Optical modules and head-mounted display devices

Abstract

This application provides an optical module and a head-mounted display device. The optical module includes a lens group, a beam splitter, a first phase retarder, and a polarizing reflector disposed between the optical paths of the lens group. The first phase retarder is located between the beam splitter and the polarizing reflector. The lens group consists of a first lens and a second lens bonded together, with the first and second lenses arranged adjacent to each other along the same optical axis. The ratio H / T2 of the height H of the second lens away from the surface of the first lens to the center thickness T2 of the second lens satisfies: 0.38 ≤ H / T2 ≤ 0.82. The optical module provided in this application has the characteristics of small overall length and good image quality.

Description

Technical Field

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

[0002] The core component of virtual reality (VR) technology is the internal optical module, and the quality of its displayed image directly determines the quality of the VR product. As people's demands for wearing comfort in VR products increase, there is a growing requirement for thinner and lighter designs. However, existing optical modules used in VR products cannot maintain image quality within a small footprint. Therefore, miniaturization of the optical module is not feasible to ensure image quality. 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 features a small overall length of the optical module and good image quality.

[0004] In a first aspect, this application provides an optical module. The optical module includes a lens group, a beam splitter, a first phase retarder, and a polarizing reflector disposed between the optical paths of the lens group, wherein the first phase retarder is located between the beam splitter and the polarizing reflector;

[0005] The lens group consists of a first lens and a second lens bonded together, with the first lens and the second lens arranged adjacent to each other along the same optical axis;

[0006] The ratio H / T2 of the sagitta of the second lens away from the surface of the first lens to the center thickness T2 of the second lens satisfies: 0.38≤H / T2≤0.82.

[0007] Optionally, the surface of the second lens adjacent to the first lens is a concave surface or a curved surface;

[0008] The surfaces adjacent to the first lens and the second lens are convex or curved surfaces.

[0009] Optionally, the surface of the second lens facing away from the first lens is convex.

[0010] Optionally, the optical module further includes a display screen located on the side of the second lens opposite to the first lens, and the ratio T2 / L of the center thickness T2 of the second lens to the aperture L of the light-emitting area of ​​the display screen satisfies: 0.2≤T2 / L≤0.5.

[0011] Optionally, the total length TTL of the optical module is less than 25 mm, and the MTF value of the optical module is greater than 0.5.

[0012] Optionally, the effective focal length of the optical module is 13mm to 23mm.

[0013] Optionally, the beam-splitting element is disposed on the surface of the second lens near the display screen;

[0014] The first phase retarder is disposed on the surface of the second lens away from the display screen, and the polarizing reflector is superimposed on the side of the first phase retarder opposite to the second lens.

[0015] Optionally, the optical module further includes a first polarizer, which is disposed on the side of the polarizing reflector opposite to the first phase retarder;

[0016] Furthermore, the first polarizer is bonded to the first lens via an adhesive layer.

[0017] Optionally, the display screen is configured to emit circularly polarized light or natural light;

[0018] When the light emitted by the display screen is natural light, a second polarizer is provided on the light-emitting surface of the display screen, and a second phase delayer is superimposed on the side of the second polarizer away from the display screen. The second polarizer and the second phase delayer form a superimposed element to convert natural light into circularly polarized light.

[0019] Optionally, the beam splitter is located between the first phase delayer and the second phase delayer.

[0020] Secondly, this application provides a head-mounted display device. The head-mounted display device includes:

[0021] Casing; and

[0022] The optical module as described in the first aspect.

[0023] The beneficial effects of this application are as follows:

[0024] According to the embodiments of this application, the optical module is a folded optical path scheme. The optical module has a cemented lens group, which is composed of two lenses. By designing the surface shape and center thickness parameters of the second lens, the total length of the optical module can be reduced while maintaining image quality.

[0025] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0027] Figure 1 This is a schematic diagram of the structure of an optical module provided in an embodiment of this application;

[0028] Figure 2 for Figure 1 One of the modulation transfer function (MTF) curves of the optical module is shown;

[0029] Figure 3 for Figure 1 The second example of the modulation transfer function (MTF) curve of the optical module is shown.

[0030] Figure 4 for Figure 1 The third example of the modulation transfer function (MTF) curve of the optical module is shown.

[0031] Figure 5 This is a schematic diagram of another optical module provided in an embodiment of this application;

[0032] Figure 6 for Figure 5 One of the modulation transfer function (MTF) curves of the optical module is shown;

[0033] Figure 7 for Figure 5 The second example of the modulation transfer function (MTF) curve of the optical module is shown.

