Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-11-30
2001-12-11
Hudspeth, David (Department: 2752)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S124010, C369S044320
Reexamination Certificate
active
06330218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk reproducing unit and more particularly, to a unit for processing signals from a optical pickup.
2. Description of the Related Art
FIG. 1
depicts light receiving parts of a conventional optical pickup. The optical pickup has light receiving parts A, B, C, D, E and F. Each of them produces an output signal upon receipt of light. The output signals are amplified through corresponding amplifiers AMP to be produced as a, b, c, d, e and f. The focus exactness is detected with a gain difference between the addition of signals a and c and that of signals b and d in the above a, b, c and d. In addition, a degree by which the optical pickup is deviated from a track is detected by using a gain difference of the above signals e and f. A servo controls the optical pickup in accordance with the focus exactness and the information of optical pickup deviation. Errors of more than 10% may be made in output signals a, b, c, d, e and f from light receiving parts A, B, C, D, E and F by the mismatch with respect to those light receiving parts that may occur in the process of manufacturing the optical pickup. That is, during the manufacturing of the optical pickup, its light receiving parts A, B, C, D, E and F may be mismatched. The above errors serve as an offset of the server for controlling the optical pickup, which becomes problematic in a high-speed and high-precision optical disk player.
Referring to
FIG. 2
, depicting a circuit sensing the optical pickup deviation degree by the use of signals e and f (hereinafter, a tracking error sensing unit), signal e is input to an inverting input terminal of a differential amplifier A
1
through a resistor R
1
. Signal f is input to a non-inverting terminal of differential amplifier A
1
through a resistor R
3
. Differential amplifier A
1
's output terminal is connected to its inverting input terminal through a resistor R
2
. The tracking error sensing unit produces a difference of signals e and f, and the transfer characteristics are expressed by equation 1:
Vout
=
-
R2
R1
e
+
1
+
R2
R1
1
+
R3
R4
f
[Equation 1]
The above signal Vout is indicative of a difference of signals e and f and is input to a control device controlling the optical pickup. The control device controls to make the optical pickup keep the track with signal Vout.
If there is an error by the mismatch that may occur in the optical pickup manufacturing process, the conventional tracking error sensing unit does not exactly detect a tracking error with signals e and f.
As described above, there may be a mismatch with respect to light receiving parts A, B, C, D, E and F in the manufacture of the optical pickup, and errors of more than 10% may be made in its output signal by the mismatch. The errors serve as an offset of the servo for controlling the optical pickup, which becomes problematic in a high-speed and high-precision optical disk player.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a balance gain tuning apparatus which can correct errors made in the manufacturing process of an optical pickup.
To achieve the above object of the present invention, there is provided a
balance gain tuning apparatus including a first amplifying part amplifying one of signals output from a optical pickup to a fixed gain; a second amplifying part amplifying another signal of the signals output from the optical pickup to a tunable gain; a subtracting part producing a difference of an output of the first amplifying part and that of the second amplifying part; and a servo control part tuning the gain of the second amplifying part in response to an output of the subtracting part.
REFERENCES:
patent: 4446545 (1984-05-01), Van Dijk
patent: 4736354 (1988-04-01), Yoshio
patent: 4932015 (1990-06-01), Nagashima et al.
patent: 5287338 (1994-02-01), Sato
patent: 5587985 (1996-12-01), Sano et al.
patent: 5828637 (1998-10-01), Kim
patent: 5886964 (1999-03-01), Fujita
patent: 5905703 (1999-05-01), Osada
patent: 5963515 (1999-10-01), Shindo
patent: 5974010 (1999-10-01), Sakanushi
Chu Kim-Kwok
Hudspeth David
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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