Optical systems and VR display devices

Abstract

An optical system (100) has an optical axis (A). The optical system (100) includes a positive power lens (1), a negative power lens (2), and a display (3) arranged sequentially along the optical axis (A). The positive power lens (1) includes a first convex surface (11) away from the display (3) and a second convex surface (12) close to the display (3). Both the first convex surface (11) and the second convex surface (12) are convex outward relative to the optical center (C1) of the positive power lens (1). The negative power lens (2) includes a third convex surface (21) away from the display (3) and a fourth concave surface (22) close to the display (3). The third convex surface (21) is convex outward relative to the optical center (C2) of the negative power lens (2), and the fourth concave surface (22) is concave inward relative to the optical center (C2) of the negative power lens (2). Among them, the refractive index of the positive power lens (1) and the refractive index of the negative power lens (2) are such that the refractive index of one is greater than the refractive index of the other, the larger refractive index is the first refractive index, the smaller refractive index is the second refractive index, the first refractive index is greater than 1.7, the second refractive index is greater than 1.5, and the ratio of the first refractive index to the second refractive index is less than or equal to 2.

Description

Technical Field

[0001] This disclosure relates to the field of display technology, and more particularly to an optical system and a VR display device. Background Technology

[0002] Virtual Reality (VR) technology is a high-tech field involving numerous disciplines. It integrates computer simulation, 3D design, image processing, pattern recognition, microelectronics, and parallel processing technologies to create a realistic virtual environment using virtual reality hardware and computer systems. Users experience the same sensations in the virtual space as in the real world, such as visual, auditory, tactile, olfactory, collision, movement, and dynamic interactive sensations.

[0003] Currently, VR display devices are developing towards larger field of view and thinner and lighter designs to provide viewers with a better sense of immersion and enhance the user experience. Summary of the Invention

[0004] On one hand, an optical system is provided, having an optical axis. The optical system includes a positive power lens, a negative power lens, and a display, arranged sequentially along the optical axis. The positive power lens includes a first convex surface away from the display and a second convex surface near the display, both the first and second convex surfaces being outwardly convex relative to the optical center of the positive power lens. The negative power lens includes a third convex surface away from the display and a fourth concave surface near the display, the third convex surface being outwardly convex relative to the optical center of the negative power lens, and the fourth concave surface being inwardly concave relative to the optical center of the negative power lens. Wherein, the refractive index of the positive power lens and the refractive index of the negative power lens are both greater than the refractive index of the other, the larger refractive index being a first refractive index and the smaller refractive index being a second refractive index, the first refractive index being greater than 1.7, the second refractive index being greater than 1.5, and the ratio of the first refractive index to the second refractive index being less than or equal to 2.

[0005] In some embodiments, the radius of curvature of the fourth concave surface of the negative power lens is smaller than the radius of curvature of the third convex surface.

[0006] In some embodiments, the radius of curvature of the fourth concave surface is greater than 0 and less than or equal to 50 mm; the radius of curvature of the third convex surface is greater than 0 and less than or equal to 100 mm.

[0007] In some embodiments, the negative power lens includes a central portion near the optical axis and an edge portion surrounding the central portion. Along the optical axis, the thickness of the central portion is less than the thickness of the edge portion.

[0008] In some embodiments, the ratio of the first refractive index to the second refractive index is less than or equal to 1.1.

[0009] In some embodiments, the optical power range of the positive power lens is 0.05 mm. -1 ~0.15mm -1 The refractive index of the positive power lens is greater than that of the negative power lens.

[0010] In some embodiments, the optical power range of the negative power lens is -0.1 mm. -1 ~-0.02mm -1 .

[0011] In some embodiments, the first refractive index is N1, and the second refractive index is N2. Along the optical axis, the distance between the second convex surface of the positive power lens and the third convex surface of the negative power lens is D. Wherein,

[0012] In some embodiments, along the optical axis, the distance between the second convex surface of the positive power lens and the third convex surface of the negative power lens ranges from 0.5 mm to 0.55 mm.

[0013] In some embodiments, along the optical axis, the distance between the vertex of the first convex surface of the positive power lens and the surface of the display away from the negative power lens is less than or equal to 35 mm.

[0014] In some embodiments, the refractive index of the positive power lens is N. a The dispersion coefficient is V a The refractive index of the negative power lens is N. b The dispersion coefficient is V b .in, and One of them is greater than the other, and the ratio of the larger one to the smaller one is less than or equal to 2.5.

[0015] In some embodiments, the first convex surface, the second convex surface, the third convex surface, and the fourth concave surface are all aspherical surfaces.

[0016] In some embodiments, the first convex surface, the second convex surface, the third convex surface, and the fourth concave surface are all even-order aspherical surfaces. The surface equations of the first convex surface, the second convex surface, the third convex surface, and the fourth concave surface are all... Where Z is the perpendicular distance between a point on the lens surface and the first reference plane, and the first reference plane is tangent to the vertex of the lens surface; c is the curvature at the vertex of the lens surface; k is the quadratic surface coefficient of the lens surface; r is the perpendicular distance between a point on the lens surface and the optical axis; A2i The coefficient of the multiplication term is i; i ≥ 1 and is an integer.

[0017] In some embodiments, the material of the positive power lens includes glass, and the material of the negative power lens includes plastic.

[0018] In some embodiments, the mass of the positive power lens is greater than the mass of the negative power lens.

[0019] In some embodiments, the optical system further includes a fixed member and a movable member, wherein the positive power lens and the negative power lens are disposed on the fixed member. The movable member is slidably connected to the fixed member, and the display is disposed on the movable member, which is configured to drive the display to move along the optical axis.

[0020] On the other hand, a VR display device is provided. The VR display device includes an optical system as described in any of the above embodiments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this disclosure.

[0022] Figure 1 This is a structural diagram of an optical system according to some embodiments;

[0023] Figure 2 for Figure 1 A magnified view of the optical system at point M;

[0024] Figure 3 An optical path diagram of an optical system according to some embodiments;

[0025] Figure 4 This is a structural diagram of a positive focal length lens for an optical system according to some embodiments;

[0026] Figure 5 for Figure 4 A cross-sectional view of the positive power lens along section line AA';

[0027] Figure 6 This is a structural diagram of a negative power lens for an optical system according to some embodiments;

[0028] Figure 7 for Figure 6A cross-sectional view of the negative power lens along section line BB';

[0029] Figure 8 A dot diagram of an optical system according to some embodiments;

[0030] Figure 9 Field curvature diagrams of optical systems according to some embodiments;

[0031] Figure 10 A distortion diagram of an optical system according to some embodiments;

[0032] Figure 11 This is another structural diagram of an optical system according to some embodiments;

[0033] Figure 12 This is yet another structural diagram of an optical system according to some embodiments;

[0034] Figure 13 This is a structural diagram of a VR display device according to some embodiments. Detailed Implementation

[0035] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.

[0036] Unless the context otherwise requires, throughout the specification and claims, the term "comprise" and its other forms, such as the third-person singular "comprises" and the present participle "comprising," are interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiments," "example," "specific example," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0037] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0038] In describing some embodiments, the term "connection" and its derivative expressions may be used. For example, the term "connection" may be used in describing some embodiments to indicate that two or more components are in direct physical or electrical contact with each other.

[0039] The use of “configured as” in this article implies an open and inclusive language that does not exclude the applicability to or configuration of devices to perform additional tasks or steps.

[0040] In addition, the use of “based on” implies openness and inclusivity, because processes, steps, calculations or other actions “based on” one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0041] As used herein, “vertical” includes the described situation and situations that are similar to the described situation, within an acceptable range of deviation, which is determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, “vertical” includes absolute verticality and approximate verticality, where an acceptable range of deviation for approximate verticality could, for example, be within 5°.

[0042] This document describes exemplary embodiments with reference to cross-sectional views and / or plan views, which are idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0043] In related technologies, VR display devices include a folded pancake structure. This structural design can reduce the thickness of the display device, but it leads to lower light emission efficiency (less than 25%), and problems such as "ghosting" and a small field of view, resulting in a poor visual experience for the viewer.

