Does anyone know something about Rheinberg illumination?

[Ning]

I am a post graduate student,and my issue is to study about how to obtain contrast enhancement based on oblique illumination.Now I have only one idea:Rheinberg illumination.According to all document I have read,I need to put a filter with different color combination on the front focal plane of condenser,and then I can see the sample stained.For example,if I use a filter combined with a red annulus and a green central ,the background shows green and the sample shows redder.But after several times experiment,I failed to obtained the expectation result,I can just find that the background changes color,like green,but the sample does not show any red,just also influenced by green.
So, I want to konw what may lead to my failure?Size of the ring and the central?Diffraction index of the sample?Transmittance of the filter?Or what else?
By the way,after I study about Fourier optics,I learn that we can rebuild the frequency plane to get the ultimate goal:rebuild the image.And the frequency plane lies on the back focal plane of the objective,so can I put filter in the back focal plane of the objective to realize rheinberg illumination or optical stain?
If someone can give me some advice, I will be deeply grateful,thanks!

[75RR]

Try this link. There are several more links within the article.

http://www.microscopy-uk.org.uk/mag/ind ... nberg.html

[Oliver]

I wrote about Rheinberg filters in this issue:
http://www.microbehunter.com/microbehun ... gust-2012/

Make sure that the central patch stop is sufficiently dark. Otherwise there is too much light passing through and the specimen itself will be too bright, taking on the color of the patch stop. If the sample also shows green, then try to adjust the size of the central patch stop. There is an optimum size for the different objectives.
Also note, that not all specimens are equally suitable. The difference in refractive index between specimen and surrounding medium must be sufficiently high, otherwise the light from the annulus (the red part of your filter), which illuminates the specimen from the side, will not bounce off the specimen and will therefore not stain the specimen red.

Oliver