Folding optical path lens group, optical imaging module and head-mounted display equipment

Abstract

The embodiment of the utility model discloses a folded optical path lens group, an optical imaging module and head-mounted display equipment. According to the embodiment of the utility model, a first lens and a second lens are arranged in a folded light path lens group, and the four surfaces of the two lenses from a light inlet surface to a light outlet surface are a first convex curved surface and a second concave curved surface of the first lens, and a third convex curved surface and a fourth plane of the second lens in sequence; wherein the curvatures of the first convex curved surface, the second concave curved surface and the third convex curved surface are sequentially reduced, so that a structure with a thick middle part and a thin periphery is formed on the first lens, and only one curved surface is formed on the second lens, thereby simplifying the structure and reducing the processing cost.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of display technology, and in particular to a folded optical path lens, an optical imaging module, and a head-mounted display device. Background Art

[0002] With the continuous development of electronic related technologies, display and display technologies and display devices derived from display are constantly emerging, such as AR (Augmented Reality) devices and VR (Virtual Reality) devices such as Pancake, which are display devices derived from display. The device form of these derived display devices is usually head-mounted display devices.

[0003] In the head-mounted display device, the optical imaging module obtained by combining optical parts such as optical resin lenses, optical glass lenses, optical films, optical coatings and display units can amplify the image source presented in the display unit and form a virtual image at a certain distance from the display unit. When the virtual image falls exactly on the retina, the user can feel the imaging effect of the head-mounted display device through vision.

[0004] The inventors studied existing head-mounted display devices and found that the folded light path mirror group is a key component in the head-mounted display device for users to view the image source. The lens in the folded light path mirror group, whose shape is determined by the concave and convex surfaces on both sides, has a relatively complex structure and a high processing cost. Utility Model Content

[0005] The utility model provides a folded light path lens, an optical imaging module and a head-mounted display device, so as to solve the technical problem that the lens in the folded light path lens group of the head-mounted display device is constrained by concave and convex surfaces on both sides to determine the shape, has a relatively complex structure and a high processing cost.

[0006] In the first aspect, an embodiment of the present application provides a folding light path mirror group, which includes a first lens and a second lens, the first lens is located on the light incident side of the folding light path mirror group, and the second lens is located on the light exit side of the folding light path mirror group, a first convex surface and a second concave surface are respectively provided on both sides of the first lens, a third convex surface and a fourth plane are respectively provided on both sides of the second lens, the first convex surface, the second concave surface, the third convex surface and the fourth plane are arranged in sequence along the optical axis, and the curvatures of the first convex surface, the second concave surface and the third convex surface decrease in sequence; a second 1 / 4 wave plate is provided at the fourth plane.

[0007] As described above, a first lens and a second lens are arranged in the folded optical path lens group, and the four surfaces of the two lenses from the light incident surface to the light exiting surface are, in sequence, a first convex surface and a second concave surface of the first lens, a third convex surface and a fourth plane surface of the second lens, wherein the curvatures of the first convex surface, the second concave surface and the third convex surface decrease in sequence, thereby forming a structure in which the first lens is thick in the middle and thin around, and the second lens has only one curved surface, thereby simplifying the structure and reducing the processing cost.

[0008] Wherein, a semi-reflective and semi-transparent film is also arranged at the first convex surface, a reflective polarizer is also arranged at the fourth plane, and the second lens and the reflective polarizer are arranged in sequence along the optical axis.

[0009] The above-mentioned surface structure and combination of the first lens and the second lens are adapted to provide an imaging picture with better resolution and enhance the user's visual experience by arranging a semi-reflective and semi-transparent film, a second quarter-wave plate and a reflective polarizer at specific positions.

[0010] Among them, the first convex surface, the second concave surface and the third convex surface are all aspherical surfaces.

[0011] As mentioned above, the aspherical first lens and the second lens have a rich variety of surface selection variations, so that more detailed changes can be made according to specific display index requirements, and the thickness of the lens can be precisely controlled, thereby minimizing the volume, weight and thickness of the entire optical imaging module while improving the imaging quality.

