Method and apparatus for in-situ measurement of head/recording medium clearance

The method for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising the steps of:

• producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• writing a plurality of signals of constant periodicity T.sub.1, T.sub.2 --T.sub.n over a predetermined area of the disk with said magnetic transducer,
• sensing a readback signal at a first wavelength W1=vxT.sub.1 from said predetermined area of said recording medium with said magnetic transducer to produce first signals;
• sensing a readback signal at a second wavelength W2=vxT.sub.2 from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• lowering the flying height of said magnetic transducer slider to substantially zero;
• sensing a readback signal at said lowered flying height from said predetermined area of said recording medium at said first and said second wavelengths to produce third and fourth signals;
• and
• calculating said first flying height as a constant times the product of two terms, the first of said two terms being the product of said two wavelengths divided by the difference between said two wavelengths, the second of two terms being the ratio of said first and second signals, expressed in decibels, subtracted from the ratio of said third and fourth signals, expressed in decibels.

The method for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising the steps of:

• producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• writing at least one signal of constant periodicity T over a predetermined area of the disk with said magnetic transducer, the readback signal resulting from reading said written signal having a spectral content comprising a plurality of different frequencies;
• sensing a readback signal at a first wavelength W.sub.1 =vT from said predetermined area of said recording medium with said magnetic transducer to produce a first signal;
• simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n.noteq.1, n is positive number) from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• lowering the flying height of said magnetic transducer slider to substantially zero;
• sensing a readback signal at said lowered flying height from said predetermined area of said recording medium simultaneously at said first and said second wavelengths to produce third and fourth signals;
• and
• calculating said first flying height as the product of two terms,
• the first term being a constant times said first velocity v divided by the difference in frequency between said first and said second signals,
• the second term being the difference of the ratio, expressed in decibels, of said first and said said second readback signals at said first and said second wavelengths and the ratio, expressed in decibels, of said third and fourth readback signals at said first and said second wavelengths.

The method for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising the steps of:

• producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• writing a plurality of signals of constant periodicity T.sub.1, T.sub.2 --- T.sub.n over a predetermined area of the disk with said magnetic transducer,
• sensing a readback signal at a first wavelength W1=vxT.sub.1 from said predetermined area of said recording medium with said magnetic transducer at said first flying height to produce a first signal;
• simultaneously sensing a readback signal at a second wavelength W2=vxT.sub.2 from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• and
• calculating the change in flying height from said first flying height as a constant times the product of two terms, the first of said two terms being the product of said two wavelengths divided by the difference between said two wavelengths, the second of two terms being the ratio of said first and second signals, expressed in decibels, subtracted from the ratio of said third and fourth signals, expressed in decibels.

The method for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising the steps of:

• producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• writing at least one signal of constant periodicity T over a predetermined area of the disk with said magnetic transducer, the readback signal resulting from reading said written signal having a spectral content comprising a plurality of different frequencies;
• sensing at a first time a readback signal at a first wavelength W1=vT from said predetermined area of said recording medium with said magnetic transducer to produce a first signal;
• simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n=2, 3--- n) from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• sensing at a second time a readback signal at a first wavelength W1=vT from said predetermined area of said recording medium with said magnetic transducer to produce a third signal;
• simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n=2, 3--- n) from said predetermined area of said recording medium with said magnetic transducer to produce a fourth signal;
• and
• calculating the change in flying height from said first to said second time as the product of two terms,
• the first term being a constant times said first velocity v divided by the difference in frequency between said first and said second signals,
• the second term being the difference of the ratio, expressed in decibels, of said first and said said second readback signals at said first and said second wavelengths and the ratio, expressed in decibels, of said third and fourth readback signals at said first and said second wavelengths.

The apparatus for measuring the flying height of a slider supporting a magnetic transducer in an operational moving magnetic storage system comprising:

• means for producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• means for writing a single signal of constant periodicity T over a predetermined area of said recording medium with said magnetic transducer;
• means for sensing a readback signal at a wavelength W from said predetermined area of said recording medium with said magnetic transducer to produce a first signal;
• means for continually lowering the flying height of said magnetic transducer slider;
• means for continually sensing a readback signal from said predetermined area of said recording medium as said flying height is lowered;
• means for determining the occurrence of contact of said magnetic transducer with said recording medium by sensing when the amplitude of said readback signal stabilizes;
• means for sensing the amplitude of said readback signal at contact to produce a second signal;
• and
• means for calculating the absolute value of said first flying height as the ratio, expressed in decibels, of said first and second signals times wavelength W divided by a constant.

