JPH06119648A - Defocus determination method for optical disk device - Google Patents

Abstract

(57) [Abstract] [Purpose] In an out-of-focus determination method of an optical disk device, when an information reproduction signal is lost, it is determined whether or not out-of-focus. [Configuration] If the information reproduction signal 10 is lost, the output signal of the mono-multivibrator 37 becomes low level, and the microcomputer 6 outputs the offset data 19 to the control circuit 18. The offset data 19 is the focus error signal 11
Is added to the data obtained by A / D conversion in the control circuit 18. If the focus servo is off, the focus error signal 11 is almost zero, and the offset data 1 is almost zero.
The value of 9 continues to be accumulated in the low frequency range data 20 which is the low frequency (low frequency) component of the focus drive signal 13. The microcomputer 6 compares the low-frequency term data 20 with a predetermined value, and when the low-frequency term data 20 exceeds a predetermined value (if the predetermined value is negative, the low-frequency term data 20 becomes smaller than the predetermined value), defocus is detected. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an out-of-focus discriminating method for an optical disk device.

[0002]

2. Description of the Related Art A conventional defocus determination method for an optical disk device will be described below.

FIG. 12 is a block diagram showing a method of discriminating out-of-focus of a conventional optical disk device. In FIG. 12, reference numeral 1 is an optical disk which is an information recording medium, and 2 is an optical disk by irradiating the optical disk 1 with light and generating and outputting an information reproduction signal 10 and a focus error signal 11 from the reflected light from the optical disk 1 and a focus drive current 14. An optical device having an objective lens 36 driven in a direction perpendicular to one surface, 3 is a high-pass filter having the information reproduction signal 10 as an input, 4 is an envelope detecting means having an output of the high-pass filter 3 as an input, and 5 is an envelope detecting means. Four
Of the output signal 29 of the comparator 5, 37 is a mono-multivibrator that receives the output signal 30 of the comparator 5, 12 is a microcomputer that receives the output signal of the mono-multivibrator 37, and 7 is a focus error signal 11. A control filter 8 which outputs a filtered signal as a focus drive signal 13 as an input, and a control filter 7
Is a driver for supplying a focus drive current 14 to the optical device 2 by inputting the focus drive signal 13 which is the output of the above, and 9 is a motor for rotating the optical disc 1.

The operation of the out-of-focus discriminating method of the optical disc device constructed as described above will be described below.

The focus error signal 11 is shown in FIG.
When the defocus is zero (the focus of the objective lens 36 is on the surface of the optical disk 1) as shown in (1), it becomes zero, and as the focus deviates, it has a positive or negative peak depending on the deviation direction and converges near zero. The polarities are set so that if the distance is shorter than the distance between the objective lens 36 in the optical device 2 and the optical disc 1 when the defocus is zero, it has a negative peak, and if it is longer, it has a positive peak. . Control filter 7
Takes the focus error signal 11 as input, and performs low-frequency compensation (increases gain at low frequency) and phase compensation (advances phase to improve phase delay near gain intersection frequency)
The servo loop is configured to set the focus error signal 11 to zero by setting the output of the control filter 7 to the focus drive signal 13, and the focus of the light emitted from the optical device 2 is always It is controlled so as to be near the surface of the optical disc 1. The information reproduction signal 10 output from the optical device 2 is input to the high pass filter 3 and high frequency components are extracted. Optical device 2 is optical disc 1
The information reproduction signal 10 is the total sum of the amounts of light reflected from the optical disk 1 by irradiating the light. The information reproduction signal 10 is the optical device 2
When the focus of the light emitted from the optical disk is near the surface of the optical disk 1, the level is increased if the focal point (spot) of the light on the surface of the optical disk is between the pits, and if it is on the pit, the level is increased. The level will drop due to such reasons. Also,
As the focus of light deviates from the surface of the optical disc 1, the level difference due to the presence or absence of pits disappears, and the level decreases. When the optical disc 1 is rotated by the motor 9 and the focus servo is applied (the servo loop is operating so that the focus of the light emitted from the optical device 2 is near the surface of the optical disc 1), the spot is tracked due to the eccentricity of the optical disc 1. Since they cross, the information reproduction signal 10 includes a high frequency signal corresponding to the unevenness of the pit. 14
(G) is the output signal of the high pass filter 3 when the focus servo is applied, and extracts the high frequency component of the information reproduction signal 10. The output signal of the high-pass filter 3 is converted into an envelope on the bright level side by the next envelope detecting means 4 as shown in FIG. Further, in the comparing means 5, when the envelope detecting means output signal 29 exceeds the "threshold value", the comparing means output signal 30 of a high level is outputted to the mono-multivibrator 37 as shown in FIGS. . Mono multivibrator 37
Extends the high level time of the comparison means output signal 30 so that the microcomputer 12 can easily monitor it. FIG.
(B) Defocus amount and envelope detection means output signal 2
9 shows the relationship of 9 and (c) is the comparison means output signal 30 corresponding to (b), and when the defocus is zero, the envelope detection means output signal 29 becomes maximum and becomes smaller as the focus shifts. . Envelope detecting means output signal 29
Is above the "threshold value" in the comparing means 5, the above-mentioned operation is performed and a high level signal is output to the mono-multivibrator 37. The microcomputer 12 monitors whether or not the output signal of the mono multivibrator 37 includes a high level section, and if the high level section is included, it is determined that the focus servo is applied.

