Calculate the edge of a transparent object

Hi! I'm trying to calculate the profile of a lens. I took the picture of the profile and now i'm trying to find the edge of the lens with a matlab code. I tryed to use edge detection algorithm but the problem is that the shades on the lens make it difficult.

I attach the picture

Does anybody can help me? Thank you in advance :)

[Walter Roberson]

Could you use a high-contrast light source, perhaps one with grid lines on it in at least one direction (across the picture) ?

[clara Lagomarsini]

yes, i can try to use it!

[Vijay]

I am also facing same problem with transparent plastic part

[Image Analyst]

Start your own discussion, and attach your image, at least the best image you can capture.

Answer 1

[Image Analyst]

I'd say put more work into getting a better photo such as having a darker background, more "edge on" viewing angle, darker base that it's laying on, etc. Then it would be a lot easier and could be automated. For now, I'd suggest you use imfreehand() to hand-trace the lens. Let me know if you want a demo of imfreehand().