Abstract: This rate dependent filter has a two-portion continuous filter function which optimizes noise filtering and minimizes detrimental lag or degradation characteristics. A first portion of the filter provides high filtering for low signal inputs below a first signal value. A second portion of the filter provides for a monotonically changing filter characteristic above the first signal values. The filter is especially useful in non-continuous transmissions, as radio, telephone, musical or other acoustical communication. It may also readily be applied to digital data transmission.

Abstract: A device which eliminates unwanted light rays and permits passage of desired light rays. For the purposes of this specification, the desired light rays are those which originate on a first side of a material capable of effecting light passage, and which pass through the material to a second side. Undesirable light rays are those originating on the second side of the material, which pass through the material to the second side of the material. The material, in the embodiment illustrated, is a beam splitter intended to present a desired scene to an observer. The preferred embodiment includes a linear polarizer and a quarter wave retarder which impart an elliptical polarization to the undesired light rays.