Speckle noise reduction based on induced mode Hopping in a semiconductor laser diode by drive current modulation

We propose and demonstrate a speckle reduction technique in a laser diode projection system. By modulating the drive current of the laser diode continuously, we manage to generate independent longitudinal modes that arise from mode hopping. Since these modes have no fixed relationship between each other they act as independent sources which results in speckle reduction in the image. We experimentally demonstrate a speckle reduction factor of 2.17, which is in excellent agreement with our theoretical expectations. We conclude that mode hopping in laser systems can be used effectively to suppress speckle noise. (C) 2015 Elsevier Ltd. All rights reserved.