The apparatus for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising:

• means for producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• means for writing a plurality of signals of constant periodicity T.sub.1, T.sub.2 --- T.sub.n over a predetermined area of the disk with said magnetic transducer,
• means for sensing a readback signal at a first wavelength W1=vxT.sub.1 from said predetermined area of said recording medium with said magnetic transducer to produce first signals;
• means for sensing a readback signal at a second wavelength W1=vxT.sub.2 from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• means for lowering the flying height of said magnetic transducer slider to substantially zero;
• means for sensing a readback signal at said lowered flying height from said predetermined area of said recording medium at said first and said second wavelengths to produce third and fourth signals;
• and
• means for calculating said first flying height as a constant times the product of two terms, the first of said two terms being the product of said two wavelengths divided by the difference between said two wavelengths, the second of two terms being the ratio of said first and second signals, expressed in decibels, subtracted from the ratio of said third and fourth signals, expressed in decibels.

The apparatus for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising the steps of:

• means for producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• means for writing at least one signal of constant periodicity T over a predetermined area of the disk with said magnetic transducer, the readback signal resulting from reading said written signal having a spectral content comprising a plurality of different frequencies;
• means for sensing a readback signal at a first wavelength W.sub.1 =vT from said predetermined area of said recording medium with said magnetic transducer to produce a first signal;
• means for simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n.noteq.1, n is positive number) from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• means for lowering the flying height of said magnetic transducer slider to substantially zero;
• means for sensing a readback signal at said lowered flying height from said predetermined area of said recording medium simultaneously at said first and said second wavelengths to produce third and fourth signals;
• and
• means for calculating said first flying height as the product of two terms,
• the first term being a constant times said first velocity v divided by the difference in frequency between said first and said second signals,
• the second term being the difference of the ratio, expressed in decibels, of said first and said said second readback signals at said first and said second wavelengths and the ratio, expressed in decibels, of said third and fourth readback signals at said first and said second wavelengths.

The apparatus for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising:

• means for producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• means for writing a plurality of signals of constant periodicity T.sub.1, T2--- T.sub.n over a predetermined area of the disk with said magnetic transducer,
• means for sensing a readback signal at a first wavelength W1=vxT.sub.1 from said predetermined area of said recording medium with said magnetic transducer at said first flying height to produce a first signal;
• means for sensing a readback signal at a second wavelength W2=vxT.sub.2 from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• and
• means for calculating the change in flying height from said first flying height as a constant times the product of two terms, the first of said two terms being the product of said two wavelengths divided by the difference between said two wavelengths, the second of two terms being the ratio of said first and second signals, expressed in decibels, subtracted from the ratio of said third and fourth signals, expressed in decibels.

The apparatus for measuring the flying height of a slider supporting a magnetic transducer in a moving magnetic storage system comprising:

• means for producing relative motion between said magnetic transducer and a magnetic recording medium at a first velocity v so that the resulting air bearing positions a magnetic transducer slider at a first flying height from the recording medium;
• means for writing at least one signal of constant periodicity T over a predetermined area of the disk with said magnetic transducer, the readback signal resulting from reading said written signal having a spectral content comprising a plurality of different frequencies;
• means for sensing at a first time a readback signal at a first wavelength W.sub.1 =vT from said predetermined area of said recording medium with said magnetic transducer to produce a first signal;
• means for simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n =2, 3 --- n) from said predetermined area of said recording medium with said magnetic transducer to produce a second signal;
• and
• means for sensing at a second time a readback signal at a first wavelength W.sub.1 =vT from said predetermined area of said recording medium with said magnetic transducer to produce a third signal;
• means for simultaneously sensing a readback signal at a second wavelength W.sub.n =nvT (n=2, 3--- n) from said predetermined area of said recording medium with said magnetic transducer to produce a fourth signal;
• and
• means for calculating the change in said flying height from said first to said second time as the product of two terms,
• the first term being a constant times said first velocity v divided by the difference in frequency between said first and said second signals,
• the second term being the difference of the ratio, expressed in decibels, of said first and said said second readback signals at said first and said second wavelengths and the ratio, expressed in decibels, of said third and fourth readback signals at said first and said second wavelengths.