The three-dimensional perception of the environment is central in applications like advanced driver assistance systems, self-driving cars or industrial robotics and security.
The principle of LiDAR (Light Detection And Ranging) is based on the determination of the time between sending an impulse of laser light and receiving the light reflected by an object in the beam path. Since the velocity of light is known, the measured time directly yields the distance the between emitter and the reflecting object. In LiDAR cameras, many of these measurements are combined to obtain a three-dimensional representation of the surrounding. Possible methods are scanning LiDAR, which capture the environment by scanning a point or a line across the scene as well as Flash LiDAR which illuminate the whole scene with a single pulse of laser light.
Basic elements of LiDAR Systems are
- Emitter: a source of pulsed laser light with typical wavelength of 905 nm or 1550 nm.
- Receiver: highly sensitive photodiodes which detect the reflected light.
- High resolution time-to-digital converter determine the time between emitting and receiving light.
- Signal processing algorithms, which carry out signal filtering operations and die determine the distance from the measured time.
Especially in complex and dynamic scenarios occurring in traffic LiDAR cameras require fast, reliable but also cost efficient detectors. In relation to LiDAR Fraunhofer IMS offers the development and production of sensors as well as expertise in signal processing, system simulation and the development of LiDAR camera systems. Among these, the key competence offered is the development and production of highly dynamic CSPAD detectors. CSPAD detectors are CMOS integrated single-photon avalanche diodes (SPAD) with on-chip readout circuits. The implementation in a standard CMOS process allows cost efficient manufacturing and the design of compact sensors for applications that require high resolution imagers.
Along with the research on of novel detectors Fraunhofer IMS has acquired a solid background in signal processing and develops photon coincidence circuits that allow the detectors to adapt to the intensity of the ambient light in order to increase the dynamic range of the measurement even further. Moreover researchers at Fraunhofer IMS develop plug-and-play LiDAR cameras in order to evaluate the CSPAD detectors and signal processing algorithms in realistic and application specific measurement conditions. These cameras can also be easily adapted to customer specifications, for example in order to facilitate testing of laser modules in LiDAR applications. Further models of cooperation include customized chip development but also the transfer of processes and intellectual property to the customer.