WO2002068900A2

WO2002068900A2 - Markless trigger

Info

Publication number: WO2002068900A2
Application number: PCT/US2002/006400
Authority: WO
Inventors: Mohanan Unni; German Linares
Original assignee: FORMSCAN Inc
Current assignee: FORMSCAN Inc
Priority date: 2001-02-28
Filing date: 2002-02-28
Publication date: 2002-09-06
Anticipated expiration: 2003-08-28
Also published as: WO2002068900A3; AU2002248520A1

Abstract

A method and apparatus (10) for providing a markless trigger in an object being manufactured, processed, conveyed, and the like. The markless trigger system has a transmissive sensor (16) suitable for detecting holes (17) in a sheet of paper. There is an encoder (18) suitable for generating position and velocity information of the sheet of paper (14). A quadrature detector (20) is in communication with the encoder, and a counter (24) is provided for tracking paper position. The method includes receiving encoder direction and pulse information at a counter, the encoder direction and pulse information relating to a position of an object. Object length information is received at the counter. Top-of-form hole detection is activated upon comparison of the encoder direction and pulse information and the object length information. A determination is made as to whether a top-of-form hole is detected. If a top-of-form hole is detected, the markless trigger is inserted based on the top-of-form hole detection. If a top-of-form hole is not detected, an artificial markless trigger is inserted. The system then looks ahead to anticipate the next location for detection of the top-of-form hole.

Description

MARKLESS TRIGGER

RELATED APPLICATION

This application claims priority to co-pending United States Provisional Application No. 60/272,351, filed February 28, 2001, for all subject matter common to both applications. The disclosure of said provisional application is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a machine vision position indicator, and more particularly relates to a method and apparatus for locating and tracking the relative position of continuous streams of paper sheets without use of markings on the paper.

BACKGROUND OF THE INVENTION

Machine vision relates to an automated examination of an item or image to determine certain characteristics. Machine vision technology is often found in manufacturing plants to check the position, arrangement, quality, and status of objects.

Machine vision, or computerized vision, systems are useful in the printing, mailing, and finishing industries. The systems can be Windows NT® based, and utilize digital cameras and/or scanners to read specific information from the objects, such as documents, during the printing or finishing process to ensure that the documents are printed, collated, matched, and mailed correctly.

There is most often a need, in machine vision systems, to provide one or more targets or triggers in the form of marks on the objects being viewed by the system in order for the system to calibrate the orientation and position of the object with respect to the features being viewed. The system first looks for the triggers or marks in order to position the object in a specific location. Once properly positioned based on the mark or marks, the system proceeds with whatever process or analysis required for the particular manufacturing step. These triggers, or marks, are often in the form of dots, bulls-eyes, parallel strips, cross-shaped symbols, and the like. If there is a problem with the mark, i.e., the mark is improperly formed, the mark is fuzzy or blurred, the mark is partially incomplete, and the like, the machine vision system can have difficulty in finding the mark, and thus difficulty in completing required tasks.

There is sometimes a desire or need for the machine vision system to be able to operate without the use of marks on the objects being viewed. The desire for no marks can stem from, e.g., aesthetic reasons (if a machine vision mark on an object would be aesthetically undesirable), from functional reasons (the mark will hinder or prevent proper performance of the object), or from implementation issues (the surface of the object is not suitable for maintaining a mark, the mark is not reliably consistent).

SUMMARY OF THE INVENTION

There exists in the art a need for a markless trigger that works in conjunction with a machine vision system to calibrate and position objects being viewed. The present invention is directed toward further solutions.

In accordance with one example embodiment of the present invention, a markless trigger system has a transmissive sensor suitable for detecting holes in a sheet of paper, however the sensor can be of any number of types, including reflective, magnetic, and the like. There is an encoder suitable for generating position and velocity information of the sheet of paper. A quadrature detector is in communication with the encoder, and a counter is provided for tracking paper position.

In accordance with another embodiment of the present invention, a markless trigger system includes a transmissive sensor suitable for detecting holes in an object. An encoder suitable for generating position and velocity information of the object is further provided. A quadrature detector is provided in communication with the encoder.

A counter for tracks object position. In accordance with certain aspects of the present invention, the object is a sheet of paper. The transmissive sensor is a reflective sensor and/or a magnetic sensor.

In accordance with further aspects of the present invention, the encoder combines information from the transmissive sensor and the position and velocity information. In addition, the quadrature detector receives information from the counter relating to the object position.

