JPH11353786A - Optical recording medium reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a kind of an optical recording medium and existence of an optical recording medium of an optical recording medium of a standard reflection type and an optical recording medium of a low reflection type securing sufficient reliability. SOLUTION: When focus moving operation in which a focus of an optical pickup 1 is moved in the direction of an optical axis in a state in which an amplifier circuit 5 is set to the standard gain is performed, level detection in which it is detected by a level detecting circuit 6 whether a detected signal level reaches the prescribed reference level or not is performed. When a signal level detected by the level detecting circuit 6 does not reach the prescribed reference level at the time of focus moving operation, the amplifier circuit 5 is switched to high gain by a control circuit 7, while focus moving operation is performed again, and level detection is performed by a control circuit 7. A kind and existence of an optical recording medium are detected by level detection by the level detecting circuit 6 at the time of focus moving operation of two times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium reproducing apparatus for discriminating various optical recording media having different reflectances and detecting the presence or absence of an optical recording medium, and more particularly to discriminating a phase change type optical recording medium. The present invention relates to an optical recording medium device suitable for the present invention.

[0002]

2. Description of the Related Art As an optical recording medium on which a signal is optically read using a light beam such as a laser beam, C is known.
D (Compact Disc) is popular, but this CD
As a family, a phase-change type rewritable CD in which signal recording is performed using a phase change between a crystalline state and an amorphous state, so-called CD-RW (ReWritabl)
e) is proposed.

Meanwhile, a CD-ROM reproducing apparatus utilizing a CD as a read-only memory for digital information needs to be compatible with the reproduction of a CD-RW disc.

This CD-RW disc is a read-only CD (CD-D) having a signal surface formed of an aluminum film.
A or a CD-ROM) disk, the reflected light level is greatly reduced to approximately 12 dB.

Therefore, when reproducing a CD-RW disc, the amount of reflected light is the same as that of a read-only CD disk having a signal surface formed of an aluminum film, or the amount of reflected light at which sufficient S / N is ensured. In order to obtain such a setting, it is necessary to switch the setting corresponding to the reproduction of the CD-RW disc, such as switching the amount of the laser beam emitted from the optical pickup to a high output level.

[0006]

In order to perform this setting change, it is necessary to detect the type of the disk when the disk is mounted, and to perform the type of the disk, the light receiving output level of the optical pickup must be detected. Although it is conceivable to use an intensity difference, the light receiving output level may vary depending on variations in the material of the signal recording surface of the disk or the substrate and the optical characteristics of the disk due to deformation of the disk, or variations in the laser diode of the optical pickup. Due to a change in the laser beam intensity from the optical pickup caused by the temperature characteristic and a change with time, there is a large variation even for the same type of disc.

Therefore, when the light output amount of the laser beam from the optical pickup is set to the standard output level corresponding to the read-only CD disk and the light-receiving output level of the optical pickup is detected, the read-only CD disk and the CD-RW disk Without the disc, the difference in each light receiving output level could not be obtained with a sufficient margin.
Discrimination from a D-RW disc and detection of the presence or absence of the disc cannot be performed with sufficient reliability.

On the other hand, when the type of the disc is detected by setting the output light quantity of the laser beam from the optical pickup to a high output level corresponding to the CD-RW disc, the level of the reflected light quantity is too high for a read-only CD disc. The amplifier circuit that amplifies the light receiving output of the optical pickup is in a clipped state, and as a result, the read-only CD disk
-There is a problem that the disc cannot be distinguished from the RW disc.

Also, in an existing IC in which a digital signal processing circuit for digitally performing signal processing for reproducing a CD disk is integrated into one chip by a semiconductor integrated circuit, a disk detection circuit for detecting the presence or absence of disk detection is incorporated. However, there is a problem that the disc detection circuit generates an erroneous determination that the CD-RW disc is a disc-less disc.

[0010]

According to the present invention, a focus movement operation for moving the focus of an optical pickup in the optical axis direction is performed in a state where an amplification circuit is set to a standard gain, and an amplification is performed by a level detection circuit during the focus movement operation. A signal level output from the circuit is detected, and it is detected that the detected signal level is equal to or higher than a predetermined reference level, thereby determining a standard reflection type optical recording medium.

On the other hand, if the detected signal level does not reach the predetermined reference level, the control circuit switches the amplifying circuit to a high gain and performs the focus moving operation again. The signal level output from the circuit is detected. When the detected signal level is equal to or higher than a predetermined reference level, the optical recording medium of the low reflection type is determined, and when the detected signal level does not reach the predetermined reference level, optical recording is performed. Detects that there is no medium.

