Optical module and smart wearable device

Abstract

Embodiments of the present application provide an optical module and a smart wearable device; wherein, the optical module includes: an imaging lens group, a beam splitter element, a first phase retarder, and a polarization reflection element; the imaging lens group includes a first lens, a second lens, and a third lens arranged in sequence along the same optical axis, and the first lens, the second lens, and the third lens are glued together; the beam splitter element, the first phase retarder, and the polarization reflection element are sequentially arranged in the optical path of the imaging lens group; wherein, the ratio of the effective aperture H2 of the third lens to the effective aperture H1 of the first lens is 1.23 to 1.27. The optical solution provided by the embodiments of the present application introduces a lens between two lenses in the folded optical path and glues the three lenses together, which can reduce the aperture size of the third lens on the near screen side, thereby facilitating the reduction of the volume and weight of the optical module.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of optical imaging technology. More specifically, embodiments of the present application relate to an optical module and a smart wearable device. Background Art

[0002] Virtual Reality (VR) technology integrates computer, electronic information, and simulation technologies. Its basic implementation method is that a computer simulates a virtual environment to give people a sense of immersion in the environment. Currently, even with a folded optical path structure, VR optical modules generally have problems of large volume and heavy weight, which reduces the comfort of users when wearing. Summary of the Invention

[0003] The purpose of the present application is to provide a new technical solution for an optical module and a smart wearable device, which can reduce the aperture of the lens on the near-screen side in the optical module, thereby reducing the volume of the optical module.

[0004] In a first aspect, the present application provides an optical module. The optical module includes:

[0005] An imaging lens group, which includes a first lens, a second lens, and a third lens arranged in sequence along the same optical axis, and the first lens, the second lens, and the third lens are glued together as a whole; and,

[0006] A beam splitter element, a first phase retarder, and a polarization reflection element, which are sequentially arranged in the optical path of the imaging lens group;

[0007] Wherein, the ratio of the effective aperture H2 of the third lens to the effective aperture H1 of the first lens is 1.23 - 1.27.

[0008] Optionally, the first lens includes a first surface and a second surface, and the first surface is a concave surface, and the second surface is a convex surface;

[0009] The second lens includes a third surface and a fourth surface, and both the third surface and the fourth surface are concave surfaces;

[0010] The third lens includes a fifth surface and a sixth surface, and both the fifth surface and the sixth surface are convex surfaces.

[0011] Optionally, the second surface and the third surface are mutually glued to glue the first lens and the second lens together; the fourth surface and the fifth surface are mutually glued to glue the second lens and the third lens together;

[0012] Among them, the refractive index of the second lens is 1.4 to 1.8.

[0013] Optionally, the exit angle B of the light on the surface where the second lens is glued to the first lens is ≤ 30°; where the light is a beam of light at the outermost edge of the marginal field of view.

[0014] Optionally, the focal length of the optical module is 16 mm to 20 mm.

[0015] Optionally, the optical module further includes a display screen, and the display screen is located on the side of the third lens away from the second lens;

[0016] The display screen is configured to be able to emit circularly polarized light or natural light;

[0017] When the light emitted by the display screen is natural light, a laminated sheet is provided on the light-emitting surface of the display screen, and the laminated sheet can convert the natural light emitted by the display screen into circularly polarized light; where the laminated sheet includes a stacked polarization element and a second phase retarder, the polarization element is provided on the display screen, and the second phase retarder is provided on the side of the polarization element away from the display screen.

[0018] Optionally, the first phase retarder and the second phase retarder are quarter-wave plates;

[0019] The first phase retarder is located between the beam splitting element and the polarization reflection element, and the transmission axis of the polarization reflection element forms a 45-degree angle with the fast axis or the slow axis of the first phase retarder;

[0020] The second phase retarder is located between the beam splitting element and the polarization element, and the transmission axis of the polarization element forms a 45-degree angle with the fast axis or the slow axis of the second phase retarder.

