JPH0256743A - Phase difference detector - Google Patents

Abstract

PURPOSE:To accurately realize detection by obtaining the phase advancing delaying discriminating signal of a side beam detecting signal. CONSTITUTION:A main beam detecting signal St from an adding part 13, detecting signals Se and Sf from light detecting parts 12e and 12f for a side beam respectively pass through level comparators 21, 22 and 23 and waveform shaping output signals Pt,Pe and Pf are obtained. A D-shaped flip flop D-FF24 detects the advancing/delaying of the phase of a signal Pe for the signal Pt and sends a comparing output signal Ss to a switching part 25. A D-EF 26 detects the mutual phase relation of signals Pe and Pf and derives a comparing output signal Sp to an output terminal 28. The signal Pf becomes a polarity inverting waveform shaping output signal, the inverse of Pf by an inverter 29 and is supplied to the D-FF 26 and an exclusive OR circuit 27. A pulse output signal Pd from the circuit 27 is derived through a low pass filter LPF 30 to an output signal Sh to an output terminal 31.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A Industrial field of application B Outline of the invention Conventional technology Examples of means for solving the problems to be solved by the invention G-1 Configuration (Fig. 1) G-2 Operation (Figs. 1 and 2) 3) (,-3 Modification H Effect of the Invention A Industrial Field of Application The present invention is directed to a so-called 3 optical beam system in which three optical beams 1 including a main beam and two side beams are used. The present invention relates to a phase difference detection device for detecting a phase difference state between detection signals of two side beams from a reproduction system of an optical disc employing a beam system.

B. Summary of the Invention The present invention provides an optical disc using the so-called 3-beam system, in which three light beams are used, consisting of a main beam and two side beams located on both sides of the main beam. In a phase difference detection device that detects a phase difference state between detection signals of two side beams obtained from a reproduction system through a photosensitive section provided therein, each of the two side beams is detected from the photosensitive section. The phase advance of either the detection signal for each of the two side beams, or the difference signal obtained by taking the difference between the two side beams, with respect to the detection signal for the main beam obtained together with the detection signal for the main beam. a first phase comparison unit that detects a delay;
a second phase comparison section that detects a mutual phase relationship between detection signals for each of the two side beams; and a second phase comparison section that detects a mutual phase relationship between detection signals for each of the two side beams; An operation for detecting the lead or lag of a phase and an operation for detecting a lead or lag of one phase with respect to the other are selectively performed according to the comparison output signal obtained from the first phase comparator, and the second phase From the comparison section, the phase lead/lag state between the detection signals for each of the two side beams,
Alternatively, by providing a phase comparison control unit that sets a state in which a phase lead/delay determination signal representing the phase lead/delay state and phase difference between the detection signals of the two side beams is obtained. Accurately detects the phase advance/delay state and phase difference between the detection signals of each of the two side beams with a relatively simple configuration even when the optical disk on which the light beam is incident is eccentrically rotated. It has been made possible.

C. Conventional technology In the reproduction system of an optical disk system, a spiral recording track is formed on the optical disk to surround its central hole, or a large number of recording trunks are arranged concentrically. When scanning with a light beam while the optical disk rotates around the central hole, tracking control is used to ensure that the light beam always reaches the recording track accurately and is properly focused on the recording track. and focus control are required.

Such tracking control and focus control are usually carried out under the condition that a light beam is made incident on an optical disk through an optical head, is modulated by a recording track on the optical disk, and then guided again through the optical head to a photosensitive section. From the output signal obtained in the photosensitive section, a tracking error signal and a focus error signal are formed according to the arrival status and focusing status of the light beam to the recording track, and based on these, the tracking error signal and the focus error signal are generated. This is done by controlling the position of the optical means.

An example of an optical head used in a reproducing system of an optical disk system in which such tracking control and focus control are performed is configured as shown in FIG. The optical head shown in FIG. 4 is assembled as a whole to form one optical system block 10, and an optical disk D having spiral or concentric recording tracks is formed.
It is assumed that the robot can move along the radial direction (direction shown by arrow A). In the optical system block 10, a laser beam emitted from a laser diode l serving as a light beam generation source passes through a grating 2 and then enters a polarizing beam splitter 3. Next, the laser beam that has passed through the analyzer surface 3a of the polarizing beam splitter 3 enters the collimator lens 4, where it is converted into a parallel light beam, and then passes through the quarter-wave plate 5 and passes through the objective lens. 6 and is focused by the objective lens 6 before being made to enter the optical disk D. The laser light beam incident on the optical disc D is modulated by the recording tracks formed on the optical disc D and is reflected to become a reflected laser light beam.

The reflected laser beam from the optical disk D returns via the objective lens 6, becomes a parallel light beam, and passes through the 174-wavelength plate 5. In this way, it passes through the 174-wavelength plate 5, enters the optical disk D, is reflected by the optical disk D, and is again 1
The reflected laser beam that has passed through the 74-wavelength plate 5 has a polarization direction of π/
It is rotated by 2.

