Optical system and head-mounted display device

Abstract

The embodiments of the present disclosure provide an optical system and a head-mounted display device. The optical system accoriding to the embodiments of the present disclosure may comprise: a display element, a lens, a spectroscope and a reflector, which are sequentially arranged along an optical axis of the system, wherein light rays from the display element sequentially pass through the lens, the spectroscope and the reflector, pass through the spectroscope again and then enter an eye box of the optical system; and an angle of field of view of the optical system is greater than or equal to 35° and less than or equal to 55°, a first ratio of the optical system is greater than or equal to 1 and less than or equal to 1.3, and the first ratio is a ratio of a square root of a product of the focal length of the lens and the focal length of a reflective surface of the reflector to the system focal length of the optical system.

Description

Optical systems and head-mounted display devices

[0001] This application claims priority to the invention application with an application date of September 12, 2023, application number "202311176226.2", and patent name "Optical system and head-mounted display device", all contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments of the present disclosure relate to the field of augmented reality technology, and in particular to an optical system and a head-mounted display device. Background Art

[0003] Augmented reality technology combines virtual and real-world scenes. By simultaneously projecting virtual images and real-world scenes into the user's view, it provides a visual experience that blends virtual and real life. Wearing augmented reality devices, such as head-mounted displays and AR glasses, is a common way for users to experience this fusion.

[0004] As demand increases, the overall structure of head-mounted display devices is expected to be more compact. However, it is difficult to balance the optical system volume, field of view, and eye box (the area where the human eye can move and see the entire displayed image) in design.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present disclosure provide an optical system and a head-mounted display device.

[0007] According to a first aspect of an embodiment of the present disclosure, an optical system is provided, comprising: a display element, a lens, a beam splitter, and a reflector arranged in sequence along an optical axis of the system; wherein light from the display element passes through the lens, the beam splitter, the reflector in sequence, and then passes through the beam splitter again before entering an eye box of the optical system;

[0008] The field of view angle of the optical system is greater than or equal to 35°, and the optical system satisfies the following relationship:

[0009] Among them, f L represents the focal length of the lens, f R represents the focal length of the reflecting surface of the reflector, f represents the system focal length of the optical system, and the first ratio s1 is greater than or equal to 1 and less than or equal to 1.3.

[0010] According to a second aspect of an embodiment of the present disclosure, a head-mounted display device is provided, which includes the above-mentioned optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present disclosure. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0012] FIG1 is a schematic diagram of the structure of an optical system provided by an embodiment of the present disclosure.

[0013] FIG2 is a schematic diagram of another optical system structure provided by an embodiment of the present disclosure.

[0014] FIG3 is a diagram of an imaging optical path of an optical system of the type shown in FIG1 .

[0015] FIG4 is a schematic diagram of an optical transfer function MTF curve of an optical system provided by an embodiment of the present disclosure.

[0016] FIG5 is a schematic structural diagram of a head-mounted display device according to an exemplary embodiment of the present disclosure.

[0017] Description of reference numerals:

[0018] 100: Optical system

[0019] 101: Display components

[0020] 102: Lens

[0021] 103: Spectroscope

[0022] 104: Reflector

[0023] 500: Head-mounted display device DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field should fall within the scope of protection of the embodiments of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other unless there is a conflict.

[0025] The specific implementation of the embodiment of the present disclosure is further explained below with reference to the accompanying drawings of the embodiment of the present disclosure.

[0026] FIG1 shows a schematic structural diagram of an optical system provided by some embodiments of the present disclosure, and FIG2 shows another schematic structural diagram of an optical system provided by some embodiments of the present disclosure.

[0027] Referring to Figures 1 and 2 , optical system 100 includes a display element 101, a lens 102, a beam splitter 103, and a reflector 104, arranged in sequence along the system's optical axis. Light emitted from display element 101 passes through lens 102, beam splitter 103, and reflector 104, and then again through beam splitter 103 before entering the eye box of optical system 100. This allows the human eye within the eye box to see the image displayed by display element 101. It should be understood that the system's optical axis refers to the optical axis of optical system 100.

