensuring that the viewing angle is not less than 95 degrees.

When the value of (d1+d4)/D3 is smaller than 0.5 or larger than 2, the FOV of the optical module is smaller and cannot reach 95 degrees.

The optical module provided by the embodiment of the application can adopt the display screen 1 with smaller size, for example, the size of the display screen 1 can be designed to be not more than 2.1 inches, so that the problem that the field angle of the optical module is difficult to be large caused by the small-size display screen is solved under the condition of reducing the weight of the optical module, and the image quality of the edge field of view can be improved.

That is, the optical module provided in the embodiment of the present application designs, on the basis of four lenses, that the dimensions of the three lenses close to the display screen 1 and the dimensions of the display screen 1 satisfy a specific proportional relationship, so that the formed optical module can take into account the performance of a large field of view, and the field of view FOV of the optical module can reach, for example, 95 ° or more.

According to the above example, the optical module facilitates achieving large field of view requirements for virtual reality display devices, such as VR display devices, under small display screens. Based on the small-size design of the display screen 1, the production cost of the optical module is reduced, the weight of the optical module can be reduced, the display screen is more suitable for being worn by a user, the wearing comfort can be improved, and the display screen is free from fatigue even if used for a long time.

In some examples of the present application, referring to 1 and fig. 2, the distance between the surface of the fourth lens 6 near the display screen 1 and the surface of the third lens 5 near the display screen 1 is L1, and the optical module satisfies 0< L1/(d1+d3+d4) +.1.

Referring to fig. 1, the third lens 5 includes a fifth surface 51 near the display screen 1 and a sixth surface 52 far from the display screen 1. The fourth lens 6 comprises a seventh surface 61 close to the display screen 1 and an eighth surface 62 remote from the display screen 1.

According to the above example, the distance between the seventh surface 61 of the fourth lens 6 and the fifth surface 51 of the third lens 5 is L1, and the distance L1 satisfies the relationship of 0< L1/(d1+d3+d4). Ltoreq.1 with the outer diameters of the first lens 3, the second lens 4, and the aperture of the display screen 1, so that the formed optical module can reduce the radial dimension of the optical module while securing a large field of view. This is favorable to promoting user's visual experience and wearing comfort.

When the value of L1/(d1+d3+d4) cannot meet the above range, the size of the optical module will be affected, and the viewing angle requirement of the optical module cannot be met.

In some examples of the present application, a distance between a surface of the fourth lens 6 near the display screen 1 and a surface of the third lens 5 near the display screen 1 is L1, a distance between a surface of the third lens 5 near the display screen 1 and a light emitting surface of the display screen 1 is L2, and the optical module satisfies: 0< (L2+L1)/(L2-L1) is less than or equal to 1.2.

According to the above example, referring to fig. 1, the distance from the seventh surface 61 of the fourth lens 6 to the fifth surface 51 of the third lens 5 is L1, and the distance from the fifth surface 51 of the third lens 5 to the light emitting surface of the display screen 1 is L2, and the two distance values satisfy the relationship of 0< (l2+l1)/(L2-L1) +.1.2 in the above example, it is possible to ensure that the optical module has a large field of view while also reducing the size of the optical module in the optical axis direction. The reduction of the size of the optical module along the optical axis direction is beneficial to realizing the light and thin design of the optical module.

In some examples of the application, the first lens 3 has a center thickness T ₁ The center thickness of the second lens 4 is T ₂ The optical module meets 0<D1/(T ₁ +T ₂ )≤4。

According to the above example, the relationship between the caliber D1 of the display screen 1 and the thicknesses of the two lenses near the display screen 1 is described, so that the thickness uniformity of the first lens 3 and the second lens 4 can be ensured, the process difficulty of lens processing can be reduced, and the processing difficulty of the whole optical module can be reduced.

In some examples of the present application, the radius of the surface of the second lens 4 near the display screen 1 is R1, the radius of the surface of the first lens 3 away from the display screen 1 is R2, and then R1 and R2 satisfy: (R2-R1)/(R1+R2) is more than or equal to 0.1 and less than or equal to 0.5.

