The calibration light source is a fluorescent bulb.
It uses mercury vapor, which has distinct sharp lines in the red, green, and blue.
This makes it particularly easy to calibrate on a color sensor.
You just look for peaks in the red, green, and blue.
You ignore the white from the phosphors. It is much lower in amplitude anyway.
With a 2D sensor, you get a rectangle of light from a slit going through a grating.
If the sample is only in the top half of the slit, and the bottom half of the slit lets
unfiltered light through, then you can simply compare the values in the top half
with those in the bottom half to get the percentage of light that the sample has
absorbed. This is nice, because each image calibrates itself.
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Get a free science project every week! "http://scitoys.com/newsletter.html"On Mon, Nov 21, 2011 at 4:21 PM, John Griessen <john@industromatic.com> wrote:
On 11/21/2011 05:45 PM, Simon Quellen Field wrote:I think so.
Your two slit trick is just a bad way of trying to simulate a point source at infinity.
Instead, use a simple lens to collimate the light. Don't waste money on a lens
corrected for chromatic aberration -- the light is going into a diffraction grating. :-)
So, I hope it is now clear that your spherical aberration focus problem is simple to
fix by using a 2D sensor.
OK.
And the result will be guaranteed to be perfect focus,
without having to carefully adjust the focal length of the optics (which will always
be focused at infinity). So there is nothing to go wrong during assembly, and nothing
to get out of adjustment in shipping or use.
You need some simple light sources to calibrate, or is there a way with broad
The software auto-calibrates both in the
frequency domain and in the amplitude domain (using the trick of the sample only
blocking half the slit).
spectrum light with few distinct lines during normal use (Normal as in
white light through a bio sample)?
I'm not understanding the bit about "the sample only blocking half the slit". Is
that written up somewhere on scitoys.com?
Thanks, Simon
JG
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