Modeling of a radial laminated grin lens; design and achievable performances of a dual-band infrared triplet with such lens

Грейсух Г.И., Левин И.А., Ежов Е.Г. Моделирование ламинированной радиально-градиентной линзы; расчёт и достижимые характеристики двухдиапазонного инфракрасного триплета с такой линзой // Оптический журнал. 2024. Т. 91. № 10. С. 34–42. http://doi.org/10.17586/1023-5086-2024-91-10-34-42

Greisukh G.I., Levin I.A., Ezhov E.G. Modeling of a radial laminated grin lens; design and achievable performances of a dual-band infrared triplet with such lens [in Russian] //Opticheskii Zhurnal. 2024. V. 91. № 10. P. 34–42. http://doi.org/10.17586/1023-5086-2024-91-10-34-42

Subject of the study. The initial scheme of the optical system, including thin homogeneous lenses and an infinitely thin model of a thick radial gradient-index lens, as well as a high-aperture dual-band infrared triplet calculated using this initial scheme. Purpose of the study. To present the calculation stages of an optical system with a coaxial laminated radial gradient-index lens and demonstrate the achievable performances of a high-aperture dual-band infrared objective consisting of two homogeneous and one radial gradient-index lens. The research method. Theoretical analysis, computer modeling and optimization using the ZEMAX optical design program. The main results. It is shown that the proposed infinitely thin model of a coaxial laminated radial gradient-index lens, having the same optical power and chromatic focal shift as the thick prototype, together with thin homogeneous lenses separated by air gaps, can be used as the initial scheme of the optical system being developed. At the same time, if the distribution of the refractive index of the gradient-index lens is known, then the best combination of optical materials of homogeneous lenses and the ratio of optical powers of all elements of the scheme can be obtained from the condition of achromatization, apochromatization or superchromatization by repeatedly solving the corresponding system of equations. The effectiveness of the proposed approach and the possibility of achieving high optical performances in a dual-band infrared triplet consisting of two homogeneous and one gradient-index lenses are demonstrated by the example of designing a system with a coaxially laminated radial gradient-index lens. The combination of brands of new chalcogenide glasses for the composite material of this lens was chosen based on the condition of achieving the required distribution of the refractive index. This distribution itself was obtained when designing a triplet of the medium (3–5 μm) infrared range. The layout, design parameters and optical performance of the calculated dual-band (3.5–5 and 8–11.9 μm) triplet are presented. Its focal length is 40 mm, F-number is 0.98 and the numerical aperture in the image space is 0.45. Within the angular field of view of 19.5º, this triplet forms an image with a contrast of 0.54 at a spatial frequency of 30 mm–1. Its distortion modulus does not exceed 0.4%. Practical significance. The results of this study open up the possibility of creating simple high-aperture dual-band infrared objectives based on coaxially laminated radial gradient-index lenses.

this work was supported by the Russian Science Foundation, Project № 20–19–00081.