The outstanding feature of CCD is that charge is used as signal, unlike other devices that use current or voltage as signal. This type of imaging device forms charge packets through photoelectric conversion, and then transfers and amplifies the output image signal under the action of driving pulses. A typical CCD camera consists of an optical lens, timing and synchronization signal generators, vertical drivers, and analog/digital signal processing circuits. As a functional device, CCD has the advantages of no burns, no hysteresis, low voltage operation, and low power consumption compared with vacuum tubes.

The development of CMOS image sensors first appeared in the early 1970s. In the early 1990s, with the development of very large-scale integrated circuit (VLSI) manufacturing technology, CMOS image sensors developed rapidly. The CMOS image sensor integrates a photosensitive element array, image signal amplifier, signal reading circuit, analog-to-digital conversion circuit, image signal processor and controller on a chip, and also has the advantage of programming random access to local pixels. At present, CMOS image sensors have been widely used in high-resolution and high-speed applications due to their good integration, low power consumption, high-speed transmission and wide dynamic range.

CCD industrial cameras are mainly used in image extraction of moving objects, such as machine vision for placement machines. Of course, with the development of CMOS technology, many placement machines are also using CMOS industrial cameras. CCD industrial cameras are generally used in visual automatic inspection programs or industries. ? CMOS industrial cameras are more and more widely used because of their low cost and low power consumption.

The aperture of the lens mainly affects the brightness of the image surface, but in the current machine vision, the final image brightness is determined by many factors: aperture, camera gain, integration time, light source and so on. Therefore, in order to obtain a reasonable image brightness, it is necessary to comprehensively adjust the imaging parameters.