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Nixi Tube vs. LED latency
james_s:
--- Quote from: jmelson on June 21, 2020, 02:09:54 am ---I built a laser photoplotter, it uses a 5 mW 670 nm laser to record images on film at 1000 X 1000 DPI, in raster mode. The pixel time of the laser is 5 us. The turn-on and turn-off of the laser is so fast, there is no motion blur of the pixels.
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That sounds quite interesting, is this project written up anywhere?
jmelson:
--- Quote from: james_s on June 21, 2020, 02:20:59 am ---
--- Quote from: jmelson on June 21, 2020, 02:09:54 am ---I built a laser photoplotter, it uses a 5 mW 670 nm laser to record images on film at 1000 X 1000 DPI, in raster mode. The pixel time of the laser is 5 us. The turn-on and turn-off of the laser is so fast, there is no motion blur of the pixels.
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That sounds quite interesting, is this project written up anywhere?
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Not as a complete set of plans, but I could make a bit more info available to anyone who is interested. One of the issues is it was completed in 1996, so used all parts in common use in 1995 and earlier. Ie. "old school". Now, it is just another one of the machines in my shop. But, if I was going to design it from scratch now, I'd use a lot of more modern parts.
See : http://pico-systems.com/photoplot.html For some more info and a picture.
It does a VERY accurate 1000 x 1000 DPI, which is required if two films were to be used for a double-sided PC board, or to make a solder stencil for a commercially-made board, which is what I now use it for mostly. I did make a few boards that were 7 x 11 inches, and the stencil lined up perfectly with the commercial PCB.
Most of the effort actually went into the program to convert Gerber files into raster format.
Jon
james_s:
Ah, it's drum based, cool. I was picturing more of a classical XY plotter style thing.
jmelson:
--- Quote from: james_s on June 21, 2020, 07:11:34 pm ---Ah, it's drum based, cool. I was picturing more of a classical XY plotter style thing.
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In the interim, while I was fooling with all the complexities, I added a "light pen" to my big Calcomp plotter. Itr DID work, but with a 0.013" writing beam, it took FOREVER to complete a single plot. Somewhere in the 45 minutes to over an hour range for a larger board. Then, for a PC board, you'd get black traces on a clear background, so you had to then contact print it onto another film to get clear traces on black background, for the photoresist. So, that really wasn't very workable.
The drum plotter produces 0.6" of plot per minute, no matter the complexity. So, a small board can be plotted in 5 minutes, a bigger one takes maybe 15 minutes.
Jon
james_s:
I was contemplating ways to make a photoplotter at one point, I forget what I was even trying to do but it occurred to me that plotting on a sheet of xray film would be a convenient way of doing it. These days I wonder if the easiest route would be to just use a TFT panel pressed right up against the film and give the backlight a quick flash. Maybe removing the backlight assembly and using a point source would give better results. Some of the displays used in larger phones and tablets can do some impressively high resolution and in many cases they are crazy cheap.
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