A microspectrophotometer of exceptional sensitivity has been constructed to record absorption spectra of visual pigments in single cells using minimum light. With this equipment, pigments of individual cones have been recorded in regions of less than 1 µ radius, with minimum bleaching. The instrument is simple and flexible in design, and uses commercially available components throughout. This paper reviews some general design considerations, the character and performance of our equipment, and some of the results obtained with retinal cones.
P. A. LIEBMAN and G. ENTINE, "Sensitive Low-Light-Level Microspectrophotometer: Detection of Photosensitive Pigments of Retinal Cones," J. Opt. Soc. Am. 54, 1451-1458 (1964)