[0034] Figure 8 for Figure 5 The third example of the modulation transfer function (MTF) curve of the optical module is shown.

[0035] Figure 9 This is a schematic diagram of the structure of another optical module provided in an embodiment of this application;

[0036] Figure 10 for Figure 9 One of the modulation transfer function (MTF) curves of the optical module is shown;

[0037] Figure 11 for Figure 9 The second example of the modulation transfer function (MTF) curve of the optical module is shown.

[0038] Figure 12 for Figure 9 The third example shows the modulation transfer function (MTF) curve of the optical module.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1. Optical axis; 2. Aperture; 3. First lens; 4. Second lens; 5. Display screen; 6. Light beam; 7. Adhesive layer; 8. First polarizer; 9. Polarizing reflector; 10. First phase retarder; 11. Beam splitter; 12. Second phase retarder; 13. Second polarizer. Detailed Implementation

[0041] 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 arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0042] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0043] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0044] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0045] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0046] The optical module and head-mounted display device provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0047] According to one aspect of the embodiments of this application, an optical module is provided, which is suitable for application in wearable devices. The wearable device is, for example, a head-mounted display (HMD), such as a VR head-mounted display. The VR head-mounted display includes, for example, VR smart glasses or VR smart helmets, and the embodiments of this application do not limit the specific form of the head-mounted display device.

[0048] The optical module proposed in this application embodiment is described in [reference]. Figure 1 , Figure 5 and Figure 9As shown, the optical module includes a lens group, a beam splitter 11, a first phase retarder 10, and a polarizing reflector 9 disposed between the optical paths of the lens group. The first phase retarder 10 is located between the beam splitter 11 and the polarizing reflector 9. The lens group consists of a first lens 3 and a second lens 4 cemented together, with the first lens 3 and the second lens 4 arranged adjacent to each other along the same optical axis 1. The ratio H / T2 of the height H of the surface of the second lens 4 facing away from the first lens 3 to the center thickness T2 of the second lens 4 satisfies: 0.38 ≤ H / T2 ≤ 0.82.

[0049] The optical module provided in the above embodiments of this application is an optical module based on a folded optical path (pancake), which can be applied to virtual reality products such as VR products.

[0050] According to the optical module provided in the above embodiment, a cemented lens group consisting of two lenses is introduced, that is, a lens group is formed by cementing the first lens 3 and the second lens 4 together. The design of two cemented lenses helps to reduce the overall length of the optical module. At the same time, in order to ensure good image quality, this application also designs the ratio H / T2 of the sagitta of the surface of the second lens 4 away from the first lens 3 to the center thickness T2 of the second lens 4 to satisfy the relationship: 0.38≤H / T2≤0.82. In this way, good image quality can be achieved while ensuring a small overall length of the optical module.

[0051] When the ratio H / T2 of the height H of the second lens 4 away from the surface of the first lens 3 to the center thickness T2 of the second lens 4 is less than 0.38 or greater than 0.82, it is impossible to achieve both image quality and imaging quality, which will reduce the image quality.

[0052] The optical module proposed in this application embodiment facilitates the achievement of high imaging quality requirements in virtual reality display devices, such as VR devices, while maintaining a small size. The small size of the optical module allows for a more compact design, enabling the virtual reality display device to be thinner and lighter, making it more suitable for user wear and improving comfort, reducing fatigue even after prolonged use.

[0053] The optical module provided in the embodiments of this application is a folded optical path scheme. The optical module has a cemented lens assembly, which consists of two lenses. By designing the surface shape and center thickness parameters of the second lens 4, the overall length of the optical module can be reduced while maintaining image quality. The second lens 4 is, for example, close to the display screen 5, see [reference needed]. Figure 1 .

[0054] The optical module provided in this application embodiment is a folded optical path. In addition to a lens group, the optical module also includes optical elements such as a beam splitter 11, a first phase retarder 10, and a polarizing reflector 9 for forming the folded optical path. These optical elements (optical films) can be used to form a folded optical path within the lens group, allowing light to be refracted within it, thereby extending the propagation path of the light. This is beneficial for achieving a clear final image and also helps to reduce the size of the entire optical module.

[0055] The beam splitter 11 allows a portion of the light to be transmitted and another portion to be reflected.

