Method and apparatus for detecting focussing error signal of objective lens

In a method for detecting a focussing error signal of an objective lens with respect to a video disc on which a light beam emitted from a laser light source is to be focussed as a light spot by the objective lens, a light flux reflected by the video disc is made incident upon a detection prism surfa...

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TORU
description In a method for detecting a focussing error signal of an objective lens with respect to a video disc on which a light beam emitted from a laser light source is to be focussed as a light spot by the objective lens, a light flux reflected by the video disc is made incident upon a detection prism surface which is set substantially at a critical angle with respect to a central light ray in the reflected light flux, and two light fluxes which situate on respective sides of a boundary plane including the central light ray and perpendicular to a plane of incidence, and are reflected by the reflection surface are separately received by two light receiving regions which are divided along a boundary plane including the central light ray reflected by the reflection surface and perpendicular to the plane of incidence. The focussing error signal is derived as a difference between output signals from the two light receiving regions.
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language eng
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subjects CLADDING OR PLATING BY SOLDERING OR WELDING
CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING
INFORMATION STORAGE
INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER
MACHINE TOOLS
METAL-WORKING NOT OTHERWISE PROVIDED FOR
OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
OPTICS
PERFORMING OPERATIONS
PHYSICS
SOLDERING OR UNSOLDERING
TRANSPORTING
WELDING
WORKING BY LASER BEAM
title Method and apparatus for detecting focussing error signal of objective lens
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