Optical module and head-mounted display device

Abstract

The present application discloses an optical module and a head-mounted display device; the optical module sequentially includes a first lens and a second lens along the optical axis direction, the surface of the first lens close to the second lens is an aspheric surface, and the aspheric surface is configured such that, from the center to the edge direction, the absolute value of its surface sag height shows a changing trend of gradually increasing to z2 and then gradually decreasing to z1, where z1 is the absolute value of the sag height of the edge of the aspheric surface, z2 is the absolute value of the sag height of the lowest point on the aspheric surface, and the difference between z2 and z1 is 0.1 mm to 0.4 mm; the optical module further includes a beam splitter element, a first phase retarder, and a polarization reflection element, and the first phase retarder is located between the beam splitter element and the polarization reflection element; the beam splitter element and the first phase retarder are located on either side of the second lens, and the polarization reflection element is disposed on the aspheric surface of the first lens. The optical module of the present application can reduce the overall optical length of the optical module while ensuring the imaging quality.

Description

Technical Field

[0001] The present application relates to the field of optical display technology, and more specifically, to an optical module and a head-mounted display device. Background Art

[0002] With the rapid development of virtual reality technology, the types of virtual reality devices are diversified and the application fields are becoming more and more extensive. In order to achieve lightness and thinness, virtual reality devices use the folded optical path method in the existing technology. In order to further reduce the size of the optical module, the main method is to reduce the number of lenses in the optical module, but this will affect the imaging quality of the optical module to a certain extent. Summary of the invention

[0003] The purpose of this application is to provide a new technical solution for an optical module and a head-mounted display device, which can reduce the total optical length of the optical module while ensuring the imaging quality.

[0004] According to one aspect of the present application, an optical module is provided, wherein the optical module includes a first lens and a second lens in sequence along an optical axis direction, wherein a surface of the first lens close to the second lens is an anti-curved surface, and the anti-curved surface is configured such that, from the center to the edge, the absolute value of the surface sagitta of the anti-curved surface first gradually increases to z2 and then gradually decreases to z1, wherein z1 is the absolute value of the sagitta of the edge of the anti-curved surface, z2 is the absolute value of the sagitta of the lowest point on the anti-curved surface, and the difference between z2 and z1 is 0.1 mm to 0.4 mm;

[0005] The optical module also includes a beam splitter, a first phase delay and a polarization reflection element, wherein the first phase delay is located between the beam splitter and the polarization reflection element; the beam splitter and the first phase delay are located on either side of the second lens, and the polarization reflection element is arranged on the reverse curved surface of the first lens.

[0006] Optionally, the absolute value of the sagittal height of the edge of the inverse curved surface is z1, the absolute value of the sagittal height of the lowest point on the inverse curved surface is z2, and the difference between z2 and z1 is 0.14 mm to 0.37 mm.

[0007] Optionally, the optical module further includes a display screen, and the display screen is located on a side of the second lens away from the first lens, wherein a distance between the polarized reflective element and the display screen is 12 mm to 16 mm.

[0008] Optionally, the absolute value z1 of the sagittal height of the edge of the inverse curved surface is 0.5 mm to 1 mm, and the absolute value z2 of the sagittal height of the lowest point on the inverse curved surface is 0.6 mm to 1.5 mm.

[0009] Optionally, the second lens is located between the beam splitting element and the first phase retarder.

[0010] Optionally, the beam splitting element is disposed on the surface of the second lens away from the aspherical surface, and the first phase retarder is disposed on the surface of the second lens close to the aspherical surface.

[0011] Optionally, the optical module further includes a first polarizing element;

[0012] The first polarizing element and the polarization reflection element are stacked and disposed together on the aspherical surface; alternatively, the first polarizing element is disposed on the surface of the first lens away from the second lens.

[0013] Optionally, the display screen is configured to emit circularly polarized light or linearly polarized light;

[0014] When the light emitted by the display screen is linearly polarized light, a second phase retarder is further disposed on the light-emitting side of the display screen, and the second phase retarder is configured to convert the linearly polarized light into circularly polarized light.

[0015] Optionally, the beam splitting element is located between the first phase retarder and the second phase retarder.

[0016] Optionally, the optical module further includes a second polarizing element, wherein the second phase retarder is located between the beam splitting element and the second polarizing element;

[0017] The second polarizing element has a transmission axis, and the included angle between the transmission axis of the second polarizing element and the fast axis or the slow axis of the second phase retarder is 45°.

