![]() We recommend discarding all pupil diameters with a lower outline confidence measure of 1. Pupil fits from different measurement sessions are illustrated as a function of the outline confidence. (B) For each detected diameter, an outline confidence measure is provided and used as an indicator to filter unreliable pupil fits from the dataset. The pupil diameter from the recorded images was extracted using the available algorithms in PupilEXT and pre-processed to illustrate the algorithms’ detection differences. An anchor spectrum with a correlated color temperature (CCT) of 5,500 K (L = 201 cd/m 2 ± SD 0.48) was turned on for 90 s between each stimulus. The pupil was exposed to LED spectra of the peak wavelengths 450 nm (L = 100.4 cd/m 2 ± SD 0.23) and 630 nm (L = 101 cd/m 2 ± SD 0.31) for 30 s. (A) Eye images from one subject were recorded during a chromatic pupillometry experiment using PupilEXT. (E) The software PupilExt can be used without connected cameras in an offline mode to detect the pupil diameter from externally captured images.Ĭomparison of the pupil detection algorithms based on the same eye image set and visualization of the pupil ellipse fit as a function of the outline confidence. ![]() (D) Prototype of a pupillometry set-up with a single camera and respective near-infrared (NIR) illumination unit. Without the use of a microcontroller, a software trigger is used for image acquisition. (C) The use of a microcontroller is optional when connecting a single camera. When capturing multi-image sequences, the hardware trigger consists of a square wave signal in which each rising edge triggers an image acquisition. (B) In mono camera vision mode, it is possible to control the image acquisition by an external hardware trigger, which has the advantage that the recording time can be set accurately. We implemented a UART communication protocol in the microcontroller so that PupilExt can automatically control and synchronize the stereo camera system via the connected hardware, via the electronics. We recommend using a Nucleo-STM32 microcontroller since the provided source code can be used to flash the electronic. A microcontroller is connected to the IO-pins of the camera, which triggers a synchronized image acquisition on both cameras. (A) In stereo vision mode, two cameras are connected to the computer via USB3.0. Illustration of the possible measurement configurations that can be realized with the PupilExt software. Įye tracking open source pupil diameter pupil measurement pupillometry stereo camera vision research.Ĭopyright © 2021 Zandi, Lode, Herzog, Sakas and Khanh. The PupilEXT software has extended features in pupil detection, measurement validation, image acquisition, data acquisition, offline pupil measurement, camera calibration, stereo vision, data visualization and system independence, all combined in a single open-source interface, available at. A developed 120-fps pupillometry demo system was able to achieve a calibration accuracy of 0.003 mm and an averaged temporal pupil measurement detection accuracy of 0.0059 mm in stereo mode. We offer a selection of six state-of-the-art open-source pupil detection algorithms (Starburst, Swirski, ExCuSe, ElSe, PuRe and PuReST) to perform the pupil measurement. This work's core outcome is an integrated cross-platform (macOS, Windows and Linux) pupillometry software called PupilEXT, featuring a user-friendly graphical interface covering the relevant requirements of professional pupil response research. Our goal was to make a professional remote pupil measurement pipeline for laboratory conditions accessible for everyone. Here, we developed an open-source pupillometry platform consisting of hardware and software competitive with high-end commercial stereo eye-tracking systems. Moreover, commercial systems rely on closed software, restricting conclusions about the used pupil-tracking algorithms. Mostly commercial solutions are used as measurement devices in pupillometry which is associated with high investments. Diameter changes in the range of 10 -2 mm are of interest, requiring reliable and characterized measurement equipment to accurately detect neurocognitive effects on the pupil. ![]() The human pupil behavior has gained increased attention due to the discovery of the intrinsically photosensitive retinal ganglion cells and the afferent pupil control path's role as a biomarker for cognitive processes.
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