Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1999-02-24
2001-05-08
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C348S901000, C725S022000
Reexamination Certificate
active
06229522
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to rasterized imaging systems and, more particularly, to an apparatus and method for producing a representation of a rasterized image. The representation of the rasterized image allows the image to be detected in an incoming video signal.
BACKGROUND OF THE INVENTION
The images which are displayed on cathode ray tube (CRT) display devices such as traditional television monitors and other types of monitors are commonly rasterized images. A rasterized image is made up of a plurality of discrete lines. For example, an NTSC rasterized image contains 525 lines divided into two fields. This type of divided image is referred to as an interlaced image. Each of these fields are used alternately to produce an image on the display device. The display device uses a time varying voltage signal to produce each image line. Each such time varying voltage signal representing a line of a rasterized image will be referred to herein as an image line signal. The image line signals are received serially one after the other, and the display device produces each image line similarly one after the other. Once one image is produced, the process starts over again to produce the next interlaced image. The speed at which the individual image line signals are received and the speed at which the corresponding image lines are written onto the display device is fast enough that the viewer perceives only the overall image. The individual images themselves are each replaced by the succeeding image fast enough that the process appears continuous.
There are many situations in which it is desirable to detect a particular image in an incoming video signal. When recording a commercial television broadcast for example, it may be desirable to detect an advertisement and prevent the advertisement from being recorded along with desired programming. The ability to detect a particular image in an incoming stream of image signals may also be useful in monitoring security or surveillance video feeds. Changing images in the incoming stream of image signals indicates motion.
There have been a number of attempts to provide a reliable system for detecting advertisements in video signals. Prior detection systems fall into the following categories:
(1) systems which detect an audio and/or video fade as a precursor to an advertisement;
(2) systems which sample the image signal frequently during each line of an image, quantizing the sample and comparing the quantized values to previously stored values;
(3) systems which process image samples to isolate an object in the image, and then scan for the isolated object in the same lines of an image being tested;
(4) systems which sample the image signals at multiple points between the start and end of an image and construct a series of digital values indicative of the image;
(5) systems which use embedded information in the non-displayed image signals or associated audio signals to identify images or types of images;
(6) systems which detect specific changes in image fields, possibly over long periods of time, by matching data samples from two distinct fields; and
(7) systems which detect images by applying neural network recognition techniques to data obtained by sampling frequently over a line of an image.
There are number of problems associated with the prior methods used to detect an image in an incoming stream of image signals. Systems which rely on video and audio fading are not reliable because such fading may not occur between multiple advertisements or between advertisements and program segments. Systems which rely on embedded information in the incoming image signals are unreliable because they depend upon the cooperation of the entity transmitting the signal. Sampling techniques generally assume that the image signal is identical for an image used to produce a stored representation and the current incoming image. In fact, signal noise and horizontal shifting of the image signals caused by signal re-synchronization at local stations may result in significantly different sampled values for the same image. Furthermore, many of the current image detection techniques are expensive to implement relative to the cost of a television set or VCR. The prior art devices require high-speed circuitry to facilitate the required real-time comparison between the incoming image and stored images. The prior art systems also require large amounts of memory to store images to be detected.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus and method for detecting an image in a stream of image line signals which make up an incoming rasterized image. Another object of the invention is to provide an apparatus and method for producing an image representation which may be used in detecting the image in an incoming stream of image line signals.
These objects are accomplished by sampling image line signals in a novel fashion to provide a unique representation of a particular image in an incoming stream of image line signals. According to the invention, a set of image line signals from a rasterized image is converted into an ordered sequence of line-based image component values. The ordered sequence of image component values provides a representation of the image. This representation may be stored and later compared with similarly produced representations of incoming images. A match between a stored image representation and a representation of an incoming image indicates that the incoming image is the same as the image represented by the stored representation. Alternatively, where the incoming stream of images comprises images from a surveillance camera, for example, a change in the image representation indicates motion in the image which is captured by the camera.
According to the invention, each image line signal is summed or integrated to produce an image line value representative of the signal. This value is preferably converted into a digital form and used alone or with other digitized image line values to produce an image component value. The resulting image component value comprises one of the values in the ordered sequence of values which makes up the desired image representation. The order of the values in the sequence is determined by the received order of the image line signal or signals used to produce the particular value. The various image component values in the ordered sequence may comprise a single image line value or an average of two or more such values. Averaging two or more image line values has the advantage of reducing the storage space required for storing the image representation and also the advantage of reducing the effects of random noise in the incoming image line signals.
Detecting an image in an incoming stream of image line signals requires four steps. First, an image to be detected is processed to produce an ordered sequence of image component values providing a representation of the image. This step may be referred to as capturing the representation of the image to be detected. The representation of the image to be detected is then stored in a suitable storage device. Next, the incoming stream of image line signals is continually processed in the same fashion as the stored image representation. Thus, an ordered sequence of image component values is produced for each incoming image. Finally, the ordered sequence of image component values produced from the signals for each incoming image is compared to the stored ordered sequence of the image component values produced from the image to be detected. A match between the image representation produced from the incoming image signals and the stored image representation indicates that the incoming image is the same as the image represented by the stored ordered sequence.
As used in this disclosure and the following claims, the term “match” is used to indicate a defined degree of similarity. Image component values of the incoming and stored image representations need not be identical in order for them to be considered a match. Some degree of var
Culbertson Russell D.
Cunningham J. F.
Luu Matthew
Shaffer & Culbertson L.L.P.
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