Time- and position-varying infrared scene simulation

Rapidly changing infrared scenes can be generated as a function of position using thermally produced irradiance. This can be done most conveniently by using a variable dwell-time, variable diameter, and scanning laser beam to deposit a predetermined amount of laser energy, as a function of position, on the target surface. An infrared target simulator has been designed and tested to perform within stringent temperature simulation requirements: heating rate of over 100 K/sec is achieved, and temperature gradients of 200 K/mm can be maintained. Problems with heat transfer between adjacent elements at different temperatures are solved by modeling the thermal layer on the target surface as a low-pass filter, which cuts off all the frequencies above the thermal cutoff frequency. When the system approach is taken to the infrared simulation design, the optical system limited performance results in the best realizable performance. In this case, the thermal layer on the target surface is designed so that the thermal cutoff frequency is above the optical cutoff frequency.