CSPAD

Advanced driver assistance systems (ADAS) require fast and reliable sensors. Autonomous vehicles have to capture their environment with absolute confidence. To meet these specifications, CSPAD detectors (standing for CMOS SPAD) by Fraunhofer IMS combine highly sensitive three-dimensional imaging with safe algorithms for efficient operation even in changing weather conditions. The following video shows the measurement principle of direct LIDAR implemented in the LiDAR camera Owl developed by Fraunhofer IMS with a CSPAD double line sensor.

CSPAD Sensor SPADeye2 for LiDAR applications
© Fraunhofer IMS

Dual line CSPAD Sensor SPADeye2 with 192x2 pixels for Solid-state LiDAR applications

CSPAD3000 kilopixel SPAD arrays
© Fraunhofer IMS

Wafer with CSPAD image sensor arrays before wafer-to-wafer bonding to read-out electronics

Due to the ongoing progress in advanced driver assistance and self-driving cars, there is an increased demand in highly dynamic, efficient and reliable sensors for three-dimensional imaging using LiDAR (light detection and ranging) cameras. To meet the specifications set by the challenging applications, CSPAD detectors by Fraunhofer IMS combine highly sensitive three-dimensional imaging with safe algorithms for efficient operation even in changing weather conditions. The primary goal is to achieve maximum measurement ranges at a minimum of overall system costs.

CSPAD technology is based on the integration of single-photon avalanche diodes (SPAD) in an automotive certified 0.35 µm CMOS process optimized for optoelectronic applications. This allows integrating SPAD detectors and readout electronics (ROIC) on a single chip, for example in the dual line sensor SPADeye2 with 2x192 pixels with and pixel-dedicated time-to-digital converter. Moreover, the 3D integration of SPAD and ROIC by wafer-to-wafer or chip-to-wafer bonding enables backside-illuminated CSPD detectors. The stacked arrangement of image sensor and readout circuits results in an increased efficiency as well as more compact sensors. Thereby, CSPAD focal plane arrays with thousands of pixels for high resolution Solid-state LiDAR Systems can be realized.

One of the key features of CSPAD detectors developed by Fraunhofer IMS is the pixel-integrated adaptive photon coincidence circuit for ambient light suppression. Only with these smart pixels an increased range at high levels of ambient light and the reliable distance measurement under changing weather conditions can be guaranteed.

Key competence of Fraunhofer IMS is the development of novel detectors. On request, the development of customized sensors is possible as well.

However, Fraunhofer IMS also provides a range of LiDAR related services that go beyond detector development. Going along with the CSPAD sensors evaluation boards as well as complete LiDAR cameras with the corresponding software are being offered. These plug-and-play devices are designed to evaluate both the CSPAD detectors as well as routines for signal processing in realistic and application specific measurement scenarios. Furthermore, researchers at Fraunhofer IMS carry out system simulations and are actively engaged in developing novel signal processing algorithms to improve distance resolution and range even further.