Emitter tracking system

Abstract

An improved emitter tracking system. In aspects of the present teachings, the presence of a desired emitter may be established by a relatively low-power emitter detection module, before images of the emitter and/or its surroundings are captured with a relatively high-power imaging module. Capturing images of the emitter may be synchronized with flashes of the emitter, to increase the signal-to-noise ratio of the captured images.

1 . An emitter tracking system, comprising:
 a signal detection module configured to detect an emitter signal generated by an emitter;   an imaging module configured to capture images of the emitter upon receiving an activation signal; and   a processor configured to receive the emitter signal from the signal detection module, analyze the emitter signal, and transmit the activation signal to the imaging module only if the emitter signal includes a predetermined signature.   
   
   
       2 . The system of  claim 1 , wherein the processor is configured to synchronize the imaging module with the emitter signal. 
   
   
       3 . The system of  claim 1 , wherein the processor is configured to cause the imaging module to capture sequential images of the emitter as the emitter alternates between an emissive state and a non-emissive state. 
   
   
       4 . The system of  claim 1 , wherein the processor is configured to construct a first subtracted image by electronically subtracting a first image of the emitter in a non-emissive state from a second image of the emitter in an emissive state. 
   
   
       5 . The system of  claim 4 , wherein the processor is configured to construct a second subtracted image by electronically subtracting a third image of the emitter in a non-emissive state from a fourth image of the emitter in an emissive state, and to construct a combined subtracted image by electronically adding the first and second subtracted images. 
   
   
       6 . The system of  claim 1 , wherein the signal detection module includes a filter configured to filter out electromagnetic radiation having wavelengths outside a desired range. 
   
   
       7 . The system of  claim 1 , wherein the signal detection module includes a filter configured to filter out signals having a flashing frequency profile insufficiently correlated to the predetermined signature. 
   
   
       8 . The system of  claim 1 , wherein the signal detection module has a first field of view and the imaging module has a second field of view substantially larger than the first field of view, the first field of view is sufficient to detect the emitter signal, and the second field of view is sufficient to capture images of the emitter and at least a portion of the emitter's surroundings. 
   
   
       9 . The system of  claim 8 , wherein the signal detection module includes a photodiode configured to receive image data from the first field of view, and the imaging module includes a focal plane array configured to receive image data from the second field of view. 
   
   
       10 . The system of  claim 1 , wherein the processor is configured to extract a flashing frequency profile from the emitter signal, compare the extracted profile to a desired profile, and transmit the activation signal to the imaging module only if the extracted profile substantially matches the desired profile. 
   
   
       11 . A method of tracking an emitter, comprising:
 detecting an emitter signal;   analyzing the signal to determine if the signal includes a signature corresponding to a particular emitter; and   capturing images of the emitter with the imaging module only if the signal includes the signature.   
   
   
       12 . The method of  claim 11 , wherein capturing images of the emitter is synchronized with a flashing frequency profile of the emitter signal. 
   
   
       13 . The method of  claim 11 , wherein capturing images of the emitter includes capturing sequential images of the emitter as the emitter alternates between an emissive state and a non-emissive state. 
   
   
       14 . The method of  claim 11 , further comprising constructing a first subtracted image by electronically subtracting a first image of the emitter in a non-emissive state from a second image of the emitter in an emissive state. 
   
   
       15 . The method of  claim 14 , further comprising constructing a second subtracted image by electronically subtracting a third image of the emitter in a non-emissive state from a fourth image of the emitter in an emissive state, and electronically adding the first and second subtracted images. 
   
   
       16 . The method of  claim 11 , wherein detecting the emitter signal includes filtering out electromagnetic radiation having wavelengths outside a desired range. 
   
   
       17 . The method of  claim 11 , wherein detecting the emitter signal includes filtering out signals having a flashing frequency profile insufficiently correlated to the signature. 
   
   
       18 . The method of  claim 11 , wherein detecting the emitter signal includes receiving the emitter signal at a signal detection module having a first field of view, and wherein capturing images of the emitter includes receiving image data at an imaging module having a second field of view substantially larger than the first field of view and including at least a portion of the emitter's surroundings. 
   
   
       19 . The method of  claim 18 , wherein the signal detection module includes a photodiode configured to receive image data from the first field of view, and wherein the imaging module includes a focal plane array configured to receive image data from the second field of view. 
   
   
       20 . The method of  claim 11 , wherein analyzing the signal includes extracting a flashing frequency profile from the signal and comparing the extracted profile to a desired profile.