From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 8/26/2015 3:21 PM, RichD wrote:   
   > On August 22,  Skywise wrote:   
   >>>> Lasers are useful for their low dispersion.   
   >>>> What I wonder is, why are they necessary for the   
   >>>> most common applications?  e.g. bar codes, CD readers,   
   >>>> My point is that collimated, non-coherent light   
   >>>> was developed long before the laser.   
   >>   
   >>> Sure, starlight for instance.  The problem with spatially incoherent   
   >>> sources such as LEDs and tungsten lamps is that in order to get a small   
   >>> focused spot, you have to trade away almost all of your light.   
   >>   
   >> Am I remembering correctly that the output from a laser is   
   >> 'appears' as a point source? And from that you can "get a small   
   >> focused spot" WITHOUT "[trading] away almost all of your light".   
   >   
   > I'm still unclear - if a light source is focused and   
   > collimated into a tight beam, where is the light "traded away"?   
   >   
   > I recall working on a photolithography project once, with   
   > a mercury arc lamp source, a series of (very expensive)   
   > lenses focused the light, worked fine.  Nobody mentioned   
   > anything about using a laser for greater efficiency.  As   
   > you can suss from my questions, I wasn't on the optical team -   
   >   
   > --   
   > Rich   
   >   
      
   If you do a Google Groups search for "sufficiently small heat engine",   
   the earliest reference is to a discussion in this group in 2004 that   
   puts this topic to bed pretty well, I think.  (The others are later   
   discussions that reference that one.  It's a bit of a FAQ.)   
      
   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   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)