DETERMINATION OF THE MODULATION TRANSFER FUNCTION OF INFRARED OBJECTIVES
V.V. Vasiliev, A.V. Vishnyakov, G.Yu. Sidorov, V.A. Stuchinsky
Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: characterization of IR objectives, mercury-cadmium-tellurium, Line Spread Function, Modulation Transfer Function, 2D IR focal-plane-array detectors
Abstract
A method for determining the modulation transfer function (MTF) of infrared (IR) objectives is proposed. With the help of an objective under test, the image of a narrow exit slit of a monochromator used as a radiation source and tuned to a certain wavelength is focused in the form of a long narrow strip onto a cold metal screen with a fine aperture slit. Such a slit aperture, used instead of a pinhole aperture, allowed us to increase the useful signal and employ the exit slit of the monochromator as a radiation source. Behind the screen, instead of a small-area IR detector previously used in similar characterization studies of IR objectives, an apertured 2D IR FPA detector was used. With the help of 320×256 mid-wave IR (MWIR) and long-wave IR (LWIR) focal-plane-array detectors based on epitaxially grown mercury-cadmium-tellurium films, the Line Spread Function and MTF of MWIR and LWIR objectives were measured. The experimental data obtained were compared to the calculated diffraction-limited MTF of the tested objectives.
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