Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-03-16
2001-05-08
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
Reexamination Certificate
active
06229776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This inventions relates to optical disc apparatuses, and more particularly to an optical disc apparatus which is arranged to read desired data out of an optical disc having audio data areas and CD-ROM areas coexisting thereon.
2. Description of the Prior Art
There are optical discs formed with a CD-ROM area having computer code data and an audio data area in a coexisting manner. In an optical disc apparatus loaded with such an optical disc, the optical disc is frequently switched of rotational speed or reproducing speed depending upon data to be read out. That is, the audio data is reproduced at a normal speed (1-times speed), whereas the computer code data is at a speed of a predetermined number times higher the normal speed (e. g. an 8-times speed).
The disc reproduced signal (reproduced EFM signal), read out of an optical disc through an optical pick-up, is configured by a plurality of pattern data different in pulse width (3T-11T). Accordingly, there is a necessity of accurately discriminating the pulse width by reproducing a clock that is synchronous with the reproduced EFM signal. The reproduced EFM signal is synchronously processed by a PLL circuit, wherein the reproduced EFM signal is compared with an oscillation clock of a VCO (voltage controlled oscillator) to control the VCO oscillating frequency in response to an error difference (voltage) between them. Consequently, the optical disc apparatus, requiring frequent changeover of reproducing speed, is structured to vary a PLL characteristic to meet with a reproducing speed, for example, by adjusting the frequency-dividing ratio of a variable frequency divider for dividing the VCO output.
Meanwhile, the audio data can be read only at a certain given frequency (normal speed), whereas the computer code data or the like can be read out over a comparatively broad speed range. That is, it is possible to read data, depending upon a frequency pulling range of the PLL circuit, from an optical disc (rotating, e.g. at a 5-times speed) before reaching an 8-times speed, as shown in FIG.
5
. Nevertheless, it is impossible to read data during a time period (T) before the reproducing speed reaches a speed 5 times higher than the normal speed, as will be understood from FIG.
5
. To this end, there has been a problem of worsening in a response characteristic to a data read request outputted from a host computer.
SUMMARY OF THE INVENTION
Therefore, it is a principal object of this invention to provide a novel optical disc apparatus.
It is another object of this invention to provide an optical disc apparatus which is capable of shortening a time to start reading data, in order to promptly deal with instructions given by a host computer.
This invention is an optical disc apparatus, arranged to read data out of an optical disc being driven by a disc motor rotating at a normal speed or a speed of a predetermined number times higher than the normal speed, comprising: a first clock output means for outputting a first clock for reading data at the normal speed; a second clock output means for outputting a second clock for reading data at the speed of the predetermined number times; and a third clock output means for outputting a third clock intermediate between the first clock and the second clock, wherein the third clock is used when the disc motor is shifted from the normal speed to the speed of the predetermined number times, and the second clock being used when the disc motor approaches the speed of the predetermined number times.
The disc reproduced (EFM) signal, read out of the optical disc rotating at the normal speed (1-times speed), is waveform-shaped (binarized) and then accurately discriminated of pulse width according to a first clock supplied from the first clock output means. Where reading data at a speed of a predetermined number times higher than the normal speed (e.g. at an 8-times speed) due to a data read request from the host computer, the disc reproduced signal read from the optical disc being accelerated by the disc motor is first discriminated of pulse width by a third clock intermediate between the second clock and the first clock.
That is, a third clock is generated that has a frequency pulling range covering over a range where data cannot be read out by the second clock for reproduction at a speed of a predetermined number times the normal speed, so that data can be read from the optical disc immediately after staring an acceleration. When the rotational speed of the disc motor approaches the speed of the predetermined number times the normal speed, i.e. when it reaches a reproducing speed permitted for the second clock, the data is continuously read by using a second clock selected by, for example, adjusting the frequency-dividing ratio of the variable frequency divider.
Also, where reading data by accelerating the optical disc from stoppage in a power-save mode up to a speed of a predetermined number times the normal speed, the data reading can be expedited in timing by using a third clock at a timing after starting the disc motor but the rotational speed of the disc motor is low.
According to this invention, a clock (third clock) is generated that is synchronous with the disc reproduced signal read from the optical disc rotating at a low speed so that data can be read out before the disc reaches a conventional high speed. Therefore, the response characteristic to instructions given by the host computer is drastically improved.
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: 5726958 (1998-03-01), Min
patent: 5740356 (1998-04-01), Liang et al.
patent: 5844872 (1997-06-01), Kubo et al.
patent: 5886966 (1997-05-01), Ota et al.
patent: 5963520 (1997-06-01), Kubo et al.
Kuwayama Yasunori
Yamaue Toshihiko
Funai Electric Co. Ltd.
Hindi Nabil
Lackenbach Siegel Marzullo Aronson & Greenspan P.C.
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