[Laser] Depth of modulation for various lamp types

[Charles Pooley]

F1AVY wrote:
  
>Infrared gives a better air transparency than the sodium yellow orange light. 
>So very under-powered classic thermal lamps could also work with a good 
>modulation....
  --------------------------------
  This will not work well.  The bandwidth for incandescent requires rapid cooling, which calls for the highest possible filament temperature.
   
  The radiated power, and cooling rate varies with T^4.  If you measure with a flat response photocell (or apply correction for wavelength depencency or use high speed bolometer) to observe the cooling of a filament after a lamp is turned off, you see a rapid cooling and an increasinly long tail of temp as the filament radiates more slowly as it cools off.
   
  In 1980 I designed a lamp driver which used filament resistance (roughly linear with temperature) to control a lamp.  The slow cooling rate as the filament cooled even slightly was obvious.
   
  Fastrest lamp will be a thin tungsten wire or ribbon--not coiled, at highest possible temp.
   
  Charles Pooley     KD6HKU     microlaunchers.com