JPH0359491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc reproducing device that uses a light beam to read information from a disc on which information is recorded, and in particular, the present invention relates to an optical disc reproducing device that uses a light beam to read information from a disc on which information is recorded. The present invention relates to an optical disc playback device that can automatically detect when the non-information reading side is mounted with the non-information reading side reversed.

BACKGROUND ART AND PROBLEMS There is a digital audio system in which an audio signal is pulse encoded and recorded as an array of pits, and the audio signal can be reproduced by optically reading the pits, for example.・A disk is proposed. In such a digital audio disk, unlike a conventional record with sound grooves, only one side is used as an information reading surface (hereinafter referred to as the surface), and the other side is used as a non-information reading surface. The mainstream is what is called a single-sided readable disc, on which a label is affixed to the reading side (hereinafter referred to as the back side) with, for example, the title of the recorded song. Therefore, when a digital audio disk for playback is attached to an optical disk playback device that makes a light beam incident on the surface of the digital audio disk and plays back audio signals from the surface, It is expected that due to an operator's mistake, the front side and the back side may be confused and installed. In such a case, for example, unless the operator notices a mistake in the mounting of the disc, the disc playback device will perform normal operations at the start of playback, such as focusing control of the light beam incident on the disc. It is an operation that draws the circuit system into a controlled operating state.
Even though the focus pull-in operation is performed, the playback start state,
That is, the focus pull-in state may not be achieved, and there is a risk that the focus pull-in operation will be repeatedly performed in vain. Continuing such useless repetitive operations may cause failure of the disc playback device.

Therefore, in order to eliminate the inconvenience caused by such an inappropriate device for the disk, the applicant first discovered that the disk was not installed correctly by using a signal from a focus pull-in circuit that causes the focus pull-in operation. An optical disc playback device is equipped with a function such as detecting the detection and returning the disc to the unloading state based on the detection, or emitting a warning sound to notify the operator of the situation. is suggesting. In the optical disc playback device proposed by the present applicant, when a disc is properly installed in the disc playback device, a light beam incident on the surface of the disc from an optical pick-up serving as information reading means is transmitted. , is reflected from the surface of the disk and reaches a light detection section that is capable of detecting the focus state, which is incorporated into an optical pickup, for example, so that the focus pull-in state is detected based on this reflected light beam, This cancels the focus retraction operation and switches to the focus control operating state in which normal focus control is performed. However, if the disk is installed incorrectly, the light beam from the optical pickup will not reach the back of the disk. However, in this case, a label or the like is attached to the back of the disc, and the incident light beam is hardly reflected. Therefore, the reflected light is not reflected to the light detection unit that can detect the focused state. This method focuses on the fact that the beam is not allowed to arrive, the focus pull-in state is not detected, and the focus pull-in operation continues to be performed repeatedly. As a result, if the focus pull-in operation continues for a predetermined number of times or for a period of time corresponding to the predetermined number of times, it is determined that the disk has been installed incorrectly, that is, its front and back surfaces have been mixed up. Therefore, it can detect the signal from the focus pull-in circuit that causes the focus pull-in operation, and based on that signal, it can detect that the disk is not installed correctly. It is possible to prevent unnecessary repetition of the focus pull-in operation by returning the focus to the unloading state or by emitting a warning sound or the like to notify the operator.

The optical disc playback device previously proposed by the present applicant employs the above-mentioned detection method, and therefore only detects discs whose back surface is a non-reflective surface. The back side can be automatically detected. However, not all digital audio disks have a label affixed to the back side to make them non-reflective, and for reasons of design, the back side also reflects light. If a disk whose back surface is also a reflective surface is mounted, it will not be possible to distinguish between the front and back sides of the disk even in the above-mentioned optical disk playback device. When a disc whose back surface is also a reflective surface is mounted in such a way that the light beam is incident on the back surface, the focus pull-in operation is performed normally and the focus pull-in state is established, and the disk playback device Put into play state. However, since a regular reproduction signal cannot be obtained, for example, the rotation speed of the disk rotation motor is not controlled correctly using the reproduction signal, and the disk rotation motor runs out of control. There is a risk that the inconvenience may occur.

Purpose of the Invention In view of the above, the present invention provides an object not only when a disk whose back surface is a non-reflective surface is mounted, but also when a disk whose back surface reflects light is mounted. Also, it can reliably automatically detect that the disk has been installed so that a light beam is incident on the back side, and it can also automatically return the disk to the unloading state or emit a warning sound. Another object of the present invention is to provide an improved optical disc playback device that is equipped with functions such as displaying a warning.

