Abstract
The eye has substantial longitudinal chromatic aberration (LCA) of approximately 2 dioptres (D) across the visible spectrum. Under normal broadband illumination, our eyes focus approximately in the middle of the spectrum (i.e. on green wavelengths). However, it is unclear how we accommodate to spectra composed of multiple narrowband components. This is relevant for current types of lighting and displays, which often have relatively narrowband sources. Understanding this will also give an insight into the way the visual system uses various cues in order to accommodate. Our aim was to investigate accommodation to lights with two narrowband components. We measured participants' accommodative responses using an autorefractor. The stimulus was a black Maltese cross mounted on a diffuser presented at 3D from the participant and viewed monocularly. The stimulus was back illuminated by five LEDs, each with a different narrow emission spectrum. We presented various mixtures of pairs of these LEDs. For each mixture, we measured the static accommodative response. We also calculated the accommodative response that would optimise image quality in the luminance pathway for each mixture. The calculations showed that typically image quality would be optimised for the mixtures by accommodating to one of the two individual LEDs. However, the observed responses differed from this. Often participants accommodated somewhere in-between the two wavelengths. One possible explanation for this finding is that rather than accommodating to maximise the image quality, participants were accommodating to reach a certain ratio between the image quality in different cone channels. Under natural broadband illumination this behaviour could provide a good approximation of the best image quality. However, with these unnatural spectra this tactic is no longer effective. Acknowledgements: We would like to thank Martin S. Banks for his ideas and support with this project.
Meeting abstract presented at VSS 2018