Near-infrared fixed-focus optical system

Abstract

The invention relates to the technical field of optical lenses, and discloses a near-infrared fixed-focus optical system which comprises a first lens, a second lens, a third lens, a fourth lens, a first gluing piece, a fifth lens, a diaphragm, a sixth lens and a second gluing piece which are sequentially arranged from an object plane to an image plane, and an optical axis serves as a rotation center. One object surface of the lens is a convex spherical surface, the curvature radius is 61.53 mm, the image surface is a plane, and the curvature radius is infinity; the object surface of the second lens is a convex spherical surface, the curvature radius of the second lens is 32.32 mm, the image surface of the second lens is a concave spherical surface, and the curvature radius of the second lens is 22.02 mm. The focal length of the lens of the near-infrared fixed-focus optical system is 16mm, so that the shooting view field range is greatly expanded, and the requirement of large-scene visual detection can be met; meanwhile, an aperture F # is 1.4, so that enough light incoming quantity can be ensured in an outdoor dark scene or an indoor low-illumination environment; even under the outdoor dark environment or the indoor low-illumination condition, it can still be ensured that the image is clear and rich in details, and the imaging accuracy and stability are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical lens, in particular to a near-infrared fixed focus optical system. BACKGROUND

[0002] Fruit and vegetable, food, medicine and other health detection need to be shot in the near-infrared band to capture its unique defect characteristics, in this kind of visual detection, near-infrared camera is needed to cooperate with near-infrared optical system to realize it.

[0003] The minimum focal length of the infrared fixed focus imaging system on the market is generally more than 25mm, and the aperture is generally greater than F#2.0, which has great limitations in the flow line or outdoor environment; we develop a kind of near-infrared fixed focus optical system to solve the problem of poor imaging effect in the outdoor dark scene or indoor low-illumination environment. SUMMARY

[0004] Based on the above description, the present application provides a kind of near-infrared fixed focus optical system to solve the problem of poor imaging effect of existing visual detection system for outdoor dark scene or indoor low-illumination environment.

[0005] The technical scheme for solving the above technical problems is as follows: a kind of near-infrared fixed focus optical system, including lens one, lens two, lens three, lens four, cemented piece one, lens five, diaphragm, lens six, cemented piece two arranged in order from object plane to image plane, and with optical axis as the rotation center; The object plane of the lens one is a convex spherical surface with a radius of curvature of 61.53mm, and the image plane is a plane with a radius of curvature of ∞; The object plane of the lens two is a convex spherical surface with a radius of curvature of 32.32mm, and the image plane is a concave spherical surface with a radius of curvature of 22.02mm; The object plane of the lens three is a concave spherical surface with a radius of curvature of-31.79mm, and the image plane is a concave spherical surface with a radius of curvature of 31.79mm;The object plane of the lens four is a convex spherical surface with a radius of curvature of 72.43mm, and the image plane is a convex spherical surface with a radius of curvature of-43.35mm; The object plane of the first lens in the cemented piece one is a convex spherical surface with a radius of curvature of 49.83mm, and the image plane is a concave spherical surface with a radius of curvature of 24.82mm;The object plane of the second lens in the cemented piece one is a convex spherical surface with a radius of curvature consistent with that of the image plane of the first lens in the cemented piece one, and the image plane is a plane with a radius of curvature of ∞; The object plane of the lens five is a convex spherical surface with a radius of curvature of 31.41mm, and the image plane is a convex spherical surface with a radius of curvature of-68.18mm; The object plane of the lens six is a convex spherical surface with a radius of curvature of 57.74mm, and the image plane is a concave spherical surface with a radius of curvature of 23.28mm; The object surface of the first piece in the second cemented piece is a convex spherical surface with a curvature radius of 49.98 mm, and the image surface is a convex spherical surface with a curvature radius of -49.88 mm; The object surface of the second piece in the second cemented piece is a concave spherical surface with a curvature consistent with the curvature of the image surface of the first piece of the second cemented piece, and the image surface is a convex spherical surface with a curvature radius of -20.24 mm; The object surface of the third piece in the second cemented piece is a concave spherical surface with a curvature consistent with the curvature of the image surface of the second piece of the second cemented piece, and the image surface is a convex spherical surface with a curvature radius of -36.97 mm.