[0028] The display element 101 is used to display images intended for the human eye. The display element 101 can be, but is not limited to, a relatively small display to minimize the overall size of the optical system 100. For example, the display element 101 can be an organic light-emitting diode (OLED) image source, a liquid crystal on silicon (LCOS) image source, a liquid crystal display (LCD) image source, a micro-electro-mechanical system (MEMS) image source, or a digital micromirror device (DMD) image source. The images displayed by the display element 101 can be, but are not limited to, various types, including 2D images, 3D images, static images, and dynamic images.

[0029] The lens 102 is used to provide diopter for the optical system 100 , and can magnify the image displayed by the display element 101 . In the case where the image displayed by the display element 101 is relatively small, the image displayed by the display element 101 can be magnified.

[0030] The beam splitter 103 is used to split the incident light. The beam splitter 103 has a first surface and a second surface, and either the first surface or the second surface can serve as the beam splitting surface of the beam splitter 103. The beam splitting surface is partially transmissive and partially reflective.

[0031] The reflector 104 is used to reflect the incident light so that the light is deflected and enters the eye box. The reflector 104 can be partially transmissive, partially reflective, or fully reflective.

[0032] It should be noted that for an entire optical system, the system optical axis can be the line connecting the optical centers of each optical component in the system, with each optical component arranged along the system optical axis. For a single optical component (e.g., the optical axis of a reflector), the optical axis of the optical component passes through the optical center of the optical component, and no deflection occurs between the incident and outgoing light. It is understood that due to manufacturing and assembly errors, the system optical axis and the optical axes of individual optical components may not be perfectly straight lines.

[0033] In some possible embodiments, referring to FIG1 , the display element 101, the lens 102, and the reflector 104 are located on the same side of the beam splitter 103. The normal direction of the display element 101 is consistent with or parallel to the optical axis of the lens 102. The lens 102 has a first surface close to the beam splitter 103 and a second surface close to the display element 101. The beam splitter 103 has a second surface close to the lens 102 and a first surface away from the lens 102. The second surface of the beam splitter 103 is a beam splitting surface. The beam splitting surface of the beam splitter 103 is at a certain inclination angle to the optical axis of the lens 102. The optical axis of the reflector 104 is at a certain inclination angle to the beam splitting surface of the beam splitter 103. The reflector 104 can be a semi-transparent and semi-reflective lens.

[0034] As shown in Figure 1, light emitted from display element 101 enters lens 102, passes through the second and first surfaces of lens 102, and is incident on the second surface of beam splitter 103. Some of the light is transmitted through the second and first surfaces of beam splitter 103 and then exits. Some of the light is reflected by the second surface (i.e., the beam splitting surface) of beam splitter 103 and then onto the reflective surface of reflector 104. The light reflected by the reflective surface of reflector 104 then passes through beam splitter 103 again before entering the eyebox. Natural light from the real world passes through reflector 104 and beam splitter 103 and then enters the eyebox, allowing the human eye in the eyebox to simultaneously see the clear image displayed by the magnified display element 101 and the real world.

[0035] In some possible embodiments, referring to FIG2 , the display element 101, the lens 102, and the reflector 104 can be disposed on both sides of the beam splitter 103. In other words, the display element 101 and the lens 102 can be disposed on one side of the beam splitter 103, and the reflector 104 can be disposed on the other side of the beam splitter 103. The normal direction of the display element 101 is consistent with or parallel to the optical axis of the lens 102. The lens 102 has a second surface close to the display element 101 and a first surface close to the beam splitter 103. The beam splitter 103 has a second surface close to the lens 102 and a first surface close to the reflector 104. The second surface of the beam splitter 103 is a transmission surface, and the first surface of the beam splitter 103 is a beam splitting surface. The beam splitting surface of the beam splitter 103 is inclined at a certain angle to the optical axis of the lens 102. The optical axis of the reflector 104 is inclined at a certain angle to the beam splitting surface of the beam splitter 103.

