JP2000260025A - Pre-pit detecting device and optical information recording / reproducing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate erroneous detection of a pre-pit signal. SOLUTION: An amplitude detection circuit 23 detects an amplitude of a noise component including an information signal with respect to a reproduction signal (push-pull signal) of an optical disk including a pre-pit signal. The binarization circuit 26 binarizes the reproduction signal of the optical disk using a predetermined slice level and detects a pre-pit signal.
The slice level setting circuit 25 sets a slice level used in the binarization circuit 26 based on the amplitude detected by the amplitude detection circuit 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-pit detecting device and an optical information recording / reproducing device.

[0002]

2. Description of the Related Art DVD-R employs a format in which tracks are wobbled so that the wobble signal frequency becomes constant when CLV rotation control is performed in order to accurately detect the linear velocity at each radial position in advance during manufacturing. ing. Therefore, the optical information recording / reproducing apparatus detects the wobble signal to control the rotation of the optical disk or generate a recording clock. The recording medium also needs address information so that the recording position can be specified, but a DVD-R has a guide track (for example, land) between two information recording tracks (for example, groove). Pre-pits corresponding to the address information are formed. Both the pre-pit and the wobble can be obtained from the push-pull signal. The wobble signal is a signal having a relatively small amplitude with a fixed period, and the pre-pit signal is a signal having a relatively large amplitude that is generated intermittently.

[0003]

However, such a DVD-R format has the following problems.

First, there is a problem that an information signal leaks into a push-pull signal. The push-pull signal is obtained by dividing the light receiving element by a dividing line along the information recording track and obtaining from the left and right difference signals. Normally, only the low frequency component is used for track following control. However, high-frequency components are required to detect pre-pits, and high-frequency noise components, which do not cause a problem in normal track following control because they are removed by a filter or the like, cannot be separated. This noise includes not only optical and circuit noises but also information signal components when tracking an already recorded area of the optical disk. The information signal obtained from the mark / space existing on the information recording track in the already recorded area is incident on the left and right light receiving elements at the same level in a steady state, so that it is canceled out when calculating the difference and leaks into the push-pull signal. There are few things. However, if a tilt or the like occurs on the optical disc and the light spot on the light receiving element becomes asymmetrical at the dividing line, leakage and congestion will occur. The pre-pit signal has a relatively large amplitude, but since the pre-pit signal and the information signal have almost the same frequency band, the two signals cannot be completely separated by a filter or the like.

In Japanese Patent Application Laid-Open No. 10-320781, a signal is amplified at a timing when a prepit may exist, and attenuated otherwise, and a leakage information signal or noise generated at a timing when there is no possibility of a prepit is used as a prepit. False detection is suppressed. The digitization (binarization) of the prepit is performed at a slice level obtained by adding the voltage V1 to the wobble signal. However, not only the pre-pits but also the leaked reproduction signal and noise components are amplified at the timing when the pre-pits may be present, so that there are many erroneous detections at the slice level only following the wobble signal level.

The second problem is the generation of a recording clock for determining the recording position control. Normally, recording is performed using a fixed frequency clock or a clock obtained by multiplying a wobble signal. However, in the former case, the recording position cannot be controlled below an extremely large optical disc rotation fluctuation component caused by a mechanical limit. On the other hand, the latter can be controlled a little better, but the wobble signal fluctuates in amplitude and phase due to crosstalk from an adjacent track, so that the recording clock becomes faster or slower due to the wobble phase fluctuation. For this reason, the recording clock generated from the wobble signal has reached the limit of the recording position accuracy.

Japanese Patent Application Laid-Open No. 10-293926 discloses that a recording clock is generated by using not only a wobble affected by crosstalk but also a prepit signal indicating a position on an optical disk without being affected by crosstalk. Has been proposed. This makes it possible to correct the fluctuation due to the wobble crosstalk and to increase the recording position accuracy as compared with the related art. However, strictly speaking, the pre-pit signal of the above detection method is digitized at the slice level to detect the position of the pre-pit, so that when the amplitude of the pre-pit signal changes due to the influence of marks / spaces in the recorded area, the slice level is changed. Differences in crossing times appear, which adversely affects clock stability.

