Commonly used commercial barcode scanner are: 1. Light pen is the first hand-held contact bar code reader and the most economical bar code reader. When in use, the operator needs to touch the light pen to the bar code surface and emit a small light spot through the lens of the light pen. When the light spot passes through the bar code from left to right, the light is reflected in the "empty" part and absorbed in the "bar" part, so a variable voltage is generated inside the light pen, which is used for decoding after amplification and shaping. 2.CCD scanner: using the principle of photoelectric coupling (CCD), the bar code printed pattern is imaged and then decoded. Its advantages are: no rotating shaft, no motor and long service life; The price is cheap. When choosing a CCD scanner, the two most important parameters are depth of field and resolution. 3. Laser handheld scanner: Single-line scanner with laser diode as light source, mainly including rotating mirror and vibrating mirror. The representative brand of rotating mirror is SP400, which uses high-speed motor to drive the prism group to rotate, so that the single-point laser emitted by diode becomes a line. The manufacturing cost of vibrating mirror is lower than that of rotating mirror, but the scanning speed of laser gun based on this principle is not easy to increase, generally 33 times per second. Individual models such as POTICON can reach 100 times per second, and the representative brands are Symbol, PSC and POTICON. When commercial enterprises choose laser scanners, the most important thing is to pay attention to the scanning speed and resolution, and the depth of field is not the key factor. Because when the depth of field increases, the resolution will be greatly reduced. An excellent hand-held laser scanner should have high scanning speed and high resolution within a fixed depth of field. 4. All-angle laser scanner: the optical system refracts the laser diode of multiple scanning lines or the laser emitted by bar code scanner. The main purpose is to reduce the cashier's labor of aligning bar codes when inputting bar code data. -Shanghai barcode technology