Planar laser illumination and imaging (PLIIM) system employing wavefront control methods for reducing the power of speckle-pattern noise digital images acquired by said system

Abstract

A planar laser illumination and imaging (PLIIM) based system employing wavefront control methods for reducing the power of speckle-pattern noise within digital images acquired by the system. The system comprises a housing having a first light transmission aperture, a second light transmission aperture, and a third light transmission aperture, wherein the first and second light transmission apertures are optically isolated from said third light transmission aperture spatially aligned on opposite sides thereof. A pair of planar laser illumination arrays (PLIAs) are mounted within the housing, for producing and projecting a first and second planar laser illumination beams (PLIBS) through the first and second light transmission apertures respectively, thereby producing a composite planar laser illumination beam (PLIB) outside of the housing, and illuminating an object therewith as the object is transported past the first, second and third light transmission apertures. An image formation and detection (IFD) module is mounted within the housing, and has a linear image detection array and imaging forming optics for providing the linear image detection array with a field of view (FOV) which is projected through the third light transmission aperture, and along which digital images of illuminated portions of the object can be detected. Notably, digital images contain speckle-pattern noise, and the PLIB and FOV are arranged in a coplanar relationship along the working range of the PLIIM based system so that the composite PLIB illuminates primarily within the FOV of the IFD module. A wavefront control mechanism is mounted within said housing, for controlling one or more characteristics of the wavefront of the composite PLIB so as to reduce either the spatial and/or temporal coherence of the composite PLIB prior to its illumination of a selected portion of the object, so that time-varying different speckle-noise patterns are present in the digital images detected at the linear image detection array. These time-varying different speckle patterns are temporally averaged at the linear image detection array during the photo-integration time period thereof so that the power of speckle-pattern noise at the linear image detection array is substantially reduced.

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