[0056] The beam splitter 11 is, for example, a semi-transparent and semi-reflective film.

[0057] Optionally, the reflectivity of the beam splitter 11 is 47% to 53%.

[0058] It should be noted that the reflectivity and transmittance of the beam splitter 11 can be flexibly adjusted according to specific needs, and this application embodiment does not impose any restrictions on this.

[0059] The first phase delayer 10 is, for example, a quarter-wave plate.

[0060] Of course, the first phase delay unit 10 here can also be set to other phase delay plates such as half-wave plates as needed.

[0061] In the optical module proposed in this application embodiment, the first phase delayer 10 is provided in the folded optical path located near the aperture 2 to change the polarization state of light. For example, it can be used to convert linearly polarized light into circularly polarized light, or circularly polarized light into linearly polarized light.

[0062] The polarizing reflector 9 is, for example, a linear polarizer, which is a polarizing reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or any other polarizing reflector that reflects linearly polarized light at a specific angle and transmits linearly polarized light in a direction perpendicular to that angle.

[0063] In the embodiments of this application, the first phase delayer 10 and the polarizing reflector 9 work together to resolve light and transmit it.

[0064] It should be emphasized that the optical elements such as the beam splitter 11, the first phase delayer 10, and the polarizing reflector 9 can form a folded optical path within the lens group on the near stop 2 side. The arrangement of the above-mentioned optical elements is relatively flexible, but it is necessary to ensure that the first phase delayer 10 is located between the beam splitter 11 and the polarizing reflector 9.

[0065] See some examples in this application. Figure 1 , Figure 5 and Figure 9 The surface of the second lens 4 adjacent to the first lens 3 is concave or curved. The surface of the first lens 3 adjacent to the second lens 4 is convex or curved.

[0066] According to the above example, the two adjacent surfaces of the first lens 3 and the second lens 4 need to be glued together. The glued surfaces of the first lens 3 and the second lens 4 are designed to be concave-convex or concave-convex, or to be curved, which facilitates the glued assembly between the two.

[0067] See some examples in this application. Figure 1 , Figure 5 and Figure 9 The surface of the second lens 4 that faces away from the first lens 3 is convex.

[0068] In the optical module provided in this application embodiment, the second lens 4 is close to the display screen 5. Since the lens group in the entire optical module is only composed of the first lens 3 and the second lens 4 bonded together, the second lens 4 is the first lens close to the display screen 5. The surface of the second lens 4 away from the first lens 3 is also the surface of the second lens 4 close to the display screen 5. Designing this surface as a convex surface can converge and amplify light, which is beneficial to improving light efficiency and image clarity.

[0069] See some examples in this application. Figure 1 , Figure 5 and Figure 9 The optical module further includes a display screen 5, which is located on the side of the second lens 4 away from the first lens 3. The ratio of the center thickness T2 of the second lens 4 to the aperture L of the light-emitting area of ​​the display screen 5, T2 / L, satisfies: 0.2≤T2 / L≤0.5.

[0070] Based on the above example, the ratio of the center thickness T2 of the second lens 4 to the aperture L of the light-emitting area of ​​the display screen 5 was designed. When this ratio is within the range in the above example, the total length of the optical module can be further reduced, and the image quality of the optical module can be improved.

[0071] The display screen 5 can be rectangular or square.

[0072] When the display screen 5 is rectangular, the aperture L of the light-emitting area of ​​the display screen 5 is either the length of the long side or the short side. When the display screen 5 is square, the aperture L of the light-emitting area of ​​the display screen 5 is the side length of the square.

[0073] In some examples of this application, the total length TTL of the optical module is less than 25 mm, and the MTF value of the optical module is greater than 0.5.

[0074] As a preferred embodiment of this application, the total length (TTL) of the optical module can be 15mm to 18mm.

[0075] For example, the total length (TTL) of the optical module can be as low as 17mm, while still maintaining good image quality.

[0076] In some examples of this application, the effective focal length of the optical module is 13mm to 23mm.

[0077] Based on the above example, the optical module provided in this application embodiment achieves short-focal-length imaging based on two cemented lenses. The overall length of the entire optical module is also relatively short, while maintaining good image quality.

[0078] See some examples in this application. Figure 1 , Figure 5 and Figure 9 The beam splitter 11 is disposed on the surface of the second lens 4 near the display screen 5; the first phase delayer 10 is disposed on the surface of the second lens 4 away from the display screen 5, and the polarizing reflector 9 is stacked on the side of the first phase delayer 10 away from the second lens 4.

