His idea is to put a barcode on the envelope, and the information in the barcode is the address of the recipient, just like today's postal code. For this reason, Kermode invented the earliest bar code recognition, and the design scheme is very simple (note: this method is called modular comparison method), that is, one bar represents the number "1", two bars represent the number "2", and so on. Then, he invented a bar code reading device composed of basic components: scanner (which can emit light and receive reflected light); A method for measuring the band and space of reflected signal, namely edge positioning coil; And a method of using the measurement result, namely a decoder.
Kermode's scanner uses a newly invented photocell to collect reflected light. "Empty" reflects a strong signal, while "bar" reflects a weak signal. Unlike today's high-speed applications of electronic components, Kermode uses magnetic coils to measure "bars" and "spaces". Just like a child connecting a wire to a battery and winding it around a nail to clamp paper. Kermode uses a coil with an iron core to attract a switch when receiving the "empty" signal, and release the switch when receiving the "bar" signal to connect the circuit. So the earliest bar code readers were very noisy. The switch is controlled by a series of relays, and the "on" and "off" are determined by the number of "paper strips" printed on the envelope. In this way, the bar code symbol directly sorts the letters.
Shortly thereafter, Douglas Young, a collaborator of Kermode, made some improvements on the basis of Kermode code.
Kermode code contains very little information, so it is difficult to compile more than ten different codes. Young codes use fewer bars, but the size of the space between bars changes, just as UPC barcode symbols today use four different bar sizes. The new bar code symbol can encode one hundred different regions in the same size space, while Kermode code can only encode ten different regions.
It was not until 1949 that the omni-directional bar code symbols invented by Noam Woodland and Bernard Silver were recorded for the first time. Prior to this, there was no record of bar code technology in patent literature, and there was no precedent for practical application. Noam Woodland and Bemmad Silver's idea is to use Kermode and Yang's vertical "strips" and "spaces" to bend them into a ring, much like the target of archery. In this way, the scanner can decode the bar code symbol by scanning the center of the graph, regardless of the direction of the bar code symbol.
In the process of constantly improving this patented technology, the science fiction writer Isaac-Azimov described an example of automatic identification using a new information coding method in his book Naked Sun. At that time, people thought that the barcode symbol in this book looked like Fang Gezi's chessboard, but today's barcode professionals will immediately realize that it is a two-dimensional matrix barcode symbol. Although this bar code symbol has no direction, no positioning and no timing, it is obvious that it represents a digital code with high information density.
It was not until 1970 that ITER FACE MACHINES developed "two-dimensional code", and the printing and reading equipment of two-dimensional matrix bar code came out at a price suitable for sale. At that time, two-dimensional matrix bar code was used to realize the automation of newspaper typesetting process. Two-dimensional matrix bar code is printed on paper tape and scanned and read by today's one-dimensional CCD scanner. The light emitted by CCD shines on the paper tape, and each photocell is aimed at different areas of the paper tape. Each photovoltaic cell outputs different patterns according to whether the bar code is printed on paper tape or not, and combines them to generate high-density information patterns. In this way, a single character can be printed in the same size space as a single bar in the early Kermode code. Timing information is also included, so the whole process is reasonable. When the first system entered the market, the price of the whole set of equipment including printing and reading equipment was about $5,000.
Shortly thereafter, with the continuous development of LED (light emitting diode), microprocessor and laser diode, a new symbol (symbolism) and its explosion came, which was called "barcode industry". Today, it is difficult to find companies or individuals who have not been directly exposed to fast and accurate barcode technology. With the rapid technological progress and development in this field, more and more application fields are developed every day. Before long, bar codes will be as popular as light bulbs and transistor radios, which will make everyone's life easier and more convenient.
Bar code is a set of bars and empty symbols arranged according to certain coding rules, which is used to represent information composed of certain characters, numbers and symbols. Bar code system is an automatic identification system composed of bar code symbol design, production and scanning reading.