From: "James Lerch" 
To: "Nils Olof Carlin" ,
"ATM List" 
Cc: 
Reply-To: "James Lerch" 


----- Original Message -----
From: "Nils Olof Carlin" 

Hi Nils,

> I would think here that if measured along the optical axis, it will be
> as it should - only the optical axis isn't what you measure along.

You know, I have never quite understood this.  When you say "only the
optical axis isn't what you measure along" is this because the light
source and imaging device (eyeball or camera) are equidistant from the
optical axis?  (as in the optical axis is perpendicular to the midpoint
between the light source and imaging device?)


> You have shown figures for the total range, but if you take just the
> intermediate zones, is the travel proportinately less within this
> range too?

Pretty much,  Here's the full data comparison where

Couder = classic Couder mask eyeball test (average of Carl's and Our labs
results, which were very close)

Couder/Video = Still using the Couder mask, however replaced the eyeball
with a video camera and Television monitor.  Note, this was just a single
impromptu run.

Robo = average KE readings from the SOG (shade of gray) experiment

   Couder    Couder/Video    Robo
Z1    0                0                    0
Z2    .026        .026                .021
Z3    .046        .043                .047
Z4    .071        .072                .063
Z5    .095        .089                .093
Z6    .119        .114                .107
Z7    .143        .135                .133

We used the following mask for the Couder portions of the test:
http://lerch.no-ip.com/atm/comp/mask.jpg (36KB)

Whose zone openings were as follows: Z1 inner = 1"
Z1 outer = 2.52"
Z2 outer = 3.41"
Z3 outer = 4.12"
Z4 outer = 4.72"
Z5 outer = 5.26"
Z6 outer = 5.74"
Z7 outer = 6.19"



>And no doubt you have verified that the actual travel of
> the stage per step is indeed equal to the calculated.

YUP  a couple times actually!

I also added some code to Robo to monitor relative Lateral KE travel
between zone 1 and 7.  The results show 0.002" of lateral travel over
0.133" of longitudinal travel to keep the same 'Shade of Gray' value
during each zone null.  This means I have a little less than 1 degree of
misalignment somewhere between my camera, platform, and optical axis.


>
> there must be some rational explanation hidden somewhere.

I concur!  If the Couder results are indeed wrong (which we should know
shorlty) Then I'd suspect something about the mask is causing the problem.
(Operator error, mask layout, or some as yet unexplained phenomenon)

James

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