Before we get into any detail of the basic mechanism of the QR code scanner, we should know what QR code is. In practice, the QR code often contains data for a locator, identifier, or tracker that points to a website or application. A QR code uses four standardized encoding modes, numeric, alphanumeric, byte/binary, and kanji, to store data efficiently while using some extensions under certain conditions. It also consists of black squares arranged in a square grid on a white background, which can be read by an imaging device such as a camera, and processed using Reed-Solomon error correction until the image can be appropriately interpreted. Subsequently, the required data is can be extracted from patterns that are present in both horizontal and vertical components of the image. A QR code reader also referred to as a QR code scanner is an optical scanner that can read printed QR codes, decode the data contained in the QR code and send the data to a computer. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating for optical impulses into electrical signals. Additionally, nearly all QR code scanners contain decoder circuitry that can analyze the QR code’s image data provided by the sensor and send the QR code’s content to the scanner’s output port.
LED scanners apply an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor measures the intensity of the light in front of it immediately. Each individual light sensor in the CCD reader, a LED scanner, is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a QR code is generated in the reader by sequentially measuring the voltages across each sensor in the row. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the QR code whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself. Camera-based readers, two-dimensional imaging scanners, are a newer type of QR code scanner, which uses a camera and image processing techniques to decode the QR code. Similarly, video camera readers use small video cameras with the same technology as in a CCD QR code scanner except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two-dimensional array so that they can generate an image.
Large field-of-view readers use high-resolution industrial cameras in order to capture multiple QR codes simultaneously. All the QR codes appearing in the photo are decoded instantly or by use of plugins and have been realized options for resolving the given tasks, for example, the QR code media used a flash application and some webcam for querying a database.
In addition, omnidirectional QR code scanner uses “series of curved or straight scanning lines of varying directions in the form of a Lissajous curve, a starburst, or other multi-angle arrangements that are projected at the symbol and one or more of them will be able to cross all of the symbol’s bars and spaces regardless of the orientation. Almost all of them use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read QR codes presented to it at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns. Among them, omnidirectional QR code scanners are most familiar through the horizontal scanners in supermarkets, where packages are slid over a glass or sapphire window. There is a range of different omnidirectional units available which can be used for differing scanning applications, ranging from retail type applications with the QR codes read only a few centimeters away from the scanner to industrial conveyor scanning where the unit can be a couple of meters away or more from the code. Omnidirectional scanners are also better at reading poorly printed, wrinkled, or even torn QR codes.