Abstract
Purpose :
Eye images captured by diagnostic devices and laser systems often exhibit corneal specular reflections caused by infrared LED illuminations. These specular reflections can affect the accuracy of eye detection and reduce the number of match points for iris registration.
This study proposes a novel method using pulsed LED illumination synchronized with image acquisition to remove the corneal specular reflections in the eye images to enhance precision in iris registration.
Methods :
A glass test eye was used to verify the synchronizing pulse LED illumination with the torsional image acquisition for LASIK refractive surgery. An auxiliary LED bank and a peripheral LED bank are used to synchronize infrared illumination with the torsion camera for image acquisition. Each LED bank consists of a 2x3 array of infrared LEDs with a central wavelength of 870nm. A synchronizing pulse signal was created to alternatively turn on the auxiliary LED bank and the peripheral LED bank for torsion imaging. The torsion camera’s video frame acquisition was synchronized to the pulse signal, capturing two adjacent frame eye images in which one was illuminated by the auxiliary LED bank and the other was illuminated by the peripheral LED bank. Subsequently, an image processing algorithm was developed to remove the specular reflections from both eye images, creating a new eye image with specular reflection removed for iris registration.
Results :
In Figure 1, Image A and Image B are the two adjacent frame images captured by the torsion camera (Ximea, 250Hz fps) from the test eye under 100Hz pulsed LED illumination. Image A is the eye image illuminated by the auxiliary LED bank, while Image B is the image illuminated by the peripheral LED bank. Specular reflections from the LED illuminations are shown with high light intensity in both images. Image C is the processed eye image derived from Image A and Image B, in which the specular reflections have been efficiently removed, and the non-uniform illumination have been corrected..
Conclusions :
This study demonstrates a significant reduction of cornea specular reflections in eye imaging through pulsed LED illumination. It provides an effective low-cost approach to produce eye images with clear iris features for iris registration, and clear pupil image for eye tracking.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.