An cctv image sensor plays a key role in converting lights through the lens into electrical signals. Based on the cctv cameras manufacturing process, there are two types of sensors: CMOS (Complementary Metal Oxide Semiconductor) and
CCD (Charge-coupled Device).
CCTV Image Sensor Types :
CMOS is a standardized and constantly developing manufacturing process used in the semiconductors industry.
Each pixel on a CMOS sensor is accompanied by an amplifier based on p-n junction structure. The p-n junction structure receives photons from the sensor and transmits them to an image signal processor.
CCD is a manufacturing process specially developed for digital imaging. A CCD is an analog shift register that enables the transportation of analog signals (electric charges) through successive stages (capacitors), controlled
by a clock signal. The analog signals in each row of the capacitors are transmitted and converted to digital via an analog-to-digital IC.
Although CCDs are sensitive to visible light, they are also sensitive to NIR light. A sensor’s spectral response is a function of the chemistry of some components and can be further manipulated with filtering technologies. Filters designed to reduce or eliminate IR light, known as “infrared-cut filters,” can be used in front of the sensors to improve a color camera’s image . Monochrome cameras do not have such filters because they are intended for use near the IR spectrum. During the day, monochrome cameras form an image using both visible and NIR light; therefore, the daytime image may lack some clarity compared to nighttime images.
In order to increase the resolution, some cameras use three CCDs. In this configuration, a prism splits the white light passing through the lens into red, green, and blue. Then, three monochrome CCDs, each filtered to receive one color, calculate and combine the vector output to create a high-resolution image. The same principles can be applied to cameras utilizing three CMOS sensors.