JPH0745024A - Servo abnormality misdetecting preventing circuit for optical disk player - Google Patents

Abstract

PURPOSE:To prevent abnormality from being erroneously detected by inhibiting a detecting operation of a servo abnormality detecting circuit when the deterioration of a quantity of reflected light due to a defect of a disk is detected. CONSTITUTION:Under normal control operation of an optical pickup, the quantity of reflected light from a disk surface is larger than a prescribed value, and output terminals 4 and 6 of detecting circuits 3 and 5 respectively are 'L'. When there is a defect on the disk under reproducing operation, the quantity of reflected light is changed, and a signal of a terminal 2 of an output circuit 1 is inputted to the detecting circuit 3 to detect the quantity of light, and when its detecting level is lower than a threshold value VC1, a prescribed rectangular wave is outputted at a terminal 4. On the other hand, when a detecting level of the circuit 5 is lower than a threshold value VC2, a prescribed rectangular wave is outputted at a terminal 6. Then, based on an output signal of the terminal 4 and an output signal of an output terminal 9 of a zero-cross detecting circuit 8, the detecting operation is performed by the servo abnormality detecting circuit 10. By this method, a pulse signal of the terminal 6 is impressed on an inhibiting terminal 12 of the circuit 10 to inhibit the servo abnormality detecting operation.

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 a signal recorded on a disc by an optical pickup, and more particularly to a circuit for preventing erroneous detection of servo abnormality.

[0002]

2. Description of the Related Art Optical disc players, which are constructed so that signals recorded on a disc are read by an optical pickup, are widely used. Such disc players use a light beam emitted from the pickup as a signal surface on the disc. Focusing control operation for focusing the light beam and 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 abnormality in the servo operation.

As a method of detecting such an abnormal servo operation, a method of utilizing the disturbance of the tracking error signal or the change of the amount of light reflected from the disk is generally used.

[0005]

In the disk player incorporating the circuit for detecting the servo abnormality by the above-mentioned method, when the disk has a defect, the disturbance of the tracking signal and the reflected light amount change, so that the servo abnormality occurs. However, there is a problem that the servo is determined to be abnormal and malfunctions.

The present invention is intended to provide a servo abnormality erroneous detection prevention circuit for preventing such a malfunction.

[0007]

A servo abnormality erroneous detection prevention circuit of the present invention detects the amount of light reflected from a disk surface and outputs a pulsed signal when the amount of reflected light is below a first predetermined value. A first reflected light amount detection circuit, a second reflected light amount detection circuit that outputs a pulsed signal when the reflected light amount is less than a second predetermined value that is smaller than the first predetermined value, and the first reflected light amount detection It is composed of a servo abnormality detection circuit for detecting a servo abnormality based on a signal obtained from a circuit output signal and a tracking error signal.

[0008]

The present invention prevents erroneous detection of a servo abnormality by inhibiting the detection operation of the servo abnormality detection circuit when a decrease in the amount of reflected light due to a defect in the disk is detected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit shown in FIG. 1 is an embodiment of the 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 reflection signal output circuit for outputting to the output terminal 2 a signal according to the amount of light reflected from the disk surface of the light beam emitted from the optical pickup, that is, a reflection signal output circuit 3 Is a first reflected light amount detection circuit for detecting the reflected light amount from the signal output to the output terminal 2, and when the reflected light amount is below a first predetermined value, that is, VC1 shown in FIG. An output terminal 4 for outputting an H (high) level signal is provided.

Reference numeral 5 denotes a second reflected light amount detection circuit for detecting the reflected light amount from the signal output to the output terminal 2, and the reflected light amount is a second predetermined value smaller than the first predetermined value VC1, that is, the figure. 2 is provided with an output terminal 6 for outputting a pulsed H-level signal when it is below VC2 shown by A. In such a configuration, the first reflected light amount detection circuit 3
The first predetermined value VC1 which is the detection level of the above is the level of the reflected light amount obtained when the light beam of the optical pickup is off track, that is, when the light beam of the optical pickup deviates from the signal track, and
The second predetermined value VC which is the detection level of the reflected light amount detection circuit 5
2 is the level of the amount of reflected light obtained when the disk has a defect.