[0021] Optionally, the first phase retarder is provided on the glued surface of the second lens and the third lens, and the polarization reflection element is provided on the glued surface of the first lens and the second lens;

[0022] The beam splitting element is provided on the surface of the third lens close to the display screen, and the beam splitting element is located between the first phase retarder and the second phase retarder.

[0023] Optionally, the total optical length TTL of the optical module is 16 mm to 20 mm.

[0024] Optionally, the ineffective optical regions at the edges of the first lens, the second lens and the third lens are removed to form a vacant space on the outer periphery of the effective optical region of each lens.

[0025] Optionally, the optical module further includes an eye-tracking lens, and the eye-tracking lens is received within the empty space.

[0026] In a second aspect, the present application provides a smart wearable device. The smart wearable device includes:

[0027] a housing; and

[0028] an optical module as described in the first aspect, and the optical module is disposed on the housing.

[0029] The beneficial effects of the present application are as follows:

[0030] An embodiment of the present application provides an optical module, which includes three lenses, and the three lenses are glued together as a whole to form a folded optical path. The entire optical module has the characteristics of a short overall length of the optical system and a small aperture of the lenses, which is conducive to reducing the volume and weight of the entire optical module.

[0031] Other features and advantages of the present specification will become clear through the following detailed description of the exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present specification and, together with the description, are used to explain the principles of the present specification.

[0033] Figure 1 is one of the schematic structural diagrams of the optical module provided by the embodiment of the present application;

[0034] Figure 2 is the second of the schematic structural diagrams of the optical module provided by the embodiment of the present application;

[0035] Figure 3 is Figure 2 a partial enlarged schematic diagram of;

[0036] Figure 4 is the third of the schematic structural diagrams of the optical module provided by the embodiment of the present application;

[0037] Figure 5 is the schematic structural diagram of the imaging lens group of the optical module provided by the embodiment of the present application;

[0038] Figure 6 is the modulation transfer function MTF curve of the optical module provided by the embodiment of the present application at 450 nm;

[0039] Figure 7 is the modulation transfer function MTF curve of the optical module provided by the embodiment of the present application at 540 nm;

[0040] Figure 8 This is the modulation transfer function (MTF) curve of the optical module provided by the embodiment of the present application at 610 nm.

[0041] Explanation of reference numerals:

[0042] 1. Optical axis; 2. Empty space; 3. First lens; 301. First surface; 302. Second surface; 4. Second lens; 401. Third surface; 402. Fourth surface; 5. Third lens; 501. Fifth surface; 502. Sixth surface; 6. Display screen; 7. Polarizing element; 8. Polarizing reflection element; 9. First phase retarder; 10. Beam splitter element; 11. Second phase retarder; 01. Light ray; 02. Human eye. Detailed implementation manners

[0043] Now, various exemplary embodiments of the present application will 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.

[0044] 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 its use.

[0045] Techniques and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques and devices should be considered as part of the specification.

[0046] 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.

[0047] 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.

[0048] According to one aspect of the embodiments of the present application, an optical module is provided, which is a near-eye display module. The optical module is suitable for use in a head-mounted display device (HMD), such as a VR head-mounted display device. The VR head-mounted display device may include, for example, a VR smart glasses or a VR smart helmet, etc. The embodiments of the present application do not limit the specific form of the head-mounted display device. Of course, the optical module provided by the embodiments of the present application can also be applied to other types of electronic devices.

[0049] The optical module proposed by the embodiments of the present application, see Figure 1, the optical module includes: an imaging lens group, and a beam splitter 10, a first phase retarder 9, and a polarization reflection element 8. The entire optical structure is a folded optical path structure. The imaging lens group includes a first lens 3, a second lens 4, and a third lens 5 arranged in sequence along the same optical axis 1, and the first lens 3, the second lens 4, and the third lens 5 are glued together as a whole. The beam splitter 10, the first phase retarder 9, and the polarization reflection element 8 are sequentially arranged in the optical path of the imaging lens group; wherein, the ratio of the effective aperture H2 of the third lens 5 to the effective aperture H1 of the first lens 3 is 1.23 to 1.27.

