From project website:
The prototype spectrograph is an experiment in low-cost design, and is almost entirely 3D printed using ABS plastic on an inexpensive desktop 3D printer (such as a Makerbot, though I used an ORD Bot Hadron). I have much more experience designing electronics than I do designing optical systems, and so the spectrograph is designed to be swappable/upgradable as newer designs come to pass (and I expect it to go throught a few iterations). This first spectrograph design has a 3D printed slit, and uses an inexpensive 1000-line/mm diffraction grating of the kind you can find on diffraction grating slides for classroom experiments. I read a paper a while ago on using deconvolution to post-process the data from slit spectrometers and basically sharpen the point-spread function (or PSF) to effectively increase the resolution of the instrument. Inspired by this, I decided to leave out the relay optics between slit-to-grating and from grating-to-detector to see if I could use post-processing to effectively sharpen up the overly broad PSF and have an even simpler and less expensive instrument.
The spectrograph design:
- contains a ~0.2mm printed slit
- 400-700nm (approx) spectral range
- Variable spectral resolution (~3.3nm @400nm, ~1.8nm @ 700nm), not accounting for the PSF
- 1000 line-per-mm diffraction grating (cut into a 4mm wide strip, and inserted into the spectrograph flush with the slit aperture)
- 3D printable on an inexpensive printer
- Very small size — about 1cm wide x 2cm long x 3cm tall.
With a spectrometer you’re often battling for SNR, and have to worry about stray light. Although these pictures don’t show it, the spectrograph has to be spray painted with a flat matte black paint to get any kind of performance.
Here is the PublicLab version of 3d printable spectrometer: