Multi-functional optical design for IRST system using high-definition detector

Abstract

This paper introduces a mid-wavelength infrared (MWIR) lens design which has both function of high-speed scanning and optical zooming for Infrared Search and Track (IRST) System. For scanning function, a reflecting mirror is integrated within the optical system to stabilize the light-of-sight of the optical axis in integration time. This scanning mirror is placed in front of an imager group which focus the light onto the image surface. To perform the optical zooming function, an afocal telescope is place conjugated with the scanning mirror so that the optical lens design can change the focal length without affecting the scanning function. The field of view in scanning mode is 19.0° x 23.6° for a single frame while in optical zooming mode, the field of view can be change to 5.9° x 4.8° at minimum which makes the optical zoom power of 4X. All optical configurations of the system are designed to work with a F/#2 SXGA (1280 x 1024) cooled detector having a pixel pitch of 15μm.