A glass-plastic hybrid lens resistant to high and low temperatures

Abstract

The present invention discloses a high - cost - performance glass - plastic hybrid lens capable of withstanding high and low temperatures, which sequentially includes, from the object side to the image side along the lens optical axis: a first lens, which is a plastic aspherical lens and has a negative optical power; a second lens, which is a glass spherical lens and has a positive optical power; a third lens, which is a plastic aspherical lens and has a positive optical power; a fourth lens, which is a plastic aspherical lens and has a negative optical power; an aperture stop, which is arranged between the first lens and the second lens; an infrared filter, which is arranged on the side of the fourth lens away from the third lens and is used for filtering infrared light; and an image acquisition element, which is arranged on the side of the infrared filter away from the fourth lens and is used for providing an image of the object to be photographed. Through the above lens configuration method, the present invention can effectively shorten the total length of the lens, reduce the system sensitivity, achieve no defocusing at high temperature of +80 °C and low temperature of -40 °C, and obtain good imaging quality.

Description

Technical Field

[0001] The present invention relates to the technical field of lenses, and specifically to a plastic-glass hybrid lens that can withstand high and low temperatures. Background Art

[0002] With the progress of technology, lenses, as the "eyes" of humans, play an increasingly important role in machine vision, artificial intelligence, criminal investigation monitoring, driverless driving, etc. In the field of video surveillance, such as road surveillance, community surveillance, square surveillance, etc., due to the harsh outdoor use environment, most lenses still use optical system lenses with all-glass lens structures. For example, patents such as patent numbers CN 201464695 U and CN 103513400 A result in high lens costs.

[0003] However, some plastic-glass hybrid lenses disclosed in the prior art, such as the one with patent number CN 205679846 U, have further reduced the overall length of the lens to a certain extent. They use plastic-glass hybrid materials to make lenses, avoiding the use of materials with high refractive indices and high prices, and reducing the lens cost. However, the actual high and low temperature resistance performance does not reach the best effect. Summary of the Invention

[0004] The purpose of the present invention is to provide a plastic-glass hybrid lens that can withstand high and low temperatures to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A plastic-glass hybrid lens that can withstand high and low temperatures. The hybrid lens has 4 lens elements, and in order from the object side to the image side along the lens optical axis:

[0007] The first lens is a plastic aspherical lens and has a negative optical power;

[0008] The second lens is a glass spherical lens and has a positive optical power;

[0009] The third lens is a plastic aspherical lens and has a positive optical power;

[0010] The fourth lens is a plastic aspherical lens and has a negative optical power;

[0011] The aperture stop is arranged between the first lens and the second lens;

[0012] The infrared filter is arranged on the side of the fourth lens away from the third lens for filtering infrared light;

[0013] The image acquisition element is arranged on the side of the infrared filter away from the fourth lens for providing an image of the object to be photographed;

[0014] The focal lengths of the first lens, the second lens, the third lens, and the fourth lens are f1, f2, f2, and f4 respectively, and the refractive indices of the first lens, the second lens, the third lens, and the fourth lens are ND1, ND2, ND3, and ND4 respectively, satisfying the following conditions:

[0015] f1 ranges from -7.67 to -6.987, f2 ranges from +8.638 to +10.553, f3 ranges from +3.521 to +4.556, and f4 ranges from -5.87 to -4.825;

[0016] ND1 ranges from 1.51 to 1.58, ND2 ranges from 1.58 to 1.71, ND3 ranges from 1.51 to 1.58, and ND4 ranges from 1.62 to 1.72.

[0017] Furthermore, the two sides of the first lens are the object side surface of the first lens and the image side surface of the first lens respectively. Both the object side surface of the first lens and the image side surface of the first lens are aspherical surfaces. The object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface. The curvature radii of the object side surface of the first lens and the image side surface of the first lens are R11 and R12 respectively. R11 ranges from +6.627 to +7.294, and R12 ranges from +2.25 to +9.678.

[0018] Furthermore, the two sides of the second lens are the object side surface of the second lens and the image side surface of the second lens respectively. Both the object side surface of the second lens and the image side surface of the second lens are spherical surfaces. Both the object side surface of the second lens and the image side surface of the second lens are convex surfaces. The curvature radii of the object side surface of the second lens and the image side surface of the second lens are R21 and R22 respectively. R21 ranges from +10.012 to +32.62, and R22 ranges from -32.62 to -10.012.

[0019] Furthermore, the absolute values of the R values of the object side surface of the second lens and the image side surface of the second lens are the same.