[0012] Among them, the expressions of the aspheric surface types of the first convex surface, the second concave surface, and the third convex surface are:

[0013]

[0014] Among them, z is the aspheric surface height, r is the radius of the aspheric surface, k is the quadratic surface coefficient, c is the curvature, A 4 ~A 16 is the high-order coefficient of the aspheric surface.

[0015] As described above, by designing a specific aspheric surface shape, the curvature of the concave and convex surfaces appearing in the first lens and the convex surface appearing in the second lens can be effectively controlled, thereby effectively controlling distortion.

[0016] Wherein, the thickness of the first lens and / or the second lens is 1-3 mm.

[0017] As described above, with a lens thickness of 1 to 3 mm, a good imaging effect can be achieved with an optical device that is as small and light as possible.

[0018] In a second aspect, an embodiment of the present application further provides an optical imaging module using any one of the folding light path mirror groups in the first aspect, the optical imaging module comprising a display unit, a first 1 / 4 wave plate and a folding light path mirror group coaxially arranged in sequence, the display unit, the first 1 / 4 wave plate and the folding light path mirror group being arranged in sequence along the optical axis;

[0019] The included angle between the fast axis direction of the first 1 / 4 wave plate and the fast axis direction of the second 1 / 4 wave plate is 90°.

[0020] As described above, by using two lenses with specific surface states, and other optical devices selected and arranged corresponding to the surface states of the two lenses, the structure of the optical imaging module can be simplified and the overall processing cost can be reduced. While ensuring that the weight of the optical imaging module is as small as possible and the cost is as low as possible, the light emitted from the display unit is polarized, refracted and reflected multiple times, so that ultimately an imaging picture with good resolution enters the user's retina, and the user can have a good visual experience.

[0021] Wherein, the optical imaging module further comprises an absorbing polarizer, which is arranged on a side of the reflective polarizer facing away from the second quarter wave plate; or

[0022] The absorbing polarizer is disposed between the display unit and the first quarter wave plate.

[0023] As described above, by disposing the absorption polarizer at the light exit position or the image source position, the stray light output from the optical imaging module is effectively reduced, and the contrast of the entire display screen is further improved.

[0024] Among them, the aperture of the optical imaging module is 43mm~50mm.

[0025] As described above, by mirroring the size of the optical device at 43 mm to 50 mm, the overall size of the optical imaging module can be controlled as much as possible without affecting the user's visual experience.

[0026] In a third aspect, an embodiment of the present application provides a head-mounted display device, which includes any optical imaging module of the second aspect.

[0027] As described above, the head mounted display device manufactured using any one of the optical imaging modules in the second aspect has the same beneficial effects as the optical imaging module. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of the optical imaging module provided in an embodiment of the present application.

[0029] Figure 2 A graph showing the field curvature and distortion simulation results of the optical imaging module provided in an embodiment of the present application.

[0030] Figure 3 A schematic diagram of the light propagation process of the optical imaging module provided in an embodiment of the present application.

[0031] Among them, 10 is a display unit; 11 is a first quarter wave plate; 20 is a first lens; 21 is a semi-reflective and semi-transparent surface; 30 is a second lens; 31 is an absorption polarizer; 32 is a reflection polarizer; 33 is a second quarter wave plate; and 40 is a retina. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0033] It should be noted that due to space limitations, this application description does not list all optional implementation methods. After reading this application description, those skilled in the art should be able to understand that as long as the technical features do not contradict each other, any combination of technical features can constitute an optional implementation method.

[0034] The following is a detailed description of the various embodiments of the present invention.

