Night vision objective lens suitable for AR equipment and AR equipment

Abstract

The invention discloses a night vision objective lens suitable for AR equipment and the AR equipment. The night vision objective lens comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane which are sequentially arranged in the optical axis direction. One surface, close to the diaphragm, of the third lens is a binary surface; one surface, close to the diaphragm, of the fourth lens is a binary surface; the face, close to the diaphragm, of the fifth lens is a Zernike free-form surface, and the face, away from the diaphragm, of the sixth lens is a Zernike free-form surface. Compared with the prior art, the problems that the AR equipment is poor in imaging quality and poor in use experience in a dark environment can be effectively solved, then the use experience of a user is improved, and the use scene of the AR equipment is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of augmented reality, and in particular to a night vision objective lens suitable for an AR device and an AR device. Background Art

[0002] Augmented Reality (AR) is a technology that calculates the position and angle of camera images in real time and adds corresponding images. It is a new technology that "seamlessly" integrates real-world information and virtual-world information. The goal of this technology is to put the virtual world on the real world on the screen and interact with it. With the continuous development of technology, AR technology has also been developed and applied. However, existing AR devices have poor imaging quality in dark environments and poor user experience, which limits the application and promotion of AR devices.

[0003] In view of this, it is necessary to provide a night vision objective lens and an AR device suitable for AR devices to solve the above problems. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a night vision objective lens and an AR device suitable for AR devices, which can effectively solve the problems of poor imaging quality and poor user experience of AR products in dark environments, thereby expanding the use scenarios of AR devices.

[0005] To achieve the above-mentioned purpose, the present invention provides a night vision objective lens suitable for AR equipment, which includes a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane arranged in sequence along the optical axis; a side of the third lens close to the aperture is a binary surface, and a side of the fourth lens close to the aperture is a binary surface; a side of the fifth lens close to the aperture is a Zernike free-form surface, and a side of the sixth lens away from the aperture is a Zernike free-form surface.

[0006] In a preferred embodiment, the radial size of the binary surface of the third lens is R1, and satisfies R1>7.25 mm.

[0007] In a preferred embodiment, the radial size of the binary surface of the fourth lens is R2, and satisfies R2>7mm.

[0008] In a preferred embodiment, the diffraction order of the binary surface of the third lens is M1, the diffraction efficiency of the binary surface of the third lens is η1, and M1 is first order, and 81%≤η1≤94.9% is satisfied.

[0009] In a preferred embodiment, the diffraction order of the binary surface of the fourth lens is M2, the diffraction efficiency of the binary surface of the fourth lens is η2, and M2 is first order, and 81%≤η2≤94.9%.

[0010] In a preferred embodiment, the first lens is a positive refractive power lens, the second lens is a biconcave negative refractive power lens, the third lens is a positive refractive power lens, the fourth lens is a positive refractive power lens, the fifth lens is a positive refractive power lens, the sixth lens is a positive refractive power lens, and the seventh lens is flat glass.

[0011] In a preferred embodiment, the focal length of the night vision objective lens suitable for the AR device is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, and the focal length of the sixth lens is f6, and satisfies:

[0012] 1.8<f1 / f<2.2; 0.8<f2 / f<1.3; 2<f3 / f<2.2; 1.4<f4 / f<1.65; 1.4<f5 / f<1.8; 1.8<f6 / f<2.2.

[0013] In a preferred embodiment, the shape factor of the first lens is X1, the shape factor of the second lens is X2, and they satisfy:

[0014] 2 <X1<2.5;-0.01<X2<-0.005。

[0015] In a preferred embodiment, the thickness of the seventh lens is H, and satisfies: 3mm≤H≤6mm.

[0016] A second aspect of the present invention provides an AR device, which includes the night vision objective lens suitable for an AR device in any of the aforementioned embodiments.

