Chromatic aberration of a dipteran corneal lens

Summary The longitudinal chromatic aberration (variation in the position of focus with wavelength) of corneal facet lenses of the houseflyMusca domestica is measured directly. The result is shown to agree with that calculated using the thick-lens formulas, the measured lens parameters and the dispersion of the refractive index of the lenses, measured with an interference microscope. The longitudinal chromatic aberration between the two wavelengths of peak absorption of fly rhabdomeres (360 nm and 495 nm) is about 2.5 m and comparable to the depth of focus of the lens, assuming the lens to be diffraction limited. Chromatic aberration is therefore expected to have little effect on optical image quality in the fly; in particular the effect on the modulation transfer function at the receptor level and on the angular sensitivity of the rhabdomeres is insignificant.Abbreviations LCA longitudinal chromatic aberration - MTF modulation transfer function