JP2654017B2 - Data reproduction method for optical disk - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for reproducing data from an optical disk for reproducing data from an optical signal from the optical disk.

(Prior Art) In an optical disc device, a track on an optical disc is irradiated with a laser beam while scanning the track on the optical disc with the optical pickup, the reflected light (or transmitted light) is detected and converted into an electric signal. In this case, as shown in FIG. 4, the electric signal I has a high level (H) due to the large amount of detection light from the optical disk where there are no pits on the optical disk, and the detection light from the optical disk where there are pits on the optical disk. And the level becomes low (L). In the case of an optical disk for data recording / reproducing, tracks on the optical disk are used in a unit of sector in the longitudinal direction of the track. Therefore, it is necessary to consider data reproduction by separating the head A of the sector and the main part B of the sector. is there. That is, a method using a circuit as shown in FIG. 5 is conventionally known as a method for reproducing data from an optical disk. In this method, the optical pickup converts an optical signal composed of light reflected from an optical disk into an electric signal by an optical / electrical converting means comprising a light receiving element and an amplifier A1, and then reproduces a reproduced signal I including a DC component from the amplifier A1. And the difference between the low-frequency signal component obtained by passing this through a low-pass filter LPF is calculated by an arithmetic unit A2 as arithmetic means, and the boundary between the pit and the space on the track of the optical disk is detected as a zero-cross point. I have. However, in this method, since the circuit of FIG. 5 operates in the same manner as the AC amplifier, the output signal II of the arithmetic unit A2
However, as shown in FIG. 4, it takes time for the signal to be stabilized in the sector head A in proportion to the time constant of the low-pass filter LPF.

If the stabilization time is to be shortened, there is a drawback that waveform interference increases in the main part B of the sector, jitter increases, and a long burst error occurs due to the presence of a defect on the optical disk.

(Object) It is an object of the present invention to provide a data reproducing method for an optical disk capable of eliminating the above-mentioned drawbacks and reproducing the sector start portion and the sector main portion under optimum conditions.

(Structure) The present invention converts an optical signal from an optical disk in which a track is divided in sector units in the longitudinal direction of the track into an electric signal by an optical-electrical converting means, and converts the signal from the optical-electrical converting means into an electric signal. A method for reproducing data from an optical disc, wherein a boundary between a pit and a space on a track of the optical disc is detected as a zero-cross point by calculating a difference between the signal and a signal obtained through a low-pass filter by a calculating means. A plurality of low-pass filters having different time constants are provided as the low-pass filter provided between the optical disk and the arithmetic means. The sector is switched by a switch at the head and main part of the sector divided in the longitudinal direction. A low-pass filter having a short time constant among the plurality of low-pass filters is selected at the beginning of the plurality of low-pass filters, and a low-pass filter having a long time constant among the plurality of low-pass filters is selected at a main part of the sector. It is characterized by.

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 shows a circuit used in one embodiment of the present invention.

In this embodiment, a plurality of low-pass filters LPF1 and LPF2 having different time constants from each other are provided as the low-pass filter LPF in the above-described conventional optical disc data reproducing method,
The low-pass filters LPF1 and LPF2 can be selected by a switch SW. The switch SW is switched by the switch switching means C, and selects a low-pass filter having a time constant optimal for an optical signal from the optical disk. When data is reproduced from an optical disk, the optimum value of the time constant of the low-pass filter is different between the sector head part A and the sector main part B as described above. If there is a defect in the optical disc, there is an optimal time constant of the low-pass filter due to the noise, and if a low-pass filter with a time constant inappropriate for the defect size is selected, even a small defect will increase in length and cause a long burst error. Become. Therefore, the switch SW may be switched at the boundary between the sector head portion A and the sector main portion B or at the time of retry when a burst error occurs due to a defect on the optical disk, or at the time of verify check immediately after data recording.

