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Three Color Laser Interferometer

IP.com Disclosure Number: IPCOM000079535D
Original Publication Date: 1973-Jul-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Edwards, RB: AUTHOR

Abstract

This interferometer is used to measure tape-to-head air film thickness, by simultaneously illuminating this interface with pulsed laser energy of three different discrete wavelengths, thereby permitting unambiguous determination of the order of the interference fringes and determination of the thickness contour of the air film. The use of laser energy provides sharply defined interference fringes, due to the high temporal and spacial coherence of the three laser sources. Since the laser sources are pulsed to produce extremely short bursts of energy, the dynamically fluctuating air film thickness can be clearly viewed. This figure is not to scale, and is intentionally shown out of scale to enhance an understanding of this interferometer.

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Three Color Laser Interferometer

This interferometer is used to measure tape-to-head air film thickness, by simultaneously illuminating this interface with pulsed laser energy of three different discrete wavelengths, thereby permitting unambiguous determination of the order of the interference fringes and determination of the thickness contour of the air film. The use of laser energy provides sharply defined interference fringes, due to the high temporal and spacial coherence of the three laser sources. Since the laser sources are pulsed to produce extremely short bursts of energy, the dynamically fluctuating air film thickness can be clearly viewed. This figure is not to scale, and is intentionally shown out of scale to enhance an understanding of this interferometer.

Aluminized tape 10 is moved past stationary magnetic recording head 11, or a model thereof, at a controlled speed, which may include a start-stop sequence. Head 11 may include an aluminized reflecting surface. While the tape is moving, a hydrodynamic air film 12 is established between the tape and the head. The air film thickness is in the range of a few microinches and is affected by parameters such as head contour, tape speed and tape tension.

Three pulsed laser sources, 13, 14 and 15, operating in the red, green and blue wavelength regions, respectively, are synchronized to jointly illuminate the head/tape interface.

The output of each laser passes through a beam expander 16. The output of sourc...