Optical path structure, optical display system, virtual reality equipment and focal power adjusting method

Abstract

The invention provides an optical path structure, an optical display system, virtual reality equipment and a focal power adjusting method, and the optical path structure comprises a first lens group, a second lens group and a third lens group which are sequentially arranged, the ratio of the total focal length of the first lens group and the second lens group to the absolute value of the focal length of the third lens group is greater than 0.1 and less than 6; one side, far away from the third lens group, of the second lens group is sequentially provided with a phase retarder and a reflective polarizer along the direction pointing to the first lens group; and a light splitting film is arranged on one optical surface of the second lens group. By adopting the light path structure provided by the invention, the light and thin effects of the whole light path structure can be realized; and by setting the focal length size relationship between different lens groups, high-resolution images under a large field angle can be realized.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to an optical path structure, an optical display system, a virtual reality device and a focal adjustment method. Background Art

[0002] Virtual reality technology is a high-tech technology that integrates modern science and technology such as simulation technology, sensor technology, display technology, and computer technology. Using computer image technology, we can simulate real objects and turn things imagined out of thin air into lifelike audio-visual works that can be seen and heard. For example, we can simulate the entire universe and let people travel in it; we can also simulate things that exist objectively but cannot be felt or touched by ordinary people, such as everything that happens in the atomic world. What is very rare is that the environment simulated by virtual reality technology is not "dead", but will present different scenes according to different reactions of people.

[0003] At present, VR (Virtual Reality) optical systems in related technologies generally have the problem of poor image quality, which leads to insufficient clarity of virtual images of VR devices. Figure 1 The MTF (Modulation Transfer Function, which uses the concept of contrast to test the sharpness of the lens) curve of VR optical display devices in related technologies cuts off at around 8lp / mm. The horizontal axis is the spatial frequency and the vertical axis is the OTF (Optical Transfer Function) modulus. It can only adapt to display screens with a pixel size of about 50 to 60 microns. The image resolution is low and cannot provide high-definition images.

[0004] Therefore, a new optical path structure is needed to improve the resolution. Summary of the invention

[0005] The main purpose of the present invention is to provide an optical path structure, an optical display system, a virtual reality device and a focal adjustment method to improve the clarity of the VR optical system.

[0006] The present invention provides an optical path structure, comprising: a first lens group, a second lens group and a third lens group arranged in sequence, wherein the ratio of the absolute value of the total focal length of the first lens group and the second lens group to the focal length of the third lens group is greater than 0.1 and less than 6; a phase delay plate and a reflective polarizer are sequentially arranged on a side of the second lens group away from the third lens group in a direction pointing to the first lens group; and a beam splitting film is arranged on an optical surface of the second lens group.

[0007] In one embodiment, the first lens group includes at least one aspherical lens; and / or the second lens group includes at least one aspherical lens; and / or the third lens group includes at least one Fresnel lens.

[0008] In one embodiment, the first lens group includes a first aspheric lens, the second lens group includes a second aspheric lens, and the third lens group includes a first Fresnel lens; wherein the optical surface of the first aspheric lens facing the second aspheric lens is convex in the direction of the second aspheric lens, the optical surface of the first aspheric lens away from the second aspheric lens is a plane, two opposite optical surfaces of the second aspheric lens are convex toward each other, the optical surface of the first Fresnel lens facing the second aspheric lens is a convex aspheric surface in the direction of the second aspheric lens, and the optical surface of the first Fresnel lens away from the second aspheric lens is a Fresnel surface.

[0009] In one embodiment, the absolute value of the focal length of the first aspheric lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the first aspheric lens facing the second aspheric lens is 1 mm to 10 mm; and / or the absolute value of the focal length of the second aspheric lens is 5 mm to 200 mm; and / or, the absolute value of the sagitta of the optical surface of the second aspheric lens facing the first aspheric lens is 1 mm to 10 mm, and the absolute value of the sagitta of the optical surface of the second aspheric lens facing the first Fresnel lens is 1 mm to 10 mm; and / or the absolute value of the focal length of the first Fresnel lens is 5 mm to 200 mm; and / or, the absolute value of the sagitta of the optical surface of the first Fresnel lens facing the second aspheric lens is 1 mm to 15 mm, and the maximum absolute value of the sagitta of the optical surface of the first Fresnel lens away from the second aspheric lens is 0 mm to 10 mm.