[0018] Optionally, the second polarizing element and the second phase retarder are stacked to form a stacked element, and the stacked element is disposed on the light-emitting surface of the display screen.

[0019] According to another aspect of the present application, there is provided a head-mounted display device, the head-mounted display device including:

[0020] A housing; and

[0021] The optical module as described above.

[0022] The beneficial effects of the present application are as follows:

[0023] An embodiment of the present application provides an optical solution for a folded optical path design, which introduces a lens with an aspherical surface type into the optical path, and a polarization reflection element is arranged on the aspherical surface of the lens. By adjusting the shape of the aspherical surface, that is, adjusting the difference between the absolute value of the sagitta at the lowest point on the aspherical surface and the absolute value of the sagitta at the edge within a set range, the distance from the polarization reflection element to the display screen can be reduced, that is, the total optical length of the optical module can be reduced, and at the same time, good imaging quality can be ensured.

[0024] Other features and advantages of the present application will become clear from the following detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present application and, together with the description, are used to explain the principles of the present application.

[0026] Figure 1 is one of the schematic structural diagrams of the optical module according to an embodiment of the present application;

[0027] Figure 2 is the schematic structural diagram of the aspherical surface of the first lens in the optical module according to an embodiment of the present application;

[0028] Figure 3 is the schematic partial structural diagram of the optical module according to an embodiment of the present application;

[0029] Figure 4 is the modulation transfer function MTF curve of the optical module according to an embodiment of the present application at 450 nm;

[0030] Figure 5 is the modulation transfer function MTF curve of the optical module according to an embodiment of the present application at 540 nm;

[0031] Figure 6 is the modulation transfer function MTF curve of the optical module according to an embodiment of the present application at 610 nm;

[0032] Figure 7 is the second schematic structural diagram of the optical module according to an embodiment of the present application.

[0033] DESCRIPTION OF THE REFERENCE NUMERALS

[0034] 10. First lens; 11. First surface; 12. Aspherical surface; 20. Second lens; 21. Third surface; 22. Fourth surface; 30. Display screen; 40. Beam splitter element; 50. First phase retarder; 60. Polarization reflection element; 70. Second polarizing element; 80. Second phase retarder; 100. Optical axis; 01. Human eye; 02. Light ray. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application.

[0036] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application, its application, or use.

[0037] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the specification.

[0038] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0039] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0040] The following combines the attached Figures 1 to 7 A detailed description is given of the optical module and the head-mounted display device provided by the embodiments of the present application.

[0041] According to one aspect of the embodiments of the present application, an optical module is provided. The optical module is designed with a folded optical path optical structure and is suitable for application in a head-mounted display device (HMD), such as a VR smart glasses, a VR helmet, etc.

[0042] The embodiments of the present application provide an optical module, as Figure 1 shown. The optical module sequentially includes a first lens 10 and a second lens 20 along the optical axis 100 direction. The surface of the first lens 10 close to the second lens 20 is an aspherical surface 12. The aspherical surface 12 is configured such that, from the center to the edge direction, the absolute value of its surface sag height shows a changing trend of gradually increasing to z2 and then gradually decreasing to z1. Here, z1 is the absolute value of the edge sag height of the aspherical surface 12, z2 is the absolute value of the lowest point sag height of the aspherical surface 12, and the difference between z2 and z1 is 0.1 mm to 0.4 mm, as Figure 2 shown;

[0043] The optical module further includes a beam splitter 40, a first phase retarder 50, and a polarization reflection element 60. The first phase retarder 50 is located between the beam splitter 40 and the polarization reflection element 60. The beam splitter 40 and the first phase retarder 50 are located on either side of the second lens 20, and the polarization reflection element 60 is disposed on the aspherical surface 12 of the first lens 10.

[0044] The optical module according to the embodiment of the present application has a folded optical path design. For example, the optical module may include two lenses, namely the above-mentioned first lens 10 and second lens 20. The first lens 10 includes a first surface 11 close to the human eye 01 and a second surface far from the human eye 01. Among them, by designing the second surface of the first lens 10 as an aspherical surface 12, which is different from a conventional curved surface, its appearance shows that from the center to the edge, as the aperture of the first lens 10 increases, the absolute value of the sag height of the aspherical surface 12 shows a trend of decreasing from large to small. Specifically, the absolute value of the sag height first gradually increases to z2 (the lowest point of the surface), and then decreases from z2 to z1 (the edge of the aspherical surface 12), as shown in Figure 2 shown. At the same time, the polarization reflection element 60 is disposed on the aspherical surface 12 of the first lens 10, so that the distance between the polarization reflection element 60 and the display screen 30 can be reduced, which is beneficial to reducing the overall optical length of the optical module.

