CN209417404U - Wide-spectrum non-focusing all-sky airglow imager - Google Patents

Abstract

The utility model relates to an airglow imager, aiming at the problems that the existing airglow imager has a small detection field of view, a narrow spectrum range and a mechanical focusing device, which lead to complex structure and operation of the imager and low luminous flux of the imager. , providing a wide-spectrum non-focusing all-sky airglow imager. The imager includes an image-space telecentric fisheye lens, an object-space telecentric imaging lens and a detector; a filter wheel is set between the fisheye lens and the imaging lens, and the filter wheel is equipped with multiple different bands and has zero focal power The narrow-band filter, the filter wheel can switch the narrow-band filter to the focal plane of the fisheye lens; the fisheye lens includes a negative power front lens group and a positive power rear lens group, the front lens group and the rear lens group There is an aperture stop on the optical path between them; the imaging lens includes a plurality of cemented mirrors made of positive lenses and negative lenses, the absolute value of the relative Abbe number difference between the positive lens and the negative lens is ≥5, and its relative dispersion The absolute value of the difference is ≤0.001.

Description

A wide-spectrum non-focusing all-sky airglow imager

technical field

The utility model relates to an airglow imager, in particular to a wide-spectrum non-focusing all-sky airglow imager.

Background technique

Airglow is an important natural luminous phenomenon in the earth's space environment. It is a certain wavelength of light emitted by molecules and atoms in the atmosphere excited by the sun's short-wave ultraviolet radiation. It generally appears between 50-500km above the earth, and its brightness is very low. The distribution is uneven and difficult to detect, and only very sensitive instruments can observe it.

The spatial and temporal distribution of airglow is modulated by various atmospheric dynamic processes such as tidal waves, atmospheric gravity waves and planetary waves, and is an important tracer of atmospheric dynamic processes and atmospheric photochemical processes. special status.

As shown in Figure 1 and Figure 2, an existing airglow imager consists of a fisheye lens 01, a diaphragm 02, a first imaging mirror 03, a filter wheel 04 (including a filter 041), a second imaging mirror 05. CCD detector 06, mechanical focusing device 07, computer 08 and other optical devices.

Because the structure of the existing imager has high requirements on the surface quality of the filter, the detection band range of the imager is wide, and the filters of different bands of the system have axial chromatic aberration. After switching the filter, the image plane will be shifted, which will affect the image quality. Therefore, after the filter wheel 04 switches the filter 041, it is necessary to use the mechanical focus device 07 to adjust the focus. However, the structure of the mechanical focusing device 07 is complicated, which increases the manufacturing cost of the imager; and because each time the filter wheel 04 is used to switch the filter 041, it is necessary to adjust the focus of the filter 041 of different wavelengths, resulting in the loss of the imager. The operation is cumbersome and complicated; the mechanical focusing device 07 may also malfunction, affecting the imaging quality of the imager, or even failing to image.

And the fisheye lens 01 of the existing imager adopts a conventional fisheye lens (for example: Nikon 8mm f/2.8 fisheye lens), and it is necessary to equip an additional image square telecentric first imaging mirror 03 to match the filter 041 pair The angle of incidence of the incident light is required, but the conventional fisheye lens 01 matching the structure of the imaging mirror has a narrow wavelength band of the imager, and the additional first imaging mirror 03 also makes the structure of the imager more complicated. At the same time, because the finished fisheye lens 01 adopted by the airglow imager with this structure has a small aperture corresponding to the primary image surface of the first imaging mirror 03, the effective relative aperture of the matching filter 041 is small, reducing the luminous flux of the system , cannot accurately detect weak airglow signals.

Utility model content

The purpose of the utility model is to overcome the shortcomings of the existing airglow imager, such as small detection field of view, narrow spectral range, mechanical focusing device, complex structure and operation of the imager, and low luminous flux of the imager, and provide a wide range Spectral non-focusing all-sky airglow imager. The imager can realize multi-channel all-sky airglow imaging economically and conveniently on the basis of ensuring a high light flux of the whole system, and realize high-precision all-sky airglow observation.

