METHOD OF AND APPARATUS FOR AUTOMATICALLY COMPENSATING FOR VIEWING-ANGLE DISTORTION IN DIGITAL LINEAR IMAGES OF OBJECT SURFACES MOVING PAST A PLANAR LASER ILLUMINATION AND IMAGING (PLIIM) BASED CAMERA SYSTEM AT SKEWED VIEWING ANGLES
First Claim
1. A method of automatically compensating for viewing-angle distortion occurring in digital linear images captured by a planar laser illumination and imaging (PLIIM) based camera system including (i) a linear imaging subsystem having a linear image detection array with an adjustable line rate for producing digital linear images of an object surface, (ii) a laser-based object profiling subsystem for measuring the range of sampled points on an object surface, and (iii) a camera control computer for controlling the operation of said PLIIM based camera system, said method comprising the steps of:
- (a) using said laser-based object profiling subsystem to measure the range of a set of sample points on a surface of an object moving past said PLIIM based camera system;
(b) using said measured ranges of said set of sample points to compute the slope (i.e. surface gradient) of said object surface; and
(c) using said camera control computer to adjust the line rate of said linear image detection array, in proportion to the computed slope of said object surface, so as to automatically compensate for viewing-angle distortion occurring in digital linear images detected by said linear image detection array.
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Abstract
Methods of and systems for illuminating objects using planar laser illumination beams having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of image formation and detection modules employed in such systems. Each planar laser illumination beam is produced from a planar laser illumination beam array (PLIA) comprising an plurality of planar laser illumination modules (PLIMs). Each PLIM comprises a visible laser diode (VLD, a focusing lens, and a cylindrical optical element arranged therewith. The individual planar laser illumination beam components produced from each PLIM are optically combined to produce a composite substantially planar laser illumination beam having substantially uniform power density characteristics over the entire spatial extend thereof and thus the working range of the system. Preferably, each planar laser illumination beam component is focused so that the minimum beam width thereof occurs at a point or plane which is the farthest or maximum object distance at which the system is designed to acquire images, thereby compensating for decreases in the power density of the incident planar laser illumination beam due to the fact that the width of the planar laser illumination beam increases in length for increasing object distances away from the imaging optics. By virtue of the present invention, it is now possible to use both VLDs and high-speed CCD-type image detectors in conveyor, hand-held and hold-under type scanning applications alike, enjoying the advantages and benefits that each such technology has to offer, while avoiding the shortcomings and drawbacks hitherto associated therewith.
82 Citations
18 Claims
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1. A method of automatically compensating for viewing-angle distortion occurring in digital linear images captured by a planar laser illumination and imaging (PLIIM) based camera system including (i) a linear imaging subsystem having a linear image detection array with an adjustable line rate for producing digital linear images of an object surface, (ii) a laser-based object profiling subsystem for measuring the range of sampled points on an object surface, and (iii) a camera control computer for controlling the operation of said PLIIM based camera system, said method comprising the steps of:
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(a) using said laser-based object profiling subsystem to measure the range of a set of sample points on a surface of an object moving past said PLIIM based camera system;
(b) using said measured ranges of said set of sample points to compute the slope (i.e. surface gradient) of said object surface; and
(c) using said camera control computer to adjust the line rate of said linear image detection array, in proportion to the computed slope of said object surface, so as to automatically compensate for viewing-angle distortion occurring in digital linear images detected by said linear image detection array. - View Dependent Claims (2, 3, 4, 5, 6, 7, 18)
wherein step (a) comprises using said laser-based object profiling subsystem to measure the range of a set of sample points on the surface of said object moving under said PLIIM based camera system; and
wherein step (b) comprises using said measured ranges of said set of sample points to compute the slope (i.e. surface gradient) of said object surface measured with respect to the surface of the conveyor belt structure.
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7. The method of claim 1, wherein said PLIIM based camera system is supported along the side of a conveyor belt structure along which said object is transported;
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wherein step (a) comprises using said laser-based object profiling subsystem to measure the range of a set of sample points on the surface of said object moving past said PLIIM based camera system; and
wherein step (b) comprises using said measured ranges of said set of sample points to compute the slope (i.e. surface gradient) of said object surface measured with respect to the edge of said conveyor belt structure.
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18. The method of claim 1, wherein said PLIIM based camera system is supported above a conveyor belt structure along which said object is transported;
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wherein step (1) comprises using said laser-based object profiling subsystem to measure the range of a set of sample points on the surface of said object moving under said PLIIM based camera system; and
wherein step (2) comprises using said measured ranges of said set of sample points to compute the slope (i.e. surface gradient) of said object surface measured with respect to the surface of the conveyor belt structure.