As described above, in the actual device, various fluctuations such as tilt occur, and even in such a situation, in order to prevent erroneous address detection, prepits can be stably detected from the push-pull signal in which the information signal component is leaked. In addition to the need for a circuit capable of performing such a control, a precise pre-pit position detection circuit that takes into account fluctuations in the pre-pit signal amplitude is required in order to control a precise recording position (recording clock) using the pre-pit signal.

An object of the present invention is to eliminate erroneous detection of a pre-pit signal.

Another object of the present invention is to accurately detect a pre-pit position.

[0011]

According to a first aspect of the present invention, there is provided a guide for guiding a light beam to an information recording track and a prepit on which address information is recorded and which guides a light beam to the information recording track. In a pre-pit detection device that obtains a pre-pit signal from the pre-pit when recording or reproducing information on an optical disc on which tracks are provided and on which information can be recorded, a reproduction signal of the optical disc including the pre-pit signal is provided. An amplitude detection circuit that detects an amplitude of a noise component including an information signal; a binarization circuit that binarizes the reproduction signal using a predetermined slice level to detect the pre-pit signal; And a slice level setting circuit for setting a slice level.

Therefore, it is possible to set an optimum slice level in accordance with the level of a noise component including an information signal, which differs depending on the conditions of the optical system and the optical disk, and it is possible to eliminate erroneous detection of a prepit signal.

According to a second aspect of the present invention, in the pre-pit detection apparatus according to the first aspect, the slice level setting circuit prepares a plurality of different slice levels and prepares the plurality of slices based on the amplitude. The slice level is set by selecting one of the levels.

Therefore, the level of the noise component which can be predicted can be quickly switched to a preset slice level, and the required accuracy of the amplitude detection circuit can be suppressed low, so that the cost of the apparatus can be reduced. it can.

According to a third aspect of the present invention, there is provided an information recording track provided with a guide track on which a prepit on which address information is recorded and which guides a light beam to the information recording track is provided. In a pre-pit detection device for obtaining a pre-pit signal from the pre-pit when recording or reproducing information on or from an optical disc capable of recording, a peak detection circuit for detecting a peak position of the pre-pit signal is provided. Is a pre-pit detection device.

Therefore, since the peak position of the pre-pit signal is detected, it is possible to accurately detect the pre-pit position regardless of the amplitude of the pre-pit signal which varies depending on the conditions of the optical system and the optical disk.

According to a fourth aspect of the present invention, in the pre-pit detecting apparatus according to the third aspect, the peak detecting circuit differentiates a reproduction signal of the optical disc including the pre-pit signal, and a differential circuit of the differential circuit. A zero-cross detection circuit for detecting a zero-cross point of the output.

Therefore, since the peak detection circuit can be constituted by the differentiating circuit and the zero-cross detection circuit, the pre-pit position can be detected at low cost.

According to a fifth aspect of the present invention, in the pre-pit detecting apparatus according to the fourth aspect, a gate generation circuit for binarizing the reproduction signal at a certain slice level, and the gate generation circuit based on an output of the gate generation circuit. And a mask circuit for inhibiting the output of the zero-cross detection circuit.

Therefore, noise components detected at timings other than the pre-pit signal can be removed.
In addition, an inexpensive and flexible logic circuit can be used as the mask circuit, and further functional improvement can be easily performed.

According to a sixth aspect of the present invention, in the pre-pit detecting device according to the fourth aspect, a gate generation circuit for binarizing the reproduction signal at a certain slice level, and the gate generation circuit according to an output of the gate generation circuit And a switch circuit for turning on / off an input to the differentiating circuit or the zero-cross detecting circuit.

Therefore, all analog circuits
Noise components detected at a timing other than the pre-pit signal can be removed.

According to a seventh aspect of the present invention, in the pre-pit detecting device according to the fifth or sixth aspect, the pre-pit detecting device according to the first or second aspect is provided as the gate generation circuit. .

