I finally received my Thorlabs bandpass filter from the German branch office of Thorlabs. Postal service did cost 4.85€. I bought the 880nm bandpass with 10nm FWHM what should mean that 90% of the light between 870 and 890 nm should be visible. Additionally I bought a so called lens tube, which is used to “screw” in the bandpass and a C mount adapter ring to screw in from one side onto my C mount lens and on the other side to screw in the lens tube. (Summed up to 130€.)
Links:
Bandpass: http://www.thorlabs.com/thorProduct.cfm?partNumber=FB880-10
Lens tube: http://www.thorlabs.com/thorProduct.cfm?partNumber=SM1L03
C mount adapter ring: http://www.thorlabs.com/thorProduct.cfm?partNumber=SM1A9
Anyway, the results are counterproductive: I do not see my fingerprints anymore (I use Osram SFH 485s with 880 nm wavelength) but I do see lots of ambient light. The filter does not fit into the lens tube (to be precise: it fits inside but you can’t use the screw ring to fix the bandpass because the bandpass is a tiny bit too high). The C mount adapter ring does fit into the thread of the C mount adapter of my fire i cam but not onto my c mount lens what I supposed the ring to do (onto the C mount adapter directly it is useless because then I do not have a lens anymore
). I sent the whole thing back and asked them instead for this product: http://www.thorlabs.com/thorProduct.cfm?partNumber=FB880-40 maybe this bandpass does show my fingerprints. The Thorlabs staff is very co-operative: they are providing the new bandpass for me on a lending basis. I can test for two weeks if that bandpass is what I’ve been looking for.
I’ll keep you updated if this bandpass will work for me, anyway, do not order the lens tube or the adapter ring if you’re ordering a bandpass from Thorlabs.