Re: [ATM] Bench star test

[Jarvis Krumbein <jkoptic@juno.com>]

Laser diodes do not make good point sources because the diode emissions
are generated in a short very thin line.  If the diode is not lasing,
then the light source is excellent for use in the Foucault  or Ronchi
test setup.  The diode must of course be rotated until the light source
line is parallel to the knife edge or Ronchi screen.

Jarvis Krumbein

On Mon, 4 Jun 2007 17:30:38 +0200 "Vladimir Galogaza"
<vladimir.galogaza1@zg.t-com.hr> writes:
> Dale,
> 
> > Laser diode's without their lens make a very good point source.
> 
> I have my doubts about this.
> 
> If a "point source" (an oxymoron in itself) is a source that has
> small physical size. than laser diode is really small source (few 
> microns).
> 
> If "point source" is considered to be good approximation for
> source of spherical wavefront than, I  think,
> laser diode (lensless) has lot of aberrations in spite of its small 
> size.
> Astigmatism, for example.
> 
> I have used it in Foucault tester and had problems. I will try 
> spatial
> filtering to see if this  can improve on wavefront sphericity and 
> thus
> verify my assumption.
> But  required spatial filter is not a trivial thing to construct, at 
> least 
> for me.
> 
> Regards
> Vladimir.
> 
> 
> 
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> 
> 
 
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