Optical system and optical display apparatus

Abstract

Provided in the embodiments of the present application are an optical system and an optical display apparatus. The optical system comprises a polarization reflection element, a phase retarder and a light splitting element, which are arranged along the same optical axis, wherein the phase retarder is located between the light splitting element and the polarization reflection element. The optical system further comprises a first lens, wherein the first lens comprises a first surface and a second surface, the light splitting element being arranged on one side of the first surface, and the polarization reflection element and the phase retarder being stacked on the second surface. The first lens satisfies: |SAG / (T*D)|≤0.3, wherein D is the effective clear semi-aperture of the second surface, T is the corresponding lens thickness under the effective clear semi-aperture D, and SAG is the depth of the second surface under the effective clear semi-aperture D.

Description

Optical system and optical display device TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of optical imaging technology, and more particularly, to an optical system and an optical display device. BACKGROUND

[0002] With the continuous progress of virtual reality (VR) technology, users have increasingly high demands for high definition. To achieve higher resolution and smaller screen size, the design and manufacturing standards of optical systems have also been improved. In the Pancake optical scheme, curved film pasting technology is widely used to improve image quality. However, this technology also faces challenges, that is, curved film pasting lenses are prone to deformation due to the pulling of the film material, thereby affecting the final imaging effect. SUMMARY

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

[0004] In a first aspect, the present application provides an optical system. The optical system comprises a polarization reflection element, a phase retarder and a light splitting element arranged along the same optical axis, and the phase retarder is located between the light splitting element and the polarization reflection element.

[0005] The optical system further comprises a first lens, the first lens comprising a first surface and a second surface, the light splitting element being arranged on one side of the first surface, and the polarization reflection element and the phase retarder being arranged in layers on the second surface.

[0006] The first lens satisfies |SAG / (T*D)|≤0.3, wherein D is an effective half-entrance pupil diameter of the second surface, T is a lens thickness corresponding to the effective half-entrance pupil diameter D, and SAG is a depth of the second surface at the effective half-entrance pupil diameter D.

[0007] Optionally, the thickness of the first lens at the maximum effective half-entrance pupil diameter is ≥3mm.

[0008] Optionally, the slope K of each point in the half-entrance pupil range of the second surface satisfies K≥0 or K≤0; wherein the surface shape of the second surface is symmetric about the optical axis.

[0009] Optionally, the D is an effective half-entrance pupil diameter of the second surface (42), and 10mm<D<30mm.

[0010] The T is a lens thickness corresponding to the effective half-entrance pupil diameter D, and 1mm<T<10mm.

[0011] Optionally, the optical system comprises a display screen, and the first surface of the first lens is located on a side close to the display screen.

[0012] Optionally, the first surface is convex, and the light splitting element is arranged on the first surface.

[0013] Optionally, the optical system further comprises a polarizing element, and the polarizing element is arranged on a side of the polarizing reflector away from the phase retarder.

[0014] Optionally, the polarizing element, the polarizing reflector and the phase retarder are stacked to form a stacked element.

[0015] Optionally, the optical system further comprises a second lens, and the second lens is located between the first lens and the display screen, an absolute value of an optical power of the second lens is less than 0.03, and a thickness of the second lens is less than or equal to 6 mm.

[0016] Optionally, the optical system further comprises a third lens, and the third lens is located between the second lens and the display screen; an absolute value of a total optical power of the second lens and the third lens is less than 0.03, and a total thickness of the second lens and the third lens is less than or equal to 6 mm.

[0017] Optionally, at least one layer of protective glass is arranged on a light emitting surface side of the display screen, and a total thickness of the protective glass is greater than or equal to 0.5 mm.

[0018] Optionally, the optical system further comprises a composite film, and the composite film comprises a first phase retardation film, a second phase retardation film and a polarizing film arranged between the first phase retardation film and the second phase retardation film, and the composite film is arranged on a surface of the protective glass away from the display screen.

[0019] In a second aspect, the present application provides an optical display device, and the optical display device comprises:

[0020] a housing; and

[0021] the optical system as described in the first aspect.

[0022] The present application has the following beneficial effects:

[0023] The optical system provided by the embodiments of the present application can be applied to, for example, a VR optical display technology, and the core of the optical system is to solve the problem that an optical film material is easily pulled on a lens when a film is pasted in a traditional optical design by finely regulating the relationship between the surface shape and the thickness of a curved film-pasted lens (for example, a first lens), which often leads to deformation of the lens and further seriously affects the imaging quality. In addition, the optical solution provided by the present application sets a reasonable range of the thickness of the film-pasted lens, enhances the structural rigidity of the lens, and enables the lens to effectively resist unnecessary stress generated by the optical film material, thereby greatly reducing the surface shape error caused by deformation and ensuring the imaging performance of the optical system.

[0024] Other features of the present specification and its advantages will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present specification and, together with the description, serve to explain the principles of the present specification.