[0010] In one embodiment, the first lens group includes a third aspheric lens, the second lens group includes a fourth aspheric lens, and the third lens group includes a second Fresnel lens; wherein the optical surface of the third aspheric lens facing the fourth aspheric lens is a plane, the optical surface of the third aspheric lens away from the fourth aspheric lens is convex in a direction away from the fourth aspheric lens, two opposite optical surfaces of the fourth aspheric lens are convex in directions away from each other, the optical surface of the second Fresnel lens facing the fourth aspheric lens is convex in a direction away from the fourth aspheric lens, and the optical surface of the second Fresnel lens away from the fourth aspheric lens is convex in a direction away from the fourth aspheric lens.

[0011] In one embodiment, the absolute value of the focal length of the third aspheric lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the third aspheric lens away from the fourth aspheric lens is 0.5 mm to 10 mm; and / or the absolute value of the focal length of the fourth aspheric lens is 10 mm to 400 mm; and / or, the absolute value of the sagitta of the optical surface of the fourth aspheric lens facing the third aspheric lens is 0.5 mm to 15 mm, and the absolute value of the sagitta of the optical surface of the fourth aspheric lens facing the second Fresnel lens is 0.5 mm to 15 mm; and / or the absolute value of the focal length of the second Fresnel lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the second Fresnel lens facing the fourth aspheric lens is 1 mm to 15 mm, and the absolute value of the sagitta of the optical surface of the second Fresnel lens away from the fourth aspheric lens is 1 mm to 15 mm.

[0012] In one embodiment, at least one optical surface of the third lens group is a Fresnel surface.

[0013] In one embodiment, an optical surface of the third lens group is a Fresnel surface, and another optical surface of the third lens group opposite to the Fresnel surface is an aspherical surface.

[0014] In one embodiment, at least one circle of thread protrusions on the Fresnel surface is an aspherical surface.

[0015] In one embodiment, an absorbing polarizer is disposed on a side of the reflective polarizer away from the phase retarder.

[0016] In one embodiment, an anti-reflection film is disposed on an optical surface of the second lens group at a side away from the beam-splitting film.

[0017] In one embodiment, a ratio of an absolute value of a focal length of the first lens group to an absolute value of a focal length of the second lens group is greater than 0.1 and less than 6.

[0018] The present invention provides an optical display system, comprising: the above-mentioned optical path structure; and a display panel, which is arranged on a side of the third lens group away from the second lens group.

[0019] The present invention provides a virtual reality device, comprising the above-mentioned optical display system.

[0020] The present invention provides a focal length adjustment method, based on the above-mentioned optical display system, comprising: adjusting the focal length of the optical display system by adjusting the distance between the second lens group and the first lens group and / or the display panel, and / or by adjusting the distance between the third lens group and the first lens group and / or the display panel, without increasing the distance between the first lens group and the display panel.

[0021] In the present invention, a folded optical path is used to process light, and multiple lens groups are used to share the refractive index of the light, so that each lens group can be thinner and lighter, which is beneficial to achieving the thinness of the entire optical path structure; by setting the focal length relationship between different lens groups, it is beneficial to achieve high-resolution images under a large field of view. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute a part of the present application, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0023] In the figure:

[0024] Figure 1 is the MTF curve of the VR optical display system in the related art;

[0025] Figure 2 is a schematic structural diagram of an optical display system according to an embodiment of the present application;

[0026] Figure 3 is a schematic structural diagram of an optical display system according to an embodiment of the present application;

[0027] Figure 4 is an MTF curve diagram of an optical display system according to an embodiment of the present application;

[0028] Figure 5 is a schematic structural diagram of an optical display system according to another embodiment of the present application;

[0029] Figure 6 FIG. 4 is a MTF curve diagram of an optical display system according to another embodiment of the present application. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] refer to Figure 2 This embodiment provides an optical path structure, which may include: a first lens group 11, a second lens group 12, and a third lens group 13 arranged in sequence, wherein the ratio of the absolute value of the total focal length of the first lens group 11 and the second lens group 12 to the focal length of the third lens group 13 is greater than 0.1 and less than 6; a phase delay plate and a reflective polarizer (not shown in the figure) are sequentially arranged on a side of the second lens group 12 away from the third lens group 13 along a direction pointing to the first lens group 11; and a dichroic film (not shown in the figure) is arranged on an optical surface of the second lens group 12.

