Prime lens

Abstract

The embodiment of the utility model discloses a prime lens. The prime lens comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with positive focal power and a fifth lens with positive focal power which are sequentially arranged from the object space to the image space along the optical axis; wherein the first lens and the third lens are spherical lenses, and the second lens, the fourth lens and the fifth lens are aspheric lenses. According to the prime lens provided by the embodiment of the utility model, the resolution capability is improved by utilizing the scheme that the spherical surface is matched with the aspheric surface, the total optical length of the lens is less than 11.5 mm, the aperture can reach F1.3, the FOV can reach 110 degrees, and the prime lens has the characteristics of large aperture, large field angle and miniaturization, and can be used in the vehicle-mounted field.

Description

Technical Field

[0001] The utility model relates to the technical field of lenses, in particular to a fixed-focus lens. Background Art

[0002] With the development of science and technology, cutting-edge fields such as virtual reality (VR), augmented reality (AR), robotics, security, and autonomous driving are developing rapidly. In these fields, 3D depth cameras capable of 3D depth measurement are usually required. There are generally three technical solutions for 3D depth measurement: dual-camera, structured light, and TOF. TOF is the abbreviation of Time of Flight technology, which calculates the time it takes for light to fly. TOF technology is widely used due to its advantages such as fast response speed, high depth information accuracy, small structure size, and low sensitivity to ambient light interference.

[0003] In the automotive field, traditional automotive TOF lenses are generally more than 13mm in total length, large in size, and high in cost, which is not conducive to lens integration and interior aesthetics, and is not conducive to installation in cars. Utility Model Content

[0004] The utility model provides a fixed-focus lens that uses a combination of spherical and aspherical surfaces to improve resolution. The total optical length of the lens is less than 11.5mm, the aperture can reach F1.3, and the field of view (FOV) can reach 110°. It has the characteristics of large aperture, large field of view and miniaturization, and can be used in the automotive field.

[0005] According to one aspect of the present invention, there is provided a fixed-focus lens, comprising a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with positive optical power, arranged in sequence from the object side to the image side along the optical axis;

[0006] The first lens and the third lens are both spherical lenses, and the second lens, the fourth lens and the fifth lens are all aspherical lenses.

[0007] Optionally, a stop is further included, and the stop is located between the second lens and the third lens.

[0008] Optionally, the first lens is a meniscus lens, the object side surface of the first lens is convex and the image side surface is concave; the second lens is a meniscus lens, the object side surface of the second lens is convex and the image side surface is concave.

[0009] Optionally, the first lens is a glass lens, the refractive index range of the first lens is 1.76 < Nd1 < 2.03, and the Abbe number range of the first lens is 19 < Vd1 < 37.4.

[0010] Optionally, the third lens is a glass lens, the refractive index range of the third lens is 1.8 < Nd3 < 2.05, and the Abbe number range of the third lens is 29 < Vd3 < 41.

[0011] Optionally, the second lens, the fourth lens, and the fifth lens are all plastic lenses.

[0012] Optionally, the refractive index of the fourth lens is greater than that of the fifth lens.

[0013] Optionally, the fixed-focus lens satisfies -3.9 < ((R41 + R42) × F4) / ((R51 + R52) × F5) < 0;

[0014] where, R41 represents the curvature radius of the object side surface of the fourth lens, R42 represents the curvature radius of the image side surface of the fourth lens, F4 represents the focal length of the fourth lens, R51 represents the curvature radius of the object side surface of the fifth lens, R52 represents the curvature radius of the image side surface of the fifth lens, and F5 represents the focal length of the fifth lens. [[ID=]17]

[0015] Optionally, the overall optical length TTL of the fixed-focus lens is < 11.5 mm.

[0016] Optionally, a filter is further included, and the filter is located between the fifth lens and the image plane.

[0017] The fixed-focus lens provided by the embodiment of the present invention includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a fourth lens with a positive optical power, and a fifth lens with a positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; wherein, both the first lens and the third lens are spherical lenses, and the second lens, the fourth lens, and the fifth lens are all aspherical lenses. The technical solution of the embodiment of the present invention can realize a fixed-focus lens that takes into account imaging requirements, has a compact structure, a large aperture, and a large field angle. By using a hybrid combination of 2 spherical lenses and 3 aspherical lenses, it can well correct aberrations, ensure good enough image quality and stable high and low temperature resolution, can meet a large field angle, the total length of the lens is less than 11.5 mm, the aperture can reach F1.3, and the field angle FOV can reach 110°, having good commercial value.

