Typiaclly they use a white light and send it thru a prism to break it into
colors. By moving a slit in the path of the output "rainbow" you can pick
the color you want and use that for the specific source. They rely on
specific color temperature lamps and calibrations to compensate for lamp
life etc. I worked on some alternative systems to that.

At 02:05 AM 4/13/98 -0400, you wrote:

>I am just a bit curious as to what kind of light source they use in
>spectrophotometers. I have played with one, and it has a rotary dial which
>can select any monochromatic wavelength from one end of the visible
>spectrum to the other. The whole device was only about 2 feet by 1 foot by
>8 inches. Seems like a pretty amazing light source in there! Cost about
>$5000, though!
>
>(For anyone not familiar with spectrophotometers, they are devices which
>measure the absorbtion/transmission spectrum of a chemical sample)
>
>Sean
>
>+--------------------------------+
>| Sean Breheny                   |
>| Amateur Radio Callsign: KA3YXM |
>| Electrical Engineering Student |
>+--------------------------------+
>Fight injustice, please look at
>http://homepages.enterprise.net/toolan/joanandrews/
>
>Personal page: http://www.people.cornell.edu/pages/shb7
>mailto:shb7@cornell.edu
>Phone(USA): (607) 253-0315
>
>
Larry G. Nelson Sr.
mailto:L.Nelson@ieee.org
http://www.ultranet.com/~nr