[0050] According to the optical module provided in the above embodiment of the present application, the imaging lens group therein, for example, includes three lenses (respectively: the above-mentioned first lens 3, second lens 4, and third lens 5), and these three lenses are glued together as a whole, forming a three-piece glued folded optical path VR optical architecture. Under this three-piece glued lens, the imaging effect can fully meet the user's immersive experience of the VR device.

[0051] The optical module provided in the above embodiment of the present application introduces an intermediate lens between the two lenses on both sides, and the three lenses are glued together in sequence, which makes there be no air gap between the lenses on both sides. That is to say, the second lens 4 replaces the air gap between the first lens 3 and the second lens 4. The imaging lens group formed in this way has good integrity and is also convenient for assembly.

[0052] Figure 2 is a schematic structural diagram of the optical module provided in the embodiment of the present application, Figure 3 is Figure 2 a partial enlarged view of. Refer to Figure 2 and Figure 3 , for example, the first lens 3 is a lens closer to the human eye 02 side, and the second lens 4 and the third lens 5 are arranged in sequence along the same optical axis behind it. The light ray 01 is the outermost light ray of the edge field of view. The incident point of the light ray 01 on the second surface 302 of the first lens 3 (refer to Figure 5 , the second surface 302 is the surface glued to the second lens 4) is O, and the incident angle is A, then the effective aperture of the first lens 3 is 2*H1, and H1 is the distance from point O to the optical axis 1.

[0053] Please continue to refer to Figure 2 and Figure 3, when adding a second lens 4 (such as glue or plastic material) between the first lens 3 and the third lens 5 and gluing the three together, the exit angle of the light ray 01 on the third surface 401 of the second lens 4 (i.e., the surface where the second lens 4 is glued to the first lens 3) is B (the exit angle B is not greater than 30°, for example, 25°). The intersection point of the light ray 01 and the sixth surface 502 of the third lens 5 (i.e., the surface of the third lens 5 facing away from the second lens 4) is E, and the effective aperture of the third lens 5 is 2*H2, where H2 is the distance from point E to the optical axis 1 (the optical axis 1 of the imaging lens group). Then, according to the law of refraction, n3*sinA = n4*sinB, where n3 is the refractive index of the first lens 3.

[0054] When the material of the second lens 4 is air, that is, when there is air between the first lens 3 and the third lens 5, the exit angle of the light ray 01 on the surface of the second lens 4 close to the first lens 3 is C (this exit angle C is about 40°, significantly larger than the exit angle B). The intersection point of the light ray 01 and the sixth surface 502 of the third lens 5 is F, and the effective aperture of the third lens 5 is 2*H3, where H3 is the distance from point F to the optical axis 1. Then, according to the law of refraction, n3*sinA = 1*sinC.

[0055] See Figure 2 and Figure 3 , it can be seen that when a second lens 4 is added between the first lens 3 and the third lens 5 and the three lenses are glued together, compared with the case where there is air between the first lens 3 and the third lens 5, the exit angle B is smaller than the exit angle C, and the height H2 from the intersection point E to the optical axis 1 is smaller than the height H3 from the intersection point F to the optical axis 1. That is, after adding a second lens 4 between the first lens 3 and the third lens 5 and gluing them together, the aperture of the third lens 5 can be reduced, and thus the volume of the entire optical module can be reduced.

[0056] According to the optical module provided in the above embodiment of the present application, when the ratio of the effective aperture H2 of the third lens 5 to the effective aperture H1 of the first lens 3 is 1.23 - 1.27, the effective aperture (2*H2) of the third lens 5 can be reduced by 5.7% - 8.5% while ensuring the imaging quality, so that the aperture size of the lens can be appropriately reduced, which is beneficial to reducing the volume size of the optical module. It is beneficial to improve the comfort of the user when wearing the optical module.