[0036] As shown in Figure 2, light emitted from display element 101 enters lens 102, passes through the second and first surfaces of lens 102, and is incident on beam splitter 103. After being transmitted by the second and first surfaces of beam splitter 103, it is incident on the reflective surface of reflector 104. It is then reflected by the reflective surface of reflector 104 to the first surface of beam splitter 103. Part of the light is reflected by the first surface (i.e., the beam splitting surface) of beam splitter 103 and finally enters the eye box. Natural light from the real world can pass through beam splitter 103 and enter the eye box, allowing the human eye in the eye box to simultaneously see the clear image displayed by the magnified display element 101 and the real world.

[0037] Figure 3 shows an imaging optical path diagram for optical system 100 of the type shown in Figure 1 . Light emitted from display element 101 enters lens 102, is refracted by the second and first surfaces of lens 102, and then is incident on the second surface of beam splitter 103. Part of the light is reflected by the second surface of beam splitter 103 (i.e., the beam splitting surface of beam splitter 103) and then onto the reflective surface of reflector 104. The light reflected by the reflective surface of reflector 104 then passes through beam splitter 103 and ultimately enters the eyebox, allowing the human eye in the eyebox to see the clear, magnified image displayed by display element 101.

[0038] The imaging principle of the optical system 100 shown in FIG2 is similar to that of the optical system described in FIG1 , and will not be described in detail here.

[0039] In some embodiments of the present disclosure, the first ratio of the optical system 100 is greater than or equal to 1 and less than or equal to 1.3. The first ratio refers to the ratio between the square root of the product of the focal length of the lens 102 and the focal length of the reflector 104 and the system focal length of the optical system 100. The optical system 100 has a field of view of greater than or equal to 35° and less than or equal to 55°. In other words, the optical system 100 satisfies the relationship shown in the following equation (1). As a result, the human eye can observe a clear image with a field of view of greater than or equal to 35° and less than or equal to 55° within a predetermined eye box.

[0040] Among them, f L represents the focal length of the lens 102, f R represents the focal length of the reflecting surface of the reflector 104 , f represents the system focal length of the optical system 100 , and the value range of the first ratio s1 is [1, 1.3], that is, the first ratio s1 can be greater than or equal to 1 and less than or equal to 1.3.

[0041] In this way, the optical system 100 can have a compact system volume while having a field of view angle of greater than or equal to 35° and less than or equal to 55°.

[0042] Optionally, the first ratio s1 may also be set to be greater than or equal to 1.05 and less than or equal to 1.2. In this way, the optical system 100 can have a field of view greater than or equal to 35° and less than or equal to 55° while further reducing the system volume.

[0043] In some embodiments of the present disclosure, the height of the optical system 100 is less than or equal to 27 mm, and the thickness is less than or equal to 20 mm. Thus, the optical system 100 in the embodiments of the present disclosure is compact, meeting the wearing comfort requirements of head-mounted display devices. Optionally, the height of the optical system 100 can be less than or equal to 24 mm, and the thickness can be less than or equal to 16 mm. The volume of the optical system 100 can be further reduced, thereby better meeting the wearing comfort requirements of head-mounted display devices.

[0044] In some embodiments of the present disclosure, the second ratio of the optical system 100 is greater than or equal to 0.75 and less than or equal to 0.985. The second ratio refers to the ratio of the sum of the distance between the reflector 104 and the beam splitter 103 along the system optical axis and the distance between the lens 102 and the beam splitter 103 along the system optical axis to the system focal length of the optical system 100. In other words, the optical system 100 can satisfy the relationship shown in the following equation (2):

[0045] (L1+L2) / f=s2 (2)

[0046] Wherein, L1 represents the distance between the reflector 104 and the beam splitter 103 along the system optical axis, L2 represents the distance between the lens 102 and the beam splitter 103 along the system optical axis, and the second ratio s2 is greater than or equal to 0.75 and less than or equal to 0.985.

