Short-wave infrared imaging lens

Abstract

The utility model discloses a short-wave infrared imaging lens, which relates to the field of optical equipment and sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side, the second lens is a meniscus cap lens with negative focal power; the third lens is a biconvex lens with positive focal power; the fourth lens is a biconcave lens with negative focal power; the fifth lens is a biconvex lens with positive focal power; the sixth lens is a biconcave lens with negative focal power; the seventh lens is a biconvex lens with positive focal power; and the eighth lens is a plano-convex lens with positive focal power. According to the utility model, by reasonably controlling the positive and negative matching of the focal power of each lens of the lens, the focal power of the lenses is distributed to be positive-negative-positive-negative-positive-negative-positive-positive-positive, the staggered distribution of the positive and negative focal powers can effectively balance the low-order aberration of the lens, and the tolerance sensitivity of the lens can be reduced at the same time; the imaging quality of the lens is ensured while the lens is kept miniaturized.

Description

Technical Field

[0001] This utility model relates to the field of optical equipment, specifically a short-wave infrared imaging lens. Background Technology

[0002] The existing shortwave infrared imaging lenses have complex optical composition and complex optical lens processing technology, and have at least one of the following defects: (1) low light transmission, low imaging quality in low light environment, which cannot meet the lens resolution requirements; (2) large lens distortion, which will produce pincushion or barrel distortion that is difficult to eliminate, which is not conducive to the detection of special scenes; (3) the lens uses expensive optical materials, resulting in high lens production cost. Summary of the Invention

[0003] The purpose of this invention is to provide a short-wave infrared imaging lens, which aims to overcome the problems existing in the prior art.

[0004] To achieve this objective, the present invention provides the following technical solution:

[0005] A shortwave infrared imaging lens, comprising, from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture, a sixth lens, a seventh lens, an eighth lens, and a protective sheet;

[0006] The first lens has a positive refractive index, with a convex object-side surface and a concave image-side surface;

[0007] The second lens has a negative refractive index, with a convex object-side surface and a concave image-side surface;

[0008] The third lens has a positive refractive index, and the object side and the image side are both convex.

[0009] The fourth lens has a negative refractive index, and the object side is concave, as is the image side.

[0010] The fifth lens has a positive refractive index, and the object side and the image side are both convex.

[0011] The sixth lens has a negative refractive index, and the object side is concave, as is the image side.

[0012] The seventh lens has a positive refractive index, and the object side and the image side are both convex.

[0013] The eighth lens has a positive refractive index, with a convex object side and a flat image side.

[0014] By rationally controlling the positive and negative combinations of the optical power of each lens, the optical power of the lens is distributed in the pattern of positive-negative-positive-negative-positive-negative-positive-positive. This staggered distribution of positive and negative optical power can effectively balance the lower-order aberrations of the lens, while reducing the sensitivity of the lens to tolerances, maintaining the miniaturization of the lens while ensuring the image quality of the lens.

[0015] Furthermore, the first lens is a meniscus lens with positive optical power and satisfies the following conditions: Nd1>1.9 Vd2<40; where Nd1 is the refractive index of the first lens and Vd1 is the Abbe coefficient of the first lens.

[0016] The use of a high refractive index and high dispersion (i.e., low Abbe coefficient) material for the first lens can ensure a large optical aperture ratio, which is beneficial for compressing the front aperture of the optical system to achieve lens miniaturization.

[0017] Furthermore, the second lens is a meniscus lens with negative optical power, and satisfies the following conditions: Nd2>1.75, Vd2<45; where Nd2 is the refractive index of the second lens and Vd2 is the Abbe coefficient of the second lens.

[0018] The second lens is made of a material with high refractive index and high dispersion (i.e., low Abbe coefficient), which can make the incident angle of the edge field rays on the subsequent optical elements smaller, realize a large field of view imaging range, make the optical system structure compact and small in size, which is very beneficial to reduce the space occupied by the entire optical system.

[0019] Furthermore, the third lens satisfies the following conditions: Nd3 > 1.8, Vd3 < 25; where Nd3 is the refractive index of the third lens and Vd3 is the Abbe coefficient of the third lens.

[0020] The third lens is made of high-refractive-index, high-dispersion (i.e., low Abbe coefficient) glass material. Combined with the ability to guide light convergence with positive optical power, it can help distribute the negative optical power of the second lens, reduce the sensitivity of the main optical lens at large angles, and improve the lens assembly yield.