[0044] To solve the above problems, such as Figure 1 As shown, some embodiments of this disclosure provide an optical system 100, which has an optical axis A, and the optical axis A is the axis of symmetry of the optical system 100.

[0045] like Figure 1 As shown, the optical system 100 includes a positive power lens 1, a negative power lens 2 and a display 3 arranged sequentially along the optical axis A. The optical center C1 of the positive power lens 1, the optical center C2 of the negative power lens 2 and the center C3 of the display 3 are all located on the optical axis A.

[0046] It should be noted that the optical power of "positive optical power lens 1" is greater than 0, and light rays converge after being refracted by positive optical power lens 1. The optical power of "negative optical power lens 2" is less than 0, and light rays diverge after being refracted by negative optical power lens 2.

[0047] like Figure 1 As shown, the positive focal length lens 1 includes a first convex surface 11 away from the display 3 and a second convex surface 12 close to the display 3. Both the first convex surface 11 and the second convex surface 12 are convex outward relative to the optical center C1 of the positive focal length lens 1.

[0048] like Figure 1 As shown, the negative power lens 2 includes a third convex surface 21 away from the display 3 and a fourth concave surface 22 close to the display 3. The third convex surface 21 is convex outward relative to the optical center C2 of the negative power lens 2, and the fourth concave surface 22 is concave inward relative to the optical center C2 of the negative power lens 2.

[0049] Among the refractive indices of positive power lens 1 and negative power lens 2, one of them has a greater refractive index than the other. For ease of description, the larger refractive index is called the "first refractive index" and the smaller refractive index is called the "second refractive index". The first refractive index is greater than 1.7 and the second refractive index is greater than 1.5. The ratio of the first refractive index to the second refractive index is less than or equal to 2.

[0050] For example, the focal length range of the optical system 100 is 20mm to 35mm, such as 20mm, 25mm, 28mm, 30mm or 35mm.

[0051] In the above embodiments of this disclosure, combined with Figure 1 and Figure 3The optical system 100 adopts a structural design that combines a positive power lens 1 and a negative power lens 2, which can reduce aberrations such as spherical aberration and field curvature in the viewing image (the image of the optical system 100 at the human eye 4), reduce stray light in the light emitted by the optical system 100, improve the "ghosting" and glare problems of the image, improve the image quality, thereby enhancing the viewer's immersion. In addition, the optical system 100 has a high light emission efficiency.

[0052] In this design, the fourth concave surface 22 of the negative power lens 2 is concave relative to the optical center C2 of the negative power lens 2, so as to collect light rays with larger angles emitted by the display 3. Furthermore, the refractive indices of the positive power lens 1 and the negative power lens 2 are configured such that one refractive index is greater than the other, with the larger refractive index being the first refractive index and the smaller refractive index being the second refractive index. The first refractive index is greater than 1.7, the second refractive index is greater than 1.5, and the ratio of the first refractive index to the second refractive index is less than or equal to 2. With this design, the positive power lens 1 and the negative power lens 2 can refract light rays with larger angles into the human eye 4 within a shorter distance (the focal length of the optical system 100), thereby increasing the field of view of the viewing image of the optical system 100 (e.g., the field of view is greater than or equal to 90°), and allowing the optical system 100 to be made thinner and lighter.

[0053] The following explanations, in conjunction with the accompanying drawings, describe the positive power lens 1, the negative power lens 2, and the display 3 in the optical system 100, as well as the relationships between them.

[0054] In some embodiments, such as Figure 4 and Figure 5 As shown, the optical power of positive power lens 1 is greater than 0, and the optical power range of positive power lens 1 is 0.05mm. -1 ~0.15mm -1 For example, the optical power of positive power lens 1 is 0.05mm. -1 0.07mm -1 0.1mm -1 0.12mm -1 or 0.15mm -1 .

[0055] In some embodiments, such as Figure 4 and Figure 5 As shown, the first convex surface 11 of the positive power lens 1 can be spherical or aspherical, and the second convex surface 12 can be spherical or aspherical.

