A near-infrared long-focus optical lens with a wavelength between 0.7um and 1um

Abstract

A near-infrared long-focus optical lens with a wavelength between 0.7 um and 1 um, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens coaxially arranged in sequence from the object side to the image side. A detector is arranged behind the sixth lens. Taking the object side to the image side as the reference direction, the first lens is a plano-convex positive lens, the front surface of the first lens is the convex surface of the lens, and the rear surface is a plane. The second lens is a biconvex positive lens. The third lens and the fourth lens form a doublet lens. The third lens is a convex-concave positive lens, and the fourth lens is a biconcave negative lens. The fifth lens is a biconvex positive lens. The sixth lens is a convex-concave positive lens, and the aperture stop is on the front surface of the second lens. The optical lens of the present invention has low processing cost, and has the advantages of short overall optical length, small volume, easy to carry, simple assembly and adjustment, and high image quality.

Description

Technical Field

[0001] The present invention belongs to the field of infrared detection, and relates to a near-infrared long-focus optical lens with a wavelength between 0.7um and 1um. Background Art

[0002] With the development of science and technology, infrared optical systems are widely used in civilian and military fields. Monitoring systems exist in many fields, such as civilian security systems, road traffic monitoring systems, military UAV optoelectronic pods, border monitoring systems, and so on. Commonly used infrared systems include zoom optical systems and fixed-focus optical systems. Among them, the zoom optical system can not only achieve long-focus high-resolution imaging but also achieve wide-field search imaging, but it has a complex structure and a high price. The fixed-focus lens can achieve long-focus high-resolution imaging, has a simple structure and a low price, and is therefore widely used in optoelectronic monitoring devices. At present, most of the short-wave infrared lenses used in China are improved from ordinary camera optical lenses, only adding infrared lenses in the camera lens, and some of the lenses are made of advanced optical glass such as aspherical lenses, which makes the price expensive and the structure complex, and is not conducive to large-scale production and use. Therefore, it is necessary to develop and design a short-wave infrared long-focus optical lens with fewer lenses, low cost, and simple assembly and adjustment. Summary of the Invention

[0003] The purpose of the present invention is to provide a near-infrared long-focus optical lens with a wavelength between 0.7um and 1um, aiming at the problems of complex structure, complex assembly and adjustment, and high cost of the short-wave infrared long-focus optical system in the above-mentioned prior art. The lens has the advantages of short overall optical length, small volume, easy to carry, simple assembly and adjustment, low cost, and high image quality, and is more suitable for assembling various aircraft optoelectronic pods.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A near-infrared long-focus optical lens with a wavelength between 0.7um and 1um, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens coaxially arranged in sequence from the object side to the image side, and a detector is arranged behind the sixth lens; taking the object side to the image side as the reference direction, the front surface S1 of the first lens is a convex surface, and the rear surface S2 of the first lens is a flat surface; the front surface S3 of the second lens is a convex surface, and the rear surface S4 of the second lens is a concave surface; the front surface S5 of the third lens is a convex surface, and the rear surface S6 of the third lens is a convex surface; the front surface S7 of the fourth lens is a concave surface, and the rear surface S8 of the fourth lens is a concave surface; the front surface S9 of the fifth lens is a convex surface, and the rear surface S10 of the fifth lens is a concave surface; the front surface S11 of the sixth lens is a concave surface, and the rear surface S12 of the sixth lens is a convex surface; an aperture stop is arranged on the front surface S3 of the second lens, and the third lens and the fourth lens form a doublet lens, the third lens is a positive lens and the fourth lens is a negative lens.

[0006] The focal length of the lens of the present invention is 300mm, the back focal length is 3.68mm, the optical F-number is 5, and the total length is 200mm.

[0007] As a preferred solution, the detector of the near-infrared long-focus optical lens of the present invention adopts a 1 / 8″, CMOS, 16:9 detector with a pixel size of 2um, the total optical length is 200mm, and the maximum aperture is 60mm.

