Re: [Phys-l] A demo for biologists?

[Bernard Cleyet <bernardcleyet@redshift.com>]

That's fixed by using very "good" lenses and adding a pinhole  
(spacial filter).

bc

p.s. pinhole mitigates many evils at the expense of intensity loss.   
The better the source, etc. the less loss.


On 2009, May 15, , at 11:18, ludwik kowalski wrote:

> P.P.S.
> The process of expanding the beam with two lenses will probably
> destroy spacial coherence (because different "bundles of rays" travel
> through different thicknesses of glass in lenses). Placing the laser
> far away from the slide should produce a large enough (but still
> specially coherent) beam for the suggested below demonstration.
>
> On May 15, 2009, at 11:19 AM, ludwik kowalski wrote:
>
> > P.S.
> > A single expended beam seems to be a better, and simpler to  
> > implement,
> > approach.
> >
> > Ludwik
> >
> > On May 15, 2009, at 11:00 AM, ludwik kowalski wrote:
> > > One thing that biology students would probably appreciate is a good
> > > demo of "phase imaging." Here is an idea that I have never tried.
> > >
> > > Suppose a laser beam is expended (with two lenses) to a diameter of
> > > about 1 cm^2. Then it is split into two beams, like in an
> > > interferometer, and recombined into one beam projected into a  
> > > screen.
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