[0032] In this embodiment, the first lens group, the second lens group and the third lens group may respectively include at least one convex lens, a concave lens or a Fresnel lens, and the material of each lens may be selected from glass, resin, plastic, etc. The working principle of the optical path structure of this embodiment is that circularly polarized light can be incident from the side of the third lens group away from the second lens group, and after being split by the beam splitter film, part of the circularly polarized light becomes the first polarized light after passing through the phase delay plate, the first polarized light is reflected at the reflective polarizer, and becomes circularly polarized light after passing through the phase delay plate again, and then the beam splitter film reflects part of the circularly polarized light, and the reflected circularly polarized light becomes the second polarized light after passing through the phase delay plate, and the second polarized light can be emitted through the reflective polarizer for imaging. If the first polarized light is S polarized light, the second polarized light is P polarized light; if the first polarized light is P polarized light, the second polarized light is S polarized light.

[0033] The phase retarder and the reflective polarizer may be located on both sides of the third lens group or on the same side of the third lens group, which is not specifically limited in this application. In other embodiments, more film layers may be included, and those skilled in the art may set them as needed, which is not specifically limited in this application.

[0034] For example, the ratio of the absolute value of the total focal length of the first lens group and the second lens group to the focal length of the third lens group can be 0.2, 0.25, 3, 4, 4.5, etc. Those skilled in the art can set it as needed, and this application does not make any specific limitation on this.

[0035] In one embodiment, the ratio of the total focal length of the first lens group 11 and the second lens group 12 to the absolute value of the focal length of the third lens group 13 is greater than 0.15 and less than 5. In this embodiment, by further setting the focal length relationship between different lens groups, it is beneficial to achieve high-resolution images at a large field of view.

[0036] In this embodiment, a folded optical path is used to process the light, and multiple lens groups are used to share the refractive index of the light. Each lens group can be thinner and lighter, which is beneficial to achieving a thinner structure of the entire optical path. By constraining the focal length relationship between different lens groups, it is beneficial to achieve high-resolution images with a large field of view.

[0037] In one embodiment, the first lens group may include at least one aspherical lens; and / or the second lens group may include at least one aspherical lens; and / or the third lens group may include at least one Fresnel lens.

[0038] In this embodiment, compared with a spherical lens, an aspherical lens can correct aberrations of the vertical optical axis such as coma and astigmatism that affect the imaging quality, improve the imaging quality, and can increase the transmittance and expand the field of view. At the same time, the aspherical lens occupies less space, which is conducive to further reducing the thickness of the optical path structure.

[0039] In one embodiment, reference Figure 3 The first lens group may include a first aspheric lens 21, the second lens group includes a second aspheric lens 22, and the third lens group includes a first Fresnel lens 23; wherein, the optical surface of the first aspheric lens 21 facing the second aspheric lens 22 is convex toward the second aspheric lens 22, the optical surface of the first aspheric lens 21 away from the second aspheric lens 22 is a plane, the two opposite optical surfaces of the second aspheric lens 22 are convex toward each other, the optical surface of the first Fresnel lens 23 facing the second aspheric lens 22 is a non-spherical surface convex toward the second aspheric lens 22, and the optical surface of the first Fresnel lens 23 away from the second aspheric lens 22 is a Fresnel surface.

[0040] In this embodiment, the shapes of the optical surfaces of the first aspheric lens and the second aspheric lens fit each other, and the shapes of the optical surfaces of the second aspheric lens and the first Fresnel lens fit each other, which can reduce the distance between adjacent lens groups and make the thickness of the entire optical path structure smaller.