[0056] It should be noted that "spherical" means that the radius of curvature of the lens surface remains constant at all points. Taking the first convex surface 11 as an example, "aspherical" means that the radius of curvature of the lens surface gradually increases from the vertex P1 to the edge (the lens surface gradually becomes flat).

[0057] For example, the first convex surface 11 and the second convex surface 12 of the positive focal power lens 1 are both aspherical, which can reduce various aberrations such as spherical aberration, coma, and field curvature of the viewed image of the optical system 100.

[0058] In some embodiments, such as Figure 4 and Figure 5 As shown, the radius of curvature of the first convex surface 11 of the positive power lens 1 is greater than 0 and less than or equal to 100 mm. For example, the radius of curvature of the first convex surface 11 is 20 mm, 40 mm, 60 mm, 80 mm, or 100 mm. The radius of curvature of the second convex surface 12 is greater than 0 and less than or equal to 50 mm. For example, the radius of curvature of the second convex surface 12 is 10 mm, 20 mm, 30 mm, 40 mm, or 50 mm.

[0059] In some embodiments, such as Figure 4 and Figure 5 As shown, the positive power lens 1 includes a central portion a1 near the optical axis A and an edge portion b1 surrounding the central portion a1. Along the optical axis A, the thickness of the central portion a1 is greater than the thickness of the edge portion b1, that is, the central portion a1 of the positive power lens 1 is thicker and the edge portion b1 is thinner.

[0060] In some embodiments, such as Figure 4 and Figure 5 As shown, the material of the positive focal length lens 1 may include glass or plastic.

[0061] In some embodiments, such as Figure 6 and Figure 7 As shown, the optical power of negative power lens 2 is less than 0, and the optical power range of negative power lens 2 is -0.1mm. -1 ~-0.02mm -1 For example, the optical power of negative power lens 2 is -0.1mm. -1 -0.08mm -1 -0.06mm -1 -0.04mm -1 or -0.02mm -1 .

[0062] In some embodiments, such as Figure 6 and Figure 7 As shown, the third convex surface 21 of the negative power lens 2 can be spherical or aspherical, and the fourth concave surface 22 can be spherical or aspherical.

[0063] For example, the third convex surface 21 and the fourth concave surface 22 of the negative power lens 2 are both aspherical, which can reduce various aberrations such as spherical aberration, coma, and field curvature of the viewing image of the optical system 100.

[0064] In some embodiments, such as Figure 6 and Figure 7 As shown, the radius of curvature of the fourth concave surface 22 of the negative power lens 2 is smaller than the radius of curvature of the third convex surface 21.

[0065] It is understandable that the fourth concave surface 22 of the negative power lens 2 is concave relative to the optical center C2 of the negative power lens 2, and the radius of curvature of the fourth concave surface 22 is set to be smaller than that of the third convex surface 21. That is, the fourth concave surface 22 is more curved than the third convex surface 21, which is more conducive to the fourth concave surface 22 collecting light rays with a larger angle emitted by the display 3, thereby helping to increase the field of view of the viewing screen of the optical system 100.

[0066] For example, such as Figure 6 and Figure 7 As shown, the radius of curvature of the third convex surface 21 of the negative power lens 2 is greater than 0 and less than or equal to 100 mm. For example, the radius of curvature of the third convex surface 21 is 20 mm, 40 mm, 60 mm, 80 mm, or 100 mm. The radius of curvature of the fourth concave surface 22 is greater than 0 and less than or equal to 50 mm. For example, the radius of curvature of the fourth concave surface 22 is 10 mm, 20 mm, 30 mm, 40 mm, or 50 mm.

[0067] In some embodiments, such as Figure 6 and Figure 7 As shown, the negative power lens 2 includes a central portion a2 near the optical axis A and an edge portion b2 surrounding the central portion a2. Along the optical axis A, the thickness of the central portion a2 is less than the thickness of the edge portion b2, making the central portion a2 of the negative power lens 2 thinner and the edge portion b2 thicker.

[0068] In related technologies, both sides of a negative power lens are concave relative to the optical center, meaning both sides of a negative power lens are concave. This makes the middle part of the negative power lens very thin, and the thickness difference between the edge part and the middle part is large, resulting in low structural strength and easy breakage of the negative power lens.

