Surveillance apparatus and recording medium recorded surveillance program

• US 20010010731A1
• Filed: 12/22/2000
• Published: 08/02/2001
• Est. Priority Date: 12/27/1999
• Status: Active Grant

• Current Assignee: Hitachi Industry & Control Solutions, Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Nagaya, Shigeki, Miyatake, Takafumi, Nagasaka, Akio, Fujita, Takehiro
• Granted Patent: US 6,798,908 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• 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 surveillance apparatus comprising:

input means for inputting images in a time series;

background image memory means for registering a plurality of background images from said images;

difference image memory means for calculating a minimum value of difference degree of an absolute value of a difference between said background image and an image afresh inputted for each pixel and storing said difference; and

judgment means for judging an existence/absence of an invading object on the basis of said difference degree.

2. A surveillance apparatus according to

claim 1

, wherein said background image comprises a single or a plurality of pixel values registered for each pixel.

3. A surveillance apparatus according to

claim 2

, wherein:

said 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 present time;

when registration is made, a new pixel value is written to an empty region if said empty region exists in said background image memory means, 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.

4. A surveillance apparatus according to

claim 1

, which further includes:

memory means for recording said image inputted afresh when said judgment means judges that an invading object exists.

5. A surveillance apparatus according to

claim 1

, wherein:

said difference image memory means includes minimum value image memory means for storing a minimum value image comprising an absolute value of a difference for each pixel and block-wise mean image memory means for dividing said minimum value image into blocks, and calculating and storing a mean value of an absolute value of a difference for each block; and

said judgment means judges an existence/absence of an invading object on the basis of a time series change of said mean value.

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

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

calculating a minimum value of difference degree of an absolute value of a difference between said background image 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 degree.

7. A recording medium according to

claim 6

, wherein said background image comprises a single or a plurality of pixel values registered for each pixel.

8. A recording medium according to

claim 7

, 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 it is last looked up, and a period from the time at which it is last looked up to a present time; and

in said registration step, a new pixel value is written to an empty region if said empty region exists in said background image memory means, 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.

9. A recording medium according to

claim 6

, wherein when said surveillance program further includes a step of recording said image inputted afresh when said judgment means judges that an invading object exists.

10. A recording medium according to

claim 6

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

wherein;

said judgment step judges an existence/absence of an invading object on the basis of a time series change of said mean value.