Optical system design of direct detection short-pulsed laser proximity sensor

Korkmaz, Emrah
In this study, we designed a Laser Proximity Sensor system that measures the distance by analyzing the echo signal reflected from object using time-of-flight principle. The sensor makes a direct-detection using a short-pulsed laser and is capable of detecting objects and measuring distances in a range between 0.5 m and 10 m far from the system. Reflectivities of objects are assumed to lie between 20% and 90% and obeying to Lambertian BSDF (Bi-Directional Scatter Distribution Function). A mathematical model for the laser propagation in the atmosphere was developed. Receiver and transmitter optical system design were performed using a ray tracing software (Zemax). Laser central wavelength was measured for the temperature region of interest (i.e. 0 – 70 C). A bandpass optical filter was designed to block the background light having a wavelength ranging outside of the laser’s emission spectrum at its all operation temperatures. Various signal-processing algorithms were developed to extract the echo signal buried in noise. Finally, laser diode driver, high-speed receiver amplifier and time to digital converter circuit board were designed.