Optical module and smart head-mounted device

Abstract

The embodiment of the application provides an optical module and a smart head-mounted device; the optical module comprises a display screen, a first lens and a second lens arranged along the same optical axis; wherein the first lens is located between the display screen and the second lens, the first lens is a flat-concave lens, and the flat surface of the first lens is glued to the display screen; a light splitting element is arranged on the surface of the first lens away from the display screen, a phase retarder and a polarization reflection element are stacked on the surface of the second lens close to the display screen, and the phase retarder is located between the light splitting element and the polarization reflection element.

Description

Optical modules and smart head-mounted devices Technical Field

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

[0002] With the rapid development of virtual reality technology, head-mounted displays (HMDs), as important virtual reality devices, have received widespread attention for their performance and user experience. However, existing HMD optical modules generally suffer from problems such as heavy weight, excessive total optical length (TTL, i.e., the distance from the display screen to the exit pupil), and susceptibility to ghosting. These issues not only increase the user's wearing burden but may also affect image quality and visual experience.

[0003] Specifically, existing HMD optical modules typically employ a monolithic folded optical path design. While maintaining a certain field of view (FOV), the time-to-light (TTL) is often greater than 18mm, or even greater than 20mm, and the total weight of all lenses generally exceeds 20g. Furthermore, during the assembly of the optical module, the display screen is prone to defects due to particles falling into it. Summary of the Invention

[0004] The purpose of this application is to provide a new technical solution for an optical module and a smart head-mounted device.

[0005] In a first aspect, this application provides an optical module. The optical module includes a display screen, a first lens, and a second lens arranged along the same optical axis; wherein the first lens is located between the display screen and the second lens, the first lens is a plano-concave lens, and the plane of the first lens is cemented to the display screen;

[0006] A beam splitting element is disposed on the surface of the first lens away from the display screen, and a phase delayer and a polarization reflection element are stacked on the surface of the second lens close to the display screen, with the phase delayer located between the beam splitting element and the polarization reflection element.

[0007] Optionally, an air gap is provided between the first lens and the second lens.

[0008] Optionally, the optical module satisfies:

[0009] 20mm < 1 / 3 EFL L1 <EFL All <28mm;

[0010] 20mm < 1 / 3 EFL L2 <EFL All <28mm;

[0011] 0.5*TTL < T < 0.6*TTL;

[0012] Among them, EFL L1 EFL is the focal length of the first lens. L2 EFL is the focal length of the second lens. All The total focal length of the optical module is T, and T is the straight-line distance between the second surface of the first lens and the third surface of the second lens.

[0013] Optionally, the optical module satisfies:

[0014] -50mm<R 21 <R 12 <-40mm;

[0015] -5<R 22 / R 21 <-4;

[0016] 2mm < CT L1 <CT L2 <4mm;

[0017] Among them, R 12 R is the radius of curvature of the second surface of the first lens. 21 R is the radius of curvature of the third surface of the second lens. 22 Let CT be the radius of curvature of the fourth surface of the second lens. L1 The center thickness of the first lens, CT L2 The center thickness of the second lens is given.

[0018] Optionally, the optical module satisfies:

[0019] 2mm < CT L1 <CT L2 <4mm;

[0020] 3<ET L1 / CT L1 <4;

[0021] 0.3 < ET L2 / CT L2 <0.5;

[0022] Among them, CT L1 ET is the center thickness of the first lens. L1 The edge thickness of the first lens, CT L2 ET is the center thickness of the second lens. L2 The edge thickness of the second lens.

[0023] Optionally, the optical module satisfies:

[0024] 5 < CA L1 / (ET L1 +CT L1 <6;

[0025] 3 < CA L2 / (ET L2 +CT L2 ) < 4;

[0026] Among them, CT L1 ET is the center thickness of the first lens. L1 CA is the edge thickness of the first lens. L1 The effective aperture of the first lens is CT. L2 ET is the center thickness of the second lens. L2 CA is the edge thickness of the second lens. L2 The effective aperture of the second lens is denoted as .

[0027] Optionally, the optical module further includes a polarization element disposed on the side surface of the polarization reflection element opposite to the phase delayer.

[0028] Optionally, the beam splitter is a semi-transparent and semi-reflective film, the phase delayer is a quarter-wave plate, the polarization reflection element is a polarization reflection film, and the polarization element is a polarizing film.

[0029] Optionally, the total optical length of the optical module is ≤17.5mm when the FOV is not less than 90°.

[0030] Secondly, this application also provides a smart head-mounted device, the smart head-mounted device comprising:

[0031] The outer casing; and

[0032] The optical module as described in the first aspect.

