Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-11-06
2001-01-09
Huber, Paul W. (Department: 2753)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S053130
Reexamination Certificate
active
06172959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information processing apparatus for recording and reproducing information on an information storage medium capable of optical recording and reproduction of information, e.g., optical disks or optical cards.
2. Description of the Related Art
In the field of optical memory technologies utilizing optical disks or optical cards, there is an increasing variety of applications including digital audio disks, video disks, data files, and the like. According to optical memory technologies, the information on an information storage medium can be reproduced by using a fine beam of light to read minute convex and concave portions, or marks and spaces (which have distinguishable physical properties from each other) provided on the medium.
FIG. 22
is a diagram illustrating the relationship between aforementioned marks and a fine light beam, where information is recorded based on differential orientations of magnetization on an optical disk as an information storage medium. Hatched regions
302
are marks (A), and blank regions
303
are marks (B), such that marks (A) and marks (B) have different magnetization orientations. A series of repetition of marks (A)
302
and marks (B)
303
are defined as a track. Information can be reproduced as a converged light beam
306
travels over a track.
The size of the converged light beam
306
is a function of the numerical aperture (NA) and wavelength (&lgr;) of the optical system. If a mark length (defined as the length of mark (A)
302
or mark (B)
303
along the longitudinal direction of tracks) is too small relative to the size of the light beam
306
, it becomes difficult to obtain enough modulation of a reproduction signal which is output from an optical head. Therefore, selecting a small minimum mark length for increased recording density results in an increased intersymbol interference (which is essentially the influence from preceding and subsequent marks), thereby making it difficult to maintain a low error rate in the reproduction of information.
Accordingly, a method (Japanese Laid-open Publication No. 6-290496; see ISOM '97 lecture proceedings (Tu~E-04)) has been proposed which virtually enlarges recorded marks to the size of alight beam before reproduction of information.
However, such conventional methods have a problem in that, during reproduction of information recorded on an information storage medium, the generation of specific signal waveforms causes an increase in the error rate in the signal reproduction by a signal reproduction circuit.
SUMMARY OF THE INVENTION
An optical information processing apparatus according to the present invention includes: an optical head for radiating a light beam onto an information storage medium and generating a reproduction signal from the light beam reflected and/or diffracted from the information storage medium, the information storage medium carrying optical readable information recorded thereon; a transportation member for causing a relative movement of the optical head with respect to the information storage medium; and a signal processing circuit for receiving the reproduction signal generated by the optical head and processing the reproduction signal, wherein the reproduction signal includes first information from a mark near a boundary between a region which is heated by the light beam to no less than a predetermined temperature and a first region which is at a temperature below the predetermined temperature, and second information from a mark near a boundary between the region which is heated to no less than the predetermined temperature and a second region which is at a temperature below the predetermined temperature, and wherein the signal processing circuit separates the first information from the second information, or vice versa, thereby obtaining from the reproduction signal the information recorded on the information storage medium.
In one embodiment of the invention, the reproduction signal is a sum of X plus Y, where X is the information signal recorded in the information storage medium and Y is a signal which is obtained by delaying the information signal and multiplying the information delayed information signal by a constant.
In another embodiment of the invention, the signal processing circuit has a transfer function represented by:
1/{1+A·exp(−j&ohgr;T)}
where A is a constant; j is the imaginary unit; &ohgr; is an angular frequency of the reproduction signal generated by the optical head; and T is a delay time.
In still another embodiment of the invention, the signal processing circuit has a transfer function represented by:
1−A·exp(−j&ohgr;T)
where A is a constant; j is the imaginary unit; &ohgr; is an angular frequency of the reproduction signal generated by the optical head; and T is a delay time.
In still another embodiment of the invention, the signal processing circuit is optimized so as to minimize a jitter of the reproduction signal having been processed by the signal processing circuit.
In still another embodiment of the invention, the signal processing circuit is optimized so as to maximize an eye pattern opening of the reproduction signal having been processed by the signal processing circuit.
In still another embodiment of the invention, the optical information processing apparatus further includes the information storage medium, the information storage medium including a magnetic recording film for storing a signal in the form of magnetization orientation, enlargement of the marks being effected by movement of a magnetic partition, and the optical head detecting the magnetization orientation of the magnetic recording film and outputting the reproduction signal.
In still another embodiment of the invention, the constant A and the delay time T are determined so as to minimize a jitter of the reproduction signal having been processed by the signal processing circuit.
In still another embodiment of the invention, the constant A and the delay time T are determined so as to maximize an eye pattern opening of the reproduction signal having been processed by the signal processing circuit.
Thus, the invention described herein makes possible the advantage of providing an optical information processing apparatus having a low error rate during reproduction.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.
REFERENCES:
patent: 5587985 (1996-12-01), Sano et al.
patent: 06290496 (1994-10-01), None
patent: 10092039 (1998-04-01), None
patent: 10092047 (1998-04-01), None
T. Shiratori et al.; ISOM 97 Tu-E-04, pp. 38-39, “High-Density Magneto-Optical Recording With Domain Wall Displacement Detection”.
Kadowaki Shin-ichi
Sano Kousei
Tanaka Shin-ichi
Huber Paul W.
Matsushita Electric - Industrial Co., Ltd.
Renner Otto Boisselle & Sklar
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