Therefore, it is possible to stably detect the pre-pits in various situations and to remove noise components detected at timings other than the pre-pit signal.

According to an eighth aspect of the present invention, in the pre-pit detection device according to any one of the fifth to seventh aspects, the gate generation circuit includes a delay circuit for delaying its output by a predetermined amount. It is characterized by.

Therefore, a gate signal corrected for a circuit delay, which is generated depending on the circuit configuration, can be generated, so that an accurate pre-pit position can be detected, and the degree of freedom in circuit design increases.

According to a ninth aspect of the present invention, in the pre-pit detecting apparatus according to any one of the fifth to eighth aspects, the timing at which the light amount of the light beam fluctuates within a predetermined time during the recording of the information is determined. A recording mask circuit for outputting a signal for inhibiting the output of the pre-pit signal is provided.

Therefore, it is possible to prevent erroneous detection of the pre-pit signal caused by the fluctuation of the light amount of the light beam.

According to a tenth aspect of the present invention, there is provided an optical system for converging the light beam on the optical disk and condensing the reflected light on a light receiving element, and recording information on the optical disk from an output signal of the light receiving element. And a reproducing circuit for detecting the position information of the light beam on the optical disk from the output information, and controlling the irradiation position of the light beam on the optical disk through a predetermined mechanism based on the position information. A servo circuit, and the pre-pit detection device according to any one of claims 1 to 9, wherein the pre-pit detection device detects address information recorded on the optical disc or generates a recording clock. An optical information recording / reproducing apparatus characterized by the following.

Therefore, the same operation and effect as those of the pre-pit detecting device according to any one of the first to ninth aspects can be obtained.

[0031]

[First Embodiment of the Invention] FIG. 1 is a block diagram of an optical system of an optical disk device according to a first embodiment of the present invention. Light emitted from the light source 1 driven by the laser driver 11 is focused on the recording surface 7 on the optical disk 6 by the coupling lens 2, the beam splitter 3, the quarter-wave plate 4, and the objective lens 5. The light reflected on the recording surface 7 returns to the above-mentioned optical system again, passes through the beam splitter 3, is condensed on the light receiving element 9 by the condensing lens 8, and is converted into an electric signal. The output of the light receiving element 9 is converted from a current into a voltage by the I / V amplifier 10 and various calculations are performed, but the calculation may be performed without changing the current.

Usually, the light receiving element 9 and the I / V amplifier 10 are divided into a plurality of parts, and a focus error signal indicating the distance between the recording surface 7 and the focal point of the light spot, a track error signal between the track on the recording surface 7 and the light spot. Calculations such as a track error signal indicating a position and an RF signal for detecting information recorded on the recording surface 7 are performed. In FIG. 1, the focus error signal and the track error signal are calculated in the servo circuit 13, and the light spot is moved to the target position by driving the mechanism system 14 from the position information. The information on the recording surface 7 of the optical disc is calculated into an RF signal in a reproducing circuit 12 and sent to a signal processing circuit (not shown) at a subsequent stage. The detection method of the wobble signal and the pre-pit signal used in the present embodiment differs depending on the division shape of the light receiving element 9, but the simplest example is obtained from the difference between the left and right of the light receiving element division line along the track of the optical disk 6. Since it is obtained from the push-pull signal (one of the track error signals), the following description will be made on the premise that the pre-pit detection circuit 15 operates based on the push-pull signal output from the servo circuit 13.

The recording surface 7 on the optical disk 6 has information recording tracks (for example, grooves) 16 as shown in FIG.
And a guide track (for example, a land) 17 for guiding a light beam to the information recording track 16 is spirally carved, and the guide track 17 contains address information in the form of a groove tear or a pit. Pre-pits 18 are formed. The track is wobbled in a certain cycle, and its detection signal is used as rotation information and the like. However, since the wobbling cycle is very long compared to the length of the pre-pit, the track is shown in a straight line in FIG. .