[0026] FIG. 1 is a structural schematic diagram of an optical system provided by an embodiment of the present application;

[0027] FIG. 2 is a schematic diagram of a film-pasting mode provided by an embodiment of the present application;

[0028] FIG. 3 is a schematic diagram of a film-pasting mode provided by an embodiment of the present application;

[0029] FIG. 4 is a structural schematic diagram of a first lens provided by an embodiment of the present application;

[0030] FIG. 5 is a point array diagram of the optical system provided by FIG. 1;

[0031] FIG. 6 is a modulation transfer function (MTF) curve diagram of the optical system provided by FIG. 1;

[0032] FIG. 7 is a field curvature and distortion diagram of the optical system provided by FIG. 1;

[0033] FIG. 8 is a sagittal chromatic aberration diagram of the optical system provided by FIG. 1;

[0034] FIG. 9 is a structural schematic diagram of an optical system provided by an embodiment of the present application;

[0035] FIG. 10 is a point array diagram of the optical system provided by FIG. 9;

[0036] FIG. 11 is a modulation transfer function (MTF) curve diagram of the optical system provided by FIG. 9;

[0037] FIG. 12 is a field curvature and distortion diagram of the optical system provided by FIG. 9;

[0038] FIG. 13 is a plot of the sagittal chromatic aberration of the optical system provided in FIG. 9;

[0039] FIG. 14 is a schematic view of a third structure of an optical system provided in embodiments of the present application;

[0040] FIG. 15 is a spot array diagram of the optical system provided in FIG. 14;

[0041] FIG. 16 is a modulation transfer function (MTF) curve diagram of the optical system provided in FIG. 14;

[0042] FIG. 17 is a field curvature and distortion diagram of the optical system provided in FIG. 14;

[0043] FIG. 18 is a plot of the sagittal chromatic aberration of the optical system provided in FIG. 14.

[0044] BRIEF DESCRIPTION OF DRAWINGS 1, display screen; 2, first protective glass; 3, second protective glass; 321, anti-reflection film; 322, first phase retardation film; 323, polarizing film; 324, second phase retardation film; 4, first lens; 41, first surface; 411, light splitting element; 42, second surface; 421, anti-reflection film; 422, polarizing element; 423, polarizing reflection element; 424, phase retarder; 5, second lens; 51, third surface; 52, fourth surface; 6, third lens; 61, fifth surface; 62, sixth surface; 01, human eye. DETAILED DESCRIPTION

[0045] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements, numerical expressions, and numerical values of components and steps set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0046] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application or its application or uses.

[0047] Techniques and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification where appropriate.

[0048] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0049] It should be noted that like numbers and letters refer to like items throughout the drawings, and once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0050] The optical system and the optical display device provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0051] According to an embodiment of the present application, an optical system is provided, which is particularly suitable for use in an optical display device, particularly a virtual reality (VR) display device, to provide an immersive visual experience. However, the application range of the optical system is not limited to the VR display device, and it can also be flexibly applied to other various types of display devices to meet different visual requirements and technical requirements.

[0052] The optical system provided by the embodiments of the present application, referring to FIG. 1, FIG. 9 and FIG. 14, comprises a polarization reflection element 423, a phase retarder 424 and a light splitting element 411 arranged along the same optical axis, and the phase retarder 424 is located between the light splitting element 411 and the polarization reflection element 423, referring to FIG. 2; the optical system further comprises a first lens 4, which comprises a first surface 41 and a second surface 42, the light splitting element 411 is arranged on one side of the first surface 41, and the polarization reflection element 423 and the phase retarder 424 are arranged in layers on the second surface 42; the first lens 4 satisfies: |(SAG) / (T*D)|≤0.3, wherein D is the effective half-aperture diameter of the second surface 42, T is the corresponding lens thickness at the effective half-aperture diameter D, and SAG is the depth of the second surface 42 at the effective half-aperture diameter D.

[0053] The optical system provided by the embodiments of the present application, from the optical architecture, comprises the following optical elements:

[0054] The polarization reflection element 423 is a polarization reflector that reflects horizontally linearly polarized light and transmits vertically linearly polarized light, or any other specific angle linearly polarized light and transmits linearly polarized light in the direction perpendicular to the angle. That is, the polarization reflection element 423 is responsible for reflecting or transmitting according to the polarization state of the light. In the optical system provided by the embodiments of the present application, it interacts with the specific state of the polarized light (such as S light or P light) to achieve specific path control of the light.

[0055] The phase retarder 424 can be used to change the polarization state of the light, such as converting linearly polarized light into circularly polarized light, or converting circularly polarized light into linearly polarized light. The phase retarder 424 in the present application is, for example, a quarter-wave plate, which is located between the light splitting element 411 and the polarization reflection element 423, and adjusts the phase of the light to ensure that the light can be correctly reflected or transmitted in the subsequent path.

[0056] The light splitting element 411 is, for example, a thin film or coating with specific light splitting properties for reflecting and transmitting incident light in a certain ratio. Specifically, the light splitting element 411 is a semi-transmissive and semi-reflective film that transmits a portion of light and reflects another portion of light. It should be noted that the reflectivity and transmissivity of the light splitting element 411 can be flexibly adjusted according to specific needs, which is not limited in the embodiments of the present application.

[0057] The first lens 4 is one of the core components of the optical system, which includes two main surfaces: a first surface 41 and a second surface 42, as shown in FIG. 1. The light splitting element 411 is, for example, disposed on one side of the first surface 41 or directly on the first surface 41, and the polarization reflection element 423 and the phase retarder 424 are stacked on the second surface 42.