In order to achieve the above purpose, the utility model provides a wide-spectrum non-focusing all-sky airglow imager, which is special in that it includes an image-side telecentric fisheye lens, an object-side Telecentric imaging lenses and detectors;

A filter wheel is set between the fisheye lens and the imaging lens. There are multiple narrow-band filters with different wavelength bands and zero focal power on the filter wheel. The filter wheel can switch the narrow-band filter to the fisheye lens. focal plane;

The fisheye lens comprises a negative power front lens group and a positive power rear lens group, an aperture stop is arranged on the optical path between the front lens group and the rear lens group, and the aperture stop is positioned at the front focal plane of the rear lens group ; The imaging lens comprises a plurality of cemented mirrors formed by cementing a positive lens and a negative lens, the relative Abbe numbers of the positive lens and the negative lens are respectively denoted as A and B, |A-B|≥5, the positive lens and the negative lens The relative dispersion is recorded as C and D respectively, and C-D|≤0.001. The positive lens generally uses crown glass with a large Abbe number, and the negative lens generally uses flint glass with a small Abbe number.

Further, the rear lens group of the above-mentioned fisheye lens includes at least one cemented mirror formed by cementing a positive lens and a negative lens, and the relative Abbe numbers of the positive lens and the negative lens are respectively denoted as a and b, |a-b|≥5, The relative dispersion of the positive lens and the negative lens are denoted as c and d respectively, |c-d|≤0.001. The fisheye lens is equipped with a glued lens to optimize the axial chromatic aberration of the primary image plane of the fisheye lens, so that the overall image quality of the fisheye lens does not change when switching between different filter systems at the primary image plane.

Further, the above-mentioned imaging lens includes a first imaging lens, a third doubled mirror, a fourth doubled mirror, a fifth doubled mirror and an eighth imaging lens from left to right; the third doubled mirror consists of a double convex positive lens and The double-concave negative lens is glued together, the material used for the double-convex positive lens is H-FK61, and the material used for the double-concave negative lens is KF2; The lens is glued together, the material used for the positive lens is KF2, and the material used for the biconvex positive lens is H-FK61; the fifth cemented lens is made of double convex positive lens and double concave negative lens from left to right The material used for the lens is H-FK61, and the material used for the double-concave negative lens is KF2.

Further, the above-mentioned narrow-band filter is a glass plate; the first imaging lens of the imaging lens is a double-convex positive lens, and the eighth imaging lens is a double-convex positive lens; the narrow-band filter, the first imaging lens, and the eighth imaging lens adopt The materials are all H-ZLAF92.

Further, the front lens group of the above-mentioned fisheye lens includes the first front lens, the second front lens, the third front lens, the first cemented mirror and the sixth front lens from left to right; the first cemented mirror consists of The negative lens facing the diaphragm is glued together with the double-convex positive lens. The material used for the negative lens is KF2, and the material used for the double-convex positive lens is H-FK61. Three rear lenses; the second cemented lens from left to right is made of a double-concave negative lens and a double-convex positive lens. The material used for the double-concave negative lens is KF2, and the material used for the double-convex positive lens is H-FK61.

Further, the first front lens of the fisheye lens front lens group is a negative lens with a concave surface facing the diaphragm; the second front lens is a negative lens with a concave surface facing the diaphragm; the third front lens is a negative lens with a concave reverse diaphragm The sixth front lens is a double-convex positive lens; the third rear lens of the rear lens group is a double-convex positive lens; the materials used for the first front lens, the second front lens, the third front lens, and the sixth front lens are H -ZLAF92, H-FK61, H-ZF6, H-FK61; the material used for the third rear lens is H-FK61.

Further, the above-mentioned filter wheel includes 8 narrow-band filters with a size of 4 inches, and the center wavelengths of the 8 narrow-band filters are 427.8nm, 557.7nm, 578.0nm, 589.3nm, 598.5nm, 630.0nm, 777.4nm, 865.0nm. Driven by the motor of the filter wheel to rotate and switch, it can realize multi-channel observation in turn.

Further, the focal length of the fisheye lens is 35.35mm, the F# is 10.3, the F# of the imaging lens is 2.8, and the β is -0.2721.