[0047] It can be understood that the spacing between the reflector 104 and the beam splitter 103 along the system optical axis may refer to the distance between the optical center of the reflector 104 and the optical center of the beam splitter 103 on the system optical axis, and the spacing between the lens 102 and the beam splitter 103 in the optical axis direction may refer to the distance between the optical center of the lens 102 and the optical center of the beam splitter 103 in the system optical axis direction.

[0048] Optionally, the second ratio s2 may be greater than or equal to 0.825 and less than or equal to 0.925.

[0049] Since a large field of view optical system 100 generally corresponds to a small system focal length, a small system focal length requires that the reflector 104 and lens 102 in the optical system 100 have a small distance. For the optical system of the type shown in FIG1 , achieving a large field of view means that the spatial distance between the reflector 104 and the lens 102 is small. When the spatial distance is too close, interference between the optical elements is likely to occur (i.e., when the distance is too close, the edge of the reflector 104 and the edge of the lens 102 interfere with each other). For the optical system shown in FIG2 , achieving a large field of view means that the spatial distance between the reflector 104 and the lens 102 is small. In this case, the spatial distance between the reflector 104 and the beam splitter 103, and the spatial distance between the beam splitter 103 and the lens 102 should also be small. When the spatial distances between the reflector 104 and the beam splitter 103, and between the beam splitter 103 and the lens 102 are too close, interference between the optical elements is likely to occur. Formula (2) can be used to optimize the distance between the reflector 104 and the beam splitter 103, as well as the distance between the lens 102 and the beam splitter 103, so that the spatial distance between the reflector 104 and the lens 102 is more reasonable when the focal length of the optical system 100 is f, thereby avoiding interference between optical elements.

[0050] In some embodiments of the present disclosure, the lens 102 may be an aspheric lens that satisfies the equation shown in the following formula (3). The aspheric lens can correct spherical aberration and improve the imaging quality of the optical system 100 in a set eye box.

[0051] Among them, r represents the distance vector height of the aspheric surface from the vertex of the aspheric surface at a height of h along the optical axis, c represents the curvature of the aspheric surface, that is, c = 1 / R (R is the curvature radius of the aspheric surface), k represents the cone coefficient, and Aii represents the coefficient of the i-th order of the aspheric surface.

[0052] In some embodiments of the present disclosure, the third ratio of the optical system 100 can be greater than or equal to 0.2 and less than 1. The third ratio refers to the ratio between the difference between the sag height of the first surface of the lens 102 (i.e., the surface close to the beam splitter 103) at the maximum effective aperture and the sag height of the second surface of the lens 102 (i.e., the surface close to the display element 101) at the maximum effective aperture, and the sum of the sag height of the first surface of the lens 102 at the maximum effective aperture and the sag height of the second surface of the lens 102 at the maximum effective aperture. In other words, the optical system 100 can satisfy the relationship shown in the following equation (4):

[0053] (SGL1-SGL2) / (SGL1+SGL2)=s3 (4)

[0054] SGL1 represents the sag of the surface of the lens 102 close to the beam splitter 103 at the maximum effective aperture, SGL2 represents the sag of the surface of the lens 102 close to the display element 101 at the maximum effective aperture, and the third ratio s3 is greater than or equal to 0.2 and less than 1.

[0055] Optionally, the third ratio s3 of the optical system 100 may be greater than or equal to 0.4 and less than or equal to 0.8.

[0056] It should be noted that the lens 102 generally includes an effective aperture portion and an edge portion used for installation and fixing, wherein the effective aperture portion participates in imaging.

[0057] Formula (4) can take into account both the central field of view and the peripheral field of view of the optical system 100, better balance the resolution and field curvature of the central field of view and the peripheral field of view of the optical system 100, and effectively reduce the difficulty of lens processing and manufacturing.