[0069] Some embodiments of this disclosure, such as Figure 6 and Figure 7As shown, the third convex surface 21 of the negative power lens 2 protrudes outward relative to the optical center C2 of the negative power lens 2, which can increase the thickness of the middle part a2 of the negative power lens 2, improve the structural strength of the middle part a2 of the negative power lens 2, and avoid the problem that the middle part a2 of the negative power lens 2 is too thin and easily broken.

[0070] In some embodiments, such as Figure 6 and Figure 7 As shown, the material of the negative power lens 2 may include glass or plastic.

[0071] In some embodiments, such as Figure 1 and Figure 3 As shown, the refractive index of positive power lens 1 is greater than that of negative power lens 2; specifically, the refractive index of positive power lens 1 is greater than 1.7, and the refractive index of negative power lens 2 is greater than 1.5. Furthermore, the optical power range of positive power lens 1 is 0.05 mm. -1 ~0.15mm -1 The positive power lens 1 has a relatively small optical power, which allows it to refract light rays at larger angles into the human eye 4. Based on this, the positive power lens 1, when used in conjunction with the negative power lens 2, can increase the field of view of the image viewed by the optical system 100.

[0072] In some embodiments, such as Figure 1 and Figure 2 As shown, among the refractive indices of the positive power lens 1 and the negative power lens 2, the larger first refractive index is designated as N1, and the smaller second refractive index is designated as N2. Along the optical axis A, the distance between the second convex surface 12 of the positive power lens 1 and the third convex surface 21 of the negative power lens 2 is designated as D.

[0073] The relationship between the first refractive index N1, the second refractive index N2, and the distance D satisfies the following formula (1):

[0074]

[0075] It can be seen that, based on the design values ​​of the refractive index of the positive focal power lens 1 and the refractive index of the negative focal power lens 2, the reasonable range of the distance D can be determined. When the distance D is within the reasonable range, the length of the optical system 100 is guaranteed not to be too long, and the reliability of the assembly between the positive focal power lens 1 and the negative focal power lens 2 is guaranteed.

[0076] It should be noted that the reference Figure 1 "The length of the optical system 100" refers to the distance along the optical axis A from the vertex P1 of the first convex surface 11 of the positive power lens 1 to the surface 31 of the display 3 away from the negative power lens 2.

[0077] For example, along the optical axis A, the distance D between the second convex surface 12 of the positive power lens 1 and the third convex surface 21 of the negative power lens 2 ranges from 0.5 mm to 0.55 mm. For example, the distance D can be 0.51 mm, 0.52 mm, 0.53 mm, 0.54 mm or 0.55 mm.

[0078] Understandably, if the distance D is less than 0.5 mm, it indicates that the distance between the second convex surface 12 and the third convex surface 21 is too small, meaning the spacing between the positive power lens 1 and the negative power lens 2 is too small. This may lead to difficulties in assembling the positive power lens 1 and the negative power lens 2. If the distance D is greater than 0.55 mm, it indicates that the distance between the second convex surface 12 and the third convex surface 21 is too large, meaning the spacing between the positive power lens 1 and the negative power lens 2 is too large. This may lead to an excessively long optical system 100, which is detrimental to the thinning and lightening of the optical system 100.

[0079] In some embodiments, such as Figure 1 As shown, along the optical axis A, the distance between the vertex P1 of the first convex surface 11 of the positive power lens 1 and the surface 31 of the display 3 away from the negative power lens 2 is less than or equal to 35 mm, that is, the length of the optical system 100 is less than or equal to 35 mm. For example, the length of the optical system 100 is 31 mm, 32 mm, 33 mm, 34 mm or 35 mm.

[0080] In some embodiments, such as Figure 1 As shown, the refractive index of the positive focal power lens 1 is set to N. a The dispersion coefficient is set to V. a The refractive index of the negative power lens 2 is set to N. b The dispersion coefficient is set to V. b .in, and One of them is greater than the other, and the ratio of the larger one to the smaller one is less than or equal to 2.5. For example, and A ratio of 2.1, 2.2, 2.3, 2.4 or 2.5 between the larger and smaller components can reduce field curvature and chromatic aberration in the viewed image of the optical system 100.

