CN113741013B - A visible light imaging spectrometer telephoto lens - Google Patents

Abstract

The invention provides a visible light imaging spectrometer telephoto lens. The lens includes 5 optical lenses, which are respectively positive, negative, positive, negative, and positive along the direction of incident light. The focal length of the lens is 11mm, and the F number is 1.8. Visible light band, the wavelength range is 400nm~700nm, the field of view is 18°, and the total optical length of the system is 16.8mm; the visible light lens is designed as an image-side telecentric optical path structure, and can be used as a visible light imaging spectrometer. Use; aspheric technology is used in the design process of the lens, two of the 5 lenses are aspherical lenses, and all aberrations are corrected in the optimization process, so that the lens has excellent image quality, large relative aperture, miniaturization and Lightweight and other advantages.

Description

A visible light imaging spectrometer telephoto lens

technical field

The invention relates to the technical field of optical design, in particular to a visible light imaging spectrometer telescopic head.

Background technique

As a widely used spectral instrument, visible light imaging spectrometer has important applications in agriculture and forestry, geological survey, hydrological monitoring, disaster investigation and so on. In recent years, with the continuous maturity of UAV technology, the rapid development of airborne equipment has been promoted. Volume and weight are important metrics for airborne visible light imaging spectrometers. For longer battery life, miniaturization and light weight are required for airborne imaging spectrometers. The imaging spectrometer mainly includes two parts: a telescopic head and a spectroscopic system. The main function of the telescopic head is to image the target. The spectroscopic system mainly separates the slit images of different wavelengths. It can be seen that the telescopic system determines the imaging quality of the imaging spectrometer. Therefore, the telescope The design of the head is crucial.

In order to ensure a good match between the telephoto system and the spectroscopic system, the telephoto system is required to have an image-side telecentric optical path structure, that is, the chief rays of all fields of view need to be vertically incident on the slit. Since the telephoto lens determines the imaging quality of the entire imaging spectrometer, it is necessary to design the telephoto system as an independent optical system to correct all kinds of aberrations to ensure good imaging quality. At the same time, in order to meet the requirements of unmanned aerial vehicles, the telescopic lens needs to be miniaturized and lightweight. Therefore, the design of the telescopic lens of the UAV imaging spectrometer has certain technical difficulties.

In order to overcome the above shortcomings, a new visible light imaging spectrometer telephoto lens is designed.

SUMMARY OF THE INVENTION

In view of this, an embodiment of the present invention provides a visible light imaging spectrometer telephoto lens, which can be used alone as a visible light imaging lens, and can also be used as a telephoto lens of a visible light imaging spectrometer. The lens is designed with an image-side telecentric optical path structure, which can be well matched with the spectroscopic system and meet the technical requirements as a telephoto lens for an imaging spectrometer. Through reasonable matching of optical materials to ensure good correction of chromatic aberration, the lens will ultimately have the advantages of excellent image quality, large relative aperture, miniaturization and light weight.

An embodiment of the present invention provides a visible light imaging spectrometer telephoto lens, which includes a first positive lens, a first negative lens, a second positive lens, a second negative lens, and a third positive lens that are coaxially arranged in sequence along a light incident direction , the material of the first positive lens is HZBAF16, 7mm<clear aperture<8mm, 2mm<thickness<3mm; the material of the first negative lens is HF51, 6mm<clear aperture<7mm, 1mm<thickness<2mm ; The material of the second positive lens is HLAF3B, 5mm<clear aperture<6mm, 2mm<thickness<3mm; the material of the second negative lens is HZF3, 4mm<clear aperture<5mm, 2mm<thickness<3mm ; The material of the third positive lens is HLAF4, 4mm<clear aperture<5mm, 2mm<thickness<3mm. The aforementioned five optical materials are selected from Chengdu Guangming Glass Warehouse, and they are all optical glasses with very low unit price.

Optionally, the clear aperture of the first positive lens is 7.2mm and the thickness is 2.80mm; the clear aperture of the first negative lens is 6.0mm and the thickness is 1.04mm; The aperture is 5.4mm and the thickness is 2.80mm; the aperture of the second negative lens is 4.8mm and the thickness is 2.00mm; the aperture of the third positive lens is 4.6mm and the thickness is 2.00mm.

Optionally, the second positive lens and the second negative lens form a cemented lens.

Optionally, the distance between the center of the light exit surface of the third positive lens and the image surface is 1.2 mm.

