JPH0697504B2 - Information reading method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an information reading method, and more particularly to a method for reading recorded information on a recording disc such as a digital audio disc.

BACKGROUND ART In the conventional information reading method, a tracking servo device controls a relative position of an information detection point of a pickup in a direction orthogonal to a recording track, and at the same time, a recording disk is driven to rotate so that the information detection point is relatively moved in an extension direction of the recording track. In this method, the information recorded together with the address information is read by manually moving it. In such a conventional method, the tracking servo device is disturbed due to a scratch on the recording disk or the like, and a track jump operation is performed in a direction opposite to the direction in which the information detection point moves relative to the recording disk, that is, in the inner circumferential direction of the recording disk. However, there is a drawback in that if the user accidentally moves, a loop is formed in which the same information is repeatedly read, and the reproduced sound obtained is unpleasant.

SUMMARY OF THE INVENTION An object of the present invention is to provide an information reading method capable of excellent information reading even if a recording disc has a scratch or the like.

The information reading method according to the present invention compares the current value and the previous value of the address information that are sequentially read with the movement of the information detection point in the recording track extension direction, and determines the difference between the current value and the previous value of the address information. When a certain value or more continues to occur at the same position, the information detection point is moved by a track jumping operation to a position separated from the position corresponding to the previous value of the address information by a predetermined distance in the recording track orthogonal direction. It has a feature.

Example Hereinafter, a detailed description will be given with reference to the drawings of an example of the present invention.

FIG. 1 is a block diagram showing an example of an optical recording disk reproducing apparatus to which the information reading method according to the present invention is applied. In the figure, a laser beam emitted from, for example, a laser diode 2 in a pickup 1 passes through a prism 3, a tracking mirror 4, an objective lens 5, and the like to become spot light (information detection point), which is a recording track (pit) of a disc 6. (Row) 7 is illuminated. The reflected light of the spot light passes through the objective lens 5, the tracking mirror 4, and the prism 3 and enters a so-called four-divided detector 8 including a photodiode or the like built in the pickup 1. The total output of the 4-division detector 8 is the read RF signal.
It is supplied to the demodulator 10 via the RF amplifier 9,
Data demodulation circuit 11 and data processing circuit 20 after demodulation by
Is supplied to. The data extraction circuit 11 extracts address information from the demodulated output, and the address information is stored in the controller.
Supplied to 12.

Further, in the data processing circuit 20, the output data of the demodulator 10 is temporarily stored in the data memory 21 after being subjected to processing such as deinterleaving, error detection, correction and correction. The data stored in the data memory 21 is read by a clock signal of a constant cycle from a clock generation circuit (not shown).
It becomes an analog signal in the D / A (digital / analog) converter 22. This analog signal is output as an audio signal via an LPF (low pass filter) 23.

Each output of the 4-division detector 8 is also supplied to the tracking error signal generation circuit 13. As a method of generating the tracking error signal, there is a so-called 1-beam method, a 3-beam method, or the like, and the 1-beam method also includes a so-called push-pull method, a heterodyne method, or the like. The tracking error signal generated by the tracking error signal generation circuit 13 is
As shown in FIG. 2, it has a so-called S-curve characteristic of zero crossing at the center of the recording track 7, and a drive coil for the tracking mirror 4 via a mirror drive circuit 14.
By being supplied to 15, the mirror 4 is driven to rotate.

Reference numeral 16 denotes a slider motor that mounts the pickup 1 and drives a slider (not shown) that is movable in the disk radial direction. The motor 16 is driven and controlled by a motor drive circuit 17. The motor drive circuit 17 detects the tilt angle of the tracking mirror 4 based on the output of the mirror drive circuit 14, and the slider motor 16 drives the slider 1 in the disk radial direction so that the tilt angle is zero, that is, the tracking mirror 4 is in the neutral position. Position control.
The mirror drive circuit 14 and the motor control circuit 17 are also drive-controlled by a drive signal issued from the controller 12. The tracking pulse generation circuit 18 generates one pulse each time the spot light crosses the recording track 7 based on the tracking error signal shown in FIG.
Send to 12. The controller 12 is a processor, a ROM,
It is formed by a micro-computer such as a timer. In this controller 12, the processor performs various controls in cooperation with the RAM 24 according to a program stored in advance in the ROM and based on the flowchart of FIG.

Next, the operation of the processor in the controller 12 will be described with reference to the sequence diagram of FIG. 4 and along the flowchart of FIG.

On a recording disc, for example, a so-called compact disc, information indicating the absolute time from the innermost circumference of the disc to the current position and the information indicating the absolute time from the inner circumference of the disc to the head of each song are recorded as address information. . Now, when the play operation is performed by the execution of the main routine and the spot light of the pickup 1 reaches the point and the address information is read, the processor reads the current value of the address information, that is, the address information read at the point. The corresponding value is compared with the previous value of the address information, that is, the value corresponding to the previously read address information (step
S1, S2). When it is determined by this comparison that the current value of the address information matches the previous value, the processor immediately resumes execution of the main routine. If it is determined that the current value of the address information matches the value obtained by adding 1 to the previous value, the processor moves to step S3 and RA
To A ₁ address of the M24 after writing the current value of the address information as the previous value to resume the execution of the main routine. Further, when the current value of the address information is determined to not match any of the values combined adding 1 to the previous value and the previous value, the processor ₁ address RAM24 of A and proceeds to step S4 and A ₂ Address The previous value of the address information stored in each is compared with the address value immediately before the jump, which will be described later.

