Surface inspection by double pass laser doppler vibrometry
AssigneeMaxtor Corporation
InventorsPeter C. Jann, Wafaa Abdalla
Life of this patent
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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.
Claims20
A double pass apparatus for detecting defects on a disk surface, comprising:
- a light source that generates a light beam;
- a beamsplitter that splits the light beam into a first light beam portion and a second light beam portion;
- a modulator that modulates the second light beam portion into a frequency shifted modulated light beam for illuminating the surface of the disk,
- wherein the frequency shifted modulated light beam is twice reflected from the surface of the disk, doubling the frequency shift of a reflected light beam;
- and
- a polarizing beamsplitter that combines the first light beam portion with the reflected light beam portion providing an interference pattern.
A method for detecting defects on a disk surface, comprising:
- generating a light beam;
- splitting the light beam into a first light beam portion and a second light beam portion;
- modulating the second light beam portion into a frequency shifted modulated light beam for illuminating the surface of the disk,
- twice reflecting the frequency shifted modulated light beam from the surface of the disk, thereby doubling the frequency shift of a reflected light beam;
- and
- combining the first light beam portion with the reflected light beam portion providing an interference pattern.
Dependencies are inferred from the claim text.