SUMMARY OF THE INVENTION The optical disk reproducing apparatus according to the present invention includes a focus pull-in circuit that can repeatedly perform a focus pull-in operation, and a focus pull-in operation that can be performed by the focus pull-in circuit until a predetermined period of time elapses from the first start of the focus pull-in operation by the focus pull-in circuit. Based on the fact that a signal indicating the end of the focus pull-in operation is not obtained from the focus pull-in circuit until the number of pull-in operations reaches a predetermined number, the light beam is made to be incident on the back surface of the disk. A first determination unit that determines that the disc is installed, and a determination signal that determines whether or not a regular playback signal is being obtained from the disk and that takes a specific state when a regular playback signal is not obtained. When a signal indicating the end of the focus pull-in operation is obtained from the discrimination circuit and the focus pull-in circuit, the disk and a second determination section that determines that the device is attached in such a way that a light beam is incident on the back surface of the device. If a disk with a non-reflective back surface is installed, the first determination section described above automatically detects the back surface, and a disk with a non-reflective back surface is also installed. If the above-mentioned second determination unit automatically detects the back side, in either case,
The disk is returned to the unloading state,
Alternatively, a warning sound or the like is emitted to notify the operator, and the inconvenience caused by the disk being mounted in such a way that a light beam is incident on its back surface can be avoided. It will be done.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block connection diagram showing essential parts of an example of an optical disc playback device according to the present invention. A disk 3 is mounted on a disk mounting section 2 which is rotated by a disk rotation motor 1. When a signal is to be generated from the disk 3, the playback start button provided on the operation panel 4 is first pressed, whereby the command signal _S1 obtained from the output terminal of the command signal generation circuit 5 becomes low. The signal is changed from the level to the high level and is supplied to the set terminal (S) of the timer 6 and the first input terminal of the switching control circuit 7. The timer 6 starts measuring time when the command signal _S1 changes from a low level to a high level, and measures the rise from a low level to a high level of an output signal sent from the output end of a focus discrimination circuit, which will be described later. It stops time measurement when there is a change, and
When a preset predetermined time, which is longer than the normal focus pull-in operation time, is measured, an output signal, which will be described later, is generated.

When the high level command signal S ₁ is supplied to the switching control circuit 7 , the output signal S ₂ from its output terminal changes from a low level to a high level and is supplied to the input terminal of the voltage generating circuit 8 . When the voltage generation circuit 8 receives this high-level output signal _S2 , it generates a focus pull-in voltage e that changes in a predetermined manner and repeats the change at a predetermined period.
Then, this focus pull-in voltage e is applied to the focus adjustment means 10 via the focus drive circuit 9.
The light beam is made incident on the disk 3 according to the focus pull-in voltage e, and
The entire optical pickup 11 that receives the reflected light beam from the disk 3 or the objective lens built therein is swung to change the focus state. Here, when the disk 3 is properly mounted, the light beam from the optical pickup 11 is made incident on the surface of the disk 3,
It is reflected by the surface and returns to the optical pickup 11. This optical pickup 11 has a built-in photodetector that can detect the focus state, and a focus error voltage e _f is determined depending on the focus state of the light beam incident on the surface of the disk 3.
to occur. This focus error voltage e _f
For example, when the focus state is overfocus, it becomes a positive voltage, when it is underfocus, it becomes a negative voltage, and when it is just focus, it becomes zero. By supplying this focus error voltage e _f to the focus discrimination circuit 12, the point where the focus error voltage e _f becomes zero voltage, that is, the point of just focus, is determined in the focus discrimination circuit 12. Detected. At the detected point, the output signal _S3 of the focus discrimination circuit 12 changes from low level to high level. This output signal _S3 is transmitted to the switch 13
is supplied to the control terminal of switch 13, and when the output signal _S3 changes from low level to high level, this switch 13
is switched from off to on. Also, the output signal
S ₃ is also supplied to the second input terminal of the switching control circuit 7, and when the output signal S ₃ is switched from a low level to a high level, the output signal S ₂ of the switching control circuit 7 is switched from a high level to a low level. As a result, the focus pull-in voltage e cannot be obtained from the voltage generating circuit 8. Therefore, instead of the focus pull-in voltage e that has been supplied to the focus drive circuit 9, the focus error voltage e _f from the optical pickup 11 is supplied to the focus drive circuit 9 via the switch 13. In response to the,
A focus drive signal is obtained from the focus drive circuit 9 and applied to the focus adjustment means 10, so that a focus control operation based on the focus error voltage e _f is performed. That is, a switching control circuit 7, a voltage generation circuit 8, a focus drive circuit 9,
When the focus pull-in operation by the focus pull-in circuit including the focus adjustment means 10 and the focus discrimination circuit 12 is canceled, the focus drive circuit 9, the focus adjustment means 10,
The focus control circuit system formed by the optical pickup 11 and the switch 13 enters a focus control operating state. Here, a change in the output signal _S3 of the focus discriminating circuit 12 from a low level to a high level is a signal indicating the end of the focus pull-in operation.