[0017] The beneficial effects of the present invention are as follows: it adopts the technical solution of a diffraction hybrid free-form surface objective lens, uses a lens with a binary surface to replace the double-cemented lens in a spherical objective lens, and then adjusts the weight of the Zernike free-form surface, so that the night vision objective lens can obtain a larger relative aperture, can be better compatible with the relatively large field of view of AR, and can effectively eliminate chromatic aberration and improve imaging quality; and can simplify the structure of the night vision objective lens, reduce the volume and weight of the objective lens, and thus can better adapt to the scene of AR equipment being used at night, improve imaging quality, and improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of equipping AR devices with low-light night vision devices;

[0019] Figure 2A schematic diagram of the structure of a night vision objective lens applicable to an AR device provided in an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of the initial structure of a night vision objective lens applicable to an AR device provided by an embodiment of the present invention;

[0021] Figure 4 A spot diagram of a night vision objective lens applicable to an AR device provided by an embodiment of the present invention;

[0022] Figure 5 An MTF diagram of a night vision objective lens applicable to an AR device provided by an embodiment of the present invention;

[0023] Figure 6 Field curvature and distortion diagram of a night vision objective lens applicable to an AR device provided in an embodiment of the present invention;

[0024] Figure 7 An energy distribution diagram of a night vision objective lens applicable to an AR device provided by an embodiment of the present invention;

[0025] Figure 8 An image plane illumination distribution diagram of a night vision objective lens suitable for an AR device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In the present invention, the terms "disposed", "provided with" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0028] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The existing optical display solutions in AR technology mainly include prism solution, birdbath solution, free-form surface solution, off-axis holographic lens solution and waveguide solution. In the process of AR design, different optical display solutions can be selected according to the characteristics of different application scenarios.

[0031] Please refer to Figure 1 In order to enable the AR device 200 to be used in night scenes, the AR device 200 is usually equipped with a low-light night vision device 100 to enable the use of AR in night scenes. In order to enable AR to obtain a better viewing effect, the AR field of view has reached more than 50°, and the night vision objective is an important component of the low-light night vision device 100. Its imaging quality will directly affect the observation performance of the low-light night vision device 100. The existing night vision objective is mainly designed with spherical glass materials, which cannot adapt well to relatively large field of view angles, and its structure is complex, and its size and weight are both large, which is not suitable for long-term wear, and the imaging quality cannot well meet the user's usage needs.

[0032] Based on the image plane illumination calculation formula It can be seen that (where L0 is the brightness of the observed target, τ0 is the transmittance of the objective lens, is the relative aperture of the objective lens), the illumination E0 of the image plane center of the objective lens is proportional to the square of the relative aperture of the objective lens. In order to obtain sufficient image plane illumination, the objective lens should have as large a relative aperture as possible. The larger the relative aperture of the objective lens, the stronger its light-gathering ability is, and more luminous radiation can be collected, but the large relative aperture makes it difficult to correct the system aberration.

[0033] To this end, the present invention provides a night vision objective lens and an AR device suitable for an AR device. Based on the dispersion characteristics of a diffractive optical element, a lens with a diffractive surface is used to replace the double-cemented lens in a spherical objective lens. By adjusting the type and parameters of the lens in the night vision objective lens, the night vision objective lens can obtain a larger relative aperture, be better compatible with the relatively large field of view of AR, and effectively eliminate chromatic aberration to improve imaging quality. The night vision objective lens can also be simplified in structure, and its volume and weight can be reduced, so that it can be better adapted to the scenarios where the AR device 200 is used at night, thereby improving imaging quality and user experience.

[0034] Specifically, the following is the content provided by the first aspect of the present invention:

[0035] Please refer to Figure 2In this embodiment, a night vision objective lens suitable for an AR device includes a first lens 1, a second lens 2, a third lens 3, an aperture 8, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7 and an image plane 9 arranged in sequence along an optical axis.

[0036] The aperture 8 is located approximately in the middle of the lens group, so that the lens group forms an approximately symmetrical structure. The side of the first lens 1 away from the aperture 8 is the first surface 11, and the side close to the aperture 8 is the second surface 12; the side of the second lens 2 away from the aperture 8 is the third surface 21, and the side close to the aperture 8 is the fourth surface 22; the side of the third lens 3 away from the aperture 8 is the fifth surface 31, and the side of the third lens 3 close to the aperture 8 is the sixth surface 32, the sixth surface 32 is a binary surface, serving as the first diffraction surface; the side of the fourth lens 4 close to the aperture 8 is the seventh surface 41, the seventh surface 41 is a binary surface, serving as the second diffraction surface, and the fourth lens 4 away from the aperture 8 is the seventh surface 41. One side of the aperture 8 is the eighth surface 42; the side of the fifth lens 5 close to the aperture 8 is the ninth surface 51, the ninth surface 51 is a Zernike free-form surface, and the side of the fifth lens 5 away from the aperture 8 is the tenth surface 52; the side of the sixth lens 6 close to the aperture 8 is the eleventh surface 61, the side of the sixth lens 6 away from the aperture 8 is the twelfth surface 62, the twelfth surface 62 is a Zernike free-form surface; the side of the seventh lens 7 close to the aperture 8 is the thirteenth surface 71, and the side of the seventh lens 7 away from the aperture 8 is the fourteenth surface 72.

