I bought a few laser diode modules on ebay. These are small brass tubes with a   
   tiny pcb inserted into a slot in the back. A lens is trapped inside the tube   
   in front. It is rated at 5 mw. I imagine this is similar to laser pointer.   
      
   Now, these are really useful for machining, because if it is aligned to   
   spindle axis, it makes it easy to see where drill will go - roughly. And if   
   there are scribe lines, accuracy is well below .001 in.   
      
   My question is: What is a low cost way to get a small dot size from these   
   things? I imagine a narrow channel painted black inside might help, until   
   diffraction takes over. I have seen a polarizer used as well.   
      
   Any ideas?  (PS the dot from these gizmos looks pretty diffuse - wonder if   
   these are rejects from laser pointers mfrs.)   
      
   JB   
      
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