[0008] As a preferred solution, the working wavelength of the near-infrared long-focus optical lens of the present invention is 0.7~1um; the average modulation transfer function value MTF of the full field of view reaches the diffraction limit at 250lp / mm.

[0009] As a preferred solution, the incident energy curves of each field of view of the lens are close to the diffraction limit, and the distortion is less than 0.05%.

[0010] As a preferred solution, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens of the present invention are all made of ordinary glass instead of high-grade optical glass. High-grade optical glass includes aspherical lenses, etc. Since high-grade lenses are not required, the cost is low, and it can be used well in the dark or in poor visibility conditions.

[0011] As a preferred solution, the front and rear surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens of the present invention respectively adopt the optical structure parameter selection types shown in the following table:

[0012]

[0013] Compared with the prior art, the present invention has the following beneficial effects: Only six lenses need to be arranged in the infrared optical lens, with a compact structure and a small number of lenses, which brings great convenience to the assembly and structural design. At the same time, it can ensure the stability of the optical axis during observation and is easy to be assembled into various aircraft electro-optical pods. Among them, the first lens is a convex-plano positive lens, the front surface of the first lens is the convex surface of the lens, and the rear surface is a plane. The second lens is a convex-concave negative lens. The third lens and the fourth lens form a doublet lens. The third lens is a biconvex positive lens, and the fourth lens is a biconcave negative lens. The fifth lens is a convex-concave negative lens. The sixth lens is a concave-convex positive lens. The aperture stop is on the front surface of the second lens. By adopting a reasonable lens combination structure, it can meet the near-infrared long-focus imaging with a wavelength between 0.7um and 1um. Since it does not need to use advanced lenses such as aspherical lenses, the processing cost is low, and it has the advantages of short overall optical length, small volume, easy to carry, simple assembly and adjustment, and high image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic structural diagram of the optical lens of the present invention;

[0015] Figure 2 Spot diagram of the present invention;

[0016] Figure 3 Modulation Transfer Function (MTF) graph of the optical lens of the present invention (cut-off resolution is 30 lp / mm);

[0017] Figure 4 Energy distribution curve graph of the optical lens of the present invention;

[0018] Figure 5 Field curvature and distortion curve graph of the optical lens of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings.

[0020] See Figure 1, a near-infrared long-focus optical lens with a wavelength between 0.7um and 1um according to the present invention, includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6 which are coaxially arranged in sequence from the object side to the image side. A detector is arranged behind the sixth lens L6. Taking the object side to the image side as the reference direction, the front surface S1 of the first lens L1 is a convex surface, and the rear surface S2 of the first lens L1 is a flat surface; the front surface S3 of the second lens L2 is a convex surface, and the rear surface S4 of the second lens L2 is a concave surface; the front surface S5 of the third lens L3 is a convex surface, and the rear surface S6 of the third lens L3 is a convex surface; the front surface S7 of the fourth lens L4 is a concave surface, and the rear surface S8 of the fourth lens L4 is a concave surface; the front surface S9 of the fifth lens L5 is a convex surface, and the rear surface S10 of the fifth lens L5 is a concave surface; the front surface S11 of the sixth lens L6 is a concave surface, and the rear surface S12 of the sixth lens L6 is a convex surface; an aperture stop is arranged on the front surface S3 of the second lens L2. The third lens L3 and the fourth lens L4 form a doublet lens, the third lens L3 is a positive lens and the fourth lens L4 is a negative lens.

[0021] For the optical lens provided by the present invention, the incident energy curves of each field of view are close to the diffraction limit, and the distortion is less than 0.05%.

[0022] For the optical lens provided by the present invention, the optical F number is 5; the back focal length is 3.68mm; the working wavelength is 0.7~1um; the average modulation transfer function value MTF of the full field of view reaches the diffraction limit at 250lp / mm.

