Re: spectrometer -- two dimensional imager

On 11/21/2011 01:19 PM, Simon Quellen Field wrote:
> Here is where the value of using a two dimensional imager comes into play.
>
> Tilt the imager, so the top row of pixels is where the green lines focus, and
> the bottom row of pixels is where the far red and far violet focus.

The problem of path lengths is not linear though... see my
non-reflective spectrometer sketch:

http://ecosensory.com/diybio/spectrometer_focus_problem-1.gif

You find curvy reflective hologram diffraction "gratings" for sale
for 2D imager chips.

It just hit me that they are to correct the setup you describe above.

I'm still wondering if a hologram lens in a transmissive film setup
could simplify, and where you find makers of such, and what are trade offs
of superimposing them.

Meanwhile Nathan is on a quest for flow cytometry, " with the right grating/optic
configuration you can disperse a spectrum with sub-nanometer per pixel resolution.",
"The double slit will reduce aberration, but it will also reduce the
signal a lot too." I'm sorry if I caused you any grief Nathan, but it took
so long to get your specs stated. If I'd known these before, I would not
have critiqued your ideas so much. You might get something working well,
and I wish you luck selling the high performance. Model a new kickstarter
after this one: http://www.kickstarter.com/projects/printrbot/1239090607
and you'll get a kick out of it. Notice how they offered the smallest,
easiest to assemble or modify, and got more preorders than donation premiums.
They got 115 backers at $500 for a full kit, unassembled. Only 8 bought stripped
down incomplete kits. 10 bought assembled systems for $250 extra

I've found a beagle-bone
compatible collaborator and will be evolving one of those for cheap --
mostly because Nathan jogged my thinking about them as I compared to Raspberry-Pi
modules for $35. The layout and schematics were done with proprietary
software, but the results show a working way to add decoupling caps
and route wires away from the dense package for its processor so
it's something to consider. There is an ecosystem of hardware and
linux bring up developers to get help from, that seems better established
than for R-Pi.

I can't see aiming for a performance spectrometer at this time, so I'm just collecting
notes for a "el cheapo robusto" miniature spectrophotometer selling some day
for $199 (and less the week between Xmas and new year's). maybe 2013.

John

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