[0037] Specifically, the first lens 1 is an ordinary spherical lens with positive refractive power and is a meniscus lens; the second lens 2 is an ordinary spherical lens with biconcave negative refractive power, and the shape factor of the first lens 1 is X1, the shape factor of the second lens 2 is X2, and they satisfy: <X1<2.5;-0.01<X2<-0.005。

[0038] The third lens 3 is a positive refractive power lens, the fourth lens 4 is a positive refractive power lens, the fifth lens 5 and the sixth lens 6 are both positive refractive power lenses, and are both meniscus lenses. The seventh lens 7 is a flat glass, and the thickness of the seventh lens 7 is H, and satisfies: 3mm≤H≤6mm; it plays a protective role for the cathode of the image intensifier in the low-light night vision device 100.

[0039] Furthermore, the focal length of the night vision objective lens suitable for the AR device is f, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, and the focal length of the sixth lens 6 is f6, and the following conditions are satisfied:

[0040] 1.8<f1 / f<2.2; 0.8<f2 / f<1.3; 2<f3 / f<2.2; 1.4<f4 / f<1.65; 1.4<f5 / f<1.8; 1.8<f6 / f<2.2.

[0041] It can be understood that by setting the aperture 8 at a position approximately in the middle of the lens group, the lens group forms a quasi-symmetrical structure, which is conducive to reducing aberrations such as coma, astigmatism and distortion of the objective lens. Using a binary surface as a diffraction surface and using the sixth surface 32 and the seventh surface 41 as binary surfaces is conducive to the correction of chromatic aberration and can reduce field curvature at the same time. Using the ninth surface 51 and the twelfth surface 62 as Zernike free-form surfaces, the ninth surface 51 is relatively closer to the aperture 8, which is conducive to reducing the field curvature and astigmatism of the night vision objective lens, and the twelfth surface 62 is relatively closer to the image plane 9, which increases the degree of freedom of aberration correction near the image plane 9, thereby reducing the total length of the night vision objective lens and improving the image quality.

[0042] Compared with the method of eliminating chromatic aberration by using double-cemented lenses in existing objective lenses, the night vision objective lens suitable for AR devices provided in this embodiment adopts the technical solution of diffraction hybrid free-form surface objective lens, which uses a lens with a binary surface to replace the double-cemented lens in the spherical objective lens, and then adjusts the weight of the Zernike free-form surface, so that the night vision objective lens can obtain a larger relative aperture, be better compatible with the relatively large field of view of AR, and effectively eliminate chromatic aberration and improve imaging quality; it can also simplify the structure of the night vision objective lens, reduce the volume and weight of the objective lens, and thus better adapt to the scenarios where the AR device 200 is used at night, improve imaging quality, and improve user experience.

[0043] Furthermore, in one embodiment, the radial size of the binary surface of the third lens 3 is R1, and satisfies R1>7.25mm; the radial size of the binary surface of the fourth lens 4 is R2, and satisfies R2>7mm.

[0044] Furthermore, in one embodiment, the diffraction order of the binary surface of the third lens 3 is M1, the diffraction efficiency of the binary surface of the third lens 3 is η1, and M1 is level 1, 81%≤η1≤94.9%. The diffraction order of the binary surface of the fourth lens 4 is M2, the diffraction efficiency of the binary surface of the fourth lens 4 is η2, and M2 is level 1, 81%≤η2≤94.9%.

[0045] Based on the theory of diffraction efficiency of diffraction elements, the phase distribution of binary diffraction elements satisfies the formula -2kπ=A1ρ 2 +A2ρ 4 +A3ρ 6 +…+A N ρ 2N , where k is the number of rings, and the ring interval can be expressed as Δρ = ρk -ρ k-1 After the radial size of the binary surface is determined, the more ring bands are to be produced on the binary surface, the smaller the minimum value of the ring band interval Δρ will be, the smaller the characteristic size of the binary surface will be, and the higher the requirements for the processing technology will be.

