Object tracking system for monitoring a controlled space

• US 5,973,732 A
• Filed: 02/19/1997
• Issued: 10/26/1999
• Est. Priority Date: 02/19/1997
• Status: Expired due to Term

• Current Assignee: Shoppertrak RCT Corporation (Johnson Controls International plc)
• Original Assignee: Quadrix Corporation
• Inventors: Guthrie, Thomas C.
• Primary Examiner(s): Chin, Tommy P.
• Assistant Examiner(s): Philippe, Gims S.
• Application Number:
  US08/802,615
• Time in Patent Office: 979 Days
• Field of Search: 348/169, 348/170, 348/171, 348/172, 348/142, 348/143, 348/149, 348/150, 348/153, 348/155, 348/218, 382/155, 342/159
• US Class Current: 348/169
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: G06V 20/53 Recognition of crowd images, e.g. recognition of crowd congestion
• CPC Class Codes: G07C 2011/02 related to amusement parks
• CPC Class Codes: G07C 9/00 Individual registration on entry or exit

Abstract

An object tracking system used for monitoring objects as they traverse a controlled space provides for efficient processing and creates a "database output" which includes the direction each object has traveled along with an identification of the specific time at which this object was counted. The system provides for efficient processing through pixel blocking and the use of a crop box to minimize the analysis required.

Claims

1. A tracking apparatus for sensing and tracking the movement of objects in a controlled space, comprising:

sensing means positioned adjacent to the controlled space for monitoring the controlled space and producing an image signal indicative of the condition of the controlled space;

digitizing means attached to the sensing means for receiving the image signal and producing a digitized video signal indicative of the condition of the controlled space;

processing means for receiving the digitized video signal and processing the digitized video signal so as to track the movement of objects in the controlled space, wherein the processing of the digitized signal comprises;

(a) processing a first image and a second image to determine the position of objects in the controlled space, wherein the first image is representative of the condition of the controlled space at a first point in time and the second image is representative of the condition of the controlled space at a second point in time, the position of objects is determined by calculating a difference array between the first image and the second image and identifying those portions of the controlled space that have changed;

(b) blocking the difference array to increase the sensitivity of the system and producing a blocked difference array;

(c) identifying a primary region within the image;

(d) identifying objects present in the primary region based upon the blocked difference array and tagging each object with an identifier;

(e) tracking each object as it traverses the primary region and recording count information once the object has moved a predetermined distance within the primary region.

2. The system of claim 1 wherein the first image and the second image are made up of a plurality of pixels and the difference array is made up of a plurality of pixels difference values.

3. The system of claim 2 wherein the blocking step is accomplished by identifying a plurality of adjacent pixels as a cell and identifying each cell as changed if a predetermined number of pixels have sufficiently changed.

4. The system of claim 3 wherein each pixel is marked as changed if the pixel difference value is above a predetermined level.

5. The system of claim 3 wherein the pixel difference value is equal to the difference between corresponding pixels in the first image and the second image and each pixel is marked as changed if the pixel difference value is greater than a predetermined constant plus a predetermined percentage of the greater pixel value of the first image or the second image.

6. The system of claim 3 wherein each cell comprises a square arrangement of 16 pixels.

7. The system of claim 5 wherein the predetermined number of pixels is equal to 3 pixels.

8. A tracking apparatus for sensing and tracking the movement of objects in a controlled space, comprising:

a sensing device positioned adjacent to the controlled space for monitoring the controlled space and producing an image signal indicative of the condition of the controlled space;

a digitizing device coupled to the to the sensing device for receiving the image signal and producing a digitized video signal indicative of the condition of the controlled space;

a processing device coupled to the digitizing device for receiving the digitized video signal and processing the digitized video signal so as to track the movement of objects in the controlled space, wherein the processing of the digitized signal comprises;

(a) processing a first image and a second image to determine the position of objects in the controlled space, wherein the first image is representative of the condition of the controlled space at a first point in time and the second image is representative of the condition of the controlled space at a second point in time, the position of objects is determined by calculating a difference array between the first image and the second image and identifying those portions of the controlled space that have changed;

(b) blocking the difference array to produce a blocked difference array;

(c) identifying a single, contiguous primary region within the image;

(d) identifying objects present in the primary region based upon the blocked difference array and tagging each object with an identifier;

(e) tracking each object as it traverses the primary region and recording count information once the object has moved a predetermined distance within the primary region.

9. The system of claim 8 wherein the first image and the second image are made up of a plurality of pixels and the difference array is made up of a plurality of pixel difference values.

10. The system of claim 9 wherein the blocking step is accomplished by identifying a plurality of adjacent pixels as a cell and identifying each cell as changed if a predetermined number of pixels have sufficiently changed.

11. The system of claim 10 wherein each pixel is marked as changed if the pixel difference value is above a predetermined level.

12. The system of claim 10 wherein the pixel difference value is equal to the difference between corresponding pixels in the first image and the second image and each pixel is marked as changed if the pixel difference value is greater than a predetermined constant plus a predetermined percentage of the greater pixel value of the first image or the second image.

13. The system of claim 10 wherein each cell comprises a square arrangement of 16 pixels.

14. A tracking apparatus for sensing and tracking the movement of objects in a controlled space, comprising:

a sensing device positioned adjacent to the controlled space for monitoring the controlled space and producing an image signal indicative of the condition of the controlled space;

a processing device coupled to the sensing device for receiving and processing the image so as to track the movement of objects in the controlled space, wherein the processing of the image comprises;

(a) processing a first image at a first point in time and a second image at a second point in time and subsequently calculating a difference array;

(b) blocking the difference array to produce a blocked difference array;

(c) identifying a single, variable primary region within the image, wherein the primary region is variable from substantially the entire image to a substantial fraction of the whole image;

(d) identifying objects present in the primary region based upon the blocked difference array and tagging each object with an identifier;

(e) tracking each object as it traverses the primary region and recording count information once the object has moved a predetermined distance within the primary region.

15. The system of claim 14 wherein the first image and the second image are made up of a plurality of pixels and the difference array is made up of a plurality of pixels difference values.

16. The system of claim 15 wherein the blocking step is accomplished by identifying a plurality of adjacent pixels as a cell and identifying each cell as changed if a predetermined number of pixels have sufficiently changed.

17. The system of claim 16 wherein each pixel is marked as changed if the pixel difference value is above a predetermined level.

18. The system of claim 16 wherein the pixel difference value is equal to the difference between corresponding pixels in the first image and the second image and each pixel is marked as changed if the pixel difference value is greater than a predetermined constant plus a predetermined percentage of the greater pixel value of the first image or the second image.

19. The system of claim 16 wherein each cell comprises a square arrangement of 16 pixels.

20. The system of claim 18 wherein the predetermined number of pixels is equal to 3 pixels.