The electronic rearview mirror Camera Monitor System, abbreviated as CMS, is a product combination based on cameras and displays, which can enhance the driver's visual perception around the vehicle and behind the side, and further enhance driving safety and comfort. Among them, the images collected by the external camera are displayed on the display screen in the cabin after data processing. At the same time, functions such as blind zone warning and obstacle prompt can be integrated.
CMS cognition
The electronic rear-view mirror is essentially a system consisting of a professional SLR camera and an on-board monitor that conforms to the GB15084 standard and meets the vehicle safety level D. The cognition of electronic rear-view mirror is generally divided into four levels:
Figure: Source: Shanghai Yuxing Electronics
The first level is traditional image , that is, we are familiar with traditional image products, such as rear view, central control screen, recorder, streaming media rearview mirror, etc.
The second level is the substitution relationship CMS is an alternative to traditional optical rear-view mirror, which must meet GB15084. Electronic rear-view mirror is a cross industry product combining traditional optics and electronics. It needs interdisciplinary talents, especially in optical imaging, image color and image processing. This is why traditional optical rear-view mirror enterprises and electronic enterprises in the world jointly develop CMS.
The third level is temporary adjustment of field of view (scene following) CMS image display is mainly combined with vehicle attitude and driving environment to meet the requirements of laws and regulations on physical mirror vision, as well as temporary vision expansion. Scene following is the soul of CMS, The electronic rear-view mirror replaces the traditional rear-view mirror at ten times the price. It must provide users with value-added functions beyond the traditional rear-view mirror, and can provide temporary adjustment of vision in the starting, driving, turning, and parking scenarios.
The fourth level is safe and reliable The traditional optical mirror is a vehicle safety part, and safety and reliability are also the basis of CMS products. Security is based on the bottom three layers. It does not exist in isolation. Only by consolidating the bottom three layers can we understand and respect security.
CMS Advantages and Applications
The electronic rear-view mirror is regarded as a "rear-view mirror with real thinking ability" in the industry. It is small in size, retractable, less windage resistance, and has a sense of science and technology. At the same time, it can help drivers avoid changing their perspective significantly during driving, so that they can know the surrounding road conditions. Compared with traditional optical rear-view mirrors, CMS has specific and significant advantages:
1. Whole vehicle weight reduction, resistance reduction and noise reduction:
In traditional rear-view mirrors, about 1-2 kg on one side of passenger vehicles and 5-10 kg on one side of commercial vehicles. Supporting such a large weight will certainly increase the thickness of the steel plate of the door and the weight of the whole vehicle. According to the test data of a German enterprise, the use of CMS rear heavy truck can reduce the weight of the whole vehicle by 60-80kg, and the elimination of exterior rear-view mirror can save fuel by 2% - 3%. Take Mercedes Benz Actros as an example, Actros The fuel consumption of the whole vehicle is reduced by 3% through CMS.
In addition, the CMS external equipment only has a camera, and its volume is only 1/3 of that of the traditional rearview mirror at most. The overall design is more consistent with the aerodynamic principle, which can reduce the wind resistance by 90% and further reduce the wind noise. Taking Audi e-tron as an example, the design of the electronic exterior rear-view mirror reduces the drag coefficient of the vehicle to 0.27, which is 0.1 percentage points lower than that of the traditional design vehicle, and improves the driving range.
2. Pain spots in visual blind area:
The effective visual area of the traditional rear-view mirror is fixed. Due to the difference in the driver's height, sitting posture, and eyespot observation, the visual range of observation is also different, and it is impossible to adjust the visual range in complex road sections. CMS uses cameras with different sensors and different angles to take real-time multi angle shots around the vehicle body to display the vehicle conditions, blind areas of vision and pedestrians at the rear of the vehicle. The visual angle is more flexible. The visual range is about 3 times that of the traditional rear-view mirror, which can reduce the blind spots by about 10% (about 50% of the wide field of view).
Figure: MAN OptiView electronic rear-view mirror is equipped with several cameras with different focal sections. The largest camera in the box is the telephoto camera, which is used to capture the rear view images of the side of the vehicle and the rear of the trailer. The camera arranged obliquely below is a wide-angle camera, which makes up for the shortcomings of the telephoto camera, and collects wide-angle images of the vehicle perspective, so that the driver can make decisions in advance. A camera is also installed below the swing arm, which is used to collect images near the door and ensure the safety of the most dangerous blind area.