[0020] Furthermore, the two sides of the third lens are the object side surface of the third lens and the image side surface of the third lens respectively. Both the object side surface of the third lens and the image side surface of the third lens are aspherical surfaces. Both the object side surface of the third lens and the image side surface of the third lens are convex surfaces. The curvature radii of the object side surface of the third lens and the image side surface of the third lens are R31 and R32 respectively. R31 ranges from +5.3 to +6.12, and R32 ranges from -3.594 to -1.902.

[0021] Furthermore, the two sides of the fourth lens are respectively the object side of the fourth lens and the image side of the fourth lens. Both the object side of the fourth lens and the image side of the fourth lens are aspherical surfaces. The object side of the fourth lens is a concave surface, and the image side of the fourth lens is a convex surface. The radii of curvature of the object side of the fourth lens and the image side of the fourth lens are R41 and R42 respectively, where R41 ranges from -3.514 to -1.902, and R42 ranges from -58.559 to -5.707.

[0022] Furthermore, the first lens, the second lens, the third lens, and the fourth lens satisfy the following conditions:

[0023] 1.18 < OBFL / EFL < 1.72, 0.05 < AC3 < 0.23, 0.14 < CRA / 2ω < 0.19;

[0024] In the formula, the focal length of the overall optical system is EFL; the distance from the closest point of the curved surface of the fourth lens to the image acquisition element (8) to the image plane is OBFL; the field angle of this lens system is 2ω, the principal ray incident angle is CRA, and AC3 is the distance between the third lens and the fourth lens in the optical axis direction.

[0025] Furthermore, the first lens, the second lens, the third lens, and the fourth lens all satisfy the equation of the even-order aspherical surface:

[0026]

[0027] In the formula, K is the conic coefficient of the quadratic surface, r is the lens height, C is the conic coefficient at the vertex of the aspherical surface, A4, A6, A8... are the fourth-order, sixth-order, eighth-order... aspherical coefficients of the aspherical surface respectively, and Z is the equation of the even-order aspherical surface.

[0028] Furthermore, a protective glass is integrally provided on the surface of the image acquisition element.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: Through the above lens configuration method, the present invention can effectively shorten the total length of the lens, reduce the system sensitivity, achieve no defocusing at high temperature +80°C and low temperature -40°C, and obtain good imaging quality; the four-piece combination also has low sensitivity, which can also improve the yield during the processing process and thus reduce the large amount of loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the present invention.

[0031] Figure 2 It is a schematic diagram of the light passing through in the present invention.

[0032] In the figure: 1 - first lens, 11 - object side surface of the first lens, 12 - image side surface of the first lens, 2 - second lens, 21 - object side surface of the second lens, 22 - image side surface of the second lens, 3 - third lens, 31 - object side surface of the third lens, 32 - image side surface of the third lens, 4 - fourth lens, 41 - object side surface of the fourth lens, 42 - image side surface of the fourth lens, 5 - aperture stop, 6 - filter, 7 - protective glass, 8 - image acquisition element. Specific embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to Figure 1-2 , in the embodiment of the present invention, a glass-plastic hybrid lens capable of withstanding high and low temperatures, the hybrid lens has 4 lens elements, and sequentially includes from the object side to the image side along the optical axis of the lens: a plastic aspherical first lens 1 with a negative optical power; a glass spherical second lens 2 with a positive optical power; a plastic aspherical third lens 3 with a positive optical power; a plastic aspherical fourth lens 4 with a negative optical power; an aperture stop 5 between the first lens 1 and the second lens 2.

[0035] The two sides of the first lens 1 are respectively the object side surface 11 of the first lens and the image side surface 12 of the first lens. Both the object side surface 11 of the first lens and the image side surface 12 of the first lens are aspherical surfaces, and the object side surface 11 of the first lens is a convex surface, and the image side surface 12 of the first lens is a concave surface. The first lens 1 can be made of a plastic material with a refractive index ND1 lower than 1.58.

[0036] The two sides of the second lens 2 are respectively the object side surface 21 of the second lens and the image side surface 22 of the second lens. Both the object side surface 21 of the second lens and the image side surface 22 of the second lens are spherical surfaces. Both the object side surface 21 of the second lens and the image side surface 22 of the second lens are convex surfaces, and the absolute values of the R values of the object side surface 21 of the second lens and the image side surface 22 of the second lens can be the same. The second lens 2 can be made of a glass material with a refractive index 1.58 < ND2 < 1.71. The combination of the negative and positive optical powers of the first lens 1 and the second lens 2 is beneficial to increasing the light transmission aperture and better reducing the system sensitivity.

