Bar Codes: A Linear History
In 1948, graduate students, Norman Woodland and Bernard Silver, took on a problem that had troubled retailers for years: how to keep track of store inventories. Inspired by the dots and dashes of Morse code, however, Woodland and Silver created a system of lines that could encode data. Called a symbology, the pattern created by the spacing and widths of the lines encodes information by representing different characters.
The first bar code was composed of four white lines set at specific distances from each other on a black background. The first line was always present.(4) Depending on the presence or absence of the remaining three lines, up to seven different arrangements were susceptible and, therefore, seven different encodings. Today, twenty-nine white lines making more than half a billion encodings possible.
To create a bar code scanner, Woodland and Silver adapted technology from an optical movie sound system. Their prototype scanner used a 500-watt bulb, a photomultiplier tube (a device that detects light), and an oscilloscope (a device that translates electronic signals into readable information). Although successful, the concoction was both large and costly. For example, progress stalled until the 1970s, when laser technology (both more compact and less expensive) became available.
In today’s scanners, a laser sends light back and forth across a bar code. While the black lines absorb the light, the white lines reflect it back at a fixed mirror inside the scanner. In this way, the scanner reads the symbology and decodes the information.
(10) Today, being that there are one- and two-dimensional bar codes using numeric and alphanumeric symbologies. Bar codes are used not only for a pack of gum or an airline ticket, but also for research. In one study, for instance, tiny bar codes were placed on bees tracking their activities. Shaping the way we gather, track, and share information, we have almost certainly exceeded even Woodland and Silver’s expectations.