[0045] Please continue as shown in Figure 2 shown, the absolute value of the sag height at the edge of the aspherical surface 12 is z1, and the absolute value of the sag height at the lowest point of the aspherical surface 12 is z2, where z2 > z1. Specifically, two changing trends are formed on the aspherical surface 12 from the center to the edge, that is, the absolute value of the surface sag height first increases to z2, and after passing through the lowest point and reaching the edge, the absolute value of the surface sag height gradually decreases until z1.

[0046] When the difference between z2 and z1 (or the difference between the sag height at the edge and the sag height at the lowest point of the aspherical surface 12) is 0.1 mm to 0.4 mm, the distance between the polarization reflection element 60 and the display screen 30 can be reasonably reduced while ensuring the imaging quality, that is, the overall optical length of the optical module is effectively reduced.

[0047] The polarization reflection element 60 is attached to the aspherical surface 12 (the surface on the side of the first lens 10 far from the human eye 01). The surface shape of the aspherical surface 12 is specifically as shown in Figure 2 shown, Figure 2 in which the Z-axis represents the sag height direction of the aspherical surface 12, the X-axis represents the aperture direction of the first lens 10, z1 represents the absolute value of the sag height corresponding to the edge of the aspherical surface 12, and z2 represents the absolute value of the sag height corresponding to the lowest point of the aspherical surface 12.

[0048] It should be noted that in conventional optical design solutions, the optical total length of the optical module is usually reduced by reducing the number of lenses in the optical module and / or adjusting the thickness of the lenses. However, in the optical module of the embodiment of the present application, the surface shape of one of the lens surfaces is adjusted to an anti-curved surface 12, and the difference between the absolute value z2 of the lowest point sagittal height and the absolute value z1 of the edge sagittal height on the anti-curved surface 12 is adjusted within a set range (0.1 mm to 0.4 mm), so as to reduce the distance between the polarization reflection element 60 and the display screen 30, thereby reducing the optical total length of the optical module.

[0049] The optical module of the embodiment of the present application, where the number of lenses includes but is not limited to the two lenses mentioned above. For example, when the optical module contains two lenses, compared with a conventional optical module containing two lenses, the optical total length of the optical module of the present application is smaller and the imaging quality is higher.

[0050] That is to say, the optical solution of the embodiment of the present application can not only reduce the optical total length of the optical module, thereby reducing the size of the optical module, but also ensure the imaging quality of the optical module.

[0051] As Figure 3 shown, for the optical module of the embodiment of the present application, the light 02 in the edge field of view satisfies the law of reflection when transmitted on the anti-curved surface 12 of the first lens 10, that is, the incident angle B = the exit angle C. Assume a ray of light is emitted from the human eye 01, the incident angle B is the incident angle of the light 02 on the anti-curved surface 12, and the exit angle C is the exit angle of the light 02 on the anti-curved surface 12. Figure 3 The angle A shown in is the angle formed by the exit ray and the optical axis 100. In the optical module of the embodiment of the present application, the larger the difference between the absolute value z2 of the lowest point sagittal height (also known as the maximum absolute value of the sagittal height on the anti-curved surface 12) and the absolute value z1 of the edge sagittal height of the anti-curved surface 12 on the anti-curved surface 12, the greater the curvature of the anti-curved surface 12, and the greater the incident angle B and the exit angle C.

[0052] Please continue to refer to Figure 3 It can be seen that the incident angle B, the exit angle C, and the angle A are positively correlated. Therefore, the angle A is positively correlated with the difference between the edge sagittal height of the anti-curved surface 12 and the lowest point sagittal height of the anti-curved surface 12. Since the image height remains unchanged, when the angle A is larger, the distance from the display screen 30 to the anti-curved surface 12 is smaller. Therefore, the larger the difference between the edge sagittal height of the anti-curved surface 12 and the lowest point sagittal height of the anti-curved surface 12 (that is, the larger the difference between z2 and z1), the smaller the distance from the polarization reflection element 60 to the display screen 30. In the design of the present application, when the difference between the absolute value z2 of the lowest point sagittal height and the absolute value z1 of the edge sagittal height on the anti-curved surface 12 is 0.1 mm to 0.4 mm, the optical module has better imaging quality.

