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S a n t a B a r b a r a R e s e a r c h C e n t e r Coleta, California ABSTRACT The interest in the nonuniformities in response of i n f r a r e d d e t e c t o r s h a s i n c r e a s e d r e c e n t l y d u e t o the increased number of detectors being considered for future infrared sensors. This paper identifies how l a r g e a uniformity problem exists for various types of detectors and indicates the possible causes of the observed variation. Detector nonuniformity and present on-chip correction techniques can be considered within the two categories of scanning and staring systems. They are discussed separately since applicable correction techniques either need to be developed or are different.A survey is made of the nonuniformities encountered in the fabrication of d e t e c t o r a r r a y s of photoconductive (PC) HgCdTe, P C PbS, PC Si:In and photovoltaic ( P V ) InSb. A discussion is not made of the use of c a l ibration data stored in system signal processing m e m o r y b e c a u s e t h i s s t r a i g h t f o r w a r d a p p r o a c h w i l l probably be located off focal plane. UNIFORMITY REQUIREMENTS IN INFRARED IMAGINGThe design of a s y s t e m f o r i n f r a r e d i m a g i n g is c h a r a c t e r i z e d by two major problems: 1) the background of infrared photons is v e r y high, and 2 ) the contrast between different portions of a n i n f r a r e d image is v e r y low. The background occurs because of the thermal emission of IR photons by all objects. This emission can be generally charact e r i z e d by the blackbody radiation curve which (for 300'K objects) peaks at 12-micrometer (pm) wavelength radiation. The contrast (the change in the photon flux) between different objects is s m a l l compared with the total f l u x and depends on changes in temperature and emissivity. Typically, high performance systems will try to resolve tenths of a degree Kelvin temperature differences.To have a usable image, the nonuniformity between different elements of a n 1R a r r a y m u s t g i v e r i s e t o s i g n a l v a r i a t i o n s w h i c h a r e t h e o r d e r of, o r less than, the d e s i r e d s y s t e m t e m p e r a t u r e s e n s itivity. Unfortunately, a single uniformity criterion cannot be used since a 0. 1'K variation in temperature will give rise to variation in the signal photon flux that depends on the wavelength of the detector IR radiation. Analytically, the photon f l u x on a detector is X2x 2This integral, evaluated for the standard imaging wavelength bands, is listed in Table 1 along with the percentage change for 0. 1'K change in t e m p e r a t u r e . Table 1. Percent Changes in the Background for the Commonly Used Wavelength Bands in Thermal Imaging 3 TO 4.2 3 TO 5.0 8 TO 14.0 2.31 X 1015 0.431 1.10 x 1016 0.371 8 TO 12.0 5.00 X 1017 0.167 0.154 FluxThe selection of a uniformity requirement for t h e d e t e c t o r a r r a y s would be easy if we could assume that the calculated AF/F (YO) were the required values.A realistic derivation of the requirement, however, sho...