Led-based planar light illumination and imaging (PLIIM) based camera system employing real-time object coordinate acquisition and producing to control automatic zoom and focus imaging optics

• US 6,877,662 B2
• Filed: 05/23/2002
• Issued: 04/12/2005
• 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, Good, Timothy A., Knowles, C. Harry, Au, Ka Man, Ghosh, Sankar, Amundsen, Thomas, Schnee, Michael D., Tsikos, Constantine J.
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US10/155,803
• Publication Number:
  US 20030071128A1
• Time in Patent Office: 1,055 Days
• Field of Search: 23546201-46245, 235/472.01, 235/472.02, 235/472.03, 235/454, 235/455, 235/494, 235/470, 235/375
• US Class Current: 235/462.01
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0052 the light source comprising a laser diode coupling into light guides using intermediate optical elements G02B6/4204; semiconductor lasers having optical devices external to the laser cavity H01S5/005
• CPC Class Codes: G02B 19/0085 for use with both a detector and a source , e.g. in a transceiver, G02B19/009, G02B19/0095 take precedence
• CPC Class Codes: G02B 19/009 for use with infrared radiation
• CPC Class Codes: G02B 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 27/095 Refractive optical elements
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: G06K 7/10594 Beam path
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/146 the method including quality enhancement steps
• CPC Class Codes: G06Q 10/00 Administration; Management
• CPC Class Codes: G06Q 30/00 Commerce
• CPC Class Codes: G06V 20/62 Text, e.g. of license plates, overlay texts or captions on TV images
• CPC Class Codes: G06V 30/144 using a slot moved over the image; using discrete sensing elements at predetermined points; using automatic curve following means
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

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.

Claims

1. An automatic image-based object identification system for automatically identifying objects transported along a conveyor belt structure, said automatic image-based object identification system comprising:

an object dimensioning subsystem for dimensioning each said object transported along a conveyor belt structure beneath said object dimensioning subsystem, and producing object dimension data representative of the spatial dimensions of said object with respect to a coordinate reference system; and

an image-based object identification subsystem mounted above said conveyor belt structure, and having

(i) a linear image formation and detection subsystem having image formation optics with a field of view with variable zoom and variable focus characteristics, for producing linear images of objects as said objects are transported along said conveyor belt structure and beneath said image-based object identification subsystem during object illumination and imaging operations, and

(ii) a pair of planar light illumination arrays (PLIAs) arranged about said linear image formation and detection subsystem, each said planar light array (PLIA) including a plurality of light emitting diodes (LEDs) arranged together in a linear manner and said PLIAs being arranged in relation to said linear image formation and detection subsystem, for producing a pair of planar light illumination beams (PLIBs), and projecting said pair of PLIBs so that the plane of said PLIBs is coplanar with the field of view of said linear image formation and detection subsystem so that the object can be simultaneously illuminated by said PLIBs and imaged within said field of view of said linear image formation and detection subsystem; and

a camera control computer operably connected to said linear image formation and detection subsystem and said object dimensioning subsystem, and receiving said object dimension data from said object dimensioning subsystem and producing zoom and focus control signals for automatically controlling the variable zoom and variable focus characteristics of said linear image formation and detection subsystem as said object is transported beneath said image-based object identification subsystem;

whereby a series of linear images of said object are sequentially detected by said linear image formation and detection subsystem as said object moves past said automatic image-based object identification system so that said series of linear images can be grabbed and buffered for subsequent use in constructing two-dimensional images of said object.

2. The automatic image-based object identification system of claim 1, which further comprises:

an image frame grabber for grabbing images formed and detected by said linear image formation and detection subsystem,

an image data buffer for buffering said grabbed linear images; and

an image processing computer operably associated with said image data buffer, for processing said buffered linear images.

3. The automatic image-based object identification system of claim 1, wherein said image formation optics has a variable focal distance and a variable focal length providing a variable field of view.

4. The automatic image-based object identification system of claim 1, wherein said object dimensioning subsystem comprises a LADAR-based object dimensioning subsystem having means for producing an amplitude modulated (AM) laser scanning beam for scanning the surface of each said object as said object is transported under said image-based object identification subsystem.

5. The automatic image-based object identification system of claim 1, wherein said coordinate reference system is a global coordinate reference system symbolically embedded within the structure of said object dimensioning subsystem.

6. The automatic image-based object identification system of claim 1, wherein said object dimension data comprises object height, width, and length coordinate data.

7. The automatic image-based object identification system of claim 1, wherein said image-based object identification subsystem further comprises a object velocity mechanism for measuring the velocity of each said object as said object is transported beneath said image-based object identification subsystem and producing object velocity data that is provided to said camera control computer.

8. The automatic image-based object identification system of claim 7, wherein said object velocity mechanism is integrated within said object dimensioning subsystem.

9. The automatic image-based object identification system of claim 1, wherein said object dimensioning subsystem is integrated with said image-based object identification subsystem within a system housing of substantially unitary construction.

10. A method of automatically identifying objects transported along a conveyor belt structure, said method comprising the steps of:

(a) dimensioning on object transported along a conveyor belt structure, producing object dimension data representative of the spatial dimensions at said object with respect to a coordinate reference system, and transmitting said object dimension data along a data communication medium;

(b) using a linear image formation and detection subsystem having a field of view (FOV) with variable zoom and variable focus characteristics and mounted above said conveyor belt structure, to produce linear images of said object as said object is being transported along said conveyor belt structure;

(c) at said linear image formation and detection subsystem, receiving said object dimension data transmitted along said data communications medium, and producing zoom and focus control signals for automatically controlling the variable zoom and variable focus characteristics of said linear image formation and detection subsystem as said object is transported along said conveyor belt structure; and

(d) whereby said linear image formation and detection subsystem captures a sequence of linear images of said object, processes said sequence of linear images to recognize object identification indicia on the surface of said object, and thereby automatically identifies said transported object.

11. The method of claim 10, wherein said linear image formation and detection subsystem comprises a planar light illumination (PLIIM) based linear camera subsystem having a linear image detection array with said FOV.

12. The method or claim 10, wherein step (a) comprises producing an amplitude modulated (AM) laser scanning beam for scanning the surface of said object as said object is transported along said conveyor belt structure.

13. The method of claim 10, wherein said data communication medium comprises a local area network supporting the Ethernet networking protocol.

14. The method of claim 10, wherein said coordinate reference system is a global coordinate reference system symbolically embedded within the structure of said linear image formation and detection subsystem.

15. The method of claim 10, wherein said object dimension data comprises object height, width, and length coordinate data.

16. The method of claim 10, wherein step (a) further comprises measuring the velocity of each said object as said object is transported along said conveyor belt structure, and producing object velocity data that is transmitted along said communication medium.