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.

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.

Abstract: An optical system is provided in which flare is prevented and, when the light reflected from a reflection component is modulated by a photoelastic phenomenon, the effect of the modulation on the measurement of the intensity of the reflected light can be eliminated, and, further, a flying height tester for a magnetic head is provided using such optical system. A multilambda plate is provided in the flare-prevention optical system for allowing the light reaching a reflection component and the light reflected from the reflection component to pass, and for allowing the phase difference between the ordinary ray and the extraordinary ray to vary by 2.pi. or more depending on the wavelength of light. Since the light passed through the multilambda plate only varies in the peak position and the peak height varies little even if the light has experienced modulation, no error occurs in the spectrum intensity of the light. A depolarizer may be substituted for the multilambda plate.

Abstract: This invention provides a method and apparatus for accurately measuring the flying height of a magnetic head at high speed by using a white lamp and a color CCD camera. The invention entails substituting tentative refraction coefficients and extinction coefficients representative of colors in theoretical equations expressing the relationship between interference light intensity and flying height, thereby optimizing the parameters by non-linear regression. The flying height of a magnetic head is measured by using the coefficient thus determined. Also, this invention enables determination of flying height at very high speed through effecting the above optimization in consideration of constants associated with the shape of the head under consideration, and adapting the above theoretical equations.

Abstract: A high-sensitivity apparatus having simple constitution that measures the flying height of a magnetic head. Light emitted from a white light source 25 is directed to the gap between a disk 23 and a head 21, and subjected to multiple reflection between the disk 23 and the head 21. Reflected light from an opaque object, which may be either the disk 23 or the head 21, is divided into at least three components having respective wavelength regions which are directed to different photodetectors 35, 36, and 37 for the respective wavelength regions. An estimation device 38 estimates the flying height of the head according to the least-square method from the outputs of the photodetectors using functions prepared in advance for the respective wavelength regions, and correlates the disk-head gap and the reflected light intensities detected by the respective photodetectors. Real-time calculation according to the least-square method is performed by means of a table look-up technique or a tracking servo technique.

Abstract: A print actuator for a dot matrix printer has a stator with a frame, at least two ferromagnetic poles and at least one permanent magnet; and at least one electromagnetic coil surrounding the magnet. The magnet can generally hold an armature in a home position by its magnetic flux until the coil is energized at which point the magnetic flux of the magnet is neutralized by the magnetic flux of the coil and the armature is substantially released of influence from the magnet's hold.