[0006] On the basis of the above technical solutions, the application can also be improved as follows.

[0007] Further, the curvature surface tolerance of the lens one, the lens two, the lens three, the lens four, the cemented piece one, the lens five, the diaphragm, the lens six and the cemented piece two is 3-5 aperture, and the local aperture is 0.3-0.5.

[0008] Further, the center thickness of the lens one is 5.28 mm±0.02 mm, the center thickness of the lens two is 2 mm±0.02 mm, the center thickness of the lens three is 2.86 mm±0.02 mm, and the center thickness of the lens four is 3.88 mm±0.02 mm. The center thickness of the first lens of the cemented piece one is 3.36 mm±0.02 mm, and the center thickness of the second lens is 5.51 mm±0.02 mm. The center thickness of the lens five is 4.49 mm±0.02 mm, and the center thickness of the lens six is 2 mm±0.02 mm. The center thickness of the first piece of the cemented piece two is 3.84 mm±0.02 mm, the center thickness of the second piece is 5 mm±0.02 mm, and the center thickness of the third piece is 2 mm±0.02 mm.

[0009] Further, the focal length of the lens one is 73.307 mm, the focal length of the lens two is -38.171 mm, the focal length of the lens three is -24.605 mm, the focal length of the lens four is 28.255 mm, the focal length of the cemented piece one is 258.431 mm, the focal length of the lens five is 26.328 mm, the focal length of the lens six is -30.935 mm, and the focal length of the cemented piece two is 43.056 mm.

[0010] Further, the aperture of the first lens is 42.3mm, the aperture of the second lens is 30.1mm, the aperture of the third lens is 25.5mm, the aperture of the fourth lens is 25.5mm, the aperture of the first cemented lens is 25.5mm, the aperture of the fifth lens is 21.3mm, the aperture of the sixth lens is 20mm, and the aperture of the second cemented lens is 20mm.

[0011] Further, the diaphragm is arranged between the fifth lens and the sixth lens, and the total length of the optical system is 80mm.

[0012] Further, the optical interval between the first lens and the second lens is 0.51mm±0.02mm, the optical interval between the second lens and the third lens is 9.89mm±0.02mm, the optical interval between the third lens and the fourth lens is 2.364mm±0.02mm, the optical interval between the fourth lens and the first cemented lens is 6.421mm±0.02mm, the optical interval between the first cemented lens and the fifth lens is 0.2mm±0.02mm, the optical interval between the fifth lens and the diaphragm is 0.3mm±0.02mm, the optical interval between the diaphragm and the sixth lens is 0.52mm±0.02mm, and the optical interval between the sixth lens and the second cemented lens is 3.61mm±0.05mm.

[0013] Further, the first lens is made of heavy lanthanum flint glass (h-zlaf4lb), the second lens is made of crown glass (h-k9l), the third lens is made of heavy flint glass (h-zf4a), and the fourth lens is made of heavy lanthanum flint glass (h-zlaf4lb). The first lens of the first cemented lens is made of heavy flint glass (h-zf4a), and the second lens is made of heavy crown glass (h-zk9b). The fifth lens is made of lanthanum flint glass (h-laf50b), the sixth lens is made of crown glass (h-k9l), the first lens of the second cemented lens is made of heavy flint glass (h-zf12), the second lens is made of heavy phosphor crown glass (h-zpk5), and the third lens is made of heavy lanthanum flint glass (h-zlf75a).

[0014] Further, the aperture of the optical system is F / 1.4, the focal length of the system is 16mm, the image size is 16mm in diameter, the working distance is infinite, and the diagonal angle of view is 43.6°.

[0015] Further, the working environment of the optical system is infrared environment, and the working waveband is 950nm-1300nm.

[0016] Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects: The lens focal length of the near-infrared fixed focus optical system is 16 mm, which greatly expands the shooting field of view range and can meet the needs of large scene visual detection; at the same time, the aperture F# is 1.4, which can ensure sufficient light quantity whether in an outdoor dark scene or in an indoor low-illumination environment; even in an outdoor dark environment or an indoor low-illumination condition, the image can still be clear and rich in details, effectively solving the pain point of poor visual detection imaging quality in a weak light environment and guaranteeing the accuracy and stability of imaging. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A light path structure schematic diagram of a near-infrared fixed focus optical system provided by the embodiment of the application is shown in the figure. Figure 2 It is a light fan diagram of the optical system of the application. Figure 3 It is a distortion and field curvature diagram of the optical system of the application. Figure 4 It is a modulation optical transfer function curve diagram of the optical system of the application. Figure 5 It is an image plane illumination decay curve diagram of the optical system of the application. Figure 6 It is a diffraction circle diagram of the optical system of the application.

