Investigations

Investigation 6: Final Project Development

In this investigation, I will be further developing my final project — the ArtScan device — by delving into the underlying science of scanning technology. How do scanners work? Can this technology be miniaturized? If so, how far can the miniaturization go without losing scan quality? This last question is particularly important from a functionality standpoint, as artists require high-resolution scans of their artwork in order to carry out the digital editing process effectively to produce high-quality artwork.

There are four main types of scanners (flatbed, sheet-fed, handheld, and drum scanners) but I will be focusing on one of these types — namely, flatbed — because I would like to adapt flatbed scanner technology to the portability of handheld scanners without losing image quality.

This is a flatbed scanner.

The purpose of a scanner is to produce an exact digitized replica of the original scanned image or document. To do this, the image needs to be analyzed and processed. However, in order to turn a scan into usable text that you can edit or work with, you need optical character recognition (OCR) software on your computer. (This is beyond the scope of my project, but if you’re interested, you can read about how OCR software works over here!)

A flatbed scanner has various parts, each of which are required for the scanner to do its job. The most important part is the CCD (charge-coupled device) array. 

 This is the core part of the flatbed scanner  (and any type of scanner). This CCD array contains numerous photosites that are made of light-sensitive diodes. Each diode converts light into an electrical charge, and does so in such a way so that this electric current travels in only one direction. Within the CCD array, each photosite is light-sensitive so that brighter light produces a greater electrical charge within its diodes.

Scanners also use a set-up of mirrors, filters, and lenses so that the image or document being scanned can be digitized.  Combined with the CCD array, these mirrors, filters, and lenses make up what’s called the scan head. This is the part that moves back and forth as an image is being scanned. It’s attached to a motor by a belt in addition to a stabilizer bar, which helps the entire scanning head make a complete scan of the image. The mirrors are used to reflect the image onto each other, and the last mirror in the set-up (usually a second mirror or sometimes a third) reflects the scanned image onto a lens. This lens focuses the image through a filter and onto the CCD array by splitting the image into three smaller versions of the original image. Each shrunken version of the image goes through a colored filter, which are usually different colors (red, blue, and green). The different colored filters are needed in order to capture all of the colors that are on a full-color image. Some scanners actually scan the image three times — one for each color. (No wonder scanning can take so long!)

Capture

As you can see, this scanner is scanning in three different colors — red, green, and blue — one at a time, in order to capture the full-color image.

After going through the filter, the images then go through the CCD array, which has one specific spot for each mini image. At the end of the scanning process, the scanner combines the information from the three color-specific parts of the CCD array into a single full-color image.

Here is a useful diagram that simplifies this process:

Diagram

In short, here’s how a scanner works:

After placing an image or document face-down on the glass plate of the scanner, the scan head moves back and forth underneath the glass to scan. The lamp — usually a xenon-gas cold cathode lamp — underneath the glass projects light onto the document, which then bounces off of the bottom of the glass and is reflected by the series of mirrors to the lens, which focuses the image onto the CCD array. The CCD array then digitizes the projected image, and this information is what gets sent to your computer. (Here’s a cool animation that shows the scanning process!)

And here’s a video I found on YouTube that shows the individual parts of a flatbed scanner and explains how they work:

As for my final project, I think it would be possible to miniaturize the CCD array and a motorized scan head belt in order to produce a portable flatbed scanner. If CCD arrays have been miniaturized for digital pens, why not make a slightly bigger version for scanning artwork on-the-go?

The key for the ArtScan device, however, is the motorized scan head. If it’s not motorized, you would have to move it with your hand — which wouldn’t be very reliable. As a result, the image quality of the scan wouldn’t be as good as that achieved with a desktop flatbed scanner. The question now is how can motorized scanner parts be miniaturized?

ExtremeTech.com has hope for possible scanners of the future that are “flatter, cheaper, and better”:

“Much of the work being done with organic LEDs and super-flat components hints at a possible scanner of the future. Imagine a sheet not much thicker than a piece of paper, which could be placed between the pages of a book, powered through a USB connector. One could scan delicate or bound originals without having to disassemble the item or force it flat on a scanner bed. A scanner could be rolled up in a document tube and taken anywhere. Scholars and researchers would love it; people concerned with preserving national security would most likely despise it–unless they had something just like it, too. We probably won’t see anything like this too soon, but there’s no question the trends of “flatter, cheaper, better” will continue unabated for a long time to come.”

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