[0057] When the ratio of the effective aperture H2 of the third lens 5 to the effective aperture H1 of the first lens 3 is 1.23 to 1.27, the entire optical module can achieve better imaging quality while minimizing the aperture design of the third lens 5 therein. Thus, the volume and imaging effect of the entire optical module are optimized.

[0058] The optical module provided in the above embodiment of the present application, for example, includes three lenses, and these three lenses can be glued together as a whole to form an optical structure of a folded optical path. The entire optical module can have the characteristics of a shorter total optical system length and a smaller aperture of the lens, which is beneficial to reducing the volume of the entire optical module. The optical module provided in the embodiment of the present application can take into account good optical performance in the case of a small volume.

[0059] The optical module provided in the embodiment of the present application is a folded optical path. In addition to including an imaging lens group, the optical module further includes optical elements such as a beam splitter 10, a first phase retarder 9, and a polarization reflection element 8, etc., which are used to form a folded optical path in cooperation with the imaging lens group.

[0060] These above-mentioned optical elements (which can be in the form of optical films) can be used to form a folded optical path between the respective lenses of the imaging lens group, so that light rays are refolded therein to extend the propagation path of the light rays, which is beneficial to the final clear imaging and at the same time beneficial to reducing the volume of the entire optical module.

[0061] In the embodiment of the present application, considering many factors such as the volume, weight, imaging quality, and production cost of the entire optical module, three cemented lenses are designed in the optical path, see Figure 1 and Figure 2 . Of course, the optical module of the embodiment of the present application includes but is not limited to using three lenses.

[0062] Among them, the beam splitter 10 is, for example, a semi-transparent and semi-reflective film. At this time, the beam splitter 10 allows a part of the light to be transmitted and another part of the light to be reflected.

[0063] It should be noted that the reflectivity and transmittance of the beam splitter 10 can be flexibly adjusted according to specific needs, and the embodiment of the present application does not limit this.

[0064] Optionally, the reflectivity of the beam splitter 10 is 47% to 53%.

[0065] Among them, the first phase retarder 9 is, for example, a quarter-wave plate. Of course, the first phase retarder 9 here can also be set to other phase retardation plates such as a half-wave plate according to needs.

[0066] In the optical module proposed in the embodiment of the present application, see Figure 1and Figure 2 In the folding optical path on the side close to the human eye 02 (aperture), by setting the first phase retarder 9, it can be used to change the polarization state of light. For example, it is used to convert linearly polarized light into circularly polarized light, or convert circularly polarized light into linearly polarized light.

[0067] Wherein, the polarization reflection element 8 is, for example, a polarization reflection film / sheet.

[0068] The polarization reflection element 8 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 this angle.

[0069] In the embodiment of the present application, the first phase retarder 9 and the polarization reflection element 8 cooperate with each other and can be used to analyze light and transmit light. Wherein, the polarization reflection element 8 has a transmission axis, and the angle between the direction of the transmission axis of the polarization reflection element 8 and the fast axis or slow axis of the first phase retarder 9 is, for example, 45°.

[0070] It should be noted that the layout positions of the three optical elements, namely the beam splitter element 10, the first phase retarder 9, and the polarization reflection element 8, between the lenses in the imaging lens group are relatively flexible and can be adjusted as needed, but it is necessary to ensure that the first phase retarder 9 is between the beam splitter element 10 and the polarization reflection element 8.

[0071] In some examples of the present application, referring to Figure 1 and Figure 2 , the first lens 3 includes a first surface 301 and a second surface 302, and the first surface 301 is a concave surface, and the second surface 302 is a convex surface. The second lens 4 includes a third surface 401 and a fourth surface 402, and both the third surface 401 and the fourth surface 402 are concave surfaces. The third lens 5 includes a fifth surface 501 and a sixth surface 502, and both the fifth surface 501 and the sixth surface 502 are convex surfaces.