[0021] Furthermore, the fourth lens satisfies the following condition: 1.45 <Nd4<1.55,Vd4> 70; where Nd4 is the refractive index of the fourth lens and Vd4 is the Abbe coefficient of the fourth lens.

[0022] The fourth lens is made of low-refractive-index, low-dispersion (i.e., high Abbe coefficient) glass material, which can effectively distribute the optical power of the lens to achieve a smooth bottom aperture.

[0023] Furthermore, the fifth lens satisfies the following conditions: Nd5 > 1.8, 40 <vd5>50; where, Nd5 is the refractive index of the fifth lens, and Vd5 is the Abbe number of the fifth lens.

[0024] The fifth lens uses a material with a high refractive index and high dispersion (i.e., a low Abbe number), and is combined with a positive focal length lens used in front of the aperture stop, which can increase the light passing ability of the lens and bring excellent low-light resolution ability.

[0025] Furthermore, the sixth lens satisfies the following conditions: Nd6 > 1.9, 40 < Vd6 < 20; where, Nd6 is the refractive index of the sixth lens, and Vd6 is the Abbe number of the sixth lens.

[0026] The sixth lens with a negative focal length has a high dispersion (i.e., a low Abbe number), and the seventh lens with a positive focal length has a low dispersion (i.e., a high Abbe number). Such a combination can play a role in correcting primary chromatic aberration, making the foci of the long wavelength of 1700 nm and the short wavelength of 900 nm that are cut off coincide on the optical axis. Such an idea is extremely beneficial to the design of a wide-spectrum composite light lens.

[0027] Furthermore, the seventh lens satisfies the following conditions: Nd7 < 1.6, Vd7 > 65, and Vd7 - Vd6 > 45; where, Nd7 is the refractive index of the seventh lens, and Vd7 is the Abbe number of the seventh lens.

[0028] While the sixth lens and the seventh lens play a role in correcting chromatic aberration in the optical system, in terms of shape, they form an edge-contact type double lens combination. There is an appropriate air gap between the positive and negative double lenses, and the refractive indices form a "high - low - high" layout. When light passes through such a region, strong refraction occurs in the air gap. However, since the radii of the two lens surfaces are relatively close and one is positive and the other is negative, most of the spherical aberration will be cancelled out. At the same time, due to different light height differences, the spherical aberration will not be completely cancelled out. It is this part of the spherical aberration difference that has a good compensation effect on the higher-order spherical aberration and can reduce the higher-order spherical aberration.

[0029] Furthermore, the eighth lens satisfies the following conditions: 1.7 < Nd8 < 1.8; 40 < Vd8 < 50; where, Nd8 is the refractive index of the eighth lens, and Vd8 is the Abbe number of the eighth lens.

[0030] The eighth lens uses a material with a high refractive index and high dispersion (i.e., a low Abbe number). This strategy can not only optimize the optical performance of the lens and improve the imaging resolution, but also effectively reduce the outer diameter size of the rear end of the lens.

[0031] The utility model has the following beneficial effects compared with the prior art:

[0032] By rationally controlling the positive and negative combinations of the optical power of each lens element, the lens optical power is distributed in a positive-negative-positive-negative-positive-negative-positive-positive pattern. This staggered distribution of positive and negative optical power effectively balances the lens's lower-order aberrations while reducing tolerance sensitivity, maintaining image quality while keeping the lens compact. Combined with specific parameter design, the lens achieves a compact design and image-side telecentricity while maintaining high optical performance. This is of great significance for improving system integration, portability, and specialized testing capabilities. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the optical path in the first embodiment of this utility model.

[0034] Figure 2 This is the MTF diagram of the first embodiment of the present invention at 900-1700nm.

[0035] Figure 3 This is a distortion diagram of the first embodiment of this invention in the 900-1700nm range. In the diagram, the left side shows the field curvature of the narrow beam, and the right side shows the distortion curve.

[0036] Figure 4 This is a relative illuminance diagram at 1300nm for the first embodiment of this utility model.

[0037] Figure 5 This is a schematic diagram of the optical path in the second embodiment of this utility model.

[0038] Figure 6 This is the MTF diagram of the second embodiment of the present invention at 900-1700nm.

[0039] Figure 7 This is a distortion diagram of the second embodiment of this invention in the 900-1700nm range. In the diagram, the left side shows the field curvature of the narrow beam, and the right side shows the distortion curve.

[0040] Figure 8 This is a relative illuminance diagram at 1300nm for the second embodiment of this utility model.

[0041] Figure 9 This is a schematic diagram of the optical path in the third embodiment of this utility model.

