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Thread: Laser Show Scanners and Scanning, the truth, the lies and a Review.

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    Default Laser Show Scanners and Scanning, the truth, the lies and a Review.

    Laser Show Scanners and Scanning, the truth & the lies ( If any exist ) and a review of the top 6 that we could find to test.

    Just putting together a lovely review about all the scanners I have on my table,

    I ordered two sets of scanners from six manufacturers over the past months to not raise any eyebrows, 12 boxes to open..

    All have been tuned by manufacturers as best they could with complex graphics being the target application.

    I post this now because I also would like to invite members to suggest testing methods which cannot be cheated or faked so that after I reveal my results, nobody can come with any BS excuses to why the scanners were not as good as the manufacturer claims them to be. Now is your chance to speak about how you would expect the tests to be done No point complaining after that your buddy's scanners were not so great after all..

    The scanners I have to test are from 6 Manufacturers who sent two sets of scanners separately to two different worldwide addresses ( finally I now have them all in and ready ) the opening of each box all 12 of them, will be done in front of a video camera to remove any manufacturer claims that the scanners somehow became damaged in transit. If anything is damaged then we'll consider that a fault of the shipper for not packaging the products good enough.

    I am also interested in opinions about software which claim to drive scanners at 30,000 points per second, but very few scanners can manage to project a 2,000 point image without strobe effects. ( Misleading data or based on some facts ?)

    Finally, after the tests have been done, I will offer the scanners for sale at 50% what I paid..

    Cheers for now.

    Andy
    Last edited by andyf97; 01-29-2017 at 04:26. Reason: The usual crappy grama correction

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    looking forward to this
    LASERS!!

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    ZPL Lighting www.zpllighting.com

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    Default You Asked for It...

    First of All, I can't accept most of your results. Two pairs per manufacturer is NOT a statistically valid sample. Ten pairs made in different months would just begin to scratch the surface.
    Plus your not doing a end of lifetime test... Even before you start, all pairs must be burned in for about 100 hours under identical conditions. Is it really fair to score what may be the best Galvo in the industry low because you two units of a bad batch, or tuned by a production worker on his or her cell phone for a few minutes??? With only two pairs, you may just do that....
    ~
    When I first read your post, I thought to myself "Poor Sod, he has no idea what he's gotten himself into". The ILDA test pattern is subjective, simply because its tuned by a human. The problem is the standard measurements of how a galvo perform in the lab have little to do with how it performs as a laser show graphics projection system... Which is why the ILDA pattern shines, it's simple, its accepted by most folks, and it works.
    ~
    If you read GSI's literature on Galvo tuning, you find there are four different initial tuning schemes for a classic analog galvo amp. There are two different definitions of rise and fall time used in data sheets right now. There are at least two different definitions of small and large angle. Some of the graphs your going to need to plot are three dimensional wire frames, especially for the response time vs scan angle. That is a lot of data to acquire, and I assure you that is four or more hours of work for each pair. Which version of the ILDA pattern are you going to use?
    ~
    The simplest way to test many things is to hook a oscilloscope to the current sensing resistor, the input signal, and the position sensor test point. But the sensor test point is NOT what the factory uses, well, because its output somewhat depends on the tuning of the linearity potentiometer.... The industry often uses a high bandwidth photodiode array with a data logger to look at settling time... And guess what... I bet NO two manufacturers set the position sensor scale to the same value. That means you have to locate the feedback point for each amp and measure it.
    ~
    So are you going to build the industry standard Jig? Yes, there soft of is one.... No, I cant just give you a copy of the plans because I need permission from SPIE to post the article here..... Do you have a decent theodolite to calibrate the all the scan angles during your measurement? Yes, he typed Theodolite... You need a laser with a very tiny, tight beam and always Gaussian transverse profile... Think low power green HeHe... That is because its transverse beam shape has a huge influence on how you interpret the scope trace when measuring angle and speed... A diode will not do for the most part..
    ~
    You even have to split your amps into categories, digital vs analog, vs analog with a notch filter.... PII circuit topology vs. PID would be a whole separate category... It is really unfair to compare an amp with a Notch to an amp without one... Trust me on that...

    ~
    Calculating the Mirror Inertia's will be well, fun, because the dimensions of the shaft and the mirror inertia matter... So does the first resonance, which when done without some very expensive hardware, is very subjective...
    ~
    Even the scope work is subjective, you'll need to do several trials per step angle, because of how the ringing decays on each small step in the galvo.. At work we make our students repeat measurements six times...
    ~
    So over the next few days I'm going to start posting the almost standardized Industry Standard definitions, how some of the tools operate, and a list of how things work... I'm going to hold you to those standards and journal articles, created by Engineers who design Galvo systems for a living...
    ~
    You need to read Bill's book. You should pick up a First Edition of "Laser Beam Scanning" edited by Gerald Marshall.. You'll need a copy of Red Alyward's and Bruce Rohr's papers on Galvo testing.
    ~
    Just off the top of my head... Four channel 100 Mhz oscilloscope with better then eight bit resolution and digital storage. Two fast photodiodes, Spectrum analyzer DC to 1 Mhz, tight laser with Gaussian Beam, A very long room with a very wide screen, Something like a Theodolite, a very high quality voltmeter, a very high quality programmable DC power supply with very good control resolution, a variable width pulse generator, and a QM32 or a QM2000 to ensure the ILDA test pattern is not Vector and has at least 12 bit resolution... A jig to position the scan head precisely compared to the Theodolite... Probably a high speed linear CCD...
    ~
    When you get done, I want to see at least:

