Dynamic information storage or retrieval – Binary pulse train information signal – Format arrangement processing for auxiliary information
Reexamination Certificate
2002-09-30
2004-03-02
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Binary pulse train information signal
Format arrangement processing for auxiliary information
C369S059140, C369S047300
Reexamination Certificate
active
06700849
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for writing on and reading an optical recording medium.
Recently, optical disks, cards and tapes are developed and have been used for recording information optically. Especially, optical disks are given attention as a medium having large capacity and high density.
A conventional method for writing an optical disk is explained below referring to the figures.
FIG. 27
shows an example of an optical disk using a phase-change type recording film. A substrate
2301
, which is made of a glass or plastic material such as PMMA or polycarbonate, is provided with guide grooves
2302
and pits indicating an address or other information. This area with the pit train is called the ID area. The guide grooves are formed in concentric circles or a coil from the inner to outer portions of the substrate. Areas
2307
between the grooves are called lands. The ID areas are located at a predetermined pitch along the guide grooves. The areas between the ID areas are called sectors. A surface of the substrate
2301
is provided with layers of a protective film
2303
, a recording film
2304
and a reflection film
2305
formed by sputtering or other methods. Furthermore, a protective sheet is glued onto the layers.
A method for writing on and reading the above-mentioned optical recording medium is explained below referring to the figures.
FIG. 28
shows a block diagram of a conventional writing and reading apparatus.
FIG. 29
shows the write and read operation for an optical disk. In
FIG. 29
, (a) indicates a write data signal, (b) indicates a laser-driving signal (corresponding to a laser power), (c) indicates a recorded state of the optical disk, and (d) indicates a record format.
The reading process for the optical disk is performed as follows. A system controller circuit
101
drives a spindle motor
114
that rotates the optical disk
113
. An optical head
112
focuses a laser beam with a weak power (Pr in
FIG. 29
) to irradiate the optical disk
113
, tracking the guide groove
2302
and the pit train
2502
shown in (c) of FIG.
29
. The intensity of the beam reflected by the optical disk
113
varies in accordance with the existence of the pit train
2502
and record marks
2501
. Detecting the intensity of the reflected beam generates read signal
122
, which is processed into binary data by a read signal processor circuit
115
and demodulated by a demodulator circuit
116
. Then the signal is processed in an error correction and deinterleaving circuit
117
to obtain read data. The deinterleaving process restores the original data from the interleaved data, which are changed in order.
The writing process for the optical disk is performed as follows. A system controller circuit
101
connected to a host computer gives write data
102
to an error correction and interleaving circuit
103
, which adds error correcting data, i.e., parity bits to the write data, and performs an interleaving process. The interleaving process makes error correction easy by converting a burst error (long continuous error) due to a defect of the optical disk into a random error (short error). The write data are divided into blocks and the order of the blocks is changed according to a predetermined rule in the interleaving process. Then a modulator circuit
104
modulates the data in accordance with the (1, 7) RLL modulation method, for example. Consequently, a modulated data signal
105
is obtained for writing the data area
604
shown in (d) of FIG.
29
.
In the synthesizer circuit
109
, each data block to be written into each sector is provided with VFO and RESYNC signals from a synchronizing signal generator circuit
108
as well as dummy data from a dummy data generator circuit
107
if necessary, to make the write data signal
118
. The VFO and RESYNC are synchronizing signals for generating a clock signal synchronizing with the read signal in a PLL circuit (synchronizing signal generator) in the read signal processor circuit
115
. The VFO signal is added to the head of the modulated data, and the RESYNCH signal is added in the modulated data signal at a predetermined interval. The dummy data are added for reducing a deterioration of the recording film generated at the end of writing when writing on the same sector repeatedly. The dummy data is not required to include any information. The example of the write data signal
118
is shown in (a) of FIG.
29
.
Corresponding to the write data signal
118
, the laser driver circuit
110
generates a laser driving signal
111
to drive a laser in the optical head
112
, modulating the intensity of the laser beam. An example of the laser-driving signal
111
is shown in (b) of FIG.
29
.
When the optical head
112
irradiates the recording film of the optical disk
113
with the focused laser beam having a high intensity (Pp shown in (b) of
FIG. 29
) for a predetermined period, the temperature of the recording film rises above the melting point and drops rapidly. As a result, the melted spot becomes a recorded mark
2501
(shown in (c) of
FIG. 29
) having an amorphous state due to rapid cooling. On the contrary, when the recording film is irradiated with the focused laser beam having a middle intensity (Pb shown in (b) of
FIG. 29
) for a predetermined period, the temperature of the recording film rises to the temperature below the melting point but above the crystallization point. Then the irradiated spot is cooled gradually and assumes a crystalline state.
A recorded pattern having crystalline and amorphous spots as mentioned above, which corresponds to the modulated data signal
105
, is created in the data area
604
on the guide groove
2302
. Thus, writing and reading of information are performed using a difference of reflectivity between the crystalline and amorphous states.
As shown in (d) of
FIG. 29
, there is a gap area
602
between the ID area
601
and the VFO area
603
, as well as a buffer area
606
between the dummy data area
605
and the next ID area
601
. The gap area
602
generates a time for controlling the laser power, and the buffer area
606
compensates for a difference of recording position due to rotation variability of the spindle motor.
When scanning an ID area
601
between sectors
607
of the optical disk, address data are read by the laser irradiating the optical disk with the same weak power as the reading power.
The system controller circuit has a configuration shown in FIG.
30
. Transmission of write data and read data between a host computer and the write/read apparatus is performed using a write data buffer
2601
and read data buffer
2602
respectively. The read data is given to the read data buffer
2602
as well as an address data detector circuit
2603
. An address data detecting signal is transmitted to the write data buffer
2601
and the read data buffer
2602
. A motor driver circuit
2604
drives the spindle motor.
When writing on the optical disk repeatedly as mentioned above, a quality of the read signal of the written data in a sector may be deteriorated at a certain part. Especially, writing similar data into the same sector repeatedly makes the deterioration serious because that part of the sector undergoes repeated melting and hardening while another part never melts. As a result, the thickness of the recording film changes at the boundary of the two parts, so that the thermal and optical characteristics are deteriorated at the boundary. In this case, it is difficult to record (write) and reproduce (read) data properly.
There is a writing method to solve the above-mentioned problem proposed in the Japanese laid-open patent application (Tokukaihei) 2-94113. This method writes data while varying the start point for writing a sector at random within a predetermined range. This range is called the variation range in this specification.
In this writing method, however, the variation range of the start point for writing was constant for various recording media or conditions. On the other hand, the deterioration rate of t
Narumi Kenji
Nishiuchi Ken'ichi
Edun Muhammad
Merchant & Gould P.C.
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