Further, the distance between the front lens group and the rear lens group is 77.9 mm, the distance between the rear lens group and the narrow-band filter is 123.78 mm, and the distance between the narrow-band filter and the imaging mirror is 160 mm. The distance between the first front lens and the second front lens is 35.42mm, the distance between the second front lens and the third front lens is 97.91mm, the distance between the third front lens and the first doubled lens is 3.13mm, and the distance between the first doubled lens The distance from the sixth front lens is 5.38mm; the distance between the second doublet and the third rear lens is 157.66mm; the distance between the first imaging lens and the third doublet is 132.59mm, and the distance between the third doublet and the fourth doublet The distance between the fourth doublet and the fifth doublet is 2mm, and the distance between the fifth doublet and the eighth imaging lens is 5.33mm. The distance between the surface of the first front lens close to the object side and the focal plane of the imager optical system is 1099.42mm.

Further, the above-mentioned detectors are scientific grade CCD cameras.

Compared with the prior art, the utility model has the advantages of:

1. The narrow-band filter of the utility model is set on the primary image plane, which reduces the requirements on the surface quality of the filter; and the cemented mirror of the imaging mirror selects a specific glass material (such as KF2, H-FK61), which is beneficial to the whole system. The apochromatic optimization is carried out in the wide spectral range of the band (427.8~865nm), which not only eliminates the positional chromatic aberration of the edge light, but also forms apochromatic aberration for the light in the whole spectrum. That is to say, high-quality imaging is realized to meet the demand for detection of weak airglow radiation; the image plane focusing device is omitted, the complexity of the system is reduced, and the manufacturing cost of the imager is saved.

2. The utility model adopts a telecentric fisheye lens, which can make the principal rays of different fields of view perpendicular to the filter, so as to ensure that the imaging beam aperture angle on the primary image plane axis and the off-axis field of view are consistent, thereby ensuring the filter Uniformity of light sheet transmission; at the same time, it can also make the incident angle of incident light meet the bandwidth requirements of multiple filters of different bands in the filter wheel, and can realize multi-band and multi-channel observation.

3. The utility model increases the aperture of the primary image plane by simplifying the structure of the imager system, reducing the number of lenses and adopting a special telecentric fisheye lens, thereby increasing the effective relative aperture of the optical filter, and finally increasing the The luminous flux of the large system enables the imager to have higher detection capabilities.

Description of drawings

Fig. 1 is a schematic diagram of the system composition of an existing airglow imager;

Fig. 2 is a schematic diagram of the optical path structure of an existing airglow imager;

Fig. 3 is a schematic diagram of the optical path structure of an embodiment of the utility model airglow imager;

Fig. 4 is a transfer function diagram of the optical system of Fig. 3 embodiment at a spatial frequency of 371p/mm;

Fig. 5 is a spot diagram of the optical system of Fig. 3 embodiment;

FIG. 6 is a paraxial chromatic aberration curve of the optical system of the embodiment in FIG. 3 .

The description of each label in Figure 1 and Figure 2 is as follows:

01—fisheye lens, 02—diaphragm, 03—first imaging mirror, 04—filter wheel, 041—filter, 05—second imaging mirror, 06—CCD detector, 07—mechanical focusing device, 08—Computer;

The description of each label in Figure 3 to Figure 6 is as follows:

1—fisheye lens;

11—front lens group, 111—first front lens, 112—second front lens, 113—third front lens, 114—first cemented mirror, 115—sixth front lens, 116—aperture stop;

12—rear lens group, 121—the second cemented mirror, 122—the third rear lens;

2—narrow band filter;

3—imaging lens, 31—the first imaging lens, 32—the third doubled mirror, 33—the fourth doubled mirror, 34—the fifth doubled mirror, 35—the eighth imaging lens.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail.

This embodiment provides a wide-spectrum non-focusing all-sky airglow imager, including an image-space telecentric fisheye lens 1, an object-space telecentric imaging lens 3, and a detector (not shown) arranged in sequence from left to right along the same optical axis. icon). The detector can use a scientific grade CCD camera.

