Abstract:
A projection system for presenting infrared scenes having biological and chemical agents, simulants and objects such as battlefield items. The generated scenes are primarily for the evaluation of infrared sensors, cameras and stand-off detectors. The system may have two or more projectors that combine various scenes into one scene having components with modified or imposed spectra signatures. Also, the system may generate a dynamic series of scenes that show synthetic scenarios of moving objects, agent clouds, non-toxic simulants and other items.

Description:
BACKGROUND 
   The invention pertains to infrared projectors and particularly to infrared projectors for generating a scene with various simulated objects in it for detection. 
   Some infrared projectors are designed to test infrared detectors. Such projectors provide various scenes to determine the sensitivity, speed and bandwidth of the infrared detectors. 
   SUMMARY OF THE INVENTION 
   The invention is an infrared projector or a combination of infrared projectors that may generate a synthetic scene having toxic chemical and/or biological agents, non-toxic agents or simulants. Agents may be a gas or liquid. “Fluid” is a generic term that includes liquids and gases as species. For instance, air, CO 2 , water and oil are fluids. The synthetic scene may be utilized for the test and evaluation of infrared chemical and biological detectors, among other things. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  reveals a two scene infrared projection system; 
       FIG. 2  is a graph of amplitude versus wavelength of a black body radiator; 
       FIG. 3  shows two scenes that are combined into one scene; 
       FIG. 4   a  shows illustrative gas spectra; 
       FIG. 4   b  shows combined black body and gas spectra; 
       FIG. 5  reveals a multiple scene infrared projection system; 
       FIG. 6  shows the various scenes associated with the projection system of  FIG. 5 ; 
       FIG. 7  reveals the system of  FIG. 5  with additional filters. 
       FIGS. 8   a  and  8   b  show illustrative examples of dynamics of a fluid composition in a filter. 
       FIG. 9  illustrates a single projector system having multiple filters. 
       FIG. 10  reveals a multiple projector system where each projector has multiple filters. 
       FIG. 11  is an illustrative example of combining a black body scene with another scene; and 
       FIGS. 12   a  and  12   b  show a projector system revealing dynamic scenes. 
   

   DESCRIPTION 
     FIG. 1  shows a multiple scene projection system  10 . Projector  11  may project an infrared radiation, light or scene  14  from an array  12  through a beam splitter or combiner  13  onto an infrared detector or camera  15 . Projectors  11  and  16  may present scenes via arrays  12  and  18 , respectively, which may be generated and coordinated by a computer  57 . A computer, though not necessarily shown, may present scenes or portions of them for various projector system configurations described below. Array  12  may provide a normal infrared signature. A projector  16  may project an infrared radiation, light or scene  17  from an array  18 . Radiation, light or scene  17  may go through a device, filter, cell or absorber  19  to beam splitter or combiner  13 . The terms “filter”, “cell” and “absorber” may be used interchangeably. The term “device” may be used in a context which may implicitly or explicitly identify that term. Radiation, light or scene  17  may go into device  19  and comes out as radiation, light or scene  20  which is combined with radiation, light or scene  14  by splitter or combiner  13  into radiation, light or scene  21  (henceforth referred to as a scene). Scene  21  is projected towards camera  15  as if it is from infinity. It&#39;s not like a projector&#39;s focusing the scene to be displayed on a screen. Scene  21  is essentially a virtual image. 
   Device  19  may have a toxic or non-toxic biological or chemical agent, simulant or a combination of fluids or substances. Device  19  may be an absorption cell through which scene  17  goes. A battle scene may be simulated with a gas in it having certain spectral characteristics. The test is to determine how well an infrared detector, such as camera  15 , can detect the gas and/or simulant of the cell in the projected scene. Additional absorption cells of various gases and/or simulants or mixtures of such gases and simulants may be inserted between array  12  and combiner  13 , and between array  18  and combiner  13 . 
     FIG. 2  is a graph of amplitude versus wavelength representing spectra  68  of a black body radiator. Projectors  11  and  16  may project scenes of the same bandwidth or different bandwidths. Or the projectors may be black body emitters having the spectrum shown in  FIG. 2 . If projectors  11  and  16  have different bandwidths, one may emit medium wavelength infrared radiation (MWIR)  22  and the other may emit long wavelength infrared radiation (LWIR)  23 , as an illustrative example. 
     FIG. 3  shows a scene  14  having a landscape  40  and a tree  41 , and a scene  20  having a building  42  and a cloud  27 . Scene  14  may be provided by projector  11  and scene  20  may be provided by projector  16 . Scene  20  may be projected through absorption cell  19  and the spectra of the gas in cell  19  may be superimposed on cloud  27  of scene  20 . Then scenes  14  and  20  may be put together by combiner  13  into a scene  21 . If the bandwidths of scenes  14  and  20  from projectors are the same then combiner  13  may be a “silvered” transparent medium that reflects about one-half of the light that impinges it. The remaining light goes through combiner  13 . If scenes  14  and  20  are of different bandwidths then combiner  13  may be a dichromic mirror that transmits a substantial portion of scene  14  and reflects a substantial portion of scene  20 . Combiner  13  may be some other mechanism, besides a mirror-like device, for combining scenes  14  and  20 . 
