# US 5,351,225 A · Optical recording and reproducing apparatus having a plurality of light spots

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- Number: US 5,351,225 A
- Document ID: US5351225A
- Status: Granted
- Kind: A
- Application number: 07/877,429
- Filed: 1992-05-01
- Granted: 1994-09-27
- Earliest claimed: 1986-01-21
- Assignees: Matsushita Electric Industrial Co., Ltd.
- Inventors: Takashi Ishida; Shunji O'Hara; Kenzo Ishibashi; Toshio Satoh
- Web page: https://patentgrep.com/patent/US5351225A

## CPC

- G11B 7/0946: {specially adapted for operation during external perturbations not related to the carrier or servo beam, e.g. vibration}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

In an optical recording and reproducing apparatus which forms at least first and second light spots on a track of an optical recording medium to record, reproduce or erase information, a movable range of the second light spot is limited to less than one half of a track pitch, normal to the track, from the track to prevent tracks other than a target track from being miserased, misrecorded or misreproduced. When a deviation of the second light spot from the target track exceeds a predetermined amount, light emission of the second light spot is stopped to prevent a track other than the target track from being miserased, misrecorded or misreproduced. When the deviation of the second light spot from the target track exceeds the predetermined amount, the second light spot is returned to a neutral position to prevent a track other than the target track from being miserased, misrecorded or misreproduced.

## Claims

### Claim 1

An optical recording and reproducing apparatus having a plurality of light spots, comprising:
light spot forming means for forming at least a first light spot and a second light spot on one track of an optical recording medium,
first deviation detection means for detecting a first deviation of the first light spot from said track,
first drive means for moving the first light spot and the second light spot together in accordance with the first deviation,
second deviation detection means for detecting a second deviation of the second light spot from said track,
second drive means for moving the second light spot relative to the first light spot in accordance with second deviation, and
limit means for limiting a movable range of the second light spot by said second drive means to less than one half of a track pitch, normal to said track, less an allowable error of the positions of the first and second light spots formed by said light spot forming means, from the position of the second light spot taken when said second drive means is at a neutral position.

### Claim 2

An optical recording and reproducing apparatus having a plurality of light spots, comprising:
light spot forming means for forming at least a first light spot and a second light spot on one track of an optical recording medium,
first deviation detection means for detecting a first deviation of the first light spot from said track,
first drive means for moving the first light spot and the second light spot together in accordance with the first deviation,
second deviation detection means for detecting a second deviation of the second light spot from said track,
second drive means for moving the second light spot relative to the first light spot in accordance with the second deviation, and
limit means for limiting a movable range of the second light spot to less than one half of a track pitch, normal to said track, from the position of the second light spot when said second drive means is at a neutral position,
wherein said limit means is a mechanical means.