[0006]

However, in the above conventional configuration, when the information reproduction signal 10 is missing,
There is a problem that it is impossible to determine whether the focus servo is out of position (out of the S-shaped range in FIG. 13A), or whether the focus servo is applied but the optical disc 1 is in a place where there are no irregularities (pits). Had a point.

The present invention solves the above-mentioned conventional problems, and provides a defocus determination method for an optical disk device, which can determine whether or not the focus is defocused even when an information reproduction signal is missing. To aim.

[0008]

In order to achieve this object, an out-of-focus discriminating method for an optical disk apparatus according to the present invention has the following method.

In the first method, an offset is injected into the focus servo loop, and the focus drive signal during the offset injection is compared with a predetermined value to determine whether or not the focus is out of focus.

The second method is to inject an offset into the focus servo loop and compare the level of the focus error signal during the offset injection with a predetermined value to judge whether the focus is out of focus or not.

[0011]

According to the present invention, by the first method described above, when the focus servo is out, the added offset is not suppressed and continues to be accumulated in the focus drive signal.
Since the focus drive signal exceeds a predetermined value (if the predetermined value is a negative value, it becomes smaller than the predetermined value), it is determined that the focus is out of focus.

The present invention also provides the above-mentioned second method.
If the focus servo is out of focus, the level of the focus error signal does not change and does not exceed the predetermined value, so it is determined to be out of focus.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1, 2 and 3 are block diagrams showing a method for determining an out-of-focus state of the optical disk device according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an optical disk which is an information recording medium, and 2 denotes an optical disk 1 which is irradiated with light to generate and output a focus error signal 11 from the reflected light from the optical disk 1, and a focus drive current 14 causes a vertical direction to the surface of the optical disk 1. An optical device having an objective lens 36 driven to
8, a microcomputer 39 receives the focus error signal 11 from the A / D converter 21 as shown in FIG.
After the conversion, the offset data 19 and the addition means 22 add them together, input them to the control filter 41, and output the drive data 38, which is the output value of the control filter 41, to the D / A converter 2.
4, a control circuit for D / A converting, outputting the output of the D / A converter 24 as the focus drive signal 13 and outputting the drive data 38 to the microcomputer 40; and 8 for the focus drive signal 13 which is the output of the control circuit 39. Is a driver that supplies the focus drive current 14 to the optical device 2 by inputting, and 9 is a motor that rotates the optical disc 1. 3 is an internal configuration diagram of the control filter 41. Reference numeral 26 is a low-pass compensation filter that receives the output of the adder 22 and performs low-pass compensation filtering, and 27 is an adder 2.
A phase compensation filter that receives the output of 2 as input and performs a phase compensation filter process, and 28 is an addition unit that adds the output of the low-pass compensation filter 26 and the output of the phase compensation filter 27.
The drive data 38 output from the adding means 28 is D / A.
It is an input to the converter 24.

