Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-06-05
2001-04-10
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S053290
Reexamination Certificate
active
06215739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disc apparatuses, and more particularly to a disc apparatus adapted to correct a track jump error due to individual disc variation.
2. Description of the Prior Art
In a conventional disc apparatus of this kind, when performing a track jump (seek) to a target position, tracks to be jumped over is first determined in number by calculation and a jump is then effected according to the determined number of tracks. As a result of the jump, when a pickup goes beyond the target position (overshoot) or does not reach the target position (undershoot), the disc is judged as one that is liable to overshoot or undershoot. When a track jump is later performed with the same disc, a correcting value for the overshoot or undershoot, i.e. a value (&agr;) taking a disc-manufacturing variation into consideration, is added to or subtracted from the calculated number of tracks, thereby obtaining an accurate seek to a target position.
In the prior art, however, the result of the track jump first made is utilized to compensate for the number of tracks to be jumped later. Accordingly, it has been difficult for a pickup to accurately access to a target position in a track jump immediately after a disc is mounted for the first time on the apparatus. That is, it is a conventional practice to add or subtract a predetermined value (&agr;) to or from the number of tracks to be jumped over, without examining factors encountered in overshoot or undershoot.
SUMMARY OF THE INVENTION
Therefore, it is a primary object of this invention to provide a novel disc apparatus.
It is another object of this invention to provide a disc apparatus which can accurately seek a target position by absorbing variation on a disc-by-disc basis.
A disc apparatus according to this invention, adapted to record information on a disc or reads information out of the disc by using a pickup, comprises: a measuring means for measuring a track pitch; and a determining means for determining, in response to a jump command, a first number of tracks to be jumped over by the pickup based on the track pitch.
First, TOC information is read out. This TOC information enables a determination of whether or not the disc was replaced with another disc. Where the disc was changed, a track pitch is measured. That is, the pickup is moved from a current position to a position of 10 min. (predetermined position). A number of tracks to be jumped at this time is calculated on an assumption that the track pitch is at 1.6 &mgr;m. A track pitch (h) for the disc is measured based on a distance over which the pickup has moved and the number of tracks (tracking error signals) detected during the movement over that distance. That is, the track pitch is calculated on a disc-by-disc basis.
If a command is given to perform a track jump to a target position, tracks to be jumped is determined in number by a distance (r1) from a center of the disc to a current position, a distance (r2) from the disc center to a target position, and the measured track pitch (h). The number of tracks jumped is determined using this track pitch (h), by a time the disc is replaced with another disc.
When the disc is changed, the track pitch data (h) for the disc having been mounted so far is erased and a track pitch for a newly mounted disc is again measured. The determination if the disc is changed or not is made by whether or not TOC information read out agrees with the TOC information stored in the memory.
According to this invention, the track pitch is measured disc by disc, and the number of tracks to be jumped is determined based on the measured track pitch. This realizes a high-speed and accurate track jump (seek).
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4773052 (1988-09-01), Sugiura et al.
patent: 5047999 (1991-09-01), Van Der Meulen
patent: 5065383 (1991-11-01), Tateishi et al.
patent: 5675560 (1997-10-01), Ogino
Adachi Kazuteru
Kuwayama Yasunori
Funai Electric Co. Ltd.
Huber Paul W.
Lackenbach Siegel
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