JP2000298848A - Method for measurement and search of track pitch on disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for the measurement of a track pitch on a disk in which a signal is recorded at a constant linear velocity. SOLUTION: A linear velocity is measured in a prescribed position on a disk in which a signal is recorded at a constant linear velocity. After that, a pickup is moved to a measuring position at a set absolute time. A radius in the measuring position is found on the basis of a prescribed track pitch. A track pitch is measured on the basis of the ratio of N to (n) when the number of frames to be read out at the prescribed speed of rotation of the disk in the measuring position is designated as N and the number of frames to be read out at a prescribed speed of rotation in the measuring position on the disk in which the signal is recorded at the prescribed linear velocity and at the prescribed track pitch is designated as (n).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring a track pitch of a disk on which a signal is recorded at a constant linear velocity.

[0002]

2. Description of the Related Art A disk player which performs a reproducing operation by reading out a signal from a disk on which information data such as music is recorded by a digital signal using an optical pickup has become widespread. One of them is a CD player.

As is well known, a disk used in such a CD player has one block (consisting of 98 frames) with a period of 1/75 second in addition to a main data signal such as music information. Is recorded, a sub-data signal called a sub-coding signal is recorded. Such a subcoding signal is composed of eight channels of P, Q to W channels, in which the P channel contains position index information indicating the position of the beginning of the song, and the Q channel has the starting point of the signal track. And the position index information indicating the absolute elapsed time, the elapsed time for each song, the song number, and the like.

[0004] Therefore, the CD player can perform an operation of detecting a position where a desired song or the like is recorded by using the position index information and performing a reproducing operation, that is, an operation called a search. Have been.
Such a search operation is performed by moving the optical pickup in the radial direction of the disk. Such a movement operation is an operation of moving the main body of the optical pickup at a high speed to near the target position, that is, a pickup feeding operation. And an operation of displacing the objective lens constituting the optical pickup, that is, a track jump operation.

[0005] The linear velocity of a disc in a CD player is not a specific velocity but 1.2 m / sec to 1.4 m / sec.
A range of seconds is allowed. In addition, the distance between tracks recorded on a disk, that is, the track pitch differs from disk to disk. Therefore, it is necessary to change the constant used for obtaining the distance to move the optical pickup when performing the search operation according to the value of the linear velocity or the track pitch.

[0006]

The search operation in the disc player is performed by calculating the number of tracks from the absolute time of the current position and the absolute time of the target position to the target position, and using the optical pickup in accordance with the number of tracks. It is performed by moving the CD-ROM player, and a high-speed search operation is required in the CD-ROM player. In order to perform the search operation at high speed, it is necessary to move the main body of the optical pickup to a position near the target position at high speed, but if the track pitch of the signal recorded on the disc is different, the moving position of the optical pickup Is greatly different from the target position.

An object of the present invention is to provide a method for measuring a track pitch of a signal recorded on a disk in order to quickly perform a search operation.

[0008]

According to the present invention, the linear velocity is measured at a specified position on a disk where a signal is recorded at a constant linear velocity,
The pickup was moved to a measurement position at the set absolute time, the radius at the measurement position was determined based on a prescribed track pitch, and the number of frames read out at the predetermined rotation speed of the disk at the measurement position was measured. Multiplying the ratio of N to n by a specified track pitch, where n is the number of frames read out at the predetermined rotation speed at the measurement position on a disk on which a signal is recorded at a linear velocity and a specified track pitch; Is used to measure the track pitch.

[0009]

1 is a flowchart showing a track pitch measuring method according to the present invention, FIG. 2 is a block circuit diagram of a disk player according to the present invention, and FIG. 3 is a schematic diagram of a disk for explaining the track pitch measuring method according to the present invention. FIG.

In FIG. 2, reference numeral 1 denotes a disk on which a signal is recorded at a constant linear velocity, and 2 denotes a turntable on which the disk 1 is mounted and which drives the disk 1 to rotate. It is configured to be driven. Reference numeral 4 denotes an optical pickup for reading a signal recorded on the disk 1 by irradiating a signal surface of the disk 1 with a light beam. The disk 1 is configured to be moved in the radial direction by rotation (not shown).

Reference numeral 5 denotes an RF signal amplifying circuit for amplifying an RF signal obtained from a photodetector incorporated in the optical pickup 4 and shaping the waveform, and 6 denotes a signal obtained through the RF signal amplifying circuit 5. The optical pickup 4 performs a focusing control operation for focusing a light beam of the optical pickup 4 on a signal surface of the disk 1 and a tracking control operation for causing the light beam to follow a signal track on the signal surface. The pickup control circuit performs a control operation of a track jump by a displacement operation of the objective lens. The operation is performed by controlling a movement of the objective lens.

