Disc eccentricity measuring apparatus and method thereof and apparatus for recording and/or reproducing disc-shaped recording medium

Abstract

A recording and/or reproducing apparatus for a disc-shaped recording medium includes an optical head, a disc rotationally driving unit, a transfer unit, and an eccentricity amount measuring unit. The eccentricity amount measuring unit includes a controller and an error signal generator which generates an error signal exhibiting the amount of relative displacement of a light beam irradiated from the optical head onto the disc-shaped recording medium with respect to a track on such medium. The controller detects the peak and trough values of the error signal supplied from the error signal generator and compares a difference signal exhibiting a difference between the detected peak and trough values and a reference value to calculate the amount of eccentricity of the disc-shaped recording medium based on a comparison output signal.

What is claimed is:  
     
         1 . An recording and/or reproducing apparatus for a disc-shaped recording medium, comprising: 
 an optical head for irradiating an optical beam onto the disc-shaped recording medium;    rotationally driving means equipped with the disc-shaped recording medium for rotationally driving the disc-shaped recording medium equipped;    transfer means for relatively transferring said optical head and said rotationally driving means in a radial direction of the disc-shaped recording medium;    error signal generating means for generating an error signal exhibiting the amount of the relative shifting of a spot of a light beam irradiated from said optical head, which is produced on the basis of an output signal from said optical head, on the disc-shaped recording medium with respect to a track on the disc-shaped recording medium; and    control means which detects a peak value and a trough value of the error signal supplied from the error signal generating means and compares a difference signal exhibiting a difference between the detected peak value and the detected trough value with a reference value to generate a drive signal to be supplied to the transfer unit on the basis of a comparison output signal;    wherein the drive signal from said control means is supplied to said transfer means to shift said optical head and said rotationally driving means in the radial direction of the disc-shaped recording medium.    
     
     
         2 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 1   , wherein said control means comprises detecting means for sampling the error signal from said error signal generating means and for comparing a sampled value with a previously sampled value to detect said peak value and said trough value; calculating means for calculating an average value on the basis of said peak value and said trough value outputted rom said calculating means; and comparing means for comparing the average value outputted from said calculating means with a reference value.  
     
     
         3 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 2   , wherein said control means further comprises analog-to-digital converting means for converting the error signal from said error signal generating means into a digital error signal, wherein the digital error signal from said analog-to-digital converting means is supplied to said detecting means.  
     
     
         4 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 2   , wherein said detecting means samples the error signal from said error signal generating means and compares a sampled value with a previously sampled value in a time-axial direction to detect said peak value and said trough value.  
     
     
         5 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 2   , wherein said control means further comprises drive signal generating means for generating a drive signal on the basis of the comparison output signal from said comparing means.  
     
     
         6 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 5   , wherein said comparing means comprises a first comparator for comparing the average value supplied from said calculating means with a first reference value, and a second comparator for comparing said average value with a second reference value, wherein said drive signal generating means generates a first drive pulse signal on the basis of a comparison output signal supplied from said first comparator and a second drive pulse signal on the basis of a comparison output signal supplied from said second comparator.  
     
     
         7 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 5   , wherein said drive signal generating means outputs a drive pulse signal so that a voltage value is gradually lowered on the basis of the comparison output signal from said comparing means.  
     
     
         8 . An recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 5   , wherein said drive signal generating means outputs a drive pulse signal a voltage value of which is changed step by step on the basis of the comparison output signal from said comparing means and having a voltage value at a falling time being lower than that at a rising time.  
     
     
         9 . A method of measuring the amount of eccentricity of a disc-shaped recording medium, comprising: 
 a first step of generating an error signal exhibiting the amount of relative displacement of a spot of a light beam irradiated from the optical disc onto the disc-shaped recording medium with respect to a track on the disc-shaped recording medium on the basis of an output signal from an optical head;    a second step of detecting a peak value and a trough value of the error signal generated to generate a difference signal exhibiting a difference between the peak and trough values detected; and    a third step of calculating the amount of eccentricity of the disc-shaped recording medium on the basis of the difference signal.    
     
     
         10 . A method of measuring the amount of eccentricity of a disc-shaped recording medium as claimed in    claim 9   , wherein said second step comprises the steps of sampling the error signal generated means, comparing a sampled value with a previously sampled value, detecting said peak value and said trough value on the basis of a comparison result, and calculating an average value from a difference between said peak value and said trough value detected.  
     
     
         11 . A method of measuring the amount of eccentricity of a disc-shaped recording medium as claimed in    claim 10   , wherein said third step comprises the step of comparing the average value obtained in said second step with a reference value to calculate the amount of eccentricity of the disc-shaped recording medium.  
     
     
         12 . An apparatus for measuring the amount of eccentricity of a disc-shaped recording medium, comprising: 
 error signal generating means for generating an error signal exhibiting the amount of relative displacement of a spot of a light beam irradiated from an optical head onto the disc-shaped recording medium with respect to a track on the disc-shaped recording medium on the basis of an output signal from the optical head; and    calculating means which detects a peak value and a trough value of the error signal supplied from said error signal generating means to calculate the amount of eccentricity of the disc-shaped recording medium on the basis of a difference signal exhibiting a difference between the peak and trough values detected.    
     
     
         13 . An apparatus for measuring the amount of eccentricity of a disc-shaped recording medium as claimed in    claim 12   , wherein said calculating means comprises detecting means which samples the error signal from said error signal generating means and compares a sampled value with a previously sampled value to detect said peak value and said trough value, and average value calculating means for calculating an average value on the basis of the peak and trough values outputted from said detecting means, and comparing means for comparing the average value outputted from said average value calculating means with a reference value.  
     
     
         14 . A recording and/or reproducing apparatus for a disc-shaped recording medium, comprising: 
 an optical head for irradiating an light beam onto the disc-shaped recording medium, said optical head including an objective lens which converges the light beam onto the recording surface of the disc-shaped recording medium;    disc rotationally driving means equipped with the disc-shaped recording medium, for rotationally driving the disc-shaped recording medium equipped;    transfer means for transferring said optical head and said disc rotationally driving means relatively in a radial direction of the disc-shaped recording medium;    error signal generating means for generating an error signal exhibiting the amount of relative displacement of a spot of the light beam irradiated from the optical disc, which is generated on the basis of an output signal from said optical head, onto the disc-shaped recording medium with respect to a track on the disc-shaped recording medium;    shifting direction detecting means for detecting whether or not said objective lens shifts from an outer side of the disc-shaped recording medium toward the inner side thereof on the basis of the error signal outputted from said error signal generating means; and    control means which receives a detection signal from said shifting direction detecting means, said control means shifting said optical head and said disc rotationally driving means relatively by supplying a drive signal to said transfer means during a period for which the drive signal exhibiting that said objective lens shifts from the outer side of the disc-shaped recording medium toward the inner side thereof is supplied from said shifting direction detecting means to said control means.    
     
     
         15 . A recording and/or reproducing apparatus for a disc-shaped recording medium as claimed in    claim 14   , wherein said shifting direction detecting means comprises a detector which samples the error signal from said error signal generating means and compares a sampled value with a previously sampled value to detect said peak value and said trough value, wherein the shifting direction of said objective lens is detected on the basis of the peak and trough values outputted from said detector.