[0058] In the present application, the design of the first lens 4 meets a specific constraint condition: |SAG / (T*D)|≤0.3mm -1 , SAG is the depth of the second surface 42 at the effective half-diameter D of the light passing through, and T is the lens thickness corresponding to the effective half-diameter D of the light passing through. The core purpose of this carefully designed constraint condition is to ensure that the surface of the lens film can maintain extreme smoothness, and at the same time, through reasonable control of the lens thickness, the overall structural strength of the lens is enhanced. Through this design, the problem of optical film material pulling and deforming the lens during film pasting, which is a common problem in traditional VR optical systems, is effectively solved.

[0059] The pulling and deformation of the optical film material often causes surface shape error of the lens, which seriously affects the imaging quality. The constraint condition designed in the present application effectively suppresses this adverse effect, so that the lens can maintain its original shape as much as possible even when subjected to the pulling action of the optical film material, thereby ensuring the imaging clarity and stability of the optical system.

[0060] Regarding the constraint condition of the first lens 4 mentioned in the present application: |SAG / (T*D)|≤0.3, it is essentially a quantitative restriction on the relationship between the surface shape, thickness, and effective light passing diameter of the lens film, aiming to optimize the optical performance and structural strength of the lens. The specific analysis is as follows:

[0061] Referring to FIG. 4, SAG represents the depth of the second surface 42 of the first lens 4 at the effective half-diameter D of the light passing through, which reflects the curvature or degree of concave of the lens surface within a certain aperture range. T represents the lens thickness corresponding to the effective half-diameter D of the light passing through, which is the physical dimension of the lens in the direction perpendicular to the optical axis. D represents the effective half-diameter of the light passing through, which is half of the diameter of the effective area of the lens that allows light to pass through.

[0062] The inequality |SAG / (T*D)|≤0.3 defines the proportional relationship between SAG and the product of T and D. The core idea is to control the relative relationship between the curve depth of the film-coated lens (i.e., the first lens 4) and its thickness and aperture to achieve the optimization purpose.

[0063] A smaller |SAG / (T*D)| value means that the lens has a relatively flat curve change in the effective light transmission aperture range, which helps to achieve a smoother film-coated surface and reduce optical problems caused by sharp curve changes.

[0064] In addition, through reasonable lens thickness design, the lens can increase the resistance to optical film material pulling and reduce lens deformation caused by optical film material stress, thereby maintaining the accuracy of the lens surface and improving the imaging quality.

[0065] The optical design scheme provided in the present application ultimately aims to improve the imaging clarity and stability of the entire optical system to ensure that users have a high-quality visual experience.

[0066] The optical system provided in the embodiments of the present application reduces the stretching (or pulling deformation) of the optical film material on the lens itself by constraining the surface shape and thickness of the curved film-coated lens (i.e., satisfying the condition |SAG / (T*D)|≤0.3). This design reduces lens surface shape errors, thereby ensuring imaging quality. This provides an effective means to solve the problem of image quality degradation caused by the curved film-coated lens being easily deformed by the pulling of the optical film material in traditional VR optical systems.

[0067] In the optical system provided in the embodiments of the present application, the precise layout and combination of the polarization reflection element 423 (transmits P light and reflects S light), the phase retarder 424 (such as a quarter-wave plate), and the light splitting element 411, etc. optical elements, through polarization and phase control, make the light maintain high clarity and contrast during transmission, further improving image quality.

[0068] In some examples of the present application, the thickness of the first lens 4 at the maximum effective light transmission aperture is ≥3mm.

[0069] In this example of the present application, the thickness of the first lens 4 at its maximum effective light transmission aperture is designed to be greater than or equal to 3mm. Such a design choice mainly brings the following technical effects, especially enhancing the structural strength of the first lens 4 (i.e., the film-coated lens). Specifically as follows:

[0070] (1) Enhance the structural strength: by ensuring that the thickness of the first lens 4 at the maximum effective light transmission aperture is at least 3mm, the physical strength and rigidity of the lens are significantly increased. This makes the lens less likely to deform or be damaged when subjected to external forces (such as pulling force during the film coating process).

[0071] (2) Improve the stability of the film: Lenses are often coated with a film to protect them or provide additional optical properties. Thicker lenses can better withstand the tension generated during the film coating process, reducing the risk of deformation caused by pulling, thereby improving the flatness and stability of the film.

[0072] (3) Extend the service life: Thicker lens structures not only improve their ability to withstand stress during the film coating process, but also may enhance their durability and impact resistance during long-term use, thereby extending the overall service life of the lens.

[0073] In this example of the present application, the thickness of the first lens 4 at the maximum effective clear aperture of the film is ≥3mm, which is an effective design aimed at enhancing the strength of the lens structure, improving the stability of the film and prolonging the service life. This is particularly important for optical applications that require high reliability and stability.

[0074] In some examples of the present application, referring to FIG. 4, the slope K of each point in the semi-aperture range of the second surface 42 satisfies: K≥0 or K≤0; wherein the surface of the second surface 42 is symmetric about the optical axis.

[0075] When the surface of the second surface 42 is symmetric about the optical axis, this symmetry helps to ensure uniform distribution of the film on the lens surface, as the film material will be uniformly constrained when attached.

[0076] In this example of the present application, the slope K represents the degree of inclination of the second surface 42 at a certain point. When K≥0 or K≤0, this design means that the inclination direction of the surface is consistent throughout the semi-aperture range, without sharp changes or inflection points. This consistent inclination direction helps the film material to stretch or compress smoothly when attached, as the film material can stretch or compress along a uniform inclination direction without encountering sudden changes in resistance.

