Optical recording and playback apparatus using plural light spots
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsTomio Yoshida, Yoshinobu Nakata, Shunji Ohara, Toshio Satoh
Life of this patent
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Abstract
In an optical recording and playback disc apparatus, two light beams (l, m) are focused by a common focusing lens (108) onto an information track (51) of the optical recording disc, and the focused light means (l, m) form two light spots (L, M), the position thereof being controlled by a first tracking servo loop (115, 116 and 117), and furthermore, one (M) of the light spots is independently controlled from the other light spot (L) by a second tracking servo loop (120, 121 and 122).
Claims21
An optical recording and playback apparatus having plural light spots comprising:
- a first detecting means for detecting a tracking error signal of a first light spot,
- a second detecting means for detecting a tracking error signal of a second light spot,
- a common focusing means for forming said first and second light spots on an information track of an optical recording medium,
- a first driving means for driving said first light spot and second light spot simultaneously in a substantially perpendicular direction to an appointed information track,
- a first tracking servo loop for controlling the first driving means based on the output of the first detecting means,
- a second driving means for driving said second light spot in a substantially perpendicular direction to a specified information track by moving an optical means,
- a second tracking servo loop for controlling the second driving means based on the output of the second detecting means.
Apparatus for ensuring proper tracking in an optical recording and playback system, comprising
- first optical source means for providing a first optical beam having a first wavelength;
- second optical source means for providing a second optical beam having a second wavelength;
- a first beam splitter (105) for aligning said first and second beams along an optical axis;
- mirror means for directing said first and second beams toward an optical recording medium information tracks;
- focusing lens means for focusing both said first and second beams on said information track, light reflected from said information track guide passing back through said objective lens means in first and second reflected light beams, said reflected light beams being directed by said mirror means back along said optical axis;
- means for driving said focusing lens means;
- quarter wave plate means disposed along said optical axis, for transmitting said reflected beams;
- polarizing beam splitter means disposed along said optical axis, for passing said second reflected beam, and for directing said first reflected beam toward a first tracking error detection means;
- first tracking error detection means for receiving said first reflected beam, and for controlling said focusing lens means driving means to reduce tracking errors on said information track guide;
- a second beam splitter (119) for directing said second reflected beam toward a second tracking error detection means;
- and
- second tracking error detection means for receiving said second reflected beam, and for controlling said second optical source mans to reduce tracking errors on said information track guide.
Dependencies are inferred from the claim text.