Polarization-enhanced contrast imaging for pupil detection

In pupil detection within the visible light spectrum, intensity information serves as a carrier for capturing the reflective characteristics of images. When the reflectance of the pupil and its adjacent iris is similar, effectively distinguishing between them becomes challenging. Polarization provides additional information sensitive to the physical and chemical properties of objects, aiding in overcoming this problem. In the polarimetric pupil detection method, the transmission process of polarized light in the human eye model is theoretically analyzed. Arbitrary orthogonal polarization channels are utilized instead of intensity to describe the collected image, facilitating the extraction of polarization information corresponding to each channel. Experimental validation of the proposed method was conducted using active polarization illumination imaging experiments. The experimental results verify that the polarimetric pupil detection method could not only suppress the scatter noise but also be capable of obtaining a combination of intensity and polarization information. Moreover, exploiting the distinctions in depolarization characteristics among biological tissues can substantially improve their contrast.The research findings presented in this article provide insights into enhancing imaging methods for existing pupil detection schemes.