Is a
Patent attributes
Patent Jurisdiction
Patent Number
Patent Inventor Names
Wafaa Abdalla0
Peter C. Jann0
Date of Patent
June 30, 2009
0Patent Application Number
116549290
Date Filed
January 17, 2007
0Patent Primary Examiner
Patent abstract
A double pass apparatus for detecting defects on a disk surface includes a light source that generates a light beam and a beamsplitter that splits the light beam into a first light beam portion and a second light beam portion. A modulator is provided that modulates the second light beam portion into a frequency shifted modulated light beam for illuminating the surface of the disk. The frequency shifted modulated light beam is twice reflected from the surface of the disk, thus doubling the frequency shift of the reflected light beam. A polarizing beamsplitter combines the first light beam portion with the reflected light beam portion providing an interference signal.
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