1.35 Mpixel CMOS image sensor for driver assistance & driverless cars

October 23, 2014 // By Graham Prophet
This automotive image sensor combines image quality with ASIL-ready support functions that will be required for future development of autonomous vehicles, providing imaging in moonless night conditions down to 0.005 lux (SNR1 illuminance); 125dB HDR output without additional ISP chip; reduced flicker effect of pulsing LED lights; and self-testing ASIL support functions for emerging safety systems.

Melexis' 3rd generation of automotive image sensors, the MLX75421 Blackbird, is an automotive grade, high dynamic range (HDR) image sensor with an extensive set of on-chip functional safety (ASIL) support functions. It has been architected for automotive safety applications such as automatic emergency braking (AEB), electronic mirrors/camera monitor systems (CMS) and autonomous evasive steering. The device is also aimed at next-generation viewing applications such as surround/rear view systems with object detection functions.

The ASIL support functions are aimed at a cost-effective implementation of ASIL systems. These functions take care of the digital aspects but moreover also cover the sensor’s analogue functions and the sensor interface. As a result, the sensor generates an embedded 'frame valid’ flag for every frame based on intensive run-time self-testing.

With a resolution of 1344 x 1008 pixels, the sensor has a 1/3-in. optical format. It features a 4 stabilised-kneepoint HDR response curve which provides up to 125 dB of HDR inside every frame. The HDR full frame rate is 45 fps, while 60 fps can be achieved when capturing image data from 800 rows. This makes the image sensor also compatible with 720p applications. The device runs fully automatically in HDR mode without the need for a companion chip.

Designed for low noise operation, the MLX75421 Blackbird has a dark leakage of less than 5 electrons/sec at 25°C and dark temporal noise of less than 4.4 electrons for a 1/30 sec exposure time. This results in an SNR1 illuminance value of 0.005 lux for light with a wavelength of 535 nm over a 1/30 sec exposure time. The device has a wide operating temperature range of -40°C to +115°C.