Optical: systems and elements – Projection screen – Curved
Reexamination Certificate
2000-10-27
2002-07-23
Mahoney, Christopher (Department: 2851)
Optical: systems and elements
Projection screen
Curved
C359S458000, C345S419000, C367S038000, C367S070000, C367S072000, C353S007000
Reexamination Certificate
active
06424464
ABSTRACT:
This invention relates to a method and apparatus for projecting spatially correct seismic data onto a large three-dimensional (3D) curved display surface, to aid in interpretation of geological characteristics of the earth. More specifically, this invention relates to a method for projecting computer graphic video images of seismic data onto a large curved 3D display surface, allowing viewers to interact with the 3D display, and to use their peripheral vision, and thus perceive the displayed imagery with a sense of realism comparable with natural viewing of a 3D physical reality.
BACKGROUND OF THE INVENTION
For many years seismic exploration for oil and gas has involved the use of a source of seismic energy and its reception by an array of seismic detectors, generally referred to as geophones. When used on land, the source of seismic energy can be a high explosive charge electrically detonated in a borehole located at a selected point on the terrain, or another energy source having capacity for delivering a series of impacts or mechanical vibrations to the earth's surface. Offshore, air gun sources and hydrophone receivers are commonly used. The acoustic waves generated in the earth by these sources are reflected back from strata boundary and/or other discontinuities and reach the earth's surface at varying intervals of time, depending on the distance traversed and the characteristics of the subsurface traversed. On land these returning waves are detected by the geophones, which function to transduce such acoustic waves into representative electrical analog signals, which are generally referred to as traces. In use on land an array of geophones is generally laid out along a grid covering an area of interest to form a group of spaced apart observation stations within a desired locality to enable construction of three-dimensional views of reflector positions over wide areas. The source, which is offset a desired distance from the geophones, injects acoustic signals into the earth, and the detected signals at each geophone in the array are recorded for later processing using digital computers, where the analog data is generally quantized as digital sample points, e.g., one sample every two milliseconds, such that each sample point may be operated on individually. The geophone array is then moved to a new position and the process is repeated to obtain a 3D data volume for a seismic survey.
After exploration of an area is completed, data relating to energy detected at a plurality of geophones will have been recorded, where the geophones are located at varying distances from the shotpoint. The data is then reorganized to collect traces from data transmitted at various shotpoints and recorded at various geophone locations, where the traces are grouped such that the reflections can be assumed to have been reflected from a particular point within the earth, i.e., a common midpoint. The individual records or “traces” are then corrected for the differing distance the seismic energy travels through the earth from the corresponding shotpoints, to the common midpoint, and upwardly to the various geophones. This step includes correction for the varying velocities through rock layers of different types and changes in the source and receiver depths. The correction for the varying spacing of shotpoint/geophone pairs is referred to as “normal move out.” After this is done, the group of signals from the various midpoints are summed. Because the seismic signals are of a sinusoidal nature, the summation process serves to reduce noise in the seismic record, and thus increasing its signal-to-noise ratio. This process is referred to as the “stacking” of common midpoint data, and is well known to those skilled in the art. Accordingly, seismic field data undergoes the above-mentioned corrections, and may also undergo migration, which is an operation on uninterpreted data and involves rearranging of seismic information so that dipping horizons are plotted in their true location. Other more exotic known processing techniques may also be applied, which for example enhance faults and stratigraphic features or some other attribute, before the continuously recorded traces are reduced to vertical or horizontal cross sections or horizontal map views which approximate subsurface structure, and are usually in color.
Once the seismic data is satisfactorily processed to incorporate necessary corrections and desired enhancements, the geophysicist interprets the 3D seismic information. In general terms, interpretation involves deriving a simple plausible geological subterranean model that is compatible with the observed data. This model is never unique, and discovering it involves a sequence of somewhat arbitrary choices.
Despite significant progress in interactive 3D seismic interpretation systems, seismic workstations continue to rely on vertically and horizontally displayed planar slices of recorded data to provide almost all of the “working surfaces” for horizon and fault picking, and correlation. These planar slices provide only a limited perspective of the full three dimensional picture. Often animation of successive slices is required to provide information about the third dimension. However, animation intrinsically forces a three-dimensional interpretation based on the interpreter's memory of the changing picture through time, rather than on direct comparison and correlation of the data.
In observing and interpreting the seismic information displaying in a useful form is highly advantageous. Display systems are widely used in diverse image display applications, with most systems employing either planar or substantially planar display surfaces, i.e., flat wall screens which have an inherently limited field of view. While it is possible to extend the observers field of view by simply increasing the vertical and horizontal dimensions of the planar display screen, this expansion generally results in an unacceptable level of distortion of the image. In order to permit users to view objects peripherally, display technology has been developed which generally uses multiple projectors to project adjoining images on adjacent sections of a large wraparound screen so that observers can view objects with depth perception in 3D space.
Accordingly, four screen types are commonly used today to facilitate the many diverse image display applications. These four screen types are: 1) a flat wall, 2) multiple adjacent flat walls, 3) a dome, and 4) a curved wraparound panel, which can be semi-toroidal. All of these display surfaces can include stereo 3D graphics, and some applications require it to be successful.
The reason that no one screen type has persisted is that the different problems and purposes encountered with display systems are best individually addressed by only one of the various screen types mentioned above.
Accordingly, it is an object of this invention to provide a hybrid screen that combines the four screen types in a unitary structure.
A more specific object is to provide a hybrid screen for viewing various 3D combinations of wraparound, dome, flat wall and multi-wall type displays using a single video projector or multiple video projectors.
A still more specific object of this invention is to provide a portable, self-supporting rigid structure with a concave inner viewing surface, which is suitable for positioning on a desktop or on a moveable support table.
Yet another object is to provide an economical viewing surface that gives the viewer a sense of depth perception without requiring stereo projection and stereo glasses.
It is still another object of this invention to create a truly three-dimensional interactive graphic workstation to aid in geological interpretation of seismic data.
A more specific object of this invention is to visualize spatially correct seismic data on a large concave screen that facilitates horizon and fault mapping of seismic data.
Still another object is to provide a projection system for computer graphic images of seismic data that includes a portable self-supporting
Grismore John R.
Layton Jesse E.
Lucas William A.
Neff Dennis B.
Singleton Jacquelyn K.
Cross Ryan N.
Cruz Magda
Mahoney Christopher
Phillips Petroleum Company
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