we use 100x 1.25NA oil objective lens，but the pictures still look unclear. Can you please provide solutions to better improve the resolution for accurate detection?
@Euaria your image does seem to be the same focus across the field of view, so most things must be correct or close to correct. There are some random blurred patches that must be something to do with the sample, it looks to be cells piled up and so not in focus. Your lens is very high specification, so to match that you will need everything else as good. Even with a good optical system the cells that you are looking at have some thickness. The depth of field of a high resolution lens is very, very small and you will find that there may well not be a single position where the whole depth of the cell is in focus. What measure of resolution are you using?
Your lens has a very high numerical aperture, but it can only be effective if there is light supplied at that very high numerical aperture. This means that the illumination is very important and is often the main thing limiting the resolution achieved. Have you got the illumination and condenser adjusted for the highest numerical aperture at the sample? Particularly what lens are you using in the condenser and is it the right way up?
There is another thread about getting the best performance with a very high quality lens: Focusing and Chromatic Aberration Issues
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