Video based system and method for detecting and counting persons traversing an area being monitored

• US 6,697,104 B1
• Filed: 01/13/2000
• Issued: 02/24/2004
• Est. Priority Date: 01/13/2000
• Status: Expired due to Term

• Current Assignee: CountWise LLC
• Original Assignee: CountWise LLC
• Inventors: Topaz, Dov, Yakobi, Ron
• Primary Examiner(s): Rao, Andy
• Assistant Examiner(s): PARSONS, CHARLES E
• Application Number:
  US09/481,447
• Time in Patent Office: 1,503 Days
• Field of Search: 348/153, 348/156, 348/143, 382/118, 382/115
• US Class Current: 348/143
• CPC Class Codes: G06V 20/53 Recognition of crowd images, e.g. recognition of crowd congestion
• CPC Class Codes: G07C 9/00 Individual registration on entry or exit
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19606 Discriminating between target movement or movement in an area of interest and other non-signicative movements, e.g. target movements induced by camera shake or movements of pets, falling leaves, rotating fan
• CPC Class Codes: G08B 13/19619 Details of casing
• CPC Class Codes: G08B 13/19632 Camera support structures, e.g. attachment means, poles
• CPC Class Codes: G08B 13/19656 Network used to communicate with a camera, e.g. WAN, LAN, Internet

Abstract

A video based system and method for detecting and counting persons traversing an area being monitored is provided. The method includes the steps of initialization of at least one end unit forming part of a video imaging system, the end unit having at least one camera installed therein, the camera producing images within the field of view of the camera of at least part of the area being monitored, the end unit includes at least a non-volatile memory unit and a working memory unit, the non-volatile data memory unit includes a plurality of counters; digitizing the images and storing the digitized images in at least one of the non-volatile memory unit and a working memory unit; detecting objects of potential persons from the digitized images; comparing the digitized images of objects detected in the area being monitored with digitized images stored in the working memory unit to determine whether the detected object is a new figure that has entered the area being monitored or whether the detected object is a known figure, that has remained within the area being monitored and to determine that a figure which was not detected has left the area being monitored; and incrementing at least one of the plurality of counters with an indication of the number of persons that have passed through the area being monitored.

Claims

1. A method for detecting and counting persons traversing an area being monitored comprising:

initialization of at least one end unit forming part of a video imaging system, said end unit having at least one camera installed therein, said camera producing images within the field of view of the camera of at least part of the area being monitored, said end unit comprising at least a non-volatile memory unit and a working memory unit, the non-volatile data memory unit comprising a plurality of counters;

digitizing said images and storing said digitized images in at least one of said non-volatile memory unit and a working memory unit;

detecting objects of potential persons from said digitized images;

comparing the digitized images of objects detected in the area being monitored with digitized images stored in the working memory unit to determine whether the detected object is a new figure that has entered the area being monitored or whether the detected object is a known figure, that has remained within the area being monitored and to determine that a figure which was not detected has left the area being monitored; and

incrementing at least one of said plurality of counters with an indication of the number of persons that have passed through the area being monitored,

wherein said initialization step comprises the step of determining the optimum pixel scale (P_scale) required for processing in accordance with the formula;

$P_{\mathrm{scale}}=\frac{H\times <br><br>W_{\mathrm{ccd}}}{W_{\mathrm{pixel}}\times <br><br>F_{\mathrm{ccd}}},\mathrm{where}<br><br>\text{;<br><br>}=H=\mathrm{Height};<br><br>W_{\mathrm{ccd}}=\mathrm{width}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{the}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{camera}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{sensor};<br><br>W_{\mathrm{pixel}}=\mathrm{width}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{the}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{FOV}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{in}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{pixel}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{units};<br><br>F_{\mathrm{ccd}}=\mathrm{focal}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{length}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{the}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{camera}.$

2. The method according to claim 1, wherein said step of incrementing further comprises at least one of the steps of:

incrementing one of said plurality of counters with an indication of the number of persons that have passed through the area being monitored and have left the areas in a pre-determined direction; and

incrementing one of said plurality of counters with an indication of the number of persons that have passed through the area being monitored and have left the areas in one of at least two directions.

3. The method according to claim 1, and further comprising the step of:

remotely retrieving data from one of said non-volatile memory unit and a working memory unit via a communications network.

4. The method according to claim 1, and further comprising the step of:

processing data to produce a displayable report;

encrypting said report; and

accessing said encrypted report from a remote site via a communications network, said encrypted report being accessible by authorized users.

5. The method according to claim 3, wherein said communications network is one of a group including a GSM cellular network and the Internet.

6. The method according to claim 4, wherein said communications network is one of a group including a GSM cellular network and the Internet.

7. The method according to claim 1, wherein the field of view of the camera includes more than one area being monitored.

8. The method according to claim 1, wherein said step of initialization further comprises the step of:

determining the direction of motion of persons being monitored.

9. The method according to claim 8, wherein said step of initialization further comprises the step of:

input the network ID data of the end unit if said unit is connected as part of a network of end units.

10. The method according to claim 8, wherein said step of determining the direction of motion of the figures comprises the steps of:

positioning the at least one camera above and perpendicular to the center of the area being monitored; and

initializing the video processor with directional definitions for bi-directional motion through the monitored area and the height of the camera above the surface.

