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 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 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 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.