1、汽车英文文献A high speed tri-vision system for automotive applicationsMarc Anthony Azzopardi & Ivan Grech & Jacques LeconteAbstractPurpose Cameras are excellent ways of non-invasively monitoring the interior and exterior of vehicles. In particular, high speed stereovision and multivision systems are impor
2、tant for transport applications such as driver eye tracking or collision avoidance. This paper addresses the synchronisation problem which arises when multivision camera systems are used to capture the high speed motion common in such applications. Methods An experimental, high-speed tri-vision came
3、ra system intended for real-time driver eye-blink and saccade measurement was designed, developed, implemented and tested using prototype, ultra-high dynamic range, automotive- grade image sensors specifically developed by E2V (formerly Atmel) Grenoble SA as part of the Europea n FP6 project -SENSAT
4、ION (adva need sen sor developme nt for atte nti on stress, vigilance and sleep/wakefulnessmonitoring). Results The developed system can sustain frame rates of 59.8 Hz at the full stereovision resolution of 1280 480 but this can reach 750 Hz when a 10 k pixel Region of Interest (ROI) is used, with a
5、 maximum global shutte speed of 1/48000 s and a shutter efficiency of 99.7%. The data can be reliably transmitted uncompressed over standard copper Camera-Link? cables over 5 metres. The synchronisation error between the left and right stereo images is less than 100 ps and this has been verified bot
6、h electrically and optically. Synchronisation is auto- matically established at boot-up and maintained during resolution changes. A third camera in the set can be configured independently. The dynamic range of the 10bit sensorsexceeds 123 dB with a spectral sensitivity extending well into the infra-
7、red range. Conclusion The system was subjected to a comprehensive testing protocol, which confirms that the salient require- ments for the driver monitoring application are adequately met and in some respects, exceeded. The synchronization technique presented may also benefit several other auto- mot
8、ive stereovision applications including near and far- field obstacle detection and collision avoidance, road condition monitoring and others.Keywords Synchronisation . High-speed automotive multivision . Active safety . Driver monitoring . Sensors1IntroductionOver the coming years, one of the areas
9、of greatest research and development potential will be that of automotive sensor systems and telematics 1, 2. In particular, there is a steeply growing interest in the utilisation of multiple cameras within vehicles to augment vehicle Human-Machine Interfacing (HMI) for safety, comfort and security.
10、For external monitoring applications, cameras are emerging as viable alternatives to systems such Radio, Sound and Light/Laser Detection and Ranging (RADAR, SODAR, LADAR/LIDAR). The latter are typically rather costly and either have poor lateral resolution or require mechanical moving parts.For vehi
11、cle cabin applications, camerasoutshine other techniques with their ability to collect large amounts of information in a highly unobtrusive way. Moreover, cameras can be used to satisfy several applications at once by re-processing the same vision data in multiple ways, thereby reducing the total nu
12、mber of sensors required to achieve equivalent functionality. However, automotive vision still faces several open challenges in terms of optoelectronic-performance, size, reliability, power con- sumption, sensitivity, multi-camera synchronisation, inter- facing and cost.In this paper, several of the
13、se problems are addressed. As an example, driver head localisation, point of gaze detection and eye blink rate measurement is considered for which the design of a dash-board-mountable automotive stereovision camera system is presented. This was developed as part of a large FP6 Integrated Project - S
14、ENSATION (Advanced Sensor Development for Attention, Stress, Vigilance and Sleep/Wakefulness Monitoring). The overarching goal of exte ndable to multivisi on systems 5 -8.The camera system is built around a matched set of prototype, ultra-high dynamic range, automotive-grade, image sensors specifica
15、lly developed and fabricated by E2V Grenoble SA for this application. The sensor which is a novelty in its own right, is the AT76C410ABA CMOS monochrome automotive image sensor. This sensor imple- ments a global shutter to allow distortion-free capture of fast motion. It also incorporates an on- chi
16、p Multi-ROI feature with up to eight Regions Of Interest (ROI) with pre- programming facility and allows fast switching from one image to another. In this way, several real-time parallel imaging processing tasks can be carried out with one sensor. Each ROI is independently programmable on-the-fly wi
17、th respect to integration time, gain, sub-sampling/binning, position, width and height.A fairly comprehensive series of“ bench tests we”re conducted in order to test the validity of the new concepts and to initially verify the reliability of the system across various typical automotive operating con