The operation of the out-of-focus discriminating method of the optical disc apparatus of the present embodiment having the above-described structure will be described below. The focus error signal 11 is converted into 8-bit digital data by the A / D converter 21. The 8-bit digital data is added to the 8-bit negative offset data 19 by the adding means 22 and input to the control filter 41. The offset data 19 has a positive peak value of 8 of the focus error signal 11 so as not to exceed the dynamic range of the focus error signal 11.
The value of 1 / min is set to the value with the polarity reversed. Control filter 41
3 has a configuration as shown in FIG. 3, in which the output of the adding means 22 is low-frequency-compensated (increases gain at low frequency) filter 26 and phase-compensated (phase is improved to improve phase delay near gain intersection frequency). (Advance) Input to the filter 27, the respective filter outputs are added by the adding means 28, and output to the D / A converter 24. The D / A converter 24 outputs the 8-bit drive data 38 output from the adding means 28.
Is D / A converted. Since the output of the D / A converter 24 is the focus drive signal 13, the servo loop is configured so that the output data of the adding means 22 becomes zero. Further, the microcomputer 40 inputs and monitors the drive data 38 which is the output of the control filter 41.
The drive data 38 is expressed by an 8-bit two's complement representation and converted into a decimal number to take a value of -128 to +127. The microcomputer 40 determines that the focus servo is off when the drive data 38 has a value smaller than -63. The predetermined value of −63 is obtained by the drive data 38 when the objective lens 36 follows the size of the maximum surface wobbling of the optical disc 1 (about 2 mm from peak to peak) (focus servo is applied). It is set to -63, which is a sufficiently small value for the possible values.

When the focus servo is applied, defocus occurs by the amount of the offset data 19 (several hundred nm), and the drive data 38 also changes by the same amount (several hundred nm). However, the predetermined value is a sufficiently small value as described above. Therefore, the drive data 38 does not become smaller than the predetermined value of −63, and the microcomputer 40 determines that the focus servo is applied.

Next, a case where the focus servo is deviated due to disturbance (vibration or scratch) will be described.

If the focus servo is off,
Since the focus error signal 11 is outside the S-shaped range as shown in FIG. 13A, the focus error signal 11 is almost zero although it has a slight offset. Therefore, the output of the adding means 22 is dominated by the value of the offset data 19, the negative value is accumulated in the low-pass compensation filter 26, and the output data of the low-pass compensation filter 26 decreases. On the other hand, the output data of the phase compensation filter 27 becomes a value near zero because the output of the adding means 22 hardly changes. Therefore, the drive data 38 decreases.
The microcomputer 40 determines that the focus servo is off when the drive data 38 has a value smaller than -63. The time from when the offset is injected to when it is determined that the focus servo is out of order is distinguished from the drive data 38 when the objective lens 36 follows the maximum surface wobbling of the optical disc 1. Since it needs to be moved more than the amount of surface wobbling, it takes about 100 ms.

Next, the case where the focus servo is applied to a portion of the optical disc 1 where there is no unevenness will be described. The focus servo is applied to a portion of the optical disc 1 where there is no unevenness, for example, when a non-recorded area is entered during access. Even when the focus servo is applied to a portion of the optical disc 1 where there is no unevenness, the microcomputer 40 determines that the focus servo is applied because the drive data 38 does not become smaller than the predetermined value −63 as described above.

As described above, according to this embodiment, an offset is injected into the focus servo loop, and whether the focus is out of focus or not is accurately determined depending on whether the drive data 38 during the offset injection is smaller than −63. be able to.

