SURVEY OF GAUGE BLOCK INSIDE CRYOSTAT. CONDITIONS IDENTICAL
TO LADDER, EXCEPT NO MYLAR FILM. SURVEY AREA IS ROUGHLY
27 X 2.7 cm**2, i.e. FULL FIELD FOR 10 ADJACENT IMAGES
STITCHED TOGETHER. TILT OF THE OBJECT HAS BEEN SUBTRACTED.

1. Lego plot.

2. Contour plot of 1 with proper aspect ratio.

The circular features have sagitta of roughly 10 microns;
they are simply an artefact of the divergence of the
laser beam (non-parallel light striking the object).
They are repeatable in every frame and readily subtractable.

Even without correction the survey is accurate locally
at the 10 micron level - already as good as the MIT OMIS2.


SURVEY OF DUMMY LADDER INSIDE CRYOSTAT.

3. Surface plot of image comprising 100,000 bins.
(i.e. data have been sparsified X100 from raw image)
Note: the field is wider than the ladder, hence ladder sides
clearly visible. Note the tilt. 
Note also the retaining bracket clearly seen at the bottom. 

4. Lego plot of 3, having removed the tilt. The data have
been further sparsified by a factor 100: i.e. 1000 bins in this image.
The ladder bow of roughly 100 microns is evident.
The survey artefacts can be seen as the 10 micron sagitta `ripples' 
superimposed on the ladder.

5. Contour plot of 3.

6. Lego plot after artefact subtraction: 4 - 1.
This represents a final image corrected for tilt and survey artefact.

7. Contour plot of 6. 


NB: The data sparsification is only for convenient display; all
10M pixels of the image are available and provide a relative height
measurement within a local area of 100 X 100 microns**2.