[0053] The embodiment of the present application provides an optical solution for a folded optical path. A first lens 10 with an aspherical surface 12 is introduced into the optical path, and a polarization reflection element 60 is arranged on the aspherical surface 12. By adjusting the shape of the aspherical surface 12, that is, adjusting the difference between the absolute value z2 of the sag height at the lowest point on the aspherical surface 12 and the absolute value z1 of the sag height at the edge within a set range, the distance from the polarization reflection element 60 to the display screen 30 can be reduced, that is, the overall optical length of the optical module can be reduced, and good imaging quality can be ensured at the same time.

[0054] Optionally, the absolute value of the sag height at the edge of the aspherical surface 12 is z1, the absolute value of the sag height at the lowest point on the aspherical surface 12 is z2, and the difference between z2 and z1 is 0.14 mm to 0.37 mm.

[0055] When the difference between z2 and z1 of the aspherical surface 12 is 0.14 mm to 0.37 mm, at this time, the curvature difference at different positions on the surface of the aspherical surface 12 is not too large, so that the processing difficulty of the aspherical surface 12 is low, the production cost of the optical module will not be increased, and the yield of the optical module can be improved. At the same time, within this range, the overall optical length of the optical module is small, and good imaging quality can be achieved.

[0056] It should be noted that the optical module in the embodiment of the present application is not limited to only including the first lens 10 and the second lens 20. The specific number of lenses in the optical module can be adjusted according to needs. However, when the number of lenses is the same, compared with the conventional folded optical path optical module, the optical module in the embodiment of the present application has the advantages of a smaller overall optical length and better imaging quality.

[0057] The optical module provided by the embodiment of the present application is a folded optical path. In addition to including the above-mentioned first lens 10 and second lens 20, it also includes a beam splitter 40, a first phase retarder 50, and a polarization reflection element 60.

[0058] Among them, the beam splitter 40 is, for example, a semi-reflective semi-transmissive film.

[0059] The beam splitter 40 allows a part of the light to be transmitted and a part of the light to be reflected.

[0060] It should be noted that the reflectivity of the beam splitter 40 can be flexibly adjusted according to specific needs, and the embodiment of the present application does not limit this.

[0061] Among them, the first phase retarder 50 is, for example, a quarter-wave plate or other phase retardation plates.

[0062] The phase retarder can be used to change the polarization state of the light in the folded optical path structure. For example, it is used to convert linearly polarized light into circularly polarized light, or circularly polarized light into linearly polarized light.

[0063] Among them, the polarization reflection element 60 is, for example, a polarization reflection film.

[0064] The polarization reflection element 60 is a polarization reflector that reflects horizontally polarized light and transmits vertically polarized light, or any other polarization reflector that reflects linearly polarized light at a specific angle and transmits linearly polarized light in the direction perpendicular to that angle.

[0065] In the embodiments of the present application, the first phase retarder 50 and the polarization reflection element 60 cooperate to analyze light rays and transmit the light rays. The polarization reflection element 60 has a transmission axis, and the angle between the direction of the transmission axis of the polarization reflection element 60 and the fast axis or slow axis of the first phase retarder 50 is 45°.

[0066] In the embodiments of the present application, the polarization reflection element 60 can be mounted on the concave surface 12 of the first lens 10 through an optical adhesive. Among them, the polarization reflection element 60 can be separately arranged from the first phase retarder 50 and the beam splitting element 40. On this basis, the beam splitting element 40 and the first phase retarder 50 can be mounted together on either side of the second lens 20. Of course, they can also be arranged at intervals. It should be noted that the first phase retarder 50 should be located between the beam splitting element 40 and the polarization reflection element 60.

[0067] The optical module provided by the embodiments of the present application, as Figure 1 shown, the propagation process of light rays is as follows:

[0068] Left-handed or right-handed circularly polarized light passes through the second lens 20 and the beam splitting element 40, and after passing through the first phase retarder 50, it becomes horizontally polarized light; after being reflected by the polarization reflection element 60 and passing through the first phase retarder 50, it becomes horizontally polarized light; after being reflected by the polarization reflection element 60, it becomes horizontally polarized light, and then after passing through the first phase retarder 50 and the second lens 20, it becomes left-handed or right-handed circularly polarized light, which is reflected by the beam splitting element 40 to form right-handed or left-handed circularly polarized light, and then passes through the second lens 20 and the first phase retarder 50 again to become vertically polarized light, and enters the human eye 01 after passing through the polarization reflection element 60 and the first lens 10.

