CN112034605A - Catadioptric Golay3 sparse aperture optical system - Google Patents
Catadioptric Golay3 sparse aperture optical system Download PDFInfo
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- CN112034605A CN112034605A CN202010940813.4A CN202010940813A CN112034605A CN 112034605 A CN112034605 A CN 112034605A CN 202010940813 A CN202010940813 A CN 202010940813A CN 112034605 A CN112034605 A CN 112034605A
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- optical system
- golay3
- reflecting mirror
- sparse aperture
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/0804—Catadioptric systems using two curved mirrors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/0804—Catadioptric systems using two curved mirrors
- G02B17/0808—Catadioptric systems using two curved mirrors on-axis systems with at least one of the mirrors having a central aperture
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/0804—Catadioptric systems using two curved mirrors
- G02B17/0812—Catadioptric systems using two curved mirrors off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
Abstract
The invention belongs to the field of optical instruments, and provides a catadioptric Golay3 sparse aperture optical system for solving the technical problems of small field angle and small filling factor of the conventional coaxial sparse aperture optical system, which comprises: the wide-angle sparse aperture optical system is characterized in that a Golay3 array main reflecting mirror with a hyperboloid surface shape, a secondary reflecting mirror with a hyperboloid surface shape and a correction lens group with a spherical surface shape are adopted, the full field angle of the sparse aperture optical system is 1 degree multiplied by 1 degree, the F number is 5, the diameter of an entrance pupil is 300mm, the structure is compact, the applicable waveband is visible light, the main reflecting mirror adopts a Golay3 array structure with a filling factor of 40.3%, the aperture of the secondary reflecting mirror is smaller than that of a secondary reflecting mirror, the correction lens group adopts a positive and negative positive structure adopting H-ZK11 glass (all clear), and three lenses are meniscus lenses. The invention is suitable for imaging remote dark and weak objects.
Description
Technical Field
The invention belongs to the field of optical instruments, and relates to a catadioptric optical system.
Background
The invention aims to provide a refraction and reflection type Golay3 sparse aperture optical imaging system, wherein the sparse aperture imaging system is formed by combining a plurality of sub-apertures according to a certain rule to replace a large aperture area, and the aperture of each sub-aperture is much smaller than the whole large aperture, so that the sparse aperture can not only overcome a series of difficulties caused by too large aperture of the optical system, but also obtain the spatial resolution equivalent to that of the large aperture optical system. For example, the civil astronomical telescope used by astronomical amateurs is generally limited to 200mm caliber, and the price of the astronomical telescope with the caliber larger than 200mm is hundreds times that of the astronomical telescope with the caliber smaller than 200 mm. The full aperture is replaced by the sparse aperture, so that hundreds of times of economic benefits are realized at cost which is dozens of times or even several times, and the research significance of the sparse aperture is fully shown. In practical application, most of the sparse aperture imaging system is of a two-reflector telescope structure (composed of a main reflector and a secondary reflector), and the main reflector is composed of small sub-mirrors in a combined mode. In terms of specific structural selection of the sparse aperture, Golay3 sparse aperture is most widely used due to its simple structure.
Usually, the main reflecting mirror of the sparse aperture telescope is spherical, namely the cone coefficient of the main reflecting mirror is 0, so that the curvature radiuses of all the sub-mirrors and the curvature radiuses of the main reflecting mirror are the same, the batch production of the sub-mirrors is easy, and meanwhile, the testing and the assembly and adjustment of all the sub-mirrors are more convenient. However, the spherical surface shape also causes relatively serious spherical aberration to the whole system, so that the secondary reflector must increase the deformation thereof to counteract the spherical aberration introduced by the primary reflector, and meanwhile, the whole system is also subjected to off-axis image differences such as coma and astigmatism, which severely limit the field of view of the whole system. The literature, "design, processing and inspection of optical aspheric surfaces" ([ M ] pandheye, published by suzhou university, 2004) states that even if the primary and secondary mirrors both use quadric surfaces, all primary aberrations cannot be eliminated for a two-mirror telescope system, and two methods are generally used in order to improve the image quality of the system and increase the field of view. One, more complex surface shapes, such as Zernike surfaces, are used. Secondly, adding corrective glasses.
