@WilliamW is right that you would want the
_infinity_f50d13_beamsplitter version of the optics, though you may want the picamera version rather than the m12 version if you’re using a Raspberry Pi Camera module. For the infinity-corrected version, the lens wants to be about 50mm from the sensor, so that parallel rays are focused onto the sensor. In reality, the distance isn’t quite 50mm, because the lens has a finite thickness, and so the plane that needs to be 50mm away from the sensor is inside the lens. That means the less curved side of the lens wants to be slightly less than 50mm from the sensor.
The optics modules with and without fluorescence are identical except that the beamsplitter-compatible one has a hole where you can slide in a filter cube. This allows you to couple in the excitation light using a dichroic mirror. It’s worth giving a word of caution here - the mounting for the fluorescence illumination is definitely the least nice part of the microscope at present! We are working on improving it; probably it will use the same optical components, but we’re trying to mount them a bit more solidly.