2016 CMOS image sensor market may reach 10.8 billion

The eye is the source of human visual images, and the image sensor is the image capture device of the video capture device. There are generally two types of image sensors classified by morphology: linear image sensors and surface image sensors. Linear image sensors are used in scanners, copiers, and fax machines. The surface image sensors are widely used in security surveillance cameras, mobile phone cameras, car reversing video cameras, and tablet computers.

Image sensors are CCD and CMOS chips. In the early days, we generally believed that CCD sensors were used in devices with excellent image quality, while CMOS sensors were used in low-cost products. However, the new CMOS chip technology has overcome the technical weaknesses of earlier CMOS sensors, and the sensor design has improved low-light performance, exposure mode, and the like compared to the old products. Take the current popular back-illuminated CMOS sensor, in the traditional CMOS image sensor, the photodiode is located behind the circuit transistor, the light will pass through the circuit and the transistor between the microlens and the photodiode, then the amount of light will be blocked. affected.

The back-illuminated CMOS sensor is optimized in the internal structure of the image sensor's original component. It rotates the original of the photosensitive layer and directs light from the back side to increase the photosensitive capacity of the chip. This makes a back-illuminated CMOS image sensor better than conventional CMOS. The sensor has a qualitative leap in the sensitivity of light sensing. Under low illumination conditions, high-definition cameras using back-illuminated CMOS sensors have greatly improved performance in terms of focusing capabilities, image quality performance, and image noise control.

Back-illuminated CMOS image sensors have better high-sensitivity and noise control performance in addition to excellent low-light performance. That is to say, after ISO is raised, noise will be much less than CCD. This has a great advantage in image acquisition in low light environments, with better performance at high frame rates.

Back-illuminated CMOS sensors are often high-speed chips, and many chips support full-HD image output at a frame rate of 60 frames per second or more. In this regard, CCD sensors are more difficult. Most mainstream HD cameras using back-illuminated CMOS sensors now support 1080P@30fps Full HD video or 720P@60fps. And our common CCD sensor camera can only 720p @ 25fps, support for 1080P format CCD sensor costly. Back-illuminated CMOS sensor pixels can be higher.

Although both back-illuminated CMOS and CCD can increase effective pixels. However, when the structure of the back-illuminated CMOS determines that the sensor area does not change, the effective pixels can be further improved and the image quality can be maintained better. In contrast, if the CCD blindly raises the pixels, the picture quality will be very poor, and as the pixels increase, the chip size will also increase and the cost will increase geometrically.

The CCD sensor manufacturing process is more complicated, and the price of cameras using CCD sensors will be relatively high. In fact, after technological transformation, the gap between the actual effects of CCD and CMOS has been reduced a lot. Moreover, the manufacturing cost and power consumption of CMOS chips are much lower than those of CCDs, so many high-definition camera manufacturers use CMOS image sensors. Imaging: In the same pixel under the CCD imaging permeability, sharpness is very good, color reproduction, exposure can guarantee the basic accuracy.

The CMOS products currently have a general screen permeability and a weak color reproduction capability. The exposure mode has a problem that the high-speed moving object sensor has a distortion when it is captured due to the use of the Rolling Shutter mode. The CMOS image quality and the CCD sensor are in the image quality. There are still some distances from the more demanding scenarios. However, due to the low price and high degree of integration, it has been widely used in the rapidly developing high-definition camera market.

In-depth CMOS technology development In the field of video imaging, since the birth of the CMOS chip, I am afraid that the debate on CMOS and CCD has not stopped. Some people said that with the qualification of CMOS, it cannot shake CCD at all. Others say that CCD has grown for many years. Too many technologies have become established, which is not conducive to its update. In short, along with CCD and CMOS in the sensor market, this kind of debate about CMOS has been continuing.

Today, the monitoring of high-definition video on the Internet has gradually become a popular trend "killed." The widespread use of CMOS sensors in the field of network surveillance cameras has rekindled the interest of more people. Thus, the development of CMOS has once again been mentioned by people. If we say that the characteristics of analog surveillance cameras can further promote the advantages of CCD sensors, then will the arrival of high-definition network contribute to the capital of CMOS-capable CCD? Recently, with the seventh Global Digital Surveillance Development Forum held in Beijing, about The discussion of CMOS prospects once again put everyone on the desk.

1, originated from 3T-8T

In recent years, although the CMOS chip has always been in a quiet development trend. However, due to the coverage of the CCD sensor ring, it is difficult to get more attention. However, this also provides more accumulation processes for the development and take-off of CMOS.

From the birth of the earliest 3T CMOS chip, to the current 8TCMOS technology is gradually being trusted. The CMOS chip can silently go through a long period of development. At first, 3T's CMOS technology had a good performance in terms of simple reset, exposure of imaging effects, etc., and this is the embodiment of the CMOS chip's most elementary technology. Later, on the 4T chip that came out later, the relevant equipment has mainly achieved a very wide improvement in signal sampling. In the work, the CMOS sensor will sample the same scene in two different light and dark phases for the exposure sampling time. After that, the two effects will be well integrated to maximize the definition and low illumination capability. The promotion. Also better to achieve the improvement of smear CMOS chip.

2. After leaps and bounds, in order to better realize the image processing capability, a more revolutionary improvement has been adopted from the CMOS 5T chip. In the CMOS technology application, globalshutter technology has been applied, and a higher PLS has been applied, so that CMOS is simple. In the field of simple imaging such as security, mobile phones, and electrical energy, it has achieved the direction of high demand for medical applications, machine vision, etc.

After the implementation of 6T technology, CMOS will further enhance the application of globalshutter and achieve higher parasitic light sensitivity technology. The overall high-definition imaging capability of CMOS chips has also been upgraded to a higher level. Later, on the basis of 6T technology, CMOS chips added control gate technology and realized faster video switching, which can make it achieve higher imaging speed than before. This is what we call 7T technology. It can be said that, in terms of professionalism, 7T CMOS chips have reached a very high level.

3, 8TCMOS status leap Now, with the emergence of 8TCMOS chip, it can be said that CMOS has come out of a set of technical development path with its own characteristics. In terms of performance, CMOS is no longer a vassal of CCD technology. In low illumination, high-sensitivity technical support has made noise and illumination at night almost no different from CCD. In global shutter applications, globalshutter not only completely solves the smear problem when taking pictures, but also makes high-speed imaging under CMOS possible. Since the advent of 7TCMOS, CMOS sensors have been able to achieve frame rates above 300fps and beyond. The advantages it brings can be achieved by using high frame rates to complete the wide dynamic function of multi-frames and multi-stacks, which is undoubtedly of great help to high-speed capture and monitoring.