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16 January 2004

Science Notebook: Doing Science with a Digital Scanner

There was a time when doing many kinds of science required the construction of specialized instruments and gadgets. While some of us still engage in this activity, plenty of science can be done using relatively simple commercial appliances.

One of the most interesting of such devices is the digital scanner. At the beginning of the personal computer era, these wonderful tools cost thousands of dollars. Because I could not afford a scanner, I once designed my own by replacing the ink pen of an HP7470 xy plotter/printer with a photodiode connected to the joystick of a desktop computer. A simple software driver written in BASIC allowed this simple contrivance to scan printed characters and drawings and transfer the image onto a computer's monitor.

A digital scanner (HP 3970) captured this image of a section of a yellow jacket nest. Click image to enlarge.

Times have changed, and today you can acquire a high-quality digital scanner for less than $100, some for much less. Many such scanners will have a resolution of perhaps 2400 x 2400 dpi. Some will also scan photographic negatives and slides.

Scanners have several important advantages over cameras. Here are four major categories:

1. Archival Images. Scanners are ideal for digitizing pages in old books, field notes, maps, sketches, electronic circuit diagrams, and laboratory notebooks. You can then archive such documents on your computer, send them to others and place them on the web.

2. Digitized Text. Scanner software drivers can transform printed text into ASCII characters you can save on your computer.

3. Flat-Field Photographic Images of Natural Objects. Scanners are ideal for capturing images of objects that have a flat or nearly flat surface. This includes leaves, polished mineral specimens, butterflies, dragonflies, feathers, soil, fingers and hands, fur, segments of trees that reveal growth rings and many other natural objects.

4. Flat-Field Photographic Images of Manufactured Objects. Scanners are perfect for making images of gears, washers, small electronic components, circuit boards, printed circuit diagrams, coins, wire, tools and so forth.

Shown nearby is a scanned image of a section of a nest built by paper wasps commonly known as yellow jackets (Vespula spp.). This nest was under the roof of the front porch of my office all summer. A camera could have provided a similar image, but the lighting would not have been nearly as good. The image would also have been distorted around the edges.

The scanner illuminates the object being scanned during the scanning process. So the lighting is very uniform and virtually shadow free. Notice that the scanned image even captures the interior of the capsules, each of which measure from 5 to 8 mm across. The capsules around the edge are not imaged straight on, because the top of the nest was curved. This gives the image more of a photographic effect.

Archiving is a very important applications for scanners. My fireproof file cabinet holds a huge stack of manually recorded log sheets of Sun and sky measurements dating back to 1989. Someday I hope to scan every page of this entire collection.

Scanning is also a good way to record important sections of old chart recordings. These are often rolled for storage, which makes them awkward to store and difficult to study.

You can many examples of high quality scanned images on the web. For example, some spectacular images of scanned Odonata, which are the dragonflies and their kin, are at www.ups.edu/biology/museum/WAODphotos.html.

What will you scan today?

Forrest M. Mims III
Editor