CN115421300A

CN115421300A - Optical module and head-mounted display equipment

Info

Publication number: CN115421300A
Application number: CN202210907088.XA
Authority: CN
Inventors: 史柴源
Original assignee: Goertek Optical Technology Co Ltd
Current assignee: Goertek Optical Technology Co Ltd
Priority date: 2022-07-29
Filing date: 2022-07-29
Publication date: 2022-12-02

Abstract

The application provides an optical module and a head-mounted display device; the optical module comprises a free-form surface prism, a first lens and a second lens; the free-form surface prism comprises a first surface, a second surface and a third surface, wherein the first surface and the third surface are both free-form surfaces, the second surface comprises a first area and a second area, and the second area is provided with a total reflection film; the first lens is positioned on one side of the first surface, the first light is transmitted by the first lens and then enters the free-form surface prism, the first light is totally reflected on the first surface after being reflected by the second area, and the number of times of the first light is more than or equal to 3 in the free-form surface prism; the second lens is positioned on one side of the third surface, and the second light rays are transmitted by the second lens, then enter the free-form surface prism and exit through the first area. The application of the optical module can reflect light rays for at least three times in the free-form surface prism, so that the light ray propagation path is prolonged, and the thickness of the optical module can be reduced while the imaging quality is guaranteed.

Description

Optical module and head-mounted display equipment

Technical Field

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

Background

Augmented Reality (AR) technology is a technology for providing additional information (so-called "Augmented") for a user in the real world by some technical means, organically integrating images of a virtual world and scenes of the real world, and deeply integrating calculated information with the real world, thereby providing richer information and immersive experience for the user.

In a hardware implementation form of augmented reality technology, wearable augmented reality devices, such as AR glasses, are most applied. Along with the promotion of consumer to the product demand, require that AR glasses's is small, can high definition formation of image, this just needs front end optical module itself frivolous and resolution ratio high, but current optical module is compromise high definition formation of image when accomplishing frivolously hardly.

Disclosure of Invention

The utility model aims at providing an optical module and wear display device's new technical scheme.

In a first aspect, the present application provides an optical module comprising:

the free-form surface prism comprises a first surface, a second surface and a third surface, wherein the first surface and the third surface are both free-form surfaces, the second surface comprises a first area and a second area, and the second area is provided with a total reflection film;

the first lens is positioned on one side of the first surface, a first light ray is transmitted by the first lens and then enters the free-form surface prism, the first light ray is reflected by the second area and then is totally reflected on the first surface, and the number of times of turning of the first light ray in the free-form surface prism is more than or equal to 3; and

and the second lens is positioned on one side of the third surface, and second light rays are transmitted by the second lens, then enter the free-form surface prism and are emitted out through the first area.

Optionally, the optical module further includes a polarization reflection element, and the polarization reflection element is located between the free-form surface prism and the second lens.

Optionally, the surface of the second lens close to the free-form surface prism and the third surface are both free-form surfaces and are connected by gluing.

Optionally, a surface of the second lens close to the free-form surface prism is provided with a polarization reflection element.

Optionally, the second lens is configured to transmit the second light, and the second light is a real-world light;

and an antireflection film is arranged on the surface of the second lens, which is far away from the free-form surface prism.

Optionally, the optical module further includes a display screen located on a side of the first lens facing away from the first surface;

the display screen is used for emitting the first light, the first light is transmitted through the first lens and the first surface, reflected through the second area, totally reflected through the first surface, totally reflected through the first area, reflected through the third surface, transmitted through the first area and then enters human eyes.

Optionally, the display screen is arranged along a first direction, and an included angle between the display screen and the first direction is-30 degrees to +30 degrees;

the first direction is perpendicular to the thickness direction of the optical module.

Optionally, the first region is provided with an anti-reflection film;

the length ratio of the second area to the first area is 0.9-3.

Optionally, the first lens includes two surfaces, and both surfaces of the first lens are free-form surfaces.

Optionally, an antireflection film is attached to at least one of the two surfaces of the first lens.

