Flying height tester and flying height test method

• US 20050117166A1
• Filed: 11/19/2004
• Published: 06/02/2005
• Est. Priority Date: 11/20/2003
• Status: Active Grant

• Current Assignee: International Manufacturing And Engineering Services Company Limited
• Original Assignee: International Manufacturing And Engineering Services Company Limited
• Inventors: Nozu, Takashi, Nozu, Yuka, Hisano, Teiji
• Granted Patent: US 7,206,077 B2
• Time in Patent Office: Days
• US Class Current: 356/507
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads
• CPC Class Codes: G11B 5/4555 by using a spin-stand, i.e. a spinning disc or simulator
• CPC Class Codes: G11B 5/5534 Initialisation, calibration, e.g. cylinder "set-up"
• CPC Class Codes: G11B 5/6005 Specially adapted for spacing from a rotating disc using a fluid cushion
• CPC Class Codes: G11B 5/6052 using optical means

Abstract

A flying height tester includes a glass disc facing a magnetic head slider under test; an optical system for guiding light to the glass disc so that multiple reflections of light occur between the glass disc and the magnetic head slider; a light sensor receiving reflection light from the glass disc to output light intensity data; and a processor which calculates back the flying height based on an output function of the light sensor. The processor calibrates intensity gain data and intensity offset data of the output function using the data obtained in a pseudo-zero state of the flying height. This pseudo-zero state is obtained by applying an index matching liquid between a first-calibration magnetic head slider, having the same optical constants as the magnetic head slider under test, and the glass disc, the index matching liquid having a refractive index identical to the glass disc.

Claims

1. A flying height tester comprising:

a glass disc positioned to face a magnetic head slider under test;

an optical system for guiding light to said glass disc so that multiple reflections of said light occur between said glass disc and said magnetic head slider under test;

a light sensor which receives reflection light from said glass disc to output light intensity data corresponding to an amount of said reflection light received; and

a processor which calculates back said flying height from said light intensity data of said magnetic head slider under test based on an output function of said light sensor, wherein said light intensity data and said flying height have a predetermined relationship expressed by said output function,

wherein said processor calibrates intensity gain data and intensity offset data of said output function using the light intensity data obtained in a pseudo-zero state of said flying height,

wherein said pseudo-zero state of said flying height is obtained by applying an index matching liquid between a first-calibration magnetic head slider, having optical constants substantially the same as those of said magnetic head slider under test, and said glass disc, said index matching liquid having a refractive index identical to that of said glass disc.

2. The flying height tester according to claim 1, wherein said processor further calibrates said intensity gain data and said intensity offset data with a peak value of said light intensity data on one of a peak-value-detecting magnetic head slider, said first-calibration magnetic head slider and said magnetic head slider under test,

wherein said peak-value-detecting magnetic head slider has optical constants substantially the same as those of said magnetic head slider under test.

3. The flying height tester according to claim 1, wherein said light sensor comprises a CCD camera capable of capturing said light intensity data, which corresponds to an amount of light received by a light-receptive area of said CCD camera, as a single image.

4. The flying height tester according to claim 1, wherein said optical system comprises a microscope through which light is guided to said glass disc.

5. The flying height tester according to claim 1, wherein a gap between said first-calibration magnetic head slider and said glass disc is filled with said index matching liquid so that no air gap is formed therebetween.

6. The flying height tester according to claim 3, wherein said CCD camera comprises a digital three-CCD camera.

7. The flying height tester according to claim 1, further comprising an X-Y stage to which an air spindle motor is mounted, wherein said glass disc is fixed to a rotary shaft of said air spindle motor to spin by said air spindle motor.

8. A flying height test method comprising:

preparing a magnetic head slider under test, and a first-calibration magnetic head slider having optical constants substantially the same as those of said magnetic head slider under test;

positioning said first-calibration magnetic head slider and a glass disc so as to face each other, and filling a gap between said first-calibration magnetic head slider and said glass disc with an index matching liquid to make a pseudo-zero state of said flying height, said index matching liquid having a refractive index identical to that of said glass disc;

guiding light to said glass disc so that multiple reflections of said light occur between said glass disc and said magnetic head slider, and making a light sensor receive reflected said light from said glass disc to obtain light intensity data in said pseudo-zero state of said flying height;

removing said first-calibration magnetic head slider, and replacing the glass disc with another glass disc that is dedicated for flying height calibration or measurement;

spinning said glass disc, and loading said test magnetic head slider on a face of said spinning glass disc;

guiding said light to said spinning glass disc so that multiple reflections of said light occur between said spinning glass disc and said magnetic head slider under test, and making said light sensor receive reflected said light from said spinning glass disc to obtain light intensity data of said magnetic head slider under test;

calibrating intensity gain data and intensity offset data of an output function of said light sensor with said light intensity data obtained in said pseudo-zero state of said flying height, wherein said light intensity data and said flying height have a predetermined relationship expressed by said output function; and

calculating back said flying height from said light intensity data on said magnetic head slider under test based on said output function after said calibrating step.

9. The flying height test method according to claim 8, further comprising:

preparing a peak-value-detecting magnetic head slider in advance which has optical constants substantially the same as those of said magnetic head slider under test; and

spinning said glass disc, and loading one of said peak-value-detecting magnetic head slider, said first-calibration magnetic head slider, and said magnetic head slider under test on a face of said spinning glass disc;

guiding light to said spinning glass disc so that multiple reflections of said light occur between said spinning glass disc and said one magnetic head slider to obtain a peak value of said light intensity data on said one magnetic head slider,

wherein said peak value is used to calibrate said intensity gain data and said intensity offset data.

10. The flying height test method according to claim 8, wherein a CCD camera capable of capturing said light intensity data, which corresponds to an amount of light received by a light-receptive area of said CCD camera, as a single image is used as said light sensor.

11. The flying height test method according to claim 8, wherein said glass disc is fixed to a rotary shaft of an air spindle motor so as to spin by said air spindle motor, wherein said air spindle motor is mounted on an x-y stage.

12. A flying height test method comprising:

preparing a magnetic head slider under test, and a first-calibration magnetic head slider having optical constants substantially the same as those of said magnetic head slider under test;

preparing a fixed glass disc and a rotary glass disc which is fixed to a rotary shaft of an air spindle motor, wherein said fixed glass disc and said air spindle motor are mounted on a common x-y stage;

positioning said first-calibration magnetic head slider and said fixed glass disc so as to face each other, and filling a gap between said first-calibration magnetic head slider and said fixed glass disc with an index matching liquid to make a pseudo-zero state of said flying height, said index matching liquid having a refractive index identical to that of said fixed glass disc;

guiding light to said fixed glass disc so that multiple reflections of said light occur between said fixed glass disc and said magnetic head slider, and making a light sensor receive reflected said light from said fixed glass disc to obtain light intensity data in said pseudo-zero state of said flying height;

removing said first-calibration magnetic head slider, and moving said x-y stage so that said rotary glass disc is available for testing instead of said fixed glass disc;

spinning said rotary glass disc, and loading said test magnetic head slider on a face of said spinning rotary glass disc;

guiding said light to said rotary glass disc so that multiple reflections of said light occur between said rotary glass disc and said magnetic head slider under test, and making said light sensor receive reflected said light from said rotary glass disc to obtain light intensity data of said magnetic head slider under test;

calibrating intensity gain data and intensity offset data of an output function of said light sensor with said light intensity data obtained in said pseudo-zero state of said flying height, wherein said light intensity data and said flying height have a predetermined relationship expressed by said output function; and

calculating back said flying height from said light intensity data on said magnetic head slider under test based on said output function after said calibrating step.