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| What's a good printer for minimal usage ? |
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| tooki:
--- Quote from: tom66 on February 14, 2023, 11:03:13 pm ---LED printers fascinate me. If it's a 600 dpi printer, you need over 5000 LEDs to image a typical row of A4. Are they using an OLED module or just discrete LEDs in some kind of custom package? --- End quote --- Neither. The LED assembly is, if I understand it correctly, assembled out of a few LED arrays, which are essentially “ICs” of LEDs, much the same way that we build billions of MOSFETs, diodes, etc. into a processor die (or pixels in an image sensor), we can make hundreds of LEDs within a single die. Modern LED printers have 1200dpi printheads, so about 10,200 LEDs across an 8.5” maximum page width. See https://www.eevblog.com/forum/projects/led-_laser_-printer-illumination-bar-hacking/ where there is more discussion on the technology, including very informative source documents. --- Quote from: tom66 on February 14, 2023, 11:03:13 pm ---Is the module small and scaled to fit the page with lenses, or is it the size of the page? --- End quote --- It is the width of the page and uses lenses. But the lenses are tiny and numerous. See the PDF attached to one of my replies in the thread linked above. --- Quote from: tom66 on February 14, 2023, 11:03:13 pm ---Early DLP projectors had a way of doubling resolution by 'shaking' the DLP chip up and down slightly, effectively creating an interlaced pattern. Maybe vibrating the drum could achieve some kind of micro-resolution improvement. --- End quote --- You really wouldn’t want to vibrate the imaging drum, as I would think that would blur and dull the image by physically shaking the toner that’s on it. The now-discontinued Xerox wax printers (which were basically inkjet printers with page-wide printheads that sprayed molten wax instead of aqueous ink, and sprayed it onto a transfer drum rather than directly onto the paper) oscillated the entire head assembly horizontally to do exactly what you are thinking. (IIRC, it oscillated the width of 6 dots at the standard 600dpi, so that the printhead itself only needed to behave nozzles 1/100” apart.) It’s unnecessary on LED printers since getting 1200dpi out of a semiconductor is trivial, by making the diodes small enough and really close together. |
| westfw:
Packing 5000-10000 LEDs across 200mm isn't that much more amazing than the way they can pack in inkjet nozzles! |
| tooki:
Incidentally, the CIS (contact image sensor) scanner elements that are used in most scanners today (both flatbed and ADF) are essentially the same construction, just with linear image sensors instead of linear LED arrays. The page-wide arrays of tiny lenses look almost identical. Scanners of course also have a second line of tiny lenses for the LED light source used to illuminate the paper. In some scanners, the sensors are RGB and white light is used; in others (most, I think), the sensor is monochrome and they use RGB LEDs to sequentially scan each color (so quickly that it looks like white light to the naked eye) with a single pass. (Anyone remember 3-pass scanners, which used color filters to scan RGB in completely separate passes, and grayscale by leaving out the filter? You didn’t dare touch the scanner mid-scan because even tiny misalignment of the scan passes would ruin the scan…) |
| tooki:
--- Quote from: westfw on February 14, 2023, 11:48:39 pm ---Packing 5000-10000 LEDs across 200mm isn't that much more amazing than the way they can pack in inkjet nozzles! --- End quote --- Absolutely! 1200dpi is much more impressive in a micromechanical semiconductor like inkjet than in LEDs, if you ask me! |
| james_s:
--- Quote from: tooki on February 14, 2023, 11:49:46 pm ---(Anyone remember 3-pass scanners, which used color filters to scan RGB in completely separate passes, and grayscale by leaving out the filter? You didn’t dare touch the scanner mid-scan because even tiny misalignment of the scan passes would ruin the scan…) --- End quote --- I still have a HP 3 pass scanner in my mom's garage, it uses three separate CCFL lamps to illuminate the image. I remember working on another scanner maybe 20 years ago that had a color filter drum with a stepper motor, I don't remember if it was 3 pass or if rotated the filters as it went along. The first scanner I actually owned was a single pass color flatbed I bought for around $150 back in 1997 shortly after I got my first job. The price of flatbeds dropped massively right around then, previously they were >$1k. |
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