[0046] In a preferred embodiment, the number of etching steps of the binary surface of the third lens 3 is 6 or 8, the etching depth range corresponding to each step is 0.187um≤h≤0.25um, the total number of ring zones is 246, and the ring zone interval Δρ≥1.98um, that is, the minimum feature of the binary surface of the third lens 3 is 1.98um. The number of etching steps of the binary surface of the fourth lens 4 is 6 or 8, the total number of ring zones is 146, and the minimum feature of the binary surface of the fourth lens 4 is 5.05um. It can be understood that the dimensions of the binary surface of the third lens 3 and the binary surface of the fourth lens 4 can be processed using existing processing technology.

[0047] The night vision objective lens for AR devices provided in this embodiment adopts a diffractive hybrid free-form surface objective lens solution. Specifically, it uses a double Gaussian-like optical structure as the initial structure, and then uses a lens with a diffractive surface to replace the double cemented lens in the initial structure. Please refer to Figure 2 and Figure 3 , the following is the preliminary design process of the lens group of the night vision objective lens suitable for AR devices:

[0048] First, separate the first double cemented lens 10 in the initial structure 300, add constraints to limit the focal length of the lens, and facilitate equivalent replacement. Add a diffraction surface on the second cemented lens 101, the diffraction surface is a binary surface, the step size of the binary surface is close to infinitesimal or smaller than the wavelength of light, and its phase formula is where N is the number of terms in the polynomial, M is the diffraction order, ρ is the normalized polar aperture coordinate, and a i is the quadratic phase coefficient, which determines the paraxial focal power of the diffraction surface.

[0049] In order to eliminate the chromatic aberration of the optical system, the binary surface is set on the side close to the aperture 8 to better correct the aberrations such as coma and astigmatism of the optical system and constrain the chromatic aberration of the optical system. The above constraints are removed, and the phase coefficient of the binary surface is used as a variable to optimize the optical system as a whole.

[0050] Similarly, repeat the aforementioned steps, replace the second double-cemented lens 20 in the initial structure 300 with a lens with a binary surface, and set the binary surface on the surface close to the aperture 8, and use the structural parameters of each lens in the replaced lens group and the phase coefficients of the two binary surfaces as variables, and perform multiple iterative optimizations to preliminarily obtain a six-piece objective lens structure.

[0051] Then, the chromatic aberration of the objective lens structure is adjusted to meet the requirements. Specifically, the number of phase coefficients of the binary plane is gradually increased. At the same time, other constraint operands such as modulation transfer function and distortion are added to the optimization constraints. By increasing the weight ratio of the system's vertical axis chromatic aberration in the constraints, the entire system is carefully optimized many times, and finally 6 phase coefficients are obtained. The chromatic aberration of the optical system is better corrected.

[0052] Next, the imaging quality is adjusted to meet the requirements. Specifically, the side of the fifth lens 201 in the objective lens structure close to the aperture and the side of the sixth lens 30 close to the image plane are respectively set as free-form surfaces. The mathematical expression of the free-form surface is: In this formula, c is the curvature at the vertex of the aspheric surface, k is the cone coefficient, and r is the distance from any point on the aspheric surface to the optical axis. is a Zernike polynomial, A j+1 are polynomial coefficients, z j is the number of terms in the polynomial, each term corresponds to a special optical aberration, and the Zernike polynomial coefficient of the free surface is gradually increased from A1 to A6, the weight ratio of the system modulation transfer function in the constraint condition is increased, the total length of the system is increased in the constraint condition, the system is optimized again, and finally the variables of the material itself are used to adjust the weights multiple times to obtain a six-piece night vision objective with a large aperture and a large field of view.

[0053] Furthermore, in order to better illustrate the imaging conditions of the night vision objective lens suitable for AR devices, the performance parameters of the night vision objective lens will be described below. It can be understood that the following data is not a limitation of the night vision objective lens suitable for AR devices provided by the present invention.

[0054] Please refer to Figure 4 , Figure 4 This is a point diagram of a night vision objective lens suitable for AR devices. It can be seen from the figure that the corresponding root mean square radii under the five fields of view are 5.234μm, 9.491μm, 6.637μm, 5.440μm and 5.237μm respectively. It can be understood that the aforementioned root mean square radii are all within the size of one pixel, and their imaging can be received by the image intensifier.

