Optical system and display device

Abstract

The embodiment of the utility model provides an optical system and display equipment. Wherein the optical system comprises a multi-focus lens, a lens group, a polarization reflection element, a phase retarder and a light splitting element which are arranged along the same optical axis; wherein the phase delayer is located between the light splitting element and the polarization reflection element; the lens group comprises at least one lens, and at least one lens in the lens group is located between light paths formed by the light splitting element, the phase retarder and the polarization reflection element; and the multi-focus lens is used for enabling the optical system to realize focal power change in a full view field so as to reasonably distribute focal power of different view fields.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical technology, and more specifically, relate to an optical system and a display device. Background Art

[0002] In optical display devices, especially in virtual reality (VR) and augmented reality (AR) devices, the optical system plays a vital role. Most traditional optical systems use single or multiple optical lenses to fold the light path, but when applied to small-screen displays, a strong optical focal length is required to achieve the bending of light, which will lead to a large field curvature phenomenon and difficult-to-eliminate ghosting problems. In addition, the ghosting caused by the contact between the optical film and the air will affect the user's wearing experience. The non-adjustable focus of the optical system will also lead to visual convergence accommodation conflict (VAC), and long-term wearing may cause dizziness. Utility Model Content

[0003] The purpose of this application is to provide a new technical solution for an optical system and a display device.

[0004] In a first aspect, the present application provides an optical system. The optical system comprises a multifocal lens, a lens group, a polarization reflection element, a phase retarder and a beam splitter arranged along the same optical axis; wherein the phase retarder is located between the beam splitter and the polarization reflection element;

[0005] The lens group includes at least one lens, and at least one lens in the lens group is located between the light path formed by the beam splitter, the phase retarder and the polarized reflective element;

[0006] The multifocal lens is used to enable the optical system to achieve optical power changes within the entire field of view, so as to reasonably allocate the optical power of different fields of view.

[0007] Optionally, the optical system further comprises a display screen, wherein the display screen is located on a side of the lens group facing away from the multifocal lens, the display screen is a small-sized screen, and the height of the display screen is ≤34 mm.

[0008] Optionally, the lens group includes a first lens and a second lens arranged along the optical axis, and the first lens and the second lens have different refractive indices;

[0009] Wherein, the first lens is located on a side close to the multifocal lens, and the second lens is located on a side close to the display screen.

[0010] Optionally, the first lens and the second lens are glued to each other.

[0011] Optionally, the optical system further comprises a polarization element, wherein the polarization element is located on either side of the polarization reflection element.

[0012] Optionally, the light splitting element is arranged on a surface of the second lens close to the display screen;

[0013] The phase retarder is arranged on the bonding surface of the first lens and the second lens;

[0014] The polarizing element and the polarizing reflecting element are stacked and disposed on a surface of the second lens away from the display screen.

[0015] Optionally, the light splitting element is arranged on the bonding surface of the first lens and the second lens;

[0016] The phase retarder, the polarization reflection element and the polarization element are sequentially stacked and arranged on a surface of the first lens away from the display screen.

[0017] Optionally, the light splitting element is arranged on a surface of the second lens close to the display screen;

[0018] The polarization reflection element, the polarization element and the phase retarder are stacked and arranged on the bonding surface of the first lens and the second lens.

[0019] Optionally, the multifocal lens enables the optical system to achieve a power variation from 0.34D in the edge field of view to 0.67D in the center field of view.

[0020] In a second aspect, the present application provides a display device, the display device comprising:

[0021] casing; and

[0022] An optical system as described in the first aspect.

[0023] The beneficial effects of this application are:

[0024] The embodiment of the present application provides a new type of optical system, which adopts a combination of a lens group and a multifocal lens, and is equipped with a polarized reflection element, a phase retarder and a beam splitter. The introduction of the multifocal lens allows the user to view distant objects through the edge field of view and observe nearby objects through the center field of view, thereby realizing a continuous zoom function within the entire field of view; and the combination of the lens group, the polarized reflection element, the phase retarder and the beam splitter, combined with a reasonable optical path arrangement, realizes the effective folding and transmission of light, which is not only conducive to improving the imaging quality, but also can form a compact optical structure design. The optical system provided by the embodiment of the present application not only brings a clearer visual experience to the user, but also greatly improves the wearing comfort of the user, and brings a more convenient and comfortable use experience to the user.

[0025] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 1 One of the structural schematic diagrams of the optical system provided in the embodiment of the present application;

[0028] Figure 2 for Figure 1 A dot array diagram of the provided optical system;

[0029] Figure 3 for Figure 1 The modulation transfer function (MTF) curve of the optical system provided;

[0030] Figure 4 for Figure 1 Provided field curvature and distortion plots of the optical system;

[0031] Figure 5 for Figure 1 Provide vertical chromatic aberration diagram of the optical system;

[0032] Figure 6 The second structural diagram of the optical system provided in the embodiment of the present application;

[0033] Figure 7 for Figure 6 A dot array diagram of the provided optical system;

[0034] Figure 8 for Figure 6 The modulation transfer function (MTF) curve of the optical system provided;

[0035] Fig. 9 for Figure 6 Provided field curvature and distortion plots of the optical system;

[0036] Fig.10 for Figure 6 Provide vertical chromatic aberration diagram of the optical system;

[0037] Fig.11 A power distribution diagram of a multifocal lens provided in an embodiment of the present application;

[0038] Fig.12 Schematic diagram of the zoom principle of the multifocal lens provided in an embodiment of the present application.