[0072] According to the above examples, in the imaging lens group, the first lens 3 is, for example, a concave-convex surface type, the second lens 4 is, for example, a double concave surface type, and the third lens 5 is, for example, a double convex surface type. This method is beneficial for gluing between the three, and the size after gluing is small, that is, it is beneficial to reduce the lateral size of the optical module.

[0073] Optionally, referring to Figure 5, the second surface 302 and the third surface 401 are glued to each other so that the first lens 3 and the second lens 4 are glued together; the fourth surface 402 and the fifth surface 501 are glued to each other so that the second lens 4 and the third lens 5 are glued together. Wherein, the refractive index of the second lens 4 is 1.4 to 1.8.

[0074] Compared with the optical structure in which the second lens 4 is not arranged between the first lens 3 and the third lens 5, that is, there is an air gap between the two, when the second lens 4 (such as glue or plastic material) is introduced between the first lens 3 and the third lens 5, when the refractive index of the second lens 4 is in the range of 1.4 to 1.8, the effective aperture (2*H2) of the third lens 5 can be reduced by 5.7% to 8.5%, so that the aperture size of the third lens 5 can be reduced. Moreover, the ratio of the effective aperture (2*H2) of the third lens 5 to the effective aperture of the first lens 3 can be controlled to be (i.e., H2 / H1) 1.23 to 1.27.

[0075] In the above example of the present application, the refractive index of the second lens 4 is set within the range of 1.4 to 1.8. Within this refractive index range, the processing difficulty of the second lens 4 is relatively small, and at the same time, it can fully meet the user's requirements for imaging quality.

[0076] In some examples of the present application, see Figure 3 , the exit angle B of the light ray 01 on the surface where the second lens 4 and the first lens 3 are glued is ≤30°; wherein, the light ray 01 is the outermost light ray of the marginal field of view.

[0077] That is to say, for the optical module provided by the embodiment of the present application, by introducing a second lens 4 between the first lens 3 and the third lens 5, the exit angle B mentioned in the above example can be significantly reduced. And the exit angle B is related to the effective aperture of the third lens 5. Specifically, if the exit angle B is smaller, the effective aperture of the third lens 5 can be reduced, so that the aperture size of the third lens 5 can be reduced.

[0078] Generally speaking, when there is air between the first lens 3 and the third lens 5, the actual exit angle is the exit angle C shown in Figure 3 , and this exit angle C is obviously larger than the exit angle B. Specifically, the exit angle C is about 40°, but the exit angle B is 30° or less. Obviously, the value of the exit angle B in the present application has been reduced.

[0079] As a relatively preferred embodiment of the present application, the exit angle B is 25°. On this basis, the ratio range of the effective aperture (2*H2) of the third lens 5 to the effective aperture of the first lens 3 (i.e., H2 / H1) can be controlled to be 1.23 to 1.27. In this way, while taking into account better imaging quality, the aperture design of the third lens 5 can reach the minimum size. The volume and imaging effect of the entire optical module are optimized.

[0080] In some examples of the present application, the focal length of the optical module is 16 mm to 20 mm.

[0081] The optical module provided by the embodiment of the present application has good optical performance, and has a short focal length effect under the design of three-piece cemented lenses. It is beneficial to reduce the size of the optical module while taking into account good imaging quality.

[0082] As a relatively preferred embodiment of the present application, the focal length of the optical module is, for example, 18.4 mm, and its focal length is below 20 mm.

[0083] In some examples of the present application, referring to Figures 1 to 4 , the optical module further includes a display screen 6, and the display screen 6 is located on the side of the third lens 5 away from the second lens 4; the display screen 6 is configured to be able to emit circularly polarized light or natural light.

