Where's my fast, smart, overhead scanner?


Back in 2008, I proposed the idea of a scanner club which would share high-end scanning equipment to rid of houses of the glut of paper. It's a harder problem than it sounds. I bought a high-end Fujitsu office scanner (original price $5K, but I paid a lot less) and it's done some things for me, but it's still way too hard to use on general scanning problems.

I've bought a lot of scanners in the day. There are now lots of portable hand scanners that just scan to an SD card which I like. I also have several flatbeds and a couple of high volume sheetfeds.

In the scanner club article, I outlined a different design for how I would like a scanner to work. This design is faster and much less expensive and probably more reliable than all the other designs, yet 7 years later, nobody has built it.

The design is similar to the "document camera" family of scanners which feature a camera suspended over a flat surface, equipped with some LED lighting. Thanks to the progress in digital cameras, a fast, high resolution camera is now something you can get cheap. The $350 Hovercam Solo 8, which provides an 8 megapixel (4K) image at 30 frames per second. Soon, 4K cameras will become very cheap. You don't need video at that resolution, and still cameras in the 20 megapixel range -- which means 500 pixels/inch scanning of letter sized paper -- are cheap and plentiful.

Under the camera you could put anything, but a surface of a distinct colour (like green screen) is a good idea. Anything but the same colour as your paper will do. To get extra fancy, the table could be perforated with small holes like an air hockey table, and have a small suction pump, so that paper put on it is instantly held flat, sticking slightly to the surface.

No-button scanning

The real feature I want is an ability to scan pages as fast as a human being can slap them down on the table. To scan a document, you would just take pages and quickly put them down, one after the other, as fast as you can, so long as you pause long enough for your hand to leave the view and the paper to stay still for 100 milliseconds or so.

The system will be watching with a 60 frame per second standard HD video camera (these are very cheap today.) It will watch until a new page arrives and your hand leaves. Because it will have an image of the table or papers under the new sheet, it can spot the difference. It can also spot when the image becomes still for a few frames, and when it doesn't have your hand in it. This would trigger a high resolution still image. The LEDs would flash with that still image, which is your signal to know the image has been taken and the system is ready to drop a new page on. Every so often you would clear the stack so it doesn't grow too high.

Alternately, you could remove pages before you add a new one. This would be slower, you would get no movement of papers under the top page. If you had the suction table, each page would be held nice and flat, with a green background around it, for a highly accurate rotation and crop in the final image. With two hands it might not be much slower to pull pages out while adding new ones.

No button is pressed between scans or even to start and finish scanning. You might have some buttons on the scanner to indicate you are clearing the stack, or to select modes (colour, black and white, line art, double sided, exposure modes etc.) Instead of buttons, you could also have little tokens you put on the surface with codes that can be read by the camera. This can include sheets of paper you print with bar codes to insert in the middle of your scanning streams.

By warning the scanner, you could also scan bound books and pamplets and even stapled documents without unstapling. You will get some small distortions but the scans will be fine if the goal is document storage rather than publishing. (You can even eliminate those distortions if you use 3D scanning techniques like structured light projection onto the pages, or having 2 cameras for stereo.)

For books, this is already worked out, and many places like the Internet Archive build special scanners that use overhead cameras for books. They have not attacked the "loose pile of paper" problem that so many of us have in our files and boxes of paper.

Why this method?

I believe this method is much faster than even high speed commercial scanners on all but the most regular of documents. You can flip pages at better than 1 per second. With small things, like business cards and photos, you can lay down multiple pages per second. That's already the speed of typical high end office scanners. But the difference is actually far greater.

For those office scanners, you tend to need a fairly regular stack or the document feeder may mess up. Scanning a pile of different sized pages is problematic, and even general loose pages run the risk of skipping pages or other errors. As such, you always do a little bit of prep with your stacks of documents before you put them in the scanner. No button scanning will work with a random pile of cards and papers, including even folded papers. You would unfold them as you scan, but the overall process will take less time.

A scanner like this can handle almost any size and shape of paper. It could offer the option to zoom the camera out or pull it higher to scan very large pages, which the other scanners just can't do. A lower ppi number on the larger pages, but if you can't handle that, scan at full ppi and stitch together like you would on an older scanner.

The scans will not be as clean as a flatbed or sheetfed scanner. There will be variations in lighting and shading from curvature of the pages, along with minor distortions unless you use the suction table for all pages. A regular scanner puts a light source right on the page and full 3-colour scanning elements right next to it, it's going to be higher quality. For publication and professional archiving, the big scanners will still win. On the other hand, this scanner could handle 3-dimensional objects and any thickness of paper.

Another thing that's slower here is double sided pages. A few options are available here:

  • Flip every page. Have software in the scanner able to identify the act of flipping -- especially easy if you have the 3D imaging with structured light.
  • Run the whole stack through again, upside-down. Runs the risk of getting out of sync. You want to be sure you tie every page with its other side.
  • Build a fancier double sided table where the surface is a sheet of glass or plexi, and there are cameras on both sides. (Flash the flash at two different times of course to avoid translucent paper.) Probably no holes in the glass for suction as those would show in the lower image.