The document "research on the structural design and adjustment method of a subaperture mosaic imaging system" ([ D ] high celestial elements, 2009, doctrine and university thesis) discloses a real object device of a sparse aperture optical imaging system, wherein a main reflector of the sparse aperture optical imaging system is a spherical reflector, a secondary reflector is a flat ellipsoid reflector, and after four correction mirrors are added, the field angle is only +/-0.063 degrees. The document 'design of Golay3 telescope system' ([ J ] optical precision engineering, 2011,19(12): 2877-; in addition, the field angle of the sparse aperture telescope is small, the field angle is +/-0.15 degrees after the spherical correction mirror is added, and the maximum filling factor is 22.2 percent. The document ' study of a three-sub-mirror sparse aperture two-reflection telescope system ' ([ D ] Leamandon, 2015, Master ' thesis) also discloses a design of a Golay3 sparse aperture telescope, wherein the primary and secondary reflecting mirror surfaces of the telescope are hyperboloid surfaces, the visual field is +/-0.5 degrees after a spherical correcting mirror is added, but the telescope does not consider the blocking of the primary reflecting mirror by the secondary reflecting mirror, and does not consider chromatic aberration when a lens correction is introduced, and the two correcting mirrors adopt unconventional glass and are expensive.
Disclosure of Invention
In order to solve the problems of small field angle and small filling factor of a coaxial sparse aperture optical system in the prior art, a catadioptric Golay3 sparse aperture optical system is provided.
The refraction and reflection type Golay3 sparse aperture optical system has a working waveband of visible light, and comprises a main reflecting mirror with a hyperboloid surface, a secondary reflecting mirror with a hyperboloid surface and a correction lens group; the approximately parallel light rays at the remote position sequentially pass through the main reflector, the secondary reflector and the correction lens group and are focused on an image plane; the main reflecting mirror with the hyperboloid surface is composed of a Golay3 array, the caliber of the secondary reflecting mirror is smaller than that of the secondary reflecting mirror, and the correcting lens group sequentially comprises a positive meniscus lens, a negative meniscus lens, a positive meniscus lens, a negative meniscus lens and a positive meniscus lens along the positive direction of an optical axis.
Preferably: the primary mirror employs a Golay3 array structure with a fill factor of 40.4%. As the fill factor increases, the Modulation Transfer Function (MTF) is large in value over a large spatial frequency range (MTF is above 0.4 at the nyquist frequency (50 lp/mm)), and direct imaging over a higher spatial frequency range can be achieved than with a small fill factor.
Preferably: the length of the catadioptric Golay3 sparse aperture optical system is comparable to the aperture of the primary mirror. The whole optical system has compact structure and small volume. If the method is applied to a space-based system, the transportation cost can be reduced.
Preferably: the optical system has a total field angle of 1 ° × 1 °, an F number of 5, an entrance pupil diameter of 300mm, and an applicable wavelength band of visible light (F, d, C). Compared with the existing coaxial sparse aperture optical system, the field angle is obviously improved, and a wider space range can be seen. Compared with the existing coaxial sparse aperture optical system, the F number is obviously reduced, and dark and weak objects can be imaged.
Preferably: the aperture of the secondary reflector of the optical system is smaller than that of the secondary reflector. The purpose of the sparse aperture is to replace the large primary mirror with a small secondary mirror, thereby reducing cost. If the aperture of the secondary mirror is large, the manufacturing cost of the system cannot be effectively reduced.
Preferably: the correcting lens group adopts a positive and negative structure of H-ZK11 glass (Chengdu Guangming), and the three lenses are meniscus lenses. Glass H-ZK11 is the recommended brand of Dougenming company: the comprehensive performance is excellent, the brand of the stock exists for a long time, the relative cost is 1, and the price of the correction lens group is low. And a positive and negative structure similar to the three-piece photographic lens is adopted, so that the field of view of the system is increased.
Advantageous effects
The invention has the characteristics of large visual field, large relative aperture and large filling factor, and is suitable for imaging remote dark and weak objects in a visible light range. And the whole system is compact in structure, and the total length of the system is only 308 mm. The correcting lens group structure made of the same material is adopted, so that the aberration of the whole system is effectively balanced, and the imaging quality is good.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic diagram of a folded-mirror Golay3 sparse aperture optical system according to the present invention;
FIG. 2 is a schematic diagram of the primary mirror structure of the catadioptric Golay3 sparse aperture optical system of the present invention;
FIG. 3 is a schematic diagram of a corrective lens assembly of a catadioptric Golay3 sparse aperture optical system of the present invention;
FIG. 4 is a schematic view of field curvature and distortion of a catadioptric Golay3 sparse aperture optical system of the present invention;
fig. 5 is a modulation transfer function diagram of the catadioptric Golay3 sparse aperture optical system of the present invention.