[0033] The beneficial effects of this application are as follows:

[0034] This application provides an optical module that can be applied to head-mounted displays (HMDs). The optical module of this application can significantly reduce the total optical length and the total weight of the lenses by optimizing the lens design on the near-screen side and adding optical devices such as beam splitters, phase delayers and polarization reflection elements at appropriate positions in the optical path, while ensuring that the imaging quality is not degraded. At the same time, it can effectively suppress the generation of "ghosting" and thus ensure good imaging quality.

[0035] 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

[0036] 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.

[0037] Figure 1 shows the structure and optical path diagram of the optical module provided in the embodiment of this application;

[0038] Figure 2 is a dot array diagram of the optical module provided in the embodiment of this application;

[0039] Figure 3 shows the field curvature and distortion diagram of the optical module provided in the embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. First lens; 11. First surface; 12. Second surface; 2. Second lens; 21. Third surface; 22. Fourth surface; 3. Display screen; 4. Beam splitter; 5. Phase delayer; 6. Polarization reflection element; 7. Polarization element; 01. Human eye. Detailed Implementation

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The optical module and smart head-mounted device provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0048] According to one embodiment of this application, an optical module is provided. Referring to FIG1, the optical module includes a display screen 3, a first lens 1, and a second lens 2 arranged along the same optical axis. The first lens 1 is located between the display screen 3 and the second lens 2. The first lens 1 is a plano-concave lens, and the plane of the first lens 1 is cemented to the display screen 3. A beam splitting element 4 is disposed on the surface of the first lens 1 away from the display screen 3. A phase delay 5 and a polarization reflection element 6 are stacked on the surface of the second lens 2 close to the display screen 3, and the phase delay 5 is located between the beam splitting element 4 and the polarization reflection element 6.

[0049] The optical module provided in this application involves multiple optical elements, each performing a specific function and working together to achieve good imaging results and user experience. The following is an analysis of each optical element in the optical module of this application and a description of its technical effects.

[0050] The optical module provided in this application includes a display screen 3, which serves as the light source for the entire optical module and is capable of emitting light for imaging display.

[0051] The optical module provided in this application embodiment includes a first lens 1, which is located on the side close to the display screen 3, and the first lens 1 is designed as a plano-concave lens.

[0052] In this embodiment of the application, the display screen 3 is glued together with the first lens 1, so that the first lens 1 can be used to protect the display screen 3.

[0053] Specifically, referring to Figure 1, the first surface 11 of the first lens 1 is a plane, which is bonded to the light-emitting surface of the display screen 3, achieving a gapless connection. This tight-fitting design eliminates the gap problems that may exist in traditional designs, thereby effectively avoiding the risk of dust, impurities, and other tiny particles falling onto the display screen 3. In smart head-mounted devices, any minute contamination can seriously affect image quality; therefore, this design enhances the reliability and durability of smart head-mounted devices.

[0054] It should be noted that in the optical module provided in the application embodiment, the display screen 3, as a core component, has a relatively fragile light-emitting surface. Direct wiping or touching it after it becomes dirty could potentially cause irreversible damage, thus affecting the display effect of the entire optical module. Given the high manufacturing precision and cost of the display screen 3, any form of physical damage will result in expensive repair or replacement costs, which undoubtedly increases the product's maintenance costs and usage risks.

[0055] Therefore, the protection of the display screen 3 was considered as one of the factors in the initial design of the optical solution of this application. By designing the first surface 11 of the first lens 1 as a plane and directly bonding it to the light-emitting surface of the display screen 3, the direct contact of the external environment with the display screen 3 is effectively isolated, thereby greatly reducing the risk of damage to it.

[0056] The first lens 1 provided in this application is a plano-concave lens. The design of the plano-concave lens can also effectively control the divergence of light, making the light more concentrated before entering the second lens 2, reducing the generation of stray light, which helps to reduce the "ghosting" phenomenon.

[0057] The optical module provided in this embodiment includes a second lens 2, as shown in Figure 1. The second lens 2 is located on the side of the first lens 1 that is away from the display screen 3. The second lens 2 can further focus the light passing through the first lens 1, thereby forming a clear image.

[0058] In addition to the aforementioned display screen 3, first lens 1, and second lens 2, the optical module provided in this application embodiment also includes optical elements such as beam splitting element 4, phase delayer 5, and polarization reflection element 6. The beam splitting element 4, the phase delayer 5, and the polarization reflection element 6 are designed to be located between the first lens 1 and the second lens 2 to achieve optical path folding.

[0059] The beam-splitting element 4 is located on the second surface 12, which is close to the first lens 1. It is used to split the light from the first lens 1 into two parts: one part is transmitted directly, and the other part is reflected. Through beam splitting, the distribution and path change of the light are realized, which provides the conditions for subsequent phase delay and polarization reflection.

