Direct discrimination of structured light by humans

TL;DR

Humans can directly perceive and discriminate structured light with space-varying polarization through an entoptic phenomenon, enabling new methods for retinal characterization and optical state probing.

Contribution

This study reveals a novel entoptic phenomenon allowing humans to perceive polarization-structured light, demonstrated through psychophysical experiments with significant discrimination success.

Findings

Participants discriminated OAM states with 77.6% success

The phenomenon enables new retinal and optical state investigations

Experimental verification of polarization-based perception

Abstract

We predict and experimentally verify an entoptic phenomenon through which humans are able to perceive and discriminate structured light with space-varying polarization. Direct perception and discrimination is possible through the observation of distinct profiles induced by the interaction between the polarization gradients in a uniform-intensity beam and the radially symmetric dichroic elements that are centered on the foveola in the macula of the human eye. A psychophysical study was conducted where optical states with coupled polarization and orbital angular momentum (OAM) were directed onto the retina of participants. The participants were able to correctly discriminate between two states, differentiated by OAM =\pm7, with an average success probability of 77.6 % (average sensitivity d^\prime=1.7, t(9) = 5.9, p = 2\times 10^{-4}). These results enable new methods of robustly characterizing the structure of the macula, probing retina signalling pathways, and conducting experiments with non-separable optical states and human detectors.