Zachary J Kelly¹, Vincent Lau¹, Geoffrey K Aguirre¹; ¹University of Pennsylvania

Measurements of visual experience have largely focused upon spatial visual properties (e.g., orientation, spatial frequency) and have made use of static images and cinematic videos. To support studies of individual differences in visual experience, we created a personalized, wearable, all-day, high-speed light-logger. Our goal is to measure the wide-field, low spatial frequency properties of spectral and temporal visual experience across the full range of photopic vision, and to characterize how these natural statistics interact with eye and head movements. The logger is mounted on inexpensive eye glasses (Pair Eyewear) with custom refractive lenses for each participant; 3D-printed spectacle arms incorporate sensor housings. The World camera (IMX219 chip with an M12 lens) provides 120° FOV, RGB video at 200 FPS (rolling shutter; 8 bit, 30x40 Bayer down-sampled image). The Eye camera (PupilLabs Cam2) provides 120 FPS IR video (global shutter, 400x400). Photopic spectral irradiance is derived from 10 narrow wavelength channels at 1Hz (AS7341 chip); mesopic illuminance is measured for a single wide band (TSL2591 chip). 6-DOF head movement is recorded at 10Hz (LSM6DSV16X chip). A Hall effect sensor detects the presence of magnetic clip-on sunglasses. HDMI and USB cables carry data to a 3D-printed (5.4”x3.4”x2.6”) recording pack worn on a cross-body strap, containing a Raspberry Pi 5, M.2 SSD, and rechargeable battery. We performed sensor calibration against a commercial spectrophotometer (PR670) within a light-integrating sphere receiving output from an 8-channel digital spectral synthesizer (plus varying neutral density filters). Using a custom gain control algorithm, the World camera provides nearly flat temporal sensitivity between 0.25 and 50 Hz across a 4 log illuminance range. Validated spectral sensitivity channels are linear across 5 log illuminance. Eye and World recordings are synchronized to within 10 msecs. We are currently refining the device for subject comfort prior to field trials.

Acknowledgements: R01EY036255