JPH0729195A - Preventive circuit of erroneous detection of servo abnormality for optical disk player - Google Patents

Abstract

PURPOSE:To obtain a circuit which prevents the erroneous detection of a servo abnormality for an optical pickup which reads out a signal recorded in a disk. CONSTITUTION:This circuit is composed of a reflected-light-quantity detection circuit 1 which detects a quantity of light reflected by a disk face and which outputs a pulse-shaped signal when the quantity of reflected light is at a prescribed value or lower and of a pulse-width discrimination circuit 5 which discriminates the pulse widths of the pulse signal output from the reflected-light- quantity detection circuit 1. Then, when the pulse width is at a prescribed value or lower, the pulse signal which is output from the reflected-light-quantity detection circuit 1 is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc player configured to read out a signal recorded on a disc by an optical pickup, and more particularly to an erroneous servo error detection prevention circuit.

[0002]

2. Description of the Related Art Optical disc players, which are constructed so that a signal recorded on a disc is read out by an optical pickup, are widely used. Such disc players use a light beam emitted from the pickup as a signal on the disc. The focusing control operation for focusing on the surface and the tracking control operation for causing the light beam to follow the signal track are performed.

The focusing control operation and the tracking control operation are performed by detecting a change in the amount of light reflected from the signal surface on the disk. Such operations are generally called focus servo and tracking servo. Has been. When an error occurs in the servo operation when performing the tracking servo operation, the operation of the disk player becomes unstable. Therefore, the disk player is generally equipped with a circuit for detecting an error in the servo operation. As a method of detecting such a servo operation abnormality,
There is a method of detecting the disturbance of the track error signal and the change of the amount of light reflected from the disc.

[0004]

Since the above-mentioned method relies on the track information formed on the disk, the track error signal is disturbed due to the waviness of the track, and the amount of light reflected from the disk is affected by these errors. Information may leak and cause fluctuations. As a result, there is a problem that a servo abnormality cannot be detected, or an erroneous detection operation is performed if a servo abnormality occurs even if there is no abnormality.

The present invention is intended to provide a servo abnormality erroneous detection prevention circuit which is improved in this respect.

[0006]

A servo error erroneous detection prevention circuit of the present invention is an optical disc player configured to perform a tracking servo control operation of an optical pickup based on a signal obtained from the optical pickup. A reflected light amount detection circuit that detects the amount of light reflected from the surface and outputs a pulsed signal when the reflected light amount is less than a predetermined value, and a pulse width of the pulse signal output from the reflected light amount detection circuit are identified. In addition, when the pulse width is less than or equal to a predetermined value, the signal removing circuit removes the pulse signal output from the reflected light amount detecting circuit.

[0007]

According to the present invention, when the pulse width of the pulse signal output from the reflected light amount detecting circuit is less than a predetermined value, the pulse signal is removed to prevent the malfunction of the servo abnormality detecting circuit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit shown in FIG. 1 is a servo error erroneous detection prevention circuit of the present invention, and the optical pickup and its tracking servo circuit are omitted. In the figure, 1 is a reflected light amount detection circuit for detecting the amount of light reflected from the disc surface of the light beam emitted from the optical pickup, and outputs a pulsed signal when the reflected light amount is below a predetermined value. The output terminal 2 is provided.

Reference numeral 3 denotes an edge detection circuit which receives the pulse signal output from the reflected light amount detection circuit 1 and detects an edge of the pulse signal, that is, a rising edge and a falling edge. It is configured to output an H (high) level signal to the output terminal 4. 5
Is the pulse of the pulse signal output from the reflected light amount detection circuit 1 by measuring the time between the input signal and the signal output to the output terminal 4 of the edge detection circuit 3 A pulse width identification circuit for identifying a width, which outputs a H level signal for a short time when the pulse width of the pulse signal is, for example, 1 μS or more, and an H level signal when the pulse width is less than 1 μS. A second signal output terminal 7 for outputting a signal is provided.

Reference numeral 8 is a pulse addition circuit whose operation is controlled by a signal output to the first signal output terminal 6 of the pulse width identification circuit 5, and an H level signal is output from the first signal output terminal 6. Then, an output terminal 9 for outputting an H-level additional pulse having a pulse width of, for example, 5 μS is provided. Reference numeral 10 is a pulse cut circuit whose operation is controlled by a signal output to the second signal output terminal 7 of the pulse width identification circuit 5, and when an H level signal is output from the second signal output terminal 7, for example, Output terminal 1 that outputs a cut pulse of L (low) level having a pulse width of 2 μS
1 is provided.

Reference numeral 12 is a delay circuit for receiving the signal output to the output terminal 2 of the reflected light amount detection circuit 1 and delaying the signal to output it to the output terminal 13. Reference numeral 14 is an output terminal of the pulse cut circuit 10. An AND circuit having the signal output to 11 and the signal output to the output terminal 13 of the delay circuit 12 as input signals, and 15 the signal output to the output terminal 9 of the pulse adding circuit 8 and the AND circuit 1
4 is an OR circuit using the output signal of No. 4 as an input signal.

Reference numeral 16 is a servo abnormality detection circuit which receives the output signal of the OR circuit 15, and when the OR circuit 15 outputs an H level signal, it is determined that an abnormality has occurred in the servo operation of the optical pickup. Is configured to. The servo error erroneous detection prevention circuit of the present invention is configured as described above, and the operation of the circuit will be described below.