[0041] In one embodiment, the absolute value of the focal length of the first aspheric lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the first aspheric lens facing the second aspheric lens is 1 mm to 10 mm; and / or, the absolute value of the focal length of the second aspheric lens is 5 mm to 200 mm; and / or, the absolute value of the sagitta of the optical surface of the second aspheric lens facing the first aspheric lens is 1 mm to 10 mm, and the absolute value of the sagitta of the optical surface of the second aspheric lens facing the first Fresnel lens is 1 mm to 10 mm; and / or, the absolute value of the focal length of the first Fresnel lens is 5 mm to 200 mm; and / or, the absolute value of the sagitta of the optical surface of the first Fresnel lens facing the second aspheric lens is 1 mm to 15 mm, and the maximum absolute value of the sagitta of the optical surface of the first Fresnel lens away from the second aspheric lens is 0 mm to 10 mm.

[0042] For example, the focal length of the first aspheric lens is 10 mm, the focal length of the second aspheric lens is 30 mm, and the focal length of the first Fresnel lens is 50 mm. In other examples, the focal lengths of the first aspheric lens, the second aspheric lens, and the first Fresnel lens may also be other values, which are not specifically limited in this application.

[0043] The sag heights of the optical surfaces of the first aspheric lens, the second aspheric lens, and the first Fresnel lens can be specifically set as needed based on the focal length, and the present application does not make any specific limitation thereto.

[0044] In one embodiment, reference Figure 5 The first lens group may include a third aspheric lens 31, the second lens group includes a fourth aspheric lens 32, and the third lens group includes a second Fresnel lens 33; wherein the optical surface of the third aspheric lens 31 facing the fourth aspheric lens 32 is a plane, the optical surface of the third aspheric lens 31 away from the fourth aspheric lens 32 convexes in a direction away from the fourth aspheric lens 32, the two opposite optical surfaces of the fourth aspheric lens 32 convex in directions away from each other, the optical surface of the second Fresnel lens 33 facing the fourth aspheric lens 32 convexes in a direction away from the fourth aspheric lens 32, and the optical surface of the second Fresnel lens 33 away from the fourth aspheric lens 32 convexes in a direction away from the fourth aspheric lens 32.

[0045] In this embodiment, the shapes of the optical surfaces of the fourth aspherical lens and the second Fresnel lens fit each other, which can reduce the distance between adjacent lens groups and make the thickness of the entire optical path structure smaller.

[0046] In one embodiment, the absolute value of the focal length of the third aspheric lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the third aspheric lens away from the fourth aspheric lens is 0.5 mm to 10 mm; and / or, the absolute value of the focal length of the fourth aspheric lens is 10 mm to 400 mm; and / or, the absolute value of the sagitta of the optical surface of the fourth aspheric lens facing the third aspheric lens is 0.5 mm to 15 mm, and the absolute value of the sagitta of the optical surface of the fourth aspheric lens facing the second Fresnel lens is 0.5 mm to 15 mm; and / or, the absolute value of the focal length of the second Fresnel lens is 10 mm to 500 mm; and / or, the absolute value of the sagitta of the optical surface of the second Fresnel lens facing the fourth aspheric lens is 1 mm to 15 mm, and the absolute value of the sagitta of the optical surface of the second Fresnel lens away from the fourth aspheric lens is 1 mm to 15 mm.

[0047] For example, the focal length of the third aspheric lens is 20 mm, the focal length of the fourth aspheric lens is 100 mm, and the focal length of the second Fresnel lens is 400 mm. In other examples, the focal lengths of the third aspheric lens, the fourth aspheric lens, and the second Fresnel lens may also be other values, which are not specifically limited in this application.

[0048] The sagittal heights of the optical surfaces of the third aspherical lens, the fourth aspherical lens, and the second Fresnel lens can be specifically set as needed based on the focal length, and the present application does not make any specific limitation thereto.

[0049] In one embodiment, at least one optical surface of the third lens group may be a Fresnel surface.

[0050] In this embodiment, by providing a Fresnel surface in the third lens group, the light can be adjusted by passing through the Fresnel surface earlier, so that the imaging of the optical path structure is brighter and more uniform.

[0051] In one embodiment, an optical surface of the third lens group may be a Fresnel surface, and another optical surface of the third lens group opposite to the Fresnel surface may be an aspherical surface.

[0052] In this embodiment, the light is processed by combining the Fresnel surface with the aspherical surface, which is beneficial to improving the imaging quality and making the formed virtual image brighter and more uniform.