[0077] In combination with the above two points, the design of the symmetric surface and the limitation of the slope K work together to make the film more smoothly attached to the second surface 42. The smoothness of the film surface is crucial to ensure the close fit between the film and the lens and to reduce defects such as bubbles, wrinkles, etc. during the film coating process.

[0078] That is, by reasonably designing the slope K of each point in the semi-aperture range of the second surface 42 to satisfy certain conditions and making the surface symmetric about the optical axis, the smoothness of the film surface can be effectively improved, thereby improving the quality and stability of the film. This is very important for optical applications that require high-quality film.

[0079] In some examples of the present application, D is the effective half-diameter of the second surface 42, and 10mm < D < 30mm; T is the corresponding lens thickness at the effective half-diameter D, and 1mm < T < 10mm.

[0080] In the present application, D is the effective half-diameter of the second surface 42, i.e. the maximum range of half-diameter that the lens can allow light to pass through. The range constrained in the present application is 10mm < D < 30mm, which means that the lens has a relatively large diameter of light, suitable for optical systems that require a larger field of view or light quantity. A larger diameter of light also helps to reduce edge effects such as aberration and light scattering, thereby improving the imaging quality.

[0081] In the present application, T is the corresponding lens thickness at the effective half-diameter D. The range constrained in the present application is 1mm < T < 10mm, which indicates that the thickness of the lens is moderate, neither too thin nor too thick. A moderate lens thickness helps to balance the weight and strength of the lens, while also helping to control the optical performance such as aberration and dispersion of the lens.

[0082] In combination with the range of D and T, it can be seen that the selection of these parameters is to optimize the optical performance and structural strength of the lens. The large diameter of light and the moderate thickness of the lens work together to ensure that the lens has good imaging quality, appropriate weight and strength, and is easy to process and manufacture.

[0083] In some examples of the present application, referring to FIG. 1, FIG. 9 and FIG. 14, the optical system comprises a display screen 1, and the first surface 41 of the first lens 4 is located on the side close to the display screen 1.

[0084] The optical system further comprises a display screen 1 for emitting imaging light.

[0085] As shown in FIG. 1, FIG. 9 and FIG. 14, the first surface 41 of the first lens 4 is located on the side close to the display screen 1, and the second surface 42 is located on the side away from the display screen 1. On this basis, the light splitting element 411 is located on the side of the first surface 41 of the first lens 4, which receives the light emitted by the display screen 1 and performs light splitting.

[0086] Referring to FIG. 14, when only the first lens 4 is used in the optical system, since the light splitting element 411 is immediately adjacent to the first surface 41 of the first lens 4, the light emitted from the display screen 1 can be immediately received and processed by the light splitting element 411. This layout reduces the transmission distance of light in the air, reduces the loss of light energy during transmission, and thus improves the light splitting efficiency.

[0087] In addition, by precisely controlling the distance between the light splitting element 411 and the first surface 41 of the first lens 4, the propagation path of light can be effectively managed, reducing aberrations and distortions caused by excessive optical path or improper refraction angles. This helps to improve the imaging quality, providing users with a clearer and more realistic visual experience.

[0088] In some examples of the present application, referring to FIG. 1, FIG. 9 and FIG. 14, the first surface 41 is convex, and the light splitting element 411 is disposed on the first surface 41.

[0089] Placing the light splitting element 411 directly on the first surface 41 of the first lens 4 greatly improves the integration of the optical system. This tightly integrated structure not only reduces the gap between components, but also simplifies the overall architecture of the optical system, making the entire optical system more compact and portable.

[0090] The close combination of the light splitting element and the lens surface helps to reduce aberrations and distortions caused by excessive optical path or improper refraction angles. This design can ensure that the light remains high in imaging quality after splitting, providing users with a clearer and more realistic visual experience. In addition, the close connection of the light splitting element and the lens surface helps to reduce the position deviation of the optical elements caused by vibration or external impact. This improvement in stability not only prolongs the service life of the optical system, but also ensures the stability and reliability of the optical system in various use environments, such as VR optical display devices.

[0091] In the present application, the light splitting element 411 is disposed on the convex surface (first surface 41), which can further regulate the behavior of light by utilizing the geometric properties of the convex surface. The specific analysis is as follows:

[0092] Optical power is a measure of the focusing power of a lens on light. The first surface 41, as the main surface providing optical power, means that it plays a key role in the entire optical system, responsible for focusing light to a predetermined position. The combination of the light splitting element 411 and the convex surface makes the change of light direction more accurate and controllable. This helps to optimize the overall performance of the optical system, reduce aberrations and improve imaging quality.

[0093] Since the first surface 41 provides both the main optical power and serves as a carrier for the light splitting element 411, this also helps to reduce the number of elements in the optical system. Fewer components mean simpler optical system structure, lower manufacturing cost and higher reliability.

[0094] In some examples of the present application, referring to FIG. 1 and FIG. 2, the optical system further comprises a polarization element 422, which is disposed on the side of the polarization reflection element 423 away from the phase retarder 424.

[0095] The polarization element 422, such as a polarizing film, can selectively transmit or reflect light vibrations in a specific direction.

[0096] In the optical system, by introducing the polarization element 422 and arranging it on the side of the polarization reflection element 423 facing away from the phase retarder 424, this design can reduce the interference of stray light.

