Abstract: A device will assist in detecting man-made objects by using a liquid crystal retarder and a stationary polarizer. The liquid crystal retarder shifts impinging light 90 degrees between a nonrotated and a rotated mode. In the nonrotated mode, the retarder is essentially transparent, with the light passing through the retarder and through the polarizer. In the rotated mode, the impinging light will be rotated 90 degrees. An observer viewing the light passing through the polarizer will detect a difference or a flashing, with the rate depending upon the speed of oscillation between the rotated and nonrotated modes. The system can be employed with visible light optical systems such as binoculars, or with an infrared detector or video camera.

Abstract: A detection system will detect and identify self-propelled objects, such as missiles, which create a hot exhaust plume. The exhaust plume has radiation which modulates with a frequency range of interest. This frequency range can be detected with various detectors, such as an infrared detector, an ultraviolet detector, or even a radio frequency detector. Guided missiles have radiation frequencies which are much higher than the radiation frequencies of jet aircraft and of reciprocating engines. A filter will filter the output signals from the detector, and discard those outside of the frequency range of interest. A warning signal will indicate if frequencies are encountered within the frequency range of interest.

Abstract: A device will detect man-made objects by using a polarizer. The polarizer rotates about an axis in front of a lens array. The rotation of the polarizer alternately polarizes light received in proportion to the speed of rotation. This produces flashing in intensity for detecting the object as well as background rejection due to its lack of polarization. A man-made object having both horizontal and vertical surfaces of a type that will reflect light that can be polarized will provide flashing through the lens array as the polarizer passes through horizontal and vertical position. On the other hand, backgrounds don't have polarized components and won't flash. Attention is drawn to the man-made target. The background can also be electronically eliminated from the observed scene, permitting precise lock-on to the target.

Abstract: A device will detect man-made objects by using a polarizer mounted to a video camera. The polarizer rotates about an axis in front of a lens array of the video camera. The rotation of the polarizer alternately polarizes light received in proportion to the speed of rotation. This produces flashing in intensity for detecting the object as well as background rejection due to its lack of polarization. A man-made object having both horizontal and vertical surfaces of a type that will reflect light that can be polarized will provide flashing through the lens array as the polarizer passes through horizontal and vertical position. On the other hand, backgrounds don't have polarized components and won't flash. Attention is drawn to the man-made target. A high pass filter between the video signal processor and the monitor reduces background from the observed scene, permitting precise lock-on to the target.

Abstract: A search light employs variable polarization angles to enhance target identification. The search light shines a beam of light which may be directed across terrain. The beam of light is alternated in polarization angles at a rate of about five to twelve cycles per second. The alternating contrast in polarization angles produces flashing to an observer viewing certain targets struck by the beam of light. The flashing appears when striking man-made objects which tend to have a differential in polarized light between horizontal and vertical polarization. Natural objects do not appear to provide the flashing to the observer. The rotating polarization angles are accomplished in one instance by using a stationary polarizer and a liquid crystal retarder mounted in front of a light source. In another instance, the change in polarization angles is accomplished by rotating a polarizer in front of a light source. The light source may be infrared, visible or ultraviolet.

Abstract: A method and system of image modulation detection of an aircraft exhaust plume by time sequence differentiation is provided. The method comprises the steps of forming two sequential images of the field of view in which an exhaust plume to be detected is located, and forming a differential image from the sequential images showing components of the aircraft's exhaust plume that are modulating at a rate greater than the frame rate of the detection system. The nonmodulating components such as the sky hills, and even the missile body are eliminated from the differential image. Only the plume remains and only the plume is detected. Therefore there is not false alarm note. Each image is formed by a plurality of pixels, wherein each pixel images a portion of the field of view. A value is assigned to each pixel in each of the sequential images that corresponds to one or more characteristics of the pixel.