Optionally, the thickness of the free-form surface prism is T ₃ ，T ₃ Satisfies the following conditions: t is more than 0.5mm ₃ ＜15mm。

Optionally, the first lens has a thickness T ₁ ，T ₁ Satisfies the following conditions: t is more than 1mm ₃ ＜10mm；

The thickness of the second lens is T ₂ ，T ₂ Satisfies the following conditions: t is more than 0.5mm ₂ ＜15mm。

Optionally, at least one of the free-form surface prism, the first lens and the second lens is made of a plastic material.

In a second aspect, the present application provides a head mounted display device comprising:

a housing; and

an optical module as described above.

According to the embodiment of the application, the optical module can be applied to AR equipment, for example, a free-form surface prism with three optical surfaces is introduced into an optical path, and light rays of a virtual optical path are reflected in the free-form surface prism for multiple times, so that the purpose of prolonging the light ray propagation path can be achieved, the thickness of the optical module can be reduced, and the imaging quality of the optical module can be guaranteed. The optical module has the characteristics of small size and high resolution.

Other features of the present description and advantages thereof 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 structural diagram of an optical module according to an embodiment of the present disclosure;

FIG. 2 is a graph of MTF of the optical module shown in FIG. 1;

FIG. 3 is a dot-line diagram of the optical module shown in FIG. 1;

FIG. 4 is a diagram illustrating field curvature distortion of the optical module shown in FIG. 1;

FIG. 5 is a vertical axis chromatic aberration diagram of the optical module shown in FIG. 1.

Description of reference numerals:

10. a first lens; 20. a second lens; 30. a free-form surface prism; 31. a first surface; 32. a second surface; 321. a first region; 322. a second region; 33. a third surface; 40. a display screen; 41. a screen protection sheet; 01. a human eye; 02. a first light ray; 03. the second light ray.

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, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise.

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

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

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

According to an aspect of the embodiments of the present application, an optical module is provided, which has a small volume and a high resolution. The optical module may be suitable for application in a Head Mounted Display (HMD), such as an AR Head mounted device. The AR headset may include AR glasses or an AR helmet, etc., which is not particularly limited by the embodiments of the present application.

The embodiment of the present application provides an optical module, as shown in fig. 1, the optical module includes: a free-form surface prism 30, and a first lens 10 and a second lens 20;

the free-form surface prism 30 includes a first surface 31, a second surface 32 and a third surface 33, both the first surface 31 and the third surface 33 are free-form surfaces, the second surface 32 includes a first region 321 and a second region 322, wherein the second region 322 is provided with a total reflection film;

the first lens 10 is located on one side of the first surface 31, the first light 02 is transmitted by the first lens 10 and then enters the free-form surface prism 30, the first light is reflected by the second area 322 and then is totally reflected on the first surface 31, and the number of times of the first light 02 is more than or equal to 3 in the free-form surface prism 30;

the second lens 20 is located at one side of the third surface 33, and the second light 03 is transmitted by the second lens 20, enters the freeform prism 30, and exits through the first region 321.

In the optical module of the embodiment of the present application, the first lens 10 can be used to transmit the virtual image light emitted from the display screen 40, i.e. the first light 02 shown in fig. 1. The second lens 20 may be used to transmit, for example, real world light rays, i.e., the second light ray 03 shown in fig. 1. The whole optical module can receive virtual and real light rays, and imaging can be carried out in human eyes 01 after processing. The optical module of the embodiment of the application can be applied to AR equipment, and a user can view virtual reality images.

The optical module of the embodiment of the application introduces a free-form surface prism 30 into the optical path, and the introduction of the free-form surface prism 30 can perform multiple times of turning on the incident virtual imaging light (namely, the first light 02 shown in fig. 1) without increasing the number of lenses or optical films in the optical path, wherein the turning times can reach not less than 3, so that the propagation path of the imaging light can be prolonged, and better imaging quality can be ensured while the thickness of the optical module is reduced.