FIG. 4, FIG. 5 and FIG. 6 are block diagrams showing a method for determining the out-of-focus state of the optical disk device according to the second embodiment of the present invention. In FIG. 4, reference numeral 1 denotes an optical disk which is an information recording medium, and 2 denotes an optical disk by irradiating the optical disk 1 with light and generating and outputting an information reproduction signal 10 and a focus error signal 11 from reflected light from the optical disk 1 and a focus drive current 14. An optical device having an objective lens 36 driven in a direction perpendicular to one surface, 3
Is a high-pass filter to which the information reproduction signal 10 is input, 4
Is an envelope detecting means having the output of the high-pass filter 3 as an input, and 5 is an output signal 29 of the envelope detecting means 4.
Is input, and 37 is the output signal 3 of the comparing means 5.
A mono multivibrator having 0 as an input, and 6 having an output signal of the mono multivibrator 37 and the low-frequency term data 20 as an input and offset data 19 as a control circuit 18
The microcomputer 18 outputs the focus error signal 11 to the offset data 19 which is the output of the microcomputer 6 after A / D conversion by the A / D converter 21 as shown in FIG.
Is added by the addition means 22 and input to the control filter 23,
The drive data 38, which is the output value of the control filter 23, is D / A converted by the D / A converter 24, and the output of the D / A converter 24 is output as the focus drive signal 13, or the low-pass data in the control filter 23 is output. 20 is a control circuit for outputting to the microcomputer 6, 23 is a control filter for filtering low frequency compensation and high frequency compensation, 8 is a control circuit 1
A driver for supplying a focus drive current 14 to the optical device 2 by inputting the focus drive signal 13 which is the output of 8 and a motor 9 for rotating the optical disc 1.
6 is an internal configuration diagram of the control filter 23.
Reference numeral 6 is a low-frequency compensation filter that receives the output of the adding means 22 as input, and performs low-frequency compensation filtering processing, 27 is a phase compensation filter that receives the output of the adding means 22 as input, and performs phase-compensation filtering processing, and 28 is low-pass compensation filter. Drive data 38, which is the output of the adder 28, is the input of the D / A converter 24. The output of the low-pass compensation filter 26 is input to the microcomputer 6 as low-pass term data 20.

The operation of the defocus determination method of the optical disk device of the present embodiment having the above-described structure will be described below. The path from the optical device 2 to the output signal of the mono-multivibrator 37 via the high-pass filter 3 has the same configuration as the conventional example, and the description thereof will be omitted. The microcomputer 6 monitors the output signal of the mono multivibrator 37, and if the output signal of the mono multivibrator 37 becomes high level, it determines that the focus servo is in operation.

First, when the output signal of the mono multivibrator 37 is at a high level, the offset data 19 output from the microcomputer 6 is zero (no offset is added).
Is. The focus error signal 11 is converted into 8-bit digital data by the A / D converter 21. The 8-bit digital data is added to the 6-bit offset data 19 by the adding means 22. In this case, since the offset data 19 is zero, the A / D converter 21 is used.
The output data of the above is directly input to the control filter 23. The structure of the control filter 23 is as shown in FIG. The output of the adder 22 (in this case, the output of the A / D converter 21) is low-frequency-compensated (increases gain at low frequency) filter 26 and phase-compensated (phase is advanced to improve phase delay near gain intersection frequency). ) It is input to the filter 27, the respective filter outputs are added by the addition means 28, and D /
It is output to the A converter 24. D / A converter 2
Reference numeral 4 D / A-converts the 8-bit drive data 38 output from the adding means 28. Since the output of the D / A converter 24 is the focus drive signal 13,
The control circuit 18 has a servo loop configured to make the focus error signal 11 zero, and is controlled so that the focus of the light emitted from the optical device 2 is always near the surface of the optical disc 1.

Next, the case where the focus servo is deviated due to disturbance (vibration or scratch) will be described.

When the focus servo is deviated due to disturbance, the focus error signal 11 is out of the S-shaped range, and the high frequency component of the information reproduction signal 10 corresponding to the pit irregularities cannot be detected, so that the output signal of the mono multivibrator 37 is at a low level. become. The microcomputer 6 outputs the offset data 19 to the control circuit 18 if the output signal of the mono multivibrator 37 is at a low level for a certain time or longer. The size of the offset data 19 is a value obtained by inverting the polarity of a value of ⅛ of the positive peak value of the focus error signal 11 as offset data 19 so as not to exceed the dynamic range of the focus error signal.