3. Special environment:
Generally speaking, the CMS exterior camera will combine physical shielding and electric heating to make the lens waterproof and snow proof, and the rest will be completed by the later algorithm and the interior display screen, which will greatly improve the visibility in rainy and snowy weather, glare, insufficient light or night driving and other environments. In addition, with the technological innovation, more advanced functions such as active anti dazzle and night vision functions will be integrated, so that the driver's driving safety at night will be more guaranteed.
4. Intelligent experience:
L3+level intelligent driving system needs to collect surrounding images for analysis, and even access to the network platform for traffic scheduling and vehicle safety management. External images become an indispensable source of information. The importance of road information around vehicles must be raised to a certain degree, and CMS can provide the underlying hardware support for it. Although CMS may not be the final information collection scheme for intelligent driving, CMS's requirements for high safety and high quality cameras will improve the overall R&D and application technology of related supporting industries. At the same time, CMS will also have a more comfortable experience in human-computer interaction and driving process.
With the acceleration of the era of intelligent electric vehicles, CMS is increasingly valued by the industry. In 2016 and 2017, the European Union and Japan successively lifted the regulatory restrictions on electronic exterior rear-view mirrors, and Audi, Lexus, Honda, Koenigsegg and other OEMs successively launched mature applications.
Table 1: Models with mass production/planned CMS
CMS key component: camera
CMS is an indirect vision device that can clearly see the rear, side or front vision of the vehicle within the specified field of vision through a system consisting of a camera and a display. This requires the CMS system supplier to have a complete design capability of camera and display systems, especially the lens design, chip selection, ISP/DSP system design and testing capabilities of the CMS camera. For example, the chip selection should meet AEC-Q100, the safety design standard should refer to ISO26262, and the production system should meet IATF16949. The team should have a highly reliable CMS system Long life experience accumulation and development design, engineering, installation and testing capabilities.
Figure: CMS system composition, sourced from Shanghai Yuxing Electronics
1、 Lens selection
Domestic manufacturers of vehicle mounted camera lens started from the production of security lens and basically entered the vehicle mounted field around 2016. Because the existing vehicle mounted cameras do not have high requirements for lens performance, although these manufacturers have accumulated optical experience, they are still very different from CMS in terms of lens requirements.
Figure: Vehicle camera module composition, from Shanghai Yuxing Electronics
1. Lens material
The lens is processed by multiple groups of lenses for concave and convex angles, and combined to meet the performance requirements of optical design. Its optical imaging quality and life are determined by the material. The material can be full glass that can be protected for many years, or resin lens, but the resin lens will become yellow and fuzzy in 2-3 years due to the impact of external ambient light irradiation and internal and external temperature changes.
CMS lens has high requirements for clarity, distortion, stray light and ghost, hydrophobicity and low light imaging ability, and needs to ensure excellent temperature characteristics. Generally, it will adopt the all glass+metal structure.
2. Coating process
A key process of lens is coating. The price will vary greatly with different coating materials, functions and service life. Good coating materials can reduce the reflectivity of glass, improve the transparency of glass, and improve the image quality. The coating process is also divided into cold coating and hot coating. The resin lens is cold coating. The biggest difference between the two coatings is friction resistance and service life.
3. The lens barrel is blackened
The blackening process of the mirror tube determines the glare and ghost area of the image. The cost of oxidation blackening is the lowest, and the SLR camera lens is blackened by a special production process.
4. Assembly process
The lens assembly best reflects the production process level of the lens manufacturer, such as the tolerance between the lens and the lens barrel, the fixation of the lens, and the imaging deployment.
5. CMS camera lens
The cost of the camera is determined by the glass composition, spherical surface, aspheric surface, coating, blackening of the mirror barrel, glass fixation, and waterproof performance. The camera material and process will determine the performance and life of the camera. CMS camera lens is equivalent to professional SLR lens manufactured in batch, which is also the reason why CMS camera lens is expensive.
II CMOS selection
As a safety part of ICV, CMS The complexity of the scene will put forward higher requirements for the hardware statistics and algorithm processing of ISP signal processor, such as colorful car body, rear lamp illumination, etc.
At present, many parts suppliers in the market are evaluating traditional SoC chips, such as IVI central control display chips, DVR recorders and even consumer security monitoring chips to achieve the design of CMS. However, according to the effect of several models that are currently equipped with CMS and have been mass produced, the performance of the traditional SoC chip solution in the CMS system seems to be somewhat "acclimatized", such as color deviation, dark noise, dispersion and ghost, and large time delay under the influence of complex light environment. So what factors should be considered for a CMS scheme that can really adapt to the actual use of vehicles? What is the ideal chip scheme of the current CMS system?