[0037] On both sides of the third lens 3 are respectively a third lens object side 31 and a third lens image side 32, and both the third lens object side 31 and the third lens image side 32 are aspherical surfaces. Both the third lens object side (31) and the third lens image side (32) are convex surfaces. This bending method can make light converge better to improve the resolution sharpness and is beneficial to suppressing the purple fringing phenomenon in actual shooting. The third lens 3 can be made of a plastic material with a refractive index ND3 lower than 1.58.

[0038] On both sides of the fourth lens 4 are respectively a fourth lens object side 41 and a fourth lens image side 42. Both the fourth lens object side 41 and the fourth lens image side 42 are aspherical surfaces. Moreover, the fourth lens object side 41 is a concave surface and the fourth lens image side 42 is a convex surface. This combination of positive and negative optical powers of the third lens 3 and the fourth lens 4 can greatly improve the imaging quality of the lens. The fourth lens 4 can be made of a plastic material with a refractive index ND4 lower than 1.72. Therefore, the first lens 1, the third lens 3, and the fourth lens 4 can use the same plastic material, which can better save the material cost in the processing process.

[0039] The first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 all satisfy the equation of an even-order aspherical surface:

[0040]

[0041] In the formula, K is the conic coefficient of the quadric surface, r is the lens height, C is the conic coefficient at the vertex of the aspherical surface, A4, A6, A8... are respectively the fourth-order, sixth-order, eighth-order... aspherical coefficients of the aspherical surface, and Z is the equation of the even-order aspherical surface.

[0042] The focal lengths of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are respectively f1, f2, f2, and f4. The refractive indices of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are respectively ND1, ND2, ND3, and ND4. The radii of curvature of the first lens object side 11 and the first lens image side 12 are respectively R11 and R12. The radii of curvature of the second lens object side 21 and the second lens image side 22 are respectively R21 and R22. The radii of curvature of the third lens object side 31 and the third lens image side 32 are respectively R31 and R32. The radii of curvature of the fourth lens object side 41 and the fourth lens image side 42 are respectively R41 and R42, and they respectively satisfy the following conditions:

[0043] f1 -7.67～-6.987 ND1 1.51～1.58 R11 +6.627～+7.294 R12 +2.25～+9.678 f2 +8.638～+10.553 ND2 1.58～1.71 R21 +10.012～+32.62 R22 -32.62～-10.012 f3 +3.521～+4.556 ND3 1.51～1.58 R31 +5.3～+6.12 R32 -3.594～-1.902 f4 -5.87～+-4.825 ND4 1.62～1.72 R41 -3.514～-1.902 R42 -58.559～-5.707

[0044] In the above table, the "-" sign indicates a negative direction.

[0045] The aperture stop 5 is centered within the aperture, i.e., it is disposed between the first lens 1 and the second lens 2, and can be realized by a spacer ring during mechanism design.

[0046] An infrared filter 6 is disposed on the side of the fourth lens 4 away from the third lens 3. The infrared filter 6 is abbreviated as IR in English. The infrared filter 6 can be made of Schott-BK7 glass, and a film layer that can cut off infrared light is coated on the surface of the infrared filter 6. There is already an infrared filter cut-off film in the prior art, so it will not be elaborated here.

[0047] An image acquisition element 8 is disposed on the side of the infrared filter 6 away from the fourth lens 4. The image acquisition element 8 is an image sensor (image sensing chip), and the image acquisition element 8 includes a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor), which can convert an image signal into an electronic signal for output to provide imaging of the object to be photographed.

[0048] A protective glass 7 is integrally disposed on the image acquisition element 8, and the protective glass 7 can be used to protect the imaging surface.

[0049] For a glass-plastic hybrid lens capable of withstanding high and low temperatures according to the present invention, after the curvature radius (R i ), surface shape, lens thickness (d i ), and air gap on the optical axis (d i ) of each lens are combined, it has good optical aberration correction, and makes the length condition, field of view angle, and back focal relationship of a glass-plastic hybrid lens capable of withstanding high and low temperatures satisfy the formulas: 0.19 < BFL / TTL < 0.23, 1.5 < TTL / y < 1.6, 1.0 < EFL / f1 < 1.14, 1.2 < TTL / EFL < 1.5 (wherein, the focal length of the overall optical system is EFL, the total length of the optical system is TTL, the image height of the optical system is y, the back focal length is BFL, and the focal length of the first lens is f1), and the units of the above relational formulas are all mm.