[0060] The phase retarder 5 and the polarization reflection element 6 are disposed together on the third surface 21 of the second lens 2, which is close to the display screen 3. Specifically, the phase retarder 5 is located after the beam splitter 4 and changes the polarization state of the light through phase delay. The polarization reflection element 6 is located after the phase retarder 5 and is used to polarize and reflect the light that has been adjusted by the phase retarder 5. Through polarization reflection, the light is reflected and focused again, improving the utilization rate of light and the image quality. At the same time, the selective reflection characteristics of the polarization reflection element 6 help reduce unnecessary reflections and interference, further reducing the generation of "ghosting".

[0061] In one example, the beam splitter 4 is a semi-transparent and semi-reflective film, which can transmit a portion of light while reflecting a portion of light. The phase retarder 5 is a quarter-wave plate, which is used to adjust the phase of the light. The polarization reflective element 6 is a polarization reflective film, which is located after the phase retarder 5 and can reflect or transmit light according to the polarization state of the light.

[0062] In the optical module provided in this application embodiment, the beam splitter 4, the phase delayer 5, and the polarization reflection element 6 are combined to form a highly efficient folded optical path. This design not only shortens the optical length (TTL) of the optical module but also enables multiple reflections and modulations of light, which helps improve image quality.

[0063] It should be noted that the optical module provided in this application adopts an interlayer optical path folding design, which reduces stray reflections of light between lenses and also helps to reduce the generation of "ghosting".

[0064] This application provides an optical module that can be applied to head-mounted displays (HMDs). The optical module of this application can significantly reduce the total optical length and the total weight of the lenses by optimizing the lens design on the near-screen side and adding optical devices such as beam splitters 4, phase delayers 5 and polarization reflection elements 6 at appropriate positions in the optical path, while ensuring that the imaging quality is not degraded. At the same time, it can effectively suppress the generation of "ghosting" and thus ensure good imaging quality.

[0065] It should also be emphasized that, because the display screen 3 and the first lens 1 are bonded together, the risk of defects caused by particles falling into the display screen during assembly is reduced. This optimization not only improves the overall reliability of the optical assembly, but also significantly enhances the stability and durability of the final product, providing users with a more reliable and stable user experience.

[0066] The optical module provided in this application embodiment can provide a good user experience for applications such as virtual reality.

[0067] In some examples of this application, an air gap is provided between the first lens 1 and the second lens 2.

[0068] In this example of the application, an air gap is provided between the first lens 1 and the second lens 2, and the beam splitter 4, the phase retarder 5, and the polarization reflection element 6 are located within the air gap. This allows light to fold within the air gap without passing through the lens, and this design can bring the following technical effects:

[0069] This reduces internal reflection and interference within the lens: When light passes through a lens, it is reflected and interfered with inside the lens, which can lead to phenomena such as "ghosting." By placing the beam splitter 4, the phase retarder 5, and the polarization reflector 6 in an air gap, the light is reflected back at the interface between the air and the lens, rather than inside the lens. This helps reduce internal reflection and interference, thereby reducing the occurrence of phenomena such as "ghosting."

[0070] In addition, air gaps can also serve as a medium for light propagation. Their refractive index differs from that of lens materials, which helps to further adjust the propagation path and focusing effect of light, thereby optimizing image quality.

[0071] In some examples of this application, referring to FIG1, the first lens 1 includes a first surface 11 and a second surface 12; the first surface 11 is planar and is bonded to the display screen 3; the second surface 12 is concave, and the beam splitting element 4 is disposed on the second surface 12.

[0072] The first lens 1 provided in this application includes two surfaces, namely a first surface 11 and a second surface 12. The first surface 11 is designed as a plane, enabling a tight adhesive bond with the display screen 3. The adhesive bonding of the first surface 11 of the first lens 1 to the display screen 3 reduces light loss in the air gap between the first lens 1 and the display screen 3, improving light utilization. Simultaneously, this adhesive bond also enhances the stability between the first lens 1 and the display screen 3, helping to maintain the overall performance of the optical module.

[0073] The concave design of the second surface 12 facilitates the convergence and divergence of light, further enhancing the imaging capability of the optical system. Furthermore, the second surface 12 provides a suitable substrate for the placement of the beam-splitting element 4.

[0074] In the optical module provided in this application embodiment, the beam splitter 4 is disposed on the second surface 12 of the first lens 1. The beam splitter 4 is, for example, a semi-transparent, semi-reflective film.

[0075] Specifically, a semi-transparent and semi-reflective film can be deposited on the second surface 12 of the first lens 1, so that light can be split in a specific proportion when passing through the second surface 12. This helps to achieve a reasonable distribution of light in the optical module, thereby optimizing the overall optical path structure.