[0018] Reference signs: 1, lens one; 2, lens two; 3, lens three; 4, lens four; 5, cemented piece one; 51, first lens; 52, second lens; 6, lens five; 7, diaphragm; 8, lens six; 9, cemented piece two; 91, first piece; 92, second piece; 93, third piece. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0021] Embodiment: Figure 1The optical path structure diagram of the whole optical system is composed of spherical glass lenses and the diaphragm 7. All the lenses and the diaphragm 7 are sequentially arranged with the optical axis as the rotation center, and from left to right, they are lens one 1, lens two 2, lens three 3, lens four 4, cemented plate one 5, lens five 6, the diaphragm 7, lens six 8 and cemented plate two 9.

[0022] Reference Figure 1 It should be noted that the leftmost in the figure is the focusing object plane of the system, and the rightmost is the ideal image plane of the whole system. The distance from the center of curvature of the first lens to the image plane is 80 mm.

[0023] Figure 2 The aberration set generated by different field regions is shown, and the difference between the meridional plane and the sagittal plane aberration can be seen in each field region.

[0024] Figure 3 The field curvature and distortion of the system are shown. The left is the field curvature (image plane curvature), and we can see that different curves represent different wavelengths, and the maximum image plane curvature deviation is 0.0754 mm. The right graph shows the optical distortion, and the maximum optical distortion is less than 0.5196%.

[0025] Figure 4 The spatial transfer function of the whole optical system in the working waveband is shown. It is a form of expression reflecting the imaging quality of the whole imaging system, and the abscissa is line pairs per millimeter, and the ordinate is frequency. Different lines represent different fields and the difference between the meridian or sagittal.

[0026] Figure 5 It mainly reflects the light distribution in different areas of the image plane after the light passes through the optical system, and reflects the attenuation of the illumination of different fields. This figure is an important indicator for evaluating the illumination of the image plane of the whole optical system. From the figure, we can see that the image illumination of all fields reaches more than 85%.

[0027] Figure 6 It is the diffusion of all entrance pupil rays converging to the image plane in different field regions, and different curves represent different wavelengths. It is also an important way to evaluate the overall imaging characteristics of an optical system. It can be seen that the geometric diameter of the diffraction spot of all fields in the design wavelength range can reach within 21.448 microns.

[0028] Reference Figure 1 The main parameters of the optical system are the curvature, center thickness, focal length, aperture of each component lens, optical spacing between lenses, and the material of each lens (because the optical properties of different materials are different, mainly the refractive index and dispersion coefficient). Next, we will describe the parameters of the optical path.

[0029] The whole optical structure surface is on the left, the initial focusing object distance is infinite; the image surface is on the right, the image distance is 16mm; we define the left surface curvature of each lens as the object surface curvature of the lens, the right surface curvature as the image surface curvature, and the convex surface towards the object surface is positive, and the convex surface towards the image surface is negative; the following describes the parameters of the lens curvature of the system.

