Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2003-01-09
2004-03-02
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053270
Reexamination Certificate
active
06700846
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording apparatus capable of recording to different types of disks using lasers with different wavelengths.
Recordable optical disks that have been proposed include CD-R and CD-RW disks, which are based on compact disks and record and playback data using a wavelength of approximately 780 nm, and DVD-RAM, DVD-R, and DVD-RW disks, which are based on DVD disks and record and playback data using a wavelength of approximately 650 nm.
An example of a conventional information recording and reproducing apparatus is an information recording and reproducing apparatus for CD-R and CD-RW disks that uses a laser with a wavelength of approximately 780 nm only. Also, an information recording and reproducing apparatus for DVD-RAM disks has been developed that is equipped with a laser with a wavelength of approximately 650 nm and a playback laser having a wavelength of approximately 780 nm, thus allowing CD-R and CD-RW disks to be played back. This device is able to perform record/playback operations on DVD-RAM disks and playback operations on CD-R and CD-RW disks by focusing the laser beam with objective lenses that correspond to the wavelength of the laser being used, with an objective lens being selected for each disk playback operation.
SUMMARY OF THE INVENTION
However, while the information recording and reproducing apparatus for DVD-RAM disks described above is capable of playing back CD-R and CD-RW disks, CD-R recording is not possible with the 650 nm DVD-RAM laser due to the fact that the reflective properties of the organic pigment used in the disk recording surface of CD-R and CD-RW disks is dependent on the laser wavelength. In other words, it is not possible to record on different disk types that require different wavelengths for recording.
Disk type discrimination must be performed in order to allow recording on different disk types that require different wavelengths for recording such as DVD-RAM and CD-R and CD-RW. However, due to the dependence of reflective properties on laser wavelength, applying a laser beam may result in data being recorded on the recording surface or damage to the recording surface. If a low laser output is used, the detector output will also be low, resulting in a low S/N ratio and reduced accuracy in the disk type discrimination operation. Thus, the laser wavelength and output used for the discrimination operation must be appropriate.
The present invention provides an information recording and reproducing apparatus capable of recording to multiple disk types requiring different laser wavelengths for recording operations.
To achieve this object, the present invention is structured as described below.
A pickup includes a first laser emitting light with a wavelength of at least 700 nm, a second laser emitting light with a wavelength of less than 700 nm, an objective lens focusing light emitted by the lasers onto a disk, and an optical detector detecting light reflected off of the disk from the lasers. The first laser can be, for example, a laser suited for recording information on CD-based recordable disks or the like such as CD-R and CD-RW disks. The second laser can be, for example, a laser suited for recording information on DVD-based disks or the like such as DVD-RAM disks. Means for rotating rotates the disk at at least 5 Hz before beaming light from the first laser or the second laser onto the disk. Laser driving means drives the lasers. Means for discriminating disks discriminates disk types using amplitudes of reflected light obtained from the optical detector. After rotating means begins rotating the disk at at least 5 Hz, driving means turns on the first laser to emit light so that power exiting the objective lens is no more than 2 mW. Discriminating means determines if a first amplitude is greater than a predetermined value, the first amplitude being the amplitude of reflected light obtained by the optical detector when driving means turns on the first laser to emit light so that power exiting the objective lens is no more than 2 mW is greater than a predetermined value. Laser driving means is controlled so that if the predetermined value is greater the second laser emits light at no more than 1 mW and if the predetermined value is less the second laser emits light at at least 0.3 mW. A second amplitude of reflected light obtained by the optical detector when the second laser is turned on is compared with the first amplitude to perform disk discrimination.
According to another aspect of the present invention, an information recording and reproducing apparatus also includes: a first encoder and a first laser driver corresponding to information recording operations using the first laser; and a second encoder and a second laser driver corresponding to information recording operations using the second laser. Information can be recorded to a plurality of disk types by selecting between the first encoder and the first laser driver and said second encoder and the second laser driver based on discrimination results from disk discriminating means.
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patent: 6115336 (2000-09-01), Okada
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patent: 6510115 (2003-01-01), Furuichi et al.
Furuichi Tokinori
Hayashi Hiroyuki
Hirai Yuji
Inaba Seiji
Jin Gohshi
Hitachi , Ltd.
Huber Paul W.
McDermott & Will & Emery
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