Hi all!
First things first: Neil, I really hope I did not offend you. This had been the last of my intentions. As English is not my mother tongue, I might sound a bit harsh from time to time. It's a really impressive list of different areas you have covered during the years!
My experience up to now, is mainly Java web and desktop application development and some years with JavaScript now. Currently I am interested to learn some Go, as it would be great for multi-core CPU programming. For sure I did a bit of C++ years ago, but whenever I get in touch with it I realize how handicapped I feel with this language...
Regarding mechanical stuff, I also did service my motorbikes on my own. The precision part of the mechanics for sure is done by other engineers, just assembling. But enough to know, how to deal with this parts.
And long time ago, I went into a school for electrical engineering. But I never worked in this area. Hence, there are some hazy memories about electrical stuff, but it's all covered below a big layer of dust.
In the moment I would say, I could imagine to take an existing drum scanner and replace the electronically part. But only with a long and steep (re)learning curve.
I can imagine to pursue such kind of project as a real long term thing. Just to invest some hours here and there. Hence, for sure it would take more than some months to see something polished working in the end.
After starting this thread, I stumbled upon two ScanMate 5000 scanners. Not to far away of my home town. I took a look on them on Sunday and consider to buy both of them. One is broken, but the current owner thinks it should work, after fixing some damage done during transport. The second one is in working condition. I could use one to scan for now, have the second for spare parts and also as base for the DIY scanner project. We the working one (preview, focus and white point calibration), but could not do any scans, as the software lacks a dongle and we could not figure out how to get into demo mode. Next Sunday I will know more, as I bring my own old computer with SCSI connector to test...
Then I wanted to cover the points discussed up to now:
Bruce, for sure you are right! "First thing you do is, make a formal functional specification for it. If you can't do that, you can't make a drum scanner. You can't solve a problem that you can't define."
But first, one has to get a to a state of knowledge, one can define the formal functional specifications.
And of course, you are right. The whole thing is much more complex and complicated as I expected it in the first moment. Maybe it stays a thought experiment, but I like to play around with things like that.
Scan and rotational speed. Optical header positioning.
Of course it has to rotate as fast as e.g. 1600 rpms. If one scans a 8x10 inch sheet, you have 10 * 5000 (dpi) horizontal resolution. Divide by 1600 rpms/lines it's 31.25 minutes to do the scan. Actually straight forward, as soon as you do the simple maths. And for sure it also has to be positioned on every rotation in the gap to archive this scan speed.
Mounting / moving options.
I think rotational is the way to go, as moving linear in two directions would be slow and take long time. You would have to accelerate the table (?) and stop it again. This is for sure much slower than to rotate at constant speed and reposition for one pixel on every turn. Of course it would be easier to handle, but would produce scanning times of hours. I also think todays general use ADCs should be capable to take enough samples fast enough. But would have to checked of course.
light source:
LED would allow to skip the optical fiber to illuminate the sheet, but I guess to shape the light correctly, it would also increase the effort. The optical fibers give the light already a direction... not very scientifically, but I think you know what I mean.
Laser as light source. Would this mean to skip the optics to bundle the light into a focus point? I have far to little knowledge about laser light, to grasp the implications. Would the same photomultipliers be able to detect them?
jp, actually a drum scanner is some kind of lathe! just a very special kind of!
Luckily the taking of the image information is non destructive in this case!
Neil, you mentioned alternative sensors. What kind of them did you think of? Do you have examples?
Pali, precision for sure would be the most challenging part on the whole project. But starting with an existing scanner could be the key to avoid it for the beginning. After a prototype is there, one could replace existing parts with own designed ones. If this ever happens...
One point popped up my mind: color profiling!
Of course would have to be done with targets and software.
(Just a note for later: drum material perspex)
Well, this beast is really going to be complex. A one persons lifetime project!
I am interested to hear your opinions about this wrap up!
Greets,
Andreas
Just in case you are interested, the service manual for the ScanMate 5000: http://www.analogfilm.camera/wp-cont...vice-Guide.pdf
It has some valuable information about the schematics of the thing...
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