Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal gain processing
Reexamination Certificate
1997-12-15
2001-03-06
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal gain processing
C369S059230
Reexamination Certificate
active
06198711
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an equalizer for an optical reproducing apparatus which reproduces data by suitably performing a decoding operation on signals read from a disc-like recording medium in accordance with a partial-response transmitting method.
2. Description of the Related Art
In the field of a system using recording mediums, such as optical discs and magneto-optical discs, research is being made on increasing the recording capacity and the recording density. To achieve high density recording, it is important to shorten the laser wavelengths and to suitably set the numerical aperture (NA) of an objective lens. Moreover, the partial-response transmitting method in which the intersymbol interferences, which would disadvantageously act on high density recording, are paradoxically utilized, is also known as a digital-data transmitting method for facilitating high density recording.
Several types of partial-response transmitting methods may be classified by allocating data in accordance with the characteristics of the transfer functions. The above transmitting methods which have been put into practical use may be represented by PR0 (class 0 partial response, which is also referred to as “the PR(1) method”) through PR5 (class 5 partial response, which is also referred to as “the PR (−1, 2, −1) method”), shown in FIG.
12
.
FIG. 12
illustrates the elements inherent in each partial response method, i.e., the response waveform, the frequency characteristics, and the output level number in response to the binary input data after PR equalization is performed.
In order to achieve even higher density recording after the laser wavelength and the NA are suitably set, it is necessary to introduce the foregoing partial-response transmitting method and also to perform an equalizing operation (correcting the frequency characteristics) on the transmitting signals by means of filtering in an electrical circuit. However, the above equalizing operation may impair the reliability of detecting the data. Thus, the electrical equalizing operation is not sufficient in order to achieve even higher density recording.
Further, in the above equalizing operation, the spatial frequency characteristics are corrected on a time axis. It is thus necessary to change the frequency characteristics in accordance with the linear velocity obtained during disc reproduction. For example, in a constant angular velocity (CAV)-type disc, or a zone CAV-type disc, the equalizing characteristics should be changed in accordance with the reproducing position in the radial direction of the disc. This inevitably increases the complexity of the configuration of the circuit and the equalizing operation.
SUMMARY OF THE INVENTION
Accordingly, in order to overcome the above drawbacks, it is an object of the present invention to optimally perform an equalizing operation in accordance with the spatial frequency characteristics without needing to perform an electrical equalizing operation in which the frequency characteristics should be changed in response to the reproducing position in the radial direction of a disc.
In order to achieve the above object, according to the present invention, there is provided an optical reproducing apparatus comprising: laser emitting means for emitting laser light to an optical recording medium; movement means for moving the laser light along a track of the optical recording medium; light receiving means having a plurality of light receiving areas which are divided by a line perpendicular to the track direction, each of the light receiving areas receiving laser light reflected by the optical recording medium and outputting an electrical signal at a level in accordance with the quantity of light; calculation means for adding the electrical signals from the plurality of light receiving areas based on a predetermined mathematical expression and outputting the calculated signal as a reproducing signal in which spatial frequency characteristics are corrected; and decoding means for decoding an information signal in accordance with a partial response method based on the reproducing signal output from the calculation means.
With the above calculation, the frequency characteristics comparable to those by a conventional electrical equalizing operation can be obtained. Namely, the characteristics in response to the spatial frequency can be obtained by the respective outputs detected by the light receiving areas in the track direction.
REFERENCES:
patent: 4831613 (1989-05-01), Kanda
patent: 5363352 (1994-11-01), Tobita et al.
patent: 5469415 (1995-11-01), Fujita et al.
patent: 5469420 (1995-11-01), Fujita et al.
patent: 5517481 (1996-05-01), Kobayashi
patent: 5812505 (1998-09-01), Shimoda et al.
patent: 5881039 (1999-03-01), Sano et al.
patent: 5886964 (1999-03-01), Fujita
patent: 5892741 (1999-04-01), Kadowaki et al.
patent: 0430811 A2 (1991-06-01), None
patent: 0652559 A2 (1995-05-01), None
Patent Abstracts of Japan, JP 8-180608, Published Jul. 12, 1996, Sharp Corp.
M. Ferguson, “Optimal Reception for Binary Partial Response Channels,” The Bell System Technical Journal, vol. 51, No. 2, Feb. 1972, pp. 493-505.
K. Arai, “PRML Signal Processing Techniques,” White Series No. 154, Published Sep. 27, 1994, Chapter 4, “PR Coding Method,” pp. 81-97.
Fujita Goro
Teraoka Yoshiyuki
Hindi Nabil
Limbach & Limbach LLP
Sony Corporation
LandOfFree
Equalizer for optical reproducing apparatus, using partial... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Equalizer for optical reproducing apparatus, using partial..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Equalizer for optical reproducing apparatus, using partial... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438735