[0097] Specifically, stray light is usually unwanted light caused by reflection, scattering or refraction of light at the interface. By arranging the polarization element 422 on the side of the polarization reflection element 423 facing away from the phase retarder 424, stray light that is not consistent with the direction of the main light can be filtered out, reducing their interference with the imaging quality. This helps to improve the contrast and clarity of the image, making the user's virtual image viewing more realistic and immersive.

[0098] The reduction of stray light directly improves the imaging quality. In virtual reality applications, high-contrast and high-clarity images are the basis for providing high-quality visual experiences. The introduction of the polarization element 422 enables the system to better control the propagation direction and state of light, reducing unnecessary light interference and improving the overall image rendering effect.

[0099] The core of virtual reality technology is to provide a realistic visual experience. The presence of stray light can destroy this sense of realism, making the user feel uncomfortable. By introducing a polarization element to reduce the interference of stray light, the realism and immersion of the virtual reality experience can be significantly improved, allowing users to focus more on the content in the virtual environment.

[0100] In addition to directly improving image quality, the introduction of the polarization element 422 also helps to improve the overall efficiency of the optical system. By reducing the propagation and energy loss of stray light, the optical system can more efficiently utilize light energy and concentrate more energy on the imaging process.

[0101] In some examples of the present application, referring to FIG. 2, the polarization element 422, the polarization reflection element 423 and the phase retarder 424 are stacked to form a stacked element.

[0102] As shown in FIG. 2, the polarization element 422, the polarization reflection element 423 and the phase retarder 424 are stacked to form a stacked element, which brings significant technical effects, as follows:

[0103] (1) By stacking multiple optical elements together, a highly integrated stacked element is formed, which not only simplifies the structure of the optical system, but also significantly reduces the volume of the optical system. This integrated design helps to achieve a thinner virtual reality device, improving user comfort and portability.

[0104] (2) The design of the stacked elements makes the relative positions between the elements more stable, which is crucial for ensuring the good imaging performance of the optical system under different use environments and conditions.

[0105] (3) The close arrangement of the elements in the stacked elements helps to optimize the propagation path of light, reducing the energy loss and aberration of light during transmission between elements. In particular, the close cooperation of the phase retarder with the polarization element and the polarization reflection element can more accurately control the polarization state and reflection direction of light, thereby improving the imaging quality.

[0106] (4) The traditional optical system needs to install and adjust each element one by one, while the design of the stacked elements simplifies the assembly process, only needs to install the stacked elements as a whole unit into the system, thereby improving the production efficiency.

[0107] Optionally, referring to FIG. 2, an anti-reflection film 421 can also be introduced into the stacked elements, which can reduce the reflection of light on the lens surface, thereby increasing the transmittance of light. This not only can improve the brightness of the image, but also can improve the overall optical performance of the optical system.

[0108] In some examples of the present application, referring to FIG. 1, the lens group further comprises a second lens 5 located between the first lens 4 and the display screen 1, the absolute value of the optical power of the second lens 5 is <0.03, and the thickness of the second lens 5 is ≤6mm.

[0109] As shown in FIG. 1, by adding the second lens 5 and locating it between the first lens 4 and the display screen 1, this design aims to further improve the imaging quality.

[0110] Specifically, after adding the second lens 5, the light emitted from the display screen 1 can be further refracted and focused, thereby optimizing the distribution of light. This helps to reduce the scattering and loss of light during air propagation, so that the light is more concentratedly projected into the user's eyes, which helps to improve the brightness and clarity of the image.

[0111] The introduction of the second lens 5 can also be used to correct various aberrations present in the optical system, such as spherical aberration, coma, and distortion, etc. By reasonably designing the curvature, thickness and material parameters of the second lens, the aberration of the entire optical system can be better controlled, thereby improving the imaging quality and reducing the blurring and distortion of the image.

[0112] In this example provided by the present application, the absolute value of the optical power of the second lens 5 is controlled to be within the range of less than 0.03. This means that its focusing ability on light rays is relatively weak and does not significantly change the propagation direction of light rays, but is sufficient for fine tuning. A lower optical power helps to reduce the overall aberration of the optical system, making the imaging clearer.

[0113] The thickness of the second lens 5 is limited to within 6mm. Such thickness limitation helps to reduce the overall size of the optical system, making it more compact.

[0114] In some cases, increasing the second lens 5 also helps to expand the field of view angle of the optical system. The field of view angle is the maximum range of view that a user can see through the virtual reality device, which is crucial for improving the user experience. By reasonably arranging and designing the second lens, the user's field of view can be expanded while ensuring the imaging quality, so that he can more realistically experience the virtual environment.

[0115] In some examples of the present application, referring to FIG. 9, the lens group further includes a third lens 6 located between the second lens 5 and the display screen 1; the absolute value of the total optical power of the second lens 5 and the third lens 6 is <0.03, and the total thickness of the second lens 5 and the third lens 6 is ≤6mm.

[0116] Referring to FIG. 9, three lenses: the first lens 4, the second lens 5 and the third lens 6 can also be used in the optical system provided by the embodiments of the present application. By introducing the third lens 6 and placing it between the second lens 5 and the display screen 1, this design not only continues the technical effects described in the previous example, but also brings more complex and delicate light control capabilities.

[0117] Specifically, through the combined action of the three lenses, the refraction, focusing and diffusion of light rays can be more accurately controlled, thereby further optimizing the distribution of light rays and the imaging quality. Such fine control helps to reduce the loss and interference of light rays during transmission, and improves the brightness and clarity of the image.

