GB2215938A - Background differencing operator for target motion detection - Google Patents

Background differencing operator for target motion detection Download PDF

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Publication number
GB2215938A
GB2215938A GB8902047A GB8902047A GB2215938A GB 2215938 A GB2215938 A GB 2215938A GB 8902047 A GB8902047 A GB 8902047A GB 8902047 A GB8902047 A GB 8902047A GB 2215938 A GB2215938 A GB 2215938A
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United Kingdom
Prior art keywords
image
pixel
operator
regions
difference
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8902047A
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GB2215938B (en
GB8902047D0 (en
Inventor
Enoch James
Raymond Joseph Paul Stafford
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems PLC
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British Aerospace PLC
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Filing date
Publication date
Priority claimed from GB888803480A external-priority patent/GB8803480D0/en
Application filed by British Aerospace PLC filed Critical British Aerospace PLC
Priority to GB8902047A priority Critical patent/GB2215938B/en
Publication of GB8902047D0 publication Critical patent/GB8902047D0/en
Publication of GB2215938A publication Critical patent/GB2215938A/en
Application granted granted Critical
Publication of GB2215938B publication Critical patent/GB2215938B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00Image analysis
    • G06T7/20Analysis of motion
    • G06T7/254Analysis of motion involving subtraction of images

Abstract

The images of two successive scenes are subtracted pixel by pixel to leave an image containing only a moving target, the background being eliminated. If the background moves relative to the camera the background is not eliminated, edges in particular being prominent, Fig 5. In order to obviate this effect a pixel from the second image is subtracted not only from the corresponding pixel in the first image, but also from each of pxq pixels Figure 6 adjacent to the corresponding pixel and the minimum difference used in the resultant image. <IMAGE>

Description

BACKGROUND DIFFERENCING OPERATOR FOR TARGET MOTION DETECTION This invention relates to guidance systems, specifically, but not exclusively, to systems where the background is removed from the field of view (FOV).
Generally the background information in a FOV is removed by differencing two frames. If the camera or guidance system is stationary relative to the background, i.e. only the target is moving, the background can be eliminated from the differenced scene. However, if the camera and! our the background are moving relative to each other the situation is not as simple, as straightforward differencing would result in significant background edge information in the differenced scene.
Accordingly, one object of the present invention is to provide a means for differencing scenes without producing background edge information.
According to a first aspect of the present invention there is provided a video image processing method in which each pixel of one recorded video image is compared with a corresponding pixel of another recorded video image and with each of a plurality of pixels of the another image which are adjacent to said corresponding pixel using a p x q difference operator so as to determine the minimum one of the differences between the pixel of the one image and the corresponding and adjacent pixels of the another image, and then using the minimum difference values to construct a further video image representative of the difference between said one and said another image.
According to a second aspect of the present invention there is provided a method for producing a differenced image for regions of more than one image wherein said regions contain substantially the same stationary features, in which said method includes the steps of: recording more than one images of a scene; locating equivalent regions within two or more of said images in which said regions contain essentially the same stationary features; applying a 3x3 difference operator to the pixels of one of said regions in which the minimum difference is determined between the pixel at the same location as the central position of said operator in one scene and each of the pixels of said operator in another scene; scanning said operator raster fashion; and, producing a difference image from the minimum difference value for each pixel within said regions.
Reference will now be made, by way of example, to the accompanying drawings in which:- Figure 1 is a diagram of two scenes in which the background is consistent in both scenes; Figure 2 is a diagram of the difference scene of the Figure la scenes; Figure 3 is a diagram of two further scenes in which the background is different in the scenes; Figure 4 is a diagram of the ideal differenced scene of the Figure 3 scenes; Figure 5 is a diagram of the actual differenced scene of the Figure 3 scenes; and, Figure 6 is a diagram illustrating two pixel masks for placing over the one to the scenes of, for example, Figure 3.
Referring to Figure 1, an aircraft 1 is shown in images 2 and 3 of consecutive scenes. The background in both of image 2 and 3 is identical since the background is not moving relative to the camera (or vice versa). The difference between the images can be seen from Figure 2 and is simply that the aircraft 1 is in different positions (A and B) in each image.
Referring to Figure 3, the aircraft 1 is again shown in images 4 and 5 of two consecutive scenes. In this case however, the background is moving relative to the camera. In order to obtain a differenced image only the regions in which the background is equivalent in both images i.e. regions 6 and 7 should be considered.
Assuming regions 6 and 7 are accurately predicted a differenced image as shown in Figure 4 would be produced However it is typically only possible to locate regions 6 and 7 to an accuracy of an F1 pixel. Differencing thus results in significant edge information 8 as shown in Figure 5.
In order to overcome this problem a difference operator is used to obtain the differenced image. Referring to Figure 6, pixels I and p are in corresponding positions in images 9 and 10 of two consecutive scenes. Instead of just subtracting pixels I and p from each other, pixel I is in addition taken away from pixel p's eight nearest neighbours (a,b,c,d,e,f,g and h). The smallest value obtained from these absolute differences goes into the difference scene. The difference scene pixel value D is given by: D = min (lI-pl, lI-bl, lI-cl, II-dl, il-el, fl, II-gl, II-hl This 3 x 3 operator is applied to the first image of two for each pixel position in the region of common background, (e. g.
for 6 and 7). The operator is scanned raster fashion over all the pixels of regions 6 and 7 except for the outer border, one pixel deep. The resulting difference image will contain only target information as in the ideal situation of Figure 4.

Claims (2)

1. A video image processing method in which each pixel of one recorded video image is compared with a corresponding pixel of another recorded video image and with each of a plurality of pixels of the another image which are adjacent to said corresponding pixel using a p x q difference operator so as to determine the minimum one of the differences between the pixel of the one image and the corresponding and adjacent pixels of the another image, and them using the minimum difference values to construct a further video image representative of the difference between said one and said another image.
2. A method for producing a differenced image for regions of more than one image wherein said regions contain substantially the same stationary features, in which said method includes the steps of: recording more than one images of a scene; locating equivalent regions within two or more of said images in which said regions contain essentially the same stationary features; applying a 3x3 difference operator to the pixels of one of said regions in which the minimum difference is determined between the pixel at the same location as the central position of said operator and each of the pixels of said operator; scanning said operator raster fashion; and, producing a difference image from the minimum difference value for each pixel within said regions.
GB8902047A 1988-02-15 1989-01-31 Background differencing operator for target motion detection Expired - Lifetime GB2215938B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8902047A GB2215938B (en) 1988-02-15 1989-01-31 Background differencing operator for target motion detection

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888803480A GB8803480D0 (en) 1988-02-15 1988-02-15 Background differencing operator for target motion detection
GB8902047A GB2215938B (en) 1988-02-15 1989-01-31 Background differencing operator for target motion detection

Publications (3)

Publication Number Publication Date
GB8902047D0 GB8902047D0 (en) 1989-03-22
GB2215938A true GB2215938A (en) 1989-09-27
GB2215938B GB2215938B (en) 1991-12-04

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Family Applications (1)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0457414A1 (en) * 1990-05-18 1991-11-21 Laboratoires D'electronique Philips S.A.S. Object detection device in an image sequence
EP0487236A2 (en) * 1990-11-20 1992-05-27 Hughes Aircraft Company Moving target detection method using two-frame subtraction
EP0686932A2 (en) * 1994-03-17 1995-12-13 Texas Instruments Incorporated A computer vision system to detect 3-D rectangular objects
GB2330974A (en) * 1997-10-10 1999-05-05 Harlequin Group Plc Image matte production without blue screen
US7630503B2 (en) 2003-10-21 2009-12-08 Mitel Networks Corporation Detecting acoustic echoes using microphone arrays

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0457414A1 (en) * 1990-05-18 1991-11-21 Laboratoires D'electronique Philips S.A.S. Object detection device in an image sequence
FR2662282A1 (en) * 1990-05-18 1991-11-22 Philips Electronique Lab DEVICE FOR DETECTING OBJECTS IN A PICTURE SEQUENCE.
WO1991018358A1 (en) * 1990-05-18 1991-11-28 N.V. Philips' Gloeilampenfabrieken Device for detecting objects in a sequence of images
EP0487236A2 (en) * 1990-11-20 1992-05-27 Hughes Aircraft Company Moving target detection method using two-frame subtraction
EP0487236A3 (en) * 1990-11-20 1994-01-05 Hughes Aircraft Co
EP0686932A2 (en) * 1994-03-17 1995-12-13 Texas Instruments Incorporated A computer vision system to detect 3-D rectangular objects
EP0686932A3 (en) * 1994-03-17 1997-06-25 Texas Instruments Inc A computer vision system to detect 3-D rectangular objects
GB2330974A (en) * 1997-10-10 1999-05-05 Harlequin Group Plc Image matte production without blue screen
US7630503B2 (en) 2003-10-21 2009-12-08 Mitel Networks Corporation Detecting acoustic echoes using microphone arrays

Also Published As

Publication number Publication date
GB2215938B (en) 1991-12-04
GB8902047D0 (en) 1989-03-22

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20060131