Procedural features of the size calculation of optical systems of scanningthermal viewers that operate with cooled photodetectors

This paper discusses features of the size calculation of the optical system s of scanning thermal viewers. It is shown that, when the size is calculate d, the shading effect, which affects the image similarly to vignetting in o rdinary observation devices, often occurs in the direct ray path. It occurs when structural elements of the optical system fall into the field of view of the radiation detector and can be eliminated much more easily when the size calculation of the optical system is carried out in the reverse ray pa th. (C) 2001 The Optical Society of America.