According to the statistics of Xuan Zhan technology, SONY auto focus camera from the earlier series has been used CMOS sensor, then, the use of CMOS sensor camera compared to CCD sensor camera what are the advantages? What are the differences and connections between them? Will CMOS sensors completely replace CCD sensors? Here’s one for you.
CCD sensors versus CMOS sensors
First, the connection between CCD and CMOS
There has been much discussion about the relative advantages of CMOS over CCD. The debate went on for a long time, but there was no clear conclusion. This is not surprising since the problem is not set in stone.
Technology and markets evolve, affecting not only what is technically feasible but also what is commercially viable. The applications of imaging devices are diverse, and the requirements and technologies are constantly changing.
First, both CCD and CMOS imaging rely on the photoelectric effect to generate electrical signals from light. Both types of imaging components work by converting light into charge and processing it into electronic signals.
In a CCD sensor, the charge of each pixel is transmitted through a very limited number of output nodes (usually only one), then converted to voltage, buffered and sent off-chip as an analog signal. All pixels are available for light capture, and the uniformity of the output, a key factor in image quality, is high.
In CMOS sensors, each pixel has its own charge-to-voltage conversion, and the sensor usually includes an amplifier, noise correction, and digitization circuit so that the chip outputs a digital signal. These other features increase the design complexity (compared to a CCD) and reduce the area available to capture light. As each pixel is transformed, the uniformity decreases.
Two, the difference between CCD and CMOS sensor
1. Imaging process
CCD and CMOS image sensor photoelectric conversion principle is the same, their main difference lies in the signal readout process is different; Because CCD has only one (or a few) output nodes unified readout, its signal output consistency is very good; However, in CMOS chip, each pixel has its own signal amplifier, which carries out charge-voltage conversion respectively, so the consistency of its signal output is poor. However, in order to read out the whole image signal, CCD requires the signal bandwidth of the output amplifier to be wide, while in CMOS chip, the bandwidth of the amplifier in each pixel is low, which greatly reduces the power consumption of the chip. This is the main reason why the power consumption of CMOS chip is lower than that of CCD. CMOS consumes only 1/8 to 1/10 of the power of CCD.
Since CMOS sensors adopt the most commonly used CMOS process of general semiconductor circuits, peripheral circuits (such as AGC, CDS, Timing generator or DSP, etc.) can be easily integrated into the sensor chip, so the cost of peripheral chips can be saved. CCD uses charge transfer to transmit data, as long as one pixel cannot run, it will lead to a whole row of data cannot be transmitted, so it is much more difficult to control the yield rate of CCD sensor than CMOS sensor, even experienced manufacturers are difficult to break through the 50% level within half a year of product release, therefore, CCD sensors will be more expensive to manufacture than CMOS sensors.
From the perspective of manufacturing process, the circuits and devices in CCD are integrated on the semiconductor single crystal material, and the process is complex. Only a few manufacturers in the world can produce CCD chips, such as DALSA, SONY, Panasonic and so on. CCD can only output analog electrical signals, which need subsequent address decoder, analog converter, image signal processor processing, and also need to provide three groups of different voltage power synchronization clock control circuits, integration is very low. CMOS, on the other hand, is built on individual pieces of material called metal oxides, the same process used to make tens of thousands of semiconductor integrated circuits such as computer chips and memory devices, making it much cheaper to produce than CCDS. At the same time, CMOS chip can image signal amplifier, signal reading circuit, A/D conversion circuit, image signal processor and controller integrated into a chip, only a chip can realize all the basic functions of the camera, high integration, chip level camera concept is generated from this. With the continuous development of CMOS imaging technology, more and more companies can provide high-quality CMOS imaging chips.
CCD adopts one by one photosensitive output, can only be output according to the prescribed program, the speed is slow. CMOS has multiple charge-voltage converters and row switch control, readout speed is much faster, most of the 500fps above the high-speed camera is CMOS camera. In addition, CMOS address gating switch can be randomly sampled to achieve sub-window output, and higher speed can be obtained when only sub-window image is output.
For CMOS sensors, it is based on the consideration of reducing power consumption, increasing integration and reducing manufacturing costs by reusing mainstream logic and memory devices. CMOS meets the above expectations in actual production, thus becoming a mature mainstream technology.
In the case of coexistence of the two, CCD sensor is superior to CMOS sensor in sensitivity, resolution, noise control and other aspects, while CMOS sensor has the characteristics of low cost, low power consumption, and high integration. By comparing different situations, we can understand the technical tradeoffs and some cost considerations, which can be selected according to our own actual needs.
FCB-EV9520L, as a new generation of SONY autofocus camera movement, will be available for sale in the first half of 2023. It is revealed that FCB-EV9520L uses STARVIS 2 CMOS sensor. What breakthroughs will it make in technology and performance in the future? We’ll see.