[0035] The inventor studied the existing head-mounted display devices and found that the folding light path mirror group is a key component for the user to view the image source in the head-mounted display device. The lens in the folding light path mirror group, whose shape is determined by the concave and convex surfaces on both sides, has a relatively complex structure and high processing cost. For example, it is necessary to set two or more lenses in the folding light path mirror group, and the surface state of each lens needs to be designed and processed. Moreover, as an electronic device with dual user experience of visual experience and wearing experience, the more lenses in the folding light path mirror group and the more complex the structure, the heavier the head-mounted display device finally assembled and produced will be. If the user uses it for a long time, the neck will be quite tired, and the user's overall user experience will be poor.

[0036] In response to the above technical problems, an embodiment of the present application provides a folded light path mirror group, in which a first lens and a second lens are arranged in the folded light path mirror group, and the four surfaces of the two lenses from the light incident surface to the light exit surface are, in sequence, a first convex surface and a second concave surface of the first lens, a third convex surface and a fourth plane surface of the second lens, wherein the curvatures of the first convex surface, the second concave surface and the third convex surface decrease in sequence, thereby forming a structure in which the first lens is thick in the middle and thin on all sides, and the second lens has only one curved surface, which simplifies the structure and reduces the processing cost.

[0037] Please refer to Figure 1, which is a schematic diagram of the overall structure when the folded light path lens provided in the embodiment of the present application is applied to an optical imaging module. Figure 1 As shown, the folding light path mirror group includes a first lens 20 and a second lens 30, the first lens 20 is located on the light incident side of the folding light path mirror group, the second lens 30 is located on the light exit side of the folding light path mirror group, a first convex surface and a second concave surface are respectively provided on both sides of the first lens 20, a third convex surface and a fourth plane are respectively provided on both sides of the second lens 30, the first convex surface, the second concave surface, the third convex surface and the fourth plane are arranged in sequence along the optical axis, and the curvatures of the first convex surface, the second concave surface and the third convex surface decrease in sequence; a second 1 / 4 wave plate 33 is provided at the fourth plane.

[0038] A first lens 20 and a second lens 30 are arranged in the folded optical path lens group, and the four surfaces of the two lenses from the light-entering surface to the light-exiting surface are the first convex surface and the second concave surface of the first lens 20, the third convex surface and the fourth plane of the second lens 30, wherein the curvatures of the first convex surface, the second concave surface and the third convex surface decrease successively, wherein the curvature relationship between the first convex surface and the second concave surface can form a structure in which the first lens 20 is thick in the middle and thin around, and the second lens 30 has only one curved surface, thereby simplifying the structure and reducing the processing cost. Moreover, the curvature relationship between the second concave surface and the third convex surface can also make the third convex surface as close to the second concave surface as possible, thereby reducing the overall distance between the first lens 20 and the second lens 30, and controlling the installation size as much as possible. In the embodiment of the present application, Figure 1 The image shown and the position of the retina 40 of the human eye are used as references. From right to left along the optical axis, the light-entering surface is correspondingly on the right, and the light-exiting surface is correspondingly on the left.

[0039] The folded optical path mirror group in the embodiment of the present application can also be provided with a semi-reflective and semi-transparent film at the first convex surface, a reflective polarizer 32 at the fourth plane, and the second lens 30, the second 1 / 4 wave plate 33 and the reflective polarizer 32 are arranged in sequence along the optical axis.

[0040] As described above, adapted to the surface structure and combination of the first lens 20 and the second lens 30, a semi-reflective and semi-transparent film, a second 1 / 4 wave plate 33 and a reflective polarizer 32 are arranged at specific positions, which can provide an imaging picture with better resolution and enhance the user's visual experience.

[0041] In another optional implementation, the first convex surface, the second concave surface and the third convex surface are all aspherical surfaces. The aspherical first lens 20 and the second lens 30 have a rich variety of surface selections, so that more detailed changes can be made according to specific display index requirements, and the lens thickness can be precisely controlled, thereby reducing the volume, weight and thickness of the entire optical imaging module as much as possible, while improving the imaging quality.

