One proven technique for nonuniformity correction (NUC) of a resistor array infrared scene projector requires careful measurement of the output-versus-input response for every emitter in a large array. In previous papers, we have discussed methods and results for accomplishing the projector NUC. Two difficulties that may limit the NUC results are residual nonuniformity in the calibration sensor, and nonlinearity in the calibration sensor's response to scene radiance. These effects introduce errors in the measurement of the projector elements' output, which lead to residual nonuniformity. In this paper we describe a recent effort to mitigate both of these problems using a procedure that combines sensor nonuniformity correction and sensor calibration, detector by detector, so that these problems do not contaminate the projector NUC. By measuring a set of blackbody flood-field images at a dozen or so different temperatures, the individual detector output-versus-input radiance responses can be measured. Similar to the projector NUC, we use a curve-fitting routine to model the response of each detector. Using this set of response curves, a post-processing algorithm is used to correct and calibrate the images measured by the sensor. We have used this approach to reduce several sensor error sources by a factor of 10 to 100. The resulting processing is used to correct and calibrate all of the sensor images used to perform the projector NUC, as one step in the projector NUC. The procedure appears to be useful for any application where sensor nonuniformity or response nonlinearities are significant.
For many types of infrared scene projectors, differences in the outputs of individual elements are one source of error in projecting a desired radiance scene. This is particularly true of resistor-array based infrared projectors. Depending on the sensor and application, the desired response uniformity may prove difficult to achieve. The properties of the sensor used to measure the projector outputs critically affect the procedures that can be used for nonuniformity correction (NUC) of the projector, as well as the final accuracy achievable by the NUC. In this paper we present a description of recent efforts to perform NUC of an infrared projector under “adverse” circumstances. For example, the NUC sensor may have some undesirable properties, including: significant random noise, large residual response nonuniformity, temporal drift in bias or gain response, vibration, and bad pixels. We present a procedure for reliably determining the output versus input response of each individual emitter of a resistor array projector. This NUC procedure has been demonstrated in several projection systems at the Kinetic Kill Vehicle Hardware-In-the-Loop Simulator (KHILS) including those within the KHILS cryogenic chamber. The NUC procedure has proven to be generally robust to various sensor artifacts.