[0076] Furthermore, by directly placing the beam splitter 4 on the surface of the first lens 1, additional optical components and assembly steps are reduced, thereby lowering manufacturing and assembly costs.

[0077] In this application, by tightly bonding the first lens 1 to the display screen 3 and by placing the beam splitter 4 on the surface of the first lens 1, the entire optical module becomes more compact and integrated. This compact layout helps reduce the size of the optical module and improves its application flexibility in devices such as virtual reality (VR) or augmented reality (AR).

[0078] In some examples of this application, referring to FIG1, the second lens 2 includes a third surface 21 and a fourth surface 22, the third surface 21 being adjacent to and spaced apart from the second surface 12; the phase retarder 5 and the polarization reflection element 6 are stacked and disposed on the third surface 21.

[0079] The second lens 2 provided in this application includes two surfaces: a third surface 21 and a fourth surface 22, wherein the third surface 21 is adjacent to and spaced apart from the second surface 12 of the first lens 1. This air gap provides the necessary space for light transmission between the lenses and allows optical elements to be disposed on the third surface 21.

[0080] In the optical module provided in this embodiment, the phase retarder 5 and the polarization reflection element 6 are directly stacked and disposed on the third surface 21 of the second lens 2. The main function of the phase retarder 5 is to adjust the phase of the light, thereby achieving precise control over the polarization state of the light. The polarization reflection element 6 can reflect or transmit light according to its polarization direction, further manipulating the light transmission path. The stacking of the phase retarder 5 and the polarization reflection element 6 on the third surface 21 allows them to work together on the passing light, achieving fine control over the polarization state and transmission path of the light. This synergistic effect helps optimize the performance of the optical module and improve image quality. This optical control helps reduce stray light and ghosting phenomena, improving image clarity.

[0081] Furthermore, stacking the phase retarder 5 and the polarization reflection element 6 on the third surface 21 of the second lens 2 allows for a compact layout of the optical elements. This layout helps reduce the size of the optical module and improves its integration and application flexibility.

[0082] Optionally, an anti-reflective coating may be deposited on the fourth surface 22 of the second lens 2.

[0083] The main function of anti-reflective coatings is to increase the amount of light passing through a lens by reducing light reflection on the lens surface. In devices such as virtual reality (VR), increased light transmittance helps improve image brightness and clarity.

[0084] It should be noted that reducing reflected light can reduce the direct stimulation of light on the eyes, especially in bright light environments, thereby reducing eye fatigue and improving the comfort of wearing VR devices for extended periods.

[0085] In addition, anti-reflective coatings can maintain the color balance of light, reduce color distortion caused by reflection, and make the transmitted light closer to the color of the original light source, thereby improving the color reproduction of the image.

[0086] In some examples of this application, the optical module satisfies the following relationship:

[0087] 20mm < 1 / 3 EFL L1 <EFL All <28mm;

[0088] 20mm < 1 / 3 EFL L2 <EFL All <28mm;

[0089] 0.5*TTL < T < 0.6*TTL;

[0090] Among them, EFL L1 EFL is the focal length of the first lens 1. L2 EFL is the focal length of the second lens 2. All The total focal length of the optical module is T, and the straight-line distance between the second surface 12 of the first lens 1 and the third surface 21 of the second lens 2 is T.

[0091] According to this example of the application, the focal length design of the first lens 1 is described as follows: 20mm < 1 / 3 EFL L1 <EFL All <28mm. This inequality indicates that the focal length (EFL) of the first lens 1 is... L1 One-third of the focal length of the entire optical module is greater than 20mm, while the total focal length (EFL) of the entire optical module is greater than 20mm. All The focal length of the first lens 1 is between one-third and 28mm. This ensures that the first lens 1 has a sufficient focal length to provide the required imaging characteristics.

[0092] In this example of the application, the focal length design of the second lens 2 is also described, specifically: 20mm < 1 / 3 EFL L2 <EFL All <28mm. For the second lens 2, its focal length (EFL) L2 One-third of the focal length of the first lens is also greater than 20mm, and the total focal length of the entire optical module is also between one-third of the focal length of the second lens 2 and 28mm. This indicates that the focal lengths of both lenses have been carefully designed to ensure a balance in the overall performance of the entire optical module.

[0093] This example of the application also describes an air gap design between the first lens 1 and the second lens 2, namely 0.5*TTL < T < 0.6*TTL. This formula specifies the straight-line distance T (i.e., air gap) between the second surface 12 of the first lens 1 and the third surface 21 of the second lens 2, which is between half and sixty percent of the total optical length (TTL) of the entire optical module. Such a design helps to control the refraction and scattering of light as it passes through the lens, thereby improving light utilization and image quality.