Optionally, the outer dimension of the visible light imaging spectrometer telephoto lens is φ7.2×16.8mm.

Optionally, the focal length of the optical system of the visible light imaging spectrometer telephoto lens is 11 mm, and the F-number is 1.8.

Optionally, the spectral range of the visible light imaging spectrometer telephoto lens is 400 nm to 700 nm.

Optionally, the full field of view of the visible light imaging spectrometer telephoto lens is 18°.

As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

1. The visible light imaging spectrometer telephoto lens has a working spectral range of 400nm to 700nm, has an image-side telecentric optical path structure, matches the technical requirements of the imaging spectrometer for the telephoto lens, and can be perfectly connected to the spectroscopic system. The focal length of the telephoto lens is 11mm, With an F-number of 1.8, the lens has super light-gathering capabilities.

2. The visible light imaging spectrometer telephoto lens adopts aspherical technology to simplify the optical path structure of the optical system. The final system includes 5 lenses, of which 2 are aspherical and 3 are spherical. The total length of the system is only 16.8mm, and the optical aperture is 7.2mm. The lens has obvious advantages of miniaturization and light weight.

Description of drawings

Fig. 1 is the optical path structure diagram of the visible light imaging spectrometer telescopic head of the present invention;

Fig. 2 is the spot diagram of the visible light imaging spectrometer telescopic head of the present invention;

Fig. 3 is the optical modulation transfer function of the visible light imaging spectrometer telephoto lens of the present invention;

Reference numerals: 1-first positive lens; 2-first negative lens; 3-second positive lens; 4-second negative lens; 5-third positive lens.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be cleared and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Please refer to FIG. 1 , which is an optical path structure diagram of the present invention. The visible light imaging spectrometer telescopic head includes 5 lenses, and the 5 lenses are arranged in the form of positive, negative, positive, and negative, and 2 lenses are aspherical, which is beneficial to the optical path structure. The simplification ensures that the lens has the advantages of miniaturization and light weight, and at the same time improves the imaging quality of the lens. The 5 lenses include a first positive lens 1, a first negative lens 2, a second positive lens 3, a second negative lens 4 and a third positive lens 5 that are coaxially arranged in sequence along the incident direction of the light. The first positive lens 1. The material is HZBAF16, 7mm<clear aperture<8mm, 2mm<thickness<3mm; the material of the first negative lens 2 is HF51, 6mm<clear aperture<7mm, 1mm<thickness<2mm; the second positive lens 3. The material is HLAF3B, 5mm<clear aperture<6mm, 2mm<thickness<3mm; the material of the second negative lens 4 is HZF3, 4mm<clear aperture<5mm, 2mm<thickness<3mm; the third positive lens 5 The material is HLAF4, 4mm<clear aperture<5mm, 2mm<thickness<3mm.

In one embodiment, the clear aperture of the first positive lens 1 is 7.2mm and the thickness is 2.80mm; the clear aperture of the first negative lens 2 is 6.0mm and the thickness is 1.04mm; The aperture of the lens 3 is 5.4mm and the thickness is 2.80mm; the aperture of the second negative lens 4 is 4.8mm and the thickness is 2.00mm; the aperture of the third positive lens 5 is 4.6mm and the thickness is 2.00mm mm; in this way, the system focal length of the visible light imaging spectrometer telephoto lens is 11mm, the F number is 1.8, the full field of view is 18°, and the overall size is φ7.2×16.8mm. The lens has excellent image quality, large relative aperture, and miniaturization. and lightweight advantages.

In one embodiment, the second positive lens and the second negative lens form a cemented lens, and the combination of optical materials of the two lenses ensures that the chromatic aberration of the optical system can be well corrected.

In one of the embodiments, the visible light imaging spectrometer telephoto lens has a spectral range of 400 nm to 700 nm, and five optical materials are selected from the Chengdu Guangming Glass Library, all of which are very cheap optical glasses.

The embodiment of the present invention is designed as an image-side telecentric optical path structure, and the principal rays of each field of view of the visible light imaging spectrometer telescope head are vertically incident on the image plane, which achieves a good match with the spectroscopic system and fully meets the technical requirements for use as an imaging spectrometer telescope head .

Please refer to FIG. 2 , which is a dot diagram of the visible light imaging spectrometer telephoto lens of the present invention. It can be seen from the figure that the RMS of the diffused spot corresponding to each field angle is basically less than 6.5 μm, indicating that the lens has good imaging quality.

