Cámara lidar de escaneo mems para imagen 3d de resolución espacial variable
- Autores: Jordi Riu Gras
- Directores de la Tesis: Santiago Royo Royo (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Ferran Laguarta Bertran (presid.), Ignacio Garcés Gregorio (secret.), José Díaz Caro (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Óptica por la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
The main objective of this doctoral thesis is the research, development and implementation of a lidar camera for three dimensional imaging based on pulsed time-of-flight technique (TOF). AA optical metrology technique measures distances from the illumination of an object by m·eans of a light source and basing on the time count and the known constant of the speed of light In the pulsed version, nanosecond laser pulses are emitted to the object and the system measures the time that the pulse takes to go there and comeback again to the receiver. Through a sequential process implemented by a scanning system, it is possible to generate three-dimensional im.ages .
The lidar camera architecture investigated in this work is based on MEMS (MicroElectroMechanical Systems) type scanning where its use is the main contribution to the state of the art. Arnong all the innovative features that the MEMS scanning provides, it's wortfi to highlight the capability of generating high spatial resolution 30 imaging, the elimination of moving parts such as mirrors or rotating prisms, as well as the ability to provide a high imaging frame rate. lt also allows a "digital" modulated balance between the image spatial resolution and the frame rate of the image. lt makes possible to tune this · balance just changing the scanning configuration digitally. This is one of the most remarkable characteristics since it's not seen in any other known scanning approach .
Besides, this work also investigates the use of a SiPM detector (Silicon Photomultiplier) for both atmospheric and three dimensional lidar applications. A comprehensive evaluation of the detector is carried out by using an atmospheric lidar system, and its performance is compared with the well-known detectors used in this environment, such as PMTs · (Photomultiplier tubes). Basing on the obtained results, it.was decided to integrate the SiPM as the main detector for the lidar camera architecture presented on thie thesis.
Additionally, a dedicated TDC (Time-to-Digital Converter) Círcuit specifically designed to equip the lidar camera system with two innovative capabilities has been designed, developed and implementad. On the one hand, in order to obtain high spatial resolution images combined with good frame rate, it is necessary from the TDC to provide high point measurement rates, in the order of hundreds of KHz and in sorne cases up to 1MHz. The number was not available in any commercial off-the-shelf TDC . On the other hand, the TDC is intended to provide tolerance to degraded vis ibility environments, for example, rain, snow, dust or fog environments . In this cases, the pulse reflected at the object and received the system is essentially a complex waveform that includes different pulses generated by the intermediate elements. In order to digitize the whole wav(3form , a TDC has been designed to allow multi-hit up to 10 consecutive pulses for each laser pulse. To do so, the TDC measuring core needs to have a large bandwidth and no dead times between consecutive edges . The implemented TDC circuit provides both a high point rate measurement and whole waveform digitization . This circuit has been implemented through an ASIC (Application Specific lntegrated Circuit) and has been manufactured in CMOS 130nm technology. As far as it is known, there are no other commercial off-the-shelf TDCs that combine both benefits.
The results of this thesis have raised 8 licensed patents currently in operation, and to the constitution of a spin-off company that is currently industrializing the results described here.
