Patent ID: 6507419
Filing Date: 2003-01-14
Classification: G02B,G02F

Abstract:
An apparatus comprising:an electrically controllable optical filter comprising an electrically switchable holographic optical element, wherein the electrically switchable holographic optical element is switchable between active and inactive states, wherein the electrically switchable holographic optical element is configured to receive incident light and one or more control signals, wherein the electrically switchable holographic optical element outputs light in response to receiving the incident light and the one or more control signals, wherein the output light comprises only a portion of the incident light, wherein the portion of incident light varies according to the one or more control signals received by the electrically switchable holographic optical element; a light detector, wherein the light detector is configured to detect a portion of output light, wherein the light detector is configured to generate an output signal in response to detecting the portion of output light, and; a control signal circuit coupled between the light detector and the electrically switchable holographic optical element, wherein the control signal circuit is configured to generate the one or more control signals in response to the light detector generating the output signal.