CCD VS CMOS in video surveillance cameras
There are two different types of cameras in the video surveillance cameras; CCD cameras and CMOS cameras. Now these two types cameras dominated the surveillance market. Thus, how much information we obtained about CCD (charge coupled device) camera and CMOS (complementary metal oxide semiconductor) camera? What are differences between them?
CCD are more sensitive to the light
Sensitivity is one of major difference between CCD camera and CMOS camera. With results of different material to form the image, CMOS sensor with 10 times lower sensitivity than CCD sensor. Human eye can see the objects under 1LUX light condition, CCD sensor see target more than human eye can do, under approximately 0.1 – 3Lux light condition, it’s 3-10 times than CMOS sensor. The sensitivity for CMOS sensor is about among 6-15LUX, CMOS with 10 times of high ratio of noise, compared to CCD sensor, CMOS sensor can not be used under 10LUX light condition lead to CCD sensor widely used for majority of video surveillance cameras. Typically, CMOS sensor is used for low-cost cheap home appliance products. The material for CCD sensor are expensive than material for CMOS sensor.
ACD also is important.
Then, what’s the reason caused CMOS without good sensitivity than CCD? Let’s take up this on next paragraph.
The first difference between CCD and CMOS is the difference of structure of pixel sensor unit. Except contain light photons semiconductor, CCD consists of many MOS (Metal Oxide Semiconductor) capacitors. CMOS sensor construct is more sophisticated, except the photons semiconductors, it included with amplifier and A/D circuit. Compared to CMOS sensor, CCD sensor with large sensitive fields, it can generate strong electric signal in the same environment condition; from the output of image, CCD sensor can provide low-noise and high-quality images. That’s the reason why traditional CMOS sensor is not as good as CCD sensor.
However, since the developing of technology, now there are impressive improvement for the CMOS sensor, with low-cost advantages, CMOS sensor start to challenge the dominate CCD sensor in high end market.
ADC (analog/digital converters) position and quantities are different
CCD and CMOS consist of different ADC design and quantities. Each line of pixel of CCD sensor connect with one ADC, after the exposure is complete, the charge is transferred into a read-out register, and from there to an output amplifier, ADC and on for processing; Each pixel for CMOS connect to one ADC, electrical signal went through amplifier and convert to digital signal.
CCD sensor output analog signal, CMOS sensor output digital signal.
CCD sensor and CMOS sensor with difference between signal processing, the previous adopts analog signal, with parameters of line, the CMOS adopts digital signal, with parameter of pixel. Surveillance cameras that use IP network for transmission are using CMOS sensor, the traditional surveillance camera are using CCD sensor.
After the development of last few years, design improvements for CMOS sensor have increased the light sensitive area to near the level of CCD sensors. In addition, CMOS sensor with advantages of simple structure, low-cost, low power consumption. CCD sensors can work better in night condition, but CMOS sensor can provide 100 million pixels HD high quality images, that’s the CCD sensor can not achieve.
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Tags: CCTV Cameras