For example, the thickness (thickness in the direction of the eye axis or the horizontal direction shown in fig. 1) of the optical module of the embodiment of the present application may be less than 15mm. The whole optical module is small in size, and the light and thin design of the optical module can be achieved. Moreover, since the virtual imaging light is turned over in the free-form surface prism 30 for many times, the imaging quality can be improved, and high-definition imaging of the optical module is facilitated.

In the embodiment of the present application, as shown in fig. 1, the second surface 32 of the free-form surface prism 30, that is, the surface close to the human eye 01, is divided into two different regions, and a total reflection film is disposed on the second region 322, so that the first light 02 entering the free-form surface prism 30 can reach a condition of total reflection on the first surface 31 after being reflected by the second region 322 of the second surface 32, so as to be capable of performing total reflection on the first surface 31, and then performing total reflection on the first region 321 on the second surface 32, thereby increasing the number of times of turning the first light 02 in the free-form surface prism 30, and specifically, the number of times of turning can reach three times or more.

According to the optical module provided by the embodiment of the present application, as shown in fig. 1, the light propagation process is as follows:

the first light 02 (i.e., virtual imaging light) emitted from the display screen 40 is transmitted through the first lens 10, transmitted through the first surface 31 of the free-form surface prism 30, reflected through the second region 322 of the second surface 32, totally reflected through the first surface 31, totally reflected through the first region 321 of the second surface 32, reflected through the third surface 33, transmitted through the first region 321, and then enters the human eye 01; the second light ray 03 (i.e., the real world light ray) also enters the human eye 01 after being transmitted through the second lens 20 and the freeform prism 30. In this way, the image of the virtual world and the scene of the real world can be organically merged together, and a high-definition picture can be formed in the human eye 01.

As shown in fig. 1, in the optical module according to the embodiment of the present invention, the first lens 10, the second lens 20 and the free-form surface prism 30 are not arranged on the same optical axis in a predetermined order, but the first lens 10 and the second lens 20 are respectively disposed on two optical surfaces close to the free-form surface prism 30.

According to the embodiment of the application, the optical module can be applied to AR equipment, for example, a free-form surface prism 30 with three optical surfaces is introduced into an optical path, and light rays of a virtual optical path are reflected for multiple times in the free-form surface prism 30, so that the purpose of prolonging the light ray propagation path can be achieved, the thickness of the optical module can be reduced, and meanwhile the imaging quality of the optical module can be guaranteed. The optical module has the characteristics of small size and high resolution.

In some examples of the present application, as shown in fig. 1, the optical module further includes a polarization reflective element located between the freeform prism 30 and the second lens 20.

In the embodiment of the present application, a polarization reflective film is disposed between the free-form surface prism 30 and the second lens 20, and the light efficiency of the virtual light path can be improved by introducing the polarization reflective film, so that the imaging quality can be improved. Wherein, can improve the light efficiency of virtual light path because: the first light 02 of the virtual light path can be reflected (or totally reflected) on the third surface 33 of the free-form surface prism 30 as much as possible and then transmitted into the human eye 01 through the first region 321, so that the influence of the first light 02 on the imaging effect due to a large amount of light passing through the third surface 33 after being incident on the third surface 33 is avoided.

Note that a polarizing reflective film may be attached to the third surface 33 of the free-form surface prism 30. The polarizing reflective film may also be used as a separate optical device, and may be supported at a suitable position between the third surface 33 of the freeform prism 30 and the second lens 20 by a transparent flat plate element, for example, which is not limited in the embodiment of the present application.

In some examples of the present application, as shown in fig. 1, the surface of the second lens 20 close to the free-form surface prism 30 and the surface of the third surface 33 are the same in surface type, both are free-form surfaces, and are adhesively connected.

In the optical module of the present embodiment, the free-form surface prism 30 includes three optical surfaces, i.e., the first surface 31, the second surface 32, and the third surface 33. Wherein the second surface 32 is independently located on a side adjacent to the human eye 01. The first surface 31 is adjacent to the first lens 10 and cooperates with the display screen 40 to form a virtual light path. The third surface 33 is close to the second lens 20, and the second lens 20 is transparent to real world light (second light 03).

