“The image is unclear, the picture is not clear, there is noise, the picture is not high-definition, the distortion, the device consumes too much power.†These problems are all on the image sensor of the surveillance camera. In this issue, we will explain the image sensing technology in detail.
Currently, image sensors for surveillance cameras are gradually shifting from traditional CCDs to CMOS.
We all know that the important step in the video surveillance system is the front-end acquisition. The surveillance camera plays an important role in the entire video surveillance system as an important device for data acquisition. Image sensors are an important factor in determining the quality of surveillance cameras.
The core part of the video surveillance system is image sensing technology. At present, the image sensor of the surveillance camera is gradually changing from the traditional CCD to the CMOS. These two sensors have their own lengths, but the shortcomings of CMOS sensors have been decreasing. The low cost and high integration of CMOS image sensors are the main features, and the image quality is not lost to CCD. Compared to CCD-based probes, CMOS probes are more integrated because CMOS sensors integrate many peripheral processing functions, require fewer devices than CCD probes, and consume much less power from CMOS probes. From the perspective of the entire system, CMOS sensors can greatly reduce the cost.
Comparison of CMOS sensor and CCD sensor
CCD (ChargeCoupledDevice), a "charge coupled device", in megapixels. How many megapixels in a digital camera specification refers to the resolution of the CCD. The CCD is a light-sensitive semiconductor chip used to capture graphics and is widely used in scanners, copiers, and filmless cameras. Similar to the principle of film, light passes through a lens and projects graphic information onto the CCD. But unlike film, CCD has neither the ability to record graphical data nor the ability to be permanently stored, or even "exposure" capabilities. All graphics data is sent to an "analog-to-digital" converter, a signal processor and a storage device (such as a memory chip or memory card). CCDs come in a variety of sizes and shapes, up to 2&TImes; 2 square inches. In 1970, Bell Labs invented the CCD. Twenty years later, people used this technology to make digital cameras, pushing the image processing industry to a whole new field.
CMOS (Complementary Metal Oxide Semiconductor), that is, "complementary metal oxide semiconductor". It is an important chip in a computer system, which preserves a large amount of data needed for system booting. It has been found that CMOS processing can also be used as a sensitized sensor in digital cameras, which is convenient for mass production and low-cost features that merchants dream of.
From a technical point of view, CCD and CMOS have the following four differences:
1. Information reading mode : The charge information stored by the CCD charge coupler needs to be read one bit after the synchronization signal control. The charge information transfer and read output need to have a clock control circuit and three different sets. The power supply is matched, and the whole circuit is complicated. The CMOS photoelectric sensor directly generates a current (or voltage) signal after photoelectric conversion, and the signal reading is very simple.
2. Speed: The CCD charge coupler needs to output information one by one in the action unit under the control of the synchronous clock, and the speed is slow; while the CMOS photoelectric sensor can take out the electric signal while collecting the optical signal, and can simultaneously process The image information of each unit is much faster than the CCD charge coupler.
3. Power supply and power consumption: Most of the CCD charge couplers need three sets of power supply, which consumes a lot of power. The CMOS photoelectric sensor only needs one power supply, and the power consumption is very small, only 1/8 of the CCD charge coupler. By 1/10, CMOS photoelectric sensors have great advantages in terms of energy saving.
4. Image quality: CCD charge coupler fabrication technology started early, the technology is mature, and the noise is isolated by PN junction or silicon dioxide (SiO2) isolation layer. The imaging quality has certain advantages over CMOS photoelectric sensors. Due to the high integration of CMOS photoelectric sensors, the distance between each photoelectric sensing element and circuit is very close, and the optical, electrical and magnetic interference between them is serious. The noise has a great influence on the image quality, making the CMOS photoelectric sensor for a long time. Unable to enter practical. In recent years, with the continuous development of CMOS circuit noise reduction technology, it has provided good conditions for the production of high-density and high-quality CMOS image sensors.
Commercial applications of CMOS sensors and CCD sensors
At present, CCD technology is mainly in the hands of Sony, Canon, Olympus and other major manufacturers. The mainstream digital cameras use CCD as the photosensitive sensor, and the number of pixels is generally about 3 million. The manufacturing process is complicated, the power consumption is large, and the cost is high. In the future, digital cameras using CCD sensors will continue to improve the number of pixels, increase the shooting function, and improve the quality of photos, and strive to reach the standards of traditional cameras as soon as possible on various indicators.
