Pixel response function of BLPP-2000 and BLPP-4000 photodetector arrays

Abstract

Photodetector arrays are widely used in atomic emission spectrometry as a part of spectrum analyzers. When the width of a spectral line is comparable with the array structure pitch, the recorded signal becomes dependent on the position of the line relative to the cells of the photodetector array. This dependence is usually explained by the loss of high spatial frequencies according to the Kotelnikov theorem, and the pixel response function of the cells (the dependence of the cell output signal on the position of a point light spot on the cell surface) is considered rectangular and determined by the cell size. However, this approximation can sometimes lead to significant errors. The aim of this study is to determine experimentally the pixel response function of BLPP-2000 and BLPP-4000 photodetector array cells used in high-speed MAES analyzers by precise moving of a light spot with a diameter of 0.7 μm and a wavelength of 405 nm. The array cell width is 14 and 7 μm, respectively. It is shown that when a light spot enters between the cells of BLPP-2000 and BLPP-4000 photodetectors, no information is lost. As for the cells of back-illuminated CCD BLPP-2000 arrays, the coefficient of mutual influence is 30% and the integral signal does not depend on the position of the light spot. The presence of isolating areas (loci) between the cells in CMOS BLPP-4000 arrays led to insignificant oscillations of the integral signal depending on the position of the light spot, but, however, provided reduction of the coefficient of mutual influence to 5%.