[0084] When the light emitted by the display screen 6 is natural light, a laminated sheet is provided on the light-emitting surface of the display screen 6, and the laminated sheet can convert the natural light emitted by the display screen 6 into circularly polarized light. Among them, the laminated sheet includes a stacked polarization element 7 and a second phase retarder 11, the polarization element 7 is provided on the display screen 6, and the second phase retarder 11 is provided on the side of the polarization element 7 away from the display screen 6.

[0085] The light entering the imaging lens group should be circularly polarized light. When the light emitted by the display screen 6 is natural light, it is necessary to first convert the polarization state of the natural light so that the natural light is first converted into circularly polarized light and then injected into the imaging lens group, so that the light finally emitted by the imaging lens group hits the human eye 02 for imaging.

[0086] Optionally, the laminated sheet includes a second phase retarder 11 and a polarization element 7. The laminated sheet is a device for converting natural light into circularly polarized light.

[0087] Optionally, a screen protection glass can be provided on the light-emitting surface of the display screen 6. At this time, the light emitted by the display screen 6 passes through the surface screen protection glass and then enters the laminated sheet for polarization state conversion of light.

[0088] Among them, the laminated sheet is, for example, a composite film. In an embodiment of the present application, it can be designed to directly mount the laminated sheet on the surface of the display screen 6 through, for example, an optical adhesive. This assembly method is simple, can reduce production costs and improve product yield.

[0089] Among them, the display screen 6 can be a self-luminous screen such as LCD, LED, OLED, Micro-OLED, ULED, etc., or a reflective screen such as DMD.

[0090] Among them, the polarization reflection element, the phase retarder and the polarization element in the optical module can be attached to a plane, a spherical surface, an aspherical surface, a cylindrical surface, a free-form surface and other forms of curved surfaces.

[0091] Optionally, the first phase retarder 9 and the second phase retarder 11 are, for example, quarter-wave plates. The first phase retarder 9 is located between the beam splitting element 10 and the polarization reflection element 8, and the transmission axis of the polarization reflection element 8 forms a 45-degree angle with the fast axis of the first phase retarder 9. The second phase retarder 11 is located between the beam splitting element 10 and the polarization element 7, and the transmission axis of the polarization element 7 forms a 45-degree angle with the fast axis of the second phase retarder 11.

[0092] Optionally, the first phase retarder 9 is disposed on the cemented surface of the second lens 4 and the third lens 5, and the polarization reflection element 8 is disposed on the cemented surface of the first lens 3 and the second lens 4; the beam splitting element 10 is disposed on the surface of the third lens 5 close to the display screen 6, and the beam splitting element 10 is located between the first phase retarder 9 and the second phase retarder 11.

[0093] That is to say, the first lens 3 and the second lens 4 are cemented together, the second lens 4 and the third lens 5 are cemented together, a polarization reflection element 8 is attached between the first lens 3 and the second lens 4, a first phase retarder 9 is attached between the second lens 4 and the third lens 5, and a beam splitting element 10 is on the surface of the third lens 5 close to the display screen 6. The polarization element 7 is attached to the surface of the display screen 6, and the second phase retarder 11 is attached to the surface of the polarization element 7 away from the display screen 6. The polarization element 7 is, for example, a linear polarizer, both the second phase retarder 11 and the first phase retarder 9 are quarter-wave plates, and the polarization reflection element 8 is a polarization reflector that reflects horizontal linearly polarized light and transmits vertical linearly polarized light.