According to the above example, referring to fig. 1, the second lens 4 comprises a third surface 41 close to the display screen 1 and a fourth surface 42 distant from the display screen 1. The first lens 3 comprises a first surface 31 close to the display screen 1 and a second surface 32 remote from the display screen 1. The radius R1 of the third surface 41 and the radius R2 of the second surface 32 satisfy the above relationship, that is, 0.1 is less than or equal to (R2-R1)/(r1+r2) is less than or equal to 0.5, so that the formed optical module can ensure that the field curvature of the edge field of the optical module can be reduced while the field of view is increased, and the image quality of the edge field of view is improved.

In some examples of the application, the combined optical power φ of the first lens 3 and the second lens 4 ₁₂ Phi is more than or equal to 0.01 ₁₂ ≤0.07。

According to the above example, the combined power range design of the first lens 3 and the second lens 4 can ensure that the fringe field curvature of the optical module is small, for example < 0.2mm.

In some examples of the application, the combined optical power φ of the first lens 3, the second lens 4, and the third lens 5 ₂ Phi is more than or equal to 0.02 ₁₂₃ ≤0.09。

According to the above example, the design of the combined focal power ranges of the first lens 3, the second lens 4 and the third lens 5 can ensure that the curvature of field of the fringe field of the optical module is smaller, for example, the curvature of field of the fringe field is smaller than 0.2mm, and simultaneously, the air interval between the light emitting surface of the display screen 1 and the first lens 3 is larger than 1mm, so that the specification requirement on the display screen dirt can be reduced.

In some examples of the application, theThe optical power phi of the first lens 3 ₁ Is 0.ltoreq.phi ₁ <0.05; the optical power phi of the second lens 4 ₂ Phi is more than or equal to-0.02 ₂ Less than or equal to 0.02; the optical power phi of the third lens 5 ₃ Is 0 to<φ ₃ <0.1; the optical power phi of the fourth lens 6 ₄ Is 0 to<φ ₄ <0.1。

According to the above example, the optical power ranges of the four lenses contained in the lens group are respectively limited, so that the combined optical power formed by mutually matching and combining the four lenses is positive, aberration can be better corrected, and each lens is convenient to process without increasing production difficulty.

In some examples of the present application, referring to fig. 1, 3 and 4, the optical module further includes a first polarizing element 93, and the first phase retarder 91, the polarizing reflective element 92 and the first polarizing element 93 are sequentially stacked to form a composite film 9. The spectroscopic element 8 is provided on the third lens 5, and the composite film 9 is provided on the fourth lens 6.

According to the above example, the light splitting element 8 and the composite film 9 are disposed in the lens assembly and are disposed on the third lens element 5 and the fourth lens element 6, so that the optical module can form an optical structure of a folded light path, which is beneficial to reducing the dimension of the optical module along the optical axis direction, thereby being beneficial to realizing the light and thin design of the optical module.

In the above example, the optical elements constituting the folded optical path, for example, the spectroscopic element 8 and the composite film 9 are directly separated on different lenses. Thus, the assembly difficulty of the optical module is reduced.

Of course, the light splitting element 8 and the composite film 9 may be respectively disposed on a plate glass (light-transmitting support member), and then be disposed as an independent device in the light path, which is not limited in the embodiment of the present application.

In some examples of the application, referring to fig. 1 and 4, the display screen 1 is configured to be capable of emitting circularly polarized light or natural light.

When the light emitted by the display screen 1 is natural light, a superposition element 7 may be provided on either side of the second lens 4 for converting natural light into circularly polarized light. Referring to fig. 4, the superimposing element 7 includes a second phase retarder 71, a second polarizing element 72, and a third phase retarder 73 that are stacked; wherein the second polarizing element 72 is located between the second phase retarder 71 and the third phase retarder 73.

It should be noted that the light entering the lens group should be circularly polarized light.

When the display screen 1 emits natural light, it is necessary to convert the polarization state of the natural light first, so that the natural light is converted into circularly polarized light first, then enters the lens group on the left side, and finally, the light emitted from the lens group enters the human eye 01 for imaging, see fig. 1.

The means for converting natural light into circularly polarized light is the above-mentioned superposition element 7.

Specifically, referring to fig. 4, the superimposing element 7 includes, for example, a second phase retarder 71, a third phase retarder 73, and a second polarizing element 72 disposed between the two phase retarders. If the display screen 1 emits natural light, the natural light is still natural light after passing through the second phase retarder 71, is changed into linearly polarized light after passing through the second polarizing element 72, and is changed into circularly polarized light after passing through the third phase retarder 73.