[0030] The curvature surface type data of each lens is as follows: The object surface of lens one 1 is a convex spherical surface with a curvature radius of 61.53mm, and the image surface is a plane with a curvature radius of ∞; The object surface of lens two 2 is a convex spherical surface with a curvature radius of 32.32mm, and the image surface is a concave spherical surface with a curvature radius of 22.02mm; The object surface of lens three 3 is a concave spherical surface with a curvature radius of -31.79mm, and the image surface is a concave spherical surface with a curvature radius of 31.79mm; the object surface of lens four 4 is a convex spherical surface with a curvature radius of 72.43mm, and the image surface is a convex spherical surface with a curvature radius of -43.35mm; The object surface of the first lens 51 in the cemented plate one 5 is a convex spherical surface with a curvature radius of 49.83mm, and the image surface is a concave spherical surface with a curvature radius of 24.82mm; the object surface of the second lens 52 in the cemented plate one 5 is a convex spherical surface with a curvature radius consistent with that of the image surface of the first lens 91 in the cemented plate one 5, and the image surface is a plane with a curvature radius of ∞; The object surface of lens five 6 is a convex spherical surface with a curvature radius of 31.41mm, and the image surface is a convex spherical surface with a curvature radius of -68.18mm; The object surface of lens six 8 is a convex spherical surface with a curvature radius of 57.74mm, and the image surface is a concave spherical surface with a curvature radius of 23.28mm; The object surface of the first lens 91 in the cemented plate two 9 is a convex spherical surface with a curvature radius of 49.98mm, and the image surface is a convex spherical surface with a curvature radius of -49.88mm; the object surface of the second lens 92 in the cemented plate two 9 is a concave spherical surface with a curvature radius consistent with that of the image surface of the first lens 91 in the cemented plate two 9, and the image surface is a convex spherical surface with a curvature radius of -20.24mm; the object surface of the third lens 93 in the cemented plate two 9 is a concave spherical surface with a curvature radius consistent with that of the image surface of the second lens 92 in the cemented plate two 9, and the image surface is a convex spherical surface with a curvature radius of -36.97mm.

[0031] It should be noted that the surface type tolerance of all curvatures is 3-5 aperture, and the local aperture is 0.3-0.5 (detected by an interferometer).

[0032] The center thickness data of each group of lenses is as follows: The center thickness of the lens one 1 is 5.28mm, the tolerance is ±0.02mm; the center thickness of the lens two 2 is 2mm, the tolerance is ±0.02mm; the center thickness of the lens three 3 is 2.86mm, the tolerance is ±0.02mm; the center thickness of the lens four 4 is 3.88mm, the tolerance is ±0.02mm; the center thickness of the first lens 51 of the cemented piece one 5 is 3.36mm, the tolerance is ±0.02mm, the center thickness of the second lens 52 is 5.51mm, the tolerance is ±0.02mm; the center thickness of the lens five 6 is 4.49mm, the tolerance is ±0.02mm; the center thickness of the lens six 8 is 2mm, the tolerance is ±0.02mm; the center thickness of the first piece 91 of the cemented piece two 9 is 3.84mm, the tolerance is ±0.02mm, the center thickness of the second piece 92 is 5mm, the tolerance is ±0.02mm, the center thickness of the third piece 93 is 2mm, the tolerance is ±0.02mm.

[0033] The focal length data of each group of lenses are as follows: The focal length of the lens one 1 is 73.307mm; the focal length of the lens two 2 is -38.171mm; the focal length of the lens three 3 is -24.605mm; the focal length of the lens four 4 is 28.255mm; the focal length of the cemented piece one 5 is 258.431mm; the focal length of the lens five 6 is 26.328mm; the focal length of the lens six 8 is -30.935mm; the focal length of the cemented piece two 9 is 43.056mm; The aperture data of each group of lenses are as follows: The aperture of the lens one 1 is 42.3mm; the aperture of the lens two 2 is 30.1mm; the aperture of the lens three 3 is 25.5mm; the aperture of the lens four 4 is 25.5mm; the aperture of the cemented piece one 5 is 25.5mm; the aperture of the lens five 6 is 21.3mm; the aperture of the lens six 8 is 20mm; the aperture of the cemented piece two 9 is 20mm.

[0034] Reference Figure 1 The system is composed of 8 groups of 11 pieces of glass lenses, the light path of the diaphragm 7, the system diaphragm 7 of the whole optical system is arranged between the lens five 6 and the lens six 8, the total optical length of the system (the curvature center of the first surface of the lens one 1 to the image surface) is 80mm.

[0035] The optical interval of the lens one 1 to the lens two 2 is 0.51mm, the tolerance is ±0.02mm; the optical interval of the lens two 2 to the lens three 3 is 9.89mm, the tolerance is ±0.02mm; the optical interval of the lens three 3 to the lens four 4 is 2.364mm, the tolerance is ±0.02mm; the optical interval of the lens four 4 to the cemented piece one 5 is 6.421mm, the tolerance is ±0.02mm; the optical interval of the cemented piece one 5 to the lens five 6 is 0.2mm, the tolerance is ±0.02mm; The optical interval of lens five 6 to diaphragm 7 is 0.3mm, the tolerance is ±0.02mm; the optical interval of diaphragm 7 to lens six 8 is 0.52mm, the tolerance is ±0.02mm; the optical interval of lens six 8 to cemented plate two 9 is 3.61mm, the tolerance is ±0.05mm.

