Abstract:
A tiled projection display for use in an aviation environment which has fail operational capabilities without providing for fully redundant spare projectors. The system includes optics for redirecting light from one projector to a central position between an adjacent projector and involves the methods of switching light from one projector to project images for an additional adjacent projector in the event of a projector failure.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to panoramic cockpit displays and even more particularly relates to such displays having multiple projectors and a tiled display. 
     BACKGROUND OF THE INVENTION 
     In the past, designers of avionics displays have endeavored to provide larger and larger display devices to better provide for enhanced situation awareness for flight crews. The use of projection displays in cockpits is gaining many followers because of their recognized ability to provide panoramic displays. 
     While these displays have many advantages, they also have significant drawbacks. 
     Typically, the projectors used in projection display screens are relatively large, heavy and expensive. To provide a Fail Operational system is required in a typical aviation environment. One approach to achieving a Fail Operational projection display configuration that has been proposed is to include fully redundant projectors or include two projectors for each normal projector requirement. One projector is the main unit and the other is a spare. However, if a tiled display system were to have four segments, with each segment using an independent projector, then eight projectors would be needed to provide fully redundancy and Fail Operational capabilities. The extra cost, weight and space required for the extra four projectors can be substantial. 
     Consequently, there exists a need for improvement in Fail Operational capabilities of tiled projection displays. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide tiled projection displays having Fail Operational capabilities. 
     It is a feature of the present invention to utilize a shared projector in the event of a projector failure. 
     It is an advantage of the present invention to reduce the need for fully redundant spare projectors. 
     It is another feature of the present invention to include an optical switching system for redirecting the images normally emitted by a main projector. 
     It is another advantage of the present invention to minimize the number of mechanical parts required in an aviation display system. 
     The present invention is an apparatus and method for providing a projection image in a tiled projection system when a projector fails to operate which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features and achieve the already articulated advantages. The present invention is carried out in a “fully redundant projector-less” manner in a sense that the need for fully redundant components in a system having Fail Operational capabilities has been greatly reduced. 
     Accordingly, the present invention is a tiled projection display system which utilizes an optical switching arrangement where one projector can be used to provide a projected image for an adjacent segment of a tile projection display system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more fully understood by reading the foregoing description of the preferred embodiments of the invention, in conjunction with the appended drawing wherein: 
     The FIGURE is a simplified schematic diagram of a tiled projection image system of the present invention, showing light emanating from the projectors during normal use as dashed lines and with the double dotted and dashed lines used to show a light being redirected from one projector to illuminate multiple segments of a tile display system. 
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawing wherein like numerals refer to like matter throughout, there is shown a system of the present invention, generally designated  100 , having a first projector  110  and a second projector  120 , which may be any type of projector used for projecting portions of a tiled image, such projectors being well known in the art. Projectors  110  and  120  generally emit light to form a portion of an image  160  and  170  respectively. Images  160  and  170  may be projected on to various types of viewing surfaces, which are well known in the art, such as a diffuser disposed in the instrument panel of an aircraft. While the discussion herein is largely focused upon cockpit displays, because it is believed that many of the advantages of the present invention will have substantial utility in an aviation setting, the present invention is not limited to merely cockpit displays. Any environment where one or more of the benefits of the present invention can be enjoyed, is intended to also be included in the present invention. The diffuser or other optical device is chosen to provide a wide viewing angle to facilitate simultaneous cross-cockpit viewing from multiple members of the flight crew. Any viewing surface may be used, and several are well known in the art. Disposed between projectors  110  and  120  and their respective viewing surfaces is a mirror  112 , which is a mirror for directing the image emanating from projector  110  to a second failure mode mirror  122 , which is used to project the image onto segments  160  and  170 . It is generally desirable for the mirror  112  to not preclude illumination of segment  160  during normal operation. Mirror  112  may be physically moved into position from an adjacent location during times of failure of a neighboring projector  120 . Alternatively, the mirror  112  may be an opto-electrical device which has the property of a lens during normal operation and when subjected to control signals during failure mode operations, functions as a mirror. Disposed between mirror  112  and failure mode mirror  122  are optical devices  114  and  118  designed to transfer the projected image to a central location between projectors  110  and  120 , where it can be better positioned to provide a simultaneous image on segments  160  and  170  with minimal distortion. Optical device  114  may be a positive lens disposed near the mirror  112  for converting the diverging beam reflecting off mirror  112  to a parallel or reduced diverging beam to maintain the overall beam diameter as it traverses the distance between mirror  112  and failure mode mirror  122 . Optical device  118  may be a cylindrical lens disposed near the failure mode mirror  122  for converting the parallel beam to a diverging beam prior to reflection by failure mode mirror  122 . Only one side of the Fail Operational system is depicted, but it should be understood that a similar or nearly identical arrangement of mirrors and optical element could be associated with projector  120  to address a failure of projector  110 . The failure mode mirror  122  may be a shared adjustable (pivoting or otherwise) mirror disposed at the center point between projectors  110  and  120  or each failure mode path may provide its own mirror. In such cases, the paths may be slightly skewed or otherwise configured to accommodate the presence of the components relating to the other projector. All of the components of the present invention, including projectors  110  and  120 , mirror  112  and failure mode mirror  122 , and optical devices  114  and  118 , are individually well known in the art. 
     In operation, the apparatus and method of the present invention could function as follows: 
     An image to be projected upon a display surface is determined, the image is projected by at least two projectors, each projecting a separate portion of the tiled image, in the event of a failure of projector  120 , the mirror  112  is deployed into operation. The image emanating from projector  110  is changed to include the images which otherwise would have been projected by both projectors  110  and  120 . The new combined image is reflected off mirror  112 , converted into a parallel beam or reduced diverging beam by optical device  114 , traverses the distance to a central region between projectors  110  and  120  and is reconverted into a diverging beam by optical device  118  prior to reflection off failure mode mirror  122  which then illuminates both segments  160  and  170 . 
     In an optional mode, each point on an image would have a minimum of two horizontal pixels, or multiples of two pixels, while in normal operating mode. Upon failure, the graphics engine or other software located in projector  110 , and/or  120 , or elsewhere, may do a divide by two function, then the horizontal split of the image would retain a normal viewing ratio. 
     It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps and arrangement of the parts and steps thereof without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.