Use of retinal nerve fiber layer birefringence as an addition to absorption in retinal scanning for biometric purposes

Abstract

We built a device sensitive to the birefringence of the retinal nerve fiber layer for biometric purposes. A circle of 20 degrees diameter on the retina was scanned around the optic disk with a spot of light from a 785 nm laser diode. The nonbirefringent blood vessels indenting or displacing the retinal nerve fiber layer were seen as "blips" in the measured birefringence-derived signal. For comparison, the reflection-absorption signature of the blood vessel pattern in the scanned circle was also measured. The birefringence-derived signal proved to add useful information to the reflectance-absorption signature for retinal biometric scanning.

Retinal identification

“…The measurement setup is explained in detail in [Agopov et al (2008)]; here it is explained briefly. The apparatus and the light paths within it are shown in Figure 5.…”

“…This can be seen in the GDx-pictures, where the blood vessels are seen as dark lines on the otherwise bright nerve fiber layer. The author and his co-workers studied the possibility of using blood vessel-induced RNFL birefringence changes for biometric purposes [Agopov et al (2008)]. A measurement device was built to scan a circle of 20 • around the optic disc.…”

Detecting central fixation by means of artificial neural networks in a pediatric vision screener using retinal birefringence scanning

“…Meanwhile, development of the RBS technology has continued in our lab, resulting in a series of central fixation detecting devices with no moving parts [11, 12], devices for continuous monitoring of fixation [13], a device for biometric purposes [14], and ultimately an improved PVS that combines “wave-plate-enhanced RBS” [15], or “polarization-modulated RBS” [16, 17], for detecting strabismus, with added technology for assessing proper focus of both eyes simultaneously. Polarization-modulated RBS is an optimized upgrade of RBS, based upon our theoretical and experimental research and computer modeling, using a spinning half wave plate (HWP) and a fixed wave plate (WP) to yield high and uniform signals across the entire population.…”

Modern technologies for retinal scanning and imaging: an introduction for the biomedical engineer

“…A more recent study has led to the optimization of the parameters of the optical components used in RBS and to improvement of the signal-to-noise ratio across a wide population [108]. RBS has also been shown to work for biometric purposes by identifying the position of the retinal blood vessels around the optic nerve [109], and for identification of Attention Deficit and Hyperactivity Disorder (ADHD) by assessing the ability of test subjects to stay fixated on a target [100]. …”

“…The amount of birefringence can drop locally if a blood vessel is encountered during retinal scanning.This enables retinal identification for biometric purposes [109,156]. A circular scan of of 20° around the optic disc catches all major blood vessels entering the fundus through the disc.…”