METHOD OF SPECKLE-NOISE PATTERN REDUCTION AND APPARATUS THEREFOR BASED ON REDUCING THE TEMPORAL-COHERENCE OF THE PLANAR LASER ILLUMINATION BEAM (PLIB) AFTER IT ILLUMINATES THE TARGET BY APPLYING TEMPORAL INTENSITY MODULATION TECHNIQUES DURING THE DETECTION OF THE REFLECTED/SCATTERED PLIB

摘要

A planar laser illumination and imaging (PLIIM) based camera system capable of producing digital images with reduced levels of speckle-pattern noise. The PLIIM based camera system comprises a planar laser illumination array (PLIA) including a plurality of laser diodes for producing and projecting a planar laser illumination beam (PLIB) so as to illuminate an object as it is moving past said PLIIM based camera system. An image formation and detection (IFD) module is provided having a image detection array and imaging forming optics for providing the image detection array with a field of view (FOV). The PLIB and FOV are arranged in a coplanar relationship along the working range of the PLIIM based camera system so that the PLIB illuminates primarily within the FOV of the IFD module. A speckle-pattern noise reduction subsystem is integrated with the IFD, for reducing the temporal-coherence of said planar laser illumination beam (PLIB) after the PLIB has illuminated and reflected/scattered off the target object. The speckle-pattern noise reduction subsystem carries out a temporal intensity modulation technique after the reflection/scattering of the PLIB off the target, so that the laser illumination reflected/scattered off the object consists of temporally coherent-reduced planar laser illumination, causing numerous substantially different time-varying speckle-noise patterns to be produced at the image detection array over the photo-integration time period thereof. The numerous substantially different time-varying speckle-noise patterns are detected at the image detection array over the photo-integration time period, and the detected speckle-noise patterns are temporally averaged at said image detection array during the photo-integration time period thereof. As a result of such temporal averaging, the RMS power of observable speckle-noise patterns is reduced at the image detection array. By virtue of the present invention, it is now possible to enjoy the benefits of laser-based illumination during high-speed imaging operations, without the adverse effects of speckle-pattern noise.