Reference numeral 7 denotes a digital signal processing circuit which receives a signal output from the RF signal amplifier circuit 5 and demodulates various signals, and 8 denotes a digital signal processed by the digital signal processing circuit 7. Is a signal reproducing circuit to which a data signal is input, and is configured to output a data signal to the computer device 9.

A system control circuit 10 receives a signal demodulated by the digital signal processing circuit 7 and controls various operations according to a switching signal output from the computer device 9. It is configured.

Reference numeral 11 denotes a spindle motor control circuit for controlling the rotation operation of the spindle motor 3, the operation of which is controlled by a motor control signal output from the system control circuit 10. 12
The system control circuit 1 receives a signal output as the spindle motor 3 rotates, for example, a signal obtained from a Hall element incorporated in the spindle motor 3, and outputs a rotation signal corresponding to the input signal.
The system control circuit 10 is configured to count the number of rotations of the spindle motor 3 based on the input signal. That is, the system control circuit 10 can accurately detect, for example, one rotation of the spindle motor 3 by counting the signal obtained from the rotation speed detection circuit 12.

The disk player according to the present invention is configured as described above, and the operation will be described next. When the disc 1 is inserted into a storage section provided in a disc player, the disc 1 is placed on the turntable 2 and a focusing control operation for focusing a light beam emitted from the optical pickup 4 on a signal surface. Is performed.

When the focusing control operation of the optical pickup 4 is performed and the focus is obtained, it is detected that the disk 1 is mounted on the turntable 2. When such a detection operation is performed, the rotation driving operation of the spindle motor 3 by the spindle motor control circuit 14 is started. When such an operation is being performed, a focusing control operation and a tracking control operation are performed by the pickup control circuit 6, and a read operation of disk data or the like recorded on the disk 1 is performed.

When a switching signal for performing a reproducing operation is output from the computer device 9, the system control circuit 10
Control operation, the spindle motor 3 is driven to rotate so that the disk 1 has a constant linear velocity, and a signal reading operation and a signal processing operation from the disk 1 are performed at a constant linear velocity. State.

The signal read by the optical pickup 4 is input to an RF signal amplifier circuit 5 where it is amplified and shaped, and applied to a digital signal processing circuit 7. After the signal input to the digital signal processing circuit 7 is subjected to digital signal processing, its data signal component is demodulated and input to the signal reproduction circuit 8. The data signal input to the signal reproduction circuit 8 is output to the computer device 9 through an output terminal, and the computer device 9 performs a predetermined signal processing operation.

As described above, the signal reading operation in this embodiment is performed. Next, a method of measuring a track pitch, which is the gist of the present invention, will be described.

In the schematic diagram of the disk shown in FIG.
The radius r of the specified position P, which is the start position of the area where the signal is recorded, is specified as 25 mm for a CD disk, and the linear velocity of the disk 1 is measured at this position. If the length of one circumference at the specified position is A, then A
Is expressed as A = 2πr, and when the time required for one rotation is B and the linear velocity is V, the linear velocity V can be obtained from V = A / B, that is, V = 2πr / B.

The time B required for one rotation is measured by detecting one rotation of the disk 1 by the signal obtained from the rotation number detecting circuit 12 and counting the number of frames in the signal read from the disk 1 during that time. I can do it. That is, in the case of a CD disk, the number F of frames read out per second is F = 75 × 98 = 7350, and is counted during one rotation of the disk 1 from the signals obtained by the digital signal processing circuit 7. Assuming that the number of frames is F1, B = F1 / 7350, and the linear velocity V can be obtained.

The linear velocity V can be obtained in this manner. Next, measurement of the track pitch will be described.
Assuming that the radius of the measurement position Q which is the position of the absolute time t set from the specified position P is R, and the area between them is S,

[0023]

(Equation 1)

It is expressed as follows. Track pitch is P,
Assuming that the length of the track from the point P to the point Q is L, the length L is L = S / P, that is,

[0025]

(Equation 2)

It is expressed as follows. Then, since the length L of the track from the point P to the point Q is L = Vt, the radius R of the measurement position Q point is given by

[0027]

(Equation 3)

## EQU1 ##

In equation (3), if the point P is a signal recording start position on the disk 1, the radius r is:
The constant value and the absolute time t of the measurement position Q are, for example, 10
The setting can be fixed, such as minutes 00 seconds. And
Assuming that the track pitch P is a specified value, the radius R at the measurement position Q of the disk on which a signal is recorded at the specified track pitch can be derived from Equation 3. Therefore, at the measurement position Q of the disk where the signal is recorded at the specified track pitch, the number n of frames read out in one rotation is n = 7350 × 2πR / V.