[0094] According to this example of the application, by precisely controlling the focal length of each lens and the air gap (i.e., T) between two lenses, the total optical length (TTL) of the entire optical module can be controlled to be below 17.5 mm. This reduces the overall size of the optical module.

[0095] At the same time, the entire optical module can transmit and focus light more efficiently, reducing light refraction and scattering losses. Fine-tuning of the focal length and air gap also helps reduce aberrations and distortion, improving image sharpness. This allows the optical module to provide more realistic and natural imaging results.

[0096] In some examples of this application, the optical module satisfies the following relationship:

[0097] -50mm<R 21 <R 12 <-40mm;

[0098] -5<R 22 / R 21 <-4;

[0099] 2mm < CT L1 <CT L2 <4mm;

[0100] Among them, R 12 R is the radius of curvature of the second surface 12 of the first lens 1. 21 R is the radius of curvature of the third surface 21 of the second lens 2. 22 The radius of curvature of the fourth surface 22 of the second lens 2 is CT. L1 The center thickness of the first lens 1, CT L2 The center thickness of the second lens 2 is given.

[0101] As described in this example of the application, -50mm < R 21 <R 12 <-40mm, this formula indicates the radius of curvature R of the third surface 21 of the second lens 2. 21The absolute value is less than the radius of curvature R of the second surface 12 of the first lens 1. 12 The absolute values ​​of both are between -50mm and -40mm. This design helps control the angle of refraction of light as it passes through the lens, allowing the light to be focused more closely onto the image plane.

[0102] This example in the application also describes that -5 < R 22 / R 21 <-4, this formula specifies the radius of curvature R of the fourth surface 22 of the second lens 2. 22 With respect to the radius of curvature R of the third surface 21 21 The ratio between them. This ratio range ensures that there is an appropriate difference in curvature between the two surfaces of the second lens 2, thereby helping to further control the refraction and focusing characteristics of light.

[0103] This example in the application also describes that 2mm < CT L1 <CT L2 <4mm indicates that the center thickness of the two lenses is controlled within 2mm to 4mm. The center thickness of the lens is also an important design parameter. A thinner center thickness helps to reduce the propagation path length of light inside the lens, thereby reducing EFL. However, the lens thickness also needs to be balanced between ensuring sufficient mechanical strength and optical performance.

[0104] In this application, by carefully designing the radius of curvature and center thickness of the lens surface, the entire optical module can achieve a smaller EFL (Earning Fluid Filter). A smaller EFL means that light can be focused more closely on the image plane, thereby improving image sharpness and resolution.

[0105] Furthermore, in this application, the precise control of the lens surface curvature radius and center thickness helps reduce aberrations and distortion, improving image quality. This enables the optical module to provide more accurate and natural imaging results.

[0106] In some examples of this application, the optical module satisfies the following relationship:

[0107] 2mm < CT L1 <CT L2 <4mm;

[0108] 3<ET L1 / CT L1 <4;

[0109] 0.3 < ET L2 / CT L2 <0.5;

[0110] Among them, CT L1ET is the center thickness of the first lens 1. L1 The edge thickness of the first lens 1, CT L2 ET is the center thickness of the second lens 2. L2 The edge thickness of the second lens 2.

[0111] CT L1 With CT L2 Relationship: CT L1 Represents the center thickness of the first lens 1, CT L2 This represents the center thickness of the second lens 2. The above relationship is 2mm < CT. L1 <CT L2 The thickness of <4mm indicates that the center thickness of both lenses is controlled between 2mm and 4mm, with the center thickness of the second lens 2 being slightly greater than that of the first lens 1. This design ensures both the structural strength of each lens and achieves lightweight design.

[0112] ET L1 With ET L2 Relationship: ET L1 This represents the edge thickness of the first lens 1. Relationship 3 < ET L1 / CT L1 The value <4 indicates that the ratio of the edge thickness to the center thickness of the first lens 1 is between 3 and 4. This means that the edge thickness is relatively large compared to the center thickness, which helps to enhance the lens's resistance to deformation while maintaining overall weight control.

[0113] ET L2 With CT L2 Relationship: ET L2 This represents the edge thickness of the second lens 2. The relationship is 0.3 < ET. L2 / CT L2 A value <0.5 indicates that the ratio of the edge thickness to the center thickness of the second lens 2 is between 0.3 and 0.5. Compared to the first lens 1, the second lens 2 has a lower edge thickness ratio, which helps to further reduce weight while maintaining sufficient structural strength.