[0050] Considering the current technological level of precision instrument processing, the manufacturing and processing of aspherical lenses have been very mature. In order to obtain better imaging quality, the lens of the present invention is composed of three plastic aspherical lenses and one glass spherical lens, and has a larger field of view angle. In order to save costs, the material problem was considered at the initial stage of design, so the present invention can also reduce costs.

[0051] The following Table (1) respectively lists the optical surface numbers (Surface Number) in sequence from the object side to the image side, and the curvature radius R of each optical surface on the optical axis i(Unit: mm) (Radius of Curvature R), refractive index (ND) of each lens, and aspheric K value (Conic) of each lens.

[0052] Table 1

[0053]

[0054]

[0055] In Table 1, the optical surfaces (Surface) marked with "*" are aspheric optical surfaces. R11 and R12 represent the object side 11 and the image side 12 of the first lens respectively; R21 and R22 represent the object side 21 and the image side 22 of the second lens respectively; R31 and R32 represent the object side 31 and the image side 32 of the third lens respectively; R41 and R42 represent the object side and the image side of the fourth lens respectively. Fno is the focal length entrance pupil ratio (F number) of the optical lens, EFL is the effective focal length of the imaging lens, and 2ω is the field of view angle of a glass-plastic hybrid lens that can withstand high and low temperatures.

[0056] The following Table 2 lists the coefficients of the aspheric surfaces of each optical surface:

[0057] Table 2

[0058] A4 A6 A8 A10 A12 A14 A16 R11 -2.97E-03 4.78E-05 2.52E-06 -1.03E-07 -2.57E-09 2.14E-10 -3.44E-12 R12 8.72E-03 -5.36E-04 -7.11E-05 3.17E-05 -4.42E-06 3.08E-07 -8.74E-09 R31 -1.81E-03 -1.72E-04 -1.00E-04 2.53E-05 -4.71E-06 -1.16E-07 1.25E-08 R32 9.77E-04 -7.46E-06 1.04E-04 -1.77E-05 -2.61E-06 5.18E-08 2.75E-08 R41 2.53E-03 -2.78E-04 4.61E-05 1.50E-05 -1.24E-06 -8.44E-07 1.02E-07 R42 8.53E-03 -1.27E-04 -1.44E-04 3.01E-05 6.08E-07 -5.40E-07 2.86E-08

[0059] The effective focal length of a glass-plastic hybrid lens that can withstand high and low temperatures in this embodiment is 4.0 mm. Using plastic materials for the first lens 1, the third lens 3, and the fourth lens 4 is beneficial for reducing costs and can well achieve a larger image height. The total length of the lens is 22.5 mm, that is, it satisfies conditions such as 1.18 < OBFL / EFL < 1.72, 0.05 < AC3 < 0.23, and 0.14 < CRA / 2ω < 0.19.

[0060] In the relational expressions, the focal length of the overall optical system is EFL; the optical back focal length of the lens system is OBFL, that is, the distance from the closest point of the curved surface of the fourth lens 4 to the image acquisition element (8) to the image plane; the field of view angle of this lens system is 2ω, the principal ray incident angle is CRA, and AC3 is the distance between the third lens and the fourth lens in the optical axis direction (defined as positive from left to right).

[0061] Through the above lens configuration method, the present invention can effectively shorten the total length of the lens, reduce the system sensitivity, achieve no defocusing at high temperature +80 °C and low temperature -40 °C, and obtain good imaging quality. The present invention will be described below in conjunction with the accompanying drawings and embodiments.

[0062] From the above Table 1, Table 2 and Figure 1 、Figure 2 As shown, it can be proved that the shape of a glass-plastic hybrid lens with high and low temperature resistance according to the present invention is easy to process and produce, thereby improving the applicability of the present invention.

[0063] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. Those of ordinary skill in the art understand that many changes, modifications, and even equivalent transformations can be made within the spirit and scope defined by the claims of the present invention, and all of them will fall within the scope of the rights of the present invention.

[0064] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed invention.

