The zoom-afocal optical system of the zoom lens for the infrared range comprises lenses made of optical material transparent in the infrared region of the spectrum, arranged one after the other along the optical axis, the orderly displacement of which along the optical axis provides a change in angular magnification. The number of lenses is four lenses, of which the first and fourth lenses have positive optical powers and the same design parameters, and the second and third lenses have negative optical powers and also the same design parameters, wherein the actual back focus of the first subsystem composed of the first and second lenses is aligned with the front apparent focus of the second subsystem composed of the third and fourth lenses, thereby forming a Galilean telescopic system with variable angular magnification, and relative to this system, the fixed pupil of the fixed lens, which is fixed relative to the fourth lens, serves as the aperture diaphragm of the Galilean system.
Comments are closed