[0114] In some examples of this application, the optical module also satisfies the following relationship:

[0115] 5 < CA L1 / (ET L1 +CT L1 <6;

[0116] 3 < CA L2 / (ET L2 +CT L2 ) < 4;

[0117] Among them, CT L1ET is the center thickness of the first lens 1. L1 CA is the edge thickness of the first lens 1. L1 The effective aperture of the first lens 1, CT L2 ET is the center thickness of the second lens 2. L2 CA is the edge thickness of the second lens 2. L2 This is the effective aperture of the second lens 2.

[0118] CT L1 This represents the effective aperture of the first lens 1. Relationship 5 < CA L1 / (ET L1 +CT L1 A ratio of 5 to 6 indicates that the effective aperture of the first lens 1 is between 5 and 6, which is the ratio of its total thickness (edge ​​thickness + center thickness). A larger ratio helps improve the optical performance of the lens, such as a larger field of view and better image quality, while maintaining a lightweight design.

[0119] CT L2 This represents the effective aperture of the second lens. Relationship 3 < CA L2 / (ET L2 +CT L2 The value < 4 indicates that the ratio between the effective aperture of the second lens 2 and its total thickness is between 3 and 4. By controlling the ratio, the optical performance and structural strength can be optimized while maintaining the lens's lightweight design.

[0120] The two examples above demonstrate how precise control of the ratio between the center thickness, edge thickness, and effective aperture of the lens achieves lightweighting, structural reinforcement, and improved imaging quality of the optical module.

[0121] Furthermore, when the optical module simultaneously satisfies the following relationship, the aim is to further optimize the weight of the optical module and better achieve lightweighting of the optical module. The specific relationship is as follows:

[0122] 2mm < CT L1 <CT L2 <4mm;

[0123] 3<ET L1 / CT L1 <4;

[0124] 0.3 < ET L2 / CT L2 <0.5;

[0125] 5 < CA L1 / (ET L1 +CT L1 <6;

[0126] 3 < CA L2 / (ET L2 +CT L2 ) < 4;

[0127] Among them, CT L1 ET is the center thickness of the first lens 1. L1 CA is the edge thickness of the first lens 1. L1 The effective aperture of the first lens 1, CT L2 ET is the center thickness of the second lens 2. L2 CA is the edge thickness of the second lens 2. L2 This is the effective aperture of the second lens 2.

[0128] In this example of the application, the center thickness of the two lenses is described as 2 mm < CT. L1 <CT L2 <4mm. This condition limits the center thickness range of each lens, ensuring that the lens is neither too thick, which would increase weight, nor too thin, which would affect manufacturing and optical performance.

[0129] Specifically, by controlling the thickness of the first lens 1 to between 2mm and 4mm, and designing the center thickness of the second lens 2 to be slightly greater than the center thickness of the first lens 1, lightweighting can be achieved while maintaining structural strength.

[0130] In this example of the application, 3 < ET is described. L1 / CT L1 <4; where ET L1 It is the edge thickness of the first lens 1, CT L1 This refers to the center thickness of the first lens 1. This ratio ensures that the edge thickness of the first lens 1 is reasonable relative to the center thickness, helping to balance the requirements of lens rigidity and lightweight design. A larger edge thickness ratio design can improve the lens's resistance to deformation while maintaining overall weight control.

[0131] In this example of the application, 0.3 < ET is described. L2 / CT L2 <0.5; where ET L2 It is the edge thickness of the second lens 2, CT L2 This refers to the center thickness of the second lens 2. Similar to the first lens 1, this condition limits the ratio of the edge thickness to the center thickness of the second lens 2 to achieve a more reasonable weight distribution and mechanical properties. A lower ratio helps to further reduce the weight of the second lens while maintaining sufficient structural strength.

[0132] In this example of the application, 5<CA is described.L1 / (ET L1 +CT L1 ) < 6; where, CA L1 This is the effective aperture of the first lens 1. This condition ensures a reasonable ratio between the effective aperture of the first lens 1 and its total thickness (edge ​​thickness + center thickness). A larger ratio helps improve the optical performance of the lens, such as a larger field of view and better image quality, while maintaining a lightweight design.

[0133] In this example of the application, 3<CA is described. L2 / (ET L2 +CT L2 ) < 4; where, CA L2 This is the effective aperture of the second lens. Similar to the first lens 1, this condition limits the ratio between the effective aperture of the second lens 2 and its total thickness. By controlling this ratio, the optical performance and structural strength can be optimized while maintaining the lens's lightweight design.

[0134] According to this example, by controlling the ratio of the center thickness, edge thickness, and effective aperture of each lens, the entire optical module can be made lightweight. This is crucial for improving the wearing comfort of HMD devices.