[0042] In a specific implementation, the aspheric surface shapes of the first convex surface, the second concave surface, and the third convex surface are expressed as follows:

[0043]

[0044] Among them, z is the aspheric surface height, r is the radius of the aspheric surface, k is the quadratic surface coefficient, c is the curvature (the inverse of the curvature radius), A 4 ~A 16 By designing a specific aspheric surface shape, the curvature of the concave and convex surfaces in the first lens 20 and the convex surface in the second lens 30 can be effectively controlled, thereby effectively controlling distortion.

[0045] In a specific implementation detail, the thickness of the first lens 20 and / or the second lens 30 is 1-3 mm.

[0046] As described above, with a lens thickness of 1 to 3 mm, a good imaging effect can be achieved with an optical device that is as small and light as possible.

[0047] In another specific implementation detail, the first lens 20 is a resin lens or a glass lens, and the second lens 30 is a resin lens or a glass lens. For example, the first lens 20 and the second lens 30 are both resin lenses, the first lens 20 and the second lens 30 are different types of resin lenses and glass lenses, and the first lens 20 and the second lens 30 are both glass lenses. Taking the example that the first lens 20 and the second lens 30 are both resin lenses, because the density of resin is lower than that of glass, the first lens 20 and the second lens 30 are both resin lenses, which can control the overall structural weight to the greatest extent possible. Moreover, the processing of concave and convex surfaces of resin lenses is relatively easy, and the overall processing cost can also be better controlled.

[0048] The imaging process of the folded light path lens in the embodiment of the present application is described in detail in the corresponding embodiment when the folded light path lens is applied to the optical imaging module.

[0049] In the embodiment corresponding to the optical imaging module, compared with the folded light path lens group, it also includes at least a display unit and a first 1 / 4 wave plate, wherein the first 1 / 4 wave plate is arranged at the light exit position of the display unit, and the light of the image source displayed by the display unit enters the folded light path lens from the light entrance surface through the first 1 / 4 wave plate, and enters the user's retina for imaging after exiting from the light exit surface. Corresponding to the specific implementation method in the folded light path lens group, the optical imaging module can have implementation methods corresponding to the layout of the display unit and the first 1 / 4 wave plate respectively, and in any implementation method, an absorption polarizer can be added (corresponding to different position settings), and the aperture of the optical imaging module can be further designed as a whole, for example, the size is designed within the aperture range of 43mm to 50mm.

[0050] Please refer to Figure 1 , which is a schematic diagram of the structure of the optical imaging module provided in the embodiment of the present application. Figure 1 In the overall embodiment design of the folded optical path mirror assembly mentioned above, the optical imaging module is described in detail. Figure 1 As shown, the optical imaging module in the embodiment of the present application includes a display unit 10, a first quarter wave plate 11, and a folded light path lens in the previous embodiment (correspondingly including a first lens 20, a second lens 30, and a second quarter wave plate 33) which are coaxially arranged in sequence, and a reflective polarizer 32; the surface of the first lens 20 facing the first quarter wave plate 11 is a convex surface (i.e., a first convex surface) and is provided with a semi-reflective and semi-transparent film ( Figure 1 The surface of the first lens 20 facing the second lens 30 is a concave surface (i.e., a second concave surface); the surface of the second lens 30 facing the first lens 20 is a convex surface (i.e., a third convex surface); the surface of the second lens 30 facing the second 1 / 4 wave plate 33 is a plane (i.e., a fourth plane); the fast axis direction of the first 1 / 4 wave plate 11 and the fast axis direction of the second 1 / 4 wave plate 33 are at an angle of 90°.