[0118] The combination of the three lenses provides more degrees of freedom and flexibility for aberration correction. By reasonably designing the curvature, thickness and material parameters of each lens, various aberrations such as spherical aberration, coma, distortion, etc. in the optical system can be more effectively corrected, thereby further improving the imaging quality. The improvement of this aberration correction capability is of great significance for improving the resolution, contrast and color restoration of the image, etc.

[0119] Optical designers can adjust the relative positions, parameters, and configurations of the three lenses according to actual needs to achieve different imaging effects and functional requirements. This design flexibility helps meet the needs of different users and application scenarios, improving the product's applicability and competitiveness.

[0120] It should be noted that in the design of the present application, the absolute value of the overall optical power of the added lens is controlled to be less than 0.03. The light can be fine-tuned without significantly changing the direction of light propagation. Lower optical power helps reduce the overall aberration of the optical system, making the imaging clearer.

[0121] In addition, it is particularly pointed out in this example of the present application that the total thickness of the added mirror lens is designed to be within 6mm. This is an important design constraint aimed at maintaining the compactness of the optical system.

[0122] In some examples of the present application, at least one layer of protective glass is provided on the side of the light-emitting surface of the display screen 1, and the total thickness of the protective glass is ≥0.5mm.

[0123] The optical system is provided with protective glass (number ≥1 layer, total thickness ≥0.5mm), which effectively improves the optical scheme's tolerance to dirt on the surface of the display screen 1 and reduces the risk of affecting the imaging quality due to screen contamination.

[0124] For example, referring to FIG. 1, the protective glass includes a first protective glass 2 and a second protective glass arranged in layers, and the total thickness of the first protective glass 2 and the second protective glass 3 is ≥0.5mm.

[0125] Specifically, the first protective glass 2 and the second protective glass 3 in front of the display screen 1 can effectively isolate dust, fingerprints and other contaminants from the outside, thereby maintaining the cleanliness of the display screen 1 surface. This is crucial for the optical system, as any dirt on the screen surface can affect light transmission and image quality. By introducing two layers of protective glass, the optical system's tolerance to dirt on the display screen 1 surface is significantly improved, ensuring the stability and reliability of the optical system.

[0126] The first protective glass 2 and the second protective glass 3 not only isolate dirt, but also effectively prevent the display screen 1 from being scratched, collided or physically damaged. This is of great significance to prolong the service life of the display screen 1 and improve the overall durability of the device.

[0127] In some examples of the present application, referring to FIG. 1 and FIG. 3, the optical system further comprises a composite film, which includes a first phase retardation film 322, a second phase retardation film 324, and a polarizing film 323 disposed between the first phase retardation film 322 and the second phase retardation film 324, and the composite film is disposed on the surface of the protective glass facing away from the display screen 1.

[0128] In this example of the present application, the combination of the first phase retardation film 322 (as a quarter-wave plate) and the polarizing film 323 in the composite film can effectively eliminate the reflected stray light of the display screen 1 itself. After the light is emitted from the display screen 1, the circularly polarized light is converted into linearly polarized light of a specific direction through the conversion of the first phase retardation film 322. Subsequently, the polarizing film 323 only allows linearly polarized light of this specific direction to pass through, while blocking linearly polarized light of other directions (including stray light reflected by the screen). Finally, the second phase retardation film 324 converts the linearly polarized light into circularly polarized light for subsequent optical processing. This process significantly reduces the interference of the reflected light of the display screen 1 on the imaging quality, improving the clarity and contrast of the image.

[0129] Through the regulation of the composite film, the loss of light during transmission is reduced, thereby improving the utilization rate of light. This helps to improve the brightness of the image.

[0130] The composite film also helps to enhance the color performance of the image. By optimizing the polarization state and phase of the light, the dispersion and chromatic aberration of the light during transmission can be reduced, making the colors of the image more vivid and accurate. This is of great significance to improving the realism and immersion of virtual reality experience.

[0131] Optionally, an anti-reflection film 321 is introduced in the composite film, which is located on the side of the first phase retardation film 322 facing away from the polarizing film 323.

[0132] The main function of the anti-reflection film 321 is to reduce the reflection loss of light at the interface, thereby increasing the transmittance of light. In an optical system, each reflection of light will cause a part of energy loss, reducing the overall efficiency of the optical system. By adding the anti-reflection film 321 on the back of the first phase retardation film 322, the proportion of light reflected back to the system from this interface can be significantly reduced, so that more light can pass through and enter the subsequent optical elements, thereby improving the brightness and clarity of the image.

[0133]

[0134] ​The introduction of the anti-reflection film 321 also helps to optimize the overall performance of the optical system. Due to the reduction of the reflection loss of light, the energy distribution inside the optical system is more uniform, which is beneficial to improve the uniformity and consistency of imaging. In addition, the anti-reflection film 321 can also correct the dispersion and chromatic aberration of light to some extent, so that the color performance of the image is more accurate and bright.

[0135] The optical system provided by the embodiments of the present application is described below with reference to FIG. 1. The light propagates as follows:

[0136] The display screen 1 emits circularly polarized light, which is transmitted through the first protective glass 2, the second protective glass 3 and the second lens 5, becomes linearly polarized light (S light) through the phase retarder 424 (such as a quarter-wave plate) of the second surface 42 of the first lens 4, is reflected by the polarization reflection element 423, becomes circularly polarized light again through the phase retarder 424, is reflected by the light splitting element 411 of the first surface 41 of the first lens 4, becomes linearly polarized light (P light) for the third time through the phase retarder 424, is transmitted through the polarization element 422 and the anti-reflection film 421, and then enters the human eye 01 to form an image.

