The difference between CCD and CMOS in industrial cameras

The difference between CCD and CMOS in industrial cameras

CCD and CMOS are essentially the difference in sensor technology. In simple terms, a CCD's light-sensing element uses only one "amplifier" for each row of pixels, while a CMOS has a separate amplifier for each pixel. Therefore, on a CCD, from a pixel point of view, the area for light-sensing is much larger than on a CMOS. After all, CMOS integrates a lot of complex circuits, so the image quality of CCD is indeed better than that of CMOS. However, CCDs have two inherent drawbacks. One is slow. After all, the processor needs to process information about each pixel. Noise is usually high.

The main difference between CCD and CMOS in manufacturing is that CCD is integrated on a semiconductor single crystal material, while CMOS is integrated on a semiconductor material called metal oxide, and there is no essential difference in the working principle. In fact, after technological transformation, the gap between the actual effect of CCD and CMOS has been reduced a lot. Moreover, the manufacturing cost and power consumption of CMOS are much lower than that of CCD, so many camera manufacturers use CMOS photosensitive elements.

Imaging: Under the same pixel, the imaging transparency and sharpness of the CCD are very good, and the color reproduction and exposure are basically accurate. However, CMOS products tend to have average transparency, weak color reproduction ability to real objects, and poor exposure. Due to its own physical characteristics, the image quality of CMOS still has a certain gap with that of CCD. But it is still widely used in the camera field due to price difference and high integration.

There are many indicators to measure the quality of CCD, such as the number of pixels, CCD size, sensitivity, signal-to-noise ratio, etc. Among them, the number of pixels and the size of CCD are important indicators. The number of pixels refers to the number of photosensitive elements on the CCD. The picture taken by the camera can be understood as being composed of many small dots, each dot is a pixel. Obviously, the higher the number of pixels, the sharper the picture. If the CCD does not have enough pixels, the sharpness of the picture will be greatly affected.

CMOS sensors are far superior in terms of processing speed and power efficiency. CCD sensors have a finite number of nodes to convert each pixel charge on the sensor. This results in slower processing. However, since all the pixels are available for light capture on the CCD structure, the overall output is sharper and brighter.

For machine vision, important KPIs are processing speed and image noise. CMOS sensors allow digital conversion of each pixel, resulting in lower bandwidth. Alternatively, high-speed CCD sensors are not as massively parallel as high-speed CMOS imagers. As a result, each CCD amplifier has a higher bandwidth, resulting in more noise on the resulting image. This is why most industrial applications use the latest CMOS sensors, which can be designed to produce images with much less noise.