According to a number of industry insiders and relevant experts from the OEMs, in the specific environment where regulations and standards are still being updated, the FPGA solution with the advantages of extremely low latency, hardware upgradeability, flexible adaptation, etc., should be the best choice for the current CMS system. The quick on board demo and the quick compliance review after the implementation of the laws and regulations do not need to change the original design, and can maximize the differentiated needs of different customers. Even the replacement of core materials such as screens or cameras only needs to directly update the logic units and core functions according to the hardware characteristics, which greatly reduces the development cycle and costs of CMS manufacturers and vehicle manufacturers, Accelerated the mass production of CMS products.
Figure: AMD Xilinx vehicle specification level chip product series
It is understood that AMD Xilinx, together with its partner iWaySense, has jointly created a core image processor IP dedicated to CMS products. It has specially designed the scenes of CMS applications, which has excellent image quality and can also achieve extremely low latency. In addition, combined with the advanced image laboratory and debugging service support capabilities of iWayLab, the image debugging partner, and the domestic localization team, it can further accelerate the launch and mass production of the OEM CMS project.
In addition, the structure of the camera also needs some special treatment. For example, the component shell of the external camera should be designed to prevent water drops from falling on the lens, and the lens should be additionally covered with a waterproof coating; In order to reduce the performance failure of cameras exposed to dust and rain water, built-in heaters are equipped to prevent icing or fog. Some schemes are also equipped with light sensors, which can automatically reduce the glare of other car headlights.
At present, foreign suppliers of electronic exterior rear-view mirror mainly include Valeo, Magna, Donghai Physicochemical, Bosch, etc., all of which regard it as an important part of ADAS or intelligent driving system. Domestic and foreign rear-view mirror suppliers mainly include Shanghai Yuxing Electronics, Senpeng, Yuanfeng Technology, Huayang Electronics, Hangsheng, Desai Xiwei, etc. Shanghai Yuxing has provided Yutong and Senpeng has provided BYD K9 with an integrated solution of electronic exterior rear-view mirror+traditional rear-view mirror; In January this year, Yuanfeng Technology also officially won the designation of Xiaopeng Automobile CMS project; In February, Yuxing Electronics won the designation of Deepway Smart Truck CMS project.
Progress of CMS regulations in China
Since the implementation of GB15084-2013 standard for five years, some problems have been exposed, such as incomplete test methods, updated versions of quoted standards, and inability to adapt to the development of current automotive technology. In order to standardize the healthy development and technical improvement of the industry, achieve the purpose of integrating with international standards, and standardize and improve the development of the domestic automobile indirect vision device industry, in December 2018, the National Automobile Standardization Technical Committee, under the guidance of the Ministry of Industry and Information Technology, launched the research and revision of this standard.
On June 3, 2020, the Ministry of Industry and Information Technology issued the draft of the national mandatory safety standard GB15084 (Performance and installation requirements for indirect vision devices for motor vehicles) for comments, and the new standard added the CMS projection height requirements and measurement methods to the CMS section; Functional requirements for Class I to IV CMS are added, and functional requirements for Class V and VI CMS are modified; Impact requirements and test methods for CMS are added.
According to the current public information, the standard is expected to be released in the middle of this year and will be implemented from January 1, 2023. In the second half of 2022, automobile manufacturers can begin to declare new models equipped with CMS and carry out fixed-point experiments, and the CMS market will enter the stage of rapid mass production.
Table 2: Regulatory progress in each region
Challenges and pain points
The CMS system needs to meet the GB15084 standard and vehicle safety level D. Its technical threshold, safety level, performance indicators and other stringent requirements are by no means the reverse monitoring screen, tachograph, streaming media and other automotive accessories. In addition, according to the calculation of replacing all traditional rear-view mirrors, the domestic market of front mounted electronic rear-view mirrors for commercial vehicles and passenger vehicles is close to 100 billion yuan. Although the prospect is very broad, there are also some difficulties to be overcome in reality:
1. Solve imaging in low light and complex environment
The main challenge for all automotive imaging systems is to improve imaging in low light conditions, while improving resolution and dynamic range of imaging. In order to avoid the image supersaturation caused by the headlights when the rear vehicle approaches, the CMS must have good imaging quality, the low illumination must be below 1Lux, and the dynamic range must exceed 110db. At the same time, the imaging system must have enough pixels to fill the monitor with high level resolution, which are beyond the limitations of traditional pixel technology.