The microcomputer 6 inputs and monitors the low frequency term data 20 which is the output of the low frequency compensation filter 26. In the present embodiment, in consideration of the case where the focus error signal 11 has a noise of a high frequency component, out-of-focus detection during offset injection is performed by the low-frequency data 20. When the focus error signal 11 has high-frequency noise, the output value of the phase compensation filter 26 may fluctuate greatly, and the drive data 38 may become smaller than the predetermined value −63. Therefore, out-of-focus detection is performed using the low-frequency data 20 that is not affected by high-frequency noise. The low-pass term data 20 is represented by an 8-bit two's complement expression and is represented by 10
It is converted to a base number and takes a value of -128 to +127. The microcomputer 6 determines that the focus is out of focus when the low frequency data 20 has a value smaller than -63. The operation in which the low-frequency data 20 becomes smaller than −63 is the same as in the first embodiment.

In this way, the microcomputer 6 detects that the low-frequency data 20 becomes smaller than -63 when the focus is out of focus.

Further, if the polarity is determined so that the objective lens 36 in the optical device 2 is driven in the direction away from the optical disc 1 when the output of the control filter 23 is a negative value, the objective lens 36 is surely moved when defocused. Since it is separated from the optical disc 1, the objective lens 36 and the optical disc 1
It also prevents contact.

Next, the case where the focus servo is applied to a portion of the optical disc 1 where there is no unevenness will be described. The focus servo is applied to a portion of the optical disc 1 where there is no unevenness, for example, when a non-recorded area is entered during access. When the focus servo is applied to a portion of the optical disc 1 where there is no unevenness, the high-frequency component of the information reproduction signal 10 corresponding to the unevenness of the pit cannot be detected, and the output signal of the mono multivibrator 37 becomes low level. The microcomputer 6 outputs the offset data 19 to the control circuit 18 if the output signal of the mono-multivibrator 37 is at the low level for a certain period of time or longer, as when the focus servo is deviated due to disturbance (vibration or scratch). Since the focus servo is applied, when the objective lens 36 in the optical device 2 is driven in the direction away from the optical disc 1 by the low-frequency item data 20 in which the added negative offset data 19 is accumulated, the focus error signal 11 is generated. The offset data 19 has the opposite polarity (positive) and changes by the same amount, and becomes a balanced state, and the data input to the control filter 23 becomes the zero center as before the offset data 19 is added. Further, as described in the first embodiment, when the focus servo is applied, the low-pass term data 20 does not become smaller than the predetermined value −63 even if the offset data 19 is injected. The microcomputer 6 inputs and monitors the low-frequency term data 20 which is the output of the low-frequency compensation filter 26. If the low-frequency term data 20 does not become smaller than −63 for a certain period of time, the focus servo is in effect. to decide.
At the same time when it is determined that the focus servo is applied, the offset data 19 is reset to zero. This is because the offset data 19 injected for out-of-focus detection
The focal point of the light emitted from the optical device 2 is the optical disc 1
Defocusing occurs from the surface, and injection of offset data is stopped (set offset data 19 to zero).
By doing so, defocusing is eliminated.

In this way, when the focus servo is applied to a portion of the optical disc 1 where there is no unevenness, the low-frequency data 2 after the lapse of a fixed time after the offset data 19 is injected.
Since 0 does not become smaller than the predetermined value of −63, it is determined that the focus servo is applied.

As described above, according to the present embodiment, as a first effect, the offset is injected into the focus servo loop, and the low-frequency term data 20 which is the low-frequency component of the focus drive signal during the offset injection is -63. By determining whether or not the focus is out of focus depending on whether or not it becomes small, it is possible to accurately determine whether or not the focus is out of focus even if the focus error signal 11 includes noise of a high frequency component.

As a second effect, the information reproduction signal 10
By only injecting an offset into the focus servo loop, the defocus caused by the offset when the information reproduction signal 10 is present is eliminated only when the information reproduction signal 10 exists.

As a third effect, the control filter 23
By determining the polarity so that the objective lens 36 in the optical device 2 is driven in a direction away from the optical disc 1 when the output of is a negative value, the objective lens 36 always comes away from the optical disc 1 when defocused. Therefore, the contact between the objective lens 36 and the optical disk 1 can be prevented.

As a fourth effect, it is judged that the focus servo is applied and at the same time the offset data 1
By returning 9 to zero, defocus due to offset is eliminated.