FIG. 3 shows an actual push-pull signal including a wobble signal, a pre-pit signal and a noise component. In the unrecorded area of the optical disc 6 (the right figure in FIG. 3A), there is no large noise component in the wobble signal detected at a constant period, and the amplitude of the pre-pit signal itself is stable. on the other hand,
In the recorded area of the optical disc 6 (the left diagram in FIG. 3A), a large noise component is superimposed on the wobble signal, and the amplitude fluctuation (dotted line) of the pre-pit signal is large. Although an enlarged view of this is also shown (FIG. 3B), most of the noise is information signal components recorded on the optical disk 6, and since this frequency band is almost the same as the pre-pit signal, a filter or the like is used. Can not be separated. As shown in FIG. 3A, an appropriate slice level is different between an unrecorded area and a recorded area.

FIG. 4 is a block diagram of the pre-pit detection circuit 15. As shown in FIG. 4, since the push-pull signal has a low-frequency undulation generated in a servo state or the like, the pre-pit detection circuit 15 uses a high-pass filter (HPF) having a cutoff frequency (fc) of about several kHz. Remove at 21. Of course, LP with a high cutoff frequency fc is used to remove noise existing in the frequency band higher than the pre-pit signal.
F (low-pass filter) or the like may be inserted. Hereinafter, this signal is referred to as a pre-pit source signal. The pre-pit source signal includes a wobble signal, a pre-pit signal, and a noise component. This signal further has an HPF2 having a cutoff frequency fc of about several hundred kHz to remove a wobble signal component.
2 and input to the amplitude detection circuit 23 to detect the amplitude of the noise component including the information signal component. The amplitude detection circuit 23 may be constituted by an absolute value circuit using a full-wave rectification circuit or a half-wave rectification circuit, but may be a peak / bottom detection circuit or the like. The output of the amplitude detection circuit 23 is averaged by the integration circuit 24 at the subsequent stage because there are a pre-pit signal having a large amplitude, other sudden noise, and output fluctuation of the rectification circuit. The slice level is changed in the subsequent slice level setting circuit 25 by the average level.
As the slice level, a DC-like voltage level may be merely changed according to the noise component amplitude.
It is more preferable to use a wobble signal component of the pre-pit source signal as shown by a dotted line and to add a DC voltage that varies according to the noise component amplitude to the signal.
Further, the gain of the wobble signal component detected from the pre-pit source signal may be changed according to the information signal amplitude. The appropriate slice level shown in FIG.
This is a signal that changes both the DC voltage. The pre-pit source signal is binarized by the binarization circuit 26 at the slice level obtained in this manner, and is converted into a pre-pit signal.

Therefore, it is possible to set an optimum slice level in accordance with the level of the noise component including the information signal, which varies depending on the conditions of the optical system and the optical disk 6 shown in FIG. Can be eliminated.

Although not shown, the optical disk apparatus includes a decoder for a pre-pit signal, which is address information on the optical disk 6 output from the pre-pit detection circuit 15, and a circuit for generating a recording clock generated from the pre-pit signal. I have. Details of the recording clock generation circuit are disclosed in Japanese Patent Application Laid-Open No. 10-293926.

[Second Embodiment] The second embodiment of the present invention is different from the first embodiment in that the slice level setting circuit 25 has a circuit configuration as shown in the block diagram of FIG. At one point. Other technical contents are the same as those of the first embodiment of the invention, and the same reference numerals as those of the first embodiment of the invention are used, and illustration and detailed description are omitted.

As shown in FIG. 5, the slice level setting circuit 25 inputs the pre-pit source signal to an LPF (low-pass filter) 31 having a cutoff frequency fc of several hundred kHz to extract a wobble signal. Of course, a BPF (bandpass filter) may be used. The wobble signal is input to a plurality of preset amplifiers 32 and 33, and is changed to a predetermined gain. These outputs are respectively provided with a predetermined DC voltage output from the constant voltage sources 34 and 35 and the adder 3.
6 and 37, and a plurality of slice levels are prepared. The outputs of the integration circuit 24 representing the amplitude of the noise component in the reproduction signal of the optical disk 6 are used as adders 36 and 3
7 selects one of the slice levels output.