[0094] According to the optical module provided by the above embodiment of the present application, see Figure 1 , its light propagation path is:

[0095] The light emitted by the display screen 6 becomes horizontally polarized light after passing through the polarization element 7, becomes left-handed or right-handed circularly polarized light after passing through the second phase retarder 11, becomes horizontally polarized light after passing through the beam splitter element 10, passing through the third lens 5, and passing through the first phase retarder 9, and then passes through the second lens 4; then it is reflected by the polarization reflection element 8 and becomes horizontally polarized light, then becomes left-handed or right-handed circularly polarized light after passing through the first phase retarder 9 and the second lens 4, then passes through the third lens 5, and then is reflected by the beam splitter element 10 to form right-handed or left-handed circularly polarized light, and then passes through the third lens 5, the first phase retarder 9, and the second lens 4 again to become vertically polarized light, passes through the polarization reflection element 8 and the first lens 3, and enters the human eye 02 (the aperture, see Figure 1 , located on the left side) for imaging.

[0096] In some examples of the present application, the total optical length TTL of the optical module is 16 mm to 20 mm.

[0097] The total optical length of the optical module can be less than 20 mm, featuring a small size.

[0098] As a relatively preferred embodiment of the present application, the total optical length TTL of the optical module is 18.5 mm.

[0099] In some examples of the present application, see Figure 4 , the ineffective optical regions at the edges of the first lens 3, the second lens 4, and the third lens 5 are removed to form a vacant space 2 on the outer periphery of the effective optical regions of the respective lenses.

[0100] Optionally, the optical module further includes an eye tracking lens, and the eye tracking lens is received within the vacant space 2.

[0101] For example, the ineffective regions at the edges of the lenses in the imaging lens group can be removed by CNC machining to create the above-mentioned vacant space 2. Functional devices such as an eye tracking lens can be placed within the vacant space 2.

[0102] In a specific example, see Figure 1, the optical module of the embodiment of the present application includes: a lens group, a beam splitter 10, a first phase retarder 9, and a polarization reflection element 8; the imaging lens group includes a first lens 3, a second lens 4, and a third lens 5 arranged in sequence along the same optical axis, and the first lens 3, the second lens 4, and the third lens 5 are glued together; the beam splitter 10, the first phase retarder 9, and the polarization reflection element 8 are sequentially arranged in the optical path of the imaging lens group; the optical module further includes a display screen 6, and the display screen 6 is located on the side of the third lens 5 away from the second lens 4; a laminated sheet is provided on the light-emitting surface of the display screen 6, and the laminated sheet can convert the natural light emitted by the display screen 6 into circularly polarized light; wherein, the laminated sheet includes a stacked polarization element 7 and a second phase retarder 11, the polarization element 7 is arranged on the display screen 6, and the second phase retarder 11 is arranged on the side of the polarization element 7 away from the display screen 6. Refer to Table 1, Table 1 shows Figure 1 the structural parameters of the optical module in

[0103] Table 1

[0104]

[0105] Refer to Table 1, the refractive index of the second lens 4 is 1.5, the effective aperture of the first lens 3 is 43 mm, the effective aperture of the third lens 5 is 16.8 * 2 mm, and the ratio of the effective aperture H2 of the third lens 5 to the effective aperture H1 of the first lens 3 is 1.24.

[0106] Refer to Figures 6 to 8 , these three figures are respectively the modulation transfer function MTF curves of the optical module of the embodiment of the present application at 450 nm, 540 nm, and 610 nm. 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 0.4; at a wavelength of 540 nm, the MTF value of the optical module is higher than 0.3; at a wavelength of 610 nm, the MTF of the optical module is higher than 0.3.

[0107] According to another aspect of the embodiment of the present application, there is also provided a smart wearable device, which includes a housing and the above-mentioned optical module, and the optical module is arranged in the housing.

[0108] Optionally, the smart wearable device is a VR head-mounted device, including a VR glasses or a VR helmet, etc., and the embodiment of the present application does not make specific limitations thereto.

[0109] The specific implementation manner of the smart wearable device of the embodiment of the present application can refer to the above-mentioned embodiments of the optical module, and thus has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be elaborated herein one by one.

[0110] In the above embodiments, the differences between the various embodiments are mainly described. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a more optimal embodiment. For the sake of brevity of the description, they will not be elaborated here.