[0051] like Figure 1As shown, when the display unit 10 is used as an image source for imaging, the outgoing light (s-polarized light) passes through the first 1 / 4 wave plate 11, the first lens 20, the second lens 30 and the second 1 / 4 wave plate 33 in sequence. Since the angle between the fast axis direction of the first 1 / 4 wave plate 11 and the fast axis direction of the second 1 / 4 wave plate 33 is 90°, the polarization state of the s-polarized light will not be changed and it is still s-polarized light; then the s-polarized light is reflected by the reflective polarizer 32 (the reflective polarizer 32 can reflect s-polarized light and transmit p-polarized light), and then passes through the second 1 / 4 wave plate 33 and the first lens 20 in sequence. Since the right surface of the first lens 20 is coated with a semi-reflective and semi-transmissive film, a part of the light is reflected by the right surface of the first lens 20, and then passes through the first lens 20 and the second 1 / 4 wave plate 33 in sequence. At this time, the s-polarized light is converted into p-polarized light, which can pass through the reflective polarizer 32 and enter the retina 40 (the position of the human eye).

[0052] As described above, by using two lenses with specific surface states, and other optical devices selected and arranged corresponding to the surface states of the two lenses, the structure of the optical imaging module can be simplified and the overall processing cost can be reduced. While ensuring that the weight of the optical imaging module is as small as possible and the cost is as low as possible, the light emitted from the display unit is polarized, refracted and reflected multiple times, so that ultimately an imaging picture with good resolution enters the user's retina, and the user can have a good visual experience.

[0053] In an optional implementation, the optical imaging module further includes an absorbing polarizer, which is arranged on a side of the reflective polarizer that is away from the second quarter wave plate.

[0054] Please refer to further Figure 1 , the outgoing light (s-polarized light) of the display unit 10 passes through the first 1 / 4 wave plate 11, the first lens 20, the second lens 30, and the second 1 / 4 wave plate 33 in sequence. Since the angle between the fast axis direction of the first 1 / 4 wave plate 11 and the fast axis direction of the second 1 / 4 wave plate 33 is 90°, the polarization state of the s-polarized light will not be changed and it is still s-polarized light; then the s-polarized light is reflected by the reflective polarizer 32 (the reflective polarizer 32 can reflect s-polarized light and transmit p-polarized light), and then passes through the second 1 / 4 wave plate 11, the first lens 20, the second lens 30, and the second 1 / 4 wave plate 33 in sequence. / 4 wave plate 33, first lens 20. Since the right surface of the first lens 20 is coated with a semi-reflective and semi-transmissive film, part of the light is reflected by the right surface of the first lens 20, and then passes through the first lens 20 and the second 1 / 4 wave plate 33 in sequence. At this time, the s-polarized light is converted into p-polarized light, which can pass through the reflective polarizer 32 and the absorptive polarizer 31 (the transmission axis direction of the absorptive polarizer 31 is the same as the polarization direction of the p-polarized light), and finally passes through the absorptive polarizer 31 into the retina 40 (where the human eye is located).

[0055] In the embodiment of the present application, the propagation direction and polarization direction of the light are as follows: Figure 3 As shown. The display unit 10 emits s-polarized light, whose polarization direction is perpendicular to the paper surface. After passing through the first 1 / 4 wave plate 11, it is converted into left-handed circularly polarized light, and then passes through the semi-reflective and semi-transparent surface 21 (the right surface of the first lens 20 is defined as the semi-reflective and semi-transparent surface 21 because the semi-reflective and semi-transparent film has a 50% energy loss), and then passes through the second 1 / 4 wave plate 33 to be converted into s-polarized light (because the angle between the fast axis direction of the first 1 / 4 wave plate 11 and the fast axis direction of the second 1 / 4 wave plate 33 is 90°, the phase difference of the two 1 / 4 wave plates cancels each other out). The reflective polarizer 32 reflects the s-polarized light, and then passes through the second 1 / 4 wave plate 33 to be converted into right-handed circularly polarized light, and then is reflected by the semi-reflective and semi-transparent surface 21 (energy loss is 50% again), and then passes through the second 1 / 4 wave plate 33 again to be converted into p-polarized light, and passes through the reflective polarizer 32 and the absorptive polarizer ( Figure 3 The image is not shown in the figure) and finally enters the human eye for imaging.

