Simulation and control of narcissus phenomenon using nonsequential ray tracing. II. Line-scan camera in 7-11 microm waveband.

A nonsequential ray tracing technique is used to calculate the narcissus signature in infrared (IR) imaging cameras having cooled detectors operating in the 7-11 microm waveband. Imaging cameras based on a one-dimensional linear detector array with a scan mirror are simulated. Circularly symmetric diffractive phase surfaces commonly used in modern IR cameras are modeled including multiple diffraction orders in the narcissus retroreflection path to correctly estimate the stray light return signal. An optical design example based on a step-zoom dual field of view optical system is discussed along with the performance curves to elaborate the modeling technique. Optical methods to minimize the narcissus return signal are explained, and modeling results presented. The nonsequential ray tracing technique is found to be an effective method to accurately calculate the narcissus return signal in complex IR cameras having diffractive surfaces.