[0135] Furthermore, a well-designed lens thickness and proportion help reduce aberrations and ghosting, improving image quality and field of view. In addition, appropriate edge thickness and proportion design can enhance the lens's resistance to deformation, improving the stability and durability of the optical module.

[0136] In some examples of this application, referring to FIG1, the optical module further includes a polarization element 7 disposed on the side surface of the polarization reflection element 6 facing away from the phase delayer 5.

[0137] The optical module provided in this application embodiment may further include a polarization element 7. The polarization element 7, the polarization reflection element 6, and the phase delayer 5 may be stacked in sequence to form a composite film. The composite film may be directly attached to the third surface 21 of the second lens 2.

[0138] The composite film formed by the phase delayer 5, the polarization reflection element 6, and the polarization element 7 can precisely control the polarization direction and reflection path of light, reducing light loss and interference. This design helps to eliminate or reduce image distortion and "ghosting" caused by polarization mismatch, thereby improving image clarity.

[0139] Optionally, an anti-reflective film may also be added to the composite film, and the anti-reflective film is disposed on the side of the phase delayer 5 away from the polarization reflection element 6.

[0140] The entire composite film has multiple functions, including polarization correction, phase delay, and anti-reflection, which can further reduce light reflection and interference and improve image quality.

[0141] In some examples of this application, the beam splitter 4 is a semi-transparent and semi-reflective film, the phase delayer 5 is a quarter-wave plate, the polarization reflective element 6 is a polarization reflective film, and the polarization element 7 is a polarizing film.

[0142] In some examples of this application, the total optical length of the optical module is ≤17.5mm when the FOV is not less than 90°.

[0143] The optical module provided in this application embodiment, as shown in Figure 1, adds a plano-concave lens (i.e., the first lens 1) on the side close to the display screen 3, and uses multiple optical films and air layers to achieve optical path folding.

[0144] Referring to Figure 1, light emitted from the display screen 3 enters the interior of the first lens 1 through the first surface 11, passes through the second surface 12, and about 50% of the light exits into the air gap (located between the first lens 1 and the second lens 2). After passing through the optical film (including the phase retarder 5 and polarization reflection element 6, etc.) attached to the third surface 21 of the second lens 2, it is reflected back to the air layer to the second surface 12. After another reflection, 50% of the light is reflected back to the air gap. Due to the change in polarization direction, the light can enter the interior of the second lens 2 again after passing through the third surface 21, and then enters the human eye 01 through the fourth surface 22 of the second lens 2. This achieves optical path folding between air layers, avoiding the influence of internal stress birefringence.

[0145] The optical module of this application, by precisely designing the optical parameters such as curvature, thickness and material of the first lens 1 and the second lens 2, reduces the total optical length (TTL) of the entire optical module to 15.4 mm when the FOV is not less than 90°, and the total weight of the two lenses is reduced to less than 9g.

[0146] The optical module provided in this application embodiment has high imaging quality. The spot size is controlled within approximately 66 micrometers across the entire field of view, ensuring image clarity and providing users with a more realistic visual experience.

[0147] The present application will be described in detail below through Example 1.

[0148] Example 1

[0149] Referring to Figure 1, the optical module includes a display screen 3, a first lens 1, and a second lens 2 arranged sequentially along the same optical axis;

[0150] The first lens 1 is a plano-concave lens, which includes a first surface 11 and a second surface 12. The first surface 11 is planar and is bonded to the display screen 3. The second surface 12 is concave and a beam splitting element 4 (such as a semi-transparent and semi-reflective film) is deposited on the second surface 12.

[0151] The second lens 2 includes a third surface 21 and a fourth surface 22. The third surface 21 is close to the second surface 12. A composite film is attached to the third surface 21. The composite film includes a phase retarder 5, a polarizing reflective element 6, and a polarizing element 7 stacked sequentially. The phase retarder 5 is a quarter-wave plate, the polarizing reflective element 6 is a polarizing reflective film, and the polarizing element 7 is a polarizing film. The phase retarder 5 is located between the beam splitter 4 and the polarizing reflective element 6.

[0152] The display screen 3 is, for example, 2.1 inches.

[0153] The optical parameters of the optical module are detailed in Table 1 below.

[0154] Table 1

[0155]

[0156]

[0157] The optical module provided in this specific example has the optical performance shown in Figures 2 and 3: Figure 2 is a schematic diagram of the dot plot, and Figure 3 is a field curvature distortion diagram.

[0158] A dot plot refers to the diffuse pattern formed by the intersection of numerous light rays emanating from a single point with the image plane due to aberrations. This pattern, distributed over a certain range, is used to evaluate the imaging quality of the projection optical system. Referring to Figure 2, the optical module provided in this specific example has a maximum image point size of less than 65 μm in the dot plot. This indicates that the optical module maintains good image sharpness at different viewing angles (which is sufficient for user needs in smart head-mounted devices).