Optionally, referring to fig. 4, the laminating element 7 may further include a second anti-reflection film 74, and the second anti-reflection film 74 may be disposed on a side of the third phase retarder 73 facing away from the second polarizing element 72. The introduction of the anti-reflection film can reduce reflection, reduce reflection energy and improve the light efficiency utilization rate.

The anti-reflection film can be formed on the lens in a sticking or coating mode to form interfaces, so that the transmittance can be increased, the reflectivity can be reduced, the image distortion can be reduced, and a user can enjoy clearer image quality to achieve the phenomenon of glare reduction.

Alternatively, referring to fig. 1, a screen protective glass 2 may be disposed on the light-emitting surface of the display screen 1. The screen protection glass 2 may protect the display screen 1. The light emitted by the display screen 1 enters the superposition element 7 after being transmitted by the screen protection glass 2 for polarization state conversion, and natural light can be converted into circularly polarized light.

In some examples of the present application, referring to fig. 1, the superimposing element 7 is disposed on a surface of the second lens 4, which is far from the display screen 1, the light splitting element 8 is disposed on a surface of the third lens 5, which is near the display screen 1, and the composite film 9 is disposed on a surface of the fourth lens 6, which is near the display screen 1.

In the optical module provided by the embodiment of the present application, four lenses, namely, a first lens 3, a second lens 4, a third lens 5 and a fourth lens 6, are disposed in the lens group, and the four lenses adopt the following material refractive index and dispersion coefficient ranges: 1.4< n <1.7, 20< v <75.

For example, the refractive index n=1.54 of the first lens 3 and the dispersion coefficient v=56.3.

For example, the refractive index n=1.54 of the second lens 4, and the dispersion coefficient v=56.3.

For example, the refractive index n=1.54 of the third lens 5 and the dispersion coefficient v=56.3.

For example, the refractive index n=1.54 of the fourth lens 6 and the dispersion coefficient v=55.7.

The imaging quality of the optical module can be improved by adjusting the refractive indexes and the dispersion coefficients of the four lenses to be matched.

The central thickness range of the first lens 3 is, for example: t is not less than 1mm ₁ 10mm or less, comprising two optical surfaces, see fig. 1, a first surface 31 and a second surface 32, respectively, which are aspherical or planar. An anti-reflection film may be disposed on the two optical surfaces. The optical power phi of the first lens 3 ₁ Is 0.ltoreq.phi ₁ <0.05。

The center thickness range of the second lens 4 is, for example: t is not less than 1mm ₂ And 8mm or less, comprising two optical surfaces, see fig. 1, a third surface 41 and a fourth surface 42, respectively, which are aspherical or planar surfaces. The optical power phi of the second lens 4 ₂ Phi is more than or equal to-0.02 ₂ ≤0.02。

The laminating member 7 may be provided on one of the third surface 41 and the fourth surface 42, and then an antireflection film may be attached on the other surface thereof. The anti-reflection film can reduce reflection, reduce reflection energy and improve light efficiency utilization rate. The anti-reflection film can be formed on the lens in a sticking or coating mode to form interfaces, so that the transmittance is increased, the reflectivity is reduced, the image distortion is reduced, a user can enjoy clearer image quality, and the glare is reduced.

The center thickness range of the third lens 5 is, for example: t is not less than 1mm ₃ And 8mm or less, comprising two optical surfaces, see fig. 1, a fifth surface 51 and a sixth surface 52, respectively, which are aspherical or planar surfaces. The optical power phi of the third lens 5 ₃ Is 0< phi ₃ ＜0.1。

For example, the spectroscopic element 8 (for example, a transflective film) may be provided on the fifth surface 51, and an antireflection film may be provided on the sixth surface 52.

The center thickness range of the fourth lens 6 is, for example: t is more than or equal to 0.5mm ₄ And 8mm or less, comprising two optical surfaces, see FIG. 1, a seventh surface 61 and an eighth surface 62, respectively, which are aspherical or planar surfaces. The optical power phi of the fourth lens 6 ₃ Is 0< phi ₄ ＜0.1。

For example, referring to fig. 1 and 3, the composite film 9 may be disposed on the seventh surface 61, and the seventh surface 61 is a surface close to the display screen 1. The composite film 9 includes, for example, a first antireflection film 90, a first phase retarder 91 (e.g., a 1/4 wave plate), a polarizing reflection element 92 (e.g., a polarizing reflection film, P-light-permeable, S-light-permeable), and a first polarizing element 93 (e.g., a polarizing film, P-light-permeable). An anti-reflection film may be provided on the eighth surface 62. The anti-reflection element can reduce reflection, reduce reflection energy and improve light efficiency utilization rate. The first polarizing element 93 may reduce stray light.