Referring to Fig. 3, a filter wheel (not shown) is arranged between the fisheye lens 1 and the imaging lens 3, and there are 8 narrow-band filters with different wavelength bands, zero focal power and a size of 4 inches on the filter wheel. 2, the filter wheel can switch the narrowband filter 2 to the focal plane of the fisheye lens 1;

The narrow-band filter 2 is a glass plate, and the material used is H-ZLAF92. The central wavelengths of the eight narrow-band filters 2 are 427.8nm, 557.7nm, 578.0nm, 589.3nm, 598.5nm, 630.0nm, 777.4nm , 865.0nm. The motor of the filter wheel is driven to rotate and switch to realize multi-channel observation in turn.

The main gas components and distribution heights corresponding to the detection bands of the 8 filters are shown in the table below.

The rear lens group 12 of the fisheye lens 1 includes at least one cemented mirror formed by cementing a positive lens and a negative lens, the absolute value of the relative Abbe number difference between the positive lens and the negative lens is ≥ 5, and the absolute value of the relative dispersion difference is ≤0.001. In the present embodiment, fisheye lens 1 comprises negative dioptric power front lens group 11 and positive dioptric power rear lens group 12, and the optical path between front lens group 11 and rear lens group 12 is provided with aperture stop 116, aperture stop 116 is located on the front focal plane of the rear lens group 12 . The front lens group 11 is mainly responsible for the field of view and the rear working distance; the rear lens group 12 belongs to the projection objective lens for short-distance imaging, which bears a large deflection angle, and provides partial aberrations to balance with the residual aberration of the front lens group 11.

The front lens group 11 of fisheye lens 1 comprises the first front lens 111, the second front lens 112, the third front lens 113, the first cemented mirror 114 and the sixth front lens 115 from left to right; The first front lens 111 is The material of the negative lens with the concave surface to the diaphragm is H-ZLAF92; the second front lens 112 is the negative lens with the concave surface to the diaphragm, and the material used is H-FK61; the third front lens 113 is the negative lens with the concave surface of the diaphragm. The material used for the negative lens is H-ZF6; the first cemented mirror 114 is glued from left to right by a negative lens facing the diaphragm and a double-convex positive lens. The material used for the negative lens is KF2, and the double-convex positive lens is made of The material used is H-FK61; the sixth front lens 115 is a biconvex positive lens, and the material used is H-FK61.

The rear lens group 12 includes a second cemented mirror 121 and a third rear lens 122 from left to right; the second cemented mirror 121 is formed by cementing a double-concave negative lens and a double-convex positive lens from left to right, and the double-concave negative lens adopts The material is KF2, and the material used for the biconvex positive lens is H-FK61. The third rear lens 122 is a biconvex positive lens, and the material used is H-FK61.

The imaging lens 3 includes multiple cemented lenses formed by cementing a positive lens and a negative lens. The absolute value of the relative Abbe number difference between the positive lens and the negative lens is ≥5, and the absolute value of the relative dispersion difference is ≤0.001. In this embodiment, the imaging lens 3 includes a first imaging lens 31 , a third doubled lens 32 , a fourth doubled lens 33 , a fifth doubled lens 34 and an eighth imaging lens 35 from left to right. The first imaging lens 31 is a double-convex positive lens, and the material used is H-ZLAF92; the third cemented lens 32 is formed by cementing a double-convex positive lens and a double-concave negative lens from left to right, and the material used for the double-convex positive lens is H-FK61, the material used for the double-concave negative lens is KF2; the fourth cemented mirror 33 is glued from left to right by a positive lens facing the diaphragm and a double-convex positive lens. The material used for the positive lens is KF2, which is double-convex. The material used for the positive lens is H-FK61; the fifth cemented mirror 34 is formed by cementing a double convex positive lens and a double concave negative lens from left to right, the material used for the double convex positive lens is H-FK61, and the double concave negative lens is made of The material is KF2; the eighth imaging lens 35 is a biconvex positive lens, and the material used is H-ZLAF92.

