[ATM] Webcam Hartmann

[vladimir.galogaza at zg.tel.hr (Vladimir Galogaza)]

Mauritz,

>what is the optimum position of the camera plane
>with respect to (paraxial) focus, in terms of sensitivity?

To use camera resolution to its limit it seems that
it is the best if Hartmann spot pattern just fills up
CCD (or CMOS) detector of the (lensless) camera. 
Actually its smaller dimension of usual 640 x 480 pixels.

In that case   L = 2*d*Fnr.

L is distance of the detector plane from the focused source image
d is size of the detector and Fnr is F number of the mirror.
( Example, in my case: Fnr=2.5, d=3mm, L=15mm)


According to James Burrows it is better if camera is
"inside focus" that is intercepting the returning cone of light
before it comes to its vertex .


>I would expect that if one is too far away the difference
>between a spherical wavefront and the actual one is smaller,
>in terms of the measured diffraction pattern.

I do not get this. I think that diffraction pattern of Hartmann holes
is not arising from interaction of (reference) spherical wavefront
and actual one ( if this is what you meant). 
 I think of it as diffraction pattern of spherical
wave passing through  aperture ( in this case square one).

Vladimir.

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