From a historical perspective, CCD (Charge Coupled Element) sensors are "born" 40 years earlier than CMOS sensors. Due to continuous improvement and optimization, CCD imaging has almost become the benchmark for high-quality images for many years; Appeared in the commercial market, and its success is also the affirmation of the 10-year technical success.
Speaking of surveillance cameras, more people are concerned about image clarity. Natural image sensors have become the core of the discussion. It is out of the logical thinking of most people. The author briefly describes the history of CCD and CMOS at the beginning of the article. For a moment. But define the camera performance only look at the sensor? CCD / CMOS sets the stage in one step, and it may be too absolute.
Get the sensor in one step? Defining the performance of surveillance cameras Who is more sensitive to CCD and CMOS?
Since sensors are the highlight, let's talk about them first. I do not know where to start, the contest between CCD and CMOS has become a hot spot in the field of video surveillance or security. No matter how much the two differ in details, the sensor is always paying for HD video based on the same physical principle. The quality of the sensor determines the success or failure of the image quality, especially in terms of sensitivity and sensitivity to light, the two are comparable.
When I first entered the security industry, many surveillance cameras used CCD sensors, and CMOS cameras with lower prices also occupied part of the market. In order to improve the imaging level of the camera, 2 or 3 sensors can be used. But multiple sensors will naturally cause many drawbacks. If you compare a single sensor, what is the difference between the two?
Surveillance lens interface also affects camera performance?
The maximum sensitivity of the CMOS sensor is in the red spectral region (650-700 nm), and there are not many innovative applications of CCD technology, but its killer is the most sensitive area of ​​the human eye-550 nm. For various technical reasons, CMOS is regarded as a low-efficiency photoelectric signal conversion device; because the photosensitive area only occupies a small part of the pixel area, it becomes its biggest weakness. With the improvement of technology in recent years, the size of the CMOS light sensitive area has been close to the level of the CCD sensor, allowing the CMOS sensor to turn over.
Since there is no obvious difference between light transmittance and sensitivity, where is the dispute between CCD and CMOS? Perhaps because of the fear of "the latecomers come first", the CCD had to beware of the surpassing of CMOS. In particular, the ultra-wide dynamics of cameras based on CMOS chips and digital pixel system image processing technology has exceeded the level of CCD chip cameras.
Pixel value and horizontal resolution In addition to the core sensor, in fact, the sensor and pixel value and horizontal resolution also have an indissoluble bond. Let's talk about pixel values ​​first. The more pixels, the higher the resolution and the clearer the image. According to the current mainstream pixel values, most analog monitoring equipment outputs are D1 series, the effective pixels are 720 * 576, the high-definition image resolution is mostly 720P or 1080P, and the pixel value can also reach one million levels.
The pixel resolution is very close to the horizontal resolution, which is also the number of XX lines we often see during the test. The unit is expressed by the TV line TVL. Horizontal resolution is a standard to measure image clarity. Both pixel values ​​and horizontal resolution can represent the clarity of the picture. In the broadcast industry, the vertical resolution of video exceeds 720p or 1080i to be called HD.
The horizontal resolution test of the surveillance camera determines whether the picture quality of a surveillance camera is clear, and the pixel value and horizontal resolution can explain the problem better. The sensor is the key to left and right imaging, but from the user's perspective, the visual effect is determined by the most intuitive image pixels and resolution.
Of course, there are many indicators to measure the performance of surveillance cameras, but for surveillance cameras with different functions, we have to choose different types and references. Low illumination, signal-to-noise ratio, wide dynamics, etc. may have such requirements for network surveillance cameras.
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