[0058] In some embodiments of the present disclosure, the fourth ratio of the optical system 100 may be greater than or equal to 5 and less than or equal to 7. The fourth ratio refers to the ratio of the product of the center thickness of the lens 102 and the focal length of the lens 102 to the system focal length of the optical system 100. In other words, the optical system 100 may also satisfy the relationship shown in the following formula (5):

[0059] T×f L / f=s4 (5)

[0060] Wherein, T represents the center thickness of the lens 102 , and the fourth ratio s4 is greater than or equal to 5 and less than or equal to 7.

[0061] Optionally, the fourth ratio may be greater than or equal to 5.5 and less than or equal to 6.5.

[0062] Formula (5) can effectively reduce the difficulty of processing and manufacturing the lens 102, and at the same time can adjust the volume of the lens, thereby reducing the weight and size of the entire system.

[0063] In addition, by reasonably optimizing the center thickness of the lens 102 and the focal length of the lens 102, the size of the lens 102 of the optical system 100 can be made more reasonable when the system focal length is f, which is beneficial to improving the imaging quality of the optical system 100 within the set eye box and the specified field of view, thereby facilitating a better balance between the volume, field of view and eye box range of the optical system 100.

[0064] In some embodiments of the present disclosure, the fifth ratio of the optical system 100 may be greater than or equal to 0.02 and less than or equal to 0.2. The fifth ratio refers to the ratio of the distance between the second surface of the lens 102 (i.e., the surface close to the display element 101) and the display surface of the display element 101 to the system focal length of the optical system 100. In other words, the optical system 100 may also satisfy the relationship shown in the following equation (6):

[0065] BFL / f=s5 (6)

[0066] BFL represents the distance between the second surface of the lens 102 and the display surface of the display element 101 along the system optical axis, and the fifth ratio s5 is greater than or equal to 0.02 and less than or equal to 0.2.

[0067] It should be noted that, in the embodiment of the present disclosure, the distance BFL between the surface of the lens 102 close to the display element 101 and the display element 101 is calculated based on the equivalent distance in air.

[0068] By rationally designing the system focal length of the optical system 100 and the distance between the second surface of the lens and the display element 101 according to formula (6), the CRA (Chief Ray Angle) of the optical system 100 can be better matched with the CRA of the display element.

[0069] In some embodiments of the present disclosure, the refractive index of the lens 102 may be greater than or equal to 1.4 and less than or equal to 1.7. Alternatively, the refractive index of the lens 102 may be greater than or equal to 1.4 and less than or equal to 1.6.

[0070] In some embodiments of the present disclosure, the Abbe number of the lens 102 may be greater than or equal to 18 and less than or equal to 65. Optionally, the Abbe number of the lens 102 may be greater than or equal to 30 and less than or equal to 60.

[0071] Selecting a lens 102 with a reasonable refractive index and Abbe number can improve the imaging quality of the optical system 100 within a set eye box and a specified field of view, while balancing the volume, field of view, and eye box range of the optical system 100.

[0072] 1 and 2 , the beam splitter 103 can be tilted relative to the lens 102. In some possible implementations, the angle between the normal of the display element 101 and the beam splitter surface of the beam splitter 103 is β, and the angle between the beam splitter surface of the beam splitter 103 and the optical axis of the reflector 104 is α. The beam splitter 103 can be tilted relative to the lens 102 such that: β is greater than or equal to 40° and less than or equal to 50°, and α is greater than or equal to β-10° and less than or equal to β+10°. This ensures that the optical system 100 can achieve the designed field of view and eye box, and that the imaging quality of the optical system 100 is guaranteed.

[0073] In some embodiments of the present disclosure, the sixth ratio of the optical system 100 may be greater than or equal to 0.2 and less than or equal to 0.385. The sixth ratio refers to the ratio of the distance between the reflector 104 and the beam splitter 103 along the system optical axis to the focal length of the reflector 104. In other words, the optical system 100 satisfies the relationship shown in the following equation (7):

[0074] L1 / f R =s6 (7)

[0075] Wherein, L1 represents the spacing between the reflector 104 and the beam splitter 103 along the system optical axis, and the sixth ratio s6 is greater than or equal to 0.2 and less than or equal to 0.385. The spacing between the reflector 104 and the beam splitter 103 can be controlled by equation (7), making the spacing between the reflector 104 and the beam splitter 103 more reasonable, which is beneficial for improving the imaging quality of the optical system 100 at a set eye box and a specified field of view angle, and is also beneficial for adjusting the size of the eye box.

