Design and development of linear optical fiber array based remote position sensor

In this paper, we describe the development of linear optical fiber array based remote position sensor that uses the oblique laser triangulation technique. The developed sensor is compliant for non-contact and precise measurement of the position of the desired target. The configuration of sensor head comprises of a diode laser producing a laser beam striking the target at an oblique angle to the surface, an aspheric lens for capturing the scattered light and transmitting it to the linear optical fiber array and finally to the CCD camera. Contrary to conventional methods, the proposed technique has the potential to be applied in hazardous environments containing radioactivity or electromagnetic noise since the camera is placed remotely from the sensor head. The position change information is inferred from the center of laser spot at CCD camera using the Fourier series method. A position resolution of 1 mm (or ∼1%) at a standoff distance of ∼100 mm between target and light collecting lens was achieved for our selected linear fiber array. Effect of roughness on the accuracy of the measurement was tested by using standard targets of known roughness values. It is seen that the uncertainty in the measured position due to variation in roughness was less than the resolution of our setup for all targets. The error in measurement was high when the roughness of target is comparable to the laser wavelength used due to the diffraction effects at the target surface that ultimately alters the intensity pattern on the optical fiber array.