Don't Overlook UV Sensing

Industrial assembly and inspection operations benefit from several light-based sensing technologies. Noncontact photoelectric sensors detect product presence/absence at distances from millimeters to meters. Color sensors are essential to ensuring uniformity of appearance. And machine vision systems, at the high end of the price/performance scale, carry out tasks ranging from determining the product's orientation on the assembly line to verifying the correct placement of labels.

There's yet another type of light-based detector, the UV fluorescence (sometimes called luminescence) sensor that works by detecting materials that fluoresce naturally or fluorescent marks applied to an object. The fluorescent substance may be invisible to the eye. Exposed to light at the UV end of the spectrum, however, atoms or molecules in the substance become excited and emit light of a characteristic frequency. The UV light source is pulsed, and the sensor is tuned to the same pattern of flashes so that it ignores most other signals. Fluorescent emission ceases abruptly when the UV source is between flashes. The technology is inexpensive and low end, but can handle a surprising variety of jobs.