Television – Panoramic
Patent
1996-05-01
1998-08-04
Britton, Howard W.
Television
Panoramic
348143, H04N 700
Patent
active
057901813
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns surveillance systems. More particularly, it concerns imaging systems for the panoramic surveillance of a space using a single, stationary, camera.
BACKGROUND OF THE INVENTION
With recent increases in the occurrence of the crimes of theft and armed robbery, it has become commonplace to install a system for the surveillance of supermarkets, shop checkout areas, banks and other spaces. Conventional surveillance systems use either multiple video cameras (each monitoring a zone of the space) or a single, mechanically scanned camera. The former of these systems requires the observer to check several image displays to monitor the entire field of view. The latter type of system displays only a narrow field of view at any instant, which reduces the value of the system as a surveillance tool.
Both of these conventional surveillance systems are quite expensive, requiring either multiple cameras and monitors or a mechanical drive for scanning the camera. Systems employing moving cameras consume more power and require more maintenance. A further disadvantage of the moving camera system is that any motion of an object that is within the image is difficult to detect from simple observation of a monitor screen, due to the apparent continual full-field image motion that is induced by the movement of the camera.
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to produce a surveillance system which utilises a single camera, which requires no movement of that camera, and yet which has a panoramic field of view that can be displayed on a single monitor screen.
This objective is achieved using a suitable camera (an electronic camera--either a "still" camera or a video camera--having a charge coupled device (CCD) sensor at its image plane, being particularly suitable) and a dome-like convex mirror. Typically the dome-like convex mirror is mounted on the ceiling of a room to be monitored (though the mirror may be mounted in other locations whenever it is more appropriate to do so in view of the nature of the surveillance to be performed). The camera is mounted relative to the mirror in such a manner that a major part (if not all) of the curved surface of the mirror is within the field of view of the camera. The mirror has a profile such that it projects most--preferably all--of the environment in which the mirror is mounted onto the imaging plane of the camera.
Thus, according to the present invention there is provided a panoramic imaging system for a space, said system comprising (i) a camera and (ii) a mirror, said system being characterised in that: curved surface; portion of the surface of the mirror is within the field of view of the camera; at least a major part of said space onto the imaging plane of the camera; and and the profile of said dome-like mirror satisfies the relationship, in polar co-ordinates,
where the origin of the co-ordinates is at the actual or virtual position of the aperture lens of said camera, r is the distance of a point on the mirror profile from the origin along a direction inclined at an angle .theta. with respect to the optical axis of the camera, C is a constant, and A specifies the inclination of the profile to the optical axis of the camera at the point on said dome-like mirror which is closest to the aperture lens of the camera.
Preferably an electronic camera having a charge coupled device (CCD) sensor at its imaging plane is used in implementations of the present invention. Such a camera (which may be a video camera or a "still" camera which produces an image in a fairly long time, of up to one minute) will produce a warped image of the space being observed, which may be displayed directly on a monitor screen. Alternatively, the signal processing of the output of the camera sensor may be modified so that the image co-ordinates are changed and a de-warped image is displayed on the monitor screen. If movement detecting software is included as part of the signal processing package, any movement within the region being mon
Chahl Javaan Singh
Nagle Martin Gerard
Sobey Peter John
Srinivasan Mandyam Veerambudi
Australian National University
Britton Howard W.
Le Vu
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