Therefore, it is possible to quickly switch to a preset slice level for a predictable noise component level (for example, when tracking to an unrecorded area or an already recorded area of the optical disc 6), and Since the required accuracy of the detection circuit 23 can be kept low, the cost of the device can be reduced.

Third Embodiment The third embodiment of the present invention is different from the first embodiment in that the pre-pit detection circuit 15 is different as described later. Other technical contents are the same as those of the first embodiment of the invention, and the same reference numerals as those of the first embodiment of the invention are used, and illustration and detailed description are omitted.

As shown in FIG. 6A, the pre-pits 18 formed on the guide tracks 17 on the optical disk 6 are not deformed, but are detected by the recording marks / spaces arranged around them. The amplitude of the pre-pit source signal changes. As shown in FIG. 6B, taking a large pre-pit signal having a large amplitude and a small pre-pit signal having a small amplitude as an example, when binarization is performed at a certain slice level, both binarized signals are used. Causes an error at the time of binarization. Both are shifted from the actual pre-pit position, but the shift is different. The binarization based on the slice level can be performed with a pre-pit 1 which can have a rough position accuracy.
Although there is no problem when using it to judge the presence or absence of 8, this deviation cannot be ignored when it is desired to detect an accurate pre-pit position in order to improve the recording position accuracy. Therefore, a prepit peak position signal that accurately indicates the center position of the prepit 18 is required. Therefore, when the peak detection of the pre-pit is performed using a circuit described later, even if the amplitude of the pre-pit source signal changes as shown in FIG.
The position of the upper pre-pit can be accurately detected.

FIG. 7 is a block diagram showing a circuit configuration of a pre-pit detection circuit (peak detection circuit) 15 according to the third embodiment of the present invention. As shown in FIG. 7, the low-frequency swell component included in the push-pull signal is
To remove. Since the characteristics of the HPF 41 can remove a wobble signal, several hundred kHz is desirable. Of course, an LPF with a high cutoff frequency fc or the like may be inserted in order to remove noise existing in a frequency band higher than the pre-pit signal. Since this signal basically has a mountain-shaped waveform like the push-pull signal shown in FIG. 8, it can be converted by the differentiating circuit 42 into a waveform in which the peak crosses the zero point (differential circuit output). The zero cross point is binarized (zero cross detection signal) by a zero cross detection circuit 43 constituted by a binarization circuit having a hysteresis characteristic, so that a prepit signal indicating the peak position of the prepit 18 is obtained.

As described above, since the peak position of the pre-pit signal is detected, it is possible to accurately detect the pre-pit position regardless of the amplitude of the pre-pit signal which varies depending on the conditions of the optical system and the optical disk 6.

The peak detecting circuit 15 is replaced with a differentiating circuit 42.
And the zero-cross detection circuit 43, the pre-pit position can be detected at low cost.

[Fourth Embodiment] The fourth embodiment of the present invention is different from the third embodiment of the present invention in that a prepit detecting circuit 15 includes a mask circuit 44 as shown in FIG.
And a gate generation circuit 45. Other technical contents are the same as those of the third embodiment of the present invention, and the same reference numerals as those of the third embodiment of the present invention are used, and illustration and detailed description are omitted.

As shown in FIG. 9, the push-pull signal outputted from the HPF 41 has a high-frequency noise component. Also in FIG. 8, the signal is represented by a small mountain-shaped signal with a dotted line,
The differentiating circuit 42 and the zero-crossing detecting circuit 43 also react to this noise component, and are output as pre-pit signals of erroneous detection.