[0039] Description of reference numerals:

[0040] 1. First lens; 11. First surface; 12. Second surface; 2. Second lens; 21. Third surface; 22. Fourth surface; 3. Multifocal lens; 4. Display screen; 5. Beam splitter; 6. Phase retarder; 7. Polarized reflective element; 8. Polarizing element; 01. Human eye. DETAILED DESCRIPTION

[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 of components and steps, numerical expressions and numerical values ​​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 in nature and is in no way intended to limit the present application, its application, or uses.

[0043] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

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

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

[0046] The optical system and display device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0047] According to one embodiment of the present application, an optical system is provided, which is particularly suitable for use in a display device, especially a virtual reality (VR) display device, to provide an immersive visual experience. However, the application scope of this optical system is not limited to VR display devices, and it can also be flexibly applied to various other types of display devices to meet different visual needs and technical requirements.

[0048] The optical system proposed in the embodiment of the present application, see Figure 6 , Fig.11 and Fig.12The optical system includes a multifocal lens 3, a lens group, a polarized reflection element 7, a phase retarder 6 and a beam splitter 5 arranged along the same optical axis; wherein the phase retarder 6 is located between the beam splitter 5 and the polarized reflection element 7; the lens group includes at least one lens, and at least one lens in the lens group is located between the light path formed by the beam splitter 5, the phase retarder 6 and the polarized reflection element 7; the multifocal lens 3 is used to enable the optical system to achieve optical power changes within the entire field of view, so as to reasonably allocate the optical power of different fields of view.

[0049] The optical system proposed in the embodiment of the present application shows an optical structure with unique design and function. This optical system mainly includes the following key optical elements: multi-focal lens 3, lens group, polarization reflection element 7, phase retarder 6 and beam splitter 5. These optical elements are arranged along the same optical axis in a set order and work together to achieve a specific optical effect.

[0050] Multifocal lenses3: Also known as multifocal lenses, see Fig.11 , which is a lens whose optical power varies with the field of view. This lens is designed with multiple focal planes so that objects in different areas can be imaged at the same or different positions. In the optical system provided in the embodiment of the present application, see Fig.12 The multifocal lens 3 is used to continuously zoom objects within a certain range (such as 1m to 3m), which means that the user can see distant objects from the edge field of view through this multifocal lens 3, and can also clearly observe nearby objects through the central field of view, achieving a visual effect of continuous zoom within the entire field of view, and there is no need for algorithm control to adjust the focal length or switch lenses, which can simplify the design of the optical system.

[0051] In the present application, by reasonably allocating the optical focal length of different fields of view, the multifocal lens 3 significantly improves the practicality of the optical system and can bring a more natural and comfortable visual experience to the user.

[0052] Lens group: includes at least one lens, and at least one lens is located in the folded light path formed by the beam splitter 5, the phase retarder 6 and the polarized reflective element 7, which plays a key role in focusing and imaging. Moreover, by selecting appropriate lens materials and optical parameters, the lens group can also correct light distortion and chromatic aberration, and improve the clarity and contrast of imaging.

[0053] Polarized reflective element 7: used to change the polarization state or direction of light. Specifically, the polarized reflective element 7 is a polarized reflective film that reflects horizontal linear polarized light and transmits vertical linear polarized light, or a polarized reflective film that reflects linear polarized light at any other specific angle and transmits linear polarized light in a direction perpendicular to the angle. In the optical system provided in the embodiment of the present application, the polarized reflective element 7 is used to cooperate with the phase retarder 6 to achieve specific optical functions, such as changing the propagation path of light or enhancing the contrast of an image.

[0054] Phase retarder 6: used to change the polarization state of light. For example, phase retarder 6 is used to convert linear polarized light into circular polarized light, or to convert circular polarized light into linear polarized light. In the optical system of the present application, the phase retarder 6 is designed to be located between the beam splitter element 5 and the polarized reflective element 7, and the phase retarder 6 is, for example, a quarter wave plate. Of course, the phase retarder 6 can be set to other phase retarder films as needed.

[0055] Beam splitter 5: The beam splitter 5 is, for example, a semi-transparent and semi-reflective film, which allows a portion of light to be transmitted and another portion of light to be reflected. It should be noted that the reflectivity and transmittance of the beam splitter 5 can be flexibly adjusted according to specific needs, and this is not limited in the embodiments of the present application.

