This paper presents a new pseudocolor method that uses a special sensitive plate with a code. It is quite convenient to use the plate to convert a black-and-white picture into a density pseudocolor-coded image. Users need only place the black-and-white picture and the plate with a code in immediate contact with each other and expose them simultaneously. Through simple development, an encoded phase transparency is obtained. That transparency is put on the input plane of a white-light processor; the density pseudocolor-coded image on the output plane is produced by the spatial filtering.
"New Pseudocolor Coding Method Using A Sensitive Plate With A Code," Optical Engineering 26(1), 260160 (1 January 1987). https://doi.org/10.1117/12.7974022