Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2001-09-26
2003-09-30
Hindi, Nabil (Department: 2655)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S116000
Reexamination Certificate
active
06628588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an information record apparatus for performing power calibration when recording information on an optical information record medium such as a write-once optical disk or a rewritable optical disk, for example, a power calibration method at the information recording time, and an optical information record medium recording information to perform power calibration.
2. Description of the Related Art
In recent years, in addition to read-only CD (compact disk) and DVD (digital video disk or digital versatile disk), write-once (recordable) CD and DVD, rewritable CD and DVD, MD (mini disk), and the like have been developed for increasing the number of variations of the optical information record media.
In write-once (recordable) CD and DVD, which will be hereinafter collectively called write-once optical disk, write laser light is applied to a record film of an organic coloring matter material for forming circular or elliptic record pits, thereby irreversibly recording information. In rewritable CD and DVD, which will be hereinafter collectively called rewritable optical disk, write laser light is applied to a phase change film for repeating crystallization and rendering amorphous, thereby reversibly recording information as circular or elliptic record pits. In MD, magneto-optical recording is performed.
To form an appropriate circular or elliptic record pit defined on the specification on write-once optical disk and rewritable optical disk, write laser light is controlled by light pulse strategy.
In the light pulse strategy, the form of a light pulse relative to the record mark length is adjusted, whereby laser light emitted from a semiconductor laser is optimized, and record pits of an appropriate form are formed by the optimized laser light, so that a high-quality reproduction signal with occurrence of jitter, etc., suppressed can be provided when information is reproduced.
Power calibration to previously adjust the emission power of the semiconductor laser is executed before essential information recording is performed based on the light pulse strategy.
In the power calibration, record pits are formed in a power calibration area provided at the inner radius of an optical disk and the emission power of the semiconductor laser is optimized based on the waveform provided, for example, by AC coupling a detection signal, called HF signal, provided by optically reading the record pits formed (namely, written for a try) in the power calibration area.
That is, as with the case where normal information reading is executed, reflected light from the power calibration area in which the recordpits are formed is detected by a photo detector and outputs of the photo detector are combined, whereby the HF signal is generated. This means that the HF signal is a signal before equalizing to generate an RF signal, etc., is performed.
As the HF signal is thus generated, an eye pattern of the HF signal is provided. If the waveform is AC-coupled, top peak level a1 of the waveform indicates the potential difference between the potential indicating the strength of reflected light from a land where no record pit is formed and the potential of AC ground GND and bottom peak level a2 indicates the potential difference between the potential indicating the strength of reflected light from a record pit and the potential of AC ground GND, as shown in FIG.
12
A.
The ratio between the peak-to-peak value of the HF signal (a1+a2) and the difference between the levels (a1−a2), which will be hereinafter referred to as &bgr; value, is found as shown in the following expression (1), and, for example, when &bgr; value=0 is adopted as the target of the power calibration, if the &bgr; value becomes almost 0, it is determined that the emission power P of the semiconductor laser is equal to target power Pw; if the waveform provided by AC coupling the HF signal becomes the waveform shown in FIG.
12
B and the &bgr; value becomes a negative value, it is determined that the emission power P of the semiconductor laser is smaller than the target power Pw; and if the waveform provided by AC coupling the HF signal becomes the waveform shown in FIG.
12
C and the &bgr; value becomes a positive value, it is determined that the emission power P of the semiconductor laser is larger than the target power Pw. The emission power P of the semiconductor laser is adjusted so as to become equal to the target power Pw based on each determination result.
&bgr;=(
a
1−
a
2)/(
a
1+
a
2) (1)
A method of determining whether or not the emission power P of the semiconductor laser reaches the target power Pw by examining asymmetry of the HF signal itself produced in response to the size and form of a recordpit formed in the power calibration area is also devised.
In the method of examining asymmetry, as shown in
FIG. 13
, top peak level A1 of the HF signal corresponding to the strength of reflected light from a land where no record pit is formed, bottom peak level A2 corresponding to the strength of reflected light from a large record pit, top peak level B1 corresponding to the strength of reflected light from a land between small recordpits, and bottompeak level B2 corresponding to the strength of reflected light from a small record pit are detected and the detected levels A1, A2, B1, and B2 are applied to the following expression (2), thereby finding the value of asymmetry, which will be hereinafter referred to as a value:
&agr;={(
A
1+
A
2)−(
B
1+
B
2)}/{2×(
A
1−
A
2)} (2)
For example, when &agr; value=0 is adopted as the target of the power calibration, if the a value becomes 0, it is determined that the emission power P of the semiconductor laser is equal to the target power Pw, and if the a value becomes unequal to 0, it is determined that the emission power P is not equal to the target power Pw, and the supply current to the semiconductor laser is controlled so that the emission power P becomes equal to the target power Pw.
When a pit is recorded and formed on an optical disk, the specification of modulation depth M found according to the following expression (3) must also be satisfied:
M=
(
A
1−
A
2)/
A
1 (3)
However, the &bgr; value and the a value fluctuate depending on the type difference between optical disks, the pulse strategy, the characteristic variations, etc., of the optical systems and electronic elements contained in pickups and thus, if the emission power of the semiconductor laser is previously adjusted based on the &bgr; value and the a value by the power calibration described above, the modulation depth may not be provided and when record pits are formed at the essential information recording time and the information is reproduced, the modulation depth is degraded and jitter, etc., accompanying the degradation of the modulation depth occurs in the reproduction signal; this is a problem. That is, it may become difficult to optimize the emission power of the semiconductor laser with good accuracy as the power calibration based on the &bgr; value and the a value in the related art is executed.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an optical information record apparatus and an optical information record method for making it possible to overcome the above-described problems and recording and forming pits in appropriate form.
It is another object of the invention to provide an information record medium recording control information to record and form pits in appropriate form for controlling an electronic machine based on the control information.
To the ends, according to the invention, there is provided an information record apparatus for adjusting power of write light on to an optical information record medium, the information record apparatus comprising a light source for emitting the write light, a power adjustment section for adjusting the emission power of the write
Hindi Nabil
Pioneer Corporation
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