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8. A planar laser illumination and imaging (PLIIM) based camera system for producing digital linear images of a moving object, while automatically compensating said digital linear images for viewing-angle distortion occurring therein as a result of said PLIIM based camera system illuminating and imaging object surfaces having a non-zero slope (i.e. surface gradient) characteristics, said PLIIM based camera system having a working range and comprising:
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a system housing of unitary construction having a first light transmission aperture and a second light transmission aperture, wherein said first and second light transmission apertures are spatially aligned with each other;
a planar laser illumination and imaging (PLIIM) based linear imaging subsystem mounted within said system housing and having a planar laser illumination array (PLIA) including a plurality of laser diodes for producing and projecting a planar laser illumination beam (PLIB) through said first light transmission aperture, so as to illuminate an object as the object is moving past said PLIIM based camera system, and an image formation and detection (IFD) module having a linear image detection array with an adjustable line rate, and imaging forming optics for providing said linear image detection array with a field of view (FOV) which is projected through said second light transmission aperture, and along which digital linear images of illuminated portions of said object can be detected, wherein said PLIB and FOV are arranged in a coplanar relationship along the working range of said PLIIM based camera system so that the PLIB illuminates primarily within said FOV of the IFD module;
an object range measurement subsystem for projecting and scanning a light beam along the surface of said moving object, receiving light reflected from said moving object, generating electrical signals representative to a characteristics of said received light, processing said electrical signals to determine the range thereof relative to the PLIIM-based camera system and generating object range data indicative of the determined range of the moving object;
a camera control computer, mounted within said system housing, for controlling the operation of said linear PLIIM-based imaging subsystem, including the line rate of said linear image detection array in response to object range data generated by said object range measurement subsystem. wherein said camera control computer (1) uses said object range data to compute a line rate compensation factor based on the slope characteristics of the illuminated and imaged object surface;
(2) uses said computed line rate compensation factor to compute an adjusted line rate for the linear image detection array; and
(3) use the computed line rate compensation factor to adjust the line rate of said linear image detection array, so as to automatically compensate said digital linear images for viewing-angle distortion occurring therein as a result of said PLIIM based camera system illuminating and imaging object surfaces having a non-zero slope (i.e. surface gradient) characteristics. - View Dependent Claims (9, 10, 11, 12, 13)
wherein said object range measurement subsystem comprises a laser-based object profiling subsystem for measuring the range of a set of sample points on the surface of said object moving under said PLIIM based camera system; and
wherein said camera control computer uses said measured range of said set of sample points to compute the line rate compensation factor based on the slope (i.e. surface gradient) of said object surface measured with respect to the surface of the conveyor belt structure.
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13. The PLIIM based camera system of claim 8, wherein said PLIIM based camera system is supported along the side of a conveyor belt structure along which said object is transported;
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wherein said object range measurement subsystem comprises a laser-based object profiling subsystem for measuring the range of a set of sample points on the surface of said object moving past said PLIIM based camera system; and
wherein said camera control computer uses said measured range of said set of sample points to compute the line rate compensation factor based on the slope (i.e. surface gradient) of said object surface measured with respect to the edge of the conveyor belt structure.
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14. A planar laser illumination and imaging (PLIIM) based camera system for producing digital linear images of a moving object, while automatically compensating said digital linear images for viewing-angle distortion occurring therein as a result of said PLIIM based camera system illuminating and imaging object surfaces having a non-zero slope (i.e. surface gradient) characteristics, said PLIIM based camera system having a working range and comprising:
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a system housing of unitary construction having a first light transmission aperture, a second light transmission aperture, and a third light transmission aperture, wherein said first and second light transmission apertures are spatially aligned with each other, and said third light transmission aperture is disposed at a predetermined distance away from said first and second light transmission apertures;
a planar laser illumination and imaging (PLIIM) based linear imaging subsystem mounted within said system housing and having a planar laser illumination array (PLIA) including a plurality of laser diodes for producing and projecting a planar laser illumination beam (PLIB) through said first light transmission aperture, so as to illuminate an object as the object is moving past said PLIIM based camera system, and an image formation and detection (IFD) module having a linear image detection array with an adjustable line rate, and imaging forming optics for providing said linear image detection array with a field of view (FOV) which is projected through said second light transmission aperture, and along which digital linear images of illuminated portions of said object can be detected, wherein said PLIB and FOV are arranged in a coplanar relationship along the working range of said PLIIM based camera system so that the PLIB illuminates primarily within said FOV of the IFD module;
a laser-based object range measurement subsystem mounted within said system housing, for producing an amplitude modulated (AM) laser scanning beam which is projected through said third light transmission aperture so as to scan the surface of said transported object and determine the range thereof and generate object range data indicative of the determined range of the object;
a camera control computer, mounted within said system housing, for controlling the operation of said linear PLIIM-based linear imaging subsystem, including the line rate of said linear image detection array in response to object range data generated by said laser-based object range measurement subsystem, wherein said camera control computer (1) uses said object range data to compute a line rate compensation factor based on slope characteristics of the illuminated and imaged object surface;
(2) uses said computed line rate compensation factor to compute an adjusted line rate for said linear image detection array; and
(3) use the computed adjusted line rate parameter to adjust the line rate of said linear image detection array, so as to automatically compensate said digital linear images for viewing-angle distortion occurring therein as a result of said PLIIM based camera system illuminating and imaging object surfaces having a non-zero slope (i.e. surface gradient) characteristics. - View Dependent Claims (15, 16, 17)
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Specification