Optical system and optical apparatus

Abstract

The utility model provides an optical system and optical equipment. The optical system comprises a display screen, a first lens, a second lens and a third lens which are sequentially arranged along an optical axis. A first pancake composite film is arranged on the surface of the side, close to the first lens, of the display screen. The first lens is a convex-concave lens with negative focal power, and a semi-transparent and semi-reflective film is arranged on the surface of one side, close to the display screen, of the first lens. And the second lens is a biconvex lens with positive focal power. The third lens is a plano-convex lens with positive focal power, and a second pancake composite film is arranged on the surface of one side, close to the second lens, of the third lens. And the exit pupil distance of the optical system is 30-40 mm. The optical system and the optical device provided by the utility model have a large object plane and a large exit pupil distance, and can effectively improve the user experience.

Description

Technical Field

[0001] The present application relates to the technical field of optical instruments, and in particular to an optical system and an optical device. Background Art

[0002] Currently, eyepiece lenses are widely used in optical fields such as telescopes, microscopes and sights. The lenses in traditional eyepieces are made of glass or plastic, and light propagates in one direction in the eyepiece. In order to meet certain specific optical index requirements, the eyepiece has to use more lenses or aspherical surfaces to meet the imaging requirements during optical design, which will increase the size, weight and cost of the eyepiece.

[0003] Currently, Pancake (folded optical path) technology has begun to be used in the field of VR (virtual reality) technology to reduce the overall size and weight of the lens. Pancake technology further compresses the thickness of the optical module, improving the user's sense of immersion and wearing comfort. The key point of the Pancake optical solution is to fold the optical path through a lens with a semi-transparent and semi-reflective polarizing film, then make multiple returns, and finally shoot into the human eye. Although Pancake technology effectively reduces the size and weight of the eyepiece, the eyepiece in the existing technology still has problems such as a small object surface and a small exit pupil distance, which affects the user experience. Summary of the invention

[0004] Based on this, the present application provides an optical system and an optical device to improve the problems existing in the prior art such as small object plane and small exit pupil distance.

[0005] To achieve the above purpose, the technical solution of the embodiment of the present application is implemented as follows:

[0006] On the one hand, an embodiment of the present application provides an optical system, comprising a display screen, a first lens, a second lens, and a third lens sequentially arranged along an optical axis;

[0007] A first pancake composite film is provided on a surface of the display screen on one side close to the first lens;

[0008] The first lens is a convex-concave lens with negative optical power, and a semi-transparent and semi-reflective film is provided on the surface of the first lens close to the display screen;

[0009] The second lens is a biconvex lens with positive optical power;

[0010] The third lens is a plano-convex lens with positive power, and a second pancake composite film is provided on the surface of the third lens close to the second lens;

[0011] The exit pupil distance of the optical system is 30-40 mm.

[0012] In one embodiment, the radius of curvature of the surface of the first lens on the side close to the display screen is 130 to 180 mm, the radius of curvature of the surface of the first lens on the side close to the second lens is 10 to 60 mm, and the focal length of the first lens is -30 to -80 mm.

[0013] In one embodiment, the radius of curvature of the surface of the second lens on the side close to the first lens is 80 to 140 mm, the radius of curvature of the surface of the second lens on the side close to the third lens is 10 to 60 mm, and the focal length of the second lens is 15 to 65 mm.

[0014] In one embodiment, the radius of curvature of the surface of the third lens on the side close to the second lens is infinity, the radius of curvature of the surface of the third lens on the side away from the second lens is -140 to -200 mm, and the focal length of the third lens is 145 to 195 mm.

[0015] In one embodiment, the distance between the surface of the third lens on the side away from the second lens and the display screen is not greater than 22 mm.

[0016] In one embodiment, the diagonal length of the effective display area of the display screen is 14 to 16 mm, and the distance between the display screen and the first lens is greater than 5 mm.

[0017] In one embodiment, the first pancake composite film includes a first quarter-wave plate and a first linear polarizer arranged in sequence, and the first linear polarizer is arranged on the side close to the display screen.

[0018] In one embodiment, the second pancake composite film includes a second quarter-wave plate, a polarization reflection film and a second linear polarizer arranged in sequence, and the second linear polarizer is arranged on the side close to the third lens.

[0019] In one embodiment, the exit pupil diameter of the optical system is 2.5 to 4 mm.

[0020] On the other hand, an embodiment of the present application provides an optical device, including an objective lens and an eyepiece, and the eyepiece includes the optical system as described above.

[0021] The present application has at least the following beneficial effects: The optical system and the optical device provided by the embodiments of the present application respectively provide pancake composite films (the first pancake composite film and the second pancake composite film) on the display screen and the third lens, and provide a semi-transmissive and semi-reflective film on the first lens, so that light is reflected and transmitted inside the optical system, realizing a folded optical path, effectively reducing the volume and weight of the optical system, and being beneficial to reducing the production cost of the optical system. At the same time, by adopting a reasonable lens structure and parameter design, as well as a reasonable lens combination, the exit pupil distance of the optical system is increased, and the user has a better experience when using it. Through the reasonable design of the optical system, the effect of increasing the object surface can also be achieved by providing a larger display screen. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the optical system according to the embodiment of the present application.