[0056] The semi-reflective and semi-transparent surface 21 of the first lens 20 is coated with a semi-reflective and semi-transparent film. When the light emitted by the display unit 10 passes through the surface, there will be a 50% energy loss. When the light is reflected by the surface, there will also be a 50% energy loss. Therefore, in theory, the energy utilization rate of the optical imaging module is 25%. In fact, the reflectivity of the reflective polarizer 32 to s-polarized light is not 100%, so a small amount of s-polarized light will pass through. The absorbing polarizer 31 can just absorb the transmitted s-polarized light, which can reduce the stray light of the system and improve the contrast of the entire display screen.

[0057] The simulation results of field curvature and distortion of the optical imaging module at this time are as follows: Figure 2 As shown, the vertical coordinates of field curvature and distortion are the field angle, the maximum field angle is 100 degrees, the horizontal coordinate unit of field curvature is millimeters, and the horizontal coordinate unit of distortion is percentage. At this time, it is obvious that there is a good field angle, and the distortion is effectively controlled.

[0058] As described above, by setting the absorption polarizer at the light output position, the stray light finally output from the optical imaging module can be effectively reduced, and the contrast of the entire display screen can be further improved. For example, when the screen content is black background with white text, it can provide users with a clearer imaging effect, and the boundary between black and white is clearer.

[0059] In another optional implementation, the optical imaging module also includes an absorption polarizer, which is arranged between the display unit 10 and the first quarter wave plate 11. This method is more suitable for the case where the display unit 10 emits natural light (i.e., non-polarized light). At this time, an absorption polarizer is added between the display unit 10 and the first quarter wave plate 11 (the transmission axis direction of the absorption polarizer is the same as the polarization direction of the s-polarized light, i.e., the direction perpendicular to the paper surface). The absorption polarizer polarizes the non-polarized light emitted by the display unit 10 to obtain s-polarized light. By setting the absorption polarizer at the image source position, stray light can be processed from the image source, thereby ultimately controlling the stray light output from the optical imaging module, and further improving the contrast of the entire display screen. For example, when the screen content is black background and white text, it can provide users with a clearer imaging effect, and the boundary between black and white is clearer.

[0060] In a specific implementation, one or more of the surface of the first lens facing the second lens, the surface of the first lens facing the first quarter wave plate, and the surface of the second lens facing the first lens are aspherical. The aspherical first lens and the second lens have a rich variety of surface selections, so that more detailed changes can be made according to specific display index requirements, and the lens thickness can be precisely controlled, thereby reducing the volume, weight and thickness of the entire optical imaging module as much as possible, while improving the imaging quality.

[0061] In a more specific implementation, the expression of the aspheric surface shape is:

[0062]

[0063] Among them, z is the aspheric surface height, r is the radius of the aspheric surface, k is the quadratic surface coefficient, c is the curvature (the inverse of the curvature radius), A 4 ~A 16 is the high-order coefficient of the aspheric surface.

[0064] As described above, by designing a specific aspheric surface shape, the curvature of the concave and convex surfaces appearing in the first lens and the convex surface appearing in the second lens can be effectively controlled, thereby effectively controlling distortion.

[0065] In terms of the specific hardware type selection, the display unit is a FastLCD display. Using a FastLCD display as a display unit can ensure the imaging refresh speed of the image source and improve the imaging effect provided to the user. Regardless of which type of display is selected, the display unit can be a 2.56-inch display. The 2.56-inch display can ensure the field of view of the entire optical imaging module.

[0066] In a specific implementation detail, the thickness of the first lens and / or the second lens may be 1-3 mm, for example, 1.7 mm, 2 mm. With a lens thickness of 1-3 mm, a good imaging effect can be achieved with an optical device that is as small and light as possible.

[0067] In another specific implementation detail, the aperture of the optical imaging module may be 43 mm to 50 mm, such as 44 mm, 47 mm, etc. With an optical device size of 43 mm to 50 mm, the overall size of the optical imaging module may be controlled as much as possible without affecting the user's visual experience.