In order to prevent this, the gate generation circuit 45 generates a gate signal which permits the output of the zero-cross detection circuit 43 at the timing when the pre-pits 18 exist and prohibits the output at the timing when the pre-pits 18 cannot exist. At 44, the output of the zero cross detection circuit 43 is masked. When the pre-pit signal and the information signal are synchronized, the gate generation circuit 45 outputs the “reproduction signal” to the R signal.
Although it is possible to generate a gate signal by binarizing an RF signal and detecting a specific pattern by considering it as an F signal (not shown), generally, a push-pull signal is binarized at a certain slice level and used. Is good. In particular, a signal obtained by digitizing the pre-pit signal itself at a slice level that can be binarized has the highest mask efficiency and can cut noise components. However, since a high-speed circuit is required, the efficiency is reduced as an alternative, but it is also possible to mask with a binary digital signal of a wobble signal usable for a format in which the wobble signal and the pre-pit signal are synchronized. Since the mask circuit 44 can be constituted by a logic circuit, there is an advantage that it can be further developed, for example, by calculating the periodicity of a signal obtained by binarizing the push-pull signal and periodically generating a gate signal. As a result, although the pre-pit 18 exists, the gate signal can be complemented even when the signal cannot be output due to the failure in binarization.

The pre-pit detection device 1 according to the first or second embodiment of the present invention is used as the gate generation circuit 45.
5 may be used. This makes it possible to stably detect the pre-pits 18 in various situations and remove noise components detected at timings other than the pre-pit signal.

[Fifth Embodiment] The fifth embodiment of the present invention is different from the third embodiment of the present invention in that a prepit detection circuit 15 includes a gate generation circuit 45 and a switch as shown in FIG. That is, circuits 46 and 47 are provided. Other technical contents are the same as those of the third embodiment of the invention, and the same reference numerals as those of the third embodiment of the invention are used.
Illustration and detailed description are omitted.

As shown in FIG. 10, the pre-pit detection circuit 15 includes switch circuits 46 and 47 for turning on / off the transmission of the signal by the gate signal output from the gate generation circuit 45 before the input to the differentiating circuit 42 or the zero-cross detection. Circuit 43
In this case, each circuit is inserted before input to the circuit, and each circuit is operated only at the timing when the pre-pit exists. As an example of a signal waveform, a zero-cross detection signal when a switch circuit 47 is inserted before the zero-cross detection circuit 43 is shown in a switch circuit output signal of FIG. At that time, the switch circuit 47 is turned ON / OFF by the gate signal shown in the figure, and outputs a switch circuit output signal. Since no signal is input except at the timing when the pre-pit exists due to the gate signal, the signal has no noise, and the zero-cross detection circuit 43
Does not make a false detection.

The pre-pit detection device 1 according to the first or second embodiment of the present invention is used as the gate generation circuit 45.
5 may be used. This makes it possible to stably detect the pre-pits 18 in various situations and remove noise components detected at timings other than the pre-pit signal.

[Embodiment 6] Embodiment 6 of the present invention is different from Embodiment 4 or 5 of the present invention in that
The point is that the gate generation circuit 45 is provided with a delay circuit for delaying the output. Other technical contents are the same as those of the fourth or fifth embodiment of the present invention, and the fourth and fifth embodiments of the present invention are the same.
The same reference numerals are used and illustration and detailed description are omitted.

Although a delay occurs in the electric circuit, as in the fourth or fifth embodiment of the present invention, the propagation time differs between signals of two different systems of a pre-pit detection circuit system and a gate generation circuit system. Since the delay time of the filter or the switch is relatively long, a delay occurs from the original pre-pit detection position as in the output of the differentiating circuit shown in FIG. Therefore, as shown in FIG. 11, the output of the zero-cross detection circuit 43 is masked by using a gate signal delay signal obtained by adjusting the timing of the gate signal with a delay substantially equal to the delay time, so that an accurate pre-pit position can be detected. And increase the degree of freedom in circuit design.

[Seventh Embodiment] The seventh embodiment of the present invention is different from the fourth, fifth or sixth embodiment in that a recording mask circuit described later is provided.
The other technical contents are the same as those of the fourth, fifth or sixth embodiment of the present invention, and the same reference numerals as those of the fourth to sixth embodiments of the present invention are used, and illustration and detailed description are omitted.