[0053] In one embodiment, at least one circle of thread protrusions on the Fresnel surface may be an aspherical surface.

[0054] In this embodiment, by setting the threaded protrusion of the Fresnel surface as an aspherical surface, it is beneficial to reduce the thickness of the third lens group and improve the imaging quality.

[0055] In one embodiment, an absorbing polarizer may be disposed on a side of the reflective polarizer away from the phase retarder.

[0056] In this embodiment, the side of the reflective polarizer far away from the phase retarder may be the emitting direction of the light. By arranging the absorbing polarizer in the emitting direction of the light, it is helpful to improve the imaging quality.

[0057] In one embodiment, an anti-reflection film may be disposed on an optical surface of the second lens group at a side away from the beam-splitting film.

[0058] In this embodiment, the anti-reflection film is provided to improve light transmittance and reduce light loss.

[0059] In one embodiment, a ratio of an absolute value of a focal length of the first lens group to an absolute value of a focal length of the second lens group may be greater than 0.1 and less than 6.

[0060] For example, the ratio of the absolute value of the focal length of the first lens group to the focal length of the second lens group can be 0.2, 0.45, 2, 2.1, 3, 4.2, etc., and those skilled in the art can set it as needed, and this application does not make any specific limitation on this.

[0061] In one embodiment, a ratio of an absolute value of a focal length of the first lens group to an absolute value of a focal length of the second lens group is greater than 0.15 and less than 5.

[0062] For example, the ratio of the absolute value of the focal length of the first lens group to the focal length of the second lens group can be 0.13, 1.5, 1.8, 3.9, 4.5, etc., and those skilled in the art can set it as needed, and this application does not make any specific limitation on this.

[0063] In this embodiment, by setting the focal length relationship between different lens groups, it is beneficial to achieve high-resolution images with a large field of view.

[0064] refer to Figure 2 This embodiment provides an optical display system, including: the above-mentioned optical path structure; a display panel 14, which is arranged on a side of the third lens group 13 away from the second lens group 12.

[0065] The relevant implementation methods of the optical path structure may refer to the aforementioned embodiments.

[0066] In this embodiment, the display panel may be a high PPI (Pixels Per Inch) display panel, for example, a 4K display panel. The display panel may be any one of an LCD (Liquid Crystal Display), an OLED (Organic Light-Emitting Diode), a Micro OLED display panel, a Mini LED display panel, or a DLP (Digital Light Processing) display panel, an LCOS (Liquid Crystal on Silicon) display panel, and the like. The display panel may be flexible or rigid, and those skilled in the art may select as needed.

[0067] The optical display system of this embodiment has higher resolution, larger field of view, and is thin and light in size. The optical display system of this embodiment can also adjust the diopter of the optical display system by adjusting the internal structure of the optical path without changing the object distance or adding peripherals.

[0068] refer to Figure 3, a specific embodiment of an optical display system is provided, comprising a first aspheric lens 21, a second aspheric lens 22, a first Fresnel lens 23 and a display panel 24 arranged in sequence. The optical surface of the first Fresnel lens 23 facing the display panel 24 is a Fresnel surface, and the optical surface away from the display panel 24 is an aspheric surface; the second aspheric lens 22 is a double-sided concave lens, the optical surface of the first aspheric lens 21 facing the second aspheric lens 22 is convex toward the second aspheric lens 22, and the optical surface of the first aspheric lens 21 away from the second aspheric lens 22 is a plane.

[0069] In addition, Figure 3 What is not shown is that an absorption polarizer is also arranged on the optical surface of the first aspheric lens away from the second aspheric lens, a reflection polarizer and a quarter wave plate are arranged on the optical surface of the first aspheric lens facing the second aspheric lens, and a dichroic film and an anti-reflection film are respectively arranged on the two optical surfaces of the second aspheric lens.

[0070] refer to Figure 4 , to characterize Figure 3 The MTF curve of the resolution capability of the optical display system shown in the figure shows that at 80lp / mm>0.2, it has extremely high resolution and the maximum field of view can reach 110°.