[0023] Figure 2 is Figure 1 the optical path schematic diagram of the optical system.

[0024] Figure 3 It is a schematic diagram of the change in the light polarization state of the optical system according to the embodiment of the present application.

[0025] The meanings of the reference numerals in the drawings are as follows:

[0026] 1. Display screen; 10. First pancake composite film; 11. First quarter-wave plate; 12. First linear polarizer;

[0027] 2. First lens; 20. Semi-transmissive and semi-reflective film;

[0028] 3. Second lens;

[0029] 4. Third lens; 40. Second pancake composite film; 41. Second quarter-wave plate; 42. Polarization reflection film; 43. Second linear polarizer;

[0030] 5. Exit pupil position. Detailed Embodiments

[0031] The technical solution of the present application will be further elaborated in detail below in conjunction with the drawings of the description and specific embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit the implementation of this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0033] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0034] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] Please refer to Figure 1 , the optical system of the embodiment of the present application includes a display screen 1, a first lens 2, a second lens 3, and a third lens 4 arranged in sequence along the optical axis.

[0036] As Figure 1 and Figure 2 shown, a first pancake composite film 10 is provided on the surface of the side of the display screen 1 close to the first lens 2. The display screen 1 in this embodiment is a micro display screen 1 for displaying the picture information to be output, and the diagonal length of the effective display area of the screen is 14 - 16 mm. The first pancake composite film 10 includes a first quarter-wave plate 11 and a first linear polarizer 12 arranged in sequence, and the first linear polarizer 12 is arranged on the side close to the display screen 1. The first pancake composite film 10 is attached to the surface of the display screen 1 and is divided into two layers. The inner layer is a linear polarizer that can only transmit polarized light in a specific direction. Here, the first linearly polarized light is used to transmit the linearly polarized light P; the outer layer is used to generate a phase delay to convert linearly polarized light and circularly polarized light into each other. The distance between the display screen 1 and the first lens 2 is greater than 5 mm.

[0037] The first lens 2 is a convex-concave lens with a negative optical power. The radius of curvature of the surface of the first lens 2 on the side close to the display screen 1 is 130 - 180 mm, preferably 150 - 160 mm. The radius of curvature of the surface of the first lens 2 on the side close to the second lens 3 is 10 - 60 mm, preferably 30 - 40 mm. The focal length of the first lens 2 is -30 - -80 mm, preferably -50 - -60 mm. A semi-transmissive and semi-reflective film 20 is provided on the surface of the first lens 2 on the side close to the display screen 1. The semi-transmissive and semi-reflective film 20 is attached to the surface of the first lens 2 on the side close to the display screen 1. It can transmit and reflect light, and the transmittance and reflectance ratio is 1:1. The semi-transmissive and semi-reflective film 20 is an important part for realizing the back-and-forth propagation of light in the lens.

[0038] The second lens 3 is a biconvex lens with a positive optical power. The radius of curvature of the surface of the second lens 3 on the side close to the first lens 2 is 80 - 140 mm, preferably 100 - 120 mm. The radius of curvature of the surface of the second lens 3 on the side close to the third lens 4 is 10 - 60 mm, preferably 30 - 40 mm. The focal length of the second lens 3 is 15 - 65 mm, preferably 35 - 45 mm.

[0039] The third lens 4 is a plano-convex lens with a positive optical power. The radius of curvature of the surface of the third lens 4 on the side close to the second lens 3 is infinite, that is, the side of the third lens 4 close to the second lens 3 is close to a plane. The radius of curvature of the surface of the third lens 4 on the side away from the second lens 3 is -140 - -200 mm, preferably -160 - -180 mm. The focal length of the third lens 4 is 145 - 195 mm, preferably 165 - 175 mm. The distance between the surface of the third lens 4 on the side away from the second lens 3 and the display screen 1 is not greater than 22 mm. A second pancake composite film 40 is provided on the surface of the third lens 4 on the side close to the second lens 3. The second pancake composite film 40 includes a second quarter-wave plate 41, a polarization reflection film 42, and a second linear polarizer 43 arranged in sequence. The second linear polarizer 43 is arranged on the side close to the third lens 4. The second pancake composite film 40 is attached to the surface of the third lens 4 on the side close to the second lens 3 and is divided into three layers. This composite film is an important part for realizing the back-and-forth propagation of light in the lens. The quarter-wave plate is used to generate a phase delay; the polarization reflection film 42 is used to reflect linearly polarized light P and transmit linearly polarized light S; the linear polarizer is used to transmit polarized light in a specific direction and here is used to transmit linearly polarized light S.

[0040] When the human eye is at the exit pupil position 5, a complete screen image can be seen. The exit pupil distance of the optical system of the embodiment of the present application is 30 - 40 mm, and the exit pupil diameter is 2.5 - 4 mm.

