Can someone explain to me what the reflection optics module does? I keep seeing epi-fluorescence being associated with it but are they equivalent? For example if i want to see the surface of a microchip, do I need all the filters or just a beam splitter?
I’m also interested in the LED grid illumination. Does it only work with the transmission module or can I just use the reflection module?
The physical layout is the same for epi-fluorescence and reflection, but as you say reflection does not need colour filters. In fact it will not work with colour filters, they are designed to reject the return light unless it is at a longer wavelength than the illumination.
For reflection you need a neutral beamsplitter. Preferably 50:50 splitting ratio for the maximum brightness. When a colleague used reflection a while ago they had significant background scatter from the incident illuminaton that goes through the beamsplitter and hits the inside of the beamsplitter module. They felt a need to put a better black surface in there. I did not look at the time, so I am not sure how big the issue is and how we can modify the design to reduce it.
The LED grid can only be used in transmission.
Is there a reason why reflection and transmission can be achieved at the same time such as this:
But not with the reflection optics module in OF? It looks like a similar system to me?
Image from: Introduction to Reflected Light Microscopy
Yes, that would work. You just put the normal illumination on the microscope as well. You would need to be able to switch between the two LEDs
I was meaning that the LED grid illuminaton will only work for transmission through the sample, and you were talking about looking at the surface of a microchip. If you are looking at a range of samples then having both illumination methods is a good choice. (I have not seen anyone actually do it on the OpenFlexure Microscope)
Thanks a lot for the explanations. To clarify, what I want is the grid illumination for things such as cells and also reflection for microchips. As i won’t be using any fluorescence filters I’m assuming the only possible source of interference is the beam splitter? For now I only have one tube lens (had to get a friend to bring it from another country) so I can’t really make both optics modules.
It’s worth noting that the optics module with a beamsplitter is equivalent to the normal optics module if you remove the beamsplitter (and put some black tape over the hole). So, you can swap between the two modes without too much faff (though you will probably need to remove the sample - it’s not yet multi-modal imaging). It’s also worth noting the version with a beamsplitter is much less tested: it has worked, but it needs refinement and software support before it’s ready for lots of people to use it. Don’t let that stop you playing with it - I’m just trying to set expectations…