[0137] The optical system provided by the embodiments of the present application is described below with reference to FIG. 1, FIG. 9 and FIG. 14. The material used in the optical lens has a refractive index and dispersion coefficient range of 1.4 < n < 2.0 and 20 < v < 75, which helps to reduce dispersion and other aberrations and improve the stability and imaging quality of the optical system.

[0138] The first lens 4 and the second lens 5 in the optical system shown in FIG. 1 are described as follows.

[0139] The central thickness of the first lens 4 ranges from 1 mm to 10 mm, for example, and includes two optical surfaces, i.e., the first surface 41 and the second surface 42, which are aspherical or planar. The second surface 42 is provided with a film layer structure, as shown in FIG. 2, which includes an anti-reflection film 421, a phase retarder 424 (a quarter-wave plate), a polarization reflection element 423 (transmits P light and reflects S light), and a polarization element 422 (transmits P light). The first surface 41 is provided with a light splitting element 411 (a semi-transparent and semi-reflective film).

[0140] The central thickness of the second lens 5 ranges from 1 mm to 8 mm, for example, and includes two optical surfaces, i.e., the third surface 51 and the fourth surface 52, which are aspherical or planar and have an anti-reflection film.

[0141] The optical system provided by the present application is further described below by way of Examples 1 to 3.

[0142] Example 1

[0143] Referring to FIGS. 1-4, the optical system comprises a polarizing element 422, a polarizing reflecting element 423, a phase retarder 424, a first lens 4, a light splitting element 411, a second lens 5, a second protective glass 3, a first protective glass 2 and a display screen 1 arranged along the same optical axis;

[0144] The polarizing element 422, the polarizing reflecting element 423 and the phase retarder 424 form a superposition element and are arranged on the surface (second surface 42) of the first lens 4 away from the display screen 1, and the light splitting element 411 is arranged on the surface (first surface 41) of the first lens 4 close to the display screen 1.

[0145] The second protective glass 3 and the first protective glass 2 are arranged in layers and are arranged on the light-emitting surface of the display screen 1, and the total thickness of the two protective glasses is ≥0.5 mm.

[0146] A composite film can also be arranged on the second protective glass 3, referring to FIG. 3, the composite film comprises a first phase retardation film 322, a second phase retardation film 324 and a polarizing film 323 arranged between the first phase retardation film 322 and the second phase retardation film 324.

[0147] The first lens 4 satisfies |SAG / (T*D)| is 0.26; wherein SAG is -6.10 m, T is 1.85 mm and D is 12.6 mm.

[0148] Table 1 shows the specific optical parameters of the optical system of the present embodiment 1.

[0149] Table 1

[0150] The optical performance of the optical system provided by the present embodiment 1 can be shown in FIGS. 5-8: FIG. 5 is a schematic diagram of a point column diagram, FIG. 6 is an MTF curve diagram, FIG. 7 is a field curvature distortion diagram and FIG. 8 is a vertical axis chromatic aberration diagram.

[0151] The point column diagram refers to a diffused pattern formed by a point emitting many light rays after passing through the optical system, and the intersection points with the image plane are no longer concentrated in the same point due to aberration, which is used to evaluate the imaging quality of the projection optical system. Referring to FIG. 5, the maximum value of the image point in the point column diagram of the optical system provided by the present embodiment 1 is less than 15 μm.

[0152] The MTF curve diagram is a modulation transfer function diagram, and the imaging clarity of the optical system is represented by the contrast of black and white lines. Referring to FIG. 6, the MTF of the optical system provided by the present embodiment 1 is >0.8 at 20 lp / mm.

[0153] Referring to Fig. 7, the optical system provided in Embodiment 1 has a maximum distortion of less than 40% at 1 field of view.

[0154] The axial chromatic aberration, also referred to as the magnification chromatic aberration, is mainly caused by a complex color chief ray in the object side, which is changed into multiple rays when exiting the image side due to the chromatic aberration of the refractive system, and the difference between the focal point positions of the blue light and the red light on the image plane. Referring to Fig. 8, the optical system provided in Embodiment 1 has a maximum chromatic aberration of less than 180 μm.

[0155] Embodiment 2

[0156] Referring to Fig. 9, the difference between Embodiment 2 and Embodiment 1 described above is that a third lens 6 is added between the second lens 5 and the display screen 1, and the second lens 5 is a plane mirror; the first lens 4 satisfies |SAG / (T*D)| is 0.07, wherein SAG is -2.30 mm, T is 1.97 mm, and D is 17.23 mm.

[0157] Table 2 shows the specific optical parameters of the optical system in Embodiment 2.

[0158] Table 2

[0159] The optical performance of the optical system provided in Embodiment 2 can be shown in Figs. 10-13: Fig. 10 is a schematic diagram of a point spread diagram, Fig. 11 is an MTF curve diagram, Fig. 12 is a field curvature distortion diagram, and Fig. 13 is an axial chromatic aberration diagram.

[0160] Referring to Fig. 10, the optical system provided in Embodiment 2 has a maximum value of an image point in the point spread diagram of less than 16 m.