[0069] The optical module provided by the embodiments of the present application is a folded optical path optical structure design. As Figure 1 shown, each optical lens and optical element in the optical module can be arranged in a set manner and located on the same optical axis 100. The size of the entire optical path structure is small and does not occupy a large space. It is very suitable for application in smart wearable devices, such as head-mounted display devices.

[0070] In some examples of the present application, as Figure 1As shown, the optical module further includes a display screen 30, the display screen 30 is located on the side of the second lens 20 away from the first lens 10, and the distance between the polarization reflection element 60 and the display screen 30 is 12 mm to 16 mm.

[0071] In the optical module according to the embodiment of the present application, the distance between the polarization reflection element 60 and the display screen 30 is reduced. For example, the distance between the two can be only 12 mm to 16 mm, which effectively reduces the total optical length of the optical module. In this way, when the optical module is applied to a head-mounted display device, the head-mounted display device can be made thinner and lighter. Moreover, when the distance between the polarization reflection element 60 and the display screen 30 is 12 mm to 16 mm, the optical module can also have better imaging quality, and the user can view a clear and complete picture after using the optical module.

[0072] It should be noted that in the optical module based on the present application, the surface shape of the first lens 10 close to the human eye 01 side is designed as Figure 2 the aspheric surface shown. By adjusting the difference between the absolute value z2 of the lowest point sagittal height and the absolute value z1 of the edge sagittal height on the aspheric surface 12, the total optical length and imaging quality of the optical module can be reasonably controlled. This is not limited in the present application.

[0073] Among them, the display screen 30 has a light-emitting surface and can emit imaging light.

[0074] Optionally, a protective glass can be provided on the light-emitting surface of the display screen 30, for example.

[0075] The display screen 30 can be a self-luminous screen or a reflective screen such as a DMD. Among them, the self-luminous screen includes LCD, LED, OLED, Micro-OLED, ULED, etc.

[0076] In some examples of the present application, referring to Figure 2 , for the aspheric surface 12 of the first lens 10, the absolute value z1 of the edge sagittal height of the aspheric surface 12 can be designed to be 0.5 mm to 1 mm, and the absolute value z2 of the lowest point sagittal height on the aspheric surface 12 is 0.6 mm to 1.5 mm.

[0077] The above parameter design can make the difference between the absolute value z2 of the lowest point sagittal height and the absolute value z1 of the edge sagittal height on the aspheric surface 12 within a set range, such as 0.1 mm to 0.4 mm as described above. More preferably, it is 0.14 mm to 0.37 mm, so that the optical module can have a smaller total optical length and higher imaging quality while having two lenses.

[0078] In some examples of the present application, such as Figure 1As shown, the second lens 20 is located between the beam splitting element 40 and the first phase retarder 50.

[0079] In an embodiment of the present application, a polarization reflection element 60 is disposed on the aspherical surface 12 of the first lens 10, and the aspherical surface 12 is close to the second lens 20. The beam splitting element 40 and the first phase retarder 50 are separately disposed from the polarization reflection element 60. The beam splitting element 40 and the first phase retarder 50 may be located between the second lens 20 and the display screen 30, or the beam splitting element 40 and the first phase retarder 50 may also be located between the second lens 20 and the aspherical surface 12 of the first lens 10. The setting positions are relatively flexible, but the first phase retarder 50 needs to be located between the beam splitting element 40 and the polarization reflection element 60.

[0080] Optionally, the second lens 20 separates the beam splitting element 40 from the first phase retarder 50.

[0081] In some examples of the present application, as Figure 1 shown, the beam splitting element 40 is disposed on the surface of the second lens 20 away from the aspherical surface 12 (i.e., Figure 1 the fourth surface 22 shown), and the first phase retarder 50 is disposed on the surface of the second lens 20 close to the aspherical surface 12 (i.e., Figure 1 the third surface 21 shown in

[0082] That is to say, two surfaces of the second lens 20 are used to support the beam splitting element 40 and the first phase retarder 50 respectively, which reduces the difficulty of film laminating compared with laminating films on the same surface of the second lens 20.

