The Vologda Optical-Mechanical Plant has patented a four-lens infrared lens operating in the IR wavelength range. The development is intended for special optical systems where high aperture and long focus are important.

The lens consists of four components arranged along the path of the rays. The first component is a positive meniscus, with its concave surface facing the image space. The second is a negative meniscus, with its concave surface facing the object space, made of zinc selenide. The third is a positive plano-convex lens, with its flat surface facing the object space. The fourth is a positive meniscus, with its convex surface facing the object space. The first, third, and fourth components are made of chalcogenide glass.

Strict ratios of refractive indices and dispersion coefficients for a wavelength of 10.6 micrometers are observed – all of them are within the specified ranges.

The technical result is an increase in the aperture and focal length of the lens while maintaining high image quality. The patent has already been obtained. Such lenses can be used in thermal imagers, night vision systems, and other equipment for infrared operation where a clear image at a long distance is required.