Reference numerals
The optical lens comprises a main reflecting mirror 1, a secondary reflecting mirror 2, a correcting lens group 3, an image plane 4, a first meniscus lens 5, a second meniscus lens 6 and a third meniscus lens 7.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
A refraction and reflection type Golay3 sparse aperture optical imaging system is shown in figure 1, the working waveband is visible light, the optical system comprises a main reflecting mirror 1 with a hyperboloid surface, a secondary reflecting mirror 2 with a hyperboloid surface and a correction lens group 3; the light rays sequentially pass through the main reflector, the secondary reflector and the correction lens group and are focused on the image plane 4; the main reflecting mirror with the hyperboloid surface is composed of a Golay3 array, the caliber of the secondary reflecting mirror is smaller than that of the secondary reflecting mirror, and the length of the system is equivalent to that of the secondary reflecting mirror; the correcting lens group sequentially comprises a positive, a negative and a positive first meniscus lens 5, a second meniscus lens 6 and a third meniscus lens 7 along the positive direction of an optical axis.
A catadioptric Golay3 sparse aperture optical imaging system comprises a primary reflector, a secondary reflector and a correcting lens group. The primary reflector is a concave hyperboloid, the secondary reflector is a convex hyperboloid, the correction lens group is a positive and negative positive structure made of H-ZK11 glass (Chengdu Guangming), and the three lenses are meniscus lenses. The optical system belongs to the category of free-form surface optical systems because each sub-mirror has no non-rotational symmetry in surface shape. The light rays firstly enter a main reflector adopting a Golay3 sparse aperture array, the main reflector reflects the light rays to a secondary reflector, and the secondary reflector reflects the light rays to sequentially pass through three correction lenses and finally converge on an image surface. The full field angle of the optical system is 1 degree multiplied by 1 degree, the F number is 5, the diameter of an entrance pupil is 300mm, the applicable wave band is visible light (F, d and C), the total length of the system is 308mm (the structure is compact, the volume of the system is small), and the size of an image detector pixel is 10 mu m.
The specific design method is as follows: a Cassegrain system is adopted as an initial structure, and the curvature radius of the primary and secondary reflectors, the distance between the primary and secondary reflectors and the distance between the secondary reflectors and the image surface are calculated according to a paraxial imaging formula (Gaussian imaging formula). This initial structure was substituted into commercial optical design software Zemax and the primary mirrors were replaced with a Golay3 sparse aperture array according to the primary and secondary mirror obscuration, spherical and coma were eliminated with the conic coefficients of the primary and secondary mirrors and a corrective lens group with power of 0 was added near the image plane. In order to ensure that the chromatic aberration of the system is sufficiently small, three separate lenses of the same material are used for achromatization. And finally, ensuring the system structure by utilizing an evaluation function, taking the radius of the point list as an optimization target, and setting all the curvature radii, the thicknesses and the conical coefficients of the primary and secondary reflectors as variables to eliminate the residual aberration of the system. The first meniscus lens is arranged in the optical axis direction, wherein the side facing an object side is taken as the front side, the side facing an image side is taken as the back side, the object side of the first meniscus lens is taken as the front surface, and the image side of the first meniscus lens is taken as the back surface; one object side of the second meniscus lens is a front surface, and the other image side of the second meniscus lens is a rear surface; the object side of the third meniscus lens is the front surface, and the image side is the back surface, and the detailed parameters of the finally obtained system are shown in table 1.
TABLE 1
The parameters of the optical system can also be scaled as desired on the basis of said table 1 as a whole.
Fig. 2 shows an array distribution of the main mirrors, the diameter of the circle of encirclement (entrance pupil diameter) being 300mm, and the three sub-mirrors are distributed in a Golay3 array, each sub-mirror having a diameter of 110 mm. The filling factor is 40.3%, and the actual clear aperture is 190.5 mm.
