Method and system for optoelectronic detection and location of objects

• US 8,718,319 B2
• Filed: 06/15/2007
• Issued: 05/06/2014
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Silver, William M.
• Primary Examiner(s): Bali, Vikkram
• Application Number:
  US11/763,785
• Publication Number:
  US 20080310676A1
• Time in Patent Office: 2,517 Days
• Field of Search: 382/101, 382/103, 382/104, 382/107
• US Class Current: 382/103
• CPC Class Codes: G01V 8/00 Prospecting or detecting by optical means
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/0008 checking presence/absence
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: G06V 2201/06 Recognition of objects for industrial automation

Abstract

Optoelectronic detection and location of moving objects is performed to capture one-dimensional images of a field of view through which objects may be moving, make measurements in those images, select from among those measurements those that are likely to correspond to objects in the field of view, make decisions responsive to various characteristics of the objects, and produce signals that indicate those decisions.

Claims

1. A system for locating an object, comprising:

an optical sensor configured to make light measurements in a field of view to capture a plurality of one-dimensional images;

means for providing relative motion between the object and the optical sensor;

such that

the object passes through the field of view; and

the object crosses a reference position at a reference time;

a processor that determines an estimate of the reference time by predicting the reference time based upon values associated with the plurality of one-dimensional images; and

means for producing a signal at a time that is responsive to the estimate of the reference time.

2. The system of claim 1 wherein the field of view is oriented substantially parallel to a direction of motion of the object.

3. The system of claim 1 wherein the optical sensor comprises a linear array of photoreceptors oriented substantially parallel to a direction of motion of the object.

4. The system of claim 1 wherein the plurality of one-dimensional images comprises a plurality of perspectives of a slice of the object.

5. A system for locating an object, comprising:

an optical sensor capable of making light measurements in a field of view;

a conveyor that provides relative motion between the object and the optical sensor, such that

the object passes through the field of view;

the field of view is oriented substantially parallel to a direction of motion of the object; and

the object crosses a reference position at a reference time;

a processor that determines an estimate of the reference time; and

means for using the estimate of the reference time to produce a signal at a signal time, wherein there is no latency between the reference time and the signal time.

6. The system of claim 5 wherein the optical sensor captures one-dimensional images in the field of view.

7. The system of claim 6 wherein the one-dimensional images comprise a plurality of perspectives of a slice of the object.

8. The system of claim 5 wherein the optical sensor comprises a linear array of photoreceptors such that the field of view of the linear array is oriented substantially parallel to the direction of motion of the object.

9. A method for locating an object, comprising:

using an optical sensor to make light measurements in a field of view;

providing relative motion between the object and the optical sensor in a direction of motion, wherein

the object passes through the field of view;

the field of view is oriented substantially parallel to the direction of motion; and

the object crosses a reference position at a reference time;

determining an estimate of the reference time by predicting the reference time; and

producing a signal at a time that is responsive to the estimate of the reference time.

10. The method of claim 9 further comprising capturing, with the optical sensor, a plurality of one-dimensional images, the plurality of one-dimensional images respectively having three values including two image measurements and a capture time, and wherein the values for the plurality of one-dimensional images are plotted along a best-fit line and the estimate of the reference time is determined by the best-fit line.

11. The method of claim 9 wherein the step of determining the estimate of the reference time employs normal correlation to produce scores and a position and judge a level of confidence as to whether an object is present in the field of view.

12. The method of claim 9 further comprising capturing, with the optical sensor, a plurality of images of the object to obtain a plurality of perspectives of a slice of the object.

13. The method of claim 9 wherein the step of producing the signal at the time that is responsive to the estimate of the reference time has the following conditions:

(a) no signal has already been scheduled;

(b) a crossed flag indicates that the object has actually crossed the reference point; and

(c) a good points counter indicates that a level of confidence indicates that the object is present in the field of view.

14. A method for locating an object, comprising:

using an optical sensor to make light measurements in a field of view to capture a plurality of one-dimensional images;

providing relative motion between the object and the optical sensor in a direction of motion, wherein

the object passes through the field of view; and

the object crosses a reference position at a reference time;

determining an estimate of the reference time based upon values associated with the plurality of one-dimensional images; and

using the estimate of the reference time to produce a signal at a signal time, wherein there is no latency between the reference time and the signal time.

15. The method of claim 14 wherein the field of view is oriented substantially parallel to the direction of motion such that the optical sensor makes light measurements substantially parallel to the direction of motion.

16. The method of claim 14 further comprising capturing, with the optical sensor, a plurality of one-dimensional images, the plurality of one-dimensional images respectively having three values including two image measurements and a capture time, and wherein the values for the plurality of one-dimensional images are plotted along a best-fit line and the estimate of the reference time is determined by the best-fit line.

17. The method of claim 14 wherein the step of determining the estimate of the reference time employs normal correlation to produce scores and a position and judge a level of confidence as to whether an object is present in the field of view.

18. The method of claim 14 further comprising capturing, with the optical sensor, a plurality of images of the object to obtain a plurality of perspectives of a slice of the object.

19. The method of claim 14 wherein the step of producing the signal at the time that is responsive to the estimate of the reference time has the following conditions:

(a) no signal has already been scheduled;

(b) a crossed flag indicates that the object has actually crossed the reference point; and

(c) a good points counter indicates that a level of confidence indicates that the object is present in the field of view.