[0056] The synergistic effect of the beam splitter 5, the phase retarder 6 and the polarized reflective element 7 can accurately control the propagation and polarization state of light, thereby obtaining a clear and accurate image. The phase retarder 6 is located between the beam splitter 5 and the polarized reflective element 7, and plays a role in regulating the phase of light, which helps to achieve accurate control of light.

[0057] The optical system provided in the embodiment of the present application improves the imaging quality. Specifically, through the synergistic effect of the lens group, the multifocal lens 3, the polarized reflection element 7, the phase retarder 6 and the beam splitter 5, the optical system can optimize the transmission and focusing of light, thereby improving the clarity and contrast of the imaging.

[0058] The optical system provided in the embodiment of the present application realizes a continuous zoom function, which is mainly due to the introduction of the multifocal lens 3, which enables the optical system to achieve continuous zoom within the entire field of view, greatly enhancing the flexibility of the optical system.

[0059] In this application, through reasonable light path arrangement and optical element combination, the optical system realizes a compact optical structure design, making the entire optical system more portable and easy to integrate into various optical display devices. The compact optical structure design and optimized visual experience make the optical system more suitable for long-term wear and improve the wearing comfort of users.

[0060] The optical system provided in the embodiment of the present application realizes a continuous change in the optical focal length from the edge field of view to the center field of view, so that the user can see objects at different distances under different fields of view without adjusting the focal length. This design is particularly important for applications such as virtual reality (VR) and mixed reality (MR) because they need to provide users with a more natural and realistic visual experience. In addition, by optimizing the design of the lens group, polarized reflection element 7, phase retarder 6 and spectroscopic element 5, this optical system can also achieve higher imaging quality, further improving the user's wearing comfort and user experience.

[0061] Furthermore, the present application combines a pre-designed multifocal lens 3, and through clever distribution of optical power, achieves focal length changes in different fields of view. This means that users can easily capture distant objects with the edge field of view, while focusing on nearby details in the center field of view. As the viewing angle gradually turns to the center, the object seems to move from far to near, presenting a continuous zoom effect.

[0062] In addition, it should be noted that see Figure 1 When the multifocal lens 3 is not introduced into the optical system, the entire optical system can also show good optical performance. After adding the multifocal lens 3, the optical system can be endowed with zoom functionality while ensuring the optical performance.

[0063] In some examples of this application, see Figure 6 The optical system further includes a display screen 4, which is located on a side of the lens group away from the multifocal lens 3. The display screen 4 is a small-sized screen, and the height of the display screen 4 is ≤34 mm.

[0064] In the example provided in this application, a key element, display screen 4, is introduced. In combination with the optical structure of the optical system described above, see Figure 6 The display screen 4 is located on the side of the lens group away from the multifocal lens 3. Such a layout allows the light emitted from the display screen 4 to be regulated by the lens group and the multifocal lens 3, and finally presents a clear image in the human eye 01 or the target position.

[0065] The display screen 4 is a small screen, the height of which is ≤34 mm. Due to the small size of the display screen 4, this design means that the entire optical system can be more compact and lightweight, suitable for integration into various portable devices, such as virtual reality (VR) smart glasses.

[0066] In a specific example, the half-height size of the display screen 4 is 12.5 mm, and the height direction of the display screen 4 is a direction perpendicular to the optical axis.

[0067] In the existing technology, the design of folded optical path faces multiple challenges when used with a small screen. First, in order to effectively bend the light into the user's eyes, a strong optical focal length is required, but this is often accompanied by significant field curvature problems, which are difficult to completely eliminate by conventional means; secondly, due to the presence of the interface between the optical film material and the air, "ghosting" is prone to occur, which not only affects the imaging quality, but also reduces the user's wearing experience. More importantly, existing designs often do not have a focusing function, which leads to the problem of visual convergence accommodation conflict (VAC), and long-term wearing can easily cause dizziness and discomfort.

[0068] In response to the above challenges, the embodiment of the present application proposes an innovative optical system design, that is, to optimize the optical system by introducing a multifocal lens 3. This design cleverly solves the problems caused by small-size screens in the optical system. The application of multifocal lenses allows the field curvature phenomenon to be effectively reduced while ensuring the light bending effect, thereby improving the imaging quality. In addition, through the carefully designed lens combination and light path layout, the generation of "ghost images" can be reduced, providing users with a clearer and more comfortable visual experience.

[0069] More importantly, the multifocal lens 3 in the present application also has a focusing function. This means that the user can adjust the focal length as needed, thereby avoiding the problem of visual convergence accommodation conflict (VAC). This innovative design not only improves the wearing comfort of the user, but also expands the application range of the optical system, making it more suitable for different scenarios and needs.

[0070] In the optical system provided in the embodiment of the present application, since the display screen 4 is small in size, the volume and weight of the entire optical system are reduced, thereby improving the portability of the display device using the optical system. This is particularly important for display devices that need to be worn for a long time.