    1. Small angle step time for angles from 0.5 to 5 degrees optical..
    2. Large Angle Step time for 0 to 30' optical in 5 degree or smaller steps. In a three D plot so we can compare units.
    3. First Resonance..
    4. Small Signal Bandwidth in Kilohertz...ie rolloff, 3db point, and how the angle falls off.
    5. Scope trace of leading edge and ringing for various step sizes,
    6. Residual noise
    7. Position sensor volts per degree..
    8. A good guess at the torque constant
    9. A good measurement of Coil mA per degree..
    10. Average current consumption when scanning a well defined ILDA pattern and a well defined circle...
    12. Response to a Delta Function (sharp pulse) input...
    13. Pics of test pattern and scope traces.
    14. A tape of a complex graphic (I use the Lightspeed Eagle animation)
    15. A frequency spectrum of a small signal jump...
    16. A sweep of the notch filter so I can tell a bit of what its doing...
    17. Mirror Inertia and Some things I have not thought of yet because I have not read the test procedure in a few years.....
    18. True usable beam size, per Bill Brenner's math...
    19. A measurement of sensor drift.
    20. Watts consumed by the coil under a few different conditions.
    21. Peak amps under a standard condition.
    22. Coil inductance and resistance hot/cold
    23. Linearity
    Five other things I have not thought of...
    ~
    And the last requirement, sending those amps out for test by another person for PEER REVIEW...
    !
    Steve
    Last edited by mixedgas; 01-29-2017 at 15:47.

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    ^


    Andy, can't wait for your test results.

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    Finale, I just asked for what is on a scanner data sheet by a serious western manufacturer.. Ie Cambridge or Scannermax.. Nothing exotic there, except the dynamic spectral measurments, Which are done but not shared by most manufacturing outfits, ...

    If you want the truth, measure the truth....

    Steve
    Last edited by mixedgas; 01-30-2017 at 12:25.
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    First thing:

    Obtain a copy of

    Testing high-performance galvanometer-based optical scanners Author(s): Bruce E. Rohr

    Date Published: 12 May 1995
    PDF: 10 pages
    Proc. SPIE 2383, Micro-Optics/Micromechanics and Laser Scanning and Shaping, (12 May 1995);

    -------------------------------------------------------------------------------------------------------------

    Here is one method for linearity...

    https://sem.org/wp-content/uploads/2...lvanometer.pdf

    -------------------------------------------------------------------------

    Steve
    Last edited by mixedgas; 01-30-2017 at 12:33.
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    Quote Originally Posted by mixedgas View Post
    First thing:

    Obtain a copy of

    Testing high-performance galvanometer-based optical scanners Author(s): Bruce E. Rohr

    Date Published: 12 May 1995
    PDF: 10 pages
    Proc. SPIE 2383, Micro-Optics/Micromechanics and Laser Scanning and Shaping, (12 May 1995);

    -------------------------------------------------------------------------------------------------------------

    Here is one method for linearity...

    https://sem.org/wp-content/uploads/2...lvanometer.pdf

    -------------------------------------------------------------------------

    Steve
    Useful links Steve, many thanks for those.

    Actually I was just getting goose bumps when reading about General scanning, It was GS scanners which I first used back in around I think 1983. of course i could not afford to buy them,. Instead they were donated to me from the guys at Laser Creations because I was so passionate about the subject. The scanners were with torsion bars. Just trying to remember the model, I think they were G124Dt but few!, its like 35 years ago and makes me feel like a grandpa.

    Later I had a of scanners from a company called LSK, http://www.laserscanning.com LASER SCANNING KEISER AG established 1987. I first saw some of there scanners at am expo, the scanners running a little demo of a helicopter flying around on a table.

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    Steve, I'll test those things before breakfast. Anything else?

    What scanners are included in your test?
    Sincerely,
    Ryan Smith
    ScannerMAX Mechanical Engineer
    ryan {at} scannermax.com

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    Really looking forward to seeing the test. Out of Steve's 23 suggested tests, only two of the points are relevant to me. The actual results of how the scanners draw the beam. What is the final result an hobbyist can expect from each model tested.

    When buying a new car, you can read all the specs you want, but you need to drive the car to actually get the feeling of the performance.

    What I would like to see:
    ILDA testpatterns.
    Scrolling text is always a challenge
    Compared size of output from same distance with same settings.
    Performance small angle and wide angle. At what stage does each model begin to struggle.
    What mirrors are standard shipped with model (if not specially ordered for the test) size and reflectio rate.
    Noise they produce during operation

    And probably some more when I have time to think this through.

    Espen
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    What about the chinascanners that can do 2MILLIONkpps at 500 DEGREES

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