A laser interferometer is on my todo list. I've acquired all of the optics on ebay for a total of a few hundred dollars. I've built a power supply. The major part I'm missing is the counting and interpolating electronics with a computer interface.
The system generates two pulse trains at about 4 MHz; a reference signal and a measurement signal. Each cycle of the 4 MHz represents a single wavelength of light. The difference in the number of cycles of each signal is the relative motion of the reference reflector and the measurement reflector. The electronic can just have two counters that are transmitted to a computer to display the difference. One can be fancier and do some interpolation to measure the relative phases of the two signals. That can yield an increase of resolution of a factor of a hundred or more. See: http://cp.literature.agilent.com/litweb/pdf/05517-90140.pdf for information on the principles of operation. Ken Anders Wallin wrote: >> 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. >> > > one picture and some text is now here. > http://www.anderswallin.net/2009/12/michelson-interferometer/ > I hope to analyze the data and post a result picture later when I have time. > > >> 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 ! >> > > Yes. You need two signals in quadrature. But how is this typically > achieved in a commercial instrument? These things must be very > robustly built if they are used in an industrial setting! > > > AW > > ------------------------------------------------------------------------------ > 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 > -- Kenneth Lerman 55 Main Street Newtown, CT 06470 203-426-3769 ------------------------------------------------------------------------------ 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
