How can I detect irises in a face with opencv?
Have a look at this forum thread. There's some source code there to get you started, but be careful about using it directly -- the original author seemed to have problems compiling it.
Start with detecting circles - see cvHoughCircles - hint, eyes have a series of concentric circles.
OpenCV has Face Detection module which uses Haar Cascade. You can use the same method to detect Iris. You collect some iris images and make it as positive set and non iris images as negative set. The use the Haar Training module to train it.
Quick and dirty would be making an eye detection first with Haar filter, there are good model xml files shipped with opencv 2.4.2. Then you do some skin detection (in the HSV space rather than the rgb space) to identify the area of the eye in the middle, or circle search.
Also, projections, histogram-based decisions can be used once the eye area is cropped.
来源：https://stackoverflow.com/questions/5023252/iris-detection-with-opencv