Abstract:
An infrared detection system for seeing multiple pixel scenes and/or connecting multiple detectors, within each communications path, includes a data processor, optical toggles and/or electrical switches, and a large number of pixels and detectors. For the spatial net, the data processor sends signals to the optical toggle and electric switches connecting neighboring pixels and other detector elements to the data processor. A single communications path serves several pixels and detector elements thereby minimizing interconnection congestion from the pixels to the processing circuitry.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to data communications between an array of infrared detectors and a multi-layer processing module, and more particularly to a spatial interconnect net with optical toggles to see multiple pixel scenes and electrical switches to connect multiple detectors within each communications path.  
         BACKGROUND OF THE INVENTION  
         [0002]    Space-based surveillance systems use infrared detectors coupled to computerized data processors for monitoring heated objects and their movements in the atmosphere below and on the ground. The infrared spectrum covers a wide range of wavelengths, from about 0.75 micrometers to 1 millimeter. The function of infrared detectors is to respond to energy of a wavelength within some particular portion of the infrared region. Heated objects will dissipate thermal energy having characteristic wavelengths within the infrared spectrum. Different levels of thermal energy, corresponding to different sources of heat, are characterized by the emission of signals within different portions of the infrared frequency spectrum. Detectors are selected in accordance with their sensitivity in the range of interest to the designer. Similarly, electronic circuitry that receives and processes the signals from the infrared detectors is also selected in view of the intended detection function.  
           [0003]    Current infrared detection systems incorporate arrays of large numbers of discrete, highly sensitive detector elements the outputs of which are connected to sophisticated processing circuity. By rapidly analyzing the pattern and sequence of detector element excitations, the system circuitry can identify and monitor sources of infrared radiation. The outputs of the detectors must undergo a series of processing steps in order to permit derivation of the desired information. The more fundamental processing steps include preamplification, tuned bandpass filtering, clutter and background rejection, multiplexing and fixed noise pattern suppression. By providing a detector connecting module that performs at least a portion of the signal processing functions within the module, i.e. on integrated circuit chips disposed adjacent the detector focal plane, the signal from each detector need be transmitted only a short distance before processing. As a consequence of such on-focal plane or “up front” signal processing, reductions in size, power and cost of the main processor may be achieved.  
           [0004]    Up front signal processing also helps alleviate performance and reliability problems associated with manufacturing high packing density electronics assemblies. An important part of the up front data processing are temporal net and spatial nets for filtering the data and discarding false readings. Temporal nets simply compare the present frame of data in time to each of multiple past frames of data. More problematic, is setting up a spatial net to compare values from neighboring detector elements. Multiple paths of communication from each of the detector elements to several locations on the processing circuitry are difficult, especially if the several locations are on multiple chips in a multi-layer stack. A high number of criss-crossing electrical connections may also develop an electrical magnetic field that interferes with data transmission. It is desirable to provide a spatial net that accomplishes the necessary interconnects, while minimizing the complexity of the communication paths.  
           [0005]    The prior art has attacked this problem by providing increasing numbers of miniaturized solder contacts on the edge of the chip stack through electron-beam lithography. Also, “optronic” components are under development that will provide for optical interconnections, but the level of miniaturization attained is not yet comparable to electronic components. Methods are needed with available technology that reduce the complexity of the interconnections.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention specifically addresses and alleviates the above-mentioned deficiencies associated with the prior art. The present invention generally comprises the reading of multiple pixel scenes and connecting of multiple detector elements within a single communications path to a data processor. The data processor controls a number of optical toggles and electrical switches of the interconnect net and analyzes the detector data.  
           [0007]    More particularly, the optical spatial interconnect net of the present invention may include optical toggles which move the optical communication path from one pixel scene to another upon command of the data processor. The interconnect net may further include electric switches which alternate the communication path from one detector element to another upon command of the data processor. This architecture provides a single communications path operative to alternately receive signals from a plurality of pixels. This architecture further provides a single communications path operative to alternately relay data from a plurality of detector elements. The number of interconnections that must be made between the multiple pixel scenes and the arrays of infrared detectors to the data processors are minimized.  
           [0008]    A communication path to a selected pixel is set up by first sending a signal from the data processor to an optical toggle, moving the toggle to put the pixel in optical communication with a detector element. Then, closing a switch completes the electronic circuit between the detector element and the data processor, sending a signal to the data processor. A spatial net is provided by repeating the above steps for neighboring pixels. Repeating the above steps for other switches connected to the same pixels provides redundancy and a means of passing comparative calibration information.  
           [0009]    These, as well as other advantages of the present invention will become more apparent from the following description and drawings. It is understood that changes in the specific structure shown and described may be made within the scope of the claims without departing from the spirit of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of an infrared detector system payload disposed within an orbiting satellite;  
         [0011]    [0011]FIG. 2 is an exploded perspective view of the focal plane of the infrared detector system;  
         [0012]    [0012]FIG. 3 is a block diagram illustrating the method of toggling connections between multiple pixels to provide spatial comparisons;  
         [0013]    [0013]FIG. 4 is a wiring diagram of the optical spatial interconnect net of the infrared detection system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    The detailed discussion set forth below in connection the appended drawings is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the functions and sequence of steps for constructing and operating the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention.  