[0071] In the optical system provided in the embodiment of the present application, although the size of the display screen 4 is small, through the careful design and optimization of the multifocal lens 3 and the lens group, it is possible to ensure a sufficient field of view (the field of view FOV can reach 100°) within a limited display area, thereby providing a wide field of view for the user.

[0072] In addition, the small-sized display screen 4, combined with the sophisticated optical architecture, can ensure that the image maintains high clarity during transmission and display, thereby enhancing the user's visual experience. The small-sized display screen 4 has lower power consumption, which helps to extend the battery life of the device, especially for portable display devices that rely on battery power. The manufacturing cost of the small-sized display screen 4 is also relatively low, which helps to reduce the cost of the entire optical system.

[0073] In a specific example of the present application, the multifocal lens 3 includes a multifocal surface, and the curvature C3 of the multifocal surface is 0.00581 mm.

[0074] In the example provided in this application, the design of the multifocal lens 3 includes multiple focal planes, and the curvature C3 of one of the multifocal planes is set to 0.00581 mm. This particular curvature selection has an important impact on the optical performance of the lens, as follows:

[0075] First, the multi-focal surface design enables the lens to provide clear imaging at different distances. In this example of the present application, the curvature C3 is designed to be 0.00581 mm, so that the lens has optimized optical performance at a certain distance (1m to 3m). This design allows the lens to achieve multiple focal length adjustments while maintaining a small size and weight, thereby meeting the visual needs at different distances.

[0076] Secondly, the optical architecture presented in this application can achieve a change from an object with a peripheral field of view of 0.34D to an object with a central field of view of 0.67D. This means that the lens can provide clear imaging in a wider field of view, especially for objects located at the edge of the field of view. This performance improvement is crucial to enhancing the user's visual experience, especially in scenes that require frequent switching of visual distances.

[0077] The design of the multifocal lens 3 in this example realizes the functions of providing clear imaging and continuous zooming in a wider field of view (such as a field of view of 100°) by designing the curvature C3 of the multifocal surface. At the same time, the excellent imaging quality further enhances the user's visual experience.

[0078] It should be noted that the curvature C3 of the multifocal surface of the multifocal lens 3 includes but is not limited to the above-mentioned 0.00581, and can also be designed to other values ​​as needed, and this application does not impose any specific limitation on this.

[0079] See also Fig.11 , Fig.11 The optical power distribution diagram of the multifocal lens 3 is shown, the field of view-optical focus of the forward light path, and the optical power is evenly distributed, which can achieve a change from an object at the edge of the field of view of 0.34D to an object at the center of 0.67D, allowing the wearer to achieve continuous zoom of objects within the range of 1.5m-3m.

[0080] See also Fig.12 The zooming principle of the multifocal lens 3 provided in the embodiment of the present application is to realize zooming by utilizing the rotation of the eyeball of the human eye 01 and the change of the field of view.

[0081] In some examples of this application, see Figure 6The lens group includes a first lens 1 and a second lens 2 arranged along the optical axis, and the refractive indexes of the first lens 1 and the second lens 2 are different; wherein the first lens 1 is located on a side close to the multifocal lens 3, and the second lens 2 is located on a side close to the display screen 4.

[0082] In this example of the present application, the lens group design consists of two lenses with different refractive indices: a first lens 1 and a second lens 2, which are arranged adjacent to each other along the optical axis, wherein the first lens 1 is located on the side close to the multifocal lens 3, and the second lens 2 is located on the side close to the display screen 4. This makes the optical system provided by the present application a two-lens folded light path, and is matched with a multifocal lens 3 and a small-sized display screen 4. This design of the lens group can bring the following effects:

[0083] (1) Optimizing light refraction: Since the first lens 1 and the second lens 2 have different refractive indices, they also have different refraction effects on light. This design can adjust the propagation direction and focusing effect of light as needed, ensuring that the light can be accurately focused on the multifocal lens 3 after passing through the lens group, thereby optimizing the imaging quality.

[0084] (2) Effectively reduce chromatic aberration: Chromatic aberration is caused by the different refractive indices of light of different wavelengths when passing through the lens. By using a combination of lenses with different refractive indices, chromatic aberration can be reduced to a certain extent, so that light of different colors can be better converged after passing through the lens group, improving the clarity and color reproduction of the image.

[0085] (3) Improving imaging quality: The difference in refractive index between the first lens 1 and the second lens 2 can optimize the imaging quality to a certain extent, making the imaging clearer.

[0086] In addition, since different lenses have different refractive indices, the lens assembly can be flexibly adjusted according to specific application scenarios and requirements. For example, by selecting a suitable lens material and refractive index combination, it can adapt to light of different wavelengths, display screens of different brightness, or different visual requirements.

[0087] In some examples of this application, see Figure 1 and Figure 6 , the first lens 1 and the second lens 2 are glued to each other.

[0088] The lens group used in this example of the present application is, for example, a cemented lens group. Specifically, the lens group is formed by cementing a first lens 1 and a second lens with different refractive indices together.