In addition, the output signal S ₃ of the focus discrimination circuit 12
is supplied to the reset terminal (R) of the timer 6, and this timer 6 stops measuring time when the output signal _S3 changes from low level to high level.

On the other hand, the disk 3 is attached to the disk attachment part 2 with the front and back sides reversed, and as a result, the back side of the disk 3 (in this case, the back side of the disk 3 has a label etc. affixed to it, for example). optical pick-up 11 on the non-reflective surface)
However, since the light beam is not reflected from this back surface and does not return to the optical pickup 11, the focus error voltage e _f
does not occur. For this reason, the focus discrimination circuit 1
In case 2, the state in which the just focus point is not detected continues. Therefore, the output signal _S3 of the focus discrimination circuit 12 maintains a low level, and therefore the focus discrimination circuit system does not take the focus control operation state, and the switching control circuit 7
The output signal S ₂ from the voltage generating circuit 8 is supplied to the focus drive circuit 9 while the output signal S 2 from the voltage generation circuit 8 is kept at a high level, and the focus pull-in operation by the focus pull-in circuit continues to be performed repeatedly. .

Furthermore, since the output signal _S3 of the focus discriminating circuit 12 remains at a low level, the time measurement of the timer 6 does not stop, but instead measures a preset predetermined time. Then, when a predetermined time is measured, an output signal _S4 is generated. This output signal _S4 is supplied to the disk loading mechanism 14 and the warning section 15, and the disk loading mechanism 14
Upon receiving the output signal S ₄ , the disk 3 is brought into an unloading state in which it is removed from the disk mounting section 2 , and upon receiving the output signal S ₄ , the warning section 15 is configured to:
Perform a warning operation such as displaying a warning display or emitting a warning sound.

Therefore, when the disk 3 whose back surface is a non-reflective surface is attached to the disk mounting portion 2 with the front and back surfaces reversed, the focus retracting operation is repeatedly started a predetermined number of times, for example, three times, and the timer is activated. 6
When the time required for the focus pull-in operation to be repeated three times is measured from the rising edge of the command signal _S1 from the command signal generating circuit 5, the light beam from the optical pickup 11 hits the back surface of the disk 3. It is determined that the incident is occurring, and timer 6 is activated.
emits an output signal _S4 , thereby detecting that the disk 3 has been mounted in such a way that the light beam is incident on its back surface. Based on this output signal _S4 , the disk loading mechanism 14 and warning section 15 are driven. Although not shown, by supplying the output signal _S4 from the timer 6 to the voltage generation circuit 8 or the optical pickup 11,
It is also possible to stop each operation.

By the way, if the back surface of the disk 3 mounted on the disk mounting section 2 is a reflective surface, even if the disk 3 is mounted with the front and back surfaces reversed, the focus drawing operation by the focus drawing circuit will not occur. At this time, the optical pickup 11 receives the reflected light beam from the back surface of the disk 3, so that a focus pull-in operation similar to that when the disk 3 is correctly mounted is performed. As a result, the output signal _S3 of the focus discrimination circuit 12 changes from a low level to a high level, the focus control circuit system takes a focus control operation state, and a signal reading state for the disk 3 is entered.
In this case, since the reading surface is not the front surface, a regular reproduction signal cannot be obtained, and a control signal included in the reproduction signal cannot be obtained. Therefore, for example, the rotation control of the disk rotation motor 1 may not be performed, and there is a risk that the disk rotation motor 1 may run out of control.

Therefore, in this example, such an inconvenience is prevented from occurring. Therefore, the output signal S ₃ of the focus discrimination circuit 12 is supplied to one input terminal of the AND gate 16 . At this time, the other input terminal of the AND gate 16 receives a high level command signal.
S ₁ is being supplied, and when the output signal S ₃ changes from low level to high level, the output signal S ₅ from the output terminal of AND gate 16 changes from low level to high level, and the timer 17 is set. is supplied to the end (S). This timer 17 starts measuring time when the output signal _S5 changes from a low level to a high level, and when a preset predetermined time is measured,
The output signal S ₆ is changed from low level to high level and is supplied to one input terminal of AND gate 18 .