[0081] In some embodiments, such as Figure 1 and Figure 3As shown, the mass of the positive power lens 1 is greater than the mass of the negative power lens 2. It should be noted that the "mass" of the lens refers to the product of the lens's material density and its volume. It is understood that the optical system 100 of this disclosure can be applied to VR display devices, which viewers can wear for viewing. Because the mass of the positive power lens 1 is greater than that of the negative power lens 2, and the positive power lens 1 is closer to the viewer's eye 4 than the negative power lens 2, the center of gravity of the VR display device is closer to the viewer, improving the viewer's wearing comfort.

[0082] For example, the material of the positive power lens 1 may include glass, and the material of the negative power lens 2 may include plastic. The material density of glass is greater than that of plastic, and the volume difference between the positive power lens 1 and the negative power lens 2 is small, so that the mass of the positive power lens 1 is greater than that of the negative power lens 2.

[0083] In some embodiments, the positive power lens 1 and the negative power lens 2 may also be Fresnel lenses. Fresnel lenses have uniform light output and high light output efficiency. The optical system 100 with this design has more uniform screen brightness. In addition, Fresnel lenses have a small thickness, which is beneficial to the thinning of the optical system 100.

[0084] In some embodiments, such as Figure 1 As shown, display 3 can be a liquid crystal display (LCD), an organic light-emitting diode (OLED), or a liquid crystal on silicon (LCOS), etc. Display 3 is a micro display with a diagonal length ranging from 1.5 inches to 2.5 inches. For example, the diagonal length of display 3 is 1.5 inches, 1.8 inches, 2 inches, 2.3 inches, or 2.5 inches.

[0085] The inventors of this disclosure have discovered that the refractive index of the positive power lens 1 and the refractive index of the negative power lens 2 are set such that one of them has a greater refractive index than the other, the larger refractive index is the first refractive index, the smaller refractive index is the second refractive index, the first refractive index is greater than 1.7, the second refractive index is greater than 1.5, and the ratio of the first refractive index to the second refractive index is less than or equal to 1.1. For example, the ratio of the first refractive index to the second refractive index is 1.01, 1.03, 1.05, 1.07, or 1.09. In this case, the field of view of the viewing image of the optical system 100 can be further increased, making the optical system 100 thinner and lighter.

[0086] As mentioned earlier, such as Figure 1 As shown, the first convex surface 11 and the second convex surface 12 of the positive power lens 1 can both be aspherical, and the third convex surface 21 and the fourth concave surface 22 of the negative power lens 2 can both be aspherical. For example, the first convex surface 11, the second convex surface 12, the third convex surface 21 and the fourth concave surface 22 can all be even-order aspherical, and the surface shape equations of the first convex surface 11, the second convex surface 12, the third convex surface 21 and the fourth concave surface 22 are all as follows (2):

[0087]

[0088] refer to Figure 5 Taking the second convex surface 12 as an example, in formula (2), Z is the perpendicular distance between point E on the lens surface (second convex surface 12) and the first reference surface N, and the first reference surface N is tangent to the vertex P2 of the lens surface; c is the curvature at vertex P2 of the lens surface; k is the quadratic surface coefficient of the lens surface; r is the perpendicular distance between point E on the lens surface and the optical axis A; A 2i The coefficient of the multiplication term is i; i ≥ 1 and is an integer.

[0089] Based on this, the inventors designed experiments to verify the results. The specific values ​​of each parameter of the optical system 100 can be found in Tables 1 and 2 below:

[0090]

[0091]

[0092] Table 1

[0093] In Table 1, "f" refers to the focal length of the optical system 100; "TL" refers to the length of the optical system 100; "FOV (Field of View)" refers to the field of view of the optical system 100; "R" refers to the radius of curvature of the lens surface, where a positive radius of curvature means the center of the lens surface is located on the side closer to the display 3, and a negative radius of curvature means the center of the lens surface is located on the side farther away from the display 3; "T" refers to the distance between two adjacent lens surfaces, for example, referring to... Figure 5 Along optical axis A, the distance between the first convex surface 11 and the second convex surface 12 is 13mm. (Reference) Figure 2 Along the optical axis A, the distance between the second convex surface 12 and the third convex surface 21 is 0.5 mm. (Reference) Figure 7 Along optical axis A, the distance between the third convex surface 21 and the fourth concave surface 22 is 4mm. (Reference) Figure 1 Along the optical axis A, the distance between the fourth concave surface 22 and the surface 31 of the display 3 is 16.5 mm; "N" refers to the refractive index of the lens; "V" refers to the dispersion coefficient of the lens.