[0079] The optical module provided in this application embodiment uses a cemented lens group formed by bonding two lenses together. In order to facilitate the assembly of the beam splitter 11, the first phase delayer 10 and the polarizing reflector 9 to form a folded optical path in the optical module, they can be directly attached to the lens.

[0080] The beam splitter 11, for example, is a quarter-wave plate, which can be directly mounted on the non-bonded surface of the second lens 4. The first phase retarder 10 and the polarizing reflector 9 can be designed to be stacked to form a composite film and sandwiched between the second lens 4 and the first lens 3. In this way, the entire optical structure is also relatively compact.

[0081] The transmission axis of the polarizing reflector 9 forms a positive angle of 45° with the fast or slow axis of the first phase retarder 10. The first phase retarder 10 and the polarizing reflector 9 work together to resolve and transmit light.

[0082] According to the above example, the polarizing reflector 9 and the first phase delayer 10 are located on the same side of the second lens 4, which facilitates the alignment adjustment between the two.

[0083] See some examples in this application. Figure 1 , Figure 5 and Figure 9 The optical module further includes a first polarizer 8, which is disposed on the side of the polarizing reflector 9 away from the first phase delayer 10; and the first polarizer 8 is bonded to the first lens 3 through an adhesive layer 7.

[0084] According to the example above, the introduction of the first polarizer 8 can reduce stray light.

[0085] The first polarizer 8, the polarizing reflector 9, and the first phase retarder 10 can be sequentially glued and stacked to form a composite film, which is then integrally disposed between two adjacent surfaces of the first lens 3 and the second lens 4. The rear surface of the first lens 3 is glued to the first polarizer 8 via an adhesive layer 7. The front surface of the second lens 4 is connected to the first phase retarder 10. The first phase retarder 10 can be mounted on the front surface of the second lens 4, or it can be formed on the front surface of the second lens 4 by plating.

[0086] It should be noted that the surfaces of the first lens 3 and the second lens 4 near the aperture 2 are both front surfaces, and the surfaces of the first lens 3 and the second lens 4 near the display screen 5 are both rear surfaces.

[0087] In some examples of this application, the display screen 5 is configured to emit circularly polarized light or natural light. When the light emitted by the display screen 5 is natural light, a second polarizer 13 is disposed on the light-emitting surface of the display screen 5, and a second phase delayer 12 is superimposed on the side of the second polarizer 13 facing away from the display screen 5. The second polarizer 13 and the second phase delayer 12 form a superimposed element to convert natural light into circularly polarized light.

[0088] The beam splitter 11 is located between the first phase delayer 10 and the second phase delayer 12.

[0089] It should be noted that the incident light entering the lens group should be circularly polarized light.

[0090] When the display screen 5 emits natural light, the natural light needs to be converted into circularly polarized light before entering the lens group on the left. Finally, the light 6 emitted by the lens group enters the aperture 2 (i.e., the human eye) to form an image.

[0091] The device used to convert natural light into circularly polarized light is the aforementioned composite element.

[0092] Optionally, a screen protective glass can be disposed on the light-emitting surface of the display screen 5. The screen protective glass can protect the display screen 5. In this case, the light emitted by the display screen 5 is transmitted through the screen protective glass and then enters the stacking element for polarization state conversion.

[0093] Based on the above example, the second phase delayer 12 and the second polarizer 13 can be mounted on the light-emitting surface of the display screen 5 to reduce assembly difficulty.

[0094] The second polarizer 13 is, for example, a linear polarizer, whose transmission axis can be along the horizontal direction, the vertical direction, or any other direction.

[0095] The second phase delayer 12 is, for example, a quarter-wave plate, which can convert linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light.

[0096] Specifically, the fast axis or slow axis direction of the second phase delayer 12, which is closer to the side of the display screen 5, makes an angle of 45° with the transmission axis direction of the second polarizer 13.

[0097] According to the optical module provided in this application embodiment, the second phase retarder 12, located near the display screen 5, is situated between the second polarizer 13 and the beam splitter 11. The beam splitter 11 is located between the first phase retarder 10 and the second phase retarder. The first phase retarder 10 (located away from the display screen 5) is situated between the beam splitter 11 and the polarizing reflector 9.