On the other hand, at the time when the output signal _S6 from the timer 17 changes to a high level, the focus control operation state is being taken, and the optical pickup 11 is reading the signal from the disk 3. The reproduced signal is supplied to the signal processing circuit 19, where necessary processing is performed. If this reproduced signal comes from the front side of the disc 3, a regular reproduced information signal is obtained as the output of the signal processing circuit 19, but if it comes from the back side, for example, a pseudo signal such as noise etc. It becomes an information signal. The output of the signal processing circuit 19 is then supplied to the information signal discrimination circuit 20. This information signal determination circuit 20 determines whether the supplied output from the signal processing circuit 19 is a regular reproduction information signal or not.
The output signal _S7 of the information signal discrimination circuit 20 is, for example,
If the reproduction information signal is a regular reproduction information signal, it takes a low level, and if it is not a regular reproduction information signal, it takes a high level.

Therefore, disk 3 is not installed correctly,
When the back side of the disk 3 is read by the optical pickup 11, the information signal discrimination circuit 20
The output signal S ₇ of is at a high level and is supplied to the other input terminal of the AND gate 18 .
Then, at one input terminal of the AND gate 18,
By supplying the output signal S ₆ of the timer 17 which has changed from a low level to a high level, a high level output signal S ₈ is obtained at the output terminal of the AND gate 18 .

Here, after the predetermined time of the timer 17 is set, after the signal is read from the disk 3, the signal processing circuit 19 starts to operate normally, and the information signal discriminating circuit 20 detects the signal from the signal processing circuit 9. The time must be set to a time longer than the time at which it is possible to correctly determine whether or not the signal is a regular reproduced signal.

In this way, when the disk 3 whose back surface is a reflective surface is transferred to the disk mounting section 2 with its front and back surfaces reversed, a high level output signal _S8 is obtained from the AND gate 18, and thereby , it is detected that the disk 3 is mounted so that the light beam is incident on the back surface thereof. The high level output signal _S8 obtained at the output terminal of the AND gate 18 is supplied to the disk loading mechanism 14 and the warning section 15, and the disk loading mechanism 14 receives the high level output signal _S8 . Upon receiving the high level output signal _S8 , the warning section 15 takes a warning action such as displaying a warning display or emitting a warning sound. conduct.

In the above example, the timer 6 is used, but instead of providing this timer 6, the number of repetitions of the focus pull-in operation by the focus pull-in circuit is counted, and the counting result is used as the normal focus pull-in operation. When a predetermined number of times exceeds the number of repetitions in the state, a counter that generates an output signal is used, and the output signal is sent to the disk loading mechanism 14 and the warning section 15 instead of the output signal _S4 from the timer 6. It may also be supplied. In this case, for example, the number of focus pull-in operations is counted by counting a predetermined change in the focus pull-in voltage e from the voltage generating circuit 8. Then, depending on whether the number of repetitions of the focus pull-in operation does not exceed a predetermined number of times, it is determined whether the focus pull-in operation is completed and the focus control circuit enters the focus control operation state. be.

FIG. 2 shows an information signal discrimination circuit 2 used in an example of the optical disc playback device according to the present invention described above.
An example of 0 is shown.

In this example, a terminal 21 connected to the output end of the signal processing circuit 19 is connected to a DC blocking circuit 22, and a clamp circuit 23, a level detection circuit 24, and a level comparison circuit 25 are connected in series to the output side of the DC blocking circuit 22. A determination output terminal 26 is derived from the comparison circuit 25.

In this example, when a regular reproduction information signal is obtained from the signal processing circuit 19, that is, when the terminal 21
For example, when a reproduction information signal Sa having a predetermined negative DC level and an amplitude a is supplied as shown in FIG. 3A, this reproduction information signal Sa is supplied to the DC blocking circuit 22. is supplied, and the DC level is brought to zero, as shown in FIG. 3B. The signal Sa whose DC level is set to zero is supplied to the clamp circuit 23. The clamp circuit 23 clamps the input signal to a certain DC level, for example, a negative voltage level close to zero -Vc, and the low level side is connected to -Vc at its output terminal as shown in FIG. 3C. A signal Sa clamped to is obtained and is supplied to the level detection circuit 24. Specifically, the level detection circuit 24 includes a low-pass filter,
Alternatively, it may be formed of an integrating circuit, and the DC output v _p at the average level or peak level of the signal Sa clamped to -Vc as shown in Figure 3D can be obtained at the output terminal. It will be done. This DC output v _p is one input terminal of the level comparison circuit 25,
For example, it is supplied to the positive input terminal and compared with a reference voltage from a comparison reference voltage supply terminal 27 connected to the other input terminal, for example, the negative input terminal.