At the time of recording information on the optical disk 6, in order to accurately adjust the width and length of the recording mark, the amount of light is modulated at a high speed by a recording laser emission waveform (example) as shown in FIG. Therefore, at the time of recording mark formation, this light amount fluctuation also occurs in the reflected signal from the optical disk 6, and the push-pull signal is also in an unstable state. In order to detect the pre-pit 18, it is necessary to select a time when the push-pull signal is stable.
It is necessary to detect a pre-pit signal when recording in a space where the laser emits light with a constant light amount. Therefore,
Output stage of gate generation circuit 45 or mask circuit 44
At the timing when the light amount of the light beam emitted from the light source 1 changes within a certain predetermined time (that is, at the time of forming a recording mark)
In this case, a recording mask circuit (not shown) for outputting a recording mask signal (FIG. 12), which is a signal for inhibiting the output of the prepit signal, is mounted. Of course, the timing at which the light amount of the light source changes within a certain predetermined time differs depending on the recording film configuration of the optical disk 6, and therefore, when modulating the light source when recording a space, masking is performed at this time.

Therefore, it is possible to prevent erroneous detection of the pre-pit signal caused by the fluctuation of the light amount of the light beam.

[0058]

According to the first aspect of the present invention, it is possible to set an optimum slice level corresponding to the level of a noise component including an information signal, which varies depending on the conditions of an optical system and an optical disk. Erroneous detection can be eliminated.

According to a second aspect of the present invention, in the pre-pit detecting apparatus according to the first aspect, the level of a predictable noise component can be quickly switched to a preset slice level, and the demand for an amplitude detection circuit is increased. Since the accuracy can be kept low, the cost of the apparatus can be reduced.

According to the third aspect of the present invention, since the peak position of the pre-pit signal is detected, it is possible to accurately detect the pre-pit position regardless of the amplitude of the pre-pit signal which varies depending on the conditions of the optical system and the optical disk.

According to a fourth aspect of the present invention, in the pre-pit detecting device according to the third aspect, since the peak detecting circuit can be constituted by a differentiating circuit and a zero-cross detecting circuit, the pre-pit position can be detected at low cost.

According to a fifth aspect of the present invention, in the pre-pit detecting device according to the fourth aspect, it is possible to remove a noise component detected at a timing other than the pre-pit signal. In addition, an inexpensive and flexible logic circuit can be used as the mask circuit, and further functional improvement can be easily performed.

According to a sixth aspect of the present invention, in the pre-pit detecting device according to the fourth aspect, a noise component detected at a timing other than the pre-pit signal can be removed by an analog circuit.

According to a seventh aspect of the present invention, in the pre-pit detecting device according to the fifth or sixth aspect, the pre-pit is stably detected in various situations, and a noise component detected at a timing other than the pre-pit signal is detected. Can be removed.

According to an eighth aspect of the present invention, in the pre-pit detection device according to any one of the fifth to seventh aspects, a gate signal corrected for a circuit delay, which is generated depending on a circuit configuration, can be generated. Pre-pit position can be detected,
The degree of freedom in circuit design increases.

According to the ninth aspect of the present invention, in the pre-pit detecting device according to any one of the fifth to eighth aspects, it is possible to prevent erroneous detection of a pre-pit signal caused by a change in light amount of a light beam.

The tenth aspect of the present invention provides the first to ninth aspects.
The same operation and effect as those of the pre-pit detection device according to any one of the above are achieved.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a recording surface on an optical disc.

FIG. 3 is a waveform diagram of an actual wobble signal, a pre-pit signal, and a push-pull signal including a noise component.

FIG. 4 is a block diagram of a prepit detection circuit of the optical disk device.

FIG. 5 is a block diagram of a slice level setting circuit of the optical disc device according to the second embodiment of the present invention.

FIG. 6 is an enlarged plan view of a recording surface on an optical disc for explaining an optical disc apparatus according to a third embodiment of the present invention;
FIG. 4B is a waveform diagram (b) of a signal extracted therefrom.