[0068] The embodiment of the present application also provides a head-mounted display device, which includes the optical imaging module as described in any of the previous embodiments, and the head-mounted display device is an AR device, a VR device such as Pancake, etc. The head-mounted display device in the embodiment of the present application has the technical effects corresponding to the embodiment of the optical imaging module in the previous text.

[0069] In an optional implementation, for two display units 10 in a head-mounted display device, the angle of the display unit 10 is adjusted to achieve the misaligned and differentiated display of the left eye and the right eye, so as to increase the horizontal viewing angle and the vertical viewing angle. For example, when the display unit 10 is facing the user's retina 40, the viewing distance is 46mm, and the angle of the display unit 10 is rotated 23°, then the viewing distance reaches 51.94mm, and the adjustment of the viewing angle is achieved from the user's experience. Overall, through a rotation of 19° to 25°, the viewing angle can be flexibly adjusted to correspond to different users.

[0070] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0071] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. Folding optical path mirror set, It is characterized in that The invention comprises a first lens (20) and a second lens (30), wherein the first lens (20) is located at a light-incoming surface side of the folding light path lens assembly, and the second lens (30) is located at a light-outgoing surface side of the folding light path lens assembly, and the first lens (20) is provided with a first convex surface and a second concave surface on both sides, and the second lens (30) is provided with a third convex surface and a fourth plane on both sides, and the first convex surface, the second concave surface, the third convex surface and the fourth plane are arranged in sequence along the optical axis, and the curvatures of the first convex surface, the second concave surface and the third convex surface decrease in sequence; A second quarter wave plate (33) is provided at the fourth plane.

2. The folded light path lens assembly according to claim 1, It is characterized in that A semi-reflective and semi-transparent film is also provided at the first convex surface, a reflective polarizer (32) is also provided at the fourth plane, and the second lens (30), the second quarter wave plate (33) and the reflective polarizer (32) are arranged in sequence along the optical axis.

3. The folded light path lens assembly according to claim 1, It is characterized in that The first convex curved surface, the second concave curved surface and the third convex curved surface are all aspherical surfaces.

4. The folded light path lens assembly according to claim 3, It is characterized in that The expressions of the aspheric surface types of the first convex surface, the second concave surface, and the third convex surface are: Among them, z is the aspheric surface height, r is the radius of the aspheric surface, k is the quadratic surface coefficient, c is the curvature, A 4 ~A 16 is the high-order coefficient of the aspheric surface.

5. The folded light path lens assembly according to claim 1, It is characterized in that The thickness of the first lens (20) and / or the second lens (30) is 1 to 3 mm.

6. The folded light path lens assembly according to claim 1, It is characterized in that The first lens (20) is a resin lens or a glass lens, and the second lens (30) is a resin lens or a glass lens.

7. An optical imaging module using the folded light path lens assembly according to any one of claims 1 to 6, It is characterized in that It comprises a display unit (10), a first quarter wave plate (11) and a folding light path lens group which are coaxially arranged in sequence; The display unit (10), the first quarter wave plate (11) and the folding light path lens group are arranged in sequence along the optical axis; The included angle between the fast axis direction of the first 1 / 4 wave plate (11) and the fast axis direction of the second 1 / 4 wave plate (33) is 90°.

8. The optical imaging module according to claim 7, It is characterized in that Also includes an absorbing polarizer (31); A semi-reflective and semi-transmissive film is also provided at the first convex curved surface, a reflective polarizer (32) is also provided at the fourth plane, the second lens (30), the second quarter-wave plate (33) and the reflective polarizer (32) are arranged in sequence along the optical axis, and the absorptive polarizer (31) is arranged on a side of the reflective polarizer (32) that is away from the second quarter-wave plate (33); or The absorption polarizer (31) is arranged between the display unit (10) and the first quarter wave plate (11).

9. The optical imaging module according to claim 7, It is characterized in that The caliber of the optical imaging module is 43 mm to 50 mm.

10. Head-mounted display devices, It is characterized in that The head-mounted display device includes the optical imaging module as described in any one of claims 7-9.

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