Reference numeral 7 is a tracking error signal output circuit for outputting a known tracking error signal to an output terminal based on a signal obtained from a photodetector constituting an optical pickup, and 8 is output from the tracking error signal output circuit 7. Is a zero-cross detection circuit that detects a zero-cross point of the tracking error signal and that outputs a short pulse signal to the output terminal 9 when the zero-cross point is detected.

Reference numeral 10 is a servo abnormality detection circuit for detecting a servo abnormality based on the output signal of the signal output from the first reflected light amount detection circuit 3 and the zero cross detection circuit 8 for detecting the zero cross of the tracking error signal. The servo abnormality detection operation by the servo abnormality detection circuit 10 is performed by the output terminal 4 of the first reflected light amount detection circuit 3 when a pulse signal is output to the output terminal 9 of the zero-cross detection circuit 8.
This is performed depending on whether or not an H level signal is being output to.

The servo abnormality detecting operation by the servo abnormality detecting circuit 10 is performed when the reflected light amount is reduced to a first predetermined value VC1 or less when the pulse signal is output from the zero-cross detecting circuit 8. However, since the output operation of such a pulse signal is performed when the tracking signal is at the zero level, that is, when the optical beam of the optical pickup is following the signal track, the amount of reflected light decreases at this time. That is an abnormal condition. Then, if such a state continues for a predetermined time or more or a predetermined number of times, it is determined that the servo is abnormal, and the output terminal 11
The servo abnormality detection circuit 10 is configured so as to output a detection signal.

When an H level pulse signal is output to the output terminal 6 of the second reflected light amount detecting circuit 5, the signal is prohibited by the inhibit terminal 12 provided in the servo abnormality detecting circuit 10.
And is configured to prohibit the servo abnormality detection operation by the servo abnormality detection circuit 10. The second
The pulse signal output to the output terminal 6 of the reflected light amount detection circuit 5 acts so as to inhibit the servo abnormality detection operation of the servo abnormality detection circuit 10, but also acts on the servo circuit 13 to determine the level of the servo signal. Is configured to be held temporarily.

As described above, the servo error erroneous detection prevention circuit of the present invention is constructed, and the operation of such circuit will be described with reference to the signal waveform diagram shown in FIG. 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 reading operation of 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, and therefore the output terminal of the first reflected light amount detection circuit 3 4 and the output terminal 6 of the second reflected light amount detection circuit 5 do not output an H level signal. When there is a defect in the disc in the reproducing operation state, the amount of reflected light from the disc surface changes, and the signal shown in A of FIG. 2 is output to the output terminal 2 of the reflected signal output circuit 1. When such a signal is input to the first reflected light amount detection circuit 3, the light amount detection operation by the first reflected light amount detection circuit 3 is performed, and the detection level is the first predetermined value V.
Since it is set to C1, the signal shown in B of FIG. 2 is output to the output terminal 4.

When the signal shown in FIG. 2A is input to the second reflected light amount detection circuit 5, the second reflected light amount detection circuit 5 performs the light amount detection operation, but the detection level is the second.
Since the predetermined value VC2 is set, the signal shown at C in FIG. 2 is output to the output terminal 6 thereof. When the signal shown in FIG. 2B is output to the output terminal 4 of the first reflected light amount detection circuit 3, the signal and the output terminal 9 of the zero-cross detection circuit 8 are output.
The detection operation by the servo abnormality detection circuit 10 is performed based on the signal output to. When such an operation is performed, the pulse signal output to the output terminal 6 of the second reflected light amount detection circuit 5 is the inhibition terminal 12 of the servo abnormality detection circuit 10.
Is applied to the servo abnormality detection operation in this state is prohibited.