[0094] The positive power lens 1 has a refractive index of 1.76 and a dispersion coefficient of 52.3, while the negative power lens 2 has a refractive index of 1.64 and a dispersion coefficient of 22.4. The ratio of the refractive index of the positive power lens 1 to that of the negative power lens 2 is 1.07. The first ratio of the dispersion coefficient to the refractive index of the positive power lens 1 is 29.72, and the second ratio of the dispersion coefficient to the refractive index of the negative power lens 2 is 13.66. The ratio of the first ratio to the second ratio is 2.2.

[0095]

[0096] Table 2

[0097] In addition, such as Figure 1 As shown, the diagonal length of display 3 is 2.1 inches, and the pixel density of display 3 is 1500, that is, the number of pixels per inch (PPI) of display 3 is 1500.

[0098] The experimental results can be referenced. Figures 8-10 , Figure 8 The diagram shows the spot size distribution (OBJ) of the optical system 100 at different viewing angles. The geometric spot radius is 32 μm at a viewing angle of 0°, 79 μm at 7.5°, 132 μm at 15°, 79 μm at 22.5°, 125 μm at 30°, 141 μm at 37.5°, and 157 μm at 45°. It is evident that the geometric spot radius is largest at 45°, therefore, its root mean square radius is also the largest, at 64 μm.

[0099] Figure 9 The field curvature diagram of the optical system 100 is shown. The solid lines in the field curvature diagram represent the field curvature of light of different wavelengths in the meridional direction, and the dashed lines represent the field curvature of light of different wavelengths in the sagittal direction. It can be seen that when the viewing angle is within the range of 0 to 45°, the field curvature of the optical system 100 is less than 2.0 mm.

[0100] Figure 10The distortion diagram {F-Tan(Theta)Distortion} of light emitted by the optical system 100 at different wavelengths is shown. It can be seen that the distortion of the optical system 100 is less than 10% when the viewing angle is in the range of 0 to 45°. For example, the distortion of the optical system 100 is the largest at a viewing angle of 45°, which is 7%. The small maximum distortion of the optical system 100 proves that the optical system 100 has small aberrations and high image quality.

[0101] In some embodiments, such as Figure 11 As shown, the optical system 100 also includes a fixed member 101 and a movable member 102 that are slidably connected. The positive power lens 1 and the negative power lens 2 are disposed on the fixed member 101, and the display 3 is disposed on the movable member 102. The movable member 102 is configured to drive the display 3 to move along the optical axis A, thereby adjusting the diopter of the optical system 100.

[0102] For example, such as Figure 11 As shown, along the optical axis A, the distance S1 between the optical center C2 of the negative power lens 2 and the center C3 of the display 3 is 16.5 mm. In this case, the diopter of the optical system 100 is -1D.

[0103] For example, such as Figure 12 As shown, the moving part 102 drives the display 3 to move closer to the negative power lens 2. Along the optical axis A, the distance S2 between the optical center C2 of the negative power lens 2 and the center C3 of the display 3 is 13.6 mm. In this case, the diopter of the optical system 100 is -6D.

[0104] With the above design, the refractive power of the optical system 100 can be adjusted by moving the display 3 along the optical axis A via the moving part 102. For example, the refractive power of the optical system 100 can be continuously adjusted from -1D to -6D.

[0105] like Figure 13 As shown, some embodiments of this disclosure also provide a VR display device 200, which may include the optical system 100 as described in the above embodiments.