After the incident light passes through the fisheye lens 1 and reaches the narrow-band filter 2 at its focal plane, the narrow-band filter 2 is used to extract the intensity information of the airglow radiation in the characteristic height region of the middle and upper atmosphere; a high-sensitivity detector is used to record the airglow in the whole sky Radiation intensity distribution image. By analyzing the images with a computer, the observed data of atmospheric fluctuations in the airglow height area can be obtained.

The specific structural parameters of the optical system of the imager in this embodiment are shown in the table below.

The F# of the optical system of the imager in this embodiment is 2.8; the focal length is 9.63mm; the image height is 13.824mm, and the field of view is 180°; it can be adapted to a CCD imaging device with a pixel number of 2048×2048 and a pixel size of 13.5um ; The focal length of the fisheye lens is 35.35mm, and the F# is 10.3. The imaging lens has an F# of 2.8 and a beta of -0.2721.

Referring to Fig. 4, at the spatial frequency of 37lp/mm, the MTF value of the system is 0.82 higher in both the sagittal plane (S) and the meridional plane (T), which is close to the diffraction limit and has excellent imaging quality.

The spot diagram in Figure 5 reflects the size of the diffuse spot imaged by the system on the image plane. As shown in Figure 5, the root mean square radius of dispersion on the axis is 2.289um, and the root mean square radius of the full field of view is 3.613um. The optical system has uniform distribution of imaging quality in the entire field of view.

It can be seen from Figure 6 that the secondary spectral chromatic aberration is about 0.048mm, and its maximum focal shift is within five times of the diffraction limit change, with a small maximum focal shift, which meets the requirements of the secondary spectral and can better Realize the correction of the secondary spectrum.

In summary, this implementation uses the image-space telecentric fisheye lens, the narrow-band filter with zero focal power, the object-space telecentric imaging lens, and cooperates with the detector to realize atmospheric airglow radiation as a tracer, and the whole sky multi- Imaging observations of channel airglow.

The above is only a description of the preferred implementation of the utility model, and does not limit the technical solution of the utility model thereto. Any known deformation made by those skilled in the art on the basis of the main technical concept of the utility model belongs to this utility model. The technical category to be protected by the utility model.

Claims (10)

