Phase contrast microscopy with a reflective sample?

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Joined: Fri Aug 25, 2006 11:43 am
Location: Leicester, UK

Phase contrast microscopy with a reflective sample?

Post by TM2030 »

Hi All, I am trying to find ways to enhance the contrast from a reflective metal specimen with low contrast marks on it. Currently I am using a low NA objective and viewing on a CCD camera. I wondered if I could use a phase contrast objective (or similar technique) to improve contrast? I can't use ring illumination as there is restricted access (Thats also why I cant use a large NA objective but in any case I think that would mainly improve resolution not contrast). I was wondering if i could illuminate the sample with an expanded laser (beam) and knock out the zero order diffraction with a central mask at the objective back focus ? I dont know if i need a phase mask or just a blocking mask? But I am still not sure what the image would look like or if it would improve at all in terms of contrast. CCD is B/W. I dont want to get expensive bits in, unless there i was sure it would improve matters.
The laser angle would point down onto the specimen just off a vertical angle again to avoid the restrictions , then be reflected back into the objective. Any advice would be greatly appreciated.
Many thanks.