Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!bionet!agate!eos!ames!amdcad!sun!imagen!hedley From: hedley@imagen.UUCP (Hedley Rainnie) Newsgroups: sci.electronics Subject: Re: deflection systems Summary: Heres another way Message-ID: <2734@imagen.UUCP> Date: 7 Dec 88 21:15:54 GMT References:<1372@cseg.uucp> Organization: Imagen Corp., Santa Clara CA Lines: 61 > Questions about laser positioning hardware Here is an article I saw about 2 years ago on net.analog: -------- From: agn@unh.cs.cmu.edu (Andreas Nowatzyk) Date: 5-Aug-86 18:52 EDT Subject: Re: Laser beam positioning anyone??? > > .... There is no known way to > do this positioning of laser beams without using mechanical positioners. > Sweeping statements like this are usually wrong. To wit: Philips used an all-solid state, digital laser beam delector for their Holographic memory research. That was more than 10 years ago. The scheme is pretty neat, so a brief description might be in order: +-+ ^ +-+ ^ +-+ ^ Leaser Beam in ------->|K|---/P\---|K|---/P\---|K|---/P\------> out +T+ / 1 \ +T+ / 2 \ +T+ / 3 \ | ----- | ----- | ----- A0 A1 A2 The linear polarized laser beam enters this 3bit delector from the left. The K-Boxes are Kerr-cells that can rotate the polarization plane of the beam. These are essentialy capacitors with some optical active medium. If a voltage is applied, the polarization plane is rotated. The voltages A0-A1 are set so that a '1' rotates the beam by 90 degrees and a '0' does not rotate the beam at all. The prisms P1-P3 are made of CaCO3 crystals. These crystals have 2 distinct difraction indices that depend on the polarization plane of the light with respect to a certain crystal orientation. Say that this difference is 1degree for P1, 2 for P2 and 4 for P3. Optical prisms can be manufactured with very tight tolerance, so you can continue this scheme for 10 or more bits (Philips used either 10 or 16 stages - weak memory). Assume that the unrotated beam has the lower deflection and A0=A1=A2=0 is said to be 0 deflection. So you get: A0 A1 A2 Beam defelction ----------------------------------- 0 0 0 0 1 1 0 1 0 1 1 2 1 0 1 3 0 0 1 4 1 1 1 5 0 1 0 6 1 0 0 7 This type of deflector can be made very fast (sub 100 ns) and precise (10-16 bit). In addition, you can build 2dimensional defelctors by adding a second deflector at the output, rotated by 90degrees. -- Andreas Usenet: ...!seismo!unh.cs.cmu.edu!agn --------------- -- {decwrl!sun}!imagen!hedley