1. A wide-spectrum band non-focusing all-sky airglow imager is characterized in that it comprises an image-space telecentric fisheye lens (1) and an object-space telecentric imaging lens (3) arranged successively from left to right along the same optical axis ) and detectors; A filter wheel is arranged between the fisheye lens (1) and the imaging lens (3), and a plurality of narrow-band filters (2) with different wavelength bands and zero focal power are arranged on the filter wheel, and the filter wheel can filter the narrow-band The optical filter (2) is switched to the focal plane of the fisheye lens (1); The fisheye lens (1) comprises a negative power front lens group (11) and a positive power rear lens group (12), and the optical path between the front lens group (11) and the rear lens group (12) is provided with The aperture stop (116), the aperture stop (116) is positioned at the front focal plane of the rear lens group (12); The imaging lens (3) includes a plurality of cemented lenses formed by cementing positive lenses and negative lenses, the absolute value of the relative Abbe number difference between the positive lens and the negative lens is ≥5, and the absolute value of the relative dispersion difference is ≤ 0.001. 2. A kind of wide-spectrum non-focusing all-sky airglow imager according to claim 1, characterized in that: the rear lens group (12) of the fisheye lens (1) comprises at least one positive lens and a negative lens For the cemented doublet, the absolute value of the relative Abbe number difference between the positive lens and the negative lens is ≥5, and the absolute value of the relative dispersion difference is ≤0.001. 3. A wide-spectrum non-focusing all-sky airglow imager according to claim 1 or 2, characterized in that: the imaging lens (3) comprises a first imaging lens (31), a third imaging lens (31) from left to right. Doubled mirror (32), the fourth doubled mirror (33), the fifth doubled mirror (34) and the eighth imaging lens (35); The third cemented mirror (32) is formed from left to right by a double-convex positive lens and a double-concave negative lens. The material used for the double-convex positive lens is H-FK61, and the material used for the double-concave negative lens is KF2; The fourth cemented mirror (33) is glued from left to right by a positive lens facing the diaphragm and a biconvex positive lens. The material that the positive lens adopts is KF2, and the material that the biconvex positive lens adopts is H-FK61; The fifth cemented mirror (34) is formed by cementing a biconvex positive lens and a biconcave negative lens from left to right. The material used for the biconvex positive lens is H-FK61, and the material used for the biconcave negative lens is KF2. 4. a kind of broadband non-focusing all-sky airglow imager according to claim 3, is characterized in that: described narrow-band optical filter (2) is glass plate; The first imaging lens of imaging lens (3) ( 31) is a biconvex positive lens, and the eighth imaging lens (35) is a biconvex positive lens; The narrow-band filter (2), the first imaging lens (31) and the eighth imaging lens (35) are all made of H-ZLAF92. 5. A wide-spectrum non-focusing all-sky airglow imager according to claim 3, characterized in that: the front lens group (11) of the fisheye lens (1) comprises the first front lens from left to right (111), the second front lens (112), the third front lens (113), the first doubled mirror (114) and the sixth front lens (115); The first cemented mirror (114) is glued from left to right by a negative lens facing the diaphragm and a double-convex positive lens. The material used for the negative lens is KF2, and the material used for the double-convex positive lens is H-FK61; The rear lens group (12) includes a second cemented mirror (121) and a third rear lens (122) from left to right; The second cemented mirror (121) is formed from a double-concave negative lens and a double-convex positive lens by cementing from left to right. The material used for the double-concave negative lens is KF2, and the material used for the double-convex positive lens is H-FK61. 6. A wide-spectrum non-focusing all-sky airglow imager according to claim 5, characterized in that: the first front lens (111) of the fisheye lens (1) front lens group (11) is concave The negative lens facing the diaphragm; the second front lens (112) is a concave negative lens facing the diaphragm; the third front lens (113) is a negative lens of a concave reverse diaphragm; the sixth front lens (115) is biconvex positive lens; The third rear lens (122) of the rear lens group (12) is a biconvex positive lens; The materials used for the first front lens (111), the second front lens (112), the third front lens (113), and the sixth front lens (115) are H-ZLAF92, H-FK61, H-ZF6, H- FK61; the material adopted by the third rear lens (122) is H-FK61. 7. A kind of broadband non-focusing all-sky airglow imager according to claim 6, is characterized in that: described filter wheel comprises 8 narrow-band filters (2) that size is 4 inches, 8 The central wavelengths of the narrowband filters (2) are 427.8nm, 557.7nm, 578.0nm, 589.3nm, 598.5nm, 630.0nm, 777.4nm, 865.0nm respectively. 8. a kind of wide-spectrum non-focusing all-sky airglow imager according to claim 7, is characterized in that: the focal length of described fisheye lens (1) is 35.35mm, and F# is 10.3, and described imaging lens (3 ) has an F# of 2.8 and a β of -0.2721. 9. a kind of wide-spectrum band non-focusing all-sky airglow imager according to claim 8, is characterized in that: described front lens group (11) and rear lens group (12) interval are 77.9mm, The distance between the rear lens group (12) and the narrow band filter (2) is 123.78mm, The interval between the narrow band filter (2) and the imaging mirror is 160mm, The distance between the first front lens (111) and the second front lens (112) is 35.42mm, The distance between the second front lens (112) and the third front lens (113) is 97.91mm, The distance between the third front lens (113) and the first doubled mirror (114) is 3.13 mm, The distance between the first doubled mirror (114) and the sixth front lens (115) is 5.38mm; The distance between the second cemented mirror (121) and the third rear lens (122) is 157.66mm; The distance between the first imaging lens (31) and the third doubled mirror (32) is 132.59mm, The interval between the third doubled mirror (32) and the fourth doubled mirror (33) is 7.46mm, The interval between the fourth doubled mirror (33) and the fifth doubled mirror (34) is 2mm, The distance between the fifth doubled mirror (34) and the eighth imaging lens (35) is 5.33mm; The distance between the surface of the first front lens (111) close to the object side and the focal plane of the imager optical system is 1099.42mm. 10. A wide-spectrum non-focusing all-sky airglow imager according to claim 9, characterized in that: the detector is a scientific grade CCD camera.