Method of and system for automatically producing digital images of a moving object, with pixels having a substantially uniform white level independent of the velocity of said moving object

• US 6,971,577 B2
• Filed: 05/23/2002
• Issued: 12/06/2005
• Est. Priority Date: 03/24/1998
• 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., Wirth, Allan
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US10/155,902
• Publication Number:
  US 20030089778A1
• Time in Patent Office: 1,293 Days
• Field of Search: 23546201-46248, 235/472.01, 235/472.02, 235/472.03, 235/470, 235/454, 235/455, 235/494, 235/462, 235/472
• 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

A method of and apparatus for automatically producing digital images of an object having a substantially uniform white level independent of the velocity of the object. The method comprising determining the velocity of an object moving relative to a planar light illumination and imaging (PLIIM) based imaging system having a linear image detection array with a field of view (FOV), a planar light illumination array (PLIA) with a plurality of light emitting diodes (LEDs) arranged in a linear array for producing a planar light illumination beam (PLIB) coplanar with the FOV, and a micro-controller for controlling the operation of the PLIIM based imaging system. The determined velocity is used to compute the optical power which each light emitting diode (LED) must produce in order that each digital image of the object, formed by illuminating the object with the computed optical power, will have substantially the same white intensity level independent of the velocity of the object relative to the PLIIM-based imaging system. The computed optical power value(s) are transmitted to the micro-controller, and the micro-controller uses the computed optical power value(s) to drive each light emitting diode so that it produces a planar light illumination beam having the computed optical power level with the FOV. By virtue of the present invention, the planar light illumination beam illuminates the object, and the PLIIM-based imaging system automatically produces a digital image of the moving object, with pixels having a substantially uniform white level, independent of the velocity of the object. Such image characteristics enables simpler and more reliable image processing in applications such as, for example, optical character recognition (OCR) processing, where image pixels having a substantially uniform white level, and a uniform aspect-ratio, are often desired or required.

Claims

1. A method of automatically producing digital linear images of a moving object, containing pixels having a substantially square aspect-ratio, independent of the range and/or velocity of the moving object, said method comprising the steps of:

a) determining the range of an object moving relative to a planar light illumination and imaging (PLIIM) based linear imaging system;

b) determining the velocity of said object moving relative to said PLIIM based linear imaging system having

a linear image detection array with a field of view (FOV) projectable onto the moving object,

a planar light illumination array (PLIA) for producing a planar light illumination beam (PLIB) coplanar within the FOV of said linear image detection array, and

a micro-controller for controlling the operation of the PLIIM based linear imaging system;

c) using the range and velocity parameters determined in steps (a) and (b) respectively, to determine a photo-integration time period parameter for the linear image detection array which ensures that said PLIIM based linear imaging system produces digital linear images of said moving object, containing pixels having a substantially square (i.e. 1;

1) aspect-ratio, independent of the measured object range and/or velocity; and

d) using said photo-integration time period determined in step (c) to control the photo-integration time period of the linear image detection array of said PLIIM based linear imaging system;

whereby the PLIB illuminates said object as said object moves through said FOV, and said linear image detection array automatically produces digital linear images of the moving object, containing pixels having a substantially square aspect-ratio, independent of the measured range and/or velocity of the moving object.

2. The method of claim 1, wherein step (a) comprises illuminating said moving object with a pair of amplitude-modulated (AM) laser beams, capturing a pair of images of said moving object, and processing said pair of images so as to determine the range and velocity of said moving object.

3. The method of claim 2, wherein step (c) comprises determining said photo-integration time period parameter by using a lookup table containing precomputed photo-integration time period parameters indexed by object velocity and range parameter values.

4. The method of claim 1, wherein step (a) comprises determining the range and velocity of the object transported relative to said PLIIM based linear imaging system supported above a conveyor belt structure, along which the object is transported during object illumination and imaging operations.

5. The method of claim 1, wherein step (a) comprises detecting the range and velocity of the object transported relative to said PLIIM based linear imaging system embodied within a hand-supportable housing, past which the object is moved during object illumination and imaging operations.

