A hand-supportable linear-type planar laser illumination and imaging (PLIIM)
based
device comprising a linear image formation and detection (IFD) module having a
linear array of image detection elements and also image formation optics having
a field of view (FOV) focusing a linear image of an object onto the linear array
of image detection elements. A pair of planar laser illumination arrays (PLIAs)
is arranged on opposite sides of the linear image formation and detection module,
and produces a plurality of spatially-incoherent planar laser illumination beam
(PLIB) components that are optically combined with respect to other PLIB components
so as to produce a composite planar laser illumination beam (PLIB) that is arranged
in a coplanar relationship with at least a portion of the FOV. Each PLIA includes
a plurality of planar laser illumination modules (PLIMs). Each PLIM includes a
laser diode and beam focusing and diverging optics for producing one spatially-incoherent
PLIB component. The composite PLIB produces a number of substantially different
individual speckle noise patterns at the linear array of image detection elements
during the photo-integration time period thereof. The speckle noise power observed
at the linear array of image detection elements is reduced through temporal averaging
of the individual speckle noise patterns during the photo-integration time period.
By virtue of the present invention, it is now possible to use visible laser diodes
(VLDs) to produce speckle-reduced images of objects suitable for OCR processing,
while enjoying improved working distances offered by planar laser illumination techniques.