Iris scans
by Chris Woodford. Last updated: April 4, 2022.
If you hate having to carry a jangling bunch of jailer's keys wherever you go, imagine how cool it would be if you could unlock your door just by staring at it for a couple of seconds! Iris scanning technology could soon make this kind of thing completely routine. It's already being used in airports and military bases where fast, reliable identification is vitally important. Iris scans are the most accurate form of biometrics (identity checking based on sophisticated body measurements)—far superior as a form of identification to fingerprints (which can wear out in time) or DNA profiling (which isn't instant). What exactly are iris scans and how do they work? Let's take a closer look!
Photo: The eyes have it: computerized security systems can recognize you by decoding the unique patterns in your irises (the colored parts of your eyes). This handheld scanner is made by SecuriMetrics Inc. for the US military. Photo by Michael J. MacLeod courtesy of US Army, published on Flickr under a Creative Commons Licence.
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Contents
Why use biometrics?
There are more people on Earth than ever before, owning more things, and swapping more information every single day. Security has never been more important but—ironically, thanks to the computing power at everyone's disposal—never easier to crack. Traditionally, security relies on things that are difficult to do quickly: locks are physically difficult to bust open without the correct metal keys, while information secured by encryption (computerized scrambling) is hard to access without the right mathematical keys. But this kind of security has a basic flaw: with the right key, even the wrong person can quickly gain access.
Photo: Scanners can be made handheld and easily portable, like this one being used by the US Army, or wall-mounted for convenience in places like airports. Photo by Lewis Hilburn courtesy of US Army and DVIDS.
Most security experts think biometrics (body measurement) is the answer. Instead of restricting access to things through arbitrary locks and keys, we grant access to people if we can positively identify them by measuring some unique pattern on their body. If you think about it, an ordinary passport photo is a crude example of biometrics. When the border guards look at your face and compare it with your passport photo, what they're doing is intuitively comparing two images. Is one nose bigger than another? Are the eyes further apart? That's simple biometrics. The trouble is that our faces change all the time and lots of people look very similar. Fingerprints are a more reliable form of biometrics, but even they're not infallible: illnesses and injuries, as well as basic wear-and-tear, can alter the pattern of ridges on our fingers in time. Iris scans are a much more reliable way of identifying people—simplying by taking quick photographs of their eyes!
What makes an iris scan unique?
The iris is the colored ring of muscle that opens and shuts the pupil of the eye like a camera shutter. The colored pattern of our irises is determined genetically when we're in the womb but not fully formed until we're aged about two. It comes from a pigment called melanin—more melanin gives you browner eyes and less produces bluer eyes. Although we talk about people having "blue eyes," "green eyes," "brown eyes," or whatever, in reality the color and pattern of people's eyes is extremely complex and completely unique: the patterns of one person's two eyes are quite different from each other and even genetically identical twins have different iris patterns.
How does iris scanning work in practice?
To get past an iris-scanning system, the unique pattern of your eye has to be recognized so you can be positively identified. That means there have to be two distinct stages involved in iris-scanning: enrollment (the first time you use the system, when it learns to recognize you) and verification/recognition (where you're checked on subsequent occasions).
Photo: The iris is the colored part of your eye around the dark pupil in the center. A "blue eye" like this has less melanin (brown pigment). If an iris scan can't identify key features clearly, a variety of image enhancement algorithms (mathematical ways of processing a digital image) can be used to make them stand out more clearly.
Enrollment
First, all the people the system needs to know about have to have their eyes scanned. This one-off process is called enrollment. Each person stands in front of a camera and has their eyes digitally photographed with both ordinary light and invisible infrared (a type of light used in night vision systems that has a slightly longer wavelength than ordinary red light). In iris recognition, infrared helps to show up the unique features of darkly colored eyes that do not stand out clearly in ordinary light. These two digital photographs are then analyzed by a computer that removes unnecessary details (such as eyelashes) and identifies around 240 unique features (about five times more "points of comparison" as fingerprint systems use). These features, unique to every eye, are turned into a simple, 512-digit number called an IrisCode® that is stored, alongside your name and other details, in a computer database. The enrollment process is completely automatic and usually takes no more than a couple of minutes.
Photo: Enrollment involves having one or both of your irises scanned, usually up to three times. Photo by Chris Willis courtesy of US Air Force published on Flickr (as a US Government work).
Verification
Once you're stored in the system, it's a simple matter to check your identify. You simply stand in front of another iris scanner and have your eye photographed again. The system quickly processes the image and extracts your IrisCode®, before comparing it against the hundreds, thousands, or millions stored in its database. If your code matches one of the stored ones, you're positively identified; if not, tough luck! It either means you're not known to the system or you're not whom you claim to be.
