Dithered focusing systems

Claim 1

Apparatus for retrieving information stored in a plurality of optically readable information tracks formed in an information storage medium by an information recovery system, comprising: a radiation source for generation of a coherent beam of radiation; beam shaping means for directing the said beam of radiation to impinge upon the said information track in a reading beam spot; read detecting means for deriving an information signal from an information track; focusing means for indicating a vertical misalignment of the reading beam spot with respect to the information storage medium and for supplying a corresponding control signal indicative of the misalignment; transducer means for moving the reading spot longitudinally along the axis of the said coherent beam of radiation; means for generating an oscillatory dither signal for application to said transducer means; and lens focusing means separate from said transducer means and responsive to the said control signal for maintaining the said beam of radiation at the optimum focused position above the information track for retrieving the maximum amount of reflected radiation from the information track; and wherein: the said transducer means is responsive to the said oscillatory dither signal, and includes a piezoelectric member having conductive contacts, positioned upon at least two opposing surfaces of said member, said piezoelectric member functions as an optical element through which the coherent beam of radiation passes, the said piezoelectric member is physically deformed in proportion to the electrical field intensity applied to the said member, and the reading beam spot is removed longitudinally along the axis of the coherent beam of radiation as a direct result of the deformation of the said member and at a frequency determined by the said oscillatory dither signal.

Claim 5

An apparatus for use with a video disc player arranged to recover optically readable information stored in a record shaped disc, the said information stored in a pluralty of information tracks, the said apparatus comprising: a radiation source for generation of a coherent beam of radiation; beam shaping means for directing the said beam of radiation to impinge upon the said disc in a reading beam spot; read detecting means for deriving an information signal from the said information track; focus means for indicating a vertical misalignment of the reading spot with the information track and for supplying a corresponding control signal indicative of the misalignment; transducer means for moving the reading beam spot longitudinally along the axis of the coherent beam of radiation; means for generating an oscillatory dither signal for application to the said transducer means; and lens focusing means separate from said transducer means and responsive to the said control signal for maintaining the said beam of radiation at the optimum focus position above the information track for retrieving the maximum amount of reflected radiation from the information track; and wherein: the said transducer means is responsive to the said oscillatory dither signal and includes a piezoelectric member having conductive contacts, at least two per surface, positioned upon at least two opposing surfaces of said member, and said piezoelectric member functions as an optical element through which the coherent beam of radiation passes, the said piezoelectric member is physically deformed in proportion to the electical field intensity applied to said member, and the reading beam spot is moved longitudinally along the axis of the said coherent beam of radiation as a direct result of the deformation of said member and at a frequency determined by the said oscillator dither signal.

Claim 6

An apparatus for use with a video disc player arranged to recover optically readable information stored in a record shaped disc, the said information stored in a pluralty of information tracks, the said apparatus comprising: a radiation source for generation of a coherent beam of radiation; beam shaping means for directing the said beam of radiation to impinge upon the said disc in a reading beam spot; read detecting means for deriving an information signal from the said information track; focus means for indicating a vertical misalignment of the reading spot with the information track and for supplying a corresponding control signal indicative of the misalignment; transducer means for moving the reading beam spot longitudinally along the axis of the coherent beam of radiation; means for generating an oscillatory dither signal for application to the said transducer means; and lens focusing means separate from said transducer means and responsive to the said control signal for maintaining the said beam of radiation at the optimum focus position above the information track for retrieving the maximum amount of reflected radiation from the information track; and wherein: the said transducer means is responsive to the said oscillatory dither signal and includes a piezoelectric member having conductive contacts, at least two per surface, positioned upon at least two opposing surfaces of said member, and said piezoelectric member functions as an optical element through which the coherent beam of radiation passes, the said piezoelectric member is physically deformed in proportion to the electical field intensity applied to said member, and the reading beam spot is moved longitudinally along the axis of the said coherent beam of radiation as a direct result of the deformation of said member and at a frequency determined by the said oscillator dither signal.

Claim 9

A method for retrieving information stored in a plurality of optically readable information tracks formed in an information storage medium by an information recovery system, comprising the steps of: imaging a beam of radiation in a reading beam spot upon the said information track; deriving an information signal from said information track; generating a control signal indicative of vertical misalignment between the said information storage medium and the reading beam spot; generating an oscillator dither signal for moving the beam of radiation longitudinally along the axis of the said beam of radiation; and manipulating the said beam of radiation responsive to the said control signal for maintaining the beam of radiation at the optimum focused position above the information track for retrieving the maximum amount of reflected radiation from the information track; and wherein the said step of generating an oscillatory dither signal for moving the beam of radiation includes passing the beam of radiation through a piezoelectric member serving both as an optical element and as a deformable transducer, deforming the piezoelectric member proportionally to an electrical field intensity, and directing the said beam of radiation to move the reading beam spot longitudinally along the axis of the said beam of radiation at a frequency determined by the said oscillatory dither signal.

Claim 10

A method for retrieving information stored in a plurality of optically readable information tracks formed in an information storage medium by an information recovery system, comprising the steps of: imaging a beam of radiation in a reading beam spot upon the said information track; deriving an information signal from said information track; generating a control signal indicative of vertical misalignment between the said information storage medium and the reading beam spot; generating an oscillator dither signal for moving the beam of radiation longitudinally along the axis of the said beam of radiation; and manipulating the said beam of radiation responsive to the said control signal for maintaining the beam of radiation at the optimum focused position above the information track for retrieving the maximum amount of reflected radiation from the information track; and wherein the said step of generating an oscillatory dither signal for moving the beam of radiation includes passing the beam of radiation through a piezoelectric member serving both as an optical element and as a deformable transducer, deforming the piezoelectric member proportionally to an electrical field intensity, and directing the said beam of radiation to move the reading beam spot longitudinally along the axis of the said beam of radiation at a frequency determined by the said oscillatory dither signal.

Claim 13

A method for retrieving information stored in a plurality of optically readable information tracks formed in a record-shaped disc by an information recovery system, in particular, a video disc player, comprising the steps of: imaging a beam of radiation in a reading beam spot upon the said disc; deriving an information signal from an information track; generating a control signal indicative of a vertical misalignment between the said disc and the reading beam spot; generating an oscillatory dither signal for moving the beam of radiation longitudinally along the axis of the said beam of radiation at the optimum focused position above the information track for retrieving the maximum amount of reflective radiation from the information track; and wherein the said step of generating an oscillatory dither signal for moving the beam of radiation includes passing the beam of radiation through a piezoelectric member serving both as an optical element and as a deformable transducer, deforming the piezoelectric member proportional to an electrical field intensity, and directing the said beam of radiation to move the reading beam spot longitudinally along the axis of the said beam of radiation at a frequency determined by the said oscillatory dither signal.

Claim 14

A method for retrieving information stored in a plurality of optically readable information tracks formed in a record-shaped disc by an information recovery system, in particular, a video disc player, comprising the steps of: imaging a beam of radiation in a reading beam spot upon the said disc; deriving an information signal from an information track; generating a control signal indicative of a vertical misalignment between the said disc and the reading beam spot; generating an oscillatory dither signal for moving the beam of radiation longitudinally along the axis of the said beam of radiation at the optimum focused position above the information track for retrieving the maximum amount of reflective radiation from the information track; and wherein the said step of generating an oscillatory dither signal for moving the beam of radiation includes passing the beam of radiation through a piezoelectric member serving both as an optical element and as a deformable transducer, deforming the piezoelectric member proportional to an electrical field intensity, and directing the said beam of radiation to move the reading beam spot longitudinally along the axis of the said beam of radiation at a frequency determined by the said oscillatory dither signal.