[0023] For the near-infrared long-focus optical lens with a wavelength between 0.7um and 1um provided by the present invention, the detector adopts a 1 / 8″, CMOS, 16:9 detector with a pixel size of 2um, the total optical length is 200mm, and the maximum aperture is 60mm.

[0024] In an embodiment of the present invention, all lenses are made of ordinary glass, and no advanced lenses such as aspherical lenses are used, so the cost is low and it can be used well in the dark or in poor visibility conditions. The optical structure parameters are as follows:

[0025]

[0026] Reference Figures 2 to 5 is the aberration analysis diagram of the optical lens in the embodiment of the present invention, wherein, Figure 2 is the spot diagram; Figure 3 is the modulation transfer function MTF diagram; Figure 4 is the energy distribution curve diagram; Figure 5 is the field curvature and distortion curve diagram;

[0027] It can be found from the figure that various aberrations can be well corrected, where the RMS size of the optical blur spot is close to that of the Airy disk; at the same time, the optical transfer function MTF is close to the diffraction limit, and the distortion is less than 0.05%; the energy is concentrated within one pixel of the detector, and the energy is greater than 95%, which can meet the usage requirements of the system.

[0028] It can be seen that the near-infrared long-focus optical lens of the present invention with a wavelength between 0.7um and 1um has good imaging quality. The optical lens of the present invention has a short overall optical length, a small volume, is convenient to carry, has simple alignment and adjustment, low cost, high image quality, and is economical and applicable.

[0029] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the art in the technical field, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A near-infrared long-focus optical lens with a wavelength between 0.7um and 1um, characterized in that: It has six lenses, including a first lens (L1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), and a sixth lens (L6) coaxially arranged in sequence from the object side to the image side. The first lens (L1) is a positive lens, the second lens (L2) is a negative lens, the fifth lens (L5) is a negative lens, and the sixth lens (L6) is a positive lens. A detector is arranged behind the sixth lens (L6). Taking the object side to the image side as the reference direction, the front surface S1 of the first lens (L1) is a convex surface, and the rear surface S2 of the first lens (L1) is a flat surface; the front surface S3 of the second lens (L2) is a convex surface, and the rear surface S4 of the second lens (L2) is a concave surface; the front surface S5 of the third lens (L3) is a convex surface, and the rear surface S6 of the third lens (L3) is a convex surface; the front surface S7 of the fourth lens (L4) is a concave surface, and the rear surface S8 of the fourth lens (L4) is a concave surface; the front surface S9 of the fifth lens (L5) is a convex surface, and the rear surface S10 of the fifth lens (L5) is a concave surface; the front surface S11 of the sixth lens (L6) is a concave surface, and the rear surface S12 of the sixth lens (L6) is a convex surface; an aperture stop is arranged on the front surface S3 of the second lens (L2). The third lens (L3) and the fourth lens (L4) form a doublet lens. The third lens (L3) is a positive lens and the fourth lens (L4) is a negative lens; The focal length of the lens is 300 mm, the back focal length is 3.68 mm, the optical F-number is 5, and the total length is 200 mm; The working wavelength of the lens is 0.7~1 μm; the average modulation transfer function (MTF) value of the full field reaches the diffraction limit at 250 lp / mm; The incident energy curves of each field of the lens are close to the diffraction limit, and the distortion is less than 0.05%; The first lens (L1), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), and the sixth lens (L6) are all made of ordinary glass that is not high-grade optical glass.

2. The near-infrared long-focus optical lens with a wavelength between 0.7um and 1um according to claim 1, characterized in that: A 1 / 8″, 16:9 CMOS detector with a pixel size of 2 μm is used, the total optical length is 200 mm, and the maximum aperture is 60 mm.

3. The near-infrared long-focus optical lens with a wavelength between 0.7um and 1um according to claim 1, characterized in that, The front and rear surfaces of the first lens (L1), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), and the sixth lens (L6) respectively adopt the optical structure parameter selection types shown in the following table: 。

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