Collimation of an anastigmat objective with three off-axis aspherical mirrors

Egorov, M.S., Lebedev, O.A., Rezunkov, Y.A., Solk, S.V., Stepanov, V.V.

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Publication in Journal of Optical Technology

For Russian citation (Opticheskii Zhurnal):

Егоров М.С., Лебедев О.А., Резунков Ю.А., Солк С.В., Степанов В.В. Проблемы юстировки объектива-анастигмата из трех внеосевых асферических зеркал // Оптический журнал. 2022. Т. 89. № 5. С. 41–53 . http://doi.org/10.17586/1023-5086-2022-89-05-41-53

Egorov M.S., Lebedev A.O., Rezunkov Yu.A., Solk S.V., Stepanov V.V. Collimation of an anastigmat objective with three off-axis aspherical mirrors [in Russian] // Opticheskii Zhurnal. 2022. V. 89. № 5. P. 41–53 . http://doi.org/10.17586/1023-5086-2022-89-05-41-53

For citation (Journal of Optical Technology):

M. S. Egorov, O. A. Lebedev, Yu. A. Rezunkov, S. V. Solk, and V. V. Stepanov, "Collimation of an anastigmat objective with three off-axis aspherical mirrors," Journal of Optical Technology. 89(5), 277-285 (2022). https://doi.org/10.1364/JOT.89.000277

Abstract:

Subject of study. Objectives for a wide variety of wavelengths from the visible to the mid-infrared are currently under development for use in small spacecraft. Because of advantages such as the ability to operate over a broad spectral range, the use of low-weight mirror fabrication technologies, and their smaller size, reflective objectives are preferred for space-based applications. This paper discusses the collimation of reflective objectives with off-axis aspheric mirrors (objectives with an off-axis field of view). Collimation of reflective objectives has traditionally been performed using interferometers operating in autocollimation mode, with collimation being verified using compensatory designs. In the case of compact multimirror objectives, it is not always possible to find space for the collimation equipment (either an interferometer with an auxiliary mirror or a holographic compensator). Method. An alternative technique was developed for sequential element-by-element collimation of a prototype multimirror objective, based on monitoring focal-spot shapes and comparing them against a calculated focal-spot shape. We discuss collimation of a four-mirror anastigmat objective, in which the first mirror is an off-axis concave ellipsoid, the second mirror is an off-axis convex hyperboloid, the third mirror is a flat, and the fourth mirror is an off-axis concave ellipsoid. The objective was collimated using a He-Ne laser (wavelength 0.63 µm), with the distribution of light in the focal spot being recorded with a television camera; collimation was verified using a continuously tunable CO laser (emission wavelength of 5.415 µm) and an HF laser (emission wavelength of 2.8–3.2 µm), and the distribution of light in the focal spots was measured with an InSb photodetector array. The focal spots were inspected using a microscope whose object plane coincided with the focal plane of the element being collimated. The entrance aperture of the objective was illuminated by a collimated laser beam parallel to the collimation axis. The quality of collimation was determined by comparing the shapes of the observed focal spots against those theoretically calculated for an ideally collimated objective. Main results. Our research revealed that a test collimation technique based on the shape of the focal spots is insufficiently sensitive to miscollimation of individual mirrors and scattering within a multiple-mirror system. In addition, the technique fails to provide the required collimation accuracy. Practical significance. The proposed technique will be used to develop specialized optoelectronic instrumentation for continuous, step-by-step verification of all optical elements in a four-mirror anastigmat to sufficient accuracy for collimation.

Keywords:

Mirror lenses, multi-mirror systems, off-axis (decentralized) systems, alignment, four-mirror off-axis anastigmat, laser focal spot, dissection

OCIS codes: 220.1250, 230.4040, 120.4825

References:

1. A. M. Savitski˘ı and M. N. Sokol’ski˘ı, “Optical systems of objectives for small spacecraft,” J. Opt. Technol. 76, 657–661 (2009) [Opt. Zh. 76(10), 83–88 (2009)].
2. L. G. Cook, “Compact four-mirror anastigmat telescope,” U.S. patent 6767103 (24 July 2004).
3. J. Contzen, J. Muylaert, G. Koppenwallner, V. Lappas, and N. Voronka, “Scientific aspects of space debris re-entry,” in ISTC Workshop on Mitigation of Space Debris (Von Karman Institute for Fluid Dynamics, 2010), pp. 39–75.
4. N. K. Artyukhina, “Principles for the development of multimirror designs with decentered components,” Visn. NTUU “KPI” Ser. Pryladobuduvannia (45), 44–53 (2013).
5. L. G. Cook, “Compact four-mirror anastigmat telescope,” U.S. patent application WO 03/083549 A1 (22 March 2002).
6. K. D. Butylkina, G. E. Romanova, V. N. Vasil’ev, and G. G. Valyavin, “Investigation of three-mirror objectives for Earth remote sensing operating with an off-axis field of view,” J. Opt. Technol. 88(9), 497–502 (2021) [Opt. Zh. 88(9), 20–27 (2021).
7. V. I. Zavarzin, A. V. Li, and S. A. Morozov, “Technique for assembly and collimation of catadioptric objectives with an eccentric image field,” Inzh. Zh.: Nauka Innovatsii 7(19) (2013).
8. S. A. Arkhipov, V. I. Zavarzin, V. A. Malykhin, and S. A. Morozov, “Collimation and certification of a long-focal-length three-mirror objective with an eccentric image field,” Vestn. Mosk. Gos. Tekh. Univ. im. N. E. Baumana Ser. “Priborostr.” (4), 24–36 (2009).
9. N. P. Larionov, “Adjustment of two-mirror collimators with off-axis aspheric mirrors,” J. Opt. Technol. 74(6), 401–406 (2007) [Opt. Zh. 74(6), 37–44 (2007)].
10. V. I. Venzel’, A. V. Gorelov, and A. S. Gridin, “Interferometric technique for collimation of a two-mirror objective with aspheric components,” Russian Federation patent 2561018 (2015).
11. N. P. Larionov, A. V. Lukin, and A. A. Nyushkin, “Monitoring small-scale aspheric optics by means of synthesized holograms,” J. Opt. Technol. 78(4), 270–272 (2011) [Opt. Zh. 78(4), 61–64 (2011)].
12. D. D. Maksutov, Fabrication and Study of Astronomical Optics, 2nd ed. (Nauka, Moscow, 1984).
13. A. R. Agachev, N. P. Larionov, A. V. Lukin, T. A. Mironova, A. A. Nyushkin, D. V. Protasevich, and R. A. Rafikov, “Computer-generated holographic optics,” J. Opt. Technol. 69(12), 871–878 (2002) [Opt. Zh. 69(12), 23–32 (2002)].
14. N. P. Larionov, A. V. Lukin, A. A. Nyushkin, and R. R. Khodzhiev, “Monitoring convex aspheric surfaces using axial synthesized holograms,” J. Opt. Technol. 74(6), 407–411 (2007) [Opt. Zh. 74(6), 45–50 (2007)].
15. https://www.edinst.com/us/products/co-gas-laser-5-2-%ce%bcm-6-0-%ce%bcm/.
16. Yu. A. Anan’ev, Optical Cavities and Laser Beams (Nauka, Moscow, 1990).
17. Zemax manual (Radiant Zemax Inc., 2005).