Database

The performance results reported here are based partly on a photographic database of eye images generously made available in 1989 by Ophthalmology Associates of Connecticut, which were digitized and then combined with further databases of images subsequently acquired directly with videocameras in Massachusetts and in Cambridgeshire, England. The total number of different eyes represented in the combined database was 592, in images acquired over a three year period from 323 persons. Multiple images were always acquired from each person, ranging from 2 to 10 images of each eye over the time period (average 3.04 images per eye). Some images were rejected manually because of excessive eyelid closure or poor focus, before the automatic operators to perform these tasks as described in Section 2.2 were developed. Images in RS-170, VHS (NTSC), and S-VHS (NTSC) formats were digitized by 480 x 640 monochrome 8-bit/pixel framegrabber boards in either Macintosh or (by SCSI interface) SUN sparcstation hosts. Image resolution and iris size within the images varied due to both distance and video zoom factor, but the outer diameter of the iris was always greater than 60 pixels and was usually in the range of 100 pixels to 200 pixels. Imaging distances ranged from 46cm to 15cm, normally through a 330mm positive meniscus lens. Ethnic groups and nationalities represented in the combined databases included persons of Northern European, Mediterranean, Eastern European, Indian, Semitic, Afro-American, Hispanic-American, Japanese, and Chinese origin.