[0041] The optical principle of the optical system of the embodiment of the present application is as follows: As Figure 2 andFigure 3 As shown in the figure, after the light emitted by the display screen 1 passes through the first linear polarizer 12, its polarization state becomes linearly polarized light P. After passing through the first quarter-wave plate 11, a phase delay is generated and it becomes right-handed circularly polarized light R. When passing through the semi-transmissive and semi-reflective film 20, half of the incident light is transmitted and the other half is reflected. The polarization state of the transmitted light remains unchanged and is still right-handed circularly polarized light R, and it continues to propagate forward. When the right-handed circularly polarized light R enters the second quarter-wave plate 41, a phase delay is generated, and the right-handed circularly polarized light R becomes linearly polarized light P. When the linearly polarized light P reaches the polarization reflection film 42, since the polarization reflection film 42 has the function of reflecting linearly polarized light P and transmitting linearly polarized light S, therefore, the linearly polarized light P is reflected by the polarization reflection film 42 here. When passing through the second quarter-wave plate 41 again, it becomes right-handed circularly polarized light R and continues to propagate forward to the semi-transmissive and semi-reflective film 20. At the semi-transmissive and semi-reflective film 20, half of the incident light is transmitted and the other half is reflected. The polarization state of the reflected light will change, from right-handed circularly polarized light R to left-handed circularly polarized light L, and it continues to propagate forward to the second quarter-wave plate 41. The left-handed circularly polarized light L is converted into linearly polarized light S here, and after passing through the polarization reflection film 42 and the second linear polarizer 43, it propagates and forms an image in the direction of the human eye.

[0042] The embodiment of the present application also provides an optical device, which includes an objective lens and an eyepiece, and the optical system described in the above embodiment is provided in the eyepiece. The optical device can be an optical imaging device such as a VR virtual reality device.

[0043] The optical system and the optical device provided by the embodiment of the present application, through the design of folding the optical path, enable the light to be refracted and reflected in the optical system, that is, to propagate back and forth in the lens to realize the shortening of the length of the lens barrel. Since the light passes back and forth through the same lens multiple times, the optical path of the light in the optical system is several times the length of the optical system, so the imaging effect that can be presented by a larger number of lenses in the traditional optical system can be achieved with a smaller number of lenses. Compared with the traditional optical system, the total length of the optical system of the embodiment of the present application is greatly shortened, it has an ultra-short lens total length (TTL), has a smaller weight, a larger object surface, and at the same time, also has a larger exit pupil distance and good imaging quality, effectively improving the user experience.

[0044] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising such element.

[0045] As described above, this is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An optical system, characterized in that, It includes a display screen (1), a first lens (2), a second lens (3), and a third lens (4) arranged in sequence along the optical axis; On one side surface of the display screen (1) close to the first lens (2), a first pancake composite film (10) is provided; The first lens (2) is a convex-concave lens with a negative optical power, and on the surface of the first lens (2) close to the display screen (1), a semi-transmissive and semi-reflective film (20) is provided; The second lens (3) is a biconvex lens with a positive optical power; The third lens (4) is a plano-convex lens with a positive optical power, and on the surface of the third lens (4) close to the second lens (3), a second pancake composite film (40) is provided; The exit pupil distance of the optical system is 30 to 40 mm.

2. The optical system according to claim 1, characterized in that, The radius of curvature of the surface of the first lens (2) close to the display screen (1) is 130 to 180 mm, the radius of curvature of the surface of the first lens (2) close to the second lens (3) is 10 to 60 mm, and the focal length of the first lens (2) is -30 to -80 mm.

3. The optical system according to claim 1, characterized in that, The radius of curvature of the surface of the second lens (3) close to the first lens (2) is 80 to 140 mm, the radius of curvature of the surface of the second lens (3) close to the third lens (4) is 10 to 60 mm, and the focal length of the second lens (3) is 15 to 65 mm.

4. The optical system according to claim 1, wherein The radius of curvature of the surface of the third lens (4) close to the second lens (3) is infinity, the radius of curvature of the surface of the third lens (4) away from the second lens (3) is -140 to -200 mm, and the focal length of the third lens (4) is 145 to 195 mm.

5. The optical system according to claim 4, wherein The distance between the surface of the third lens (4) away from the second lens (3) and the display screen (1) is not greater than 22 mm.

6. The optical system according to claim 1, characterized in that, The diagonal length of the effective display area of the display screen (1) is 14 to 16 mm, and the distance between the display screen (1) and the first lens (2) is greater than 5 mm.

7. The optical system according to claim 1, wherein, The first pancake composite film (10) includes a first quarter-wave plate (11) and a first linear polarizer (12) arranged in sequence, and the first linear polarizer (12) is arranged on the side close to the display screen (1).

8. The optical system according to claim 1, characterized in that, The second pancake composite film (40) includes a second quarter-wave plate (41), a polarization reflection film (42), and a second linear polarizer (43) arranged in sequence, and the second linear polarizer (43) is arranged on the side close to the third lens (4).

9. The optical system according to any one of claims 1 to 8, characterized in that, The exit pupil diameter of the optical system is 2.5 to 4 mm.

10. An optical device, characterized in that, It includes an objective lens and an eyepiece, and the eyepiece includes the optical system according to any one of claims 1 to 9.

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