   Cloud  27  representing the gas may all originate in one projector or a part of cloud  27  may originate from another projector. Scenes  14  and  20  may be separated electronically, such as pixel by pixel, and combined optically, pixel by pixel. For increased contrast, the background temperature of the scene such as that in scene  14  may be lowed and cloud  27  temperature of scene  20  may be increased. The cloud representing the agent or gas may have a complex signature of spectra peaks or wavelengths as shown by example spectra  28  in the graph of  FIG. 4   a .  FIG. 4   b  is a graph of curve  67  combining black body spectra  68  of  FIG. 2  and gas spectra  28  of  FIG. 4   a . One test of infrared detector  15  would to be able to identify the gas in the scene having both black body and gas spectra. Detector  15  may need to be tuned to be spectrally sensitive to a particular gas or agent. 
   The agent or simulant being detected could be any gas, liquid, or substance. Device  19  may be a container having walls that are transparent. The pressure of the gas in the container may be set at an acceptable value for appropriate absorption. The absorption cross-section of a fluid in a cell may be noted. For example, there may be a mixture of gases in device  19 . These gases may have complex spectra that detector  15  may decipher and thus identify the gases and their respective quantities. Each additional array with a gas cell in front of it is filled with the proper agent or simulant (fluid or other substance) at the proper pressure to represent the integrated absorption-path length infrared signal attenuation. 
   A plurality of gases may be utilized in the scene projector system in another manner.  FIG. 5  shows a system  30  having three or more projectors that may be utilized. A third projector  31  with an array  32  could be added with a gas cell  33  for containing a second gas to be added to a scene  29  for camera  15  to detect. If desired, additional projectors may be added. A final projector  34  may be the second, third or N-th projector along with the respective array  35  and cell  36 . Projector system  30  may use silvered or the like splitters or combiners, or di- or multi-chromic splitters or combiners. Other forms of combining the scenes, such as light couplers, may be incorporated. 
   A scene  14  may be emanated by projector  11  via array  12 . Scene  14 , having a landscape  40  and a tree  41 , goes to combiner  13 , as shown in  FIG. 5 . The scenes and their combinations are revealed in  FIG. 6 . Projector  16  emanates a scene  17  via array  18  through gas cell  19 . A building  42  and a cloud  38  make up scene  20  as it emanates from cell  19 . Cloud  38  picks up the spectra signature of the gas in cell  19 . Scenes  14  and  20  are put together as a scene  39  by combiner  13 . Scene  39  goes to combiner  37 . Projector  31  emanates a scene  43  via an array  32  through gas cell  33 . A cloud  44  makes up scene  45  as it emanates from cell  33 . Cloud  44  picks up the spectra signature of the gas in cell  33 . Scenes  39  and  45  are put together as a scene  46  by combiner  37 . There may be more projectors as needed through N-th projector  34 . For this illustrative example, one may assume that only four projectors contribute to the resultant scene  21 . N-th projector  34  emanates a scene  47  having a cloud  48  via a cell  36 . Cloud  48  picks up the spectra signature of the gas in cell  36  as it emerges from cell  36  as a scene  49 . Scenes  46  and  49  are put together as scene  29  by combiner  50 . Actually, scene  29  is a combination of scenes  14 ,  20 ,  45  and  49 . There are at least three gases that camera  15  may detect and identify. Some or all of the gases may be different, the same or mixtures of various fluids. Of course, as indicated above, other fluids and/or objects may be added to resultant scene  29  from more projectors in system  30 . 
   As shown in  FIG. 7 , projector system  30  may have additional gas cells  75  and  76  in front of projectors  16  and  11 , respectively. Scene  14  in  FIG. 6  may have a superimposition of spectra of a gas in cell  76 . It may be over items  40  and  41 . Scene  20  after passing through cell  19  may have other fluid spectra imposed on it. Cell  75  may impose those spectra on scene  20 . For instance, cloud  38  may have a mixture of two gases in this IR scene simulation due to cells  19  and  75 . The percentage of the two gases relative to the total composition may vary over time. For example,  FIG. 8   a  may show a curve  77  of the percentage of a gas of cell  75  in cloud  38  over time. Another gas of cell  19  may be the remaining percentage of gas in the composition of cloud  38 . Cloud  38  may also have a percentage of water vapor. Cell  75  may have a mixture of various gases. The same may be true for cell  19 . Curves of  FIG. 8   b  reveal other examples of percentages  78  and  79  over time of gas compositions in a scene displaying objects such as cloud  38 . System  30  may have any arrangement of projectors and cells to compose IR scenes of various scenarios. 
     FIG. 9  shows an IR scene projection system  70  with array  82  having one projector  81  and a multitude of cells. In this instance, there are cells  83 ,  84  and  85  that may have any combination of fluids for a display of desired spectra for items in a projected IR scene  86  for detection by IR camera  15 . 
