A field portable, multiwavelength, digital image processing system for the analysis of thin layer chromatography plates is described. The imaging module consists of a two‐dimensional charge coupled device detector, a xenon strobe light source, a stepper driven filter wheel for wavelength selection, and hardware to digitize images. The instrument is controlled by a laptop computer resulting in a compact device the size of a 6‐in. thick briefcase. As a representative application, software has been developed for the automated analysis of sulfa residues in pork products by thin layer chromatography (USDA SOS‐test). Response to analyte concentration is linear over two and one half orders of magnitude with a correlation coefficient of 0.9998. Detection limit is 80 pg for sulfamethazine spotted on a plate.