[0098] Optionally, polarizers, phase retarders, and polarizing reflectors can be attached to planes, spheres, aspherical surfaces, cylindrical surfaces, freeform surfaces, and other types of curved surfaces.

[0099] The display screen 5 can be a self-emissive screen such as LCD, LED, OLED, Micro-OLED, ULED, or a reflective screen such as DMD.

[0100] See Figure 1 The light propagation process of the optical module is as follows:

[0101] The light 6 emitted by the display screen 5 passes through the second polarizer 13 and becomes horizontally linearly polarized light. After passing through the second phase retarder 12, it becomes left-handed or right-handed circularly polarized light. After passing through the beam splitter 11, the second lens 4, and the first phase retarder 10, it becomes horizontally linearly polarized light. Then, after being reflected by the polarizing reflector 9, it becomes horizontally linearly polarized light. After passing through the first phase retarder 10 and the second lens 4, it becomes left-handed or right-handed circularly polarized light. After being reflected by the beam splitter 11, it becomes right-handed or left-handed circularly polarized light. After passing through the second lens 4 and the first phase retarder 10 again, it becomes vertically linearly polarized light. After passing through the polarizing reflector 9, the first polarizer 8, the adhesive layer 7, and the first lens 3, it enters the aperture 2 for imaging.

[0102] The optical performance of the optical module provided in this application will be described below through Examples 1 to 3.

[0103] Example 1

[0104] See Figure 1 , Figure 1 The optical structure of the optical module provided in Embodiment 1 of this application is shown, which includes a first lens 3 and a second lens 4 bonded together, a display screen 5 disposed on one side of the second lens 4, and an aperture located on one side of the first lens 3; wherein the first lens 3 and the second lens 4 are disposed adjacent to each other along the same optical axis, and a first polarizer 8, a polarizing reflector 9, a first phase retarder 10 and a beam splitter 11 are disposed sequentially between the first lens 3 and the second lens 4; a second phase retarder 12 and a second polarizer 13 are disposed on the light-emitting surface of the display screen 5.

[0105] The height H of the second lens 4 on the side of the display screen 5 (rear surface) is 5.9 mm, the center thickness T2 of the second lens 4 is 9.6 mm, and the ratio of the two is 0.61.

[0106] The ratio of the center thickness T2 of the second lens 4 to the width (or length) of the light-emitting area of ​​the display screen 5 is 0.38.

[0107] Table 1 shows the optical parameters of the optical module, as detailed below.

[0108] Table 1

[0109]

[0110] Figure 2 , Figure 3 , Figure 4 The modulation transfer function (MTF) curves of the optical module in Example 1 at 450nm, 540nm, and 610nm are shown below. Figures 2 to 4 As can be seen, at a spatial frequency of 10 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 0.7; and at a wavelength of 610 nm, the MTF value of the optical module is higher than 0.6.

[0111] Example 2

[0112] See Figure 5 , Figure 5 The optical architecture of the optical module provided in Embodiment 2 of this application is shown, which includes a first lens 3 and a second lens 4 bonded together, a display screen 5 disposed on one side of the second lens 4, and an aperture located on one side of the first lens 3; wherein the first lens 3 and the second lens 4 are disposed adjacent to each other along the same optical axis, and a first polarizer 8, a polarizing reflector 9, a first phase retarder 10 and a beam splitter 11 are disposed sequentially between the first lens 3 and the second lens 4; a second phase retarder 12 and a second polarizer 13 are disposed on the light-emitting surface of the display screen 5.

[0113] The height H of the second lens 4 on the side of the display screen 5 (rear surface) is 7mm, the center thickness T2 of the second lens 4 is 8.5mm, and the ratio of the two is 0.82.

[0114] The ratio of the center thickness T2 of the second lens 4 to the width (or length) of the light-emitting area of ​​the display screen 5 is 0.34.

[0115] Table 2 shows the optical parameters of the optical module, as detailed below.

[0116] Table 2

[0117]

[0118] Figure 6 , Figure 7 , Figure 8 The modulation transfer function (MTF) curves of the optical module in Example 2 at 450nm, 540nm, and 610nm are shown below. Figures 6 to 8 As can be seen, at a spatial frequency of 10 lp / mm: the MTF value of the optical module is higher than 0.9 at a wavelength of 450 nm, at a wavelength of 540 nm, and at a wavelength of 610 nm.