FIG. 7 and FIG. 8 are block diagrams of a method for determining an out-of-focus state of an optical disk device according to the third embodiment of the present invention. In this figure, the difference from FIGS. 4 and 5 is that the A / D converter output data 31 is provided so as to be input to the microcomputer 15 instead of the low-frequency item data 20.
The operation from the loss of the information reproduction signal 10 to the injection of the offset data 19 by the microcomputer 15 is the same as in the second embodiment. Since the microcomputer 15 detects the focus error signal 11 after a certain time (several ms) has passed after the offset data 19 is injected, the focus error signal 11 is set to A
The A / D converter output data 31 that has been / D converted is input. The focus error signal 11 after the offset data 19 is injected is, as described in the second embodiment,
When the focus is out of focus, the focus error signal 11 is outside the S-shaped range and is substantially zero, and when the focus servo is applied to a portion of the optical disc 1 where there is no unevenness, the focus error signal 11 is opposite to the offset data 19. The polarity (positive) changes by the same amount and the equilibrium state is reached. The time from injection of the offset data 19 to reaching the equilibrium state is several ms because the objective lens 36 is displaced by several hundred nm. Therefore, the focus error signal 11 a few ms after the offset is injected
It is possible to determine whether the focus is lost or not by detecting and determining the level. Specifically, the comparison data value a as shown in FIG. 9D is held inside the microcomputer 15, and the A / D converter output data 31 and the comparison data value a are compared in size to obtain A / A from the comparison data value a. D converter output data 31
Is larger, it is determined that the focus servo is applied, and the A / D converter output data 31 indicates the comparison data value a.
If the following is true, it is determined that the focus servo is off.

As described above, according to the present embodiment, the offset is injected into the focus servo loop, and if the level of the focus error signal during the offset injection is larger than the comparison data value a, it is determined that the focus is applied,
If the comparison data value is equal to or smaller than the comparison data value a, the defocused state can be detected at high speed by determining the defocused state.

FIG. 10 is a diagram showing an out-of-focus determination method for an optical disk device according to the fourth embodiment of the present invention. In this figure, the difference from FIG. 4 is that a position detection signal 3 indicating the position of the optical device 2 in the radial direction of the optical disk 1 is shown.
4, an A / D converter 35 for A / D converting the position detection signal 34 and outputting it to the microcomputer 17, a feed signal 32 for moving the optical device 2 in the radial direction of the optical disc 1, and a feeding means 3
3 is provided.

In this embodiment, the determination of out-of-focus is the same as in the second embodiment, and the explanation is omitted. Optical disc 1
When the focus servo is applied to a place where there is no unevenness, it is determined by the operation of the second embodiment that the focus servo is applied and the operation after the offset injection is stopped is the operation peculiar to the fourth embodiment.

In the fourth embodiment, the position detection signal 34 after the offset injection is stopped is monitored.

The position detection signal 34 is a signal shown in FIG. The level of the position detection signal 34 is the lowest when the position of the optical device 2 is at the innermost circumference of the optical disc 1, and becomes higher as the optical device 2 moves toward the outer circumference of the optical disc 1. In addition, the optical disc 1 has a portion having no unevenness on the inner circumference or the outer circumference as shown in FIG. When the focus servo is applied to a portion of the optical disc 1 where there is no unevenness, whether the optical device 2 is on the outer circumference or the inner circumference can be determined by the level of the position detection signal 34. The microcomputer 17 monitors the data obtained by converting the position detection signal 34 by the A / D converter 35, and compares the comparison data value b with the microcomputer 1.
7, and compares the output data of the A / D converter 35 with the comparison data value b. Comparison data value b
If the output data of the A / D converter 35 is larger, it is determined that the optical device 2 is located on the outer circumference of the optical disc 1, and the feed signal 32 is set to the inner circumference feed (for example, positive voltage). When the feed signal 32 is set to the inner circumference feed, the feeding means 33 moves the optical device 2 to the inner circumference. While the optical device 2 is moving in the inner peripheral direction, if the focus of the light of the optical device 2 is on the uneven portion of the optical disc 1, a high frequency component appears in the information reproduction signal 10 and the operation described in the conventional example is performed. The output signal of the multivibrator 37 becomes high level. When the output signal of the mono multivibrator 37 becomes high level, the microcomputer 17 sets the feed signal 32 to zero and stops the movement of the optical device 2. If the output data of the A / D converter 35 is less than or equal to the comparison data value b, it is determined that the optical device 2 is located at the inner circumference of the optical disc 1, and the feed signal 32 is set to the outer circumference feed (for example, negative voltage). To do. When the feed signal 32 is set to the outer circumference feed, the feeding means 33 moves the optical device 2 to the outer circumference. While the optical device 2 is moving in the outer peripheral direction, if the focus of the light of the optical device 2 is on the uneven portion of the optical disc 1, a high frequency component appears in the information reproduction signal 10 and the operation explained in the conventional example is performed. The output of 5 becomes high level. When the output of the comparison means 5 becomes high level, the microcomputer 17 sets the feed signal 32 to zero and stops the movement of the optical device 2.

