There are many situations in which photographic recordings of imaged data are made under less than ideal conditions. In aerial reconnaissance, ground surveillance, x-ray examinations, and other applications where "retakes" are either undesirable or impossible it is inevitable that some information will have to be extracted from images which are of low contrast due to under or over exposure or to intervening obstructions such as fog, haze, or soft body tissue. This paper will disuss the IDES, which has been designed to increase the intelligence a trained observer may extract from the available images. IDES combines a high quality variable-magnification binocular microscope with the Itek PROM (Pockel's Readout Optical Modulator) to allow an operator to adjust the contrast of the input imagery by changing the image bias while it is being viewed. This contrast adjustment varies continuously from positive to negative, with the intermediate settings resulting in dark contours of constant input intensity appearing in the image. These contours enhance the gradients which form the edges of image details thus making them more visible.
Bruce A. Horwitz,
"The Image Detail Enhancement System (IDES)", Proc. SPIE 0126, Clever Optics: Innovative Applications of Optics, (21 November 1977); doi: 10.1117/12.955893; https://doi.org/10.1117/12.955893