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Brian Vohnsen, Benjamin Lochocki, Carmen Vela; The integrated Stiles-Crawford effect for coherent and incoherent extended sources. Journal of Vision 2013;13(15):P22. doi: https://doi.org/10.1167/13.15.57.
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© ARVO (1962-2015); The Authors (2016-present)
The integrated Stiles-Crawford effect expresses the combined effect of all pupil points towards the effective visibility of the human eye. It was first studied 80 years ago by Stiles and Crawford and has since been analysed by a limited number of authors using predominantly annular apertures and weakly-coherent sources. The Stiles-Crawford effect per se is traditionally analysed for a single pupil point at a time using Maxwellian viewing whereby the average directional sensitivity of a retinal region and its photoreceptors can be determined.
Here, we report on an experimental analysis of the integrated Stiles-Crawford effect and compare directly the coherent and incoherent illumination cases using normal non-Maxwellian viewing in a single axis pupil-size flickering system that allows rapid and synchronized changes of pupil size, brightness and color. Relative visibility with large pupils is determined in comparison to that of a 2 mm reference pupil. This shows that integration is valid under normal viewing conditions whereas for partially-coherent and highly coherent light special care has to be taken. The variation with wavelength and the impact of remnant defocus in determining an effective directionality parameter are discussed.
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