[0065] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A glass-plastic hybrid lens resistant to high and low temperatures, characterized in that, The hybrid lens has 4 lens elements, and sequentially includes from the object side to the image side along the lens optical axis: The first lens (1), which is a plastic aspherical lens and has a negative optical power; The second lens (2), which is a glass spherical lens and has a positive optical power; The third lens (3), which is a plastic aspherical lens and has a positive optical power; The fourth lens (4), which is a plastic aspherical lens and has a negative optical power; The aperture stop (5) is disposed between the first lens (1) and the second lens (2); The infrared filter (6) is disposed on a side of the fourth lens (4) away from the third lens (3) for filtering infrared light; The image acquisition element (8) is disposed on a side of the infrared filter (6) away from the fourth lens (4) for providing imaging of an object to be photographed; The focal lengths of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are f1, f2, f2 and f4 respectively, and the refractive indices of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are ND1, ND2, ND3 and ND4 respectively, satisfying the following conditions: f1 ranges from -7.67 mm to -6.987 mm, f2 ranges from +8.638 mm to +10.553 mm, f3 ranges from +3.521 mm to +4.556 mm, f4 ranges from -5.87 mm to -4.825 mm; ND1 ranges from 1.51 to 1.58, ND2 ranges from 1.58 to 1.71, ND3 ranges from 1.51 to 1.58, ND4 ranges from 1.62 to 1.72; The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) satisfy the following conditions: 1.18 < OBFL / EFL < 1.72, 0.05 < AC3mm < 0.23, 0.14 < CRA / 2ω < 0.19; In the formula, the focal length of the overall optical system is EFL; the distance from the point on the surface of the fourth lens (4) closest to the image acquisition element (8) to the image plane is OBFL; the field angle of the lens system is 2ω, the chief ray angle of incidence is CRA, and AC3 is the distance between the third lens (3) and the fourth lens (4) in the optical axis direction; The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) all satisfy the equation of an even aspherical surface: In the formula, K is the conic coefficient of the quadratic surface, r is the lens height, C is the conic coefficient at the vertex of the aspherical surface, A4, A6, A8... are the aspherical coefficients of the fourth order, sixth order, eighth order... of the aspherical surface respectively, and Z is the equation of the even aspherical surface.

2. The glass-plastic hybrid lens capable of withstanding high and low temperatures according to claim 1, characterized in that, On both sides of the first lens (1) are the object side surface (11) of the first lens and the image side surface (12) of the first lens. Both the object side surface (11) of the first lens and the image side surface (12) of the first lens are aspherical surfaces. The object side surface (11) of the first lens is a convex surface, and the image side surface (12) of the first lens is a concave surface. The radii of curvature of the object side surface (11) of the first lens and the image side surface (12) of the first lens are R11 and R12 respectively, and R11 ranges from +6.627 to +7.294, and R12 ranges from +2.25 to +9.

678.

3. A glass-plastic hybrid lens capable of withstanding high and low temperatures according to claim 1, characterized in that, On both sides of the second lens (2) are a second lens object side (21) and a second lens image side (22) respectively. Both the second lens object side (21) and the second lens image side (22) are spherical surfaces. The second lens object side (21) and the second lens image side (22) are both convex surfaces. The radii of curvature of the second lens object side (21) and the second lens image side (22) are R21 and R22 respectively, where R21 ranges from +10.012 to +32.62 and R22 ranges from -32.62 to -10.

012.

4. A glass-plastic hybrid lens capable of withstanding high and low temperatures according to claim 3, characterized in that, The absolute values of the R values of the second lens object side (21) and the second lens image side (22) are the same.

5. A glass-plastic hybrid lens resistant to high and low temperatures according to claim 1, characterized in that, On both sides of the third lens (3) are a third lens object side (31) and a third lens image side (32) respectively. Both the third lens object side (31) and the third lens image side (32) are aspherical surfaces. The third lens object side (31) and the third lens image side (32) are both convex surfaces. The radii of curvature of the third lens object side (31) and the third lens image side (32) are R31 and R32 respectively, where R31 ranges from +5.3 to +6.12 and R32 ranges from -3.594 to -1.

902.

6. A glass-plastic hybrid lens capable of withstanding high and low temperatures according to claim 1, characterized in that, On both sides of the fourth lens (4) are a fourth lens object side (41) and a fourth lens image side (42) respectively. Both the fourth lens object side (41) and the fourth lens image side (42) are aspherical surfaces. The fourth lens object side (41) is a concave surface and the fourth lens image side (42) is a convex surface. The radii of curvature of the fourth lens object side (41) and the fourth lens image side (42) are R41 and R42 respectively, where R41 ranges from -3.514 to -1.902 and R42 ranges from -58.559 to -5.

707.

7. A glass-plastic hybrid lens capable of withstanding high and low temperatures according to claim 1, characterized in that A protective glass (7) is integrally provided on the surface of the image acquisition element (8).

Images