Abstract: A system and method for pulse interval modulating signals in accordance with a code wherein the code resides in the spacing between adjacent pulses. The invention has particular utility in connection with laser designators and laser seekers and, while clearly not limited to this application, is disclosed hereinafter mainly in connection with laser designators and seekers. In connection with this laser environment, the invention may include a pulse interval modulation encoder for encoding the laser designator output signal and a pulse interval modulation decoder for decoding by the laser seeker of the encoded designator signal. The encoder preferably employs an ordered arrangement of unique pulse interval pairs which cyclically repeats after a relatively long time period. Because of the length of the time period and the apparent randomness of the intervals forming the unique interval pairs, the code appears to enemy countermeasures to be random.

Abstract: A system and method for pulse interval modulating signals in accordance with a code wherein the code resides in the spacing between adjacent pulses. The invention has particular utility in connection with laser designators and laser seekers and, while clearly not limited to this application, is disclosed hereinafter mainly in connection with laser designators and seekers. In connection with the laser environment, the system may include a pulse interval modulation encoder for encoding the laser designator output signal and a pulse interval modulation decoder for decoding by the laser seeker of the encoded designator signal. The encoder preferably employs an ordered arrangement of unique pulse interval pairs which cyclically repeats after a relatively long time period. Because of the length of the time period and the apparent randomness of the intervals forming the unique interval pairs, the code appears to enemy countermeasures to be random.

Abstract: A forward looking infrared system in which the usual FLIR is augmented by the addition of active laser illumination in order to enhance the FLIR's capability to discern in a scene certain details, such as manmade objects, especially under conditions of thermal washout. The laser is coded, and appropriate decoding electronics are provided to enable the FLIR to differentiate reflected laser radiation from thermal radiation of the scene. Therefore, it is unnecessary to endeavor to increase the brightness of the laser to an extent sufficient to overwhelm the natural thermal radiance level of the scene. Both types of radiation simultaneously impinge on a common detector, thereby eliminating the necessity for dual detectors and/or dual optics, and avoiding registration problems normally associated with the use of dual components.