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Thread: "KPPS" technical definition/question

  1. #21
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    Also, if you don't want to mess with point placement at all, both RIYA and QM2000 have auto-optimizing vector input libraries. All your code has to do is draw the most basic lines and the libraries take care of scanner optimization.

  2. #22
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    Quote Originally Posted by drlava View Post
    Also, if you don't want to mess with point placement at all, both RIYA and QM2000 have auto-optimizing vector input libraries. All your code has to do is draw the most basic lines and the libraries take care of scanner optimization.
    I would definitely go that route if I was running on a PC. I'm going to try to adapt one of our little ARM based systems to drive the laser directly (instead of a vector monitor) though.

    (Yes, I'm making this way harder than if I just used a PC to write a game, but dedicated hardware has some advantages-- and I just want to try it. ...and throwing GHz worth of PC horsepower at a line based game just isn't even sporting! ;-)

    Thanks for all the pointers and tips!

    -Clay

  3. #23
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    Quote Originally Posted by havok1919 View Post
    (Yes, I'm making this way harder than if I just used a PC to write a game, but dedicated hardware has some advantages-- -Clay
    Like REAL TIME for example! ................. Thats music to my ears!

    Good on you cobber !

    Cheers

  4. #24
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    Exclamation KPPS definition .. confusing ..

    We r trying to build a DIY laser-show projector using BLDC motors with optical encoders + PLC for control.
    We r newbies and have some doubts regarding the ILDA test pattern:

    1) We have the same doubt as : havok1919/Clay.
    "Is a "point" defined as a move of a certain percentage of the display angle or something? (If there isn't a distance that a "point" implies I'm having a hard time understanding how the galvo could be rated in "point" units? Are these "20KPPS" points close together or far apart or what?"
    "if we have one line with endpoints at (0,0) and (100,0) is that two "points" or is that possibly 100 "points"?"


    2) For example: there is a square in the ILDA pattern. Is it made of 4 points or more points?

    3) I opened the ILDA pattern using LaserBoy software. It says there are ~1191 vertices in the pattern.
    Now if Iam tuning for 12KPPS, does that mean my frame rate during the tuning would be : 12000/1191 ~= 100 fps?

    4) Does anyone have the ILDA pattern co-ordinates as a ascii file or a DXF file?
    Would like to go thru the co-ordinates and understand what kind of anchor points, guiding points, blanking points etc. has been added to the pattern.

    regards

  5. #25
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    Quote Originally Posted by TanveerChawla View Post
    We r trying to build a DIY laser-show projector using BLDC motors with optical encoders + PLC for control.
    We r newbies and have some doubts regarding the ILDA test pattern:

    1) We have the same doubt as : havok1919/Clay.
    "Is a "point" defined as a move of a certain percentage of the display angle or something? (If there isn't a distance that a "point" implies I'm having a hard time understanding how the galvo could be rated in "point" units? Are these "20KPPS" points close together or far apart or what?"
    "if we have one line with endpoints at (0,0) and (100,0) is that two "points" or is that possibly 100 "points"?"


    2) For example: there is a square in the ILDA pattern. Is it made of 4 points or more points?

    3) I opened the ILDA pattern using LaserBoy software. It says there are ~1191 vertices in the pattern.
    Now if Iam tuning for 12KPPS, does that mean my frame rate during the tuning would be : 12000/1191 ~= 100 fps?

    4) Does anyone have the ILDA pattern co-ordinates as a ascii file or a DXF file?
    Would like to go thru the co-ordinates and understand what kind of anchor points, guiding points, blanking points etc. has been added to the pattern.

    regards
    Hi, it can be confusing, be sure to read the links in my first post above. There are a few things to keep in mind:
    The transfer function of control to optical deflection of traditional mechanical galvos (with drivers) can crudely modeled as a low-pass filter, with higher point rates input, past a certain frequency, giving greater and greater distortion on the output image.

    1) A 'point' in itself is nothing more than a DAC sample, nothing more, nothing less.

    However when used in the context of kpps rating of galvos, it's most accurately referring to the ability of the galvos to draw the 12-point circle so its edges meet the square at a certain scan angle. A scanset that can fit that requirement (typically) at 8 degrees total frame scan angle when the frame is being clocked out of the DAC at a sample rate of 30,000 smaples (points) per second is said to be 30kpps rated.

    2) it is made of more points, or 'optimization' points.

    3) about 10FPS, yes.

    4) if you have laserboy and have opened the test frame, you can not only iterate through the points to see for yourself, but can save as a text file as well. To iterate, press k to get to the points editor, and square brackets to iterate through.

  6. #26
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    Exclamation inverse kinematics calculation ...

    Hi,

    I opened the ILDA pattern file in the laserBoy and was able to see the "points" locations in the point-editor mode.
    Looks like the square has lot of extra points at the corners.
    My question is : 1) Are these "optimisation" points there in the orginal ILDA file or added by some other software.

    2) The co-ordinates in the ILDA file: Are these "X,Y" co-ordinates or "motor1Angle,motor2Angle" co-ordinates.
    I believe we need to do some inverseKinematics calculations to get motor-angles given the XY co-ordinates.
    Is this typically done for laser-shows or it is not so important?

    regards

  7. #27
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    Question ILDA pattern optimisation points ..

    Hi,

    I opened the ILDA pattern file in the laserBoy and was able to see the "points" locations in the point-editor mode.
    Looks like the square has lot of extra points at the corners.
    My question is : 1) Are these "optimisation" points there in the orginal ILDA file or added by some other software.

    2) The co-ordinates in the ILDA file: Are these "X,Y" co-ordinates or "motor1Angle,motor2Angle" co-ordinates.
    I believe we need to do some inverseKinematics calculations to get motor-angles given the XY co-ordinates.
    Is this typically done for laser-shows or it is not so important?

    regards

  8. #28
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    Quote Originally Posted by mixedgas View Post
    Portland/Vanc area? There are at least 4 laserists in your area.

    Come on WA laserists, at least one of you would like to see laser arcade games, help this guy out!

    Steve

    Here! How may I be of service?

    -Jonathan

  9. #29
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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    quote:
    My question is : 1) Are these "optimisation" points there in the orginal ILDA file or added by some other software. end quote.

    No, they are there as part of the design of the standard frame. The test pattern takes advantage of certain characteristics of a analog scanner amplifier PID loop, and the inertia of the galvanometer scanner rotor system.

    Quote:
    2) The co-ordinates in the ILDA file: Are these "X,Y" co-ordinates or "

    End quote.

    No, they are a X-Y plot.

  10. #30
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    Remember that galvo scanners work over small angles (8 degrees or such), and at small angles sin(x) approximately equals x and cos (x) approximately equals 1-x (where the angles are in radians) so for the small angles involved scan angle and x/y position become almost equivalent.

    Regards, Dan.

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