         [0015]    [0015]FIG. 1 of the drawings generally illustrates an infrared detector system payload disposed within an orbiting satellite system. The satellite system generally incorporates an optical system which focuses objects within the field of view on the surface of a detector focal plane. The focal plane is formed of electro-optical components adapted to detect objects within the field of view and to generate electrical signals responsive to images of those objects. By analyzing the pattern of information produced by the individual detector elements and correlating that information over time in various ways a detailed image of the area within the field of view can be generated. The precise satellite structure, the structure of the detector modules used to form the detector focal plane, and the precise manner in which the information from the detector elements is processed is not intended to be a limitation with respect to the present invention, which, in its broader aspects, has application to all types of satellite and detector systems. Thus, the reference to particular types of detector modules is intended as exemplary of one manner in which the present invention may be utilized.  
         [0016]    [0016]FIG. 1 more particularly illustrates a satellite  11  shown in Earth orbit. The portions of satellite  11  of interest herein include an optical system  13 , detector focal plane  15  and data processor  17 . The optics  13  function to image objects within the satellite field of view on the surface of the focal plane  15 . The focal plane  15  may be any of a variety of constructions, utilizing a variety of different materials suitable to operate in a space environment. The focal plane  15  functions to derive electrical signals from the image focused by optical system  13  and to communicate such electrical signals to the data processor  17 . The data processor  17  directs interrogation of the focal  15  and is controlled by signals from ground operations  19 .  
         [0017]    Referring to FIG. 2 a mosaic focal plane  20  useful in the application illustrated at FIG. 1 is shown in more detail. As shown at FIG. 2 the focal plane  20  is defined by a housing  21  which holds a substantial number of individual subarrays  23  disposed to have edge portions that collectively form the front face of the focal plane  20 . Each subarray  23  is comprised of a plurality of modules  25 , with each module  25  comprised of a plurality of separate layers  27 . Integrated circuits  29  may be mounted on the layers  27  to facilitate on-focal-plane processing of data and interrogation of detector elements. Detector arrays  31 , each containing a plurality of detector elements are formed along a vertical edge surface of the modules. A buffer board  33  may be disposed intermediate the front face of module  25  and the detector arrays  31  to facilitate interconnection.  
         [0018]    Each of the detector arrays  31  has a multiplicity of individual detector elements  35  for the multiplicity of pixel scenes  37  in the field of view. To accomplish the up-front processing on the focal plane  15  requires a large number of electrical connections between the detector elements  35  and the multi-layer module  25 . To improve the performance and reliability of the up-front processing, temporal nets and spatial nets are set up, further increasing the amount of data transmitted and the number of connections required. Also, to improve the reliability of the up-front processing, redundant connections are desirable. The temporal net (not shown) compares the present frame of data in time from detector elements  35  to each of multiple past frames. The temporal net is configured by comparing multiple analog values stored (in analog or digital form) on capacitors of the integrated circuits  29 . The spatial net compares values from neighboring detector elements  35 . This typically requires additional connections between the detector elements  35  and the processing circuity in the module  25 .  
         [0019]    The spatial interconnect  41  net and method of alternating communication paths between multiple pixel scenes  37  and multiple detector elements  35  of the present invention are illustrated in FIGS. 3 and 4 which depict the presently preferred embodiment of the invention.  
         [0020]    First referring to FIG. 3, the spatial interconnect net  41  may be further described. The preferred embodiment shows a scheme of an optical toggle  39  having multiple pixels  37  within its field of view. Each detector circuit  47  is shown containing eight vertically aligned pixels  37 , though many different schemes could be set up. The spatial net  41  for a given pixel  35  is the eight surrounding pixels  37 , represented by the compass headings. The data processor  17  obtains a reading from a selected pixel  37  by designating the appropriate detector circuit  47  and optical toggle  39  position. The arrows in FIG. 3 represent tracking of a moving target either in a northerly or southerly direction.  
         [0021]    Next referring to FIG. 4, the wiring for three detector circuits  47  of the spatial interconnect net is shown. Each of the detector circuits  47  include a connection to the data processor  17 , an amplifier  43 , and a switch  45 . Upon the data processor  17  sending a signal to close a given switch  45 , the associated detector  35  is electrically connected to the data processor  17 . The amplified signal from that detector  35  is received at the data processor  17 . The arrows in FIG. 3 represent the detectors  35  viewing the pixels  37  below.  
         [0022]    The preferred embodiment further provides that each pixel  37  may be seen by two detector elements  35 . This is achieved by providing overlapping coverage of the pixels  37  by the detector elements  35 . Further, coverage of pixels  37  by neighboring detector elements  35  may be staggered (see FIG. 1). In this way adjacent detectors  35  may not cover pixels  37  within the same spatial comparison net  41 .  
         [0023]    It is understood that the optical spatial interconnect net and method for toggling communications between multiple pixels  37  and switching connections between multiple detectors  35  described herein and shown in the drawings represents only a presently preferred embodiment of the invention. Indeed, various modifications and additions may be made to the embodiment without departing from the spirit and scope of the invention. These and other modifications may be obvious to those skilled in the art and may be implemented to adapt the present invention for use in a variety of different applications.