Multidimensional measurement by using 3-D PMD sensors
Abstract. Optical Time-of-Flight measurement gives the possibility to enhance 2-D sensors by adding a third dimension using the PMD principle. Various applications in the automotive (e.g. pedestrian safety), industrial, robotics and multimedia fields require robust three-dimensional data (Schwarte et al., 2000). These applications, however, all have different requirements in terms of resolution, speed, distance and target characteristics. PMDTechnologies has developed 3-D sensors based on standard CMOS processes that can provide an optimized solution for a wide field of applications combined with high integration and cost-effective production. These sensors are realized in various layout formats from single pixel solutions for basic applications to low, middle and high resolution matrices for applications requiring more detailed data. Pixel pitches ranging from 10 micrometer up to a 300 micrometer or larger can be realized and give the opportunity to optimize the sensor chip depending on the application.
One aspect of all optical sensors based on a time-of-flight principle is the necessity of handling background illumination. This can be achieved by various techniques, such as optical filters and active circuits on chip. The sensors' usage of the in-pixel so-called SBI-circuitry (suppression of background illumination) makes it even possible to overcome the effects of bright ambient light. This paper focuses on this technical requirement. In Sect. 2 we will roughly describe the basic operation principle of PMD sensors. The technical challenges related to the system characteristics of an active optical ranging technique are described in Sect. 3, technical solutions and measurement results are then presented in Sect. 4. We finish this work with an overview of actual PMD sensors and their key parameters (Sect. 5) and some concluding remarks in Sect. 6.