Compactness

[arthurwolf]

Really awesome project!

This is huge (in terms of volume). I think this would be much more useful as a tool, if it was much more compact (say if you could have this easily added to a trichorder etc).

Does anyone reading this have any idea how it could be made more compact?

The internet has some designs for compact spectrometers, but I would be interrested in something even more compact if possible. You can see one such design here for example: https://img.laserfocusworld.com/files/base/ebm/lfw/image/2016/01/1305lfw01f1.png?auto=format&w=720

Could a prism be used instead of the diffraction grating? That sounds like it could be made more compact then. A very small motor could be used to move (rotate) the prism about if needed, there are minuscule stepper motors around, and I can help with finding and interfacing those if required.

The design of this project (PySpectrometer) looks a lot like this one, am I correct in my understanding there? https://www.hamamatsu.com/sp/ssd/product/Spectrometers/img06_en.png

Stacking mirrors also might have potential by increasing the number of reflections (still using only two mirrors) and therefore widening the prism/spectrum effect: https://media.springernature.com/m685/springer-static/image/art%3A10.1038%2Fs41467-018-06495-5/MediaObjects/41467_2018_6495_Fig1_HTML.png

Something like this has a similar concept to what I'm describing here : https://www.researchgate.net/profile/Manuel-Cano-Garcia/publication/338279737/figure/fig1/AS:845739789938690@1578651487502/Schematic-draw-of-the-proposed-spectrophotometer-An-Arduino-stage-drives-all-the.png but I would think it might be possible to make this even much more compact somehow ... just racking my brain for an engineering solution and have not found one yet. Curious if somebody else reading this would have an idea.

Maybe it could be possible to take advantage of the fact that we have a 2D sensor (instead of the strictly 1D sensor we actually need for spectra), by having several different prisms stacked on top of each other, creating different lines hitting the sensor on top of one another. This should be relatively easy to manufacture: it is simply a pile of flat panes of glass, on top of one another, with their entries and exists at different/varying angles (and presumably an opaque sheet of something between each layer). I can create a schematic of this if somebody is interrested and/or my description is not clear enough. It would also be very easy to make this very precise, by having two (or more) holes in each pane/plate/prism, and have a "pin" go through all of the holes in the stack for each series/stack of holes, thus ensuring perfect alignment of the prisms. This way, you would get on your sensor, a series of spectrum lines on top of one another, giving you a 2D array of spectral points instead of a line/1D array of such.

I hope I'm not saying anything too stupid...

Maybe it's not stupid: I found an image that looks like that idea: https://www.osapublishing.org/getImage.cfm?img=dTcqLmxhcmdlLG9lLTI2LTE1LTE5NDU2LWcwMDE

The interresting thing/goal of what I describe here, would be that it would be very compact, which is the objective/what I created the issue for. But if anyone else has any idea of how to make things more compact, I would be very interested to hear about it (I need very compact spectrometers to identify materials on an automated recycling/sorting CNC machine)

Sorry for rambling about this, I hope I'm not disturbing anything, I'm just trying to get a conversation going.

Cheers!