Surveillance apparatus and recording medium recorded surveillance program

• US 6,798,909 B2
• Filed: 05/18/2001
• Issued: 09/28/2004
• Est. Priority Date: 12/27/1999
• Status: Expired due to Fees

• Current Assignee: Hitachi Industry & Control Solutions, Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Fujita, Takehiro, Nagaya, Shigeki, Miyatake, Takafumi, Nagasaka, Akio
• Primary Examiner(s): Mehta, Bhavesh M.
• Assistant Examiner(s): DESIRE, GREGORY M
• Application Number:
  US09/859,509
• Publication Number:
  US 20010024513A1
• Time in Patent Office: 1,229 Days
• Field of Search: 345/582, 345/612-615, 345/419-421, 345/423-425, 345/430, 345/435, 345/437, 345/447, 382/173, 382/181, 382/190-193, 382/203, 382/236-239, 382/266, 382/268, 382/271-272, 382/291, 348/135, 348/152, 348/169
• US Class Current: 382/190
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19604 involving reference image or background adaptation with time to compensate for changing conditions, e.g. reference image update on detection of light level change
• 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 13/19671 Addition of non-video data, i.e. metadata, to video stream
• CPC Class Codes: G08B 13/19676 Temporary storage, e.g. cyclic memory, buffer storage on pre-alarm
• CPC Class Codes: G08B 13/1968 Interfaces for setting up or customising the system
• CPC Class Codes: G08B 13/19682 Graphic User Interface [GUI] presenting system data to the user, e.g. information on a screen helping a user interacting with an alarm system
• CPC Class Codes: G08B 13/19691 Signalling events for better perception by user, e.g. indicating alarms by making display brighter, adding text, creating a sound

Abstract

An economical surveillance apparatus robust to an environmental change includes an input unit for inputting images in a time series, a background image memory unit for storing a plurality of input images, a difference image memory unit for calculating and storing difference degree between a plurality of background images of the background image memory unit and an image inputted afresh, and a judging unit for judging an existence/absence of an invading object by utilizing the value of the difference degree of the difference image memory unit. This surveillance apparatus can automatically register a plurality of background images from a camera image. Since the background images that are no longer used are automatically erased, the drop of detection speed and detection sensitivity can be prevented.

Claims

1. A recording medium having recorded thereon a surveillance program executed by a computer including input/output means, a CPU and a memory, said program comprising the steps of:

inputting images in a time series from said input/output means;

registering a plurality of different background images from said images into said memory;

calculating a minimum value of a difference between each of said plurality of different background images and an image inputted afresh for each pixel, and storing said minimum value in said memory; and

judging an existence/absence of an invading object on the basis of said difference.

2. A recording medium according to claim 1, wherein each of said plurality of different background images comprises a single or a plurality of pixel values registered for each pixel.

3. A recording medium according to claim 2, wherein:

said surveillance program includes a step of erasing said background image;

in said erasing step, a pixel to be erased is decided on the basis of a period from a registration time of each of said pixel values to a time at which said pixel is last looked up, and a period from the time at which said pixel is last looked up to a present time; and

when registration is made, new pixel value is written to an empty region if said empty region exists in said memory, and if said empty region does not exist, a degree of importance for each pixel value of a corresponding pixel is calculated and is overwritten to a pixel value having the lowest degree of importance.

4. A recording medium according to claim 1, wherein said surveillance program further includes a step of recording said image inputted afresh when said invading object is judged to exist.

5. A recording medium according to claim 1, wherein said surveillance program further includes the steps of:

storing a minimum value image comprising an absolute value of a difference for each pixel; and

dividing said minimum value image into blocks, calculating and storing a mean value of an absolute value for a difference for each of said blocks;

wherein an existence/absence of an invading object is judged on the basis of a time series change of said mean value.

6. A computer readable medium having embodied thereon a surveillance program which, when executed by a computer system, performs the method comprising:

receiving images in time series from one or more input devices;

registering a plurality of different background images from the images;

detecting a presence absence of an invading object from the images of one or more input devices, by;

determining an absolute value of a difference between an input image and each of said plurality of different background images for each pixel,

determining a minimum value image among all the background images at which the difference between the input image and each of said plurality of different background images is minimal,

determining a mean value of a difference for each discrete block within the minimum value image, and

determining the presence/absence of an invading object on the basis of a time series change of said mean value.

7. A computer readable medium according to claim 6 wherein each of said plurality of different background images comprises a single or a plurality of pixel values registered for each pixel.

8. A computer readable medium according to claim 6, wherein:

each background image is registered or erased for each pixel;

erasing is determined on the basis of a period from a registration time of said pixel to a time at which said pixel is last looked up, and a period from a time at which said pixel is last looked up to a current time;

when registration is made, a new pixel value is written to an empty region if said empty region exists in a background image memory section of said memory device, and if said empty region does not exist, importance of each pixel value of a corresponding pixel is calculated and is overwritten to an image value having the lowest degree of importance.

9. A computer readable medium according to claim 6, wherein said input image is recorded afresh for each pixel, when the invading object is present.

10. A computer readable medium according to claim 6, further comprising:

an input image storage section for storing an input image afresh for each pixel;

a background image storage section for registering a plurality of different background images; and

a difference image storage section for storing the minimum value image in discrete blocks, and for storing the mean value of the difference for each block.