Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1993-06-16
1998-02-03
Tran, Thang V.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 4426, G11B 700
Patent
active
057152233
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for measuring the deviation between an arcuate centerline of two adjacent grooves on both sides of a recording track and a control prepit pattern of an optical disc of the sample servo tracking system.
BACKGROUND ART
Information signals are recorded on the optical disc by radiating a light beam from an optical pickup unit to the disc which is rotated at a constant linear velocity or a constant angular velocity. For accurate recording of the information signals, it is necessary for the light beam to track the recording track accurately.
Consequently, a variety of tracking systems, inclusive of the sample servo tracking system, have been proposed.
With the sample servo tracking system, tracking is achieved by a control prepit pattern formed on a disc substrate, instead of by a so-called pre-groove formed on the disc substrate. Consequently, in the optical disc of the sample servo tracking system, clock pits for clock synchronization and wobble pits for deriving tracking error signals are formed as a pre-pit pattern along the centerline of a recording track at the time of molding of the disc substrate.
Meanwhile, it has been pointed out with the optical disc of the sample servo tracking system that ghost pits or unusual polarization tends to be produced at the time of molding of the disc substrate. The present Assignee has already proposed providing grooves in a data area in the optical disc of the sample servo tracking system for overcoming these inconveniences.
The disc substrate provided with these grooves may be detached easily from a stamper at the time of molding, while being free from ghost pits or unusual polarization, so that an optical disc exhibiting superior optical characteristics may be produced.
When preparing the optical disc provided with these grooves, since it is impossible to cut the prepit pattern and the grooves in the data area simultaneously by a single laser beam, it becomes necessary to split a cutting laser beam into a sub-beam for forming the prepit pattern and another sub-beam for cutting the groove.
However, since the grooves are spaced apart a distance of an order of 1.5 .mu.m, it is extremely difficult to match the relative position of the two sub-beams so that the clock pits are accurately positioned at the center of the lands between the grooves.
It is therefore necessary to measure the deviation between the pits and the grooves after cutting to feed it back to a mastering process to adjust the relative position between the two sub-beams to assure cutting in as accurate a manner as possible.
However, there have not been made any investigations into the art of measurement of the deviation and hence the method for measuring the deviation has not been established to date.
In view of the above-depicted status of the art, it is an object of the present invention to provide a method for measuring the deviation between the center of wobble pits and the center of the grooves in a simplified manner for feeding the measured value of the deviation promptly to a mastering process.
DISCLOSURE OF THE INVENTION
For accomplishing the above object, the present invention provides a method for measuring a deviation between the centerline between circumferentially extending grooves and a control prepit pattern composed of a clock pit and a pair of wobble pits extending along a spirally or circumferentially extending recording track or tracks on an optical disc The grooves are formed on both sides of said recording track. The method includes sweeping an optical beam along a land between the grooves under tracking control and measuring the deviation between the centerline between the grooves and the control prepit pattern based on a difference in a playback output from the pair of the wobble pits, or includes sweeping an optical beam so that playback outputs from the wobble pits are equal and measuring the deviation between the centerline between the grooves and the control prepit pattern by a tracking error signal at a land between the gro
REFERENCES:
patent: 4748609 (1988-05-01), Yonezawa et al.
patent: 4949331 (1990-08-01), Maeda et al.
patent: 4996682 (1991-02-01), Yanagihara et al.
patent: 5084860 (1992-01-01), Maeda et al.
Sony Corporation
Tran Thang V.
LandOfFree
Method of measuring a deviation between a centerline between gro does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of measuring a deviation between a centerline between gro, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of measuring a deviation between a centerline between gro will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-668952