Hi Anders W ! Happy to see some pic of your's prototype ! I have ever made an prototype interferometer to do measurement of distance. And I have some difficult to have a good signal on photodiode to have stable measurement. For that i know I think to know in which direction you are going you must detect the front side or down side of interference with two photodiode reading the same interference but with an difference of period T/4 in long ! Looks like absolute encoders ! The principle is said "phase detection" quadrant detection etc...
http://members.cox.net/rbirac2/Ebot/using_encoder.htm One link foud has is that explain briefly heterodyne phase detection for interferomter : http://www.google.com/url?sa=t&source=web&ct=res&cd=32&ved=0CBcQFjABOB4&url=http%3A%2F%2Fepsppd.epfl.ch%2FPraha%2FWEB%2F98ICPP_W%2FF054PR.PDF&ei=IVwrS5f9J- aL4gaRtKGSCQ&usg=AFQjCNFjEFKUOyPkBto0m5EaaOSMviBSnQ If you want detect the direction with one photodiode i don't know if its possible. Perahaps with an rampimg detection on the shape of interference , and have a different form of interference on right edge and left edge. And detect the zero stage of interference running. And finally have a resolution of 2lambda than one lambda but perhaps enougth... but more difficult in algorythme. waiting for others solution ... Le vendredi 18 décembre 2009, Anders Wallin a écrit : > Hi all, > > I built a simple interferometer for measuring the surface of a hand > ground/polished telescope mirror a while ago. > > Yesterday I removed the expanding lens and used a photodiode to > measure the interference fringes. I mounted the back-reflector on a > small motorized stage which has ca 100mm of movement range. It worked > OKish and I will post a pic and some results soon. With this simple > setup there is only one sine-shaped signal so I don't know which > direction the stage moves when I see fringes. > > I am wondering if anyone in the group has experience with a commercial > professional interferometer used for measuring machine tools? Any > links to sites that explain the principles? or papers? > > regards, > Anders W > > --------------------------------------------------------------------------- > --- This SF.Net email is sponsored by the Verizon Developer Community > Take advantage of Verizon's best-in-class app development support > A streamlined, 14 day to market process makes app distribution fast and > easy Join now and get one step closer to millions of Verizon customers > http://p.sf.net/sfu/verizon-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
