Plant Works & Engineering March 2022

R equirements for precision techniques in manufacturing operations have bolstered the use of laser triangulation sensors on production lines, where they are used for industrial displacement measurement. From its development more than two decades ago, the default measurement technology has used a red laser light source. Red light lasers are as familiar in grocery store checkout stations as they are on the production line. But effective as red lasers are, they can come up short in some applications. To overcome these challenges, Glenn Wedgbrow, Business Development Manager at Micro-Epsilon UK explains that his company developed and patented sensors based on blue laser technology. Basics of linear displacement measurement Wedgbrow explains that in practical terms, linear displacement measurement refers to the movement of an object in one direction along a single axis. In an industrial setting, this could be a discrete piece of material travelling along a belt or roller. As the material passes the measuring device, an output signal from the linear displacement sensor takes measurements in units of millimetres or inches, or even in micrometers. Laser triangulation sensors, says Wedgbrow, pinpoint a narrow beam of laser light onto an object or sample, and light reflected from the object’s surface is focused by a high-quality optical lens onto a charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) image sensor. He explains that as the object moves, the reflected light also changes position on the image sensor, which is computed to detect the position of the object or sample. The triangulation principle involves the measurement of distance on a wide range of material surfaces. To measure displacement, distance and position, laser point triangulation sensors are used. To measure profile and gap, laser line triangulation sensors or ‘laser scanners’ are used. Red vs. blue: when to use which Laser triangulation technology works best according to Wedgbrow in automated position sensing, as well as for passive and dynamic dimensional measurements: “Most often, the laser used in this application is red in colour, and this type of laser suits the vast majority of industrial applications. In addition, because of the red laser’s ubiquity and lengthy development history, a wide variety of cost- effective red laser measurement and sensing systems are available.” “Red lasers perform best when reflected from Process, Controls & Plant Focus on: Sensors & Measurement 32 | Plant & Works Engineering www.pwemag.co.uk March 2022 A comparison of blue and red-light sensor technology PWE spoke to Glenn Wedgbrow, Business Development Manager at Micro-Epsilon UK, about the benefits and limitations of red and blue laser light sensor technologies, as well as those applications where blue lasers are a better choice over traditional red lasers. Principles of laser point triangulation (left) and laser line triangulation sensors (right)