As described above, in the present embodiment, when the focus servo is applied to a portion of the optical disk 1 where there is no unevenness, the optical device 2 is moved in the radial direction of the optical disk 1 to move the focus servo to the uneven area of the optical disk 1. Can be applied.

[0042]

As described above, according to the present invention, it is possible to judge whether the focus is out of focus or not by injecting an offset into the focus servo loop and comparing the focus drive signal during the offset injection with a predetermined value.

By injecting an offset into the focus servo loop and comparing the level of the focus error signal during the offset injection with a predetermined value, it is possible to quickly determine whether or not the focus is out of focus.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical disk device according to a first embodiment of the present invention.

2 is a block diagram showing an internal configuration of a control circuit 39 in FIG.

3 is a block diagram showing an internal configuration of a control filter 41 in FIG.

FIG. 4 is a block diagram showing a configuration of an optical disc device according to a second embodiment of the present invention.

5 is a block diagram showing an internal configuration of a control circuit 18 in FIG.

6 is a block diagram showing an internal configuration of a control filter 23 in FIG.

FIG. 7 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the present invention.

8 is a block diagram showing an internal configuration of a control circuit 16 in FIG.

FIG. 9 is a waveform diagram of a focus error signal for explaining the operation of the third embodiment.

FIG. 10 is a block diagram showing a configuration of an optical disc device according to a fourth embodiment of the present invention.

FIG. 11 is an explanatory diagram for explaining the operation of the fourth embodiment.

FIG. 12 is a block diagram showing the configuration of a conventional optical disc device.

FIG. 13 is a characteristic diagram showing the relationship between the amount of defocus and each signal in the conventional example.

FIG. 14 is a waveform diagram showing a relationship between signals in the conventional example.

[Explanation of symbols]

 1 Optical Disc 2 Optical Device 3 High Pass Filter 4 Envelope Detecting Means 5 Comparing Means 6 Microcomputer 8 Driver 9 Motor 18 Control Circuit 37 Mono Multivibrator

Claims (7)

[Claims] 1. A method for discriminating defocus of an optical disk apparatus, which comprises injecting an offset into a focus servo loop and comparing a focus drive signal during the offset injection with a predetermined value to judge whether or not the defocus state exists. . 2. An optical disk apparatus, wherein an offset is injected into a focus servo loop, and a low frequency component of a focus drive signal is compared with a predetermined value during the offset injection to determine whether or not the focus is out of focus. Defocus determination method. 3. An out-of-focus state of an optical disk apparatus, wherein an offset is injected into a focus servo loop, and a level of a focus error signal during the offset injection is compared with a predetermined value to determine whether or not the focus is out of focus. How to determine. 4. The method of discriminating out-of-focus of an optical disk apparatus according to claim 1, wherein an offset is injected into the focus servo loop when it is detected that the information reproduction signal is lost. 5. The optical disc device according to claim 1, wherein the polarity of the offset is set in a direction in which the objective lens in the optical device is separated from the optical disc when the focus servo loop is open. How to determine. 6. The method of discriminating out-of-focus of an optical disk device according to claim 1, wherein offset injection is stopped after it is confirmed that the lens is in focus. 7. The defocus determination method for an optical disk device according to claim 4, wherein the optical device is moved in the radial direction of the optical disk after it is confirmed that the optical disk is in focus.