[0089] When the first lens 1 and the second lens 2 are glued together, the following benefits can be achieved:

[0090] (1) Gluing two lenses together can eliminate or reduce reflection and scattering caused by air gaps, thereby improving the optical performance of the lens group. This design helps to reduce light loss and improve imaging clarity.

[0091] (2) Since the two lenses have different refractive indices, they refract light differently. By properly selecting lens materials and refractive indices and gluing them together, the refraction and focusing of light can be optimized, chromatic aberration can be reduced, and the color accuracy and clarity of the image can be ensured.

[0092] (3) The refractive index of the lens material is related to the wavelength of the incident light, which causes different colors of light to be refracted to different degrees, thereby causing distortion. The lens group can more accurately control the refraction path of light by combining two lenses with different refractive indices, thereby reducing distortion. For example, in the lens group, one lens may weaken light of a certain color, while the other lens will strengthen this light. Through this mutual offset effect, the distortion caused by chromatic aberration can be reduced. And gluing the two lenses together can also help reduce the existence of "ghost images".

[0093] (4) By gluing two lenses together, the assembly process of the lens group can be simplified. Compared with installing multiple lenses separately, the glued lens group is more stable and reliable, and reduces assembly errors. By gluing two or more lenses together, a single optical element can be formed, which also reduces the number of components in the optical system. This helps to reduce the complexity and cost of the system and improve the overall optical performance.

[0094] (5) The gluing method makes the two lenses tightly connected, improving the structural stability of the entire lens group. This structure makes the lens group more durable, able to withstand greater external pressure and temperature changes, and reduces the problem of optical system failure caused by vibration.

[0095] The optical solution provided in the embodiment of the present application realizes precise control of light transmission through a double-cemented lens piece and a folded optical path solution. Among them, the imaging lens adopts a special cemented design, which helps to significantly reduce chromatic aberration, distortion and "ghosting" phenomenon, and accurately distributes the focal length through the multifocal lens 3, which can reduce problems such as field curvature and VAC-induced dizziness, greatly improving the comfort of the wearer.

[0096] It is worth mentioning that the optical system provided in the embodiment of the present application has a field of view (FOV) that can be extended to 100°.

[0097] In addition, regarding the lens group in the optical system, it includes but is not limited to the use of two glued lenses. It is also possible to use a single lens, or introduce more than two lenses. The lenses can be kept at a certain distance or glued, and this is not limited in the present application.

[0098] In some examples of this application, see Figure 1 and Figure 6 The optical system further includes a polarization element 8 , which is located on either side of the polarization reflection element 7 .

[0099] The introduction of the polarization element 8 can reduce the interference of stray light and help improve the contrast and clarity of the image, which is crucial for enhancing the virtual reality experience because stray light will interfere with the authenticity of the virtual image viewed by the user.

[0100] The polarizing element 8 is, for example, a polarizing film.

[0101] In some examples of this application, see Figure 1 and Figure 6 The beam splitter 5 is disposed on the surface of the second lens 2 close to the display screen 4; the phase retarder 6 is disposed on the bonding surface of the first lens 1 and the second lens 2; the polarizing element 8 and the polarizing reflecting element 7 are stacked and disposed on the surface of the second lens 2 away from the display screen 4.

[0102] See also Figure 1 and Figure 6 The first lens 1 includes a first surface 11 and a second surface 12 , the first surface 11 is far away from the display screen 4 , and the second surface 12 is close to the display screen 4 .

[0103] See also Figure 1 and Figure 6 The second lens 2 includes a third surface 21 and a fourth surface 22 , the third surface 21 is adjacent to the second surface 12 of the first lens 1 , and the fourth surface 22 is close to the display screen 4 .

[0104] In some examples provided in the present application, the beam splitter 5 is plated or mounted on the fourth surface 22 of the second lens 2, and the beam splitter 5 is, for example, a semi-transparent and semi-reflective film. The phase retarder 6 is attached to the bonding surface of the two lenses, and the composite film material composed of the polarizing element 8 and the polarizing reflective element 7 is attached to the first surface 11 of the first lens 1, that is, the phase retarder 6 and the polarizing reflective element 7 are attached to different surfaces respectively, which is designed in consideration of the simplicity of the process. Among them, the phase retarder 6 is, for example, a quarter wave plate, the polarizing reflective element 7 is a polarizing reflective film, and the polarizing element 8 is a polarizing film.

[0105] In the example of the present application, the beam splitter 5, the phase retarder 6 and the polarization reflection element 7 are arranged on three surfaces of two glued lenses, which can simplify the assembly process and enable the installation of multiple optical elements in one assembly.

[0106] In some examples of the present application, the beam splitter 5 is disposed on the bonding surface of the first lens 1 and the second lens 2; the phase retarder 6, the polarizing reflection element 7 and the polarizing element 8 are sequentially stacked and disposed on the surface of the first lens 1 away from the display screen 4.

[0107] In this example of the present application, the beam splitter element 5 is plated on the bonding surface of the first lens 1 and the second lens 2. At the same time, the phase retarder 6, the polarization reflection element 7 and the polarization element 8 are arranged on the first surface 11 of the first lens 1, so that the light path is folded inside the first lens 1.

