An indirect method for determining the spectral response of infrared detectors

This dissertation presents the results of an investigation into the development of a novel measurement technique to indirectly determine the spectral response of infrared detectors. Current spectral response measurement instruments directly compare, at each wavelength, the output responses from a reference detector and the detector under test to determine the unknown detector's spectral response. An interpretation of the measurement of the detector spectral response as an inverse problem leads to a system design which can measure the detector spectral response without relying on the spectral characteristics of a reference detector.;The initial investigation of the performance characteristics of the indirect spectral response measurement methodology were carried out using computer simulations in which effects due to different wavelength resolutions, different spectral content in the input spectral irradiance, and different regularization methods were evaluated. The computer simulations includes tools for generating detector output response data based on a known spectral response and input spectral irradiance, analyzing the measurement system in terms of its singular value decomposition (SVD) and reconstructing the infrared detector spectral response using different regularization methods.;Based on the results of the computer simulations, a laboratory prototype instrument was built to validate the indirect spectral response measurement methodology. The spectral response of the MWIR HgCdTe infrared detector that served as the basis for the computer simulations was experimentally measured at a wavelength resolution of ;The indirect spectral response measurement methodology is modeled using a discrete-to-discrete mapping from input spectral irradiance space to detector output response space as described by the matrix equation g = Hf. The m x 1 vector g represents the detector output response data collected by the measurement system, where m is the number of different input spectral irradiance conditions. The unknown detector spectral response is approximated by the n x 1 vector f. The m x n matrix H describes the spectral content of the irradiance at each different measurement condition. The indirect spectral response measurement reconstructs the unknown detector spectral response, f, based on the measured detector output response data, g, the knowledge of the input spectral irradiance that is described by the H matrix, and regularization algorithms that are taken from inverse problem theory.