When the reproduction operation of the optical disc player is started, the control operation of the optical pickup, that is, the focusing control operation and the tracking control operation are performed and the operation of reading the signal recorded on the disc is performed.
In such a reproducing operation state, when the control operation of the optical pickup is normally performed, the amount of light reflected from the disk surface is larger than a predetermined value, so that the output terminal 2 of the reflected light amount detection circuit 1 is pulsed. No signal is output.

When the amount of reflected light from the disk surface decreases due to track waviness or some other cause in the reproducing operation state, the signal shown in FIG. 2A is output from the output terminal 2 of the reflected light amount detection circuit 1. In FIG. 2A, N1 and N
Reference numeral 2 is a pulse signal due to a decrease in the amount of reflected light due to track waviness, which is not a servo error. Then, T1, T2, T3, T4 and T5 in A of FIG.
Is a pulse signal due to a decrease in the amount of reflected light due to a servo abnormality.

Since the pulse signal output to the output terminal 2 of the reflected light amount detection circuit 1 is input to the edge detection circuit 3, an H level signal is output to the output terminal 4 every time an edge is detected. . Since the signal output to the output terminal 4 is input to the pulse width identification circuit 5, the reflected light amount detection circuit 1 is measured by measuring the interval between the input signals.
The pulse width of the output pulse signal can be identified.

When the signal shown in FIG. 2A is output to the output terminal 2 of the reflected light amount detection circuit 1, the pulse width of the pulses N1 and N2 is less than 1 μS, and the pulses T1, T2, T
The pulse width of 3, T4 and T5 is 1 μS or more. The pulse width of the pulse signal is identified by the pulse width identification circuit 5, and when the pulse width is 1 μS or more, an H level signal is output to the first output terminal 6 and when the pulse width is less than 1 μS. Outputs an H level signal to the second output terminal 7.

When the H-level signal is output to the first output terminal 6, the pulse adding circuit 8 is put into operation, and an additional pulse having a pulse width of 5 μS is output to the output terminal 9.
The additional pulse is continuously output to the output terminal 9 while the signal having the pulse width of 1 μS or more is output from the reflected light amount detection circuit 1. The signal shown in is output.

Further, when an H level signal is output to the second output terminal 7, the pulse cut circuit 10 is activated, and an L level cut pulse having a pulse width of 2 μS is output to the output terminal 11. Therefore, the signal shown in C of FIG. 2 is output to the output terminal 11. When the signal indicated by C in FIG. 2 is output to the output terminal 11 of the pulse cut circuit 10, the output terminal of the AND circuit 14 which receives the signal and the signal delayed by the delay circuit 12 as input signals is The signal indicated by D is output. 2D
As shown in, the AND circuit 14 outputs a signal from which the pulse signals N1 and N2 of the pulse signal output to the output terminal 2 of the reflected light amount detection circuit 1 are removed. That is, the pulse signal N1 output when the amount of reflected light is reduced due to the waviness of the track, not the abnormality of the servo.
And N2 can be removed.

The output terminal 9 of the pulse adding circuit 8 is shown in FIG.
2 is output to the output terminal of the OR circuit 15 which receives the signal and the signal from the AND circuit 14 shown in D of FIG. 2 as an input. Will be. When the signal shown by E in FIG. 2 is output to the output terminal of the OR circuit 15, the abnormality detection operation is performed by the servo abnormality detection circuit 16 to which the signal is input. And
Comparing the signal input to the servo abnormality detection circuit 16 with the signal output to the output terminal 2 of the reflected light amount detection circuit 1, the signals are input to the servo abnormality detection circuit 16 as apparent from A and E of FIG. The pulse signals N1 and N2 output due to the fact that the servo is not abnormal are removed, and the pulse signals T1, T2, T3, T4 and T5 output due to the servo abnormality are continuous pulse signals. Therefore, it is possible to accurately detect an abnormality in the servo operation.

In this embodiment, a pulsed signal is output to the output terminal 2 of the reflected light amount detection circuit 1 when the amount of light reflected from the disc surface is below a predetermined value. On the other hand, it is also possible to output a pulsed signal when the amount of light reflected from the disk surface has risen above a predetermined value. Further, in the present embodiment, the case where the signal removal circuit is configured by the edge detection circuit 3, the pulse width identification circuit 5, the pulse addition circuit 8, the pulse cut circuit 10 and the like has been described, but it goes without saying that other configurations may be adopted. It is possible.

[0021]

According to the present invention, when the pulse width of the pulse signal output from the reflected light amount detection circuit is less than a predetermined value, the pulse signal is removed. Even if there is a change, there is no need to perform a servo abnormality detection operation, and a servo abnormality erroneous detection prevention operation can be performed.

[Brief description of drawings]

FIG. 1 is an embodiment of a servo error erroneous detection prevention circuit of the present invention.

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

[Explanation of symbols]

 1 reflected light amount detection circuit 3 edge detection circuit 5 pulse width identification circuit 8 pulse addition circuit 10 pulse cut circuit 16 servo error detection circuit

Claims (1)

[Claims] 1. An optical pickup is configured to read a signal recorded on a disc, and a tracking servo control operation of the optical pickup is performed based on a signal obtained from the optical pickup. In an optical disc player, a reflected light amount detection circuit that detects the amount of light reflected from the disc surface and outputs a pulsed signal when the reflected light amount is below a predetermined value, and a pulse signal output from the reflected light amount detection circuit And a signal removing circuit for removing the pulse signal output from the reflected light amount detection circuit when the pulse width is less than a predetermined value, and the servo is performed based on the signal output from the signal removing circuit. Support for optical disk players characterized by detecting abnormal operation Abnormal error detection circuit.