[0108] The light splitting element 5 is, for example, a semi-transparent and semi-reflective film.

[0109] The phase retarder 6 is, for example, a quarter wave plate, the polarization reflection element 7 is a polarization reflection film, and the polarization element 8 is a polarization film.

[0110] Since the phase retarder 6, the polarization reflection element 7 and the polarization element 8 form a composite film, this design simplifies the assembly process of the optical system and does not require additional support members or fixing structures, which reduces costs and improves the stability and reliability of the optical system.

[0111] Optionally, an anti-reflection film layer may be introduced into the composite film material, and the anti-reflection film layer can reduce the reflection of light on the lens surface, thereby increasing the light transmittance, which can not only improve the brightness of the image, but also improve the overall optical performance of the optical system.

[0112] In some examples of the present application, the beam splitter element 5 is disposed on the surface of the second lens 2 close to the display screen 4; the polarized reflection element 7, the polarizing element 8 and the phase delay device 6 are stacked and disposed on the bonding surface of the first lens 1 and the second lens 2.

[0113] In this example of the present application, the beam splitter 5 is plated on the fourth surface 22 of the second lens 2, and at the same time, the phase retarder 6, the polarization reflection element 7 and the polarization element 8 are arranged on the bonding surface of the first lens 1 and the second lens 2. Considering the process factors, the composite film composed of the polarization reflection element 7, the polarization element 8 and the phase retarder 6 can be attached to the bonding surface of the two lenses to achieve the flipping of light on the bonding surface.

[0114] The light splitting element 5 is, for example, a semi-transparent and semi-reflective film.

[0115] The phase retarder 6 is, for example, a quarter wave plate, the polarization reflection element 7 is a polarization reflection film, and the polarization element 8 is a polarization film.

[0116] Since the phase retarder 6, the polarization reflection element 7 and the polarization element 8 form a composite film, this design simplifies the assembly process of the optical system and does not require additional support members or fixing structures, which reduces costs and improves the stability and reliability of the optical system.

[0117] Optionally, an anti-reflection film layer may be introduced into the composite film material, and the anti-reflection film layer can reduce the reflection of light on the lens surface, thereby increasing the light transmittance, which can not only improve the brightness of the image, but also improve the overall optical performance of the optical system.

[0118] In some examples of this application, see Fig.11 The multifocal lens 3 enables the optical system to achieve a focal power change from 0.34D in the edge field of view to 0.67D in the center field of view.

[0119] A multifocal lens3 is a lens designed with multiple focal zones that allow the user to see clearly at different distances.

[0120] In the present application, the optical power of the multifocal lens 3 varies from the edge field of view (referring to the edge part of the lens) to the central field of view (the central part of the lens). Specifically, the optical power of the edge field of view is, for example, 0.34D, while the optical power of the central field of view is 0.67D.

[0121] The optical power is a physical quantity that describes the refractive power of a lens, and its unit is diopter (D for short). A diopter of 1D means that the lens can focus parallel light rays at a distance of 1 meter from the lens. The higher the optical power, the stronger the refractive power of the lens, and the more distant the light rays can be focused.

[0122] In this example of the present application, the optical power of the multifocal lens 3 gradually increases from the edge field of view to the central field of view, which means that the refractive power of the multifocal lens 3 is stronger in the central part. This design allows the user to select areas of different optical powers on the multifocal lens 3 by rotating the eyeball when viewing objects at different distances, thereby obtaining clear vision.

[0123] In summary, the multifocal lens 3 in this example of the present application provides a solution that facilitates users to obtain clear vision at different distances by achieving a change in optical power from the edge field of view to the center field of view.

[0124] In addition, optionally, a protective glass is provided on the light-emitting surface of the display screen 4 .

[0125] The protective glass in front of the display screen 4 can effectively isolate dust, fingerprints and other dirt from the outside, thereby keeping the surface of the display screen 4 clean. This is crucial for the optical system, because any dirt on the screen surface may affect light transmission and image quality. By introducing the protective glass, the example of this application significantly improves the tolerance of the optical system to dirt on the surface of the display screen 4, ensuring the stability and reliability of the optical system.

[0126] The protective glass can not only isolate dirt, but also prevent the display screen 4 from physical damage such as scratches and collisions. This is of great significance for extending the service life of the display screen 4 and improving the overall durability of the device.

[0127] The light emitted by the display screen 4 should be circularly polarized light. If the light emitted by the display screen 4 is not circularly polarized light, the light needs to be converted. For example, a special superimposed element can be provided on the light-emitting side of the display screen 4, and the superimposed element can include, for example, two quarter-wave plates and a polarizing film provided between the two quarter-wave plates. Through the synergistic effect between the optical films in the superimposed elements, the superimposed elements can ensure that the light emitted by the display screen 4 is circularly polarized light. This design is crucial to ensuring the imaging stability and image quality of the optical system, because circularly polarized light has better anti-interference and higher clarity during transmission.