[0161] Referring to Fig. 11, the optical system provided in Embodiment 2 has an MTF of greater than 0.6 at 20 lp / mm.

[0162] Referring to Fig. 12, the optical system provided in Embodiment 2 has a maximum distortion of less than 40% at 1 field of view, and the distortion is very small.

[0163] Referring to Fig. 13, the optical system provided in Embodiment 2 has a maximum chromatic aberration of less than 180 μm.

[0164] Embodiment 3

[0165] Referring to Fig. 14, the difference between Embodiment 3 and Embodiment 1 described above is that only one first lens 4 is used in the optical system; and the first lens 4 satisfies |SAG / (T*D)| is 0.15, wherein SAG is -2.37 mm, T is 1.06 mm, and D is 15.30 mm.

[0166] Table 3 shows the specific optical parameters of the optical system in Embodiment 3.

[0167] Table 3

[0168] The optical system provided in Embodiment 3 has the optical performance as shown in FIGS. 15-18: FIG. 15 is a schematic diagram of a spot diagram, FIG. 16 is a curve diagram of MTF, FIG. 17 is a diagram of field curvature distortion, and FIG. 18 is a diagram of axial chromatic aberration.

[0169] Referring to FIG. 15, the optical system provided in Embodiment 3 has the maximum value of an image point in a spot diagram less than 30 μm.

[0170] Referring to FIG. 16, the optical system provided in Embodiment 3 has MTF greater than 0.1 at 20 lp / mm.

[0171] Referring to FIG. 17, the optical system provided in Embodiment 3 has the maximum distortion occurring at 1 field of view, and the absolute value is less than 40%, and the distortion is very small.

[0172] Referring to FIG. 18, the optical system provided in Embodiment 3 has the maximum chromatic aberration value less than 180 μm.

[0173] According to another embodiment of the present application, there is provided an optical display device, comprising: a housing and an optical system as described above.

[0174] The optical display device provided in the embodiments of the present application is, for example, a VR display device.

[0175] The specific implementation of the optical display device of the embodiments of the present application can refer to the above-described embodiments of the optical system, and thus has all the beneficial effects brought by the technical solutions of the above-described embodiments, which will not be described herein again.

[0176] In the above embodiments, the differences between the embodiments are mainly described, and the different optimization features between the embodiments can be combined to form a more optimal embodiment as long as they are not contradictory. In view of the brevity of the writing, they will not be described herein again.

[0177] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, but not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. An optical system characterized by comprising: The optical system comprises a polarization reflection element (423), a phase retarder (424) and a light splitting element (411) arranged along the same optical axis, and the phase retarder (424) is located between the light splitting element (411) and the polarization reflection element (423); The optical system further comprises a first lens (4) comprising a first surface (41) and a second surface (42), the light splitting element (411) is arranged on one side of the first surface (41), and the polarization reflection element (423) and the phase retarder (424) are arranged in layers on the second surface (42); The first lens (4) satisfies: |SAG / (T*D)|≤0.3, wherein D is the effective half light diameter of the second surface (42), T is the corresponding lens thickness at the effective half light diameter D, and SAG is the depth of the second surface (42) at the effective half light diameter D.

2. The optical system of claim 1, wherein The thickness of the first lens (4) at the maximum effective light diameter is ≥3mm.

3. The optical system of claim 1, wherein, The slope K of each point in the half diameter range of the second surface (42) satisfies: K≥0 or K≤0; wherein the surface type of the second surface (42) is symmetric about the optical axis.

4. The optical system of claim 1, wherein, D is the effective half light diameter of the second surface (42), and 10mm<D<30mm; T is the corresponding lens thickness at the effective half light diameter D, and 1mm<T<10mm.

5. The optical system of claim 1, wherein, The optical system comprises a display screen (1), and the first surface (41) of the first lens (4) is located on the side close to the display screen (1).

6. The optical system of claim 5, wherein, The first surface (41) is convex, and the light splitting element (411) is arranged on the first surface (41).

7. The optical system of claim 1, wherein The optical system further comprises a polarization element (422) arranged on the side of the polarization reflection element (423) away from the phase retarder (424).

8. The optical system of claim 7, wherein, The polarization element (422), the polarization reflection element (423) and the phase retarder (424) are stacked to form a combined element.

9. The optical system of claim 5, wherein, The optical system further comprises a second lens (5) located between the first lens (4) and the display screen (1), the absolute value of the optical power of the second lens (5) is <0.03, and the thickness of the second lens (5) is ≤6mm.

10. The optical system of claim 9, wherein, The optical system further comprises a third lens (6) located between the second lens (5) and the display screen (1), the absolute value of the total optical power of the second lens (5) and the third lens (6) is <0.03, and the total thickness of the second lens (5) and the third lens (6) is ≤6mm.

11. The optical system of claim 5, wherein, At least one layer of protective glass is arranged on the light emitting side of the display screen (1), and the total thickness of the protective glass is ≥0.5mm.

12. The optical system of claim 11, wherein, The optical system further comprises a composite film material, the composite film material comprising a first phase delay film (322), a second phase delay film (324), and a polarizing film (323) disposed between the first phase delay film (322) and the second phase delay film (324), the composite film material being disposed on a surface of the protective glass facing away from the display screen (1).

13. An optical display device, characterized by Comprising: a housing; the optical system of any one of claims 1-12.

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