Referring to fig. 1, the optical module provided in the embodiment of the present application propagates light as follows:

the display screen 1 emits natural light, which is still natural light after passing through the second phase retarder 71 on the surface of the second lens 4, is changed into linearly polarized light after passing through the second polarizing element 72, is changed into circularly polarized light after passing through the third phase retarder 73, is transmitted through the third lens 5, is changed into linearly polarized light (S-light) after passing through the first phase retarder 91 on the surface of the fourth lens 6, is reflected by the polarizing reflection element 92, is changed into circularly polarized light after passing through the first phase retarder 91 again, is reflected by the light splitting element 8, is changed into linearly polarized light (P-light) after passing through the first phase retarder 91, is transmitted through the fourth lens 6, and is injected into the human eye 01, and finally presents an image in the human eye 01.

According to some examples of the application, the effective focal length EFL of the optical module is 14 mm. Ltoreq.EFL.ltoreq.25 mm.

The optical performance of the optical module provided in the embodiments of the present application is described in detail below by examples 1 to 3.

Example 1

Referring to fig. 1, the optical module provided in this embodiment 1 includes a first lens 3, a second lens 4, a third lens 5, and a fourth lens 6 sequentially disposed along the same optical axis, where a combined optical power Φ of the first lens 3, the second lens 4, the third lens 5, and the fourth lens 6 is 0.03 Φ.ltoreq.0.1; the optical module further comprises a light splitting element 8, a composite film 9 and a superposition element 7, wherein the superposition element 7 is arranged on the fourth surface 432 of the second lens 4, the light splitting element 8 is arranged on the fifth surface 51 of the third lens 5, and the composite film 9 is arranged on the seventh surface 61 of the fourth lens 6.

Wherein the superposition element 7 comprises a second phase retarder 71, a second polarizing element 72 and a third phase retarder 73 which are stacked; wherein the second polarizing element 72 is located between the second phase retarder 71 and the third phase retarder 73;

wherein the composite film 9 includes a first phase retarder 91, the polarizing reflection element 92, and the first polarizing element 93, which are stacked; wherein the polarizing reflective element 92 is located between the first phase retarder 91 and the first polarizing element 93.

The optical module further comprises a display screen 1, wherein the display screen 1 is arranged on one side of the first lens 3, which is away from the second lens 4; the outer diameter D3 of the first lens 3, the outer diameter D4 of the second lens 4, the outer diameter D5 of the third lens 5, and the aperture D1 of the light emitting surface of the display screen satisfy: the (D3+D4)/(D1+D5) is more than or equal to 0.5 and less than or equal to 2.

Table 1 shows specific optical parameters of each lens in the optical module provided in this embodiment 1.

TABLE 1

For the optical module provided in the above embodiment 1, the optical performance of the optical module may be as shown in fig. 5 to 8:

fig. 5 is a schematic view of a point column of an optical module, fig. 6 is an MTF graph of the optical module, fig. 7 is a field curvature distortion graph of the optical module, and fig. 8 is a vertical axis chromatic aberration graph of the optical module.

The point column graph refers to a dispersion graph scattered in a certain range, which can be used for evaluating the imaging quality of an optical module, after a plurality of light rays emitted from one point pass through the optical module, the intersection point of the light rays and an image plane is not concentrated at the same point due to aberration. Referring to fig. 5, the maximum value of the image points in the point column image is less than 8 μm.

The MTF graph is a modulation transfer function graph, and the imaging definition of the optical module is represented by the contrast of the black-white line pair. Referring to FIG. 6, the center MTF was >0.5 at 40lp/mm, and the imaging was clear.

Referring to fig. 7, distortion occurs at maximum at 1 field of view, with an absolute value of less than 40%.

The vertical axis chromatic aberration is also called as chromatic aberration of magnification, and mainly refers to a multi-color principal ray of an object side, which is changed into a plurality of rays when exiting from an image side due to chromatic dispersion of a refraction system, and the difference of focus positions of blue light and red light on an image plane. Referring to fig. 8, the maximum color difference value of the optical module is less than 200 μm.

