JP3439125B2 - Track jump detection circuit of disk player - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention 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. 2. Description of the Related Art Disk players that perform 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 have become widespread. A typical example 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 the disk is being read out, if 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.
This will generate a noise signal and adversely affect operations such as tracking servo and focus servo. [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 a 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 in accordance with a track jump. [0006] Recently, different types of discs such as a write-once disc that can perform not only reproduction but also a signal recording operation once and a rewritable disc that can repeatedly perform a recording operation have been commercialized. A read-only disc, a write-once disc, and a rewritable disc have different characteristics in that the amount of light reflected from their signal surfaces is different, so that the level change of the RF signal that occurs when a track jump occurs greatly changes depending on the type of disc. Have. 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 detection outputs for the RF signals (A), (C) and (E), respectively, and the detection output cannot be obtained in (F). become. An object of the present invention is to provide a track jump detection circuit which solves such a problem. According to the present invention, there is provided 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 RF signal output 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 It is composed of FIG. 1 is a circuit diagram showing an embodiment of a disk player according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the present invention, and FIG. FIG. 7 is a signal waveform diagram for performing the following. 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 RF by the offset voltage adding circuit 3 by the offset voltage setting circuit 6
The setting of the additional voltage value for the signal is configured to be set in advance in accordance with the noise amount of the track jump signal due to the difference in the amount of reflected light from various disks. 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 a signal recorded on the disk is being reproduced, an RF signal obtained from a photodetector incorporated in the optical pickup 1 is inputted to an RF signal output circuit 2 and then a predetermined signal is outputted. 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. According to the present invention, an RF signal output circuit for outputting an RF signal obtained from a photodetector for converting light reflected from a disk into an electric signal, and an RF signal output circuit An offset voltage adding circuit for adding an offset voltage corresponding to the characteristics of a disk used for an output RF signal, and an RF signal to which an offset voltage is added by the offset voltage adding circuit is input and a change in the signal level is performed. And a signal level detection circuit whose detection level is fixed, and a track jump of the optical pickup is performed by a detection signal obtained by a comparison operation between the level of the RF signal and the detection level by the signal level detection circuit. Since the detection is performed, even if the detection level for detecting the level change is the same, the characteristics are different. It is possible to reliably detect level changes due to jump the tracks of the disk that. [0019]

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. [Description of Signs] 1 Optical pickup 2 RF signal output circuit 3 Offset voltage addition circuit 4 Signal level detection circuit 6 Offset voltage setting circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-124893 (JP, A) JP-A-7-45024 (JP, A) JP-A-9-147359 (JP, A) JP-A 64-64 59642 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 09-7/10

Claims (1)

(57) [Claim 1] In a disc player provided with an optical pickup incorporating a photodetector for converting light reflected from a disc into an electric signal, the optical pickup is obtained from the photodetector. the RF signal output circuit for outputting an RF signal, the
Used for RF signal output from RF signal output circuit
And an offset voltage adding circuit for adding an offset voltage corresponding to the characteristics of the disk, to the offset voltage adding circuit
Therefore, an RF signal to which an offset voltage is added is input , and a change in the signal level is detected , and the detection is performed.
Become more a signal level detection circuit output level is fixed, the level of the RF signal by the signal level detecting circuit
The detection signal obtained by the comparison operation with the detection level
A track jump detection circuit for a disc player, wherein a track jump of an optical pickup is detected.