[0159] Referring to Figure 3, the optical module provided in this specific example has a field curvature of less than 1.3 mm and an absolute distortion of less than 22.6% in the full field of view (e.g., 90°, half field of view θ is 45°). This indicates that the distortion generated during the imaging process of this optical module is very small and can fully meet the user's imaging requirements for smart head-mounted devices.

[0160] In summary, the optical module provided in this application embodiment can meet the requirements of HMD applications for lightweight, low ghosting and high imaging quality.

[0161] According to another embodiment of this application, a smart head-mounted device is provided, the smart head-mounted device including a housing and an optical module as described above.

[0162] The smart head-mounted devices provided in this application are, for example, VR smart head-mounted devices, such as VR smart glasses or VR smart helmets.

[0163] The specific implementation of the smart head-mounted 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.

[0164] 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.

[0165] 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, The optical module includes a display screen (3) and a lens group arranged along the same optical axis. The lens group consists of a first lens (1) and a second lens (2). The first lens (1) is located between the display screen (3) and the second lens (2). The first lens (1) is a plano-concave lens, and the plane of the first lens (1) is cemented to the display screen (3). The second lens (2) is a biconvex lens. A beam splitter (4) is disposed on the surface of the first lens (1) away from the display screen (3). A phase retarder (5) and a polarization reflection element (6) are stacked on the surface of the second lens (2) close to the display screen (3). The phase retarder (5) is located between the beam splitter (4) and the polarization reflection element (6). The optical module satisfies the following condition: 2mm < CT. L1 <CT L2 <4mm; 3<ET L1 / CT L1 <4; 0.3 <ET L2 / CT L2 <0.5; where CT L1 ET is the center thickness of the first lens (1). L1 The edge thickness of the first lens (1), CT L2 ET is the center thickness of the second lens (2). L2 The edge thickness of the second lens (2) is given.

2. The optical module according to claim 1, characterized in that, An air gap is provided between the first lens (1) and the second lens (2).

3. The optical module according to claim 2, characterized in that, The optical module satisfies: 20mm < 1 / 3 |EFL L1 |<EFL All <28mm; 20mm <1 / 3EFL L2 <EFL All <28mm; 0.5*TTL < T < 0.6*TTL; where EFL L1 EFL is the focal length of the first lens (1). L2 EFL is the focal length of the second lens (2). All T is the total focal length of the optical module, T is the straight-line distance between the second surface (12) of the first lens (1) and the third surface (21) of the second lens (2), the second surface (12) being the surface of the first lens (1) away from the display screen (3), and the third surface (21) being the surface of the second lens (2) close to the display screen (3); TTL is the distance from the side of the second lens (2) away from the display screen (3) to the display screen (3).

4. The optical module according to claim 3, characterized in that, The optical module satisfies: -50mm < R 21 <R 12 <-40mm; -5<R 22 / R 21 <-4; 2mm < CT L1 <CT L2 <4mm; where R 12 R is the radius of curvature of the second surface (12) of the first lens (1). 21 R is the radius of curvature of the third surface (21) of the second lens (2). 22 The radius of curvature of the fourth surface (22) of the second lens (2), the fourth surface (22) being the surface of the second lens (2) facing away from the display screen (3), CT L1 The center thickness of the first lens (1), CT L2 The center thickness of the second lens (2) is given.

5. The optical module according to claim 1, characterized in that, The optical module also satisfies: 5 < CA L1 / (ET) L1 +CT L1 ) < 6; 3 < CA L2 / (ET) L2 +CT L2 ) < 4; where CT L1 ET is the center thickness of the first lens (1). L1 CA is the edge thickness of the first lens (1). L1 For the effective aperture of the first lens (1), CT L2 ET is the center thickness of the second lens (2). L2 CA is the edge thickness of the second lens (2). L2 The effective aperture of the second lens (2) is given.

6. The optical module according to claim 1, characterized in that, The optical module also includes a polarization element (7), which is disposed on the side surface of the polarization reflection element (6) away from the phase delayer (5).

7. The optical module according to claim 6, characterized in that, The beam splitter (4) is a semi-transparent and semi-reflective film, the phase delayer (5) is a quarter-wave plate, the polarization reflection element (6) is a polarization reflection film, and the polarization element (7) is a polarizing film.

8. The optical module according to any one of claims 1-7, characterized in that, The total optical length of the optical module is ≤17.5mm when the field of view (FOV) is not less than 90°.

9. A smart head-mounted device, characterized in that, include: shell; And the optical module as described in any one of claims 1-8.

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