[0128] According to the above specific example, the propagation of light in the optical system is as follows, see Figure 6:The light is emitted from the display screen 1 as circularly polarized light, and after passing through the beam splitter 5 (semi-transmissive and semi-reflective film, BS film) on the fourth surface 22 of the second lens 2, the energy becomes 50%, and after passing through the second lens 2, it passes through the phase retarder 6 (quarter wave plate, QWP) on the third surface 21 of the second lens 2 and is emitted as linearly polarized light; the polarization direction of the linearly polarized light is perpendicular to the transmission axis of the designed polarizing reflective element 7 (polarizing reflective film, RP film), and when it is incident on the polarizing reflective element 7 on the first surface 11 of the first lens 1, it will be reflected back to the second surface 12 of the first lens 1, and then pass through the phase retarder 6 (quarter wave plate, QWP) again. , QWP) becomes circular polarized light, and then passes through the second lens 2 and is incident on the beam splitter element 5 (semi-transmissive and semi-reflective film, BS film). 25% of the light is reflected back to the cemented lens group composed of the first lens 1 and the second lens 2, and becomes linear polarized light after passing through the phase retarder 6 (quarter wave plate, QWP) again. Due to the reflection, the direction of the circularly polarized light changes, and the polarization direction of the linear polarized light will be parallel to the transmission axis of the polarizing reflective element 7 (polarizing reflective film, RP film). Then, the light can pass through the polarizing element 8 (polarizing film, LP film) on the first surface 11 of the first lens 1 and the multifocal lens 3 and then enter the human eye 01.

[0129] The optical system provided by the present application is further described below through Example 1 and Example 2.

[0130] Example 1

[0131] See also Figure 1 , the optical system comprises a polarizing element 8, a polarizing reflecting element 7, a second lens 2, a phase retarder 6, a first lens 1, a beam splitting element 5 and a display screen 4 which are sequentially arranged along the same optical axis;

[0132] The first lens 1 and the second lens 2 are glued together to form a glued lens set, the first lens 1 and the second lens 2 have different refractive indices, the first lens 1 is located on a side close to the multifocal lens 3, and the second lens 2 is located on a side close to the display screen 4;

[0133] The beam splitter 5 is disposed on the surface of the second lens 2 close to the display screen 4; the phase retarder 6 is disposed on the bonding surface of the first lens 1 and the second lens 2; the polarizing element 8 and the polarizing reflective element 7 are stacked and disposed on the surface of the second lens 2 away from the display screen 4;

[0134] The display screen 4 is a small-sized screen, and the half height of the display screen 4 is 12.5 mm.

[0135] The curvature of the bonding surface between the first lens 1 and the second lens 2 is -0.091 mm.

[0136] Table 1 shows the specific optical parameters of the optical system of this embodiment 1.

[0137] Table 1

[0138]

[0139] It should be noted that the multifocal lens 3 is not introduced into the optical system shown in the present embodiment 1.

[0140] The optical system provided in this embodiment 1 has an optical performance as shown in Figures 2 to 5 As shown: Figure 2 is a schematic diagram of the point diagram. Figure 3 is the MTF curve graph, Figure 4 is the field curvature distortion diagram, Figure 5 This is the vertical axis chromatic aberration diagram.

[0141] The spot diagram refers to a diffuse diagram formed by many light rays emitted from one point after passing through the optical system. Due to aberration, their intersection points with the image plane are no longer concentrated at the same point, but are scattered in a certain range. It is used to evaluate the imaging quality of the projection optical system. Figure 2 The optical system provided in this embodiment 1 has a spot size of less than 8 microns in the entire field of view and provides clear imaging.

[0142] MTF is a quantitative description of the resolution of an optical system. A larger value indicates a higher resolution at the current frequency. In this embodiment 1, see Figure 3 It can be seen that at 80 line pairs per millimeter, the MTF value is still 0.30, which shows that the optical system has good resolution.

[0143] Field curvature and distortion reflect the difference in the position of the clear imaging surface in different fields of view. Figure 4 It can be seen that, in the optical system provided in this embodiment 1, the maximum field curvature does not exceed 0.08 mm, and the distortion does not exceed 30%.

[0144] Chromatic aberration reflects the difference in the imaging position of light of different wavelengths in different fields of view on the image plane. The chromatic aberration of the optical system provided in this embodiment 1 is shown in Figure 5 As shown, the maximum color difference is less than 90μm.

[0145] Example 2

[0146] See also Figure 6The optical structure of the present embodiment 2 is that, on the basis of the above-mentioned embodiment 1, a multifocal lens 3 is introduced on the side close to the human eye 01, the multifocal lens 3 includes a multifocal surface, and the curvature C3 of the multifocal surface is 0.00581 mm; the multifocal lens 3 can enable the optical system to achieve a focal power change from 0.34D at the edge of the field of view to 0.67D at the center of the field of view. After adding the multifocal lens 3, the field of view angle can be stabilized at 90°, which shows the stability of the optical structure.

