IMPLEMENTATION OF A LONG RANGE LRF BY AUTOMATIC MULTI-MODE MEASUREMENT SCHEME

Abstract

A long range Laser Range Finder (LRF) is proposed and developed in this paper. A mathematical model, which relates object distance and Position Sensitive Detector (PSD) voltage output is investigated. LRF is a single point optical triangulation instrument, which detects distance information quickly and easily without touching the object being measured. It can be used in real-time control application. This kind of instrument is available in today's market, however, it is limited to a short range application only (maximum range of about 400 mm). The nonlinearity is inherent in this kind of instrument, resulting the sensitivity and accuracy change with the distance nonlinearly. Sensitivity and accuracy becomes worse abruptly when distance to the object being measured is longer than a limited range. The proposed long range LRF is developed to achieve a longer operation range of about 1 m or more. To improve the instrument accuracy at long range, automatic multi-mode measurement scheme is introduced and implemented. The PSD output voltage is selected properly from a corrected mode. Then, it is shifted and scaled depending on the mode of operation before feeding to analog to digital converter-(ADC) automatically. This automatic multi-mode measurement scheme has shown the ability to make the accuracy finer considerably depending on the number of mode being used.