Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-08-01
2004-06-22
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044320, C369S044410
Reexamination Certificate
active
06754157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording and/or reproducing apparatus and a recording and/or reproducing method, which can be applied preferably to a DVD reproducing apparatus, a DVD recording apparatus and a DVD recording and/or reproducing apparatus and the like for recording and/or reproducing in/from an optical disc such as DVD-R and DVD-RW.
2. Description of the Related Art
Generally, address information and the like is preliminarily recorded in a recordable optical recording medium so as to enable recording of desired information, and a recording track wobbled under a predetermined frequency is provided to generate a clock signal for use in recording and/or reproducing operation.
As such an optical recording medium, for examples digital versatile disc-recordable (DVD-R) capable of recording the amount of information about 7 times that of the compact disc (CD)has been currently available. In this DVD-R, information such as video data and audio data is recorded in concave pre-grooves in the form of a recording pit, while address information and the like are preliminarily recorded in convex land located between these pre-grooves in the form of land pre-pit (LPP).
The land pre-pits (LPP) on the land are recorded such that a LPP do not overlap with an adjacent land pre-pit (LPP) located beyond a pre-groove on a straight line perpendicular to a tangent line of the pre-groove. The pre-groove is employed for rotation control of the DVD-R and provided so as to be wobbled slightly in a radius direction at a predetermined frequency based on the reference clock.
Upon the rotation control of the DVD-R, the wobbling frequency is detected from a reproduction output of the wobbled pre-groove (hereinafter referred to as wobbling groove) and then feedback control is carried out so that this detected wobbling frequency coincides with the frequency of the reference clock.
For the land pre-pit (LPP), a reflection light of light beam (laser beam) irradiated to the wobbling groove from a semiconductor laser is received by a photo detector divided to at least two sections with optically parallel lines in the tangent line direction of the wobbling groove and then, a differential signal in a direction perpendicular to the wobbling groove between the output signals sent from respective regions (individual divided regions) of this photo detector is obtained. Then, by comparing this differential signal with a predetermined threshold value and then binarizing, its binary signal is detected.
In the case of the disc-like recording medium, the dividing regions are formed on the photo detector in the radius direction of the optical disc with the aforementioned dividing lines and the differential signal is called radial push-pull signal.
The reason why the land pre-pit (LPP) can be detected with such binarized binary signal by comparing the radial push-pull signal (differential signal) with the predetermined threshold value is that as described above, the land pre-pits (LPP) are formed such that there are no two adjacent land pre-pits beyond a wobbling groove on a straight line perpendicular to the tangent line of the wobbling groove.
That is, when the light beam is irradiated to a wobbling groove, the reflection light from the lands on both sides do not contain the land pre-pit (LPP) reflection components at the same time (only the reflection light from either land contains the LPP component). Thus, by computation of the differential, only the reflection light component of the land pre-pit (LPP) is extracted.
Usually, the binary signal obtained by comparing only one of the both polarity components (for example, positive polarity component) obtained by the above computation of the differential with the predetermined threshold value is employed as the land pre-pit signal (LPP signal).
Meanwhile, in the optical disc such as the DVD-R and DVD-RW, the land pre-pit (LPP) is detected by comparing the radial push-pull signal (differential signal) with the predetermined threshold and then binarizing its result. Although conventionally, two input signals are adjusted so as to be equal in terms of the amplitude ratio for computation of the radial push-pull signal (differential signal), laser power modulation component during recording turns to noise in the land pre-pit (LPP) according to this method. Further, when the reproduction mode is selected, the land pre-pit (LPP) is detected erroneously due to an influence of the recording pit. Further, if a lens shift of an objective lens occurs when the recording/reproduction mode of the optical disc is selected, the balance of the radial push-pull signal is destroyed, so that the radial push-pull signal may be detected erroneously either.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been achieved in views of the above-described problem and therefore, an object of the invention is to provide a recording and/or reproducing apparatus and a recording and/or reproducing method for extracting the radial pre-pit signal (LPP signal) at a high precision with a simple structure.
To achieve the above object, there is provided a recording and/or reproducing apparatus for recording and/or reproducing information signal into/from a disc-like recording medium including wobbling grooves each wobbled according to a predetermined frequency and serving as a recording track for the information signal and lands in which at least address information is preliminarily recorded in the form of a land pre-pit at a predetermined wobbling cycle interval, the wobbling grooves and the lands being formed alternately spirally or coaxially, the recording and/or reproducing apparatus comprising: coefficient multiplying means for when a light beam is irradiated to the disk-like recording medium, receiving reflection light from the disk-like recording medium with first and second light receiving regions, divided equally along the recording track of the disk-like recording medium and multiplying one of respective light reception outputs of the first and second light receiving regions with a predetermined coefficient k; push-pull signal generation means for outputting a differential as a radial push-pull signal, the differential being produced by subtracting the multiplication processing result outputted from the coefficient multiplying means from the other of the respective light reception outputs of the first and second light receiving regions; land pre-pit signal amplitude detecting means for extracting a land pre-pit signal corresponding to a land pre-pit on the lands from the radial push-pull signal so as to detect and output an amplitude of the land pre-pit signal; wobbling signal amplitude detecting means for extracting a wobbling signal in the wobbling grooves from the radial push-pull signal so as to detect and output an amplitude of the wobbling signal; and coefficient setting means for setting a value of the predetermined coefficient k to be larger than 1.0 and in a range capable of detecting the land pre-pit signal based on the amplitude of the land pre-pit signal, or the amplitude of the land pre-pit signal and the amplitude of the wobbling signal.
Further, to achieve the above object, there is provided a recording and/or reproducing apparatus for recording and/or reproducing information signal into/from a disc-like recording medium including wobbling grooves each wobbled according to a predetermined frequency and serving as a recording track for the information signal and lands in which at least address information is preliminarily recorded in the form of a land pre-pit at a predetermined wobbling cycle interval, the wobbling grooves and the lands being formed alternately spirally or coaxially, the recording and/or reproducing apparatus comprising: coefficient multiplying means for when light beam is irradiated to the disk-like recording medium, receiving reflection light from the disk-like recording medium with first and second light receiving regions, divided equally along the recording track of the disk-like recordi
Huber Paul W.
Nath Gary M.
Nath & Associates PLLC
Victor Company of Japan , Limited
LandOfFree
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