You can turn a diffuse source into a point source with a slit, but you
lose most of your light doing it.

Also, I built the electronics portion of a CCD spectrometer a few years
ago, a Harvard physics PHD did the optics.  He chose a compound three
element prism over a grating but I never got a good answer why.
Sometimes he claimed it made the calibration math easier.  Other times
it seemed to just be a visceral hatred of gratings!  What are the
relative merits of prisms vs. gratings?

Sherpa Doug

> -----Original Message-----
> From: Michael Vinson [mailto:mjvinson@HOTMAIL.COM]
> Sent: Thursday, January 17, 2002 9:05 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: photodetectors ( tag changed from OT)
>
>
> Josh Koffman wrote, in part:
> >What if you used a prism instead of a filter? Then place the
> >photodetectors at the correct output angle.
>
> I'm puzzled by all this talk of prisms. A diffraction grating works
> much better, at least in all the (physics) applications I've
> worked with. Regarding another comment someone made, you *can*
> use a diffraction grating with a diffuse source, you just need to
> send the light through a slit and maybe some additional optics.
>
> Michael V
>
> Thank you for reading my little posting.
>
>
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