On the other hand, when the normal reproduction information signal cannot be obtained from the signal processing circuit 19, that is, when the back side of the disc 3 is read by the optical pickup 11, the terminal 21 receives the signal as shown in FIG. 4A. A spurious signal Sa' appears whose amplitude is significantly smaller than the amplitude a of the reproduced information signal Sa. The DC level of this pseudo signal Sa' is set to zero in the DC stop circuit 22 as shown in FIG. Clamped to level -Vc.
This pseudo signal Sa' clamped to -Vc is supplied to the level detection circuit 24, and the average value of the pseudo signal Sa' clamped to -Vc is output at the output terminal as shown in FIG. 4D. A level or peak level DC output v _p ' is obtained and supplied to one input terminal of the level comparison circuit 25. In this case, since the amplitude of the pseudo signal Sa' is significantly smaller than the amplitude of the signal Sa, the DC output v _p ' is significantly lower than the DC output v _p described above.

The reference voltage supplied from the comparison reference voltage supply terminal 27 to the other input terminal of the level comparison circuit 25 is a DC output v _p as shown in FIGS. 3D and 4D.
and v _{p ′} . and,
The output signal S ₇ of the level comparison circuit 25 is connected to one input terminal as a DC output v _p higher than the reference voltage V _b (v _p > V _b ).
becomes low level when V b is supplied, and the reference voltage V _b
It is assumed that the high level occurs when a lower DC output v _p ′ (v _p ′<V _b ) is supplied. This output signal S ₇
is supplied from the discrimination output terminal 26 to the other input terminal of the AND gate 18.

In addition, as another example of the information signal discrimination circuit 20,
It is possible to use a circuit that detects whether the signal read from the disk 3 is a signal that has been recorded using a predetermined recording method. In that case, for example, in the case of a digital audio disk commonly called a compact disk, 1
Since it is standardized that a frame signal consists of 588 channel bits, by providing a circuit to detect whether or not 588 bits are obtained within one frame, it is possible to ensure that the signal is a legitimate reproduction information signal. It is possible to determine whether or not.

Effects of the Invention As described above, the optical disc playback device according to the present invention can be used in cases where the operator mistakenly attaches the disc with the front and back sides reversed and performs a playback operation. If the disk is not installed correctly, it can be automatically detected whether the back side of the disk is a non-reflective surface or a reflective surface, and subsequent processing can be carried out as soon as possible, for example. It is extremely convenient for operation because it performs operations such as returning the disk to the unloading state or issuing a warning to notify the operator. In addition, in the optical disc playback device according to the present invention, it is possible to prevent unnecessary repetition of the focus pull-in operation and to prevent the disc rotation motor from continuing to be driven in a state where the rotation control is not performed correctly. This eliminates the cause of this problem and prevents wasteful energy consumption.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram showing essential parts of an example of an optical disc playback device according to the present invention, FIG. 2 is a block connection diagram showing an example of an information signal discrimination circuit used in the example of FIG. 1, and FIG. 4 and 4 are waveform diagrams used to explain the operation of the example shown in FIG. 2. In the figure, 5 is a command signal generation circuit, 6 and 17 are timers, 7 is a switching control circuit, 8 is a voltage generation circuit,
9 is a focus drive circuit, 10 is a focus adjustment means, 11 is an optical pickup, 12 is a focus discrimination circuit, 14 is a disk loading mechanism, 15 is a warning section, 19 is a signal processing circuit, and 20 is an information signal discrimination circuit. .

Claims (1)

[Scope of Claims] 1. A focus pull-in circuit capable of repeatedly performing a focus pull-in operation for pulling a focus control circuit system into a control operation state for a light beam incident on the disk, and from the first start of the focus pull-in operation by the focus pull-in circuit. Based on the fact that a signal indicating the end of the focus pull-in operation is not obtained from the focus pull-in circuit before a predetermined time elapses or before the number of focus pull-in operations reaches a predetermined number, the disk a first determination unit that determines whether the disc is mounted in such a way that the light beam is incident on its non-information reading surface; and a first determination unit that determines whether or not a regular reproduction signal is obtained from the disc a discriminating circuit that generates a discriminating signal that takes a specific state when the reproduced signal is not obtained, and a signal indicating the end of the focus pull-in operation from the focus pull-in circuit is obtained;
A second method for determining, based on the determination signal being in the specific state after a predetermined time has elapsed, that the disk is mounted in such a way that the light beam is made incident on the non-information reading surface thereof. An optical disc playback device comprising: a determination unit; and an optical disc playback device.