Therefore, in such a case, the servo abnormality detection signal is not output to the output terminal 11 of the servo abnormality detection circuit 10, and the decrease in the reflected light amount in such a case is caused by the defect of the disk. Therefore, the reproduction operation of the optical disc player is continuously performed. The operation when the disk is defective as described above is performed, but the operation when the servo abnormality occurs next will be described. In such a case, the amount of reflected light decreases to VC1 which is the first predetermined value or less, but VC which is the second predetermined value
It does not drop below 2. Therefore, in such a case, the pulse signal is output to the output terminal 4 of the first reflected light amount detection circuit 3, but the output terminal 6 of the second reflected light amount detection circuit 5 is output.
No pulse signal is output to. Therefore, the servo abnormality detection prohibition operation for the servo abnormality detection circuit 10 is not performed, and the servo abnormality detection operation is performed.
When a detection operation is performed by the servo abnormality detection circuit 10 and a detection signal is output to the output terminal 11, a switching control operation such as changing the disc player from a reproduction operation state to a stop state is performed, and the disc player is not operated. It is possible to prevent a stable state.

The operation of the embodiment of the present invention shown in FIG. 1 is performed as described above. Next, the embodiment shown in FIG. 3 will be described. The same parts as those in the embodiment shown in FIG. 1 are designated by the same reference numerals. In this embodiment, a delay circuit 14 is inserted and connected between the output terminal 6 of the second reflected light amount detection circuit 5 and the inhibition terminal 12 of the servo abnormality detection circuit 10, and the delay circuit 14 is connected to the second reflection light. The light amount detection circuit 5 is provided with an output terminal 15 which outputs a signal delayed by a predetermined time from the output terminal 6 and which is connected to the prohibition terminal 12.

According to this structure, the output terminal 6 of the second reflected light amount detecting circuit 5 is connected to the C of FIG.
When the signal shown in is output, the output terminal 15 of the delay circuit 14
The signal indicated by D in FIG. Therefore, the servo abnormality detection prohibition operation for the servo abnormality detection circuit 10 in the embodiment shown in FIG. 3 is delayed by a predetermined time as compared with the case of the embodiment shown in FIG.

The reason why the servo abnormality detection prohibiting operation for the servo abnormality detecting circuit 10 is delayed is that the output terminal 4 of the first reflected light amount detecting circuit 3 is used when the defect on the disk is large.
This is because the pulse width of the signal output to is increased and the timing deviation from the signal output to the output terminal 6 of the second reflected light amount detection circuit 5 is corrected. According to such a configuration, the servo error erroneous detection prevention operation of the servo error detection circuit 10 can be accurately performed.

In the embodiment shown in FIG. 4, the output terminal 6 of the second reflected light amount detecting circuit 5 and the servo abnormality detecting circuit 10 are arranged to correct the above-mentioned timing deviation which occurs when a defect on the disk is large. A pulse width amplification circuit 16 is inserted and connected between the inhibition terminal 12 and the pulse width amplification circuit 16, and the pulse width amplification circuit 16 outputs the output terminal 6 of the second reflected light amount detection circuit 5.
An output terminal 17 which outputs a signal obtained by pulse-width-amplifying the signal output to
Is equipped with.

According to such a configuration, when the signal shown in C of FIG. 2 is output to the output terminal 6 of the second reflected light amount detection circuit 5 by the above-described detection operation, it is output to the output terminal 17 of the pulse width amplification circuit 16 shown in FIG. The signal indicated by E is output. Therefore, the servo abnormality detection prohibition operation for the servo abnormality detection circuit 10 in the embodiment shown in FIG. 4 is performed for a longer time than in the case of the embodiment shown in FIG.