18、ditions. Additional rigorous testing would of course be needed to guarantee a mean time before failure (MTBF) and to demonstrate the efficacy of the proposed design techniques over statistically significant production quantities.2Application backgroundThe set of conceivable automotive camera applica
19、tions is an ever-growing list with some market research reports claiming over 10 cameras will be required per vehicle 9. The incomplete list includes occupant detection, occupant classification, driver recognition, driver vigilance and drowsiness monitoring 10, road surface condition moni- toring, i
20、ntersection assistance 11, lane-departure warning 12, blind spot warning, surround view, collision warning, mitigation or avoidance, headlamp control, accident record-ing, vehicle security, parking assistance,traffic sign detection 13, adaptive cruise control and night/synthetic vision (Fig.1).2.1Co
21、st considerationsThe automotive sector is a very cost-sensitive one and the monetary cost per subsystem remains an outstanding issue which could very well be the biggest hurdle in the way of full deployment of automotive vision. The supply-chain industry has been actively addressing the cost dilemma
22、 by introducing Field Programmable Gate Array (FPGA) vision processing and by moving towards inexpensive image sensors based on Complementary Metal Oxide Semiconductor (CMOS) technology 14. Much has been borrowed from other very large embedded vision markets which are also highly cost-sensitive: The
23、se are mobile telephony and portable computing. However, automotive vision pushes the bar substantially higher in terms of performance requirements. The much wider dynamic range, higher speed, global shuttering, and excellent infra-red sensitivity are just a few of the characteristics that set most
24、automotive vision applications apart. This added complex- ity increases cost. However, as the production volume picks up, unit cost is expected to drop quite dramatically by leveraging on the excellent economies of scale afforded by the CMOS manufacturing process.Some groups have been actively devel
25、oping and pro- moting ways of reducing the number of cameras required per vehicle. Some of these methods try to combine disparate applications to re-use the same cameras. Other techniques (and products) have emerged that trade-off some accuracy and reliability to en able the use of mono cular visi o
26、n in sce narios which traditi on ally required two or more cameras 10, 15, 16. Dista nee estimati on for 3D obstacle localisatio n is one such example. Such tactics will serve well to con tai n cost in the in terim. However, it is expected that the cost of the imagi ng devices will eve ntually drop
27、to a level where it will no Ion ger be the determining factor in the overall cost of automotive vision systems. At this point, we argue thatFig. 1 Some automotive visi on applicati onsreliability, performa nee and accuracy con sid- erati ons will aga in reach the forefront.In this paper the cost iss
28、ue is addressed, but in a differe nt way. Rather tha n discardi ng stereo- and multi-vision altogether, a low-cost (but still high-performanee) technique for synchronously comb ining multiple cameras is pre- sen ted. Cabli ng requireme nts are likewise shared, result ing in a reducti on in the corre
29、sp onding cost and cable harn ess weight sav in gs.2.2The role of high speed visionA number of automotive vision applications require high frame-rate video capture. External applications involving high relative motion such as traffic sign, oncoming traffic or obstacle detecti on are obvious can dida
30、tes. The n eed for high speed visi on is perhaps less obvious in the interior of a vehicle. However, some driver monitoring applications can get quite demanding in this respect. Eye-bli nk and saccade measureme nt, for in sta nee, is one of the tech niq ues that may be employed to measure a driver s
31、 state of vigilanee and to detect the onset0? f16e epso happe ns that these are also some of the fastest of all huma n moti on and accurate rate of cha nge measureme nts may require frame rates running up to several hun dred hertz. Other applica- tions such as occupa nt detect ion and classificati o
32、n can be accommodated with much lower frame rates but the n the same cameras may occasi on ally be required to capture high speed moti on for visual-servoing such as when modulating airbag release or seatbelt tensioning during a crash situation.2.3A continued case for stereovision/multivisionSeveral
33、 of the applications mentioned, stand to benefit from the use of stereovision or multivision sets of cameras operating in tandem. This may be necessaryto extend the field of view or to increase diversity and ruggedness and also to allow accurate stereoscopic depth estimation11. Then, of course, multivision is indeed one of the
