LED "flashing" is no longer the "blocking tiger" to achieve automatic driving

Strobe, there is frequency flicker, light changes quickly and repeatedly with time called stroboscopic, the direct feeling is that the light source is mobilized and unstable. The reason for the stroboscopic generation is that the luminaire is powered by an alternating current, and its brightness varies with the periodic variation of the alternating current.

LED lights are common sources of stroboscopic hazards. They are widely used in traffic lights, lights, etc. It seems that there is nothing wrong with ordinary people, but when the camera starts to be used as a vehicle information source, LED lights The danger of stroboscopic began to appear.

LED strobe causes interference to the car camera to collect information

Today's car camera system uses a CMOS image sensor, which is a high-definition sensor capable of reaching 100-200 megapixels. The single/binocular camera is integrated with the radar system to provide drivers with information on the speed, distance and shape of obstacles or moving objects. Autopilot is nothing more than a deep learning algorithm to analyze the information collected by the camera, and then replace the human driver to make driving behavior.

Analysis of the reasons, Liu Qi pointed out: "The current LED lamp frequency is mostly between 90-270 Hz, usually a light and dark cycle is less than or equal to 11 milliseconds. The HDR camera on the car streaming rearview mirror is usually a frame image. 16.6 milliseconds, but the exposure time is mostly between 3-4 milliseconds. Therefore, the camera cannot capture LED pulses at any exposure time (long, short or very short) and the LEDs cannot be observed in the video."

How to solve the LED "blinking"?

From the current situation, to achieve a high level of automatic driving, the car is inseparable from the camera. If you do not solve the problem of LED flashing, safety should always be marked with a question mark. Suppressing and eliminating the "blinking" of LED lights is a hurdle on the road to study autonomous driving.

Liu Qi said that there are currently three ways to solve the "flicker" problem of LED lights, namely LOFIC technology, chopping technology and separate pixel technology. The principle is to ensure that at least 11ms of exposure time is required to capture a 90Hz LED pulse. The LFM (reduce or eliminate LED flicker) technology requires the camera to extend the exposure time and make it longer than the LED drive cycle without overexposure. And to maintain a certain dynamic range level, then the problem is solved.