Interferometric flying height measuring device including an addition of a spacer layer

A device for measuring a flying height of a read/write head above a rotating disk, comprising:

• a means for providing a light;
• an air-bearing slider for supporting the mad/write head on a cushion of fluid over the disk, said air-bearing slider having an underside;
• the disk including:
• a beam splitter layer, and
• a spacer layer provided on a top surface of said beam splitter layer;
• an interference pattern resulting from a phase difference in a plurality of electromagnetic wavelengths, said interference pattern being formed by a first portion of said light reflecting off of said beam splitter layer and a second portion of said light passing through said beam splitter layer and reflecting off of said underside of said air-bearing slider to thereupon recombine with said first portion of said light;
• wherein said spacer layer is provided to increase said phase difference so that each electromagnetic wavelength in said plurality of electromagnetic wavelengths is within the visible spectrum;
• and wherein said interference pattern is uniquely representative of a height of said air-bearing slider above said beam splitter layer;
• a slider structure having a bottom surface in contact with a top surface of said spacer layer;
• a reference interference pattern resulting from interferometry by a third portion of said light reflecting off of said beam splitter layer and a fourth portion of said light passing through said beam splitter layer and reflecting off of said bottom surface of said slider structure to thereupon recombine with said third portion of said light;
• wherein said reference interference pattern is uniquely representative of a thickness of said spacer layer;
• means for determining said height of said air-bearing slider above said beam splitter layer from said interference pattern and for determining said thickness of said spacer layer from said reference interference pattern;
• wherein the flying height of the read/write head is the difference between said height and said thickness.

A method of determining a flying height of a read/write head above a rotating disk, comprising the steps of:

• directing a light toward the disk, the disk having a beam splitter layer and a spacer layer thereon;
• obtaining a first interference pattern due to the reflection of said light off of said beam splitter layer and a top surface of said spacer layer;
• storing a digital representation of said first interference pattern in a computer memory;
• maintaining the read/write head over the disk on a cushion of fluid;
• directing said light toward the disk a second time;
• obtaining a second interference pattern due to the reflection of said light off of said beam splitter layer, said top surface of said spacer layer and an underside of said read/write head;
• comparing said first interference pattern to said second interference pattern to obtain a difference between said patterns;
• calculating by computer program the flying height of the read/write head above the disk based on said difference.

A method of determining a flying height of a head above a rotating disk having a beam splitter layer thereon, comprising the steps of:

• directing a light toward the disk;
• obtaining an interference pattern by the steps of:
• reflecting a first portion of said light off of the beam splitter layer,
• transmitting a second portion of said light through the beam splitter layer,
• increasing a path length of said second portion of said light by passing said second portion of said light through a spacer layer, and
• reflecting said second portion of light off of an underside of the head to thereupon recombine with said first portion of said light;
• determining a first height of said underside of the head above the beam splitter layer by analysis of said interference pattern;
• obtaining a reference interference pattern by the steps of:
• reflecting a third portion of said light off of the beam splitter layer,
• transmitting a fourth portion of said light through the beam splitter layer, and
• reflecting said fourth portion of light off of an upper surface of said spacer layer to thereupon recombine with said third portion of said light;
• and
• determining a second height of said upper surface of said spacer layer above the beam splitter layer by analysis of said reference interference pattern.

A method of determining a flying height of a read/write head over a rotating disk, comprising the steps of:

• directing a light toward the disk, the disk having a beam splitter layer thereon;
• obtaining an interference pattern by the steps of:
• reflecting a first portion of said light off of said beam splitter layer,
• transmitting a second portion of said light through said beam splitter layer,
• increasing a path length of said second portion of said light by passing said second portion of said light through a spacer layer, and
• reflecting said second portion of light off of an underside of the read/write head to thereupon recombine with said first portion of said light;
• determining a first height of said underside of said read/write head above said beam splitter layer by analysis of said interference pattern;
• obtaining a reference interference pattern by the steps of:
• reflecting a third portion of said light off of said beam splitter layer,
• transmitting a fourth portion of said light through said beam splitter layer, and
• reflecting said second portion of light off of an upper surface of said spacer layer to thereupon recombine with said third portion of said light;
• and
• determining a second height of said upper surface of said spacer layer above said beam splitter layer by analysis of said reference interference pattern.