In accordance with one embodiment of the present invention, the counter is a 16- bit counter mechanism.

The markless trigger system can further include an image capture mechanism for viewing the object.

In accordance with another embodiment of the present invention, a method of generating a markless trigger is provided. The method includes receiving encoder direction and pulse information at a counter, the encoder direction and pulse information relating to a position of an object. Object length information is received at the counter. Top-of-form hole detection is activated upon comparison of the encoder direction and pulse information and the object length information. A determination is made as to whether a top-of-form hole is detected. If a top-of-form hole is detected, the markless trigger is inserted based on the top-of-form hole detection. If a top-of-form hole is not detected, an artificial markless trigger is inserted.

In accordance with one embodiment of the present invention, position of the object information and velocity of the object information enter a quadrature detector. The quadrature detector can emit the direction and pulse information.

In accordance with still another embodiment of the present invention, the counter tracks the position of the object. In accordance with yet another embodiment of the present invention, the step of determining includes processing encoder direction information, encoder pulse information, hole space counter information, and hole search space register information to determine a manner by which the markless trigger should be inserted.

In accordance with another embodiment of the present invention, the method further includes the system pausing as a full length of the object passes. The system then looks for a next top-of-form hole. The system then generates another markless trigger at the next top-of-form hole, the markelss trigger being based on the detection of another top-of-form hole.

In accordance with another embodiment of the present invention, the system looks one object length later for a third top-of-form whole.

In accordance with still another embodiment of the present invention, in an electronic device, a method of generating a markless trigger is provided. The method includes receiving encoder direction and pulse information at a counter, the encoder direction and pulse information relating to a position of an object. Object length information is received at the counter. Top-of-form hole detection is activated upon comparison of the encoder direction and pulse information and the object length information. A determination is made as to whether a top-of-form hole is detected. If a top-of-form hole is detected, the markless trigger is inserted based on the top-of-form hole detection. If no top-of-form hole is detected, an artificial markless trigger is inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned features and advantages, and other features and aspects of the present invention, will become better understood with regard to the following description and accompanying drawings, wherein:

FIG. 1 is a diagrammatic illustration of a machine vision system according to one aspect of the present invention; FIG. 2 is a block diagram of a quadrature detector according to one aspect of the present invention; FIG. 3 is a block diagram of a markless trigger system according to one aspect of the present invention; FIG. 4 is a flowchart showing an example determination of a markless trigger according to one aspect of the present invention; and FIG. 5 is a flowchart showing a further example determination following the process of FIG. 4 according to one aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to a markless trigger machine vision system. The markless trigger system generates a top-of-form signal in a web-based paper process where a conventional trigger mark is not reliably or consistently available. The markless trigger system uses the top-of-form signal in conjunction with an encoder to synchronize and clock the print inspection hardware. A quadrature detector processes signals from an encoder, which provides paper position and velocity. Top-of-form holes provide a trigger enable signal. Once there is a first trigger, the system pauses as the entire length of a sheet of paper passes before the system again looks for the next top-of- form hole. The encoder counts the page lengths. Once the page-length passes, the system looks for the next top-of-form hole. The system then generates another trigger at the next top-of-form hole. If the system does not detect another top-of-form hole, the system generates an artificial trigger. The system then automatically looks one page length later for the next top-of-form whole, adjusted for position errors. FIGS. 1 through 5, wherein like parts are designated by like reference numerals throughout, illustrate an example embodiment of a markless trigger system according to the present invention. Although the present invention will be described with reference to the example embodiments illustrated in the figures, it should be understood that many alternative forms can embody the present invention. One of ordinary skill in the art will additionally appreciate different ways to alter the parameters of the embodiments disclosed, such as the size, shape, or type of elements or materials, in a manner still in keeping with the spirit and scope of the present invention.

FIG. 1 illustrates a basic machine vision system 10. There is an image capture device 12 that looks at an object paper sheet 14 containing one or more images 15. Image capture device 12 can respond within the visual spectrum, e.g., a video or digital camera or scanner, it can also respond to emissions in other spectra, such as infrared, gamma ray, and the like. The object can be a paper sheet 14, as in the illustrated embodiment, or can be any object being processed, manufactured, conveyed, and the like, that requires some form of visual quantification.

