Abstract: A measurement apparatus disclosed that has a radiation source configured to provide a measurement beam of radiation such that an individually controllable element of an array of individually controllable elements capable of modulating a beam of radiation, is illuminated by the measurement beam and redirects the measurement beam, and a detector arranged to receive the redirected measurement beam and determine the position at which the redirected measurement beam is incident upon the detector, the position at which the redirected measurement beam is incident upon the detector being indicative of a characteristic of the individually controllable element.

Abstract: This invention pertains to an improved technique of introducing an added insulative layer between the thermoplastic layer and the photoconductive layer of the thermoplastic photoconductive holographic recording medium. The added layer (pure PVK) is electrically insulating at temperatures used for thermal development to prevent decaying charge contrast during hologram development.

Abstract: This invention pertains to an improved thermoplastic holographic recording medium having an added layer between the thermoplastic layer and the photoconductor layer. The added layer is electrically insulating at temperatures used for thermal development to prevent decaying charge contrast during hologram development.

Abstract: A holographic recording is made on a tone wheel which is arranged to be driven by a capstan motor and capstan assembly. The holographic recording is a series of radial holograms on the tone wheel which recording is matched to the mechanical system driving the tone wheel by incorporating mechanical drive errors in the holographic recordings. The holographic recording on the tone wheel is read during subsequent operation of the motor/capstan/tone wheel assembly by a laser playback system to provide control signals for a motor energizing means to correct intrinsic drive system errors in a "sync-off-tach" type tape drive system.