The surface of the second lens element 20 close to the third surface 33 is designed to be the same as the surface of the third surface 33, and both surfaces are free-form surfaces, which is beneficial to improving the imaging definition of the optical module. Moreover, the surface types of the two surfaces are the same, and the gluing connection of the two surfaces is also facilitated.

The surface of the second lens 20 close to the free-form surface prism 30 and the third surface 33 of the free-form surface prism 30 can be glued together by optical glue, for example, so that the second lens 20 and the free-form surface prism 30 form a glued lens group, and the design can reduce chromatic aberration of an optical module. Moreover, the assembly difficulty of the optical module is reduced.

Optionally, as shown in fig. 1, a polarizing reflective film is disposed on a surface of the second lens 20 close to the free-form surface prism 30.

The light effect of the virtual light path can be improved by introducing the polarization reflection film, the imaging quality is improved, and in the example, the polarization reflection film is clamped between the two surfaces of the second lens 20 and the free-form surface prism 30, and the assembly difficulty of the optical film can be reduced by the arrangement mode.

In addition, since the surface of the second lens 20 close to the free-form surface prism 30 is a free-form surface, when the polarization reflection film is provided thereon, the polarization reflection film may be bonded to the surface of the second lens 20 by means of plating, for example, so that the bonding fastness is high. Of course, optical adhesive can also be used, which is not limited in the embodiments of the present application.

The second lens 20 is configured to transmit the second light ray 03, where the second light ray 03 is a real-world light ray; the surface of the second lens 20 far away from the free-form surface prism is provided with an antireflection film.

Alternatively, the surface of the second lens 20 away from the free-form surface prism 30 may be designed to be flat, which facilitates the flat mounting of an anti-reflection film or other types of optical film thereon.

Of course, the surface of the second lens 20 away from the freeform prism 30 may also be non-planar, which is not limited in this application.

In some examples of the present application, as shown in fig. 1, the optical module further includes a display screen 40, the display screen 40 being located on a side of the first lens 10 facing away from the first surface 31; the display screen 40 is configured to emit the first light 02, and the first light 02 passes through the first lens 10 and the first surface 31, is reflected by the second region 322, is totally reflected by the first surface 31, is totally reflected by the first region 321, is reflected by the third surface 33, and enters the human eye 01 after being transmitted by the first region 321.

In the practice of the present application, the display screen 40 may be configured to emit linearly polarized light or circularly polarized light. It should be noted that the light incident on the first lens 10 should be linearly polarized light.

Optionally, the light emergent surface of the display screen 40 is provided with a screen protection sheet 41, which is made of glass, for example. The first light 02 emitted from the display screen 40 is transmitted through the screen protection sheet 41 on the surface and then enters the first lens 10. The first light 02 (i.e., the virtual imaging light) is transmitted through the first lens 10, transmitted through the first surface 31 of the freeform prism 30, reflected through the second region 322 of the second surface 32, totally reflected through the first surface 31, totally reflected through the first region 321 of the second surface 32, reflected through the third surface 33, transmitted through the first region 321, and enters the human eye 01. It can be seen that the first light ray 02 is incident into the freeform prism 30 and undergoes at least three reflections, so that the propagation path of the light ray can be extended.

In some examples of the present application, as shown in fig. 1, the display screen 40 is disposed along a first direction, and the display screen 40 forms an angle of-30 ° to +30 ° with the first direction; the first direction is perpendicular to the thickness direction of the optical module.

As shown in fig. 1, the thickness direction of the optical module is the horizontal direction shown in fig. 1, and may be referred to as the longitudinal direction of the optical module. The optical module of this application embodiment, its thickness size is less, can be less than 15mm.

