The Microdensitometer Revisited

The developments leading to the characterization of microdensitorneter optical performance, through application of the principles and methods of the theory of partial coherence, are briefly reviewed and a summary of the papers contributing to the current state of knowledge is given. The basic imaging equations are presented and briefly discussed. The problem of achieving effective incoherence in the system illumination with incandescent sources is also discussed and the current criterion evaluated. The development of a new criterion for effective incoherence is then undertaken and a more useful inequality is derived. In those instances where the maintaining of effectively incoherent illumination conflicts with the minimizing of flare -- a case common to systems with limited reduction factor for the influx subsystem -- it is shown that there is a performance tradeoff: linearity (which occurs with incoherent illumination) or flare (which occurs with excessive over-illumination of the sampling aperture). A quantitative relation between these is established and a procedure is outlined for reconfiguring the microdensitometer to meet coherence requirements with a minimum of excess flare.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.