[0106] The VR display device 200 disclosed herein has small aberrations, small distortions, and high image quality, which can bring viewers a strong sense of immersion. In addition, the VR display device 200 has high light emission efficiency, a large field of view, and is lightweight and comfortable to wear.

[0107] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. An optical system having an optical axis, the optical system comprising, in order along the optical axis, a positive lens, a negative lens, and a display; the positive lens comprising a first convex surface distal to the display and a second convex surface proximal to the display, the first convex surface and the second convex surface are both convex with respect to the optical center of the positive lens; the negative lens comprising a third convex surface distal to the display and a fourth concave surface proximal to the display, the third convex surface is convex with respect to the optical center of the negative lens, and the fourth concave surface is concave with respect to the optical center of the negative lens; wherein a refractive index of one of the positive lens and the negative lens is greater than a refractive index of the other, the greater refractive index is a first refractive index, the smaller refractive index is a second refractive index, the first refractive index is greater than 1.7, the second refractive index is greater than 1.5, and a ratio of the first refractive index to the second refractive index is less than or equal to 2; a radius of curvature of the fourth concave surface is greater than 0 and less than or equal to 50 mm; a radius of curvature of the third convex surface is greater than 0 and less than or equal to 100 mm.

2. The optical system of claim 1, wherein, a radius of curvature of the fourth concave surface of the negative lens is less than a radius of curvature of the third convex surface.

3. The optical system of claim 1 or 2, wherein, the negative lens comprises a middle portion proximal to the optical axis and a peripheral portion surrounding the middle portion; along the optical axis, a thickness of the middle portion is less than a thickness of the peripheral portion.

4. The optical system of claim 1, wherein, the ratio of the first refractive index to the second refractive index is less than or equal to 1.

1.

5. The optical system of claim 1, wherein, The positive power lens has an optical power ranging from 0.05 mm -1 0.15 mm -1 ; the refractive index of the positive lens is greater than the refractive index of the negative lens.

6. The optical system of claim 5, wherein, The power of the negative power lens ranges from -0.1 mm -1 -0.02 mm -1 .

7. The optical system of claim 1, wherein, the first refractive index is N1, and the second refractive index is N2; along the optical axis, a distance between the second convex surface of the positive lens and the third convex surface of the negative lens is D; wherein .

8. The optical system of claim 7, wherein, along the optical axis, the distance between the second convex surface of the positive lens and the third convex surface of the negative lens ranges from 0.5 mm to 0.55 mm.

9. The optical system of claim 7 or 8, wherein, along the optical axis, a distance between an apex of the first convex surface of the positive lens and a surface of the display distal to the negative lens is less than or equal to 35 mm.

10. The optical system of claim 1, wherein, The refractive index of the positive power lens is N a , and the Abbe number is V a . The refractive index of the negative power lens is N b , and the Abbe number is V b . wherein and one of R1and R2is greater than the other, the ratio of the greater to the lesser is less than or equal to 2.

5.

11. The optical system of claim 1, wherein, the first convex surface, the second convex surface, the third convex surface, and the fourth concave surface are all aspheric surfaces.

12. The optical system of claim 11, wherein, the first convex surface, the second convex surface, the third convex surface, and the fourth concave surface are all even aspheric surfaces; The surface equations of the first convex surface, the second convex surface, the third convex surface and the fourth concave surface are ; wherein Z is the perpendicular distance of a point of the lens surface from a first reference surface which is tangent to the vertex of the lens surface; c is the curvature at the vertex of the lens surface; k is the quadratic surface coefficient of the lens surface; and r is the perpendicular distance of a point of the lens surface from the optical axis; are the multiple term coefficients; i > 1, and is an integer.

13. The optical system of claim 1, wherein, a material of the positive lens comprises glass, and a material of the negative lens comprises plastic.

14. The optical system of claim 1, wherein, a mass of the positive lens is greater than a mass of the negative lens. 15.The optical system of claim 1, further comprising: a fixed member; the positive lens and the negative lens are disposed on the fixed member; a moving member in sliding connection with the fixed member; the display is disposed on the moving member, and the moving member is configured to move the display along the optical axis.

16. A VR display device comprising: the optical system of any one of claims 1-15.

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