Detectors & Imaging

Position sensing with photodiodes

Feb. 1, 2002

Two complementary technologies allow system optimization for optical-beam centering and/or quantitative measurement of lateral beam displacement.

Jeff Hecht

FIGURE 1. The most common multielement photodiodes used for position-sensing applications are the bi-cell and quad-cell.

Two complementary technologies allow system optimization for optical-beam centering and/or quantitative measurement of lateral beam displacement.

Position-sensing photodiodes provide quantitative information about the position of an incident light beam or spot image. These photodiodes have been in use for many years and as optical technology continues to find increasing application in areas as diverse as telecommunications, biomedicine, data storage, manufacturing, test and measurement, and aerospace/military, the need for these workhorse devices will likely continue to thrive.

Two technologies are currently used for position sensing: multielement photodiodes and position-sensing (or lateral-displacement) photodiodes.

About the Author

Jeff Hecht | Contributing Editor

Jeff Hecht is a regular contributing editor to Laser Focus World and has been covering the laser industry for 35 years. A prolific book author, Jeff's published works include “Understanding Fiber Optics,” “Understanding Lasers,” “The Laser Guidebook,” and “Beam Weapons: The Next Arms Race.” He also has written books on the histories of lasers and fiber optics, including “City of Light: The Story of Fiber Optics,” and “Beam: The Race to Make the Laser.” Find out more at jeffhecht.com.