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Lasers!

Discussion in 'LEDs and Optoelectronics' started by dssteven, Jun 15, 2012.

  1. dssteven

    dssteven

    47
    0
    May 9, 2012
    Hey guys,

    I'm trying to understand how the TopCon Laser-Zone connects to multiple targets. I guess I just don't understand a whole hell of a lot about lasers. Through googling and a bit of research I figured out a decent amount but what I'm really wondering is how this Laser-Zone can hit multiple receivers and relay to each one their Z coordinate. Basically the system gets the X and Y coordinates from a GPS system and then uses the Laser-Zone to get an accurate Z coordinate.

    The system I am referring to is here: http://www.topconpositioning.com/products/machine-control/3d/millimeter-gps-paving

    It says in the brochure here: http://www.topconpositioning.com/si...illimeter_GPS_Paver_Broch_7010_2034_Rev_A.pdf

    that the device can connect to multiple users. Maybe I am misunderstanding but are they suggesting the single wide angle laser beam (or is it multiple laserbeams in a wide angle spread? - Like I said, I don't know too much and they aren't giving too much info up)

    We use a Trimble TotalSystem for our 3-D concrete paving and I was just interested in how TopCon can connect to multiple systems.

    Any information is probably helpful!

    Thanks,

    Dan
     
    Last edited: Jun 15, 2012
  2. dssteven

    dssteven

    47
    0
    May 9, 2012
    I think I found their patent via google: http://www.google.com/patents?id=7p...=0CEEQ6AEwAQ#v=onepage&q=topcon laser&f=false
    EDIT: This is a patent from Trimble, looks like they are developing something similar though based on what I've read.

    Basically from what I've read, the lasers are emitted in different wavelengths and frequencies and sometimes even different spectrums. The laser receiver is then capable of deciding which frequency, wavelength or spectrum it should be reading from and uses that given signal.

    So does this mean there are indeed multiple lasers in the laser-zone systems? or does it just switch the one laser beam (somehow made into a wide angle spread) on many different frequencies or wavelengths or spectrums?

    If that is the case, why is Topcon the only company that is doing this? It would seem to me at least as a man who likes programming that it would not be extraordinarily difficult to program these lasers to emit different in different styles.


    If I'm way off here tell me because I'm just spit-balling as of right now.

    Thanks
     
    Last edited: Jun 15, 2012
  3. davenn

    davenn Moderator

    13,249
    1,746
    Sep 5, 2009
    Altho I work for the Trimble side of things, I dont deal directly with that particular equip
    I work on the GPS based heavy and highway gear rather than the surveying gear other than total stations

    that pdf file is an interesting read and I didnt get all the way through it. I dont know if Trimble are producing something similar or not. It wouldnt suprise me if they are. Competition is pretty fierce between the 2 companies.

    I suspect, from the initial reading I did, that the transmitter is transmitting on red,green and IR and the receiver is capable of receiving the same via filters. The system can look at the received signals and determine if there is an interefering light source because of its signal being present on only 1 or 2 of the colour channels....
    something along those lines of thought

    cheers
    Dave
     
  4. john monks

    john monks

    693
    1
    Mar 9, 2012
    A line is generated by focusing a laser straight into a solid transparent cylinder. The line comes from the fact that the laser light reflects around in the cylinder at different angles until the light finally escapes in the for of a straight line. I don't know how TopCon does it but I imagine that they have a laser with a transparent cylinder on a rotating shaft causing a vertical line of light to travel around in a full 360 degrees.
     
  5. dssteven

    dssteven

    47
    0
    May 9, 2012
    Okay, I've understood what you guys said about different targets, thanks a ton for the replies. Now I'm wondering how the Topcon laser can get a highly accurate z coordinate.

    Normally when using a laser you move the entire laser transmitter up or down and based on where it hits the photocell receiver is "zereoed" and where it hits when you move the receiver up and down, you get a z coordinate.

    The topcon has a vertical fan laser and can detect and determine z coordinate of the specialized target. My dilemma with this is if the laser is vertically fanned, it hits the target in multiple points. How does the receiver determine if you've moved up or down if it doesn't really have a singular reference point like it does with the solid beam as made by Trimble or Lieca? I'm just having some trouble grasping it and they don't exactly tell you how they determine your x-coordinate. If my explanation doesn't make sense, just let me know and I'll try to explain better.

    EDIT: Sometimes immediately after I post I come up with a solution to my problem so.. I think I understand how it works but I could be way off. With a fan laser, only one fraction of the beam is entering at exactly 90 degrees perpendicular to the target. It uses this small fraction of the beam as a reference beam and when you zero the target, it takes that point as zero and again uses the photocells to detect how far the target is from the zero position. Is this correct? maybe? Shoot your theories at me if you think otherwise. :) I'd love to hear them lol

    Thanks!
     
    Last edited: Jun 18, 2012
  6. john monks

    john monks

    693
    1
    Mar 9, 2012
    I don't how TopCon works but I know that if your transmitter is getting a gps signal and the receiver is getting the gps signal and the receiver gets the transmitter's position then the receiver can easily compute its exact position in xyz coordinates. So the transmitter must be modulating the laser with pulse code or something that the receiver can pick up in a few microseconds. As you probably know gps gives you xyz coordinates but it is accurate only to 70 some feet unless you get the military version. But if you already know the position of a reference point the error for both is the same and the error can be canceled out.
     
  7. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    That intentional built in error (Selective Availability) was removed in 2000 from public/consumer GPS... There are still differences between military and civilian GPS but for all practical purposes they both resolve to the same accuracy now... With supplemental support like that from WAAS (US) and EGNOS (EU) accuracy can be within a meter or so... While top of the line GPS units like those used for surveying and employing RTK can be accurate to one or two centimeters...
     
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