Equivalent blur as a function of spurious response of a sampled imaging system: application to character recognition

Image sampling effects have been variously quantified as aliased signal, sp atial signal, and spatial noise. However, a relationship between these char acteristics and human object recognition has not been established in a cohe rent, mathematical form. We present a heuristic study that characterizes th e performance degradation that is due to the spurious response of a sampled imaging system as an effective increase in system blur. A character recogn ition experiment was performed in which 20 observers responded to 3500 char acter pairs of blur and sample spacing. A baseline was created where the pr obability of character recognition was determined as a function of blur wit hout sampling. The sampled characters were then compared with this baseline so that the effect of sampling on character recognition could be determine d. Finally, an increase in blur was established as a function of spurious r esponse, which describes the overall effect of sampling on observer charact er recognition. (C) 1999 Optical Society of America [S0740-3232(99)03105-1] .