[0111] 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, Comprising: An imaging lens group, which includes a first lens (3), a second lens (4), and a third lens (5) arranged in sequence along the same optical axis (1), and the first lens (3), the second lens (4), and the third lens (5) are glued together; and, A beam splitter element (10), a first phase retarder (9), and a polarization reflection element (8), which are sequentially arranged in the optical path of the imaging lens group; Wherein, the ratio of the effective aperture H2 of the third lens (5) to the effective aperture H1 of the first lens (3) is 1.23 to 1.

27.

2. The optical module according to claim 1, characterized in that, The first lens (3) includes a first surface (301) and a second surface (302), and the first surface (301) is a concave surface, and the second surface (302) is a convex surface; The second lens (4) includes a third surface (401) and a fourth surface (402), and both the third surface (401) and the fourth surface (402) are concave surfaces; The third lens (5) includes a fifth surface (501) and a sixth surface (502), and both the fifth surface (501) and the sixth surface (502) are convex surfaces.

3. The optical module according to claim 2, characterized in that, The second surface (302) and the third surface (401) are glued to each other so that the first lens (3) and the second lens (4) are glued together; the fourth surface (402) and the fifth surface (501) are glued to each other so that the second lens (4) and the third lens (5) are glued together; Wherein, the refractive index of the second lens (4) is 1.4 to 1.

8.

4. The optical module according to claim 1, wherein The exit angle B of the light ray (01) on the surface where the second lens (4) and the first lens (3) are glued is ≤30°; wherein, the light ray (01) is the outermost light ray of the marginal field of view.

5. The optical module according to any one of claims 1-4, characterized in that, The focal length of the optical module is 16 mm to 20 mm.

6. The optical module according to claim 5, wherein The optical module further includes a display screen (6), and the display screen (6) is located on the side of the third lens (5) away from the second lens (4); The display screen (6) is configured to be able to emit circularly polarized light or natural light; When the light emitted by the display screen (6) is natural light, a laminated sheet is provided on the light-emitting surface of the display screen (6), and the laminated sheet can convert the natural light emitted by the display screen (6) into circularly polarized light; wherein, the laminated sheet includes a stacked polarization element (7) and a second phase retarder (11), the polarization element (7) is provided on the display screen (6), and the second phase retarder (11) is provided on the side of the polarization element (7) away from the display screen (6).

7. The optical module according to claim 6, wherein The first phase retarder (9) and the second phase retarder (11) are quarter-wave plates; The first phase retarder (9) is located between the beam splitter element (10) and the polarization reflection element (8), and the transmission axis of the polarization reflection element (8) forms a 45-degree angle with the fast axis or the slow axis of the first phase retarder (9); The second phase retarder (11) is located between the beam splitting element (10) and the polarization element (7), and the transmission axis of the polarization element (7) forms a 45-degree angle with the fast axis or the slow axis of the second phase retarder (11).

8. The optical module according to claim 6, wherein The first phase retarder (9) is disposed on the cemented surface of the second lens (4) and the third lens (5), and the polarization reflection element (8) is disposed on the cemented surface of the first lens (3) and the second lens (4); The beam splitting element (10) is disposed on the surface of the third lens (5) close to the display screen (6), and the beam splitting element (10) is located between the first phase retarder (9) and the second phase retarder (11).

9. The optical module according to claim 6, wherein The total optical length TTL of the optical system of the optical module is 16 mm to 20 mm.

10. The optical module according to claim 1, wherein The ineffective optical regions at the edges of the first lens (3), the second lens (4) and the third lens (5) are removed to form a vacant space (2) on the outer periphery of the effective optical region of each lens.

11. The optical module according to claim 10, wherein The optical module further includes an eye tracking lens, and the eye tracking lens is received in the vacant space (2).

12. An intelligent wearable device, characterized in that, Comprising: A housing; And The optical module according to any one of claims 1-11, wherein the optical module is disposed in the housing.

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