[0076] Optionally, the sixth ratio s6 may be greater than or equal to 0.3 and less than or equal to 0.35.

[0077] In some embodiments of the present disclosure, the size of the eye box at a preset eye relief (ER) satisfies: the length of the eye box is greater than or equal to 8 mm and less than or equal to 25 mm, and the height of the eye box is greater than or equal to 3 mm and less than or equal to 10 mm, that is, the eye box can be set to a size that satisfies the relationship shown in the following formula (8).

[0078] 8mm*3mm<EB<25mm*10mm (8)

[0079] Wherein, EB represents eye box, mm represents millimeters, * represents multiplication, length refers to the dimension along the left and right eye direction, and height refers to the dimension perpendicular to the left and right eye direction.

[0080] In some embodiments of the present disclosure, the diameter of the eye box at a preset eye relief may be greater than or equal to 6 mm.

[0081] In some embodiments of the present disclosure, the field of view of the optical system 100 can be greater than or equal to 40° and less than or equal to 55°. Thus, the optical system 100 of the present disclosure can produce high-quality images of the image displayed by the display element 101 within a larger field of view, allowing the human eye located within a predetermined eye box to see a clear image of the image displayed by the display element 101.

[0082] Table 1 shows a reference table of optical parameters of various optical elements in the optical system 100 according to some embodiments of the present disclosure, and Table 2 shows an example of aspheric coefficients of the lens 102 in the optical system 100 shown in Table 1. The field of view of the optical system 100 is 43°, the system focal length f is 16.75 mm, the first ratio is 1.16, the second ratio is 0.896, the third ratio is 0.44, the fourth ratio is 5.97, the fifth ratio is 0.09, and the sixth ratio is 0.36.

[0083] Table 1

[0084] Table 2

[0085] Figure 4 shows a schematic diagram of the modulation transfer function (MTF) curve of optical system 100. MTF is a method for describing the performance of an optical system and can be used to assess its ability to restore contrast. In Figure 4, the horizontal axis represents spatial frequency, the vertical axis represents contrast, the solid line represents the meridional direction, and the dashed line represents the sagittal direction. As shown in Figure 4, optical system 100 has good resolution in different field of view directions, resulting in high overall imaging quality that meets the human eye's requirements for resolution clarity.

[0086] 5 , there is shown a schematic structural diagram of a head mounted display device 500 according to an embodiment of the present disclosure. As shown in FIG5 , the head mounted display device 500 of this embodiment includes: a frame and the aforementioned optical system 100.

[0087] The frame is used to fix the optical system 100. The frame can be, for example but not limited to, a headband or a glasses frame.

[0088] In some optional embodiments, the head-mounted display device 500 includes but is not limited to: VR smart glasses, AR smart glasses, XR smart glasses, MR smart glasses, etc.

[0089] In some optional embodiments, the head-mounted display device 500 includes an integrated head-mounted display device or a split head-mounted display device. The split head-mounted display device may include a head-mounted display device and a terminal device, wherein the head-mounted display device is, for example, AR glasses, VR glasses, MR glasses, etc. The terminal device is, for example, a mobile phone, tablet, computer, etc.

[0090] It should be pointed out that, according to the needs of implementation, the various components / steps described in the embodiments of the present disclosure can be split into more components / steps, or two or more components / steps or partial operations of components / steps can be combined into new components / steps to achieve the purpose of the embodiments of the present disclosure.

[0091] Those skilled in the art will appreciate that the units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments of the present disclosure.

[0092] The above implementation methods are only used to illustrate the embodiments of the present disclosure, and are not intended to limit the embodiments of the present disclosure. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the embodiments of the present disclosure. Therefore, all equivalent technical solutions also fall within the scope of the embodiments of the present disclosure, and the scope of patent protection of the embodiments of the present disclosure should be defined by the claims.

