Calibration and Non-Uniformity Correction of MICOM's Diode Laser Based Infrared Scene Projector

Abstract

A dynamic infrared (IR) scene projector which is based upon diode lasers is now operational at the US Army Missile Command's (MICOM) Research, Development, and Engineering Center (RDEC). The projector is referred to as the Laser Diode Array Projector (LDAP). It utilizes a 64-element linear array of Pb-salt diode lasers coupled with a high-speed optical scanning system, drive electronics and synchronization electronics to generate in-band IR scenes. The projector is interfaced to a real-time scene generation computer which is capable of 3-D scene generation. This paper describes the process for calibration of the projector and the correction of spatial non-uniformities which are inherent in the projector design. Each laser within the system must be calibrated so that its output power is linear with respect to input gray level. The calibration table for each laser is stored in the projector electronics memory and is applied in real-time. In addition, spatial variations in perceived pixel intensity must be corrected such that the output scene is uniform. Gain and offset correction factors for each pixel are used to correct the spatial non-uniformities. The gain and offset terms are applied to each pixel in real-time by the projector drive electronics. The projector's overall performance characteristics, including the non-uniformity correction (NUC) performance level achieved to-date, are presented in the paper. Issues associated with NUC limitations are also discussed. Sample images generated with the projector and captured by an InSb FPA sensor are included in the text.