[0018] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic structural diagram of a fixed-focus lens provided in Example 1 of the present utility model;

[0021] Figure 2 is the modulation transfer function (MTF) curve of the fixed-focus lens in Example 1;

[0022] Figure 3 A schematic structural diagram of another fixed-focus lens provided in Example 2 of the present utility model;

[0023] Figure 4 is the MTF curve of the fast Fourier transform of the fixed-focus lens in Example 2;

[0024] Figure 5 A schematic structural diagram of another fixed-focus lens provided in Example 3 of the present utility model;

[0025] Figure 6 This is the MTF curve of the fast Fourier transform of the fixed-focus lens in Example 3. DETAILED DESCRIPTION

[0026] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] Figure 1 This is a structural diagram of a fixed-focus lens provided in Example 1 of the present utility model, with reference to Figure 1 The fixed-focus lens includes a first lens 10 with negative optical power, a second lens 20 with negative optical power, a third lens 30 with positive optical power, a fourth lens 40 with positive optical power, and a fifth lens 50 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the first lens 10 and the third lens 30 are both spherical lenses, and the second lens 20, the fourth lens 40, and the fifth lens 50 are all aspherical lenses.

[0029] It is understood that the focal power is the reciprocal of the focal length and characterizes the ability of an optical system to deflect light. The larger the absolute value of the focal power, the stronger the light bending ability, and the smaller the absolute value of the focal power, the weaker the light bending ability. When the focal power is a positive number, the light refraction is convergent; when the focal power is a negative number, the light refraction is divergent. The first lens 10 and the second lens 20 are both negative lenses. Optionally, the first lens 10 is a meniscus lens with a convex object side and a concave image side; the second lens 20 is a meniscus lens with a convex object side and a concave image side. This arrangement can better allow light to enter the lens, allowing the light to propagate smoothly without excessive deflection, thereby avoiding the introduction of larger aberrations. At the same time, it is beneficial to reduce the aperture and total length of the lens. The third lens 30 to the fifth lens 50 are all positive lenses, used to converge light onto the image plane. Moreover, the combination of spherical lenses and aspherical lenses can better correct aberrations and improve imaging quality.

[0030] Optional, continue to refer to Figure 1 The fixed focus lens further includes an aperture 60, which is located between the second lens 20 and the third lens 30. The aperture 60 is set between the second lens 20 with negative optical power and the third lens 30 with positive optical power, and can be used to block far-axis light, better correct high-order aberrations, and improve imaging quality.

[0031] Optionally, continue to refer to Figure 1 , the fixed-focus lens further includes a filter 70, and the filter 70 is located between the fifth lens 50 and the image plane.

[0032] Among them, setting the filter 70 can filter the light outside the light band of the imaging light. For example, in some embodiments, the imaging light is visible light, and the filter 70 can be set as an infrared filter to avoid the influence of infrared optics on the imaging sensor. Specifically, when implemented, the filtering wavelength of the filter 70 can be designed according to the actual situation.

[0033] Optionally, the first lens 10 is a glass lens, the refractive index range of the first lens 10 is 1.76 < Nd1 < 2.03, and the Abbe number range of the first lens 10 is 19 < Vd1 < 37.4.

[0034] When the refractive index and Abbe number of the first lens 10 are set within the above ranges, the light can be better converged, the ratio of the lens aperture to the radius of curvature can be reduced, and the edge illumination can be improved.

[0035] Optionally, the third lens 30 is a glass lens, the refractive index range of the third lens 30 is 1.8 < Nd3 < 2.05, and the Abbe number range of the third lens 30 is 29 < Vd3 < 41.

[0036] The third lens 30 plays a role in correcting defocus at high and low temperatures. Cooperating with the optical power of other lenses is beneficial to obtaining stable resolution at high and low temperatures.

[0037] Optionally, the second lens 20, the fourth lens 40, and the fifth lens 50 are all plastic lenses.

[0038] Glass spherical lenses are easy to process and have better thermal stability. Plastic aspherical lenses have better aberration correction effects. Designing a glass-plastic hybrid structure can play a complementary role. Using a combination of glass lenses and plastic lenses in the fixed-focus lens can better balance the resolution of the lens and improve the imaging effect.

[0039] Optionally, the refractive index of the fourth lens 40 is greater than the refractive index of the fifth lens 50.

[0040] In the fixed-focus lens provided by the embodiment of the present invention, both the fourth lens 40 and the fifth lens 50 are plastic aspherical lenses. The fourth lens 40 is set as a high-refractive-index material, and the fifth lens 50 is set as a low-refractive-index material. Through the combination of the refractive indices of the two lenses, it is beneficial to chromatic aberration correction, further reducing the aberration of the system, and facilitating the realization of high-definition image quality.