Claims

1. An optical system, comprising: A display element, a lens, a beam splitter, and a reflector are sequentially arranged along the optical axis of the system; wherein the light from the display element sequentially passes through the lens, the beam splitter, the reflector, and then passes through the beam splitter again before entering the eye box of the optical system; The field of view angle of the optical system is greater than or equal to 35° and less than or equal to 55°; The optical system satisfies the following relationship: Among them, f L represents the focal length of the lens, f R represents the focal length of the reflecting surface of the reflector, f represents the system focal length of the optical system, and the first ratio s1 is greater than or equal to 1 and less than or equal to 1.

3.

2. The optical system according to claim 1, wherein: The first ratio s1 is greater than or equal to 1.05 and less than or equal to 1.

2.

3. The optical system according to claim 1 or 2, wherein: The optical system meets any of the following dimensions: The height of the optical system is less than or equal to 27 mm, and the thickness is less than or equal to 20 mm. The height of the optical system is less than or equal to 24 mm, and the thickness is less than or equal to 16 mm.

4. An optical system according to any preceding claim, wherein: The optical system also satisfies the following relationship: (L1+L2) / f=s2 Wherein, L1 represents the distance between the reflector and the beam splitter along the optical axis of the system, L2 represents the distance between the lens and the beam splitter along the optical axis of the system, and the second ratio s2 is greater than or equal to 0.75 and less than or equal to 0.

985.

5. The optical system according to claim 4, wherein: The second ratio s2 is greater than or equal to 0.825 and less than or equal to 0.

925.

6. An optical system according to any preceding claim, wherein: The lenses satisfy the following relationship: (SGL1-SGL2) / (SGL1+SGL2)=s3 Wherein, SGL1 represents the sag of the surface of the lens close to the beam splitter at the maximum effective aperture, SGL2 represents the sag of the surface of the lens close to the display element at the maximum effective aperture, and the third ratio s3 is greater than or equal to 0.2 and less than 1.

7. The optical system according to claim 6, wherein: The third ratio s3 is greater than or equal to 0.4 and less than or equal to 0.

8.

8. An optical system according to any preceding claim, wherein: The lens satisfies the following relationship: T×f L / f=s4 Wherein, T represents the central thickness of the lens, and the fourth ratio s4 is greater than or equal to 5 and less than or equal to 7.

9. The optical system according to claim 8, wherein: The fourth ratio s4 is greater than or equal to 5.5 and less than or equal to 6.

5.

10. An optical system according to any preceding claim, wherein: The lens satisfies the following relationship: BFL / f=s5 Wherein, BFL represents the distance between the surface of the lens close to the display element and the display surface of the display element along the system optical axis, and the BFL is calculated as an equivalent distance in the air, and the fifth ratio s5 is greater than or equal to 0.02 and less than or equal to 0.

2.

11. An optical system according to any preceding claim, wherein: The reflector satisfies the following relationship: L1 / f R =s6 Wherein, L1 represents the distance between the reflector and the beam splitter along the optical axis of the system, and the sixth ratio s6 is greater than or equal to 0.2 and less than or equal to 0.

385.

12. The optical system according to claim 11, wherein: The sixth ratio s6 is greater than or equal to 0.3 and less than or equal to 0.

35.

13. An optical system according to any preceding claim, wherein: The field of view angle of the optical system is greater than or equal to 40° and less than or equal to 55°.

14. An optical system according to any preceding claim, wherein: The eye box meets any of the following dimensions at the preset eye relief: The length of the eye box is greater than or equal to 8 mm and less than or equal to 25 mm, and the height of the eye box is greater than or equal to 3 mm and less than or equal to 10 mm; The diameter of the eye box is greater than 6mm.

15. A head mounted display device, comprising: A frame for fixing the optical system; Wherein, the optical system is the optical system as claimed in any one of claims 1 to 14.

Images