Focus error detection using an equal path length lateral shearing interferometer

This invention provides an equal path length lateral shearing interferometer and its implementation in focus detection devices, particularly for optical data storage devices. The interferometer comprises a beamsplitter and two abutting roof prisms. Shifting the placement of a roof prism along an axi...

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Bibliographic Details
Main Authors GARDNER; TIMOTHY S, SHAFAAT; SYED T, STAHL; RONALD P
Format Patent
LanguageEnglish
Published 29.08.1995
Edition6
Subjects
INFORMATION STORAGE
INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER
PHYSICS
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Summary:This invention provides an equal path length lateral shearing interferometer and its implementation in focus detection devices, particularly for optical data storage devices. The interferometer comprises a beamsplitter and two abutting roof prisms. Shifting the placement of a roof prism along an axis orthogonal to the direction of light propagation and to the peak of the roof creates a lateral shear between the two output beams. Rotation a roof prism about this axis produces a tilt between the two output beams. This creates an interference pattern with a rotational orientation which is a function of the focus of the beam impinging on the optical storage medium. A pattern sensor is provided to adjust the focus of the beam in an accurate and dynamic manner.
Bibliography:Application Number: US19920972578