How to detect circles in the given image?

I am working on a series of images- some blurry, some sharp. My aim is to detect the outer boundary of the iris.

After adaptive thresholding, the image becomes:

I have applied similar adaptive thresholding to all my test images- some of them are blurry, some have sharp focus measures. A few of my results:

I want to extract the circular boundary which marks the iris through a common code. Although it is quite visible intuitively, neither of regionprops or imfindcircles is able to locate the iris. Moreover, in some cases, it is not exactly a complete circle, and gets trimmed across the left and right edges while capturing the photo.

Any help or advice on this would be much appreciated!

[Swarooph]

More pre-processing could help. Try performing some morphological operations to reduce the noise (non-circular features) in the image before using imfindcircles. Some documentation to help: http://www.mathworks.com/help/images/morphological-filtering.html

Answer 1

[Image Analyst]

There are so many iris detection algorithms. Just check the literature for the latest and greatest one(s): http://www.visionbib.com/bibliography/contentspeople.html#Face%20Recognition,%20Detection,%20Tracking,%20Gesture%20Recognition,%20Fingerprints,%20Biometrics

21.5.3 Biometrics, Iris Recognition Systems
    21.5.3.1 Iris Based Biometrics, Biometrics Engineering Research Center, Dongguk University
    21.5.3.2 Iris Recognition Systems, Infrared, Near-Infrared, NIR Based
    21.5.3.3 Iris Recognition Systems, Wavelet Based
    21.5.3.4 Iris Detection, Segmentation and Localization Systems
    21.5.3.5 Iris Recognition Systems, Systems, Evaluation, Comparison, Surveys

[Anannya Uberoi]

Hey,

Thanks for the link. I was wondering why a simple Hough Transform is unable to detect the rings in the binary images I attached. Could you point out a possible reason?

I am using Hough Transform (imfindcircles) after Canny edge detection on the binary image.

[Image Analyst]

I don't really know, short of delving into it myself. Perhaps you need to adjust some parameters with it.

[pawarcse]

Hello, I am currently working on Iris Recognition and I am having problem in detection of pupil and sclera Boundary. Please help me to solve this problem!! I am using Daugaman Algorithm.