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What nobody seems to understand is the circle in the square in the ILDA TEST PATTERN measures the approximate "3 dB Down" point of the galvo frequency response at a specified test condition.

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The test pattern is a unit of measurement set up so artists who are non-techies and techies who are non-artists can get a figure of merit both sides agree on for a given galvo pair under standard conditions.

It gives us a common reference to interchange vector artwork and to tune the galvo servo loops, without needing a table top full of test gear. . 30Kpps is roughly a 2.4 KHz galvo response bandwidth for very short jumps. As that bandwidth available changes with angle, decreasing with larger jumps, the angle of the standard test pattern projection is specified and the sample rate for its reconstruction is specified.

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There is no easy formula to convert KPPS to a galvo frequency response , because the equation approximating the motion of the galvo under closed loop control is a very complex polynomial.

1/KPPS (ie..the reciprocal) is the time in seconds between DAC output updates.

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KPPS in terms of the DAC and Software is the update rate per point in the image without any image optimization or vector processing applied. Then you can assume the galvo acts as a complex, non-linear low pass filter with a integrated memory of its last positions and some resonances if driven out of its ballistic response region. There are whole books on Galvo dynamics, it is not an easy subject to understand.

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Closed Loop Galvos have a frequency response of DC to low audio.

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Steve

Last edited by mixedgas; 01-21-2019 at 08:58.

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When I still could have...