I want to have a optical system where, I focus a beam onto the BFP of a microscope objective. Unfortunately, I always have a strong Back Reflection from the objective. Can anyone suggest me some tips to counter that?
Have you tried crossed polarizers? Use one for the incident beam and another at 90° for the detection path.
What are the optical filters you are using? Maybe adding an additional long-pass filter can you reduce the reflection in case the polariser solution won't work for you (e.g. if you are looking at week fluorescence and can't afford to waste about a half of the fluorescence intensity on the analyser)
Hello, Edgar Guevara Unfortunately, that is not an option for us. Our detection path and excitation path is quite same. I have attached a crude diagram to show the situation. And more importantly my detection wavelength is the same as the incident wavelength. The partial reflector is also a partial transmitter (Beam splitter).
Check if you can replace the objective with one with (a perhaps better) anti-reflection coating. If you feel adventurous, you may get some ideas here: Conference Paper Minimising back reflections from the common path objective i...
You may also contact a representative of an optics co.
Ranit Roy
Maybe I am missing something, but I think you can try crossed-polarizers in your setup, as we did in Fig. 1 of the following paper:
Article Laminar optical tomography of the hemodynamic response in th...
- Nikolaos Kourkoumelis's idea is perhaps the most straight-forward solution.
Edgar Guevara Thank You for the suggestion, unfortunately we already have a cross polarized situation like the way you have shown in the paper. It really doesn't help in our case. But Nikolaos Kourkoumelis 's answer seems to be best option for us. I shall accept that as the best answer. Thank You both for the valuable suggestions.
In the case of a setup as shown in your schematic, you can use a trick described for example in the following paper.
https://www.osapublishing.org/boe/fulltext.cfm?uri=boe-9-12-6545&id=402741
By placing a quarter-wave plate between the objective and the sample they cancel reflection from all surfaces before the quarter-wave plate, that is from everything else than the sample. A quarter-wave plate should be ideally placed into collimated beam, so it's not optimal between sample and objective, but for a long-working distance objective should be acceptable.
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