Example 2

Referring to fig. 9, the optical architecture of the present embodiment 2 is the same as that of the embodiment 1, except that the optical parameters of each lens in the optical module are different, and see table 2 below.

TABLE 2

For the optical module provided in the above embodiment 2, the optical performance thereof may be as shown in fig. 10 to 13: fig. 10 is a schematic view of a point column of an optical module, fig. 11 is an MTF graph of the optical module, fig. 12 is a field curvature distortion graph of the optical module, and fig. 13 is a vertical axis chromatic aberration graph of the optical module.

The point column graph refers to a dispersion graph scattered in a certain range, which can be used for evaluating the imaging quality of an optical module, after a plurality of light rays emitted from one point pass through the optical module, the intersection point of the light rays and an image plane is not concentrated at the same point due to aberration. Referring to fig. 10, the maximum value of the image points in the point column image is less than 8 μm.

The MTF graph is a modulation transfer function graph, and the imaging definition of the optical module is represented by the contrast of the black-white line pair. Referring to FIG. 11, the center MTF was >0.5 at 40lp/mm, and the imaging was clear.

Referring to fig. 12, distortion occurs at maximum at 1 field of view, with an absolute value of less than 40%.

The vertical axis chromatic aberration is also called as chromatic aberration of magnification, and mainly refers to a multi-color principal ray of an object side, which is changed into a plurality of rays when exiting from an image side due to chromatic dispersion of a refraction system, and the difference of focus positions of blue light and red light on an image plane. Referring to fig. 13, the maximum color difference value of the optical module is less than 200 μm.

Example 3

Referring to fig. 14, the optical architecture of this embodiment 3 is the same as that of embodiment 1, except that the optical parameters of each lens in the optical module are different, and see table 3 below.

TABLE 3 Table 3

For the optical module provided in the above embodiment 3, the optical performance thereof may be as shown in fig. 15 to 18: fig. 15 is a schematic view of a point column of an optical module, fig. 16 is an MTF graph of the optical module, fig. 17 is a field curvature distortion graph of the optical module, and fig. 18 is a vertical axis chromatic aberration graph of the optical module.

The point column graph refers to a dispersion graph scattered in a certain range, which can be used for evaluating the imaging quality of an optical module, after a plurality of light rays emitted from one point pass through the optical module, the intersection point of the light rays and an image plane is not concentrated at the same point due to aberration. Referring to fig. 15, the maximum value of the image points in the point column image is less than 8 μm.

The MTF graph is a modulation transfer function graph, and the imaging definition of the optical module is represented by the contrast of the black-white line pair. Referring to FIG. 16, the center MTF was >0.5 at 40lp/mm, and the imaging was clear.

Referring to fig. 17, distortion occurs at maximum at 1 field of view, with an absolute value of less than 40%.

The vertical axis chromatic aberration is also called as chromatic aberration of magnification, and mainly refers to a multi-color principal ray of an object side, which is changed into a plurality of rays when exiting from an image side due to chromatic dispersion of a refraction system, and the difference of focus positions of blue light and red light on an image plane. Referring to fig. 18, the maximum color difference value of the optical module is less than 200 μm.

According to another embodiment of the present application, there is provided a head-mounted display device. The head mounted display device comprises a housing and an optical module as described above.

The head-mounted display device comprises VR intelligent glasses or VR intelligent helmets and the like, and the embodiment of the application is not limited to the VR intelligent glasses or the VR intelligent helmets.

The specific implementation manner of the head-mounted display device of the embodiment of the present application may refer to each embodiment of the optical module, so at least the technical solution of the embodiment has all the beneficial effects, which are not described in detail herein.

The foregoing embodiments mainly describe differences between the embodiments, and as long as there is no contradiction between different optimization features of the embodiments, the embodiments may be combined to form a better embodiment, and in consideration of brevity of line text, no further description is given here.

While certain specific embodiments of the application have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the application. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the application. The scope of the application is defined by the appended claims.

