On Thursday, January 23, 2014 10:31:12 AM UTC-5, Phil Hobbs wrote:   
   > On 01/23/2014 09:50 AM, Joe Gwinn wrote:   
   >   
   > > In article , Phil Hobbs   
   >   
   > >  wrote:   
   >   
   > >   
   >   
   > >> Hi, all,   
   >   
   > >>   
   >   
   > >> I have a gig to design a microplate reader for a new bioassay system.   
   >   
   > >> To match the reagent systems, it needs to work over a range of   
   >   
   > >> wavelengths in the 340-500 nm region, none of which is particularly well   
   >   
   > >> matched to mercury emission lines.   
   >   
   > >>   
   >   
   > >> So, I'm casting about for a light source.  It really doesn't need much   
   >   
   > >> power, maybe a few milliwatts per square cm in a 5-nm passband.   So   
   >   
   > >> 5-10 W output would be fine for an arc lamp, much less for a LED.   
   >   
   > >>   
   >   
   > >> For particular purposes, I can get LEDs in almost any wavelength I need.   
   >   
   > >>    However, it would be very useful to have a broadband source.   
   >   
   > >>   
   >   
   > >> Most white LEDs appear to cut off very sharply below about 420 nm, which   
   >   
   > >> is pretty understandable given that that's the short wavelength tail of   
   >   
   > >> the blue LED chip.   
   >   
   > >>   
   >   
   > >> High pressure xenon lamps have nearly flat spectra in that region, which   
   >   
   > >> would be terrific if I could find one rated at less than a kilowatt.   
   >   
   > >>   
   >   
   > >> Any lamp- or LED-selection wisdom?   
   >   
   > >   
   >   
   > > How about a pulsed xenon flashlamp, ie, a stroboscope?  These are   
   >   
   > > easily built.  (I built one to stop motion in a coil winder, so one   
   >   
   > > could diagnose winding problems.  The flash is triggered from a axle   
   >   
   > > position sensor, so the image stands still regardless of rotation   
   >   
   > > speed.)  Pulsed at low power (relative to the capacity of the flashlamp   
   >   
   > > in question), the life can be quite long.  The pulsed output fits into   
   >   
   > > lock-in amplifier schemes nicely.   
   >   
   > >   
   >   
   > > Joe Gwinn   
   >   
   > >   
   >   
   > Thanks, Joe.   
   >   
   >   
   >   
   > That's the approach that a lot of existing microplate readers use.  The   
   >   
   > problem is the pulse-to-pulse variation, which hurts the measurement   
   >   
   > repeatability.  Something nice and stable like a LED would be my first   
   >   
   > choice.  I may wind up with a white LED with a violet and a UV one for   
   >   
   > fill-in, but that's a bit on the messy side and tends to waste light.   
   >   
   >   
   >   
   > The sample will be in rapid motion during the measurement, so an arc   
   >   
   > lamp is a possibility.   
   >   
   >   
   >   
   > There's some specification creep happening at the moment.  Originally it   
   >   
   > was a single-wavelength system, where a filtered LED would have been   
   >   
   > just the ticket, but now it looks more like a fibre-coupled spectrometer.   
   >   
   >   
   >   
   > Cheers   
   >   
   >   
   >   
   > Phil Hobbs   
   >   
   >   
   >   
   > --   
   >   
   > Dr Philip C D Hobbs   
   >   
   > Principal Consultant   
   >   
   > ElectroOptical Innovations LLC   
   >   
   > Optics, Electro-optics, Photonics, Analog Electronics   
   >   
   >   
   >   
   > 160 North State Road #203   
   >   
   > Briarcliff Manor NY 10510   
   >   
   >   
   >   
   > hobbs at electrooptical dot net   
   >   
   > http://electrooptical.net   
      
   Phil   
   I saw a Xenon "short arc" lamp - 75W at Newport Co. website. Pricey. (300-1200)   
   We used water cooled versions in weatherometers.   
   Have you approached lamp companies like Phillips with your specs?   
   I'm shooting in the dark, but how broad is spectrum from a simple CFL?   
   jb   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)