Capacitance detection control circuit for positioning a magnetic head close to a magneto-optical disk

Claim 2

A magnetic head position control apparatus for controlling a magnetic head mounted in opposition to one side of a magneto-optical disk, comprising: a capacitance detection electrode mounted on said magnetic head and being in opposition to said one side of said magneto-optical disk; an oscillator circuit having predetermined oscillation characteristics and being connected to said capacitance detection electrode for producing an oscillation output having a frequency that varies in response to changes in capacitance between said capacitance detection electrode and said magneto-optical disk; a voltage controlled oscillator having oscillation characteristics substantially identical to those of said oscillator circuit and producing an oscillation output; a phase locked loop phase detection circuit including said voltage controlled oscillator and connected to said oscillator circuit for producing a phase detection output representing a detected phase difference between the oscillation output of said voltage controlled oscillator and the oscillation output of said oscillator circuit and wherein said phase detection output controls the oscillation output of said voltage controlled oscillator; and drive means connected to the phase detection output of said phase locked loop phase detection circuit for driving said magnetic head toward or away from a recording surface of said magneto-optical disk.

Claim 3

A magnetic head position control apparatus for controlling a magnetic head mounted in opposition to one side of a magneto-optical disk, comprising: a capacitance detection electrode mounted on said magnetic head and being in opposition to said one side of said magneto-optical disk; drive means connected to said magnetic head for driving said magnetic head toward or away from a recording surface of said magneto-optical disk; an oscillator circuit having predetermined oscillation characteristics and being connected to said capacitance detection electrode for producing an oscillation output having a frequency that varies in response to changes in capacitance between said capacitance detection electrode and said magneto-optical disk; a phase difference detection circuit having first and second inputs, said first input being connected to said oscillator circuit, and for detecting a phase difference between signals applied to said first and second inputs; a low pass filter having an input connected to an output of said phase difference detection circuit for passing low-frequency components of a signal applied to said input and having an output connected to said drive means; and a voltage controlled oscillator having oscillation characteristics substantially identical to those of said oscillator circuit having an input connected to said output of said low pass filter and having an output connected to said second input of said phase difference detection circuit for producing an output having a frequency of oscillation responsive to the level of the output of said low pass filter, whereby said phase difference detection circuit, said low pass filter, and said voltage controlled oscillator form a phase locked loop and said drive means is responsive to the output of said low pass filter.

Claim 4

A magnetic head position control apparatus for controlling a magnetic head mounted in opposition to one side of a magneto-optical disk, comprising: a capacitance detection electrode mounted on said magnetic head and being in opposition to said one side of said magneto-optical disk; drive means connected to said magnetic head for driving said magnetic head toward or away from a recording surface of said magneto-optical disk; an oscillator circuit having predetermined oscillation characteristics and being connected to said capacitance detection electrode for producing an oscillation output having a frequency that varies in response to changes in capacitance between said capacitance detection electrode and said magneto-optical disk; a phase difference detection circuit having first and second inputs, said first input being connected to said oscillator circuit, and for detecting a phase difference between signals applied to said first and second inputs; a low pass filter having an input connected to an output of said phase difference detection circuit for passing low-frequency components of a signal applied to said input and having an output connected to said drive means; and a voltage controlled oscillator having oscillation characteristics substantially identical to those of said oscillator circuit having an input connected to said output of said low pass filter and having an output connected to said second input of said phase difference detection circuit for producing an output having a frequency of oscillation responsive to the level of the output of said low pass filter, whereby said phase difference detection circuit, said low pass filter, and said voltage controlled oscillator form a phase locked loop and said drive means is responsive to the output of said low pass filter.