[0041] Optionally, the fixed-focus lens satisfies -3.9 < ((R41 + R42) × F4) / ((R51 + R52) × F5) < 0;

[0042] Among them, R41 represents the curvature radius of the object side surface of the fourth lens 40, R42 represents the curvature radius of the image side surface of the fourth lens 40, F4 represents the focal length of the fourth lens 40, R51 represents the curvature radius of the object side surface of the fifth lens 50, R52 represents the curvature radius of the image side surface of the fifth lens 50, and F5 represents the focal length of the fifth lens 50.

[0043] Optional, fixed-focus lens with a total optical length TTL < 11.5mm.

[0044] The technical solution of the embodiment of the utility model can realize a fixed-focus lens that takes into account imaging requirements, compact structure, large aperture, and large field of view. It adopts a mixed combination of two glass spherical lenses and three plastic aspherical lenses, which can correct aberrations well, ensure sufficiently good image quality and stable high and low temperature resolution, and can meet the requirements of a large field of view. The total length of the lens is less than 11.5mm, the aperture can reach F1.3, and the field of view angle FOV can reach 110°, which has good commercial value.

[0045] In this embodiment, the surface of the aspheric lens satisfies the following formula:

[0046]

[0047] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitting cone coefficient; A, B, C, D, and E are the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspheric polynomial, respectively.

[0048] For example, Table 1 shows Figure 1 Specific parameters of the corresponding fixed-focus lens:

[0049] Table 1 Specific parameters of fixed focus lens

[0050] Scope of protection Example 1 Lower limit Upper limit Nd1 1.807 1.76 2.03 Vd1 36.397 19 37.4 Nd3 2.000 1.8 2.05 Vd3 30.00 29 41.00 ((R41+R42)×F4) / ((R51+R52)×F5) -0.996 -3.9 0

[0051] Table 2 shows the parameter data of each lens in Example 1. Example 1 can realize a fixed-focus lens with a focal length of F=2.436 mm, an aperture number of F=1.3, and a field of view angle FOV=110°.

[0052] Table 2 Design values ​​of optical physical parameters of the fixed focus lens of Example 1

[0053]

[0054]

[0055] The surface numbers are numbered according to the order of the surfaces of each lens. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the image plane, and a negative value indicates that the surface is curved toward the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different number of digits in the values ​​of each parameter, there will be focusing errors. Therefore, the thickness of the 13th surface can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0056] Table 3 shows the design values ​​of the aspheric parameters in Example 1:

[0057]

[0058] Among them, -8.3122835E-03 means that the A coefficient of surface number S3 is -8.3122835×10 -3 .

[0059] Figure 2 This is the Modulation Transfer Function (MTF) curve of the fixed-focus lens in Example 1, calculated by the Fast Fourier Transform. An MTF graph represents the overall resolution of an optical system. The vertical axis in the graph shows the normalized MTF, which indicates the quality of contrast and calibrates the lens's resolution, with higher values ​​being better and 1 being a perfect score. The solid line represents the meridional MTF value, and the dashed line represents the sagittal MTF value. The horizontal axis represents spatial frequency, with 0 representing 0 lp / mm and increasing in frequency as the image moves to the right. As can be seen from the graph, within the wavelength range of 0.92μm to 0.96μm, the MTF value is ≥0.8 at 60 lp / mm in the center field of view and ≥0.55 at 60 lp / mm at the edge of the field of view.

[0060] Figure 3 This is a schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present utility model. Table 4 is a schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present utility model. Figure 3 Specific parameters of the corresponding fixed-focus lens:

[0061] Table 4 Specific parameters of fixed-focus lenses

[0062] Scope of protection Example 2 Lower limit Upper limit Nd1 1.980 1.76 2.03 Vd1 20.004 19 37.4 Nd3 1.850 1.8 2.05 Vd3 40.00 29 41.00 ((R41+R42)×F4) / ((R51+R52)×F5) -1.425 -3.9 0

[0063] Table 5 shows the parameter data of each lens in Example 2. Example 2 can realize a fixed-focus lens with a focal length of F=2.440 mm, an aperture number of F=1.3, and a field of view angle FOV=110°.

[0064] Table 5 Design values ​​of optical physical parameters of the fixed focus lens of Example 2

[0065]

[0066]

[0067] The surface numbers are numbered according to the order of the surfaces of each lens. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the image plane, and a negative value indicates that the surface is curved toward the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different number of digits in the values ​​of each parameter, there will be focusing errors. Therefore, the thickness of the 13th surface can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0068] Table 6 shows the design values ​​of the aspheric parameters in Example 2:

[0069]

[0070] Among them, -7.8127130E-03 means that the A coefficient of surface number S3 is -7.8127130×10 3 .