6. A planar light illumination and imaging (PLIIM) based camera system for producing digital linear images of a moving object, containing pixels having a substantially square aspect-ratio independent of the velocity and/or distance of the moving object, said PLIIM based camera system having a working range and comprising:

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 respect to each other;

a PLIIM-based linear imaging subsystem mounted within said system housing and having

a planar light illumination array (PLIA) for producing and projecting a planar light illumination beam (PLIB) through said first light transmission aperture, so as to illuminate an object as it is moving past said PLIIM based camera system, and

an image formation and detection (IFD) module having a linear image detection array 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 linear images of illuminated portions of said object can be detected,

wherein said PUB and FOV are arranged in a coplanar relationship along the working range of said PLIIM based camera system so that the PUB illuminates primarily within said FOV of the IFD module;

an object range and velocity measurement subsystem for projecting and scanning a light beam along the surface of said object, receiving light reflected from said object, generating electrical signals representative to a characteristics of said received light, processing said electrical signals to determine the range and velocity thereof relative to the PLIIM-based camera system and generating object range and velocity data indicative of the determined range and velocity of the moving object;

a camera control computer, mounted within said system housing, for controlling the operation of said linear PLIIM-based imaging subsystem, in response to object range and velocity data generated by said object range and velocity measurement subsystem,

wherein said camera control computer

(1) uses said object range and velocity data to determine a photo-integration time period parameter for the linear image detection array which produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio, independent of range and/or velocity of said moving object, and

(2) uses said determined photo-integration time period parameter to control the operation of said linear image detection array so that said linear image detection array automatically produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio independent of the measured range and/or velocity of the moving object.

7. The PLIIM based camera system of claim 6, wherein said system housing is supported above a conveyor belt structure, along which the object is transported during object illumination and imaging operations.

8. The PLIIM based camera system of claim 6, wherein said system housing is realized as a hand-supportable housing, past which the object is moved during object illumination and imaging operations.

9. planar light illumination and imaging (PLIIM) camera system for producing digital linear images of a moving object, containing pixels having a substantially square aspect-ratio independent of the velocity and/or distance of the moving object, said PLIIM based camera system having a working range and comprising:

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 respect to each other, and said third light transmission aperture is disposed at a predetermined distance away from said first and second light transmission apertures;

a PLIIM-based linear imaging subsystem mounted within said system housing and having

a planar light illumination array (PLIA) for producing and projecting a planar light illumination beam (PLIB) through said first light transmission aperture;

so as to illuminate an object as it is moving past said PLIIM based camera system, and

an image formation and detection (IFD) module having a linear image detection array 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 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 LED module;

a light scanning object range and velocity measurement subsystem mounted within said system housing, for producing a pair of amplitude modulated (AM) laser scanning beams which are projected through said third light transmission aperture so as to scan the surface of said transported object and determine the range and velocity thereof and generate object range and velocity data indicative of the determined range and velocity of the object, respectively;

a camera control computer, mounted within said system housing, for controlling the operation of said linear PLIIM-based linear imaging subsystem, in response to object range and velocity data generated by said light scanning object range and velocity measurement subsystem,

wherein said camera control computer

(1) uses said object range and velocity data to determine a photo-integration time period parameter for the linear image detection array which produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio, independent of range and/or velocity of said moving object; and

(2) uses said determined photo-integration time period parameter to control the operation of said linear image detection array so that said linear image detection array automatically produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio independent of the measured range and/or velocity of the moving object.

10. The PLIIM based camera system of claim 9, wherein said system housing is supported above a conveyor belt structure, along which the object is transported during object illumination and imaging operations.

11. The PLIIM based camera system of claim 9, wherein said system housing is realized as a hand-supportable housing, past which the object is moved during object illumination and imaging operations.

12. A planar light illumination and imaging (PLIIM) based camera system for automatically producing digital linear images of a moving object containing pixels having a substantially square aspect-ratio independent of the velocity and/or distance of the moving object, said PLIIM based camera system comprising:

a linear image detection array with a field of view (FOV) projectable onto the moving object;

a planar light illumination array (PLIA) for producing a planar light illumination beam (PLIB) coplanar with the FOV of said linear image detection array;

an object range and velocity and distance measurement subsystem for automatically measuring the range and velocity of the moving object, and generating object range and velocity data indicative of the determined range and velocity of the moving object, respectively;

a micro-controller for controlling the operation of the linear image detection array and said PLIA, and carrying out the following control operations;

(1) using said object range and velocity data to determine a photo-integration time period parameter for the linear image detection array which produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio, independent of range and/or velocity of said moving object; and

(2) using said determined photo-integration time period parameter to control the operation of said linear image detection array so that said linear image detection array produces digital linear images of said moving object, containing pixels having a substantially square aspect-ratio independent of the measured range and/or velocity of the moving object;

whereby the PLIB illuminates said object as said object moves through said FOV, and said linear image detection array automatically produces digital linear images of the moving object, containing pixels having a substantially square aspect-ratio, independent of the range and/or velocity of the moving object.

13. The PLIIM based camera system of claim 12, supported above a conveyor belt structure, along which the object is transported during object illumination and imaging operations.

14. The PLIIM based system of claim 12, embodied within a band-supportable housing, past which the object is moved during object illumination and imaging operations.