# Does coverslip thickness matter for high NA oil immersion objectives?

This question is related to Impact of covering glass on lens performance.

I use a 63x TIRF objective with a numerical aperture of 1.46 and oil immersion. The immersion oil has an index of $n_e=1.518$. I'm observing green eGFP fluorescence at around 510 nm. Does it matter if I use a coverslip (BK7 glass) with 140 $\mu$m thickness instead of 170 $\mu$m?

Edit: The objective is a Zeiss Objective alpha "Plan-Apochromat" 63x/1.46 Oil Corr M27

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## 1 Answer

Yes, you are getting a bit higher aberrations in the corners of the image (i.e. they might be a little more blurry).

As long as image quality is ok for you, you may continue doing so.

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I am more concerned about the spherical (and maybe chromatic) aberration which would effect the PSF and Strehl ratio. My field of view is very small, 60$\mu$m diameter. – whoplisp Jul 9 '11 at 22:47
Do you have specific model of your lens? Do you know it's type or optical scheme (might be in the docs)? I might then try to simulate coverglass effect (and knowing model/optical scheme would make simulation more precise, but possible in any way) – BarsMonster Jul 9 '11 at 22:59
I added a screenshot from their web store but I'm afraid they wouldn't give me exact information. A while ago I searched through their patents but I think the objective is too new for the patent to be released (if there even is one). – whoplisp Jul 9 '11 at 23:11
Whoa, nice lens price :-) While I am still thinking should I spend 1200\$ for whole 'decent' microscope :-) – BarsMonster Jul 9 '11 at 23:11
Hmm... This adjustable ring seems to be something interesting... Isn't it have adjustable glass correction? :-) – BarsMonster Jul 9 '11 at 23:12