[0119] Example 3

[0120] See Figure 9 , Figure 9The optical architecture of the optical module provided in Embodiment 32 of this application is shown, which includes a first lens 3 and a second lens 4 bonded together, a display screen 5 disposed on one side of the second lens 4, and an aperture located on one side of the first lens 3; wherein the first lens 3 and the second lens 4 are disposed adjacent to each other along the same optical axis, and a first polarizer 8, a polarizing reflector 9, a first phase retarder 10 and a beam splitter 11 are disposed sequentially between the first lens 3 and the second lens 4; a second phase retarder 12 and a second polarizer 13 are disposed on the light-emitting surface of the display screen 5.

[0121] The height H of the second lens 4 on the side of the display screen 5 (rear surface) is 4mm, the center thickness T2 of the second lens 4 is 10.6mm, and the ratio of the two is 0.38.

[0122] The ratio of the center thickness T2 of the second lens 4 to the width (or length) of the light-emitting area of ​​the display screen 5 is 0.41.

[0123] Table 3 shows the optical parameters of the optical module, as detailed below.

[0124] Table 3

[0125]

[0126] Figure 10 , Figure 11 , Figure 12 The modulation transfer function (MTF) curves of the optical module in Example 3 at 450nm, 540nm, and 610nm respectively are shown below. Figures 10 to 12 As can be seen, at a spatial frequency of 10 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 0.55; and at a wavelength of 610 nm, the MTF value of the optical module is higher than 0.5.

[0127] According to another embodiment of this application, a head-mounted display device is provided. The head-mounted display device includes a housing and an optical module as described above.

[0128] The head-mounted display device includes VR smart glasses or VR smart helmets, etc., and this application embodiment does not limit this.

[0129] The specific implementation of the head-mounted display device in this application can refer to the above-described embodiments of the optical module. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0130] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0131] While specific embodiments of this 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 are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. An optical module, characterized in that, It includes a lens group, and a beam splitter (11), a first phase delayer (10) and a polarizing reflector (9) disposed between the optical paths of the lens group, wherein the first phase delayer (10) is located between the beam splitter (11) and the polarizing reflector (9); The lens group consists of a first lens (3) and a second lens (4) glued together, with the first lens (3) and the second lens (4) arranged adjacent to each other along the same optical axis (1); The ratio H / T2 of the sagitta of the surface of the second lens (4) away from the first lens (3) to the center thickness T2 of the second lens (4) satisfies: 0.38≤H / T2≤0.82; The optical module also includes a display screen (5), which is located on the side of the second lens (4) away from the first lens (3). The ratio of the center thickness T2 of the second lens (4) to the aperture L of the light-emitting area of ​​the display screen (5) is T2 / L, which satisfies: 0.2≤T2 / L≤0.

5. The effective focal length of the optical module is 13mm to 23mm.

2. The optical module according to claim 1, characterized in that, The surface of the second lens (4) adjacent to the first lens (3) is concave or curved; The surfaces adjacent to the first lens (3) and the second lens (4) are convex or curved.

3. The optical module according to claim 2, characterized in that, The surface of the second lens (4) that is opposite to the first lens (3) is convex.

4. The optical module according to claim 1, characterized in that, The total length TTL of the optical module is less than 25mm, and the MTF value of the optical module is greater than 0.

5.

5. The optical module according to claim 1, characterized in that, The beam splitter (11) is disposed on the surface of the second lens (4) near the display screen (5); The first phase delay unit (10) is disposed on the surface of the second lens (4) away from the display screen (5), and the polarizing reflector (9) is stacked on the side of the first phase delay unit (10) away from the second lens (4).

6. The optical module according to claim 5, characterized in that, The optical module also includes a first polarizer (8), which is located on the side of the polarizing reflector (9) away from the first phase delayer (10). Furthermore, the first polarizer (8) is bonded to the first lens (3) through an adhesive layer (7).

7. The optical module according to claim 1, characterized in that, The display screen (5) is configured to emit circularly polarized light or natural light; When the light emitted by the display screen (5) is natural light, a second polarizer (13) is provided on the light-emitting surface of the display screen (5), and a second phase delayer (12) is superimposed on the side of the second polarizer (13) away from the display screen (5). The second polarizer (13) and the second phase delayer (12) form a superimposed element to convert natural light into circularly polarized light.

8. The optical module according to claim 7, characterized in that, The beam splitter (11) is located between the first phase delayer (10) and the second phase delayer (12).

9. A head-mounted display device, characterized in that, include: case; as well as The optical module as described in claims 1-8.

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