The problem with using a regular camera is you need a bright light shined at the iris in order to make sure you can see it well. Most people find this uncomfortable, which makes it hard to get people to adopt it.

Instead, most iris scanners use a near infrared camera and light instead. Near-infrared LEDs are cheap and and since you can't see the light it doesn't bother you. CMOS cameras can see near-infrared pretty well without any special processing. Typical CMOS cameras usually have a near infrared filter because without it images tend to look weird with the extra near-infrared light. So a standard sort of webcam or the camera in your phone won't work.