Circle detection for eye

Hi everyone, I am stuck with this for weeks. After I input a face image,

First: I perform the viola jones eye region detection by using the vision.CascadeObjectDetector

Second: I perform the Canny edge detection based on the eye region that was detected during the first stage.

a = imread('face.jpg');
imshow(a);

detector = vision.CascadeObjectDetector('EyePairSmall');
bbox = step(detector,a);
out = insertObjectAnnotation (a,'rectangle',bbox,'detection');
subplot(2,2,1),subimage(out);
outb = imcrop(out,bbox);
[hog1,visualization] = extractHOGFeatures(outb,'CellSize',[8 8]);
subplot(2,2,2),subimage(outb);
I  = rgb2gray(outb);
BW = edge(I,'canny');
subplot(2,2,3);
imshow(BW);

After that, the image shown is like this:

May I know how can I detect the iris (circle shape) based on the output of Canny edge detection ?

As the region has will only have two circles detected, how is it possible to be implemented ?

I read about the imfindcircle before, but it doesn't work out. Might need the community helps and some guidance on this.

Much appreciated. Thank you !

[KALYAN ACHARJYA]

Iris circle?

[Teik Jin Lim]

Yaya. Iris circle

Answer 1

[Image Analyst]

Why are you using edge detection???

I'd first try thresholding the red channel, and if that is not robust enough, try imfindcircles().

[Teik Jin Lim]

1. Sorry, I don get your "thresholding the red channel" meaning. Can you explain further ?

2. I tried imfindcircles(), it couldnt detect. No circle was detected.

[Image Analyst]

mask = rgbImage(:,:,1) < someThresholdValue; % You pick what someThresholdValue is.

Try adjusting some of the parameters to imfindcircles().

[Teik Jin Lim]

Can you write it in complete form ? I donno what are you talking about. Too random haha.

I am new to Matlab

[Image Analyst]

OK, what is the name of your image? What did you call the variable?

Can you attach the cropped eye image alone? (Use imwrite()).