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How Does a Laser Scanner Work? — Parallax Forums

How Does a Laser Scanner Work?

lardomlardom Posts: 1,659
edited 2010-12-19 22:02 in General Discussion
A cathode ray tube controls an electron beam with a magnetic yoke. How does a barcode scanner do it?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-12-19 15:03
    Rotating polygonal mirror(s) in the case of supermarket scanners. You can see one if you look through the glass.

    -Phil
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2010-12-19 15:06
    The beam gets directed by reflecting it off a small mirror that can be quickly positioned like that, a lot less work and stress than wig-wagging a laser assembly.
    Spin a faceted mirror-ball and speed goes way up.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-12-19 15:14
    PJ,

    Are you familiar with handheld laser scanners? I noticed that the ones at the local UPS Store have a beam with bright spots at the ends, which suggests a wig-wag type of scan. But one would think, in that case, that they'd make an audible "buzzing" sound, which they do not.

    Thanks,
    -Phil
  • lardomlardom Posts: 1,659
    edited 2010-12-19 15:40
    Thanks. I was curious. That means it would be difficult to use a laser to display a pattern. I'm guessing it would make more sense to shine a light through an LCD that has a computer generated image onto a surface through a lens. (Yeah, I know I'm going off on a tangent but I feel pretty normal on this forum!)
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2010-12-19 19:15
    The mirror deal can be used to laser pictures onto the sides of buildings:
    http://en.wikipedia.org/wiki/Mirror_galvanometer

    examples abound on youtube
  • kwinnkwinn Posts: 8,697
    edited 2010-12-19 19:21
    Phil Pilgrim (PhiPi) wrote: »
    PJ,

    Are you familiar with handheld laser scanners? I noticed that the ones at the local UPS Store have a beam with bright spots at the ends, which suggests a wig-wag type of scan. But one would think, in that case, that they'd make an audible "buzzing" sound, which they do not.

    Thanks,
    -Phil

    Some (most I have seen) hand held scanners use a linear imaging chip to read the bar code. No moving parts and no laser. Bar code is illuminated by a row of leds.
  • lardomlardom Posts: 1,659
    edited 2010-12-19 19:40
    I've seen laser light shows. So the galvanometer is how it's done... extraordinarily cool :cool:
  • kf4ixmkf4ixm Posts: 529
    edited 2010-12-19 22:02
    Alot of barcode verification systems that i've seen use a mirror mounted to a swivel that uses a magnetic coil to swivel the mirror back and forth, much like the way a dvd or cd player focuses its lens in front of the laser diode. most of the commercial units ive seen are made by SICK.
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