Figure 1 illustrates the optical component layout and light paths of the new PVS. Linearly polarized light emitted continuously by the main 785-nm laser diode (LD1) passes through a pair of plano-convex lenses (LP1), and is then transmitted by a plate polarizing beam splitter (PBS) toward an HWP that is spun by a motor using a pulley ratio to achieve a rotation 9/16th as fast as the scan (explained below). After passage through the rotating HWP, the beam of continuously rotating linearly polarized light enters the scanning unit that consists of two gold-plated plane mirrors (M1 and M2). The scanning unit is driven by the same motor, thus turning the stationary beam of light into a circular scan. Light from the outer scanning mirror (M2) travels toward the eyes through a 106 deg retarder (WP) with its fast axis oriented horizontally (0 deg azimuth). While each eye is fixating, or focusing, on a blinking red light generated by a 690-nm laser diode (LD2), optically conjugate to, and appearing to be in, the very center of the scanning circle, each retina is scanned by the spot of laser light in a circle subtending a visual angle of 3 deg in diameter. The small percentage of light reflected from each ocular fundus is reimaged back, following the same light path it originally came from, via the principle of conjugacy. The unchanged part of the returning light, in other words the part with the same polarization as the original plane of polarization, is transmitted through the PBS back toward the light source, thus never making it to the detection unit. The changed part of the returning light, on the other hand, is reflected by the PBS toward the photodetector assembly, consisting of two bull’s-eye photodetectors (PD1 and PD2), one for each eye. Note that the eyes and photodetector assembly have been rotated 90 deg about the optical axis for clarity of illustration. A band pass filter (F) ensures that only light in the desired wavelength range reaches the detectors. It is positioned between another pair of plano-convex lenses (LP2) to avoid shifting of the filter’s peak transmission to a shorter wavelength, which can occur if used in convergent or divergent light. The lens pair images the spatially preserved signals from the right and left eyes, separated by a knife-edge reflecting prism (P) conjugate to the plane of the pupils, toward PD1 and PD2.