When the signal sequence recorded on the optical disk records, for example, a bit synchronization signal, a frame synchronization signal, and an information signal as shown in FIG.
, A frame synchronization signal is detected from the output signal, and the detection signal (frame synchronization detection signal) is as shown in FIG. When the frame synchronization detection signal becomes 1, the switch switching means C sets the switch switching signal to 1 by holding this signal for the length of the information signal or slightly longer than that. The switch SW is a low-pass filter LP when the switch switching signal from the switch switching means C is 0.
Select F1 and connect it to arithmetic unit A2.
In the case of, the low-pass filter LPF2 is selected and connected to the arithmetic unit A2. If the time constant of the low-pass filter LPF1 is shorter than the time constant of the low-pass filter LPF2, the bit synchronization signal is detected in a short time at the head of the sector on the optical disk track, and the information signal is transmitted to the main part of the sector. It can be read with little jitter and error. That is,
As is clear from FIG. 2, the switch switching signal is 0 at the head of the sector and the switch SW selects the low-pass filter LPF1 having a short time constant. Selects the low-pass filter LPF2 with a long time constant. For this reason, a bit synchronization signal is quickly output from the output signal of the arithmetic unit A2, to which the output signal of the amplifier A1 and the output signal of the low-pass filter LPF1 having a short time constant are input, to the head of the sector by the switch switching means C. Low-pass filter LP with long time constant detected and switched to switch SW
F2 can be selected, and the information signal can be read from the main part of the sector with little jitter and error.

When reading data from an optical disk, the switch switching means C may be one which performs processing as shown in FIG. In this case, the switch switching means C reads data from the output signal of the arithmetic unit A2 in a normal state, and if an error is detected in the data, a low-pass filter is connected to the switch SW.
The data is read again by switching between LPF1 and LPF2. By doing so, data reading errors can be reduced.

(Effects) As described above, according to the present invention, an optical signal from an optical disk in which a track is divided in sector units in the longitudinal direction of the track is converted into an electric signal by an optical-electrical conversion unit,
The difference between the signal from the optical-to-electrical conversion means and the signal obtained by passing the signal through a low-pass filter is calculated by a calculation means to detect the boundary between a pit and a space on a track of the optical disk as a zero-cross point. In the data reproducing method, a plurality of low-pass filters having different time constants are provided as the low-pass filter provided between the optical-to-electrical conversion unit and the arithmetic unit, and the plurality of low-pass filters are connected to the optical-to-electrical conversion unit. The signal from the means is switched by a switch between a head portion and a main portion of the sector divided in the track longitudinal direction of the optical disk, and at the head portion of the sector, the time constant among the plurality of low-pass filters is short. And in the main part of the sector out of the plurality of low-pass filters Since such time constant to select a longer low-pass filter, and reproduced sector head portion and the sector main part at respective optimum conditions, also,
The signal from the optical-to-electrical conversion means is switched from a low-pass filter with a short time constant to the head of the sector to a low-pass filter with a long time constant for the main part of the sector in a short time to reduce the information signal to the main part of the sector,
It becomes possible to read out by error. Further, by not performing feedback, the operation of the recording data having the sector configuration can be reproduced with high reliability without instability.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a circuit used for implementing the present invention, FIG. 2 is a timing chart of the circuit, FIG. 3 is a flowchart for explaining the present invention, and FIG. FIG. 5 is a block diagram showing a circuit used in the conventional method. LPF1, LPF2 …… Low-pass filter, A2 …… Calculator, SW…
…switch.

Claims (1)

(57) [Claims] 1. An optical signal from an optical disk in which a track is divided in sector units in a longitudinal direction of a track is converted into an electric signal by an optical / electrical converting means, and the signal from the optical / electrical converting means and the signal are converted. In a data reproducing method for an optical disc, in which a difference between a signal obtained through a low-pass filter and a boundary between a pit on a track of the optical disc and a space is detected as a zero-cross point by calculating the difference with a calculating means, A plurality of low-pass filters having mutually different time constants are provided as the low-pass filter provided between the arithmetic means and the plurality of low-pass filters. Switch between the head and main part of the sector divided by Wherein a low-pass filter having a short time constant among the plurality of low-pass filters is selected, and a low-pass filter having a long time constant among the plurality of low-pass filters is selected in a main part of a sector. Method of reproducing data from an optical disk.