DPSS analog Modulation Frequency

Discussion in 'The Lounge' started by Laser Dude, Apr 17, 2006.

  1. Laser Dude

    Laser Dude Member

    Hello,

    What is the minimum modulation frequency recommended for analog modulation on a DPSS?

    I have seen Analog modulation specs at 10kHz or 15kHz.

    I would suspect the higher is better to allow for higher scan rates, but right now I am using cambridge 6800's tuned to 30kpps. Is 10kHz modulation frequency high enough for typical 30kpps scan rates?

    Thanks,
    Eric
     
  2. dmxlaser

    dmxlaser Member

    Hi Eric,

    The analog modulation specified in KHZ is the rate in which the laser can be switched on and off.
    So 10 Khz means 10.000 times per second it can switch on and off or change it's output.

    So you can change the output from 0 % to 100 % 10.000 times per second.
    As our eyes are only sensitive to anything below 60 hz you can see that the 10 khz rate is more then sufficient. The only difference is that with a 30 Khz laser you may get a smoother ( finer ) effect then with a 10 khz, but 10 khz will do just fine.

    Cheers,

    Peter
    DMXLASER
     
  3. JamesStewart

    JamesStewart New Member

    It would take more than 60Hz of blanking for most laser artwork Peter.

    Remember the way we use beams in this application. When the beam is moving, as is mostly the case, you will see (and need) much higher modulation frequencies.

    It's not just a laser graphics requirement. In a Q-Switched YAG it is clearly possible to see the beam modulating on scanned effects when it is running in Q-Switched mode.

    Returning to graphics though, it is important to consider also is the quality of modulation not just the maximum frequency. The problem becomes even more aparent when modulating three lasers in an RGB system simultaneously. If the modulation characteristics of all three lasers are not the same, this is where you start to see the horrible colour distortions appear in effects, and more so graphics.

    James.
    Laser Visuals
     
  4. misterre

    misterre New Member

    I have a question about analog and ttl modulation. What is the difference of these two? :confused:
     
  5. Selivandr

    Selivandr Member

    As I know modulation frequency defines fade in/out and blanking, but not scanrate. Scanrate is the characteristics of galvo.
     
  6. Pangolin

    Pangolin Staff Member

    TTL is an acronym for Transistor to Transistor Logic. It speaks to how the output of one integrated circuit is coupled with the input of another integrated circuit. TTL means that the output of the integrated circuit is a transistor, and the input of the integrated circuit is also a transistor. Before TTL, there was DTL, which means Diode to Transistor logic. It means that the output of the circuit was a diode, feeding the input of another circuit which was a transistor.

    The actual acronym and precisely what it means is not important in the context of modulation, but that's what "TTL" means.

    When used to describe blanking and color modulation, TTL is used to mean that the device has on-off characteristics. Analog on the other hand means that the device has variable output characteristics. So basically it means that devices with only TTL modulation capability can only be on or off, with no levels in between. Analog can have many levels, and can be used to fade in and out.

    Best regards,

    William Benner
     

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