[0071] refer to Figure 5 , another specific embodiment of an optical display system is provided, comprising a third aspheric lens 31, a fourth aspheric lens 32, a second Fresnel lens 33 and a display panel 34 arranged in sequence. The optical surface of the second Fresnel lens 33 facing and / or away from the display panel 34 is a Fresnel surface, that is, at least one optical surface of the second Fresnel lens 33 is a Fresnel surface; the fourth aspheric lens 32 is a double-sided convex lens, the optical surface of the third aspheric lens 31 away from the fourth aspheric lens 32 is convex in the direction away from the fourth aspheric lens 32, and the optical surface of the third aspheric lens 31 facing the fourth aspheric lens 32 is a plane.

[0072] In addition, Figure 5 What is not shown is that an absorption polarizer is also arranged on the optical surface of the third aspheric lens away from the fourth aspheric lens, a reflection polarizer and a quarter wave plate are arranged on the optical surface of the third aspheric lens facing the fourth aspheric lens, and a dichroic film and an anti-reflection film are respectively arranged on the two optical surfaces of the fourth aspheric lens.

[0073] refer to Figure 6 , to characterize Figure 5 The MTF curve of the resolution capability of the optical display system is shown. It can be seen that at 79lp / mm≥0.2, it has extremely high resolution and the maximum field of view can reach 110°.

[0074] This embodiment provides a virtual reality device, including the above-mentioned optical display system.

[0075] The relevant implementation of the optical display system can refer to the above-mentioned embodiment. The virtual reality device can be VR (Virtual Reality), AR (Augmented Reality), MR (Mixed Reality), etc.

[0076] This embodiment provides a focal adjustment method, referring to Figure 2 , based on the above optical display system, including: when the distance between the first lens group and the display panel does not increase, the focal length of the optical display system is adjusted by adjusting the distance between the second lens group and the first lens group and / or the display panel, and / or by adjusting the distance between the third lens group and the first lens group and / or the display panel.

[0077] In the related art, the diopter adjustment of the optical display system is either achieved by adding a myopic lens outside the lens or adjusting the object distance. The former has poor adaptability, and the latter causes a change in the lens length before and after adjustment, both of which reduce the wearing experience.

[0078] Based on the optical display system of the present application, the focal length of the optical display system can be adjusted by adjusting the second lens group and / or the third lens group, at least without increasing the distance between the first lens group and the display panel. The diopter adjustment can be achieved without changing the object distance or adding peripherals, and without increasing the volume, thereby adapting to more users.

[0079] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. When the terms "include" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0080] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances.

[0081] It should be understood that the exemplary embodiments in this specification can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments described herein. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps. These embodiments are provided to make the disclosure of this application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art, and should not be construed as limitations on the present invention.

[0082] Although the spirit and principle of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the disclosed specific embodiments, and the division of various aspects does not mean that the features in these aspects cannot be combined to benefit, and such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the attached claims.

Claims

1. An optical path structure, characterized in that: include: A first lens group, a second lens group, and a third lens group are arranged in sequence, wherein the ratio of the absolute value of the total focal length of the first lens group and the second lens group to the focal length of the third lens group is greater than 0.1 and less than 6; A phase delay plate and a reflective polarizer are sequentially arranged on a side of the second lens group away from the third lens group in a direction pointing to the first lens group; A beam splitting film is disposed on an optical surface of the second lens group.

2. The optical path structure according to claim 1, characterized in that: The first lens group includes at least one aspherical lens; and / or The second lens group includes at least one aspherical lens; and / or The third lens group includes at least one Fresnel lens.

3. The optical path structure according to claim 2, characterized in that: The first lens group includes a first aspheric lens, the second lens group includes a second aspheric lens, and the third lens group includes a first Fresnel lens; The optical surface of the first aspheric lens facing the second aspheric lens is convex in the direction of the second aspheric lens, the optical surface of the first aspheric lens away from the second aspheric lens is a plane, the two opposite optical surfaces of the second aspheric lens are convex toward each other, the optical surface of the first Fresnel lens facing the second aspheric lens is a aspheric surface convex in the direction of the second aspheric lens, and the optical surface of the first Fresnel lens away from the second aspheric lens is a Fresnel surface.

