Project overview

The optical system is used to identify, illuminate and trace moving object, performing the following functions:

• Emit a pulsed 640nm laser radiation and receive return pulses by photodiode (lidar);
• Use a scanning system that allows to scan over a plane with the radiation for tracking and handling mobile target;
• Emit a high peak power impulsive radiation at 1550nm (marker radiation).

Project development

An optical diagram was made with two laser diodes at two different wavelengths (640nm and 1550nm) each with its own collimator and beam expander. The project includes a photodiode with a special focusing optics: the reflected radiation is concentrated in order to increase efficiency; two selective dichroic mirrors direct the radiation of different wavelenght in the right path and to a fixed-speed rotating mirror for scanning. The prototype scans the area with a frequency of 20.000 readings per second; if a target is identified, it is illuminates with pulsed radiation at 1550nm (eye-safe wavelength).

Results

The lidar part was developed according to classic scheme: for distances limited to a few meters (4-6m) the signal is sufficiently intense and the attenuation of the dichroic mirror don’t significantly affects transmitted and reflected radiation. The evaluation of the installed prototype is positive, the system satisfies the specifications.
The lighting part of the target allows to meet the application specifications so allows to maintain impulsive radiation for as long as the object remains in the scanning area. Lidar synchronization with the illuminator required development of a high-speed driver electronics, given the very short scan times.