In the embodiment of the present application, as shown in fig. 1, the display screen 40 is located on the side of the first lens 10 away from the first surface 31 of the free-form surface prism 30, and the display screen 40 is disposed in an inclined manner in the thickness direction perpendicular to the whole optical module, and the inclined range is from-30 ° to +30 ° as described above, this design is adopted because: both surfaces of the first lens 10 are free-form surfaces, and the display screen 40 is obliquely disposed in the above-described manner, so that the first light 02 emitted from the display screen 40 can satisfy a condition for total reflection when it strikes the first surface 31 of the free-form surface prism 30, and thus total reflection can occur on the first surface 31. And the number of times of reflection of the first light ray 02 in the free-form surface prism 30 can be increased.

In some examples of the present application, the first region 321 is provided with an antireflection film; the ratio of the length of the second region 322 to the length of the first region 321 is 0.9-3.

In the embodiment of the present application, the free-form surface prism 30 is designed to include three optical surfaces, wherein the second surface 32 is a surface close to the human eye 01, and two different optical film layers are attached to the second surface 32 in different areas, respectively: an anti-reflection film disposed in the first region 321 and a total reflection film disposed in the second region 322. After the first light 02 of the virtual light path is incident to the second surface 32 for reflection, the first surface 31 of the free-form surface prism 30 can be totally reflected, so that the light propagation path of the virtual light path can be increased, and the resolution of the optical module can be improved while the thickness of the optical module is reduced. The second real world ray 03 may be transmitted as completely as possible through the first region of the second surface 32. Therefore, a high-definition virtual reality picture is finally presented in the human eyes 01, and the watching experience of a user can be improved.

It should be noted that, on the second surface 32 of the freeform surface prism 30, when the length ratio of the second area 322 to the first area 321 is 0.9 to 3, all the first light 02 emitted from the display screen 40 can be totally reflected on the first surface 31. The length direction of the first region 321 and the second region 322 may be a direction perpendicular to the thickness direction of the optical module (or a horizontal direction) as shown in fig. 1.

In some examples of the present application, as shown in fig. 1, the first lens 10 includes two surfaces, and both surfaces of the first lens 10 are free-form surfaces.

In the optical module of the embodiment of the present application, the lens with the free-form surface type is disposed on one side of the first surface 31 of the free-form surface prism 30, that is, the first lens 10, so that high-definition imaging of the optical module can be achieved.

In whole optical module, through the use of a plurality of free curved surfaces, can increase the degree of freedom of optical module design, can effectual improvement optical module's imaging quality.

Optionally, an antireflection film is attached to at least one of the two surfaces of the first lens 10.

For example, both surfaces of the first lens 10 are free-form surfaces, and antireflection films are attached to both surfaces.

In some examples of the present application, the free-form surface prism 30 has a thickness T ₃ ，T ₃ Satisfies the following conditions: t is more than 0.5mm ₃ ＜15mm。

The thickness of the free-form surface prism 30 at different positions is different, and within the thickness range, the imaging quality of the optical module can be ensured, and the thickness and the weight of the whole optical module cannot be influenced.

Optionally, the thickness of the first lens 10 is T ₁ ，T ₁ Satisfies the following conditions: t is more than 1mm ₁ Less than 10mm; the second lens 20 has a thickness T ₂ ，T ₂ Satisfies the following conditions: t is more than 0.5mm ₂ Less than 15mm. First lens 10 and second lens 20 both have free curved surface, and the thickness of different positions is different on it, and the thickness scope of first lens 10 and second lens 20 does benefit to the volume and the weight that reduce optical module in this application, simultaneously with free curved surface prism 30 cooperation that can be fine, promote imaging quality.

In some examples of the present application, at least one of the free-form surface prism 30, the first lens 10, and the second lens 20 is made of a plastic material. Each lens in the optical module is made of plastic materials, so that the weight of the optical module can be effectively reduced.

The second lens element 20 and the free-form surface prism 30 are glued together, and the two elements may be made of the same material, for example, so as to reduce chromatic aberration and aberration.

Optionally, the refractive indexes n of the first lens 10, the second lens 20, and the free-form surface prism 30 are: n is more than 1.45 and less than 1.70; the first lens 10, the second lens 20, and the free-form surface prism 30 have an abbe number v: v is more than 20 and less than 70. The refractive index and the dispersion coefficient of the two lenses are adjusted to be matched, so that the imaging quality of the optical module can be improved.