[0012]

FIG. 1 is a circuit block diagram of a circuit for detecting a disc type in a CD-ROM reproducing apparatus showing an example of an optical recording medium reproducing apparatus according to the present invention. This circuit comprises a read-only CD disk and a CD-R. (Recordable) Standard reflection type standard disc and low reflection type CD
-Discriminate the disc from the RW disc.

In FIG. 1, reference numeral 1 denotes an optical pickup having a light receiving element 2 for emitting a reading beam to a disk and receiving the reflected light of the reading beam from the disk;
Is a focus drive circuit for driving the focus of the read beam from the optical pickup 1 in the optical axis direction, and 4 is a signal generation circuit for generating a triangular wave signal for forcibly moving the focus of the read beam in the optical axis direction. is there.

The signal generation circuit 4 includes an optical pickup 1
A circuit used for performing a focus search operation for pulling the focal point of the focus servo system into the servo area of the focus servo system is also used.

Reference numeral 5 denotes a focus error amplifier which amplifies and calculates a light receiving output obtained from each light receiving area of the light receiving element 2 to generate a focus error signal indicating a defocus amount of the read beam with respect to the signal surface of the disk. This focus error amplifier 5 has a standard gain for amplifying to an appropriate output level when reproducing a standard reflection type standard disk such as a read-only CD disk and a CD-R disk and a low reflection type CD-RW disk when reproducing. The gain is switchable between a high gain that amplifies to an appropriate output level. Specifically, when the focus error amplifier 5 is set to a high gain, the value is set to a value which is increased by approximately 12 dB which is a light receiving output level difference between the standard disk and the CD-RW disk from a state where the standard gain is set.

Reference numeral 6 denotes a preset reference level Vr.
And a level detection circuit that compares the amplitude level of the focus error signal output from the focus error amplifier 5 with the reference level Vr to detect a level of the focus error signal. As the level detection circuit 6, when a disk detection circuit for detecting the presence or absence of disk detection is incorporated in a semiconductor integrated circuit of a digital signal processing circuit, the disk detection circuit can be used.

A control circuit 7 controls the switching of the gain of the focus error amplifier 5 according to the signal level detected by the level detection circuit 6 and controls the operation of the signal generation circuit 4.

The control circuit 7 includes a judging means 8 for judging the type of the disk and the presence or absence of the disk, and performs the judgment processing and the control processing shown in the flowchart of FIG.

Next, the operation of FIG. 1 will be described with reference to the flowchart of FIG.

Now, when the loading operation of the disk is performed, the control circuit 7 controls to switch the focus error amplifier 5 to the standard gain (step a) and controls to activate the signal generation circuit 4 (step b). . For that reason,
When the focus error amplifier 5 is set to the standard gain, the focus of the read beam from the optical pickup 1 is forcibly moved in the optical axis direction by the triangular wave signal generated from the signal generation circuit 4, and the level detection circuit 6
As a result, the level detection whether the amplitude level of the focus error signal generated from the focus error amplifier 5 is equal to or higher than the reference level Vr is performed (step c).

When the amplitude level of the focus error signal detected by the level detection circuit 6 is equal to or higher than the reference level Vr, and the level detection circuit 6 generates a level detection output to that effect, the judgment means 8 is mounted. It is determined that the disc is a standard disc (step d).

In the case of a CD-R disk, the amplitude level of the focus error signal detected by the level detection circuit 6 is lower than that of a read-only CD disk, but the degree of reduction is negligible compared to that of a CD-RW disk. Therefore, the amplitude level of the focus error signal becomes a value sufficiently higher than the reference level Vr even if the fluctuation is considered.

On the other hand, the amplitude level of the focus error signal detected by the level detection circuit 6 is equal to the reference level V.
When the level is less than r and a level detection output indicating that is generated from the level detection circuit 6, the control circuit 7 performs control to switch the focus error amplifier 5 to a high gain (step e) and again generates a signal. Control for operating the circuit 4 is performed (step f).

Therefore, the focus error amplifier 5
Is set to a high gain, the focus moving operation of forcibly moving the focus of the read beam from the optical pickup 1 in the optical axis direction is performed again, and the level of the focus error signal is increased by the level detection circuit 6. The detection circuit 6 detects again whether the level is equal to or higher than the reference level Vr (step g).

At the time of the second focus movement operation, the amplitude level of the focus error signal detected by the level detection circuit 6 is equal to or higher than the reference level Vr, and a level detection output indicating this is generated from the level detection circuit 6. Then, the judging means 8 inserts the loaded disc into a CD.
-RW is determined (step h).

