Speckle Reduction with Virtual Incoherent Laser Illumination Using a Modified Fiver Array

A novel technique for speckle reduction is proposed, in which a spatially coherent illumination coming from a laser source is converted into an extended partially incoherent laser illumination without employing any moving mechanical part. This is accomplished by using a combination of semiconductor laser and modified fiber array. The modified fiber array consists of N fiber-guides in which the length difference of any two fibers is greater than the coherence length of the light source. The combined exit surfaces of all fiber guides resembled an extended, quasi-monochromatic partially incoherent source. Out technique requires only an integration time to within the response time of a detector for one image-frame to average speckle, and suffers minimum loss of energy