As shown in FIG. 3, the correcting lens group structure is integrally distributed in positive and negative positive directions, three lenses are meniscus lenses made of H-ZK11 glass which are all bright, and the correcting lens group reduces the primary monochromatic aberration of the system and has small chromatic aberration in a visible light range. Glass H-ZK11 is the recommended brand of Dougenming company: the comprehensive performance is excellent, the brand of the stock exists for years, and the relative cost is 1.
As shown in fig. 4, the field curvature and distortion of the whole optical system have a maximum sagittal field curvature of 0.0567mm, a maximum meridional field curvature of 0.0446mm, and a maximum distortion of 0.0632%. The field curvature and distortion are small and can be ignored, and the image has almost no deformation.
As shown in fig. 5, which is a Modulation Transfer Function (MTF) of the entire optical system, it can be seen that the MTF of each field of view is close to the diffraction limit, there is no null point in the cutoff frequency range, and the MTF values are each greater than 0.4 at the nyquist frequency (50lp/mm), and the imaging quality is excellent. Defining an equivalent caliber of
Wherein DmaxDiameter of circular aperture corresponding to meridian cut-off frequency, DminThe aperture of the circular aperture corresponding to the cutoff frequency in the sagittal direction can be calculated to be 234 mm. The telescope system with the equivalent caliber of 234mm is obtained by the through caliber of 190.5mm, and the telescope system has obvious benefit on reducing the system quality.
The foregoing is merely illustrative of the technical concepts and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (7)
1. A catadioptric Golay3 sparse aperture optical system; the working wave band is visible light, and the device is characterized in that: the device comprises a main reflecting mirror with a hyperboloid surface, a secondary reflecting mirror with a hyperboloid surface and a correction lens group; the light rays sequentially pass through the main reflector, the secondary reflector and the correction lens group and are focused on an image plane; the main reflecting mirror with the hyperboloid surface is composed of Golay3 arrays, and the caliber of the secondary reflecting mirror is smaller than that of the secondary reflecting mirror; the correction lens group sequentially comprises a positive, a negative and a positive first meniscus lens, a second meniscus lens and a third meniscus lens along the positive direction of the optical axis.
2. The catadioptric Golay3 sparse aperture optical system of claim 1, wherein: the full field angle of the optical system is 1 ° × 1 °.
3. The catadioptric Golay3 sparse aperture optical system of claim 1, wherein: the F-number of the optical system was 5.
4. The catadioptric Golay3 sparse aperture optical system of claim 1, wherein: the entrance pupil diameter of the optical system is 300 mm.
5. The catadioptric Golay3 sparse aperture optical system of claim 1, wherein: the primary mirror employs a Golay3 array structure with a fill factor of 40.3%.
6. The catadioptric Golay3 sparse aperture optical system of claim 1, the object side of the first meniscus lens being a front surface and the image side being a back surface, with the object side facing front and the image side being back, along the optical axis; one object side of the second meniscus lens is a front surface, and the other image side of the second meniscus lens is a rear surface; one object side of the third meniscus lens is a front surface, and the other image side of the third meniscus lens is a rear surface; the method is characterized in that: the parameters of the optical system are shown in Table 1
TABLE 1
7. The catadioptric Golay3 sparse aperture optical system of claim 6, wherein: the parameters of the optical system are scaled globally on the basis of said table 1.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113568152A (en) * | 2021-07-27 | 2021-10-29 | 西安航空学院 | High-resolution optical system based on catadioptric splicing primary mirror |
| CN113568151A (en) * | 2021-07-27 | 2021-10-29 | 西安航空学院 | Large-caliber splicing primary mirror optical system for realizing high resolution |
| CN113655608A (en) * | 2021-08-13 | 2021-11-16 | 西安航空学院 | Visible or infrared high-resolution optical system based on sparse aperture |
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2020
- 2020-09-09 CN CN202010940813.4A patent/CN112034605A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113568152A (en) * | 2021-07-27 | 2021-10-29 | 西安航空学院 | High-resolution optical system based on catadioptric splicing primary mirror |
| CN113568151A (en) * | 2021-07-27 | 2021-10-29 | 西安航空学院 | Large-caliber splicing primary mirror optical system for realizing high resolution |
| CN113655608A (en) * | 2021-08-13 | 2021-11-16 | 西安航空学院 | Visible or infrared high-resolution optical system based on sparse aperture |
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