Planar laser illumination and imaging (PLIIM) systems

• US 6,786,414 B2
• Filed: 01/28/2002
• Issued: 09/07/2004
• Est. Priority Date: 06/07/1999
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Zhu, Xiaoxun, Amundsen, Thomas, Naylor, Charles A., Knowles, Carl Harry, Schnee, Michael D., Tsikos, Constantine J., Dobbs, Russell Joseph
• Primary Examiner(s): Le, Thien M.
• Application Number:
  US10/059,047
• Publication Number:
  US 20030015587A1
• Time in Patent Office: 953 Days
• Field of Search: 235/462-1-4, 235/462-6-4, 235/454, 235/455, 235/472-1-4, 235/476
• US Class Current: 235/472.01
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G06K 7/10554 Moving beam scanning
• CPC Class Codes: G06K 7/10574 Multiple sources
• CPC Class Codes: G06K 7/10633 by oscillation
• CPC Class Codes: G06K 7/10683 Arrangement of fixed elements
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches

Abstract

A planar laser illumination and imaging system for illuminating an object and forming an image thereof. The planar laser illumination and imaging system which comprises an image formation and detection module having a field of view (FOV) focused at an image detecting array. A planar laser illumination array (PLIA) constructed from an plurality of planar laser illumination modules (PLIMs) is arranged in rectilinear manner. Each planar laser illumination module comprises a visible laser diode (VLD), a focusing lens, and a cylindrical optical element arranged therewith to produce a planar laser illumination beam component; and wherein the individual planar laser illumination beam components produced from the plurality of planar laser illumination modules are optically combined to produce a composite substantially planar laser illumination beam having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of the image formation and detection module, so that laser light reflected off an object illuminated by the planar laser illumination beam is focused along the field of view and onto the image detecting array to form an image of the illuminated object.

Claims

1. A planar laser illumination and imaging system for illuminating an object and forming an image thereof, said planar laser illumination and imaging system comprising:

an image formation and detection module having a field of view (FOV) focused at an image detecting array; and

a planar laser illumination array (PLIA) constructed from an plurality of planar laser illumination modules (PLIMs) arranged in rectilinear manner,

wherein each said PLIM comprises a visible laser diode (VLD), a focusing lens, and a cylindrical optical element arranged therewith to produce a planar laser illumination beam component; and

wherein said individual planar laser illumination beam components produced from said plurality of PLIMs are optically combined to produce a composite substantially planar laser illumination beam having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of said image formation and detection module, so that laser light reflected off an object illuminated by said composite substantially planar laser illumination beam is focused along said field of view and onto said image detecting array to form an image of said illuminated object.

2. The planar laser illumination and imaging system of claim 1, wherein said composite substantially planar laser illumination beam has substantially uniform power density characteristics over the entire spatial extent thereof and thus the working range of the system.

3. The planar laser illumination and imaging system of claim 1, wherein 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 said composite substantially planar laser illumination beam due to the fact that the width of said composite substantially planar laser illumination beam increases in length for increasing object distances away from the imaging optics.

4. The planar laser illumination and imaging system of claim 1, wherein said planar light illumination beam (PLIB) and the magnified field of view (FOV) are projected onto an object during conveyor-type illumination and imaging applications, and wherein the height dimension of the PLIB is substantially greater than the height dimension of the magnified field of view of each image detection element in said image detecting array so as to decrease the range of tolerance that must be maintained between the PLIB and the FOV.

5. The planar laser illumination and imaging system of claim 1, wherein said visible laser diodes are configured together along with a linear array of electronic image detection cells so as to produce said substantially planar beam of laser illumination which extends in substantially the same plane as the field of view of the linear array of electronic image detection cells, along at least a portion of its optical path within the working distance of said system.

6. The planar laser illumination and imaging system of claim 5, wherein said linear array of electronic image detection cells are realized using charge-coupled device (CCD) technology.

7. The planar laser illumination and imaging system of claim 1, wherein a fixed focal length imaging subsystem is employed, and a laser beam focusing technique is employed to compensate for decreases in the power density of the incident planar illumination beam due to the fact that the width of said composite substantially planar laser illumination beam increases with increasing distances away from said imaging subsystem.

8. The planar laser illumination and imaging system of claim 1, wherein the principle of Gaussian summation of light intensity distributions is employed to produce a planar laser illumination beam having a power density across the width the beam which is substantially the same for both far and near fields of the system.

9. A planar laser illumination and imaging (PLIIM) based system with automatic laser beam power density compensation, said PLIIM based system comprising:

an image formation and detection module having a field of view (FOV) focused at an image detecting array; and

a planar laser illumination array (PLIA) for producing a planar laser illumination beam (PLIB) having substantially-planar spatial distribution characteristics that extend through the field of view (FOV) of said image formation and detection module, so that laser light reflected off an object illuminated by said planar laser illumination beam is focused along said field of view and onto said image detecting array to form an image of said illuminated object;

wherein said planar laser illumination beam has a beam width which increases as a function of increasing object distance in said PLIIM based system; and

wherein the height of said planar laser illumination beam decreases as the object distance increases, compensating for the increase in beam width in said planar laser illumination beam which occurs for an increase in object distance,

thereby yielding a laser beam power density on the target object which increases as a function of increasing object distance over a substantial portion of the object distance range of said PLIIM based system.

10. The PLIIM based system of claim 9, wherein the beam height of said PLIB is substantially constant (e.g. 1 mm) over the entire portion of the object distance range of said PLIIM-based system.

11. A PLIIM based system having near and far field regions, comprising:

a planar laser illumination array (PLIA) having a plurality of visible laser diodes (VLDs),

wherein the power density contributions of the individual visible laser diodes in the planar laser illumination array are additively combined to produce a planar laser illumination beam (PLIB) having substantially uniform power density characteristics in the near and far field regions of the system.

12. A method of illuminating an object and forming an image thereof, comprising the steps of:

(a) providing a field of view (FOV) focused at an image detecting array within a system; and

(b) producing a planar laser illumination beam having substantially-planar spatial distribution characteristics that extend through said field of view (FOV) so that laser light reflected off an object illuminated by said planar laser illumination beam is focused along said field of view and onto said image detecting array to form an image of said illuminated object.

13. The method of claim 12, wherein said step (b) comprise:

producing a plurality of laser beams from a plurality of visible laser diodes (VLDs);

focusing each said laser beam through a focusing lens, and expanding the focused laser beam through a cylindrical optical element so as to produce a substantially planar laser illumination beam component; and

optically combining the plurality of planar laser illumination beam components produce a composite substantially planar laser illumination beam having substantially uniform power density characteristics over the entire spatial extent thereof and thus the working range of the system.

14. The method of claim 13, said FOV is provided by imaging optics, and wherein 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.