Ideally, all of this would work without a computer, storing the images to a flash card. Fancier adjustments and OCR could be done later on the computer, as well as converting images to PDFs and breaking things up into different documents. Even better if it can work on batteries, and fold up for small storage. But frankly, I would be happy to have it always there, always on. Any paper I received in the mail would get a quick slap-down on the scanning table and the paper could go in the recycling right away.

You could also hire teens to go through your old filing cabinets and scan them. I believe this scanner design would be inexpensive, so there would be less need to share it.

Getting Fancy

As Moore's law progresses, we can do even more. If we realize we're taking video and have the power to process it, it becomes possible to combine all the video frames with a page in it, and produce an image that is better than any one frame, with sub-pixel resolution, and superior elimination of gradations in lighting and distortions.

As noted in the comments, it also becomes possible to do all this with what's in a mobile phone, or any video camera with post-processing. One can even imagine:

  • Flipping through a book at high speed in front of a high-speed camera, and getting an image of the entire book in just a few seconds. Yes, some pages will get missed so you just do it again until it says it has all the pages. Update: This lab did something like this.
  • Vernor Vinge's crazy scanner from Rainbow's End, which sliced off the spines and blew the pages down a tube, being imaged all the way along to capture everything.
  • Using a big table and a group of people who just slap things down on the table until the computer, using a projector, shows you which things have been scanned and can be replaced. Thousands of pages could go buy in minutes.


Why not use a scanning service?

I have, and they work fine, both piecemeal by mail-in envelopes and in bulk by shipped boxes.

Can do the job -- but they don't do ongoing scanning as new documents arrive, and they tend to be about 10 cents/page, which is an issue if you have many tens of thousands of pages. If you know of services that get down to more like 3-4 cents it can make sense. But you still want this fast scanner for your new documents. If you look at the cost of the components -- basic digital camera and a few other things, it should be cheaper than a nice document feeding scanner.

I can't help but think today's scanners are where cameras where pre-iphone. high res cameras are getting so cheap and so good, we've got to be only a year away from having your perfect scanner in a phone app. I'd love to be able to just hold my phone up while i flip pages on the table in front of it, have it auto-detect the page edges, and auto-format it into a combined PDF of all the scanned pages. it seems some apps are already out there that can do the scanning part, but not yet at high speed from what i could see.

That could happen, but there are a few things that will reduce the quality. Lighting is important. It must be even, and also offset so that reflections don't shine back into the camera. You need the lighting to be of a known colour.

For flattening the image, you either want the suction table I describe, or you can pull off the 3-D image. Having 2 cameras is good there, or structured light. You might see that in smartphones. And possibly two phones could accomplish the 3-D view required to remove any distortions from bending.

So yes, it might be a useful smartphone app to make for people.

In many ways, you could do a lot of this with just HD video which is then post-processed by a more powerful computer. HD video would only get you around 150 pixels/inch, but that's actually enough for a lot of documents. Certainly a smartphone holder with some white LEDs could be a nice kit to add to an app.

A scanner where you don't have to place the book flat face-down for every page... you just flip through it.


I've had similar scanner fantasies in the past, but not since I got a ScanSnap. It is pretty close to perfect. It can scan a stack of 30 pages front and back taking maybe 1 second of my time. It is small enough to leave on my desk, always read to scan. Drop int he documents and push the button and it immediately devours them.

I have mine set up to automatically save everything as a PDF and do OCR on it, although I don't seem to use the OCRed text as much as I thought I would. Instead I keep some major category folders under the scan destination folder. When things start piling up, I go ahead and drag completed scans into these sub-folders, which is good enough filing to find anything I need in a few seconds. This all works particularly well since the PDF files show up as thumbnails in the folders, so I can often find the document I am looking for by sight.

I was also surprised that it handles photos very nicely. It can very quickly scan a stack of loose photos that are all the same size to within maybe 30%. I do not notice any quality difference compared to my high end flat bed, and wouldn't care if I did because it scans so quickly and easily that I actually use it. You can scan a shoebox of similarly sized photos in a few minutes, compared to hours with a flat bed.

It does jam occasionally, usually because of an unnoticed staple or ripped page, but clearing a jam is quick and the software handles it gracefully with rational options to keep or discard the last scanned page, or to start the whole scan over again.

If you try the ScanSnap and still find yourself wanting, let me know and I can probably make you a quick but fully functional prototype that you could test to see if it was worth perusing the idea. My guess is that it would take <$100 in parts and a few days of effort to get something working.


I have an older, much higher end fujitsu scanner (5650) but I have seen the scansnap. I plaid with one recently and it was good but still could miss things in just a stack of papers. But perhaps it is getting there. But as I have said, in many cases, while the scanner is fast, the time to prepare the documents for a reliable scan can match the time to just slap them down on a table one page at a time, at least for single sided.

Just Google A3 lamp Scanner, or check out this YouTube video:

To get all the way you need:

  • More resolution
  • Working without a computer (ie. just store to flash drive)
  • Battery operation a plus (though not a total must)
  • Most of all, instant operation and the software to make it possible to just slap down documents as fast as you can and have it all work

Add new comment