October 12, 1999 Scanning
Tuesday October 12 11:42:15 CDT 1999

This mini-edition comes to you straight from my SGI workstation at the office!

I've got a few slack moments while I'm scanning. I just thought I'd take a moment to say that, although it probably seems old hat to most folks, I think it's pretty cool to be using a Howtek drum scanner to digitize an image at 2000 pixels per inch by 2000 pixels per inch, producing a 179 Mbyte file from an image about 6 x 7 inches.

The scanner is pretty neat. It's called a drum scanner because the image to be scanned is taped around the outside of a glass cylinder, or "drum". This drum is then put into the scanner, sort of like putting a wooden blank into an lathe, and the plastic, translucent safety cover is closed so that there is no chance of anything getting in or out- this thing is spinning fast. when the software is started, there is kind of a clunk from inside the scanner as the drum's drive is engaged, and when the "scan" button is clicked, a cool industrial whine is heard as the drum gets up to speed. As soon as the drum is spinning fast enough, the scanner begins shooting precisely timed pulses of bright light through the image to the sensor that is on a post passed through the hole in the bottom of the drum. Each time the light pulses, the sensor reads the intensity and color of the light filtered through the image. When one line around the circumfrnce of the drum has been scanned, the drum moves along its axis to put a new line in front of the light source. This isn't a quick process, though. I think it took about 25 minutes to scan an image less than the size of one regular printed page.

I am scanning the Jeppesen chart (kind of like a plan view of the runways and taxiways- we use them a lot for making airport databases) of London-Luton airport. Luton is one of a number of european airports that have to be updated in a hurry to provide current databases for the first of our simulators to be based in England.

Scan's done... back to work

About the Author
About this Website