The paper sheet 14 passes by the area observed by the image capture device 12, while a transmissive sensor 16 searches for a top-of-form hole 17 at a predetermined location along a side perforation of the paper sheet 14. The transmissive sensor 16 communicates the sighting of a top-of-form hole 17 to an encoder 18 which combines the transmissive sensor 16 information with position and velocity information from the paper sheet 14 and transmits everything to a central processing unit 22 containing a quadrature detector 20. The transmissive sensor 16, as previously mentioned, can utilize a number of different sensing technologies, including but not limited to a reflective or magnetic sensor as understood by one of ordinary skill in the art.

The quadrature detector 20 also receives input from a 16-bit counter 24 that tracks the amount of paper sheet 14 passing by the counter 24. The quadrature detector 20 takes the information of a trigger, (the sighting of a top-of-form hole 17 from the transmissive sensor 16) with the position and velocity information from the encoder 18, and the amount of paper sheet 14 passing by the counter 24 to anticipate where and when the next top-of-form hole 17 is to occur. Once the paper sheet 14 travels the requisite distance, the central processing unit 22 instructs the image capture device 12 to scan for another top-of-form hole 17.

If the image capture device 12 does not find another top-of-form hole 17, the machine vision system 10 insets an artificial trigger to compensate for the missing top- of-form hole 17. Whenever an artificial trigger is inserted, the next trigger is adjusted to compensate for positional errors. The subsequent triggers are then expected to originate from the transmissive sensor 16.

FIG. 2 illustrates a block diagram of the quadrature detector 20. The two phases of the encoder 18 (the position 28 and the velocity 30 of the paper sheet 14) enter the quadrature detector 20. The quadrature detector 20 then emits a pulse 32 corresponding to the velocity of the paper sheet 14 (see FIG. 1) and a travel direction indication 34 of the paper sheet 14. The 16-bit counter 24 (see FIG. 1) then tracks the position of the paper sheet 14 based on the pulses from the quadrature detector 20 so that the system 10 can implement artificial triggers as previously described.

FIG. 3 illustrates a block diagram of the process the markless trigger system 10 goes through in generating a markless trigger. The encoder direction indication 34 and the encoder pulses 32 are supplied to the 16-bit counter 24, which feeds to a 16-bit comparator 36. There is also page length register 38 information feeding to the comparator 36. The top-of-form hole 17 detection is in communication with the image capture device 12, which controls activation of the top-of-form hole 17. The system 10 can insert a trigger based either on a real detection of a top-of-form hole 17 or on a collection of information indicating the requirement for an artificial trigger insertion. The information includes the encoder direction 34 and pulses 32, data from a hole space counter 39, and a hole search space register 40.

FIG. 4 illustrates a flowchart of one example process the markless trigger system

10 executes in generating a markless trigger. This flowchart should be viewed in conjunction with the previously described block diagram of FIG. 3. The encoder direction indication 34 and the encoder pulses 32 enter the 16-bit counter 24 (step 100), which feeds to a 16-bit comparator 36 (step 102). Page length register 38 information also feeds into the comparator 36 (step 104). After a full page length passes by, the system 10 activates the top-of-form hole 17 detection through use of the image capture device 12 (step 106). The system 10 determines whether to insert a trigger based either on a real detection of a top-of-form hole 17 or on a collection of information indicating the requirement for an artificial trigger insertion (step 108). If there is a real detection of the top-of-form hole 17, the system 10 inserts a trigger based on the real detection (step 110). If there is an indication that an artificial trigger insertion is required, the system 10 inserts a trigger based on the supplied information (step 112). The information includes the encoder direction 34 and pulses 32, data from a hole space counter 39, and a hole search space register 40.

FIG. 5 is a flowchart showing a continuation process from the step 110 based on real detection of the top-of-form hole 17 of FIG. 4. Once a markless trigger has been placed based on a real detection of the top-of-form hole 17, the markless trigger system 10 pauses as the entire length of the paper sheet 14 passes (step 114) before the system 10 again looks for the next top-of-form hole 17. The counter 24 counts the page lengths (step 116). Once one page-length passes, the system 10 looks for the next top-of-form hole 17 (step 118). The system 10 then determines whether the next top-of-form hole is detected (step 120). If the next top of form hole 17 is detected, the system 10 generates another markless trigger at the next top-of-form hole 17 (step 122). If the system 10 does not detect another top-of-form hole 17, the system 10 generates an artificial markless trigger (step 124). The system then automatically looks one page length later for the next top-of-form 17 hole (step 126), adjusted for position errors.