[0042] Figure 10 This is the MTF diagram of the third embodiment of the present invention at 900-1700nm.

[0043] Figure 11 This is a distortion diagram of the third embodiment of this invention in the 900-1700nm range. In the diagram, the left side shows the field curvature of the narrow beam, and the right side shows the distortion curve.

[0044] Figure 12 This is a relative illuminance diagram at 1300nm for the third embodiment of this utility model. Detailed Implementation

[0045] The specific embodiments of this utility model are described below with reference to the accompanying drawings. Many details are described below to provide a comprehensive understanding of this utility model; however, those skilled in the art can implement this utility model without these details.

[0046] like Figure 1 , Figure 5 and Figure 9 As shown, a shortwave infrared imaging lens comprises, from the object side to the image side, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, an aperture 6, a sixth lens 7, a seventh lens 8, an eighth lens 9, and a protective sheet 10.

[0047] like Figure 1 As shown, the first lens 1 has a positive refractive index, with the object side being convex and the image side being concave.

[0048] Specifically, the first lens 1 is a meniscus lens with positive optical power and a crescent shape. Furthermore, the first lens 1 satisfies the following conditions: Nd1 > 1.9, Vd2 < 40; where Nd1 is the refractive index of the first lens, and Vd1 is the Abbe coefficient of the first lens. The use of a high refractive index and high dispersion (i.e., low Abbe coefficient) material ensures a large optical aperture ratio, which is beneficial for reducing the front aperture of the optical system and thus achieving lens miniaturization.

[0049] Furthermore, the first lens 1, as the first glass lens of the optical lens, is made of H-ZLAF4LB (impact strength 2.72 (KJ / m*2), hardness 707 HK (10*7Pa) and H-ZLAF72 (impact strength 2.82 (KJ / m*2), hardness 663 HK (10*7Pa). As the first glass lens of the optical lens, the first lens 1 is exposed to air for extended periods. Therefore, during the optical design phase, it is necessary to consider improving the system's reliability and dependability, requiring it to meet certain hardness and drop test requirements, such as those involving falling gravel. Thus, the first lens 1 is made of glass material with excellent mechanical properties and chemical stability.

[0050] like Figure 1 As shown, the second lens 2 has a negative refractive index, with the object side being convex and the image side being concave.

[0051] Specifically, the second lens 2 is a meniscus lens with negative optical power and satisfies the following conditions: Nd2>1.75, Vd2<45; where Nd2 is the refractive index of the second lens and Vd2 is the Abbe coefficient of the second lens.

[0052] The second lens 2 is made of a material with high refractive index and high dispersion (i.e., low Abbe coefficient), which can make the incident angle of the edge field rays on the subsequent optical elements smaller, realize a large field of view imaging range, make the optical system structure compact and small in size, which is very beneficial to reduce the space occupied by the entire optical system.

[0053] like Figure 1 As shown, the third lens 3 has a positive refractive index, and the object side and the image side are both convex.

[0054] Specifically, the third lens 3 is a biconvex lens with positive optical power and satisfies the following conditions: Nd3>1.8, Vd3<25; where Nd3 is the refractive index of the third lens and Vd3 is the Abbe coefficient of the third lens.

[0055] The third lens 3 is made of high refractive index and high dispersion (i.e., low Abbe coefficient) glass material. Combined with the ability to guide light convergence with positive optical power, it can help distribute the negative optical power of the second lens, reduce the sensitivity of the main optical lens at large angles, and improve the lens assembly yield.

[0056] like Figure 1 As shown, the fourth lens 4 has a negative refractive index, and the object side is concave, as is the image side.

[0057] Specifically, the fourth lens 4 is a biconcave lens with negative optical power, and satisfies the following condition: 1.45 <Nd4<1.55,Vd4> 70; where Nd4 is the refractive index of the fourth lens and Vd4 is the Abbe coefficient of the fourth lens.

[0058] The fourth lens 4 is made of glass material with low refractive index and low dispersion (i.e., high Abbe coefficient), which can effectively distribute the optical power of the lens to achieve a smooth bottom aperture.

[0059] like Figure 1 As shown, the fifth lens 5 has a positive refractive index, and the object side and the image side are both convex.

[0060] The fifth lens, 5, is a biconvex lens with positive optical power and satisfies the following conditions: Nd5 > 1.8, 40 <vd5>50; where, Nd5 is the refractive index of the fifth lens, and Vd5 is the Abbe number of the fifth lens.

[0061] The fifth lens 5 uses a material with a high refractive index and high dispersion (i.e., low Abbe number), and is combined with a positive focal length lens used before the aperture stop, which can increase the light passing ability of the lens and bring excellent low-light resolution ability.