[0036] The material data of each lens is as follows: All the lenses adopt the colorless glass of Chengdu Guangming, all use Chengdu Guangming's brand, and in order to ensure the follow-up industrial production, all the brands are the recommended brands of current mass production.

[0037] Lens one 1 adopts heavy lanthanum flint glass (h-zlaf4lb); lens two 2 adopts crown glass (h-k9l); lens three 3 adopts heavy flint glass (h-zf4a); lens four 4 adopts heavy lanthanum flint glass (h-zlaf4lb); the first lens 51 of cemented plate one 5 adopts heavy flint glass (h-zf4a), the second lens 52 adopts heavy crown glass (h-zk9b); lens five 6 adopts lanthanum flint glass (h-laf50b); lens six 8 adopts crown glass (h-k9l); the first plate 91 of cemented plate two 9 adopts heavy flint glass (h-zf12), the second plate 92 adopts heavy phosphor crown glass (h-zpk5), and the third plate 93 adopts heavy lanthanum flint glass (h-zlf75a).

[0038] The aperture of the system is F / 1.4; the focal length of the system is 16mm; the image plane size is 16mm in diameter; the working distance is infinity; and the diagonal angle of view is 43.6°.

[0039] The working environment of the system is infrared environment, and the working waveband is 950nm-1300nm.

[0040] The above only describes the preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A near-infrared fixed focus optical system characterized by comprising: It comprises lens one (1), lens two (2), lens three (3), lens four (4), adhesive piece one (5), lens five (6), diaphragm (7), lens six (8), adhesive piece two (9) arranged in order from object plane to image plane, and with optical axis as the rotation center; The object plane of the lens one (1) is convex spherical surface with a curvature radius of 61.53 mm, and the image plane is a plane with a curvature radius of ∞; The object plane of the lens two (2) is convex spherical surface with a curvature radius of 32.32 mm, and the image plane is concave spherical surface with a curvature radius of 22.02 mm; The object plane of the lens three (3) is concave spherical surface with a curvature radius of -31.79 mm, and the image plane is concave spherical surface with a curvature radius of 31.79 mm; the object plane of the lens four (4) is convex spherical surface with a curvature radius of 72.43 mm, and the image plane is convex spherical surface with a curvature radius of -43.35 mm; The object plane of the first lens (51) in the adhesive piece one (5) is convex spherical surface with a curvature radius of 49.83 mm, and the image plane is concave spherical surface with a curvature radius of 24.82 mm; the object plane of the second lens (52) in the adhesive piece one (5) is convex spherical surface, and the curvature is consistent with that of the image plane of the first piece (91) of the adhesive piece one (5), and the image plane is a plane with a curvature radius of ∞; The object plane of the lens five (6) is convex spherical surface with a curvature radius of 31.41 mm, and the image plane is convex spherical surface with a curvature radius of -68.18 mm; The object plane of the lens six (8) is convex spherical surface with a curvature radius of 57.74 mm, and the image plane is concave spherical surface with a curvature radius of 23.28 mm; The object plane of the first piece (91) in the adhesive piece two (9) is convex spherical surface with a curvature radius of 49.98 mm, and the image plane is convex spherical surface with a curvature radius of -49.88 mm; The object plane of the second piece (92) in the adhesive piece two (9) is concave spherical surface, and the curvature is consistent with that of the image plane of the first piece (91) of the adhesive piece two (9), and the image plane is convex spherical surface with a curvature radius of -20.24 mm; The object plane of the third piece (93) in the adhesive piece two (9) is concave spherical surface, and the curvature is consistent with that of the image plane of the second piece (92) of the adhesive piece two (9), and the image plane is convex spherical surface with a curvature radius of -36.97 mm.

2. The near-infrared fixed focus optical system according to claim 1, wherein The curvature surface tolerance of the lens one (1), lens two (2), lens three (3), lens four (4), adhesive piece one (5), lens five (6), diaphragm (7), lens six (8), and adhesive piece two (9) is aperture 3-5, and local aperture 0.3-0.