The present invention generally relates to a markless trigger machine vision system. The markless trigger system generates a top-of-form signal in a process where a conventional trigger mark is not reliably or consistently available. The markless trigger system uses the top-of-form signal in conjunction with an encoder to synchronize and clock the print inspection hardware. A quadrature detector processes signals from an encoder, which provides paper position and velocity. Top-of-form holes provide a trigger enable signal. Once there is a first trigger, the system pauses as the entire length of a sheet of paper passes before the system again looks for the next top-of-form hole. The encoder counts the page lengths. Once the page-length passes, the system looks for the next top-of-form hole. The system then generates another trigger at the next top-of- form hole. If the system does not detect another top-of-form hole, the system generates an artificial trigger. The system then automatically looks one page length later for the next top-of-form whole, adjusted for position errors.

Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode for carrying out the invention. Details of the structure may vary substantially without departing from the spirit of the invention, and exclusive use of all modifications that come within the scope of the appended claims is reserved. It is intended that the invention be limited only to the extent required by the appended claims and the applicable rules of law.

Claims

CLAIMSWhat is claimed is:

1. A markless trigger system, comprising: a transmissive sensor suitable for detecting holes in an object; an encoder suitable for generating position and velocity information of the object; a quadrature detector in communication with the encoder; and a counter for tracking obj ect position.

2. The markless trigger system of claim 1, wherein the object is a sheet of paper.

3. The markless trigger system of claim 1, wherein the transmissive sensor is at least one of a reflective sensor and a magnetic sensor.

4. The markless trigger system of claim 1, wherein the encoder combines information from the transmissive sensor and the position and velocity information.

5. The markless trigger system of claim 1, wherein the quadrature detector receives information from the counter relating to the object position.

6. The markless trigger system of claim 1, wherein the counter comprises a 16-bit counter mechanism.

7. The markless trigger system of claim 1, further comprising an image capture mechanism for viewing the object.

8. A method of generating a markless trigger, comprising: receiving encoder direction and pulse information at a counter, the encoder direction and pulse information relating to a position of an object; receiving object length information at the counter; activating top-of-form hole detection upon comparison of the encoder direction and pulse information and the object length information; determining whether a top-of-form hole is detected; and one of inserting the markless trigger based on a top-of-form hole detection and inserting an artificial markless trigger.

9. The method of claim 8, further comprising position of the object information and velocity of the object information entering a quadrature detector.

10. The method of claim 9, further comprising the quadrature detector emitting the direction and pulse information.

11. The method of claim 8, further comprising the counter tracking the position of the object.

12. The method of claim 8, wherein determining comprises processing encoder direction information, encoder pulse information, hole space counter information, and hole search space register information.

13. The method of claim 8, further comprising the system pausing as a full length of the object passes.

14. The method of claim 13, further comprising the system looking for a next top-of- form hole.

15. The method of claim 14, further comprising the system then generating another markless trigger at the next top-of-form hole, the markelss trigger being based on the detection of another top-of-form hole.

16. The method of claim 15, further comprising the system looking one object length later for a third top-of-form whole.

17. In an electronic device, a method of generating a markless trigger, the method comprising: receiving encoder direction and pulse information at a counter, the encoder direction and pulse information relating to a position of an object; receiving object length information at the counter; activating top-of-form hole detection upon comparison of the encoder direction and pulse information and the object length information; determining whether a top-of-form hole is detected; and one of inserting the markless trigger based on a top-of-form hole detection and inserting an artificial markless trigger.

18. The method of claim 17, further comprising position of the object information and velocity of the object information entering a quadrature detector.

19. The method of claim 18, further comprising the quadrature detector emitting the direction and pulse information.

20. The method of claim 17, further comprising the counter tracking the position of the object.

21. The method of claim 17, wherein determining comprises processing encoder direction information, encoder pulse information, hole space counter information, and hole search space register information.

22. The method of claim 17, further comprising the system pausing as a full length of the object passes.

23. The method of claim 22, further comprising the system looking for a next top-of- form hole.

24. The method of claim 23, further comprising the system then generating another markless trigger at the next top-of-form hole, the markelss trigger being based on the detection of another top-of-form hole.

25. The method of claim 24, further comprising the system looking one object length later for a third top-of-form whole.