11. The method according to claim 10, wherein said step of digitizing comprises the steps of:

in a time T1, receiving a first array of binary data containing the grayness level existing over a given area and storing said first array in the program working memory;

in a time T2, receiving a second array of binary data containing grayness levels existing over the same given area;

calculating the differences between the first and second arrays at the single pixel level to obtain an array representing color differences;

creating a bitmap at the single pixel level comprising a binary array indicating a substantial change of color at the single pixel level and changes that have not occurred or are less than a pre-determined threshold level;

processing the bitmap to prepare an “

Y”

histogram to locate coordinates of concentrations of changes in the direction perpendicular to the direction of expected motion and an “

X ”

histogram to find overlapping coordinates of change concentrations in the direction of expected motion; and

analyzing said “

Y” and

“

X”

histogram at the single pixel level.

12. The method according to claim 10, wherein said step of incrementing comprises the steps of:

incrementing said counter for each object identified as a person passing through the area being monitored, said person being identified by assigning a direction of motion to an object determined to be a potential person and verifying the direction of the potential person over a period of time to determine the potential person as a person to be counted.

13. The method according to claim 10, wherein said step of detection further comprises the step of:

filtering said histogram by rejecting those coordinates where the space between them is too narrow to contain a human figure as determined by pre-determined thresholds.

14. The method according to claim 13, wherein said pre-determined thresholds representing the width of a man'"'"'s shoulders and the distance between his chest and back in the direction of the expected bi-directional motion.

15. The method according to claim 13, wherein said step of detection further comprises the step of further filtering said histogram by rejecting objects not having a sufficiently high density change representing a person in motion.

16. The method according to claim 13, wherein said step of detection further comprises the step of applying a spatial frequency threshold.

17. The method according to claim 16, wherein said spatial frequency threshold is performed alternately from both sides of the potential figure.

18. The method according to claim 16, further comprising the steps of:

identifying a person as a moving figure by comparing the potential figure with previously verified figures stored in memory and comparing the potential figure with previously detected but non-verified figures stored in memory.

19. The method according to claim 18, further comprising the steps of:

comparing the potential figure with previously detected figures stored in memory; and

searching for previously detected figures that were not detected during the present detection period.

20. The method according to claim 19, further comprising the steps of:

determining that a person has left the above area if said person was not detected during a plurality of detection periods.

21. An end unit for use with a video based image processing system, the end unit configured to obtain information about the motion of people, the end unit comprising:

at least one CCD camera;

an A/D converter for converting analog information from the camera to digital information;

a digital switching unit connected to the A/D converter;

a video processor connected to the digital switching unit, for receiving the digital video information from said digital switching unit and to process said digital information at a single pixel level; and

a non-volatile memory unit and a program working memory unit coupled through an address and data bus to the video processor.

22. The end unit according to claim 21, and further comprising:

at least one digital video data input connected to the digital switching unit for receiving data from a second CCD camera external to the end unit.

23. The end unit according to claim 21, wherein said non-volatile memory unit is remotely accessible and contains data on the quantity of people and their direction of their motion.

24. The end unit according to claim 21, wherein said non-volatile memory unit includes discrete data input stored therein.

25. The end unit according to claim 21, and further configured for installation in an acoustic ceiling, having the body of the end unit above the ceiling and the CCD camera below the ceiling.

26. The end unit according to claim 25, wherein said camera is fitted within a dome unit connectable to said body by snap connectors fitted to extendable flanges attached.

27. A video based system for detecting and counting persons traversing an area being monitored comprising:

at least one end unit, said end unit comprising;

at least one CCD camera;

an A/D converter for converting analog information from the camera to digital information;

a digital switching unit connected to the A/D converter;

a video processor connected to the digital switching unit, for receiving the digital video information from said digital switching unit and to process said digital information at a single pixel level; and

a non-volatile memory unit and a program working memory unit coupled through an address and data bus to the video processor;

a device for remote retrieval of the data stored in said non-volatile memory unit;

a device for processing said data and generating reports therefrom; and

a device for displaying said reports.

28. The system according to claim 27 wherein said report is encrypted and wherein said encrypted report is accessible from a remote site via a communications network by authorized users.

29. The method according to claim 28, wherein said communications network is one of a group including a GSM cellular network and the Internet.

30. A method for detecting and counting persons traversing an area being monitored comprising:

in a time T1, receiving a first array of binary data containing the grayness level existing over a given area;

in a time T2, receiving a second array of binary data containing grayness levels existing over the same given area;

calculating the differences between the first and second arrays at the single pixel level to obtain an array representing color differences;

creating a bitmap at the single pixel level comprising a binary array indicating a substantial change of color at the single pixel level and changes that have not occurred or are less than a pre-determined threshold level;

processing the bitmap to prepare an “

Y”

histogram to locate coordinates of concentrations of changes in the direction perpendicular to the direction of expected motion and an “

X”

histogram to find overlapping coordinates of change concentrations in the direction of expected motion; and

analyzing said “

Y” and

“

X”

histogram at the single pixel level.