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Optical storage apparatus

  • US 6,118,739 A
  • Filed: 01/09/1998
  • Issued: 09/12/2000
  • Est. Priority Date: 08/05/1997
  • Status: Expired due to Fees
First Claim
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1. An optical storage apparatus comprising:

  • a positioner for moving an objective lens to irradiate a light beam to a medium in a direction traversing tracks on the medium;

    an access control unit for moving the light beam from an optical unit to a target track so as to be ontracked by a driving control of said positioner;

    a linear velocity control unit for variably controlling a rotational speed of said medium in accordance with a radial position of the medium so that a linear velocity in a circumferential direction at the irradiating position of said light beam is set to a constant value;

    an eccentricity measuring unit for measuring an eccentricity amplitude of one rotation of said medium and an eccentricity phase for a start position of one rotation;

    an eccentricity memory in which a region from the start position to an end position of one rotation of said medium is divided into a plurality of regions every predetermined rotational angle, addresses are sequentially allocated to said plurality of regions, and a sine value of each rotational angle which is increased every said predetermined rotational angle has been stored in each of said addresses;

    a read control unit for forming an address in said eccentricity memory corresponding to a rotating position of the medium where the light beam is irradiated at present while using the start position of one rotation of said medium as a reference and for reading out the correspondence sine value from said eccentricity memory by a designation of said address, said read control unit including;

    a rotational period detecting unit for detecting a medium rotational period according to the position in the radial direction of the medium where the light beam is irradiated at present,a 1-address rotating time detecting unit for detecting a 1-address rotating time indicative of a medium rotating time of one address by dividing said rotational period by the number of addresses in said eccentricity memory,a medium present position detecting unit for detecting a medium present position showing the rotating position of the medium where the light beam is irradiated at present while using the start position of one rotation of said medium as a reference, anda memory reading unit for comparing an address upper limit value in said eccentricity memory which is expressed by using said 1-address rotating time and is read out at present with said medium present position where the light beam is irradiated at present, for designating the same address and for reading out the sine value from said eccentricity memory when said medium present position is less than said address upper limit value, and for updating the address to an address obtained by adding "1" to the present address and for reading out the sine value from said eccentricity memory when said medium present position reaches said address upper limit value; and

    an eccentricity correcting unit for obtaining an eccentricity amount on the basis of the sine value read out by said read control unit and a measurement value measured by said eccentricity measuring unit, thereby controlling said positioner so as to set off said eccentricity amount.

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