[0083] Specifically, the beam splitting element 40 (half-reflective and half-transmissive film) can be formed on the fourth surface 22 of the second lens 20 facing the display screen 30 by means of coating. The coating method has relatively low requirements for the shape of the fourth surface 22 of the second lens 20, and the formed half-reflective and half-transmissive film can be firmly attached to the fourth surface 22 of the second lens 20.

[0084] The first phase retarder 50 can be mounted on the third surface 21 of the second lens 20 by means of optical glue. Single-layer film laminating is conducive to laminating the film flatly with relatively low difficulty.

[0085] It should be noted that the first phase retarder 50 can be mounted on a flat surface, or can be mounted on a curved surface such as a spherical surface, an aspherical surface, or a cylindrical surface. Mounting on a flat surface can reduce the difficulty of film laminating and improve production efficiency.

[0086] In some examples of the present application, as Figure 1 shown, the optical module further includes a first polarizing element ( Figure 1(not shown in the figure); the first polarizing element and the polarization reflection element 60 are stacked and disposed together on the anti-curved surface 12; alternatively, the first polarizing element is disposed on the surface of the first lens 10 away from the second lens 20.

[0087] Among them, the first polarizing element can transmit P-polarized light in the optical module, can reduce stray light, and is beneficial to improving the imaging quality.

[0088] In an embodiment of the present application, the first polarizing element is, for example, a polarizing film, which can be attached to the polarization reflection element 60, or can be spaced apart from the polarization reflection element 60.

[0089] For example, as Figure 1 shown, when the first polarizing element and the polarization reflection element 60 are spaced apart, the first polarizing element can be disposed on the first surface 11 of the first lens 10. In this way, the first polarizing element and the polarization reflection element 60 disposed on the anti-curved surface 12 of the first lens 10 are spaced apart.

[0090] It should be noted that when the first polarizing element is mounted on the first surface 11 of the first lens 10, the first surface 11 can be a plane, or can be a curved surface such as a spherical surface, an aspherical surface, or a cylindrical surface. Mounting on a plane can reduce the difficulty of film sticking and improve production efficiency.

[0091] In addition, the polarization reflection element 60 can be formed on the anti-curved surface 12 by coating. Compared with optical glue mounting, the polarization reflection element 60 can be better attached to the anti-curved surface 12.

[0092] In some examples of the present application, as Figure 1 shown, the display screen 30 is used to emit circularly polarized light or linearly polarized light; when the light emitted by the display screen 30 is linearly polarized light, a second phase retarder 80 is further provided on the light-emitting side of the display screen 30, and the second phase retarder 80 is used to convert the linearly polarized light into circularly polarized light.

[0093] That is to say, the light emitted by the display screen 30 and incident on the second lens 20 should be left-handed or right-handed circularly polarized light.

[0094] Among them, the beam splitting element 40 is located between the first phase retarder 50 and the second phase retarder 80. Lenses can also be reasonably arranged between different optical modules to improve the imaging quality, which is not limited in the embodiments of the present application.

[0095] In some examples of the present application, as Figure 1As shown, the optical module further includes a second polarizing element 70. Among them, the second phase retarder 80 is located between the beam splitting element 40 and the second polarizing element 70; the second polarizing element 70 has a transmission axis, and the included angle between the transmission axis of the second polarizing element 70 and the fast axis or slow axis of the second phase retarder 80 is 45°.

[0096] When it is necessary to provide the second phase retarder 80 at the light-emitting surface of the display screen 30, another polarizing element (i.e., the above-mentioned second polarizing element, which is the polarizing element on the near-display side here) can be further introduced into the optical path. The second polarizing element 70 can also transmit P-polarized light in the optical module, which can reduce stray light and is beneficial to improving the imaging quality.

[0097] Optionally, the second polarizing element 70 and the second phase retarder 80 are stacked to form a stacked element, and the stacked element is provided on the light-emitting surface of the display screen 30.

[0098] Of course, the second polarizing element 70 and the second phase retarder 80 can also be arranged at intervals. The second phase retarder 80 is located between the second polarizing element 70 and the light-emitting surface of the display screen 30.

