JP2000030267A - Track jump detection circuit of disk player - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the track jump detection circuit of a disk player constituted so as to read out a signal recorded on a disk by an optical pickup. SOLUTION: This track jump detection circuit is constituted of an RF signal output circuit 2 which outputs an RF signal obtained from a photodetector assembled in the optical pickup 1, an offset voltage addition circuit 3 adding an offset voltage to the RF signal in response to the disk to be used and a signal level detection circuit 4 inputting the RF signal outputted from the offset voltage addition circuit 3 and detecting the change of the signal level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a track jump detection circuit of a disk player configured to read out a signal recorded on a disk by an optical pickup.

[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.

[0003] Such a disk player is configured to perform a signal reading operation by accurately focusing a light beam emitted from an optical pickup on a signal surface of a disk and making the beam follow a signal track. ing.

[0004]

In a disk player in a state where a signal recorded on a disk is being read out, when external vibration is applied,
A phenomenon called track jump occurs in which the light beam is displaced to another position. When such a track jump occurs, the signal read from the disk disappears.
A noise signal is generated, and the operation of the tracking servo, the focus servo, and the like is adversely affected.

[0005] In order to solve such a problem, an RF detector obtained from a photodetector incorporated in an optical pickup is used.
It is configured to detect the occurrence of a track jump by detecting a change in the signal level, and to perform a control operation of a tracking servo or a focus servo. R
The operation of detecting the change in the level of the F signal is configured to be performed based on whether or not the level of the RF signal exceeds a predetermined detection level due to a track jump.

[0006] Recently, different types of disks have been commercialized, such as a disk that can perform not only reproduction but also a signal recording operation only once and a disk that can repeatedly perform a recording operation. Such a disc has a characteristic that the level change of the RF signal that occurs when a track jump occurs greatly changes depending on the type of the disc.

FIGS. 3 (A), 3 (C) and 3 (E) show changes in the level of the RF signal due to the skipping of tracks on different disks, indicating that the changes in the level of the RF signal are different. ing. In response to such a level change, the detection level for detecting a track jump is set and fixed to the voltage V, so that the signal output in accordance with the signal level detection changes. (B), (D) and (F) of FIG. 3 show the detection outputs for the RF signals (A), (C) and (E), respectively. become.

An object of the present invention is to provide a track jump detection circuit which solves such a problem.

[0009]

SUMMARY OF THE INVENTION The present invention provides an RF signal output circuit for outputting an RF signal obtained from a photodetector incorporated in an optical pickup, and an RF signal output circuit corresponding to a disk used. An offset voltage adding circuit for adding an offset voltage to the RF signal output from the circuit, and a signal level detecting circuit for receiving the RF signal output from the offset voltage adding circuit and detecting a change in the signal level. Have been.

[0010]

FIG. 1 is a circuit diagram showing an embodiment of a disc player according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the present invention, and FIG. 3 is a diagram for explaining the operation of a conventional apparatus. It is a signal waveform diagram.

In FIG. 1, reference numeral 1 denotes an optical pickup for reading out a signal recorded on a disk, and incorporates a photodetector for converting light reflected from the disk into an electric signal. An RF signal output circuit 2 receives an RF signal obtained from a photodetector incorporated in the optical pickup 1 and amplifies and outputs the signal. An offset voltage adding circuit for receiving an RF signal and adding an offset voltage to the signal is a signal level detecting circuit for receiving an RF signal output from the offset voltage adding circuit 3, and a level change of the RF signal. Is higher than a predetermined level V, a detection signal of H (high) level is outputted to an output terminal.

Reference numeral 5 denotes a control circuit to which a detection signal output from the signal level detection circuit 4 is input, and is configured to perform various control operations associated with track jump detection. Reference numeral 6 denotes an offset voltage setting circuit whose operation is controlled by the control circuit 5, and has an operation of setting a voltage added by the offset voltage adding circuit 3.

In such a configuration, the setting of the additional voltage to the offset voltage adding circuit 3 by the offset voltage setting circuit 6 is configured to be a voltage set in advance in accordance with the noise amount of the track jump signal. .

As described above, the track jump detecting circuit of the present invention is configured. Next, the operation of the circuit having such a configuration will be described.

In a state where the signal recorded on the disk is being reproduced, an RF signal obtained from a photodetector incorporated in the optical pickup 1 is input to an RF signal output circuit 2 and then a predetermined signal is output. And amplified and output. RF output from the RF signal output circuit 2
The signal is input to the offset voltage adding circuit 3, but is output after adding the offset voltage set by the offset voltage setting circuit 6 corresponding to the type of the disk.

FIGS. 2A, 2C and 2E are waveform diagrams of the RF signal output from the offset voltage adding circuit 3, and FIG.
In (C) and (E), offset voltages of the voltage B1 and the voltage B2 are added, respectively. Such a signal is input to the signal level detection circuit 4 and a level change of the signal is detected at the same detection level V. In such a case, (B) and (D) of FIG. As shown in (F) and (F), detection outputs can be obtained for all disks. Therefore, it is possible to detect the track jump phenomenon in all the disks.

Further, by monitoring the detection output output from the signal level detection circuit 4 during the reproducing operation of various disks, the offset voltage can be set in correspondence with various disks. Track jumps can be detected under optimal conditions.

[0018]

According to the present invention, an R signal for outputting an RF signal obtained from a photodetector incorporated in an optical pickup is provided.
An offset voltage adding circuit for adding an offset voltage to the RF signal output from the F signal output circuit is provided, and track jump is detected by detecting a level change of the RF signal output from the offset voltage adding circuit. Therefore, even if the detection level of the level change is the same, it is possible to reliably detect a track jump of a disc having a different characteristic.

Further, according to the present invention, the adjustment of the additional voltage set by the offset voltage setting circuit is performed based on the detection output output from the signal level detection circuit, so that a highly accurate adjustment operation can be performed. I can do it.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a disc player according to the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the present invention.

FIG. 3 is a signal waveform diagram for explaining the operation of the conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical pickup 2 RF signal output circuit 3 offset voltage adding circuit 4 signal level detection circuit 6 offset voltage setting circuit

Claims (3)

[Claims] 1. An RF signal output circuit for outputting an RF signal obtained from a photodetector in a disc player provided with an optical pickup incorporating a photodetector for converting light reflected from the disc into an electric signal. And an offset voltage adding circuit for adding an offset voltage to the RF signal output from the RF signal output circuit corresponding to the disk to be used, and an RF signal output from the offset voltage adding circuit is input and A signal level detection circuit for detecting a change in the signal level, wherein the signal level detection circuit detects a change in the level of the RF signal to detect a track jump; Detection circuit. 2. The track jump detecting circuit according to claim 1, further comprising an offset voltage setting circuit for setting a voltage added by the offset voltage adding circuit. 3. The track jump detection circuit according to claim 2, wherein the adjustment of the additional voltage set by the offset voltage setting circuit is performed based on a detection output output from the signal level detection circuit. .