Examples

As shown in fig. 1, the optical module includes a first lens 10, a second lens 20 and a free-form surface prism 30, and the three lenses are made of plastic materials;

the free-form surface prism 30 includes a first surface 31, a second surface 32 and a third surface 33, both the first surface 31 and the third surface 33 are free-form surfaces, the second surface 32 includes a first region 321 and a second region 322, an anti-reflection film is disposed in the first region 321, and a total reflection film is disposed in the second region 322; that is, different optical films are provided on the second surface 32 in two regions;

the first lens 10 is located on one side of the first surface 31, a first light ray 02 is transmitted by the first lens 10 and then enters the free-form surface prism 30, the first light ray is reflected by the second area 322 and then is totally reflected on the first surface 31, and the number of times of the first light ray is more than or equal to 3 in the free-form surface prism 30; the second lens 20 is located at one side of the third surface 33, and the second light 03 is transmitted by the second lens 20, enters the freeform prism 30, and exits through the first region 321.

The optical parameters of the first lens 10 and the free-form surface prism 30 may be as shown in tables 1 to 7, where 11 denotes a surface of the first lens 10 away from the free-

form surface prism

30, 12 denotes a surface of the first lens 10 close to the free-

form surface prism

30, 31 denotes a first surface of the free-form surface prism 30, and 33 denotes a third surface of the free-form surface prism 30.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

A19

A20

A21

A22

A23

A24

A25

A26

0.00E+00

3.47E-12

0.00E+00

1.16E-05

-7.08E-06

0.00E+00

1.55E-05

0.00E+00

-2.01E+03

0.00E+00

4.26E+03

0.00E+00

TABLE 5

A27

A28

A29

A30

A31

A32

A33

A34

0.00E+00

-1.13E-08

0.00E+00

-1.30E-10

0.00E+00

TABLE 6

TABLE 7

A40	A41	A42	A43	A44
					0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00
0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00
					-8.13E-10	0.00E+00	0.00E+00	0.00E+00	0.00E+00
0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00

The optical module provided in the above embodiments can be as shown in fig. 2 to 5:

fig. 2 is an MTF graph of an optical module according to an embodiment of the present disclosure, fig. 3 is a schematic diagram of a dot-column diagram of an optical module according to an embodiment of the present disclosure, fig. 4 is a diagram of a field curvature distortion according to an embodiment of the present disclosure, and fig. 5 is a diagram of a vertical axis chromatic aberration according to an embodiment of the present disclosure.

The MTF graph is a modulation transfer function graph, and the imaging definition of the optical module is represented by the contrast of black and white line pairs. As shown in FIG. 2, the MTF in this example is >0.3 at 38lp/mm, imaging is clear.

The point diagram refers to that after a plurality of light rays emitted by one point pass through the optical module, the intersection points of the light rays and the image surface are not concentrated on the same point any more due to aberration, and a dispersion pattern scattered in a certain range is formed and can be used for evaluating the imaging quality of the optical module. As shown in fig. 3, in the present embodiment, the maximum value of the image point in the dot array image is less than 11 μm, and the image is clearly imaged.

The field curvature distortion map reflects the image plane position difference of clear images formed by different fields, and in this embodiment, as shown in fig. 4, the maximum value of field curvature is less than 0.4mm, and the maximum value of distortion reflects the deformation condition of the images, and is less than 20% (absolute value).

The vertical axis chromatic aberration is also called as magnification chromatic aberration, and mainly refers to the difference of focal positions of blue light and red light on an image plane, wherein a compound-color main light ray of an object side is changed into a plurality of light rays when the light rays exit from an image side due to chromatic dispersion of a refraction system. In embodiment 1, as shown in fig. 5, the maximum color difference value of the optical module is less than 130 μm.

According to another aspect of the embodiments of the present application, there is also provided a head-mounted display device, which includes a housing and the optical module as described above.

The head-mounted display device is, for example, an AR head-mounted device, including AR glasses or an AR helmet, and the like, which is not limited in this application embodiment.

