Differential amplitude scanning for retinal imaging: a theoretical study

A differential amplitude scanning system for ophthalmoscopy is described theoretically. The differential scanning ophthalmoscope (DSO) samples the retina with two laterally displaced spots. The signal measured is the difference between the irradiance from these two locations. The theoretical analysis of the DSO shows it offers increased contrast at high spatial frequencies and only weak contributions from the low frequencies. This enables high-gain, low-noise detection that maximizes contrast.