[0071] Figure 4 This is the Fast Fourier Transform (FT) MTF curve for the fixed-focus lens in Example 2. An MTF graph represents the overall resolution of an optical system. The vertical axis of the graph shows the normalized MTF, which indicates contrast quality and calibrates the lens's resolution, with higher values ​​being better and 1 being a perfect score. The solid line represents the meridional MTF value, and the dashed line represents the sagittal MTF value. The horizontal axis represents spatial frequency, with 0 representing 0 lp / mm and increasing in frequency toward the right. As can be seen from the graph, within the wavelength range of 0.92μm to 0.96μm, the MTF value is ≥0.8 at 60 lp / mm in the center field of view and ≥0.5 at 60 lp / mm at the edge of the field of view.

[0072] Figure 5 This is a structural diagram of another fixed-focus lens provided by an embodiment of the present utility model. Table 7 is a schematic diagram of the fixed-focus lens provided by an embodiment of the present utility model. Figure 5 Specific parameters of the corresponding fixed-focus lens:

[0073] Table 7 Specific parameters of fixed-focus lenses

[0074] Scope of protection Example 3 Lower limit Upper limit Nd1 1.922 1.76 2.03 Vd1 24.679 19 37.4 Nd3 1.944 1.8 2.05 Vd3 40.00 29 41.00 ((R41+R42)×F4) / ((R51+R52)×F5) -2.963 -3.9 0

[0075] Table 8 shows the parameter data of each lens in Example 3. Example 1 can realize a fixed-focus lens with a focal length of F=2.438 mm, an aperture number of F=1.3, and a field of view angle FOV=110°.

[0076] Table 8 Design values ​​of optical physical parameters of the fixed focus lens of Example 3

[0077]

[0078] The surface numbers are numbered according to the order of the surfaces of each lens. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the image plane, and a negative value indicates that the surface is curved toward the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different number of digits in the values ​​of each parameter, there will be focusing errors. Therefore, the thickness of the 13th surface can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0079] Table 9 shows the design values ​​of the aspheric parameters in Example 3:

[0080]

[0081] Among them, -5.6152732E-03 means that the A coefficient of surface number S3 is -5.6152732×10 -3 .

[0082] Figure 6 This is the Fast Fourier Transform (MTF) curve for the fixed-focus lens in Example 3. An MTF graph represents the overall resolution of an optical system. The vertical axis of the graph shows the normalized MTF, which indicates the quality of contrast and calibrates the lens's resolution, with higher values ​​being better and 1 being a perfect score. The solid line represents the meridional MTF value, and the dashed line represents the sagittal MTF value. The horizontal axis represents spatial frequency, with 0 representing 0 lp / mm and increasing in frequency as the value moves to the right. As can be seen from the graph, within the wavelength range of 0.92μm to 0.96μm, the MTF value is ≥0.8 at 60 lp / mm in the center field of view and ≥0.5 at 60 lp / mm at the edge of the field of view.

[0083] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that: It includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a fourth lens with a positive optical power, and a fifth lens with a positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; Among them, the first lens and the third lens are both spherical lenses, and the second lens, the fourth lens, and the fifth lens are all aspherical lenses.

2. The fixed-focus lens according to claim 1, wherein: It further includes an aperture, and the aperture is located between the second lens and the third lens.

3. The fixed-focus lens according to claim 1, wherein: The first lens is a meniscus lens, the object side surface of the first lens is convex, and the image side surface is concave; the second lens is a meniscus lens, the object side surface of the second lens is convex, and the image side surface is concave.

4. The fixed-focus lens according to claim 1, wherein: The first lens is a glass lens, the refractive index range of the first lens is 1.76 < Nd1 < 2.03, and the Abbe number range of the first lens is 19 < Vd1 < 37.

4.

5. The fixed-focus lens according to claim 1, wherein: The third lens is a glass lens, the refractive index range of the third lens is 1.8 < Nd3 < 2.05, and the Abbe number range of the third lens is 29 < Vd3 < 41.

6. The fixed-focus lens according to claim 1, wherein: The second lens, the fourth lens, and the fifth lens are all plastic lenses.

7. The fixed-focus lens according to claim 6, wherein: The refractive index of the fourth lens is greater than that of the fifth lens.

8. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens satisfies -3.9 < ((R41 + R42) × F4) / ((R51 + R52) × F5) < 0; Where, R41 represents the curvature radius of the object side surface of the fourth lens, R42 represents the curvature radius of the image side surface of the fourth lens, F4 represents the focal length of the fourth lens, R51 represents the curvature radius of the object side surface of the fifth lens, R52 represents the curvature radius of the image side surface of the fifth lens, and F5 represents the focal length of the fifth lens.

9. The fixed-focus lens according to claim 1, wherein: The optical total length TTL of the fixed-focus lens < 11.5 mm.

10. The fixed-focus lens according to claim 1, wherein: It further includes a filter, and the filter is located between the fifth lens and the image plane.

Images