The specific implementation of the head-mounted display device in the embodiment of the present application may refer to each of the embodiments of the optical module, so that at least all the beneficial effects brought by the technical solutions of the embodiments are achieved, and are not described in detail herein.

In the above embodiments, the differences between the embodiments are described in emphasis, and different optimization features between the embodiments can be combined to form a better embodiment as long as the differences are not contradictory, and further description is omitted here in consideration of brevity of the text.

Although some specific embodiments of the present application have been described in detail by way of illustration, it should be understood by those skilled in the art that the above illustration is only for purposes of illustration and is not intended to limit the scope of the present application. It will be appreciated by those skilled in the art that modifications can be made to the above embodiments without departing from the scope and spirit of the present application. The scope of the application is defined by the appended claims.

Claims

1. An optical module, comprising:

a free-form surface prism (30), the free-form surface prism (30) including a first surface (31), a second surface (32), and a third surface (33), the first surface (31) and the third surface (33) both being free-form surfaces, the second surface (32) including a first region (321) and a second region (322), wherein the second region (322) is provided with a total reflection film;

the first lens (10) is positioned on one side of the first surface (31), first light rays (02) are transmitted by the first lens (10) and then enter the free-form surface prism (30), the first light rays are reflected by the second area (322) and then are totally reflected on the first surface (31), and the number of times of the first light rays are refracted in the free-form surface prism (30) is not less than 3; and

and the second lens (20), the second lens (20) is positioned on one side of the third surface (33), and the second light rays (03) are transmitted through the second lens (20), then enter the free-form surface prism (30) and exit through the first area (321).

2. The optical module of claim 1 further comprising a polarizing reflective element located between the freeform prism (30) and the second lens (20).

3. The optical module according to claim 1, wherein the surface of the second lens (20) close to the free-form surface prism (30) and the third surface (33) are both free-form surfaces and are adhesively bonded.

4. An optical module according to claim 3, characterised in that the surface of the second lens (20) adjacent to the freeform prism (30) is provided with a polarising reflecting element.

5. The optical module according to claim 1, wherein the second lens (20) is configured to transmit the second light ray (03), and the second light ray (03) is a real-world light ray;

the surface of the second lens (20) far away from the free-form surface prism (30) is provided with an antireflection film.

6. Optical module according to any one of claims 1 to 5, further comprising a display screen (40), the display screen (40) being located on a side of the first lens (10) facing away from the first surface (31);

the display screen (40) is used for emitting the first light (02), and the first light (02) is transmitted through the first lens (10) and the first surface (31), reflected through the second area (322), totally reflected through the first surface (31), totally reflected through the first area (321), reflected through the third surface (33), transmitted through the first area (321), and enters the human eye (01).

7. The optical module according to claim 6, wherein the display screen (40) is arranged in a first direction, the display screen (40) being angled from-30 ° to +30 ° from the first direction;

8. An optical module according to claim 1, characterized in that the first region (321) is provided with an anti-reflection film;

the length ratio of the second region (322) to the first region (321) is 0.9-3.

9. The optical module according to claim 1, characterized in that the first lens (10) comprises two surfaces, both surfaces of the first lens (10) being free-form surfaces.

10. An optical module according to claim 9, characterised in that an antireflection film is applied to at least one of the two surfaces of the first lens (10).

11. The optical module of claim 1, wherein the free-form surface prism (30) has a thickness T ₃ ，T ₃ Satisfies the following conditions: t is more than 0.5mm ₃ ＜15mm。

12. Optical module according to claim 1, in which the first lens (10) has a thickness T ₁ ，T ₁ Satisfies the following conditions: t is more than 1mm ₃ ＜10mm；

The second lens (20) has a thickness T ₂ ，T ₂ Satisfies the following conditions: t is more than 0.5mm ₂ ＜15mm。

13. The optical module according to claim 1, wherein at least one of the free-form surface prism (30), the first lens (10) and the second lens (20) is made of a plastic material.

14. A head-mounted display device, comprising:

a housing; and

the optical module of any one of claims 1-13.