You may be able to work backwards.  Lift off using reversal depends upon the
refractive index of resist bending the exposure light to create a reverse angle.
As most positive resists have a lift off angle of  22 degrees out of vertical.
Assuming the unctrilled collimation is held to 1 or 2 degrees to create a 22
degree lift of angle requires that the light is bent through about 20 degrees.
Hope this helps.  Bill Moffat

________________________________

From: mems-talk-bounces@memsnet.org on behalf of Chris Bliss
Sent: Tue 3/20/2007 10:08 AM
To: 'Peng Li (Paul)'; 'General MEMS discussion'
Subject: RE: [mems-talk] measure refractive index

Hello,
Abbe refractometers are common instruments used to measure the refractive
index of liquids. A web search will provide a list of vendors.
Cheers!
Chris Bliss

-----Original Message-----
From: Peng Li (Paul) [mailto:lip@egr.uri.edu]
Sent: March 19, 2007 11:55 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] measure refractive index

Hey all,

Does anybody know what kind of instrument can be used to measure the
refractive index of liquid? Which vendor and what products do you recommend
for use?