     FIG. 10  reveals a system  80  having a two-projector system, where each projector has several cells in front of it. Projector  11  with array  12  may emit a scene  14  that may have various spectra imposed on it by cells  87  and  88 . Likewise, IR projector  34  with array  35  may emanate a scene  47  that propagates through cells  36 ,  89  and  91  which impose certain spectra on IR scene  47 . The combination of various fluids in the cells may be selected to provide IR scenes with particular items exhibiting certain spectra, some of which may vary in percentage of composition over time. Scenes  14  and  47 , after passage through and modification by cells  87 ,  88 ,  36 ,  89  and  91 , respectively, may be put together into a resultant scene  72  by combiner  71 . Combiner  71  may be of any technology and is not restricted to mirror types of devices. Camera  15  may detect scene  72  for various purposes. 
     FIG. 11  is an illustrative scenario example of the combing of scenes. Array  12  may contain pixels like those, for example of a bolometer, except electric current is forced through some of the elements to make certain hot pixels in a pattern, resembling, for instance, a mobile military tank  53  which may be a black body in scene  51 . The pixel content of array  12  or  18  may be, whatever one&#39;s design calls for, 100×100, 240×320 or 480×640 pixels, and so forth. Array  18  may be constructed like and operate similar to array  12 . A cloud  54  may be presented in array  18  as scene  52  but that area of the cloud is a portion  69  of scene  51  that is missing. Portion  69  is not presented or lit up via the array pixels in scene  51 . Its absence may be represented by the shading. The rest of scene  51  may be present, including a portion of tank  53 . The shaded or darkened-out portion  69  may be the missing part of the scene and be an inactive portion of array  12  of pixels. Counterpart scene  52  may show cloud  54  having an outline of tank  53  which is in that portion of the scene. The resultant scene  56  may be the combination or sum of the actively presented portions of scenes  51  and  52 . If the darkened areas were added together into a scene, the resultant scene may be completely darkened. 
   Projectors  11  and  16  may present the respective scenes via the arrays, which may be generated and coordinated by a computer  57 . Cloud  54  may be a black body having a signature present with the signature of tank  53 . Scene  52  may be projected through cell  19  containing a gas. Cell  19  can be regarded as an “optical signature modifier”. Scene  51  and modified scene  52  may be combined at device  55 . Various kinds of media may be utilized to convey and combine scenes  51  and  52 . For instance, optical fiber may be used to transmit the modified infrared scene  52  and infrared scene  51  to device  55 . Device  55  may be an optical coupler that combines these scenes into a scene  56 . The spectral content of scene  51  may not be strictly black body in scene  56 . 
   The same principle of active (light) and inactive (dark) portions of the scenes, shown above with  FIG. 11 , may apply to  FIGS. 12   a  and  12   b . The scenes may be dynamic with moving objects and clouds of gas. The present projection can generate a synthetic battle field that is dynamic as well.  FIG. 12   a  may show tank  53  climbing a hill  64  in a scene  58  of array  12 . That may be the active part of the scene  58 . The inactive portion of scene  58  may be the shaded portion  69 . No signal would come from the projector to that area of the scene. The active portion of scene  59  may be cloud  54 . The remaining portion of array  18  is dark and inactive. If the two undarkened or lightened portions of scenes  58  and  59  are added together, then one may get the resultant scene  60 . If the two darkened areas of arrays  12  and  18  are added together, then one may get a completely darkened scene or pixel array. Cloud  54  may be in scene  59  of array  18 . Scene  59  may go through cell  19  and impose a spectra of the gas in cell  19  upon cloud  54  which appears in scene  60 . Scenes  58  and  59  may be combined at device  55  into scene  60 . Camera  15  may detect scene  60  with tank  53  on hill  64  and cloud  54  of agent gas. 
     FIG. 12   b  may show subsequent scenes  61  and  62  from the same projectors only moments later. These scenes in  FIGS. 12   a  and  12   b  may show the dynamics of the projection system with an animation of moving objects. In  FIG. 12   b , tank  53  may be going downhill and a truck  65  may appear in scene  61  of array  12 . In scene  62  of array  18 , cloud  54  may move towards the left. A new cloud  66  may appear in scene  62 . As scene  62  passes through device or cell  19  containing the gas, the spectra of the gas may be imposed on clouds  54  and  66 . In the combined scene  63 , there may be two vehicles and two clouds of the gas or agent. Infrared camera  15  may detect moving vehicles, shifting gas clouds and possibly other objects appearing and sometimes moving in dynamic infrared scene  63 . Various battle scene scenarios may be provided in an infrared scene for significant evaluation of camera  15 . Clouds  54  and  66  are not present in scene  61 . The absence of the clouds may be indicated by missing portions of the scenes as indicated by darkened areas  69  and  73 . Combining the lighter portions of scenes  61  and  18  may result in a complete scene  63 . If the darkened parts of scenes  61  and  62  or inactivated portions of arrays  12  and  18 , respectively, are combined or added together, then one may get a completely darkened screen or inactive array for a resultant scene (not shown). 
   Although the invention has been described with respect to at least one illustrative embodiment, many variations and modifications will become apparent to those skilled in the art upon reading the present specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.