[0099] As Figure 1 shown, the propagation process of light in the optical module is as follows:

[0100] The light emitted by the display screen 30 becomes horizontal linearly polarized light after passing through the second polarizing element 70, and becomes left-handed or right-handed circularly polarized light after passing through the second phase retarder 80; the left-handed or right-handed circularly polarized light passes through the second lens 20 and the beam splitting element 40, and passes through the first phase retarder 50 to become horizontal linearly polarized light; after being reflected by the polarization reflection element 60 and passing through the first phase retarder 50, it becomes horizontal linearly polarized light; after being reflected by the polarization reflection element 60, it becomes horizontal linearly polarized light, and then passes through the first phase retarder 50 and the second lens 20 to become left-handed or right-handed circularly polarized light. After being reflected by the beam splitting element 40, it forms right-handed or left-handed circularly polarized light, and then passes through the second lens 20 and the first phase retarder 50 again to become vertical polarized light, and enters the human eye 01 after passing through the polarization reflection element 60 and the first lens 10.

[0101] In addition, it should be noted that when the light emitted from the light-emitting surface of the display screen 30 is itself circularly polarized light, the above-mentioned second phase retarder 80 and second polarizing element 70 can be omitted.

[0102] In the optical module provided by the embodiment of the present application, by arranging the polarization reflection element 60 on the aspherical surface 12 of the first lens 10, the distance between the polarization reflection element 60 and the display screen 30 is effectively reduced. Preferably, the difference between the edge sagittal height and the minimum sagittal height of the aspherical surface 12 is 0.14 mm to 0.37 mm. The larger this difference is, the smaller the distance between the polarization reflection element 60 and the display screen 30 is, which is more conducive to the miniaturization design of the module.

[0103] Embodiment 1

[0104] As Figure 1 shown, the optical module provided in this Embodiment 1 sequentially includes a first lens 10, a second lens 20, and a display screen 30 along the optical axis 100 direction. Among them, the second lens 20 is located between the first lens 10 and the display screen 30. The surface of the first lens 10 close to the second lens 20 is the aspherical surface 12. The aspherical surface 12 is configured such that, from the center to the edge direction, the absolute value of its surface sagittal height shows a changing trend of gradually increasing to z2 first and then gradually decreasing to z1. Among them, z1 is the absolute value of the edge sagittal height of the aspherical surface 12, and z2 is the absolute value of the lowest point sagittal height on the aspherical surface 12. As Figure 2 shown;

[0105] Among them, the absolute value z1 of the edge sagittal height of the aspherical surface 12 is 0.65 mm, the absolute value z2 of the lowest point sagittal height on the aspherical surface 12 is 1.02 mm, and the difference between z2 and z1 is 0.37;

[0106] The optical module further includes a beam splitting element 40, a first phase retarder 50, and a polarization reflection element 60. The beam splitting element 40 is arranged on the surface of the second lens 20 away from the aspherical surface 12 (i.e., the fourth surface 22), the first phase retarder 50 is arranged on the surface of the second lens 20 close to the aspherical surface 12 (i.e., the third surface 21), the polarization reflection element 60 is arranged on the aspherical surface 12 of the first lens 10, and the distance between the polarization reflection element 60 and the display screen 30 is 13.2 mm.

[0107] Table 1 shows the optical parameters of the optical module of this Embodiment 1.

[0108] Table 1

[0109]

[0110] It should be noted that, as Figure 1 shown, for the optical module, the surface of each optical element close to the human eye 01 is the front surface, and the other surface is the back surface.

[0111] The optical performance of the optical module of this Embodiment 1 is as follows:

[0112] Figure 4 、 Figure 5 、Figure 6 MTF curves of the optical module of Example 1 at 450 nm, 540 nm, and 610 nm respectively. From Figures 4 to 6 it can be seen that: at a spatial frequency of 20 lp / mm, at a wavelength of 450 nm, the MTF value of the optical module is higher than 0.7; at a wavelength of 540 nm, the MTF value of the optical module is higher than 0.8; at a wavelength of 610 nm, the MTF of the optical module is higher than 0.6. The optical module can form clear images.

[0113] Example 2

[0114] The optical module provided in Example 2, as Figure 7 shown, is different from that of Example 1 in that:

[0115] Among them, the absolute value z1 of the edge sag of the aspheric surface 12 is 0.73 mm, the absolute value z2 of the lowest point sag on the aspheric surface 12 is 0.87 mm, and the difference between z2 and z1 is 0.14; the polarization reflection element 60 is disposed on the aspheric surface 12 of the first lens 10, and the distance between the polarization reflection element 60 and the display screen 30 is 13.9 mm.

