Design and Performance of a Laser-Based Compact Position Sensor for Long Standoff Distance

In this paper, we design and demonstrate a compact laser-based sensor for measurement of the position of a target placed at a long standoff distance. To make the sensor compact, the beam-folding technique was used in the path of the converging light from the lens, which ultimately falls on the position-sensing detector (PSD). The position resolution of 1 mm at a standoff distance of ~1000 mm between the target and the light collecting lens was achieved for the developed sensor. The calibration of the sensor was done based on the output voltage obtained at PSD with near and far displaced position of the target. The sensor output was found to be linearly varying with the target position. The sensor performance was tested for different target roughness and ±10° variation in angle between the laser and the target surface. The effect of temperature on the output of developed sensor was also studied and the error in measurement was found to be within the sensor resolution. The developed sensor has many potential applications in industrial environments where the position has to be measured for targets having different surface roughness and variable ambient temperature.