dclaar@hpcupt1.HP.COM (Doug Claar) (12/02/89)
This is probably a naive question, but how do you aim a laser beam? (I know, very carefully!). But seriously, are there non-mechanical methods to aim a beam, or must I rely on moving mirrors around? What do things like handheld laser barcode scanners and heads-up displays do? Are they mechanical?? Thanks, Doug Claar HP Computer Systems Division UUCP: mcvax!decvax!hplabs!hpda!dclaar -or- ucbvax!hpda!dclaar ARPA: dclaar%hpda@hplabs.HP.COM
piner@pur-phy (Richard Piner) (12/03/89)
In article <6220003@hpcupt1.HP.COM> dclaar@hpcupt1.HP.COM (Doug Claar) writes: >This is probably a naive question, but how do you aim a laser beam? (I know, >very carefully!). But seriously, are there non-mechanical methods to aim >a beam, or must I rely on moving mirrors around? What do things like >handheld laser barcode scanners and heads-up displays do? Are they >mechanical?? Most laser scanners use spining mirrors and electro-mechanical shutters. Some use electo-optical shutters, like LCDs. However, for really high speed laser stering, the neatest trick I've heard of is an ultrasonic diffraction grating. An ultrasonic standing wave creates a density sine wave in air, water, or other material. By changing the frequence of the sound, the grating spacing changes and hence the angle of diffraction changes. Very high speed, low mass system. Of cousre, there is the old trick of a mylar mirror on a speaker cone. If the speed of electrical response of non-linear optical materials ever gets high enough, electronic gratings will be a big application. R. Piner
henry@utzoo.uucp (Henry Spencer) (12/03/89)
In article <6220003@hpcupt1.HP.COM> dclaar@hpcupt1.HP.COM (Doug Claar) writes: >This is probably a naive question, but how do you aim a laser beam? (I know, >very carefully!). But seriously, are there non-mechanical methods to aim >a beam, or must I rely on moving mirrors around? What do things like >handheld laser barcode scanners and heads-up displays do? Are they >mechanical?? It is possible to deflect lasers (etc.) non-mechanically. However, it is a colossal pain to do, and substantial deflections are difficult. As far as I know, all "real" systems except perhaps some fancy military things use mechanical deflection. -- Mars can wait: we've barely | Henry Spencer at U of Toronto Zoology started exploring the Moon. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
aez@Data-IO.COM (Adam Zilinskas) (12/05/89)
In article <1989Dec3.000739.7513@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > >As far >as I know, all "real" systems except perhaps some fancy military things >use mechanical deflection. I worked on a laser system for an ultra-centrifuge that used the Bragg cell for switching the light beam. The Bragg cell is one of those pezioelectric crystals (I think I spelled it right) that builds up a diffraction grating when an appropriate high frequency signal is placed across it forming a standing wave. Yes you could "steer" the beam somewhat but the pattern coming out was a diffraction pattern. Bragg cell off the beam more or less went straight through. When on, the beam broke down into harmonics of the diffraction grating, lots of laser energy went off where we didn't need it. See crude ASCII below: OFF # 100% orignal beam ON . . , , * . * , , . . Harmonics^ ~25% leakage ~25% harmonics^ We tapped off on of the first order harmonics which gave us approximately 25% of the original laser power for a strobe to "snapshot" a sample rotating in the ultracentrifuge at about 10,000 RPM. The diffraction grating system is actually intended for modulating a beam rather than deflecting it. A more efficient system would be akin to the mylar on the speaker system where a pezio-electric cell would push a very small mirror to change the angles and thereby deflect the beam. Go to one of those Laserium shows and you will seem beam deflection at its finest. Adam Zilinskas
batman@watsci.uwaterloo.ca (Marcell Stoer) (12/05/89)
In article <6220003@hpcupt1.HP.COM> dclaar@hpcupt1.HP.COM (Doug Claar) writes: >This is probably a naive question, but how do you aim a laser beam? (I know, >very carefully!). But seriously, are there non-mechanical methods to aim >a beam, or must I rely on moving mirrors around? What do things like >handheld laser barcode scanners and heads-up displays do? Are they >mechanical?? > >Thanks, >Doug Claar >HP Computer Systems Division >UUCP: mcvax!decvax!hplabs!hpda!dclaar -or- ucbvax!hpda!dclaar >ARPA: dclaar%hpda@hplabs.HP.COM It's quite simple. Since a laser beam is just a light source, you use high transmission (99.9%+) optics for focusing your beam to what ever radius you want. You steer a laser beam with high reflectivity (laser quality ) mirrors. For some applications prisms or corner cubes are used. Prisms and some corner cubes use total internal reflection for bending a beam exactly 90 degrees. All of these optics must be of extremely high quality in order not to lose the coherency (spatial or temporal) of the laser beam. Marcell Stoer Centre for Molecular Beams and Laser Chemistry