[0116] Table 2 shows the optical parameters of the optical module of Example 2.

[0117] Table 2

[0118]

[0119] The optical performance of the optical module of Example 2 can also be referred to Figures 4 to 6 , and the optical module can form clear images.

[0120] According to another aspect of the embodiments of the present application, a head-mounted display device is further provided, and the head-mounted display device includes a housing and the optical module as described above.

[0121] The head-mounted display device is, for example, a VR head-mounted device, including a VR glasses or a VR helmet, etc., and the embodiments of the present application do not make specific limitations thereto.

[0122] The specific implementation manners of the head-mounted display device of the embodiments of the present application can refer to the embodiments of the above optical module, and thus at least have all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0123] In the above embodiments, the differences between the embodiments are mainly described. As long as the different optimization features between the embodiments are not contradictory, they can be combined to form a more optimal embodiment. Considering the simplicity of the text, it will not be elaborated herein.

[0124] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. An optical module, characterized in that, The optical module sequentially includes a first lens (10) and a second lens (20) along the optical axis (100) direction. The surface of the first lens (10) close to the second lens (20) is an aspherical surface (12). The aspherical surface (12) is configured such that, from the center to the edge direction, the absolute value of its surface sag height first gradually increases to z2 and then gradually decreases to z1. Here, z1 is the absolute value of the edge sag height of the aspherical surface (12), z2 is the absolute value of the sag height at the lowest point on the aspherical surface (12), and the difference between z2 and z1 is 0.1 mm to 0.4 mm. The optical module further includes a beam splitter element (40), a first phase retarder (50), and a polarization reflection element (60). Among them, the first phase retarder (50) is located between the beam splitter element (40) and the polarization reflection element (60); the beam splitter element (40) and the first phase retarder (50) are located on either side of the second lens (20), and the polarization reflection element (60) is disposed on the aspherical surface (12) of the first lens (10).

2. The optical module according to claim 1, wherein The absolute value of the edge sag height of the aspherical surface (12) is z1, the absolute value of the sag height at the lowest point on the aspherical surface (12) is z2, and the difference between z2 and z1 is 0.14 mm to 0.37 mm.

3. The optical module according to claim 1, wherein The optical module further includes a display screen (30). The display screen (30) is located on the side of the second lens (20) away from the first lens (10). Among them, the distance between the polarization reflection element (60) and the display screen (30) is 12 mm to 16 mm.

4. The optical module according to claim 1, wherein The absolute value z1 of the edge sag height of the aspherical surface (12) is 0.5 mm to 1 mm, and the absolute value z2 of the sag height at the lowest point on the aspherical surface (12) is 0.6 mm to 1.5 mm.

5. The optical module according to claim 1, wherein The second lens (20) is located between the beam splitter element (40) and the first phase retarder (50).

6. The optical module according to claim 1, wherein The beam splitter element (40) is disposed on the surface of the second lens (20) away from the aspherical surface (12), and the first phase retarder (50) is disposed on the surface of the second lens (20) close to the aspherical surface (12).

7. The optical module according to claim 1, characterized in that The optical module further includes a first polarizing element; The first polarizing element is stacked with the polarization reflection element (60) and is disposed together on the aspherical surface (12); or, the first polarizing element is disposed on the surface of the first lens (10) away from the second lens (20).

8. The optical module according to claim 3, characterized in that, The display screen (30) is used to emit circularly polarized light or linearly polarized light; When the light emitted by the display screen (30) is linearly polarized light, a second phase retarder (80) is further provided on the light-emitting side of the display screen (30). The second phase retarder (80) is used to convert the linearly polarized light into circularly polarized light.

9. The optical module according to claim 8, wherein The beam splitter element (40) is located between the first phase retarder (50) and the second phase retarder (80).

10. The optical module according to claim 8, wherein, The optical module further includes a second polarizing element (70), wherein the second phase retarder (80) is located between the beam splitting element (40) and the second polarizing element (70); The second polarizing element (70) has a transmission axis, and the angle between the transmission axis of the second polarizing element (70) and the fast axis or the slow axis of the second phase retarder (80) is 45°.

11. The optical module according to claim 10, wherein The second polarizing element (70) and the second phase retarder (80) are stacked to form a stacked element, and the stacked element is disposed on the light-emitting surface of the display screen (30).

12. A head-mounted display device, characterized in that, Comprising: A housing; And The optical module according to any one of claims 1-11.

Images