[0062] As Figure 1 shown, the sixth lens 7 has a negative refractive power, the object side is concave, and the image side is concave. The seventh lens 8 has a positive refractive power, the object side is convex, and the image side is convex.

[0063] Specifically, the sixth lens 7 is a biconcave lens with a negative focal power and satisfies the following conditions: Nd6 > 1.9, 40 < Vd6 < 20; where, Nd6 is the refractive index of the sixth lens, and Vd6 is the Abbe number of the sixth lens. The seventh lens 8 is a biconvex lens with a positive focal power and satisfies the following conditions: Nd7 < 1.6, Vd7 > 65, and Vd7 - Vd6 > 45; where, Nd7 is the refractive index of the seventh lens, and Vd7 is the Abbe number of the seventh lens.

[0064] The sixth lens 7 with a negative focal length has a high dispersion (i.e., a low Abbe number) and the seventh lens 8 with a positive focal length has a low dispersion (i.e., a high Abbe number). Such a combination can play a role in correcting primary chromatic aberration, making the foci of the long wavelength of 1700 nm and the short wavelength of 900 nm on the optical axis coincide. Such an idea is extremely beneficial to the design of a wide-spectrum compound light lens.

[0065] While the sixth lens 7 and the seventh lens 8 play a role in achromatism in the optical system, in terms of shape, they form an edge-contact type doublet lens combination. There is an appropriate air gap between the positive and negative doublet lenses, and the refractive indices form a "high - low - high" layout. When light passes through such a region, strong refraction occurs in the air gap. However, since the radii of the two lens surfaces are relatively close and one is positive and the other is negative, most of the spherical aberration will be canceled out. At the same time, due to the different ray height differences, the spherical aberration will not be completely canceled out. It is this part of the spherical aberration difference that has a good compensation effect on the higher-order spherical aberration, which can reduce the higher-order spherical aberration somewhat.

[0066] As Figure 1 shown, the eighth lens 9 has a positive refractive power, the object side is convex, and the image side is flat.

[0067] Specifically, the eighth lens 9 is a plano-convex lens with a positive focal power and satisfies the following conditions: 1.7 < Nd8 < 1.8; 40 < Vd8 < 50; where, Nd8 is the refractive index of the eighth lens, and Vd8 is the Abbe number of the eighth lens.

[0068] The eighth lens 9 is made of a material with high refractive index and high dispersion (i.e., low Abbe number). This strategy not only optimizes the optical performance of the lens and improves the imaging resolution, but also enables an effective reduction in the outer diameter of the lens's rear end.

[0069] Detailed optical data for three embodiments of this utility model are provided. The lens parameters for the three embodiments are as follows:

[0070]

[0071] First Embodiment

[0072] Table 1. Detailed optical data of the first embodiment

[0073]

[0074] In the first embodiment, the optical system has a focal length f=11.8mm, a light transmission FNO=2, a field of view FOV=46.3°, a target surface size IMH=10mm, and a total optical length TTL=50mm.

[0075] like Figure 2 As shown, it can be seen that the MTF value of the first embodiment at 900-1700nm is greater than 0.6 at 37LP / mm, indicating that the embodiment has high resolution and good imaging quality under short-wave infrared light.

[0076] like Figure 3 As shown, it can be seen that in the first embodiment, the edge field distortion values ​​are all less than ±3% in the range of 900-1700nm, the optical distortion is small, the imaging effect is good, and the imaging fidelity is high.

[0077] like Figure 4 As shown, it can be seen that in the first embodiment, at 1300nm, the lens maintains a relative illumination greater than 85% while ensuring a field of view (FOV) of 23.15°, resulting in good image quality.

[0078] Second Embodiment

[0079] Table 2. Detailed optical data for the second embodiment

[0080]

[0081] In the second embodiment, the optical system has a focal length f=11.8mm, a light transmission FNO=2, a field of view FOV=46.3°, a target surface size IMH=10mm, and a total optical length TTL=50mm.

[0082] like Figure 6 As shown, it can be seen that the MTF value of the second embodiment at 900-1700nm is greater than 0.5 at 33.3LP / mm, indicating that this embodiment has high resolution and good imaging quality under short-wave infrared light.

[0083] like Figure 7 As shown, it can be seen that in the second embodiment, the edge field distortion values ​​are all less than ±0.6% in the 900-1700nm range, the optical distortion is very small, the imaging effect is good, and the imaging fidelity is high.