On the other hand, at the time of the second focus movement operation, the amplitude level of the focus error signal detected by the level detection circuit 6 is lower than the reference level Vr, and the level detection output from the level detection circuit 6 indicates that. Is generated, the judging means 8 judges that no reproducible disc has been mounted and judges that there is no disc (step i).

As described above, the circuit shown in FIG. 1 detects that the amplitude level of the focus error signal obtained during the first focus movement operation has reached the reference level Vr, discriminates the standard disk, and performs the second focus movement. The CD-RW is determined by detecting that the amplitude level of the focus error signal obtained at the time of operation has reached the reference level Vr, and the amplitude level of the focus error signal obtained at the time of the second focus movement operation is at the reference level. It is detected that the voltage has not reached Vr, and the absence of the disk is detected.

That is, the detection of the amplitude level of the focus error signal during the first and second focus movement operations is performed by switching the gain of the focus error amplifier 5, and the gain of the focus error amplifier 5 is set to the standard disk and the CD. -The same level detection is performed by the level detection circuit 6 without changing the reference level Vr during the first and second focus movement operations because the setting is made so as to compensate for the difference between the light receiving output level with the RW disk. In the disc discrimination between the standard disc and the CD-RW,
And detection of no disk.

Here, the level detection by the level detection circuit 6 is a simple comparison as to whether or not the amplitude level of the focus error signal has reached the reference level Vr, so that highly reliable detection can be performed.

[0030]

As described above, the present invention provides the first time and the second time.
At the time of the first focus movement operation, the signal level of the light receiving output of the optical pickup obtained through the amplifier circuit is detected by switching the gain of the amplifier circuit. In the above, the same level detection is performed by the level detection circuit without changing the reference level, thereby discriminating between the standard reflection type optical recording medium and the low reflection type optical recording medium, and detecting the absence of the optical recording medium. Can be performed.

In particular, since the level detection by the level detection circuit is a simple comparison as to whether or not the signal level of the light receiving output has reached the reference level, the hardware and software can be simplified. In addition, the reliability of the level detection is high, and detection errors of the type and presence / absence of the optical recording medium can be prevented.

Further, the light receiving output of the optical pickup for performing level detection by the level detecting circuit is the amplitude level of the focus error signal obtained without driving the optical recording medium, and the optical recording medium is used as the RF signal or the tracking error signal. Since the signal is not a signal obtained by driving the optical recording medium, the type and presence / absence of the optical recording medium can be detected while the optical recording medium is stopped.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a circuit for detecting a disc type in a CD-ROM reproducing device showing an example of an optical recording medium reproducing device according to the present invention.

FIG. 2 is a flowchart showing a judgment process and a control process in a control circuit 7;

[Explanation of symbols]

 Reference Signs List 1 optical pickup 3 focus drive circuit 4 signal generation circuit 5 focus error amplifier 6 level detection circuit 7 control circuit

Claims (2)

[Claims] 1. An optical recording medium reproducing apparatus capable of reproducing a standard reflection type optical recording medium having a standard reflectance and a low reflection type optical recording medium having a lower reflectance than the standard reflection. A signal generation circuit for generating a signal for forcibly moving the focus of the pickup in the optical axis direction, and a light receiving output of an optical pickup for optically reading a recording signal of an optical recording medium are amplified. An amplifier circuit that can be switched to a high gain higher than the standard gain, a level detection circuit that detects a signal level of a light receiving output of the optical pickup obtained through the amplification circuit, and a signal detected by the level detection circuit A control circuit for controlling the switching of the gain of the amplifier circuit according to the level, and for controlling the operation of the signal generation circuit. With the gain set, a focus movement operation of moving the focus of the optical pickup in the optical axis direction is performed, and at that time, a level detection is performed to determine whether or not the signal level detected by the level detection circuit has reached a predetermined reference level. When the signal level detected by the level detection circuit does not reach a predetermined reference level during the focus movement operation, the control circuit switches the amplification circuit to a high gain, and performs the focus movement operation again to perform the focus movement operation. An optical recording medium reproducing apparatus wherein level detection is performed by a level detection circuit, and the type and presence / absence of an optical recording medium are detected by the level detection by the level detection circuit during the two focus movement operations. . 2. The method according to claim 1, wherein the amplifying circuit is a focus error amplifier for generating a focus error signal for an optical recording medium, and an amplitude level of the focus error signal is used as a light receiving output of an optical pickup for performing level detection by the level detection circuit. The optical recording medium reproducing device according to claim 1, wherein: