Television – Image signal processing circuitry specific to television – Special effects
Reexamination Certificate
1999-10-18
2001-08-07
Luu, Matthew (Department: 2672)
Television
Image signal processing circuitry specific to television
Special effects
C348S585000, C348S589000, C348S590000, C348S700000, C348S722000, C382S284000
Reexamination Certificate
active
06271890
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for studio imaging including chromakeying.
BACKGROUND OF THE INVENTION
Background chromakey panels are commonly used in the art of television and video production in order to facilitate merging of a virtual background with foreground figures. The foreground figures are imaged on the chromakey panel background, and the known color of the chromakey panel background is detected and replaced by the virtual background. One problem associated with such productions is that changes in the foreground image, due to camera displacement, pan, tilt and zoom in and out, are not automatically applied to the background scene.
One system designed to solve this problem is the “Virtual Studio” developed by Ultimatte. The “Virtual Studio” requires a special memory head pedestal which measures the camera's pan and tilt angles directly from the camera's mount. A disadvantage of this approach is that in order to obtain a complete perspective transformation for the background image, the zoom state of the lens must be read and the instantaneous location of the camera must be determined. Also, this approach requires that each and every camera mount be replaced by a memory head pedestal, resulting in an expensive system and complicated operation if a large number of cameras are employed. Also, the accuracy of this method is inadequate for seamless foreground/background merging.
Conventional edge detection methods which are based on smoothing and finding directional derivates are described in the following publication, the disclosure of which is hereby incorporated by reference:
Canny, J., “A computational approach to edge detection”, IEEE Trans. on PAMI, PAMI-8, No. 6, 1986, 679-697.
Conventional edge detection methods which are based on Hough transforms are surveyed in the following publication, the disclosure of which is hereby incorporated by reference:
J. Illingworth and J. Kitler, “A survey of the Hough transform”, CVGIP, 44, 1988, 87-116.
FIG. 1A
is a simplified block diagram of a state of the art chromakeying system.
SUMMARY OF THE INVENTION
The present invention seeks to provide improved methods and apparatus for chromakeying.
There is thus provided in accordance with a preferred embodiment of the present invention a chromakeying panel for use in conjunction with a chromakeying system having a color keying spectrum, the panel including a plurality of first locations bearing a first color within the color keying spectrum, and a plurality of second locations bearing a second color within the color keying spectrum.
Further in accordance with a preferred embodiment of the present invention the first color and the second color are of the same hue and of different intensities.
There is additionally provided in accordance with a preferred embodiment of the present invention a chromakeying system including a frame grabber operative to grab an image of a foreground image including at least one nonuniform chromakeying panel having a known pattern and a subject, a perspective transformation computation unit operative to compute a perspective transformation by comparing the image of at least one portion of the captured panel with the known pattern, and a background generation unit operative to receive a background image, to apply the perspective transformation thereto and to replace the captured portion of at least one panel with the transformed background, thereby to generate a composite image.
Still further in accordance with a preferred embodiment of the present invention the system also includes a 3D background image source operative to provide the background generation unit with a 3D representation of a background scene.
Additionally in accordance with a preferred embodiment of the present invention the system also includes a background image sequence source operative to provide the background generation unit with a temporal sequence of background scenes and wherein the perspective transformation computation unit is operative in real time relative to the pace of the temporal sequence.
Also in accordance with a preferred embodiment of the present invention the background image sequence source includes a video clip source and wherein the perspective transformation computation unit is operative in video real time.
Further in accordance with a preferred embodiment of the present invention the system also includes a graphically animated background image source operative to provide the background generation unit with a graphically animated background scene.
Still further in accordance with a preferred embodiment of the present invention the system also includes a photographed background image source operative to provide the background generation unit with a photographed background scene.
Additionally in accordance with a preferred embodiment of the present invention the system includes a user interface communicating with the background generation unit and operative to determine, for individual virtual object locations within the background image, whether the virtual object location is in front of the subject or in back of the subject and wherein the background generation unit is operative to superimpose the subject over back virtual object locations and to super-impose front virtual object locations over the subject.
Further in accordance with a preferred embodiment of the present invention each individual virtual object location includes a single pixel within the background image.
Still further in accordance with a preferred embodiment of the present invention the system includes a rangefinder boresighted to the camera imaging at least one chromakey panel and the subject and operative to measure the range of a plurality of locations within the camera's field of view and wherein the background generation unit is operative to merge overlaying background image locations and subject locations such that the overlaying location having a smaller range is included in the composite image.
Further in accordance with a preferred embodiment of the present invention the system also includes a plurality of cameras imaging at least one chromakey panel and the subject.
Still further in accordance with a preferred embodiment of the present invention the at least one chromakey panel includes a plurality of chromakey panels.
Additionally in accordance with a preferred embodiment of the present invention the background generator is operative to replace chromakey panel pixels with a transformed background also in the case that the camera's momentary field of view is larger than the chromakey panel's field of view.
There is further provided in accordance with a preferred embodiment of the present invention a chromakeying method for use in conjunction with a chromakeying system having a color keying spectrum, the method including providing a chromakeying panel including a plurality of first locations bearing a first color within the color keying spectrum and a plurality of second locations bearing a second color within the color keying spectrum, and imaging a foreground image including the panel and a subject.
There is additionally provided in accordance with a preferred embodiment of the present invention a chromakeying method including grabbing an image of a foreground image including at least one nonuniform chromakeying panel having a known pattern and a subject, computing a perspective transformation by comparing the image of at least one panel with the known pattern, and receiving a background image, applying the perspective transformation thereto and replacing at least one panel with the transformed background, thereby to generate a composite image.
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patent: 4396939 (1983-08-01), Kitahama
patent: 4
Sharir Avi
Tamir Michael
Luu Matthew
Orad, Inc.
Sajous Wesner
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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