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Thread: CNC Laser Engraving 8bit Shades of Grey 445nm

  1. #151
    Join Date
    Sep 2017
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    Quote Originally Posted by JJWMACHINECO View Post
    Here is the original image I started with before any editing.

    Attachment 52807
    That is a spectacular image. Thanks for showing.

    Here's what I'm finding - although the laser may well be modulated - and although the response be fairly linear ratio of optical power out for amps in, the alternative of burn/not.burn is essentially binary. So it seems that the 'grayscale' is being produced by widening of the lines that varies with the joules/second delivered to the work.
    For a line to widen there are only 2 ways I can imagine- combustion, i.e., material burns that is not directly heated by the laser beam, or else the beam is wider than the effective burning 'circle' in the center of it and that expands with intensity. Can you confirm or correct that?

    Regardless of the exact mechanism, though, here's what the results show:
    http://imgur.com/a/dLH9o
    As can be seen, the best burn (10 bit modulation) is replicable with no more than 16 shades.
    In a lame analogy, the speedometer may say 1000 MPH, but the car isn't goin that fast no matter what.
    In fact, the color depth can be reduced to about 9 shades before there's any noticeable degradation of the image.

    At the moment, my little laser is on a cnc mill, so the speed is quite slow or i'd be burning a copy of that picture for a test. Perhaps I will make a machine optimized for lasering so I may dare to attempt the larger images... or- would you be willing to attempt burning that if I provide gcode for a true halftone?

    Or maybe I can just do a part of the picture for a test... lemme work on that...
    Last edited by GARCAD; 09-02-2017 at 18:33.

  2. #152
    Join Date
    Jun 2013
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    Florida
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    Click image for larger version. 

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    All you did was convert my laser photo engraving to 8 shades of gray.

    Click image for larger version. 

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    This thread is about laser diode image engraving with varied intensity, so go start your own thread on the forum about your old school 1bit halftone engraving method.
    Last edited by JJWMACHINECO; 09-03-2017 at 04:53.
    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

  3. #153
    Join Date
    Sep 2017
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    but I am talking about varied intensity.
    as you have demonstrated - 10 bits of modulation didn't get you more than 4 bits of color depth.
    can you show any burned image you have ever done that can not be reduced to 16 shades with no significant degradation?
    i've converted a section of that original image to test, btw. do you not want me to post that in your thread?
    if i start a new thread about the true spectrum achievable by varying intensity vs halftone, would you like to contribute to it?

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