How Printing Challenges Shaped the Modern Barcode

While students at Drexel University, Woodland and Bernard Silver overheard a grocery-industry executive ask one of the university’s school of engineering deans about options for gathering inventory data during the checkout process. Woodland, who had worked on the Manhattan Project and who had previously earned a degree in mechanical engineering, was so captured by the idea that he left graduate school to pursue it full time.

Woodland’s familiarity with Morse Code led him to experiment with patterns of dots and dashes, but in a 1999 interview with Smithsonian magazine, he attributed the essential characteristic of what would become the modern linear barcode to a day spent at the beach. “I poked my four fingers into the sand and for whatever reason – I don’t know – I pulled my hand toward me and drew four lines. I said, ‘Golly! Now I have four lines, and they could be wide lines and narrow lines instead of dots and dashes.’ Only seconds later, I took my four fingers – they were still in the sand – and I swept them around into a full circle.”

Incorporating this later flourish, Woodland and Silver filed in 1949 for patent of a bullseye-shaped code design and received a patent in 1952 for a device titled a “Classifying Apparatus and Method.” According to Woodland, one of the primary benefits of the bullseye pattern was that it was omni-directional, relieving checkout clerks of having to orient them to the detector. Their prototype detector-reader consisted of a 500-watt light bulb and oscilloscope – it would be decades before laser-based scanners became mainstream technology.

The bullseye pattern presented a unique printing challenge due to the tendency of inks to “bleed” during the printing process, causing blurring of the concentric bars. Unlike Woodland’s and Silver’s bullseye pattern, horizontal lines could be printed so that the inks bled in the direction of the bars, leaving sharp, readable bar edges. Woodland was working in IBM’s Store System Group in the late 1960s when it produced what would become the familiar rectangular-shaped linear UPC.

Of course, printing technology has also come a long way since Woodland and Silver first encountered the challenges of print bleed: Witness the thermal-transfer technology that allows Zebra Technologies to deliver ultra-precision, high-contrast linear and 2D barcodes from mobile printers that are so compact they can be worn on the operators belt. But, if you ever wondered who invented the linear barcode and why it consists of parallel bars, now you know!