Since the servo abnormality detection inhibiting operation for the servo abnormality detection circuit 10 is performed for a long time, the signal between the signals output to the output terminal 4 of the first reflected light amount detection circuit 3 and the output terminal 6 of the second reflected light amount detection circuit 5 is Even if there is a timing deviation, the servo error detection circuit 10 can accurately perform the servo error erroneous detection prevention operation. The embodiment shown in FIG. 5 is a combination of the delay circuit 14 shown in FIG. 3 and the pulse width amplification circuit 16 shown in FIG. 4 in order to correct the above-mentioned timing shift. That is, a pulse width amplification circuit 16 for amplifying the pulse width of the pulse signal output to the output terminal 6 of the second reflected light amount detection circuit 5 is provided, and the pulse signal output to the output terminal 17 of the pulse width amplification circuit 16 is delayed. The delay circuit 14 is provided, and the output terminal 15 of the delay circuit 14 is connected to the inhibition terminal 12 of the servo abnormality detection circuit 10.

With such a configuration, when the signal shown in C of FIG. 2 is output to the output terminal 6 of the second reflected light amount detection circuit 5 by the above-described detection operation, the signal is output to the output terminal 17 of the pulse width amplification circuit 16 shown in FIG. The signal indicated by E is output. Then, the signal indicated by F in FIG. 2 is output to the output terminal 15 of the delay circuit 14 to which such a signal is input. Therefore, the servo abnormality detection prohibition operation for the servo abnormality detection circuit 10 in the embodiment shown in FIG. 5 is performed for a long time and with a predetermined time delay as compared with the case of the embodiment shown in FIG.

Since the servo abnormality detection prohibition operation for the servo abnormality detection circuit 10 is performed for a long time with a predetermined time delay,
Even if there is a timing difference between the signals output to the output terminal 4 of the first reflected light amount detection circuit 3 and the output terminal 6 of the second reflected light amount detection circuit 5, the servo error erroneous detection prevention operation of the servo error detection circuit 10 is performed. It can be done reliably. In this embodiment, when the amount of light reflected from the disk surface is below a predetermined value, the output terminal 4 of the first reflected light amount detection circuit 3 and the output terminal 6 of the second reflected light amount detection circuit 5 are bypassed. Although a signal is output, a pulse signal may be output when the amount of light reflected from the disk surface is higher than a predetermined value.

[0027]

According to the present invention, the abnormality detection operation of the servo abnormality detection circuit provided to detect the servo abnormality when the decrease in the amount of reflected light due to the defect of the disk is detected is prohibited. It is possible to prevent the erroneous detection of the servo abnormality that has occurred in the case of the occurrence.

[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.

FIG. 3 is an embodiment of a servo error erroneous detection prevention circuit of the present invention.

FIG. 4 shows an embodiment of a servo error erroneous detection prevention circuit of the present invention.

FIG. 5 shows an embodiment of a servo error erroneous detection prevention circuit of the present invention.

[Explanation of symbols]

 3 First reflected light amount detection circuit 5 Second reflected light amount detection circuit 7 Tracking error signal output circuit 10 Servo abnormality detection circuit 14 Delay circuit 16 Pulse width amplification circuit

Claims (3)

[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 first 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 less than or equal to a first predetermined value, and the reflected light amount from the disc surface A second reflected light amount detection circuit for detecting a light amount and outputting a pulsed signal when the reflected light amount is less than a second predetermined value smaller than the first predetermined value; and an output signal of the first reflected light amount detection circuit. And a servo error detection circuit that detects a servo error based on the signal obtained from the tracking error signal. According to another aspect of the present invention, a servo error erroneous detection prevention circuit for an optical disk player is configured to prohibit the detection operation of the servo error detection circuit when a pulse signal is output from the second reflected light amount detection circuit. 2. A delay circuit for delaying the pulse signal output from the second reflected light amount detection circuit is provided, and the detection operation of the servo abnormality detection circuit is prohibited by the output signal of the delay circuit. The servo error erroneous detection prevention circuit according to claim 1. 3. A pulse width amplification circuit for amplifying the pulse width of the pulse signal output from the second reflected light amount detection circuit is provided, and the detection operation of the servo abnormality detection circuit is prohibited by the output signal of the pulse width amplification circuit. The servo error erroneous detection prevention circuit according to claim 1, wherein: