Television – Special applications – Observation of or from a specific location
Reexamination Certificate
1999-09-13
2002-11-26
Kelley, Chris (Department: 2613)
Television
Special applications
Observation of or from a specific location
C382S262000
Reexamination Certificate
active
06486909
ABSTRACT:
The purpose of this invention is a process and device for identifying and localizing an area in relative movement in a scene and for determining the speed and oriented direction of this relative movement, in real time.
Relative movement means a movement of said area (which may be composed of an “object” in the broadest sense of the term including a living being or a portion of a living being, for example a hand) in an approximately motionless environment, or more or less complete immobility of said area (or “object”) in an environment that is at least partially in movement.
The invention relates to the processing of a digital video output signal from an observation system composed of an optical imput system or objective capable of forming an image of the observed scene, and by an optoelectronic conversion system or sensor capable of converting said image that it receives into a digital output signal.
In general, the observation system is composed of a video camera or camescope that observes the scene to be monitored (said digital output signal then being composed of the digital video signal output by a camera with a digital output or of the output of an analog/digital converter, the input of which is connected to the output of a camera outputting an analog video signal.
The observation system may also be composed of the objective of an optical instrument (binoculars, sighting refracting instrument, view-finder), from which at least a portion of the outgoing light beam is sampled and by a photoelectronic sensor, for example of the CCD or CMOS type, with the normal associated electronic system, sensor receiving the image formed by said portion of the light beam and converting it through the associated electronic system into a digital video output signal.
The invention consists mainly of processing the digital video output signal from an observation system, particularly a video camera, with a digital output to determine signals signaling the existence and localization of an area in relative movement in said scene, and the speed and oriented direction of the displacement if said area is actually moving in said scene relatively to an approximately motionless environment, in real time.
The best system yet developed for identifying and localizing an object in relative movement and for determining its speed and oriented direction of displacement is animal or human sight, for example a hunter in his hide localizing the displacement of an animal, and the direction and speed of this displacement.
Prior art surveillance devices like artificial retinas, either analog (Giocomo Indiveri et al, in Proceedings of MicroNeuro'96 pp 15 to 22), or digital (Pierre-François Rüedi in Proceedings of MicroNeuro'96 pp 23 to 29), have been proposed, but the first article deals with detectors and analog units with complex structures, and the second article deals with means of identifying the edges of an object; furthermore, very fast and high capacity memories are used in the devices described in order to operate in real time, and limited information is obtained about moving areas or objects.
Thus the suggestion was made of memorizing a frame output signal from a video camera, or similar instrument, composed of a sequence of data relative to pixels representative of the scene observed by the camera at time t
0
in a first two-dimensional memory, and then the video signal for the next corresponding frame representing said scene at time t
1
, in a second two-dimensional memory. If an object has moved between t
0
and t
1
, on the one hand, the distance d by which the object has moved in the scene between t
1
and t
0
and, on the other hand, the time T=t
1
−t
0
between the beginnings of two successive corresponding frames relative to the same pixels are determined. The displacement speed is then equal to d/T. This type of system requires a very large total memory capacity if it is required to obtain precise speed and oriented direction indications characterizing the displacement. Furthermore, there is some delay in obtaining the speed and displacement direction indications; this information is not available until time t
1
+R, where R is the time necessary for the calculations for the period t
0
−t
i
.These two disadvantages (the need for a large memory capacity and the delay in obtaining the required information) limit applications of this type of system.
Furthermore, French patent No. 2.611.063, of which one of the inventors (Mr. Patrick Pirim) is the inventor of the present invention, describes a process and a device for real time processing of a sequenced data flow, composed in particular of the output signal from a camescope, in order to perform data compression. According to this prior patent, the histogram of signal levels is formed using a classification law for a first sequence, the representative Gauss function associated with this histogram is memorized and the maximum and minimum levels are extracted from it, the levels of the next sequence or second sequence are compared with said signal levels for the first sequence memorized with a constant time constant identical for each pixel, a binary classification signal is generated that characterizes the next said sequence with reference to the classification law, an auxiliary signal is generated from this binary signal representative of the duration and position of a range of significant values, and finally said auxiliary signal is used to generate a signal localizing the range with the longest duration, called the dominant range, and these operations are repeated for subsequent sequences of the sequenced signal. This process and this device of classification enable data compression, keeping only interesting parameters in the processed flow of sequenced data. In particular, this process is capable of processing a digital video signal representative of a video image in order to extract and localize at least one characteristic of at least one area in said image. It is thus possible to classify brightness and/or chrominance levels of the signal and to characterize and localize an object in the image.
U.S. Pat. No. 5,488,430 detects and estimates a displacement by determining horizontal and vertical changes in the image of the observed area separately. Difference signals are used to detect movements from right to left or from left to right, or from top to bottom or bottom to top, in the horizontal and vertical directions respectively, firstly by carrying out the EXCLUSIVE OR logical function on horizontal/vertical difference signals and frame difference signals, and secondly by using a ratio of the sums of horizontal/vertical signals and the sums of frame difference signals with respect to a K×3 window. In this U.S. Pat. No. 5,488,430, calculated values of the image along two orthogonal horizontal and vertical directions are used with an identical repetitive difference K in these two orthogonal directions, this difference K being defined as a function of the displacement speeds that are to be determined. The device according to this US patent determines the direction of movements along each of the two orthogonal directions by applying a set of calculation operations indicated in columns 12 (at the beginning and end) and 13 (at the beginning) to the difference signals, which requires very complex (and therefore difficult to execute) electronic computing units performing particularly division, multiplication and summation; furthermore, additional complex computing units are necessary to obtain the speed and oriented direction of displacement (extraction of square root to obtain the amplitude of the speed and calculation of the arc tan function to obtain the oriented direction), starting from projections on the two horizontal and vertical axes. Finally U.S. Pat. No. 5,488,430 does not include any means of smoothing pixel values by means of a time constant, variable for each pixel, in order to compensate for excessively fast variations of these values.
On the contrary, the process according to the invention is embodie
Bugg George A
Holding B.E.V.
Kelley Chris
Townsend and Townsend / and Crew LLP
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