[0055] Please refer to Figure 5 , Figure 5 This is the MTF curve of the night vision objective lens suitable for AR devices. It can be seen from the figure that at the full field of view, the lowest system transfer function value is greater than 0.3. It can be understood that the image quality of the night vision objective lens suitable for AR devices has met the imaging requirements.

[0056] Please refer to Figure 6 , Figure 6The field curvature and distortion curve of the night vision lens suitable for AR devices is shown in the figure. It can be seen from the figure that under the full field of view, the field curvature of any working wavelength is less than 0.062mm, and the distortion value does not exceed 3.4%. It can be understood that the image quality of the night vision lens suitable for AR devices has met the imaging requirements.

[0057] Please refer to Figure 7 , Figure 7 This is an energy distribution diagram of a night vision objective lens suitable for AR devices. It can be seen from the figure that within a pixel size, the energy of the optical system accounts for more than 80% of the energy of the image plane 9, so the focusing effect of the night vision objective lens suitable for AR devices is relatively good.

[0058] Please refer to Figure 8 , Figure 8 This is the image plane illumination distribution diagram of the night vision objective lens suitable for AR devices. From the figure, we can analyze that the system image plane illumination will gradually decrease from the center to the edge of the field of view, until the illumination is close to 60% at the very edge, which basically meets the theoretical design requirements.

[0059] In summary, the night vision objective lens suitable for AR devices provided by the present invention adopts the technical solution of a diffraction hybrid free-form surface objective lens, and uses a lens with a binary surface to replace the double-cemented lens in the spherical objective lens, and then adjusts the weight of the Zernike free-form surface. The night vision objective lens can obtain a larger relative aperture, be better compatible with the relatively large field of view of AR, and effectively eliminate chromatic aberration and improve imaging quality. It can also simplify the structure of the night vision objective lens, reduce the volume and weight of the objective lens, and thus better adapt to the scenarios where the AR device 200 is used at night, improve imaging quality, and improve the user experience.

[0060] The following is the content of the second aspect of the present invention:

[0061] The present invention provides an AR device 200, which includes the aforementioned night vision objective lens suitable for AR devices. The AR device 200 can better adapt to nighttime usage scenarios, has relatively better imaging quality, and the overall volume and weight of the AR are relatively small, which can effectively improve the user experience.

[0062] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A night vision objective lens suitable for AR equipment, characterized in that: The invention comprises a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane which are arranged in sequence along the optical axis; a surface of the third lens close to the aperture is a binary surface, a surface of the fourth lens close to the aperture is a binary surface; a surface of the fifth lens close to the aperture is a Zernike free-form surface, and a surface of the sixth lens away from the aperture is a Zernike free-form surface.

2. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The radial size of the binary surface of the third lens is R1, and satisfies R1>7.25mm.

3. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The radial size of the binary surface of the fourth lens is R2, and satisfies R2>7mm.

4. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The diffraction order of the binary surface of the third lens is M1, the diffraction efficiency of the binary surface of the third lens is η1, and M1 is first order, and 81%≤η1≤94.9%.

5. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The diffraction order of the binary surface of the fourth lens is M2, the diffraction efficiency of the binary surface of the fourth lens is η2, and M2 is first order, and 81%≤η2≤94.9%.

6. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The first lens is a positive refractive power lens, the second lens is a biconcave negative refractive power lens, the third lens is a positive refractive power lens, the fourth lens is a positive refractive power lens, the fifth lens is a positive refractive power lens, the sixth lens is a positive refractive power lens, and the seventh lens is flat glass.

7. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The focal length of the night vision objective lens suitable for the AR device is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, and the focal length of the sixth lens is f6, and the following conditions are satisfied: 1.8<f1 / f<2.2; 0.8<f2 / f<1.3; 2<f3 / f<2.2; 1.4<f4 / f<1.65; 1.4<f5 / f<1.8; 1.8<f6 / f<2.

2.

8. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The shape factor of the first lens is X1, the shape factor of the second lens is X2, and they satisfy: 2 <X1<2.5;-0.01<X2<-0.005。 9. The night vision objective lens suitable for AR equipment according to claim 1, characterized in that: The thickness of the seventh lens is H, and satisfies: 3mm≤H≤6mm.

10. An AR device, characterized in that: A night vision objective lens suitable for an AR device comprising any one of claims 1 to 9.

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