[0147] Table 2 shows the specific optical parameters of the optical system of this embodiment 2.

[0148] Table 2

[0149]

[0150] The optical system provided in this embodiment 2 has an optical performance as shown in Figure 7 Fig.10 As shown: Figure 7 is a schematic diagram of the point diagram. Figure 8 is the MTF curve graph, Fig. 9 is the field curvature distortion diagram, Fig.10 This is the vertical axis chromatic aberration diagram.

[0151] The spot diagram refers to a diffuse diagram formed by many light rays emitted from one point after passing through the optical system. Due to aberration, their intersection points with the image plane are no longer concentrated at the same point, but are scattered in a certain range. It is used to evaluate the imaging quality of the projection optical system. Figure 2 The optical system provided in this embodiment 1 has a spot size of less than 38 microns in the entire field of view and a clear image.

[0152] MTF is a quantitative description of the resolution of an optical system. A larger value indicates a higher resolution at the current frequency. In this embodiment 1, see Figure 3 It can be seen that at 80 line pairs per millimeter, the MTF value is still 0.10, which shows that the optical system has good resolution.

[0153] Field curvature and distortion reflect the difference in the position of the clear imaging surface in different fields of view. Figure 4 It can be seen that, in the optical system provided in this embodiment 1, the maximum field curvature does not exceed 0.5 mm, and the distortion does not exceed 20%.

[0154] Chromatic aberration reflects the difference in the imaging position of light of different wavelengths in different fields of view on the image plane. The chromatic aberration of the optical system provided in this embodiment 1 is shown in Figure 5 As shown, the maximum color difference is less than 110μm.

[0155] It should be noted that the difference between Example 1 and Example 2 is that the multifocal lens 3 in Example 2 is omitted, and the optical system provided by Example 1 can be used alone and has a better optical imaging effect.

[0156] According to another embodiment of the present application, a display device is provided, which includes: a housing and the optical system as described above.

[0157] The display device provided in the embodiment of the present application is, for example, a VR display device.

[0158] The specific implementation of the display device of the embodiment of the present application can refer to the above-mentioned embodiments of the optical system, so it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0159] The above embodiments focus on 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. Considering the simplicity of the text, they will not be repeated here.

[0160] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. An optical system, characterized in that: The invention comprises a multifocal lens (3), a lens group, a polarized reflection element (7), a phase retarder (6) and a beam splitter (5) arranged along the same optical axis; wherein the phase retarder (6) is located between the beam splitter (5) and the polarized reflection element (7); The lens group includes at least one lens, and at least one lens in the lens group is located between the light path formed by the beam splitting element (5), the phase retarder (6) and the polarized reflection element (7); The multifocal lens (3) is used to enable the optical system to achieve optical power changes within the entire field of view, so as to reasonably distribute the optical power of different fields of view.

2. The optical system according to claim 1, characterized in that The optical system further comprises a display screen (4), wherein the display screen (4) is located on a side of the lens group away from the multifocal lens (3), the display screen (4) is a small-sized screen, and the height of the display screen (4) is ≤34 mm.

3. The optical system according to claim 2, characterized in that The lens group comprises a first lens (1) and a second lens (2) arranged along the optical axis, and the refractive index of the first lens (1) and the refractive index of the second lens (2) are different; The first lens (1) is located on a side close to the multifocal lens (3), and the second lens (2) is located on a side close to the display screen (4).

4. The optical system according to claim 3, characterized in that The first lens (1) and the second lens (2) are glued to each other.

5. The optical system according to claim 4, characterized in that The optical system further comprises a polarizing element (8), wherein the polarizing element (8) is located on either side of the polarizing reflecting element (7).

6. The optical system according to claim 5, characterized in that The light splitting element (5) is arranged on a surface of the second lens (2) close to the display screen (4); The phase retarder (6) is arranged on the bonding surface of the first lens (1) and the second lens (2); The polarizing element (8) and the polarizing reflecting element (7) are stacked and arranged on a surface of the second lens (2) away from the display screen (4).

7. The optical system according to claim 5, characterized in that The light splitting element (5) is arranged on the bonding surface of the first lens (1) and the second lens (2); The phase retarder (6), the polarized reflection element (7) and the polarization element (8) are sequentially stacked and arranged on a surface of the first lens (1) away from the display screen (4).

8. The optical system according to claim 5, characterized in that The light splitting element (5) is arranged on a surface of the second lens (2) close to the display screen (4); The polarized reflection element (7), the polarization element (8) and the phase retarder (6) are stacked and arranged on the bonding surface of the first lens (1) and the second lens (2).

9. The optical system according to claim 1, characterized in that The multifocal lens (3) can enable the optical system to achieve a focal power change from 0.34D in the peripheral field of view to 0.67D in the central field of view.

10. A display device, characterized in that: include: shell; and An optical system as claimed in any one of claims 1 to 9.

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