Comparison of Real Foucault Images of a Telescope Mirror and Simulated Foucault from Interferometric Data
Dale Eason May 25 2006
The
top row of images are the real Foucualt Images of an 8 inch F5.3
Telescope Mirror. The second row are the simulated Foucault
images created from the interferometric data of the same mirror.
I think they are very similar except at the edge. The simulated
images show a diffraction ring where none really exists. I'm still
working at characterizing the false artifacts that arise from my
process. Some of which are:
- ringing at the edge
- Underestimated surface bump height (the smaller the area of the bump, the more it is underestimated)
- Flattening and widening of surface features
- Additional false bumps
Below
is top level view of the surface as computed by the interferometric
software as compared to the best fit paraboloid. Red is high
surface, blue is low.
Below
is a profile through a diameter of the mirror to help show the scale of
the surface error. The purple line is the profile computed by
FigureXP using a 7 zone mask. The adjuster in the upper right
corner shows the angle of the diameter measured. I picked this
diameter because it seemed to be the closest match to the FigureXP
measurements. The vertical scale is in nanometer deviation from
the perfect paraboloid.
Last here is a view with exaggerated height. Just because I like it. The box around it is 1/8 wave heigh.