5.

3. The near-infrared fixed focus optical system according to claim 1, wherein The central thickness of the lens one (1) is 5.28 mm±0.02 mm, the central thickness of the lens two (2) is 2 mm±0.02 mm, the central thickness of the lens three (3) is 2.86 mm±0.02 mm, and the central thickness of the lens four (4) is 3.88 mm±0.02 mm; The central thickness of the first lens (51) of the adhesive piece one (5) is 3.36 mm±0.02 mm, and the central thickness of the second lens (52) is 5.51 mm±0.02 mm. The center thickness of the lens five (6) is 4.49mm±0.02mm; the center thickness of the lens six (8) is 2mm±0.02mm; The center thickness of the first piece (91) of the cemented piece two (9) is 3.84mm±0.02mm, the center thickness of the second piece (92) is 5mm±0.02mm, and the center thickness of the third piece (93) is 2mm±0.02mm.

4. The near-infrared fixed focus optical system according to claim 1, wherein The focal length of the lens one (1) is 73.307mm, the focal length of the lens two (2) is -38.171mm, the focal length of the lens three (3) is -24.605mm, the focal length of the lens four (4) is 28.255mm, the focal length of the cemented piece one (5) is 258.431mm, the focal length of the lens five (6) is 26.328mm, the focal length of the lens six (8) is -30.935mm, and the focal length of the cemented piece two (9) is 43.056mm.

5. The near-infrared fixed focus optical system according to claim 1, wherein The aperture of the lens one (1) is 42.3mm, the aperture of the lens two (2) is 30.1mm, the aperture of the lens three (3) is 25.5mm, the aperture of the lens four (4) is 25.5mm, the aperture of the cemented piece one (5) is 25.5mm, the aperture of the lens five (6) is 21.3mm, the aperture of the lens six (8) is 20mm, and the aperture of the cemented piece two (9) is 20mm.

6. The near-infrared fixed focus optical system according to claim 1, wherein The diaphragm (7) is arranged between the lens five (6) and the lens six (8), and the total length of the optical system is 80mm.

7. The near-infrared fixed focus optical system according to claim 6, wherein The optical interval between the lens one (1) and the lens two (2) is 0.51mm±0.02mm, the optical interval between the lens two (2) and the lens three (3) is 9.89mm±0.02mm, the optical interval between the lens three (3) and the lens four (4) is 2.364mm±0.02mm, the optical interval between the lens four (4) and the cemented piece one (5) is 6.421mm±0.02mm, the optical interval between the cemented piece one (5) and the lens five (6) is 0.2mm±0.02mm, the optical interval between the lens five (6) and the diaphragm (7) is 0.3mm±0.02mm, the optical interval between the diaphragm (7) and the lens six (8) is 0.52mm±0.02mm, and the optical interval between the lens six (8) and the cemented piece two (9) is 3.61mm±0.05mm.

8. The near-infrared fixed focus optical system according to claim 1, wherein The lens one (1) is made of heavy lanthanum flint glass (h-zlaf4lb), the lens two (2) is made of crown glass (h-k9l), the lens three (3) is made of heavy flint glass (h-zf4a), and the lens four (4) is made of heavy lanthanum flint glass (h-zlaf4lb); The first lens (51) of the cemented piece one (5) is made of heavy flint glass (h-zf4a), and the second lens (52) is made of heavy crown glass (h-zk9b); The first lens (51) of the cemented piece one (5) is made of heavy flint glass (h-zf4a), and the second lens (52) is made of heavy crown glass (h-zk9b); The lens five (6) adopts h-laf50b, the lens six (8) adopts h-k9l, the first piece (91) of the cemented plate two (9) adopts h-zf12, the second piece (92) adopts h-zpk5, and the third piece (93) adopts h-zlf75a.

9. A near-infrared fixed focus optical system according to any one of Claims 1 to 8, wherein The aperture of the optical system is F / 1.4, the focal length is 16mm, the image plane size is 16mm in diameter, the working distance is infinity, and the diagonal angle of view is 43.6°.

10. The near-infrared fixed focus optical system according to claim 9, wherein The working environment of the optical system is an infrared environment, and the working waveband is 950nm-1300nm.

Images