Claims

1. An optical module is characterized by comprising a lens group, a light splitting element (8), a first phase retarder (91) and a polarization reflecting element (92), wherein the light splitting element (8), the first phase retarder and the polarization reflecting element are arranged between light paths of the lens group; wherein the first phase retarder (91) is located between the light splitting element (8) and the polarizing reflective element (92);

the lens group at least comprises a first lens (3), a second lens (4), a third lens (5) and a fourth lens (6) which are sequentially arranged along the same optical axis, and the combined focal power phi of the first lens (3), the second lens (4), the third lens (5) and the fourth lens (6) is more than or equal to 0.03 and less than or equal to 0.1.

2. The optical module according to claim 1, further comprising a display screen (1), the display screen (1) being located on a side of the first lens (3) facing away from the second lens (4);

the outer diameter D3 of the first lens (3), the outer diameter D4 of the second lens (4), the outer diameter D5 of the third lens (5) and the caliber D1 of the light emitting surface of the display screen (1) satisfy the following conditions: the (D3+D4)/(D1+D5) is more than or equal to 0.5 and less than or equal to 2.

3. The optical module of claim 2, wherein the FOV of the optical module is at least 95 °.

4. The optical module according to claim 2, wherein a distance between a surface of the fourth lens (6) close to the display screen (1) and a surface of the third lens (5) close to the display screen (1) is L1, and the optical module satisfies 0< L1/(d1+d3+d4). Ltoreq.1.

5. An optical module according to claim 2, characterized in that the distance between the surface of the fourth lens (6) close to the display screen (1) and the surface of the third lens (5) close to the display screen (1) is L1, the distance between the surface of the third lens (5) close to the display screen (1) and the light emitting surface of the display screen (1) is L2, the two distance values being such that:

0<(L2+L1)/(L2-L1)≤1.2。

6. an optical module according to claim 2, characterized in that the first lens (3) has a central thickness T ₁ The center thickness of the second lens (4) is T ₂ The optical module satisfies: 0<D1/(T ₁ +T ₂ )≤4。

7. An optical module according to claim 2, wherein the radius of the surface of the second lens (4) close to the display screen (1) is R1, and the radius of the surface of the first lens (3) away from the display screen (1) is R2, and then R1 and R2 satisfy:

0.1≤(R2-R1)/(R1+R2)≤0.5。

8. optical module according to claim 1, characterized in that the combined optical power Φ of the first lens (3) and the second lens (4) ₁₂ Phi is more than or equal to 0.01 ₁₂ ≤0.07。

9. An optical module according to claim 1, characterized in that the combined optical power Φ of the first lens (3), the second lens (4) and the third lens (5) ₁₂₃ Phi is more than or equal to 0.02 ₁₂₃ ≤0.09。

10. An optical module according to claim 1, characterized in that the optical power Φ of the first lens (3) ₁ Is 0.ltoreq.phi ₁ <0.05；

The optical power phi of the second lens (4) ₂ Phi is more than or equal to-0.02 ₂ ≤0.02；

The third lens (5) has an optical power phi ₃ Is 0 to<φ ₃ <0.1；

The optical power phi of the fourth lens (6) ₄ Is 0 to<φ ₄ <0.1。

11. The optical module according to claim 2, further comprising a first polarizing element (93), wherein the first phase retarder (91), the polarizing reflective element (92) and the first polarizing element (93) are sequentially stacked to form a composite film (9);

the light splitting element (8) is arranged on the third lens (5), and the composite film (9) is arranged on the fourth lens (6).

12. The optical module according to claim 11, characterized in that the display screen (1) is configured to be able to emit circularly polarized light or natural light;

when the light emitted by the display screen (1) is natural light, a superposition element (7) is arranged on any side of the second lens (4) and used for converting the natural light into circularly polarized light;

wherein the superposition element (7) comprises a second phase retarder (71), a second polarizing element (72) and a third phase retarder (73) which are arranged in a superposition way; wherein the second polarizing element (72) is located between the second phase retarder (71) and the third phase retarder (73).

13. The optical module according to claim 12, wherein the superimposing element (7) is disposed on a surface of the second lens (4) away from the display screen (1), the light splitting element (8) is disposed on a surface of the third lens (5) close to the display screen (1), and the composite film (9) is disposed on a surface of the fourth lens (6) close to the display screen (1).

14. The optical module of any one of claims 1-13 wherein the optical module has an effective focal length EFL of 14mm +.efl +.25 mm.

15. A head-mounted display device, comprising:

a housing; and

the optical module of any one of claims 1-14.