Finding radius by fitting circles to partial lines

Hello, I am trying to find the radius of circles from images which contain only a portion of the circle image, like this: http://postimage.org/image/hs9wbu3fv/ is anyone familiar with how to do this, for instance using Hough transforms? Thank you,

[Matt J]

Only the radius? You already know where the center is?

Answer 1

[Image Analyst]

You can find published methods for that here in VisionBib: http://www.visionbib.com/bibliography/contentsshapefrom.html#3-D%20Shape%20from%20X%20--%20Shading,%20Textures,%20Lasers,%20Structured%20Light,%20Focus,%20Line%20Drawings, particularly this section: 9.5.3 Optical Interferometry, Moire Patterns

Answer 2

[Matt J]

Anyway, you'll find lot's of circle detectors on the FEX.

http://www.mathworks.com/matlabcentral/fileexchange/index?utf8=%E2%9C%93&term=hough+circle