At this point, since the difference between the current value and the previous value of the address information is 1 or less, the processor restarts execution of the main routine immediately after step S, or executes the main routine after further steps S2 and S3. To resume. As a result, the play operation continues, and the spot light follows the recording track and gradually moves in the outer peripheral direction.

Here, there is a scratch at a point, and when the spot light reaches this spot, the scratch causes disturbance in the tracking servo loop and the spot light accidentally moves to the point located in the inner circumferential direction due to the track jump operation. It is also assumed that the address information is read when the play operation thereafter reaches a point located on the inner circumference of the point. Then, at this point, the difference between the current value and the previous value of the address information becomes larger than 1, so the processor proceeds to step S
After 1 and S2, the process proceeds to step S4. When it is determined by the execution of this step S4 that the previous address information and the address value just before the jump are the same, the processor moves to step S5 and determines whether the current value of the address information is larger than the previous value. judge. However, since the previous value of the address information and the address value (initial value) immediately before the jump are different in the point, the processor moves to step S7 and sets the previous value of the address information stored in the address A _{1 of} the RAM 24 to A Write to address ₂ as the address value just before jumping. Next, the processor moves to step S8 and writes the previous value of the address information stored in the address A _{1 of} the RAM 24 into the address A ₃ as a search address value. Then the processor is RAM2
Subroutine R for searching the address indicated by the search address value stored in the address A _{3 of} 4
And then resume the main routine. still,
This subroutine R is formed based on the address search method disclosed in Japanese Patent Application No. 60-28776.

A so-called search operation is performed by executing the subroutine R, and the spot light reaches a point. After that, when the spot light reaches the point by the play operation, the spot light is erroneously moved to the point by the track jump operation due to the scratch at this point. After that, when the spot light resumes the movement toward the outer periphery by the play operation and reaches the point, the address information is read, and the previous value of the address information at this time is read at the point and the address immediately before the jump is reached. The value is equal to the value stored in RAM24.

Therefore, in terms of the processor the steps S1, S2, S4
After that, the process proceeds to step S5. If it is determined in step S5 that the current value of the address information is larger than the previous value, the processor moves to step S3 and
After writing the current value of the address information as the previous value at address ₁ , execution of the main routine is restarted. However,
At this point, the current value of the address information is not greater than the previous value, so the processor moves to step S6 and adds the value corresponding to the distance T seconds required for the light spot to move by the play operation to the previous value, Move to S8. As a result, the spot light moves to a point located on the outer periphery of the point by the search operation and restarts the movement by the play operation.

FIG. 5 is a flowchart showing another example of the operation of the processor in the controller 12, and the steps corresponding to the steps of the flowchart in FIG. 3 are indicated by the same reference numerals. In this example, if there is no step corresponding to step S5 in the flowchart of FIG. 3 and it is determined in step S4 that the previous value of the address information and the address value immediately before the interlace match, the processor immediately executes the step. Move to S6. Therefore, the search operation is started even when the spot light jumps and moves in the outer peripheral direction due to a scratch on the recording disk or the like, but the same effect as in the case of the flowchart of FIG. 3 can be obtained.

Although the method of reading recorded information on a digital audio disc has been described above, the present invention can be applied to any other method of reading information on a recorded disc on which address information is recorded.

As described in detail above, the information reading method according to the present invention compares the current value and the previous value of the address information sequentially read with the movement of the information detection point, and compares the current value and the previous value of the address information with each other. When the difference of becomes equal to or more than a predetermined value continuously occurs at the same position, the information detection point is moved to a position separated by a predetermined distance from the position corresponding to the previous value in the recording track orthogonal direction by the track jumping operation. When the information detection point is erroneously moved in the direction opposite to the reading direction due to the track jumping operation due to scratches or dirt on the recording disk, and a loop is formed in which the same information is repeatedly read, the information detection point is detected from this loop. It will be possible to disengage and prevent the unpleasant state from continuing.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a recording track and a tracking error signal, and FIG. 3 is a flow chart showing an operation of the apparatus of FIG. FIG. 4 is a sequence diagram showing the reading operation of the apparatus shown in FIG. 1, and FIG. 5 is a flowchart showing another example of the operation of the apparatus shown in FIG. Description of main part code 1 …… Pickup 6 …… Recording disk 11 …… Data extraction circuit 12 …… Controller

Claims (1)

[Claims] 1. An information reading method for moving the information detection point of a pickup in a recording track extension direction of a recording disk to read information recorded together with address information on the recording disk, wherein the recording of the information detection point is performed. When the difference between the current value and the previous value of the address information sequentially obtained with the movement in the track expansion direction becomes a predetermined value or more, the previous value is skipped and stored as the immediately preceding address value, and the information detection point is tracked. By the jumping operation, the recording track is moved in the direction perpendicular to the recording track to the position corresponding to the previous value, and then in the recording track extension direction, and the difference between the current value and the previous value of the address information is again the predetermined value or more. When the previous value of the address information is compared with the address value immediately before the jump, the previous value of the address information and the address value immediately before the jump are compared. Is detected, the information detection point is moved by a track jumping operation in a direction orthogonal to the recording track to a position separated from the position corresponding to the previous value of the address information by a predetermined distance, and When it is detected that the previous value and the address value immediately before jumping do not match, the previous value of the address information is stored as the address value immediately before jumping, and the information detection point is recorded on the recording track orthogonally by the track jumping operation. An information reading method comprising moving the address information to a position corresponding to a previous value of the address information.