Vehicle mounted cameras are different from security surveillance cameras and other video cameras. For glare, you can choose to install a shield or change the camera installation position to avoid the exposure of strong light sources. How to ensure clear image quality poses a higher challenge to system technology.
2. Impact of lamp flashing on camera
Another major challenge is the impact on the current image sensor when LED lights or street lights flash. In the rearview mirror on the display screen, the daytime driving lamp will flash due to pulse width modulation (PWM), which may cause the driver to mistakenly think that an emergency situation has occurred or the police car is approaching, affecting safety. Many daytime running lights have a PWM frequency of 90-300Hz. It is very difficult to image in this range when the sensor exposure is small under daytime conditions.
3. Reliable imaging for long-term use
The camera replaces the rear-view mirror, which not only solves the problem of "presence", but also covers the blind area of the traditional rear-view mirror; More importantly, the problem of "seeing clearly" should be solved. There are other headlights in the field of vision, but other obstacles should still be seen clearly. As long as the car is powered on, the camera that replaces the rear-view mirror will work for a long time and still need to be used when driving at high speed. It has higher requirements on all aspects of the camera, and brings higher challenges in high pixel, distortion free, wide dynamic, low illumination, high frame rate, and high reliability.
4. Cable and connector selection and matching problem
With the increase of camera sensor resolution, the cost of transmitting camera data to the display will also increase. In the case of standard definition camera system, video data is transmitted together with analog composite video, which is a common camera system in the market at present. Because the data bandwidth is also very low, the cost of cables and connectors in this case is relatively low. After the introduction of high-definition cameras, the cost of cables and connectors will also increase according to the type of data transmission technology used.
At present, the most common vehicle HD video transmission technology is the digital serializer/deserializer called "SerDes". The problem with existing SerDes is that compared with analog composite video systems, it requires relatively expensive cables and connector types. Another challenge of SerDes is that there are many SerDes standards (similar functions) in the market at present, and they are not compatible with each other. Therefore, OEMs and primary system manufacturers usually need to select a specific SerDes standard and stick to it, regardless of whether the competitive standard has better characteristics. Due to the delay caused by IP based systems, IP camera systems do not perform well in such applications. The rear-view mirror replacement system is required to have a minimum delay, which can be achieved by analog video and SerDes.
5. Higher computing power and memory requirements
The image sensor and imaging processor must first pass the vehicle specification (AEC-Q100) to meet the requirements of vehicle parts, and the required tests are quite complex. In addition, the problems of power consumption and heat dissipation also need attention in the design of high-definition image sensor. More and more high-definition vehicle photography opportunities bring many new applications and rich image data, which also means that processors need higher computing power and memory. At present, the demand for high-definition image sensors is increasing, and the traditional CVBS interface cannot support high-definition images. The new LVDS and Ethernet AVB interfaces may be the mainstream of the next generation of intelligent camera for vehicles.
6. Professional division
The professional division of domestic camera module is very professional, including structural design, ISP calibration, module production. At present, traditional rear-view mirror suppliers are mainly good at physical structure and optics, but do not have electronic circuit and image processing technology, so it is difficult to provide CMS systems with high safety standards. However, IVI suppliers providing automobile central control systems lack the knowledge and technology accumulation of traditional optical mirrors, the foundation of image optical processing, and the design experience of providing systems with high safety requirements, and are also difficult to enter the CMS system market.
At present, only a few enterprises can grasp the needs of terminal customers, match COMS, lens and external structure according to the needs, and have full-time ISP engineers responsible for image deployment.
In addition, the popularization of mass production of CMS, in addition to the breakthrough in technology and the provision of safer and more reliable products by CMS suppliers, needs more matching support from the OEMs in the early design of vehicle models.
summary
Electrification, intelligence, networking and sharing, the automotive industry is undergoing a once-in-a-century major change. The development of basic technology of image optics and automotive intelligence makes it possible for electronic rear-view mirrors to replace traditional optical rear-view mirrors. Similar to the transformation of the glass rear-view mirror industry when touch screen phones replaced key phones to reconstruct the mobile phone ecosystem, Establish an ecological environment with high-quality video camera+5G+AI as the core to enable driving safety. The turning point of CMS has come, and the curtain is slowly opening. We will wait and see who will win the first place.