Digital cameras using CMOS sensors are generally less than 1.3 million pixels, mainly for low-end markets dominated by home and personal users. Its advantages of fashion, versatility and low price have been welcomed by ordinary consumers. Domestic digital camera manufacturers have placed great enthusiasm for CMOS digital cameras, including Seagull, SAST, and Himalayan. CMOS plasticity is high, and in addition to digital cameras, it will be widely used in fax machines, scanners, digital cameras, and security detection systems. At present, there are not many CMOS products on the market, but in the United States, many companies including Intel and ATI are actively developing related products. In July of this year, IMEC, an independent semiconductor research organization in Europe, announced two research projects on CMOS, including "AdvancedDeviceImplementaTIonProgram", which explores the limits of CMOS technology. Its goal is to establish the latest version of the International Semiconductor Technology Plan (ITRS) and propose to face 60nm. ~30nm technology.
Comparison of TI, Hisilicon, Ambarella schemes
For a single million HD front-end camera, TI, Hisilicon, and Ambarella have their own advantages and disadvantages. No one is dominant in all dimensions.
TI's previous monitoring chip occupancy rate No.1, the technical background is rich, but I feel that TI has not invested much in the security market in the past few years. The products of the past two years have no outstanding highlights, the power consumption is more prominent, and the image quality is average. It takes a lot of skill to develop good results and powerful features. Can reflect the level of developers, the previous development is difficult, but in the past two years, the technical support has improved. There are many secondary development plans, which are beneficial to R&D companies with certain technical strength.
After occupying the DVR market, Haisi has paid more attention to the IPC market in the past two years, and the frequency of products launched in the IPC field is relatively high. The performance is excellent. After integrating your own ISP, the image quality is also good, and as a domestic solution manufacturer, technical support is in place. Development is relatively easy and the price is relatively cheap. At present, it is widely accepted by the market for its high cost performance and good technical support.
As a traditional DV solution provider, Anba is committed to the needs of high-end customers. It is the ultimate in video image compression, code stream and image quality. It is the well-deserved leader in video image processing. And the manufacturers of the Anba system put forward the same code stream to see the effect, the same effect is better than the concept of code stream. The biggest advantage is the image quality, especially the coding algorithm is very good. In the case of low code rate, the image quality is the best among the three schemes, the price is expensive, and the market share is not high.
TI, Hisilicon, Anba company profile
TI (TexasInstruments): short for Texas Instruments, headquartered in Dallas, Texas, USA, is a world-renowned semiconductor company, mainly engaged in the research of analog circuits and digital signal processing technology, its representative DaVinci-DM3xARM9 Video processor solutions are used in a wide range of applications in the security industry.
In 1951, it changed its name to Texas Instruments and began to enter the semiconductor market. It has occupied a large share in many market sectors. When video surveillance in the security field evolved from the simulation phase to the digital compression processing phase, TI gradually dominated the security video compression field. Representative solutions in the IPC field are the DM355, DM365, DM368, and the newly introduced DM369, DM388.
Hisilicon: Hisilicon Semiconductor Co., Ltd. was established in October 2004. Its predecessor was Huawei Integrated Circuit Design Center, which was founded in 1991. Headquartered in Shenzhen, HiSilicon has design divisions in Beijing, Shanghai, Silicon Valley and Sweden. Haisi's products cover chips and solutions in wireless networks, fixed networks, digital media, etc., and have been successfully applied in more than 100 countries and regions around the world. In the field of digital media, network monitoring chips and solutions, videophone chips have been launched. And solutions, DVB chips and solutions and IPTV chips and solutions. In 2009-2012, DVR chips can be described as wind and water. Representative solutions in the IPC field are Hi3516, Hi3516C, Hi3517, Hi3518A, Hi3518C, Hi3518E.
Ambarella: Founded in 2004 and headquartered in Santa Clara, Calif.; the company's Chinese name is “Anbaâ€, which is the technology leader in the HD video industry, providing low-power, high-definition video compression and Image processing solutions, in the TV broadcasting market, Anba technology is also widely used, TV programs from all over the world are compressed by the Anba chip and transmitted. The industry is the first to introduce a highly integrated SoC chip based on the latest H.264 video compression standard, integrating various key system functions, providing a cost-effective HD overall solution, and nearly 90% of the H.264 HD professional broadcast encoding equipment market. Market. Representative solutions in the IPC field are A2, A5, A5S, A7, A9.
Conclusion:
Most of the chips in the field of video surveillance are in the hands of foreign companies. The harmful effects caused by the lagging of domestic chip research and development have attracted the attention of the state. As a result, the government has adopted a stimulus policy for the chip industry, and plans to invest 10 trillion yuan in 10 years to support the localization of chips. And this policy will benefit from Shenzhen, Shanghai, Wuhan and other places. Image sensor technology, as the core of the video surveillance system, will have a major improvement in its localization.
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