Please refer to FIG. 3 , which is the optical modulation transfer function MTF of the visible light imaging spectrometer telephoto head of the present invention. It can be seen from the figure that in the spatial frequency range within 200 cycles/mm, the MTF of each field of view is basically higher than 0.2, which satisfies the optical Lens design requirements.

Below, the lens data of the visible light imaging spectrometer telephoto lens is shown. Table 1 shows the relevant optical parameters of each lens in the optical lens.

Table 1

The aspheric surface type expression formula adopted in the embodiment of the present invention:

Among them, z is the sag of the aspheric surface from the vertex of the aspheric surface when the radius is r along the optical axis; c is the paraxial curvature of the aspheric surface, k is the conic coefficient; A _i is the correction coefficient of the i-th order of the aspheric surface .

Table 2 shows the coefficients of the respective aspheric higher-order terms in this embodiment.

Table 2

S3 2.29E-03 -2.35E-04 -9.29E-07 2.11E-06 -6.83E-08 -1.50E-08 9.76E-10 S4 7.35E-03 -6.35E-04 1.08E-04 -1.96E-05 1.91E-06 1.88E-07 -3.57E-08 S9 1.08E-03 -6.80E-04 3.55E-04 -3.39E-05 -7.99E-06 1.37E-06 -5.16E-08 S10 -1.84E-02 3.44E-03 9.09E-05 -1.03E-04 -8.38E-07 2.25E-06 -1.60E-07

The visible light imaging spectrometer telephoto lens of the present invention has a focal length of 11 mm, an F-number of 1.8, a working band of visible light, a wavelength range of 400 nm to 700 nm, a field of view angle of 18°, and a total optical length of 16.8 mm. The image-side telecentric structure can be used as a telephoto lens for a visible light imaging spectrometer, or as a visible light lens alone; the lens is designed with aspherical technology to correct all kinds of aberrations, and the lens has image It has the advantages of good quality, large relative aperture, miniaturization and light weight.

The specific embodiments of the present invention described above do not limit the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (8)

1. A telescope lens of visible light imaging spectrometer, its characterized in that: the lens is composed of a first positive lens, a first negative lens, a second positive lens, a second negative lens and a third positive lens which are coaxially arranged in sequence along the incident direction of light;

the material of the first positive lens is HZBAF16, 7mm < the clear aperture <8mm, 2mm < the thickness <3 mm;

the first negative lens is made of HF51, the light transmission aperture is 6mm <7mm, and the thickness is 1mm <2 mm;

the second positive lens is made of HLAF3B, 5mm < light-passing aperture <6mm, 2mm < thickness <3 mm;

the second negative lens is made of HZF3, the light-passing aperture is 4mm <5mm, and the thickness is 2mm <3 mm;

the third positive lens is made of HLAF4, 4mm < light-passing aperture <5mm, and 2mm < thickness <3 mm.

2. The visible light imaging spectrometer telescope lens of claim 1, wherein:

the light-transmitting aperture of the first positive lens is 7.2mm, and the thickness of the first positive lens is 2.80 mm;

the clear aperture of the first negative lens is 6.0mm, and the thickness of the first negative lens is 1.04 mm;

the light-transmitting aperture of the second positive lens is 5.4mm, and the thickness of the second positive lens is 2.80 mm;

the clear aperture of the second negative lens is 4.8mm, and the thickness of the second negative lens is 2.00 mm;

the light-transmitting aperture of the third positive lens is 4.6mm, and the thickness of the third positive lens is 2.00 mm.

3. The visible light imaging spectrometer telescope lens of claim 1, wherein: the second positive lens and the second negative lens constitute a cemented lens.

4. The visible light imaging spectrometer telescope lens of claim 1, wherein: and the distance between the center of the light emergent surface of the third positive lens and the image surface is 1.2 mm.

5. The visible light imaging spectrometer telescope lens of claim 1, wherein: the external dimension of the telescope lens of the visible light imaging spectrometer is phi 7.2 multiplied by 16.8 mm.

6. The visible light imaging spectrometer telescope lens of claim 1, wherein: the focal length of an optical system of the telescope lens of the visible light imaging spectrometer is 11mm, and the F number is 1.8.

7. The visible light imaging spectrometer telescope lens of claim 1, wherein: the spectral range of the telescope lens of the visible light imaging spectrometer is 400 nm-700 nm.

8. The visible light imaging spectrometer telescopic lens of claim 1, wherein: the full field of view of the telescope lens of the visible light imaging spectrometer is 18 degrees.

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