Hi Warren, My suggestion was to meaure the relative phase of the intensity variations, not the actual phase of the light, i.e. if the intensity at point a increases /decreases before point b then the fringes must be reaching point a first. David Whalley At 09:14 PM 2/4/99 -0500, Dr. Warren Smith wrote: >Perhaps you can place a small force (in a known direction) on the sample as >you observe the way the fringes shift. This will easily tell you the >direction of the height variation (probably a much simpler method than >trying to compare the phases of reflected light -- especially because >anything you try to do to compare the phases would require a measurement >way outside of the coherence length of a reflection!) ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################