On the other hand, the optical pickup 4
Is moved, and at that position, the number N of frames read in one rotation is counted, and the track pitch can be obtained by multiplying the ratio of N and n by a specified track pitch P.

Next, a method of measuring a track pitch according to the present invention utilizing such a principle will be described with reference to a flowchart shown in FIG.

The operation for measuring the track pitch is as follows.
First, a linear velocity is determined at a specified position on the disk 1 (step A). When the linear velocity is obtained, the optical pickup 4 is moved to the measurement position which is the position of the set absolute time (step B).

The radius of the measurement position is obtained based on the specified track pitch and the linear velocity obtained in step A (step C). When the optical pickup 4 moves to the measurement position, the number N of frames read in one rotation of the disk 1 is counted at that position (step D). When the number of frames N is counted by the operation of step D, the frame is read in one revolution of the disk on which the signal is recorded at the measurement position at the specified track pitch and the linear velocity obtained in step A. Operate the number n,
The track pitch is determined by multiplying the ratio between the number N of frames and the number n of frames by a prescribed track pitch (step E).

The track pitch of the signal recorded on the disk 1 can be measured by the above-described method. In order to detect one rotation of the disk 1, the signal is detected by a Hall element incorporated in the spindle motor 3. With such a configuration, an accurate rotational position can be detected.

Further, by setting the number of movements of the track for moving the optical pickup 4 at the time of the search operation based on the measured track pitch, an accurate track movement operation can be performed. Not only can search speed be increased, but also the search speed can be increased.

In this embodiment, the track pitch is measured by the number of frames read by one rotation of the disk 1. However, the number of rotations is not limited.

[0037]

According to the present invention, the linear velocity is measured at a specified position on the disk where the signal is recorded at a constant linear velocity, and then the pickup is moved to the set absolute time measuring position and the measuring position is measured. Is determined based on a specified track pitch, and the number of frames read at a predetermined rotation speed of the disk at the measurement position is N, a measured linear velocity and a signal recorded at a specified track pitch on a disk. Assuming that the number of frames read at the predetermined rotation speed at the measurement position is n, the track pitch is measured by multiplying the ratio of N to n by a specified track pitch, so that an accurate track pitch can be obtained. I can do it.

Also, in the present invention, a signal for detecting a predetermined rotation of the disk is obtained from a Hall element incorporated in the spindle motor. As a result, the structure can be simplified and the device can be manufactured at low cost.

In the present invention, since the number of tracks to be moved by the optical pickup during the search operation is set based on the measured track pitch, an accurate track movement operation can be performed. In addition, there is an advantage that the search speed can be increased.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a track pitch measuring method of the present invention.

FIG. 2 is a block circuit diagram of a disc player according to the present invention.

FIG. 3 is a schematic diagram of a disk for explaining a track pitch measuring method of the present invention.

[Explanation of symbols]

 Reference Signs List 3 spindle motor 4 optical pickup 6 pickup control circuit 7 digital signal processing circuit 8 signal reproduction circuit 9 computer device 10 system control circuit 11 spindle motor control circuit 12 rotation speed detection circuit

Claims (3)

[Claims] After measuring a linear velocity at a specified position on a disk where a signal is recorded at a constant linear velocity, a pickup is moved to a measurement position for a set absolute time and a radius at the measurement position is specified. N, the number of frames read at a predetermined rotation speed of the disk at the measurement position is N, the measured linear velocity and the measurement position of the disk on which a signal is recorded at a specified track pitch. A method of measuring a track pitch of a disk, wherein the track pitch is measured by multiplying a ratio of N to n by a prescribed track pitch, where n is the number of frames read at the predetermined rotation speed. 2. The track pitch measuring method according to claim 1, wherein a signal for detecting a predetermined number of rotations of the disk is obtained from a Hall element incorporated in the spindle motor. 3. A linear velocity is measured at a predetermined position on a disk where a signal is recorded at a constant linear velocity, and then the pickup is moved to a measurement position for a set absolute time and a radius at the measurement position is defined. N, the number of frames read at a predetermined rotation speed of the disk at the measurement position is N, the measured linear velocity and the measurement position of the disk on which a signal is recorded at a specified track pitch. Assuming that the number of frames read at the predetermined number of rotations is n, the track pitch is measured by multiplying the ratio of N to n by a specified track pitch, and track movement during a search operation is performed based on the measured track pitch. A search method characterized by setting a number.