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Would anyone be capable of making a barcode reader with vacuum tubes?
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Psi:
You could make a 386 CPU out of vacuum tubes and play doom, but at 100khz clock it would take at least 40 seconds to render 1 frame and consume 1.5MW of power.  (colossus was 1500 tubes and 8kW and a 386 is 275,000 transistors).
T3sl4co1l:

--- Quote from: Someone on November 20, 2021, 06:09:38 am ---
--- Quote from: T3sl4co1l on November 20, 2021, 04:30:13 am ---But it's a lot harder to do that with when every bit of storage and every gate of logic costs multiple whole tubes!
--- End quote ---
You're possibly jumping to the same digital calculation blinkers that people are discussing above. Given tube era technology, leave as much of the processing in analog as possible! Delay lines (liquid metal, ultrasonic, etc) for "memory", then plenty of optical and frequency domain processing. Avoid digital wherever possible.

Get a solid checksum/verification solution/design, and spam random orientation and scale until something falls through the sieve.

--- End quote ---

Yes -- if the requirement is electronic rather than electromechanical, and largely off the shelf (heh, for as many tubes as you can find on the shelf, anyways), it might be something like I said.  Granted, I'd allow delay lines and optical masks, to the extent you're willing to make them.  Though I'm not sure what you can do with them exactly.  (Obviously, delay lines let you multiply the stored bits/tube, but you still need to get the bits in and out of 'em.)  One of the differences with not being familiar with that technology!

Optical masks, I wonder if a shift register for converting time to space would do (can include any sort of raster scan, like a CRT), then using perspective transforms (aha!) to shift the spacial frequency, then vary the scale factor (distance between scanner and projector) until it picks up the clock frequency (by tuned circuit).  Would be neat to use Doppler to do rate conversion but I'm not sure what you'd use for a medium.  Oh, or heck, just short all that out, I wonder if that can be done by adjusting the optics themselves (e.g. zoom lens).  Or even less complicated still, maybe the laser beam can be projected parallel, rather than swept-angle so the scanned frequency is only sensitive to relative angle and parallax.  Yeah, and then instead of a prismatic mirror it could be tapered or something, and the scale done by scanning along that in turn.

Scanning one variable-geometry parameter, while also scanning the barcode itself, is kind of dubious in terms of missing combinations (if harmonically locked, they trace a certain regular path), or warping caused by combined relative motion (particularly at low ratios of scan rate), or requiring massive scan rates (like a TV raster -- mechanical TV isn't exactly practical).  If they're not harmonically locked, they'll eventually hit most combinations, and like you say, a good verifier only needs it to work once.

Oh, and hey, a lot of algorithms effectively throw away partial results in the course of a search; instead of wasted computation, why not just throw away useless input instead? :P  Another thing we take for granted, being able to compute a whole load of stuff at once; like the difference between mechanical scanned (samples each location only very briefly) vs. vidicon TV (continuous optical integration), however in this case we have very little limitation imposed by intensity / SNR so can afford to make exactly such a trade in the opposite direction.  Or of FFT vs. sweep in spectrum analysers.

Or you just don't care about perspective/rotation, and stipulate that the scanner has to be held near a particular distance and angle, and it just doesn't recognize a scan for higher frequencies (distances).  That's honestly not too useless, I mean everyone already has the experience that scanners can be picky.  Maybe emboss the design a bit, so the scan head kinda keys into it, that wouldn't be expensive to do with cardboard cartons, or attach suitably shaped placards to wood/metal/etc.

Tim
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