Design of high precision electronics for laser range finder

Resolution of Time to Digital Convertor (TDC) is a critical parameter in determining the overall performance of Time Of Flight based laser range finder system. This paper focuses on designing a high resolution Laser Range Finder (LRF) using Commercial-Off-The-Shelf (COTS) components. The designed LRF consists of a high resolution Time to Digital Convertor using Virtex-4 FPGA, Parallel to USB converter, High Voltage Power Supply and Data acquisition and display module. TDC generates START pulse at pulse repetition frequency (prf). This pulse is fed as trigger to laser TX. Avalanche Photo-Diode (APD) receiver with high voltage bias (~140V) generates a STOP pulse on receipt of reflected laser beam. This pulse is level translated and fed to TDC as STOP pulse. Digital Clock Manager (DCM) is used to achieve clock interpolation for improving resolution beyond 1 clock period. The output of TDC is parallel 16-bit digital count which is converted to serial USB protocol and interfaced to PC based data acquisition system. The raw data is processed and distance information is derived after calibration with known distance sets. Graphical User Interface (GUI) is developed for display, record and calibration. Full system resolution of about 22 cm is achieved in hardware for a range of 10m. The system has a power consumption of 6.15W.