What Is a CCD Camera?

CCD cameras are used in security systems. The current generation of images is mainly from CCD cameras. CCD is short for charge coupled device. It can turn light into electric charges and store and transfer the electric charges. The charge is taken out to change the voltage, so it is an ideal CCD camera element. The CCD camera is widely used because of its small size, light weight, no magnetic field, and anti-vibration and impact.

CCD camera

CCD cameras are used in security systems. The current generation of images is mainly from CCD cameras. CCD is short for charge coupled device. It can turn light into electric charges and store and transfer the electric charges. The charge is taken out to change the voltage, so it is an ideal CCD camera element. The CCD camera is widely used because of its small size, light weight, no magnetic field, and anti-vibration and impact.

Chinese name

CCD camera

Foreign name

charge coupled device camera

Types of

camera

Attributes

Charge-coupled device

CCD

CCD, full name in English: Charge coupled Device, full name in Chinese: charge-coupled element, can be called CCD image sensor. CCD is a semiconductor device that can convert optical images into digital signals. The tiny photosensitive material implanted on the CCD is called a pixel. The more pixels a CCD contains, the higher the resolution it provides. CCD works like film, but it converts image pixels into digital signals. There are many neatly arranged capacitors on the CCD, which can sense light and convert the image into a digital signal. Through the control of an external circuit, each small capacitor can transfer its charge to its adjacent capacitor. As a light number conversion element, CCD cameras have been widely used. ^[1]

CCDs with grid-like pixels are used in the light-sensitive components of digital cameras, optical scanners, and video cameras. Its light efficiency can reach 70% (capable of capturing 70% of incident light), which is 2% better than that of traditional films. Therefore, CCDs have been rapidly adopted by astronomers.

Difference between CCD camera and CMOS camera

Imaging process

The principle of photoelectric conversion of CCD and CMOS image sensors is the same. The main difference is that the signal readout process is different. Because CCD has only one (or a few) output nodes for unified readout, the consistency of its signal output is very good; In a CMOS chip, each pixel has its own signal amplifier, which performs charge-voltage conversion, and the consistency of its signal output is poor. However, in order to read out the entire image signal, the CCD requires a wider signal bandwidth of the output amplifier. In a CMOS chip, the bandwidth requirement of the amplifier in each pixel is lower, which greatly reduces the power consumption of the chip. This is the CMOS chip. The main reason for lower power consumption than CCD. Despite the reduced power consumption, the inconsistency of millions of amplifiers brings higher fixed noise, which is again an inherent disadvantage of CMOS over CCD.

Integration

From the perspective of the manufacturing process, the circuits and devices in the CCD are integrated on the semiconductor single crystal material, and the process is more complicated. Only a few manufacturers in the world can produce CCD wafers, such as DALSA, SONY, and Panasonic. The CCD can only output analog electrical signals, which requires subsequent address decoders, analog converters, and image signal processors, and it also needs to provide three sets of power supply synchronous clock control circuits with different voltages. The integration is very low. CMOS is integrated on a monolithic material called metal oxide. This process is the same as the process for producing tens of thousands of semiconductor integrated circuits such as computer chips and storage devices, so the cost of producing CMOS is much lower than that of CCD. . At the same time, the CMOS chip can integrate the image signal amplifier, signal reading circuit, A / D conversion circuit, image signal processor and controller into one chip, and only one chip can realize all the basic functions of the camera, the degree of integration Very high, the chip-level camera concept was born from this. With the continuous development of CMOS imaging technology, more and more companies can provide high-quality CMOS imaging chips, including: Micron, CMOSIS, Cypress, etc.

Speed

The CCD uses one-by-one photosensitive output, which can only be output according to the prescribed program, and the speed is slow. CMOS has multiple charge-voltage converters and row / column switch controls. The readout speed is much faster. Most high-speed cameras above 500fps are CMOS cameras. In addition, the address strobe of the CMOS can be sampled randomly to achieve sub-window output, which can achieve higher speed when only outputting sub-window images.

4. Noise

CCD technology has developed relatively early and is relatively mature. It uses PN junction or silicon dioxide (SiO2) isolation layer to isolate noise. The imaging quality has certain advantages over CMOS photoelectric sensors.