[0084] like Figure 8 As shown, it can be seen that in the second embodiment, at 1300nm, the lens maintains a relative illumination greater than 85% while ensuring a field of view (FOV) of 23.15°, resulting in good image quality.

[0085] Third Embodiment

[0086] Table 3. Detailed optical data for the third embodiment

[0087]

[0088] In the third embodiment, the optical system has a focal length f=11.8mm, a light transmission FNO=2, a field of view FOV=46.3°, a target surface size IMH=10mm, and a total optical length TTL=50mm.

[0089] like Figure 10 As shown, it can be seen that the MTF value of the third embodiment at 900-1700nm is greater than 0.5 at 37LP / mm, indicating that this embodiment has high resolution and good imaging quality under short-wave infrared light.

[0090] like Figure 11 As shown, it can be seen that in the third embodiment, the edge field distortion values ​​are all less than ±1% in the range of 900-1700nm, the optical distortion is small, the imaging effect is good, and the imaging fidelity is high.

[0091] like Figure 12 As shown, it can be seen that in the third embodiment, at 1300nm, the lens maintains a relative illumination greater than 95% while ensuring a field of view (FOV) of 23.15°, resulting in good image quality.

[0092] This is merely a specific embodiment of the present utility model, but the design concept of the present utility model is not limited thereto. Any non-substantial modifications made to the present utility model using this concept shall be considered as an infringement of the protection scope of the present utility model.

Claims

1. A shortwave infrared imaging lens, characterized in that: From the object side to the image side, there are, in sequence, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture stop, a sixth lens, a seventh lens, and an eighth lens; The first lens has a positive refractive power, with a convex object side and a concave image side; The second lens has a negative refractive power, with a convex object side and a concave image side; The third lens has a positive refractive power, with a convex object side and a convex image side; The fourth lens has a negative refractive power, with a concave object side and a concave image side; The fifth lens has a positive refractive power, with a convex object side and a convex image side; The sixth lens has a negative refractive power, with a concave object side and a concave image side; The seventh lens has a positive refractive power, with a convex object side and a convex image side; The eighth lens has a positive refractive power, with a convex object side and a flat image side.

2. The shortwave infrared imaging lens according to claim 1, characterized in that: The first lens is a meniscus lens with a positive focal power and satisfies the following conditions: Nd1 > 1.9, Vd2 < 40; where Nd1 is the refractive index of the first lens and Vd1 is the Abbe number of the first lens.

3. A shortwave infrared imaging lens according to claim 1, characterized in that: The second lens is a meniscus lens with a negative focal power and satisfies the following conditions: Nd2 > 1.75, Vd2 < 45; where Nd2 is the refractive index of the second lens and Vd2 is the Abbe number of the second lens.

4. A shortwave infrared imaging lens according to claim 3, characterized in that: The third lens satisfies the following conditions: Nd3 > 1.8, Vd3 < 25; where Nd3 is the refractive index of the third lens and Vd3 is the Abbe number of the third lens.

5. A shortwave infrared imaging lens according to claim 1, characterized in that: The fourth lens satisfies the following conditions: 1.45 < Nd4 < 1.55, Vd4 > 70; where Nd4 is the refractive index of the fourth lens and Vd4 is the Abbe number of the fourth lens.

6. A shortwave infrared imaging lens according to claim 1, characterized in that: The fifth lens satisfies the following conditions: Nd5 > 1.8, 40 <vd5>50; where Nd5 is the refractive index of the fifth lens and Vd5 is the Abbe number of the fifth lens.< / vd5> 7. A shortwave infrared imaging lens according to claim 1, characterized in that: The sixth lens satisfies the following conditions: Nd6 > 1.9, 40 < Vd6 < 20; where Nd6 is the refractive index of the sixth lens and Vd6 is the Abbe number of the sixth lens.

8. A shortwave infrared imaging lens according to claim 7, characterized in that: The seventh lens satisfies the following conditions: Nd7 < 1.6, Vd7 > 65, and Vd7 - Vd6 > 45; where Nd7 is the refractive index of the seventh lens and Vd7 is the Abbe number of the seventh lens.

9. A shortwave infrared imaging lens according to claim 8, characterized in that: The sixth lens and the seventh lens form an edge-contact doublet lens group.

10. A shortwave infrared imaging lens according to claim 1, characterized in that: The eighth lens satisfies the following conditions: 1.7 < Nd8 < 1.8; 40 < Vd8 < 50; where Nd8 is the refractive index of the eighth lens and Vd8 is the Abbe number of the eighth lens.

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