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US 5,684,782 AGranted
Use of a laser light source as a detector via a dithering modulation
AssigneeInternational Business Machines Corporation
InventorsLawrence Jacobowitz, Casimer Maurice DeCusatis
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Abstract
Laser light is focused in an accurate manner on selected layers in a multilayer optical disk recording system by means of an analysis of output electrical signals from a dithered source which results in the production of an electrical signal which is proportional to an amount by which the parts of the system are to be relatively moved in order to achieve the desired focus on one of the layers.
Claims5
A combined laser source and detector system comprising:
- a semiconductor laser light source which is capable of having its light output modulated by varying drive current applied to said semiconductor light source;
- means for varying the focus of light from said source, in an oscillatory manner, at a selected frequency;
- and
- means for detecting, in the range of said selected frequency, variations in current flowing through said semiconductor source, said variations being induced by laser light which is emitted from and is subsequently returned to said semiconductor light source.
1 more element
Dependencies are inferred from the claim text.