Method and apparatus for locating objects

• US 8,630,478 B2
• Filed: 09/20/2012
• Issued: 01/14/2014
• Est. Priority Date: 06/09/2004
• Status: Active Grant

• Current Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Original Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Inventors: Silver, William M.
• Primary Examiner(s): Rahmjoo, Mike
• Application Number:
  US13/623,387
• Publication Number:
  US 20130163847A1
• Time in Patent Office: 481 Days
• Field of Search: 382/141, 382/145, 382/153, 382/100, 382/209, 382/159, 382/190, 382/194, 382/195, 382/216, 382/217, 382/170, 382/155
• US Class Current: 382/141
• CPC Class Codes: G01N 2021/8909 Scan signal processing specially adapted for inspection of running sheets
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/0006 using a design-rule based approach
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06V 10/443 by matching or filtering

Abstract

Disclosed are methods and apparatus for automatic optoelectronic detection and inspection of objects, based on capturing digital images of a two-dimensional field of view in which an object to be detected or inspected may be located, analyzing the images, and making and reporting decisions on the status of the object. Decisions are based on evidence obtained from a plurality of images for which the object is located in the field of view, generally corresponding to a plurality of viewing perspectives. Evidence that an object is located in the field of view is used for detection, and evidence that the object satisfies appropriate inspection criteria is used for inspection. Methods and apparatus are disclosed for capturing and analyzing images at high speed so that multiple viewing perspectives can be obtained for objects in continuous motion.

Claims

1. A method for locating a plurality of objects, comprising:

using a conveyor having motion relative to a fixed mark point to transport each object of the plurality of objects so that the object passes the fixed mark point;

inputting a non-transitory encoding signal responsive to the motion of the conveyor, from which can be obtained at desired times a corresponding encoder count indicating a relative location of the conveyor;

determining, for each object of the plurality of objects, a corresponding mark count indicating the encoder count corresponding to a time when the object passes the fixed mark point, wherein

determining the corresponding mark count occurs at a corresponding decision point that differs from the time when the object passes the fixed mark point by a corresponding decision delay; and

the decision delays corresponding to the plurality of objects are variable;

producing, for each object of the plurality of objects, a corresponding non-transitory signal at a corresponding report time that occurs when the corresponding encoder count differs from the mark count by a delay count; and

using, for each object of the plurality of objects, the corresponding report time of the corresponding non-transitory signal to indicate a location of the object.

2. The method of claim 1, further comprising using a first-in first-out buffer to hold information needed for producing each corresponding non-transitory signal at each corresponding report time.

3. The method of claim 1, wherein the location of the object, at the corresponding report time, is a downstream position that is separated from the mark point by a distance determined by the delay count.

4. The method of claim 3, further comprising adjusting the delay count so that the downstream position corresponds to a desired location of the object.

5. The method of claim 4, wherein the desired location corresponds to an actuator location.

6. The method of claim 4, wherein adjusting the delay count is responsive to a human-machine interface.

7. The method of any of claims 1-6, further comprising using, for each object of the plurality of objects, the corresponding non-transitory signal to indicate that the object was detected.

8. A system for locating a plurality of objects, comprising:

a conveyor having motion relative to a fixed mark point that transports each object of the plurality of objects so that the object passes the fixed mark point;

an input device that receives an encoding non-transitory signal responsive to the motion of the conveyor, from which can be obtained at desired times a corresponding encoder count indicating a relative location of the conveyor;

an analyzer that determines, for each object of the plurality of objects, a corresponding mark count indicating the encoder count corresponding to a time when the object passes the fixed mark point, wherein

determining the corresponding mark count occurs at a corresponding decision point that differs from the time when the object passes the fixed mark point by a corresponding decision delay; and

the decision delays corresponding to the plurality of objects are variable; and

an output signaler that indicates, for each object of the plurality of objects, a location of the object by producing a corresponding non-transitory signal at a corresponding report time that occurs when the corresponding encoder count differs from the mark count by a delay count.

9. The system of claim 8, further comprising a first-in first-out buffer that holds information needed by the output signaler for producing each corresponding non-transitory signal at each corresponding report time.

10. The system of claim 8, wherein the location of the object, at the corresponding report time, is a downstream position that is separated from the mark point by a distance determined by the delay count.

11. The system of claim 10, further comprising a controller that adjusts the delay count so that the downstream position corresponds to a desired location of the object.

12. The system of claim 11, further comprising

an actuator having a location from which to act on each object;

and wherein

the desired location corresponds to the location of the actuator.

13. The system of claim 11, wherein the controller comprises a human-machine interface.