4. The optical path structure according to claim 3, characterized in that: The absolute value of the focal length of the first aspheric lens is 10 mm to 500 mm; and / or the absolute value of the sagittal height of the optical surface of the first aspheric lens facing the second aspheric lens is 1 mm to 10 mm; and / or The absolute value of the focal length of the second aspheric lens is 5 mm to 200 mm; and / or the absolute value of the sagittal height of the optical surface of the second aspheric lens facing the first aspheric lens is 1 mm to 10 mm, and the absolute value of the sagittal height of the optical surface of the second aspheric lens facing the first Fresnel lens is 1 mm to 10 mm; and / or The absolute value of the focal length of the first Fresnel lens is 5 mm to 200 mm; and / or the absolute value of the sagittal height of the optical surface of the first Fresnel lens facing the second aspheric lens is 1 mm to 15 mm, and the maximum absolute value of the sagittal height of the optical surface of the first Fresnel lens away from the second aspheric lens is 0 mm to 10 mm.

5. The optical path structure according to claim 2, characterized in that: The first lens group includes a third aspheric lens, the second lens group includes a fourth aspheric lens, and the third lens group includes a second Fresnel lens; Among them, the optical surface of the third aspheric lens facing the fourth aspheric lens is a plane, the optical surface of the third aspheric lens away from the fourth aspheric lens convexes in a direction away from the fourth aspheric lens, the two opposite optical surfaces of the fourth aspheric lens convex in a direction away from each other, the optical surface of the second Fresnel lens facing the fourth aspheric lens convexes in a direction away from the fourth aspheric lens, and the optical surface of the second Fresnel lens away from the fourth aspheric lens convexes in a direction away from the fourth aspheric lens.

6. The optical path structure according to claim 5, characterized in that: The absolute value of the focal length of the third aspheric lens is 10 mm to 500 mm; and / or the absolute value of the sagittal height of the optical surface of the third aspheric lens away from the fourth aspheric lens is 0.5 mm to 10 mm; and / or The absolute value of the focal length of the fourth aspheric lens is 10 mm to 400 mm; and / or the absolute value of the sagittal height of the optical surface of the fourth aspheric lens facing the third aspheric lens is 0.5 mm to 15 mm, and the absolute value of the sagittal height of the optical surface of the fourth aspheric lens facing the second Fresnel lens is 0.5 mm to 15 mm; and / or The absolute value of the focal length of the second Fresnel lens is 10 mm to 500 mm; and / or the absolute value of the sagittal height of the optical surface of the second Fresnel lens facing the fourth aspheric lens is 1 mm to 15 mm, and the absolute value of the sagittal height of the optical surface of the second Fresnel lens away from the fourth aspheric lens is 1 mm to 15 mm.

7. The optical path structure according to claim 2, characterized in that: At least one optical surface of the third lens group is a Fresnel surface.

8. The optical path structure according to claim 7, characterized in that: One optical surface of the third lens group is a Fresnel surface, and another optical surface of the third lens group opposite to the Fresnel surface is an aspherical surface.

9. The optical path structure according to claim 7 or 8, characterized in that: At least one circle of thread protrusions on the Fresnel surface is an aspherical surface.

10. The optical path structure according to claim 1, characterized in that: An absorption polarizer is arranged on a side of the reflection polarizer away from the phase retarder.

11. The optical path structure according to claim 1, characterized in that: An anti-reflection film is arranged on the optical surface of the second lens group at a side away from the beam-splitting film.

12. The optical path structure according to claim 1, characterized in that: A ratio of an absolute value of a focal length of the first lens group to an absolute value of a focal length of the second lens group is greater than 0.1 and less than 6.

13. An optical display system, characterized in that: include: The optical path structure according to any one of claims 1 to 12; The display panel is arranged on a side of the third lens group away from the second lens group.

14. A virtual reality device, characterized in that: Comprising the optical display system as claimed in claim 13.

15. A method for adjusting focal length, characterized in that: Based on the optical display system according to claim 13, comprising: When the distance between the first lens group and the display panel does not increase, the focal length of the optical display system is adjusted by adjusting the distance between the second lens group and the first lens group and / or the display panel, and / or by adjusting the distance between the third lens group and the first lens group and / or the display panel.

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