FIG. 7 is a block diagram showing a circuit configuration of a pre-pit detection circuit (peak detection circuit) according to a third embodiment of the present invention.

FIG. 8 is a waveform chart of a signal for explaining Embodiments 3, 4, and 5 of the present invention.

FIG. 9 is a block diagram showing a circuit configuration of a prepit detection circuit (peak detection circuit) according to a fourth embodiment of the present invention.

FIG. 10 is a block diagram showing a circuit configuration of a prepit detection circuit (peak detection circuit) according to a fifth embodiment of the present invention.

FIG. 11 is a waveform diagram of a signal for explaining the sixth embodiment of the present invention.

FIG. 12 is a signal waveform illustrating a seventh embodiment of the present invention.

[Explanation of symbols]

 23 Amplitude detection circuit 25 Slice level setting circuit 26 Binarization circuit 42 Differentiation circuit 43 Zero cross detection circuit 44 Mask circuit 45 Gate generation circuit 46 Switch circuit 47 Switch circuit

Claims (10)

[Claims] 1. An optical disk on which information recording tracks and guide tracks for forming a pre-pit on which address information is recorded and guiding a light beam to the information recording tracks are provided, and on which information can be recorded. On the other hand, in a pre-pit detection device for obtaining a pre-pit signal from the pre-pit when recording or reproducing information, an amplitude for detecting an amplitude of a noise component including an information signal with respect to a reproduction signal of the optical disc including the pre-pit signal A detection circuit; a binarization circuit that binarizes the reproduction signal using a predetermined slice level to detect the pre-pit signal; and a slice level setting circuit that sets the slice level based on the amplitude. Pre-pit detection device. 2. The slice level setting circuit prepares a plurality of different slice levels and sets a slice level by selecting one of the plurality of slice levels based on the amplitude. Item 2. The pre-pit detection device according to Item 1. 3. An optical disk on which information recording tracks and guide tracks for forming a prepit on which address information is recorded and for guiding a light beam to the information recording tracks are provided, and on which information can be recorded. On the other hand, a prepit detection device for obtaining a prepit signal from the prepit when recording or reproducing information, comprising a peak detection circuit for detecting a peak position of the prepit signal. 4. A peak detection circuit comprising: a differentiation circuit for differentiating a reproduction signal of the optical disk including the pre-pit signal; and a zero-cross detection circuit for detecting a zero-cross point of an output of the differentiation circuit. Claim 3
4. The pre-pit detection device according to 1. 5. The reproduction signal is output at a certain slice level.
5. The pre-pit detection device according to claim 4, further comprising: a gate generation circuit for converting a value into a value; and a mask circuit for prohibiting an output of the zero-cross detection circuit based on an output of the gate generation circuit. 6. The reproduction signal is reproduced at a certain slice level.
5. The semiconductor device according to claim 4, further comprising: a gate generation circuit for converting a value into a value; and a switch circuit for turning on / off an input to the differentiation circuit or the zero-cross detection circuit according to an output of the gate generation circuit. The described pre-pit detection device. 7. The pre-pit detection device according to claim 5, wherein the pre-pit detection device according to claim 1 or 2 is provided as the gate generation circuit. 8. The pre-pit detection device according to claim 5, wherein said gate generation circuit includes a delay circuit for delaying its output by a predetermined amount. 9. A recording mask circuit for outputting a signal for inhibiting the output of the pre-pit signal at a timing when the light amount of the light beam fluctuates within a predetermined time during the recording of the information. The pre-pit detection device according to claim 5. 10. An optical system for converging the light beam on the optical disc and condensing the reflected light on a light receiving element, a reproducing circuit for detecting information recorded on the optical disc from an output signal of the light receiving element, A servo circuit for detecting position information of the light beam on the optical disk from the output information and controlling an irradiation position of the light beam on the optical disk via a predetermined mechanism based on the position information; And a pre-pit detecting device according to any one of claims 1 to 9, wherein the pre-pit detecting device detects address information recorded on the optical disc or generates a recording clock. apparatus.