The reflected laser light beam whose polarization direction has been rotated by π/2 enters the collimator lens 4, where it is made into a focused beam, and then enters the polarizing beam splitter 3, where it is turned into a focused beam. The light is reflected by the analyzer surface 3 a of No. 3 and guided to the photosensitive section 8 through the light receiving lens 7 . Then, the photosensitive section 8 detects the reflected laser beam modulated by the recording track formed on the optical disk D, and the change is extracted as a signal.

The objective lens 6 includes a focus control coil 9F for performing focus control by moving the objective lens 6 toward and away from the optical disk D along the optical axis direction, and a focus control coil 9F for controlling the focus by moving the objective lens 6 toward and away from the optical disk D along the optical axis direction. A tracking control coil 9T is provided for performing tracking control by moving the optical disc D in the radial direction, which is a direction perpendicular to the axis.

In such an optical system block 1o, the laser light beam from the laser diode 1 is divided into three laser light beams by passing through the grating 2, and in FIG. 4, one line is shown for simplicity. However, there are actually three laser beams on the optical path from the grating 2 onwards, reflected by the optical disk D, refracted by the polarizing beam splitter 3, and reaching the photosensitive section 8. These three laser beams include a main beam that tracks the recording track and reads information recorded on the optical disc D, and a main beam that tracks and tracks the recording track of the main beam.
In order to detect errors, two side beams positioned on both sides of the main beam are made incident. The manner in which the main beam and the two side beams are incident on the optical disk D is as shown in FIG. The beam spots Be and Bf by the two side beams are formed so as to coincide with the center position of the recording track T, and the beam spots Be and Bf by the two side beams are centered on the beam spot Bm by the main beam with respect to the direction along the recording track T and the direction perpendicular thereto. They are formed at symmetrical positions so that a portion of each is placed on the recording track T.

The main beam reflected at the optical disk D and 2
The side beams of the book are made to reach separate photodetectors in the photosensitive section 8 via cylindrical lenses forming a common receiving lens.

Therefore, the photosensitive section 8 has four photodetecting elements 11a and 11b adjacent to each other, as shown in FIG.

Main beam photodetector 11 consisting of 11c and lid
and two side beam photodetectors 1 separated from it.
2e and 12f, the main beam from the optical disc D is detected by the main beam photodetector 11, and the two side beams from the optical disc D are detected by the side beam photodetectors 12e and 12f. The beams are saved respectively. Then, detection outputs Sa, Sb, Sc, and Sd are obtained from the photodetecting elements 11a to 11lid forming the main beam photodetector 11, respectively, and these are added in an adding section 13, and the adding section 13 outputs an optical signal. A main beam detection signal St corresponding to the main beam from the disk D is obtained. Note that the photodetecting elements 11a to lid
Each of the detection outputs S a - S d obtained from the above is used to form a focus error signal in addition to forming a main beam detection signal St. Furthermore, side beam detection signals Se and Sf corresponding to each of the two side beams from the optical disk D are obtained from the side beam photodetectors 12e and 12f, respectively, and these are used to form a tracking error signal. used.

The main beam and two side beams incident on the optical disk D are positioned so that the beam spot arrangement relationship as shown in FIG. 5 is obtained under proper tracking and knocking conditions. Each of the main beam and two side beams reflected on the disc D is divided into two cases: when the reflection position is a part of the optical disc D where a recording track T is formed, and when the recording track T is formed on the optical disc D.
The recording track T for the main beam and two side beams is indicated by the arrow or arrow R in Fig. 5. When a state is assumed in which the main beam and the two side beams move in the indicated direction, each of the main beam and the two side beams relatively crosses a plurality of recording tracks T, and the main beam is detected accordingly. Each of the signal St and the side beam detection signals Se and Sf causes level fluctuations with a period corresponding to the interval and moving speed of the recording tracks T. At that time, the recording track T for the main beam and two side beams is
When the main beam detection signal St moves in the direction shown by the arrow, the main beam detection signal St has a level fluctuation as shown in FIG. As shown by the solid line in FIG. 7A, the level fluctuation has a phase lead of 90 degrees with respect to the main beam detection signal St. On the other hand, the side beam detection signal Sf has a level fluctuation as shown by the solid line in FIG. 7C. To,
The level fluctuation has a phase lead of 90 degrees with respect to the main beam detection signal St.

Further, when the recording track T moves in the direction shown by the arrow R with respect to the main beam and the two side beams, the main beam detection signal St changes in level as shown in FIG. In contrast, the side beam detection signal Se has a phase difference of 90° with respect to the main beam detection signal St, as shown by the solid line in FIG. 8A. On the other hand, the side beam detection signal Sr has a highly advanced level fluctuation, as shown by the solid line in FIG.
The level fluctuation has a phase lead of 90 degrees with respect to the main beam detection signal St.

In this way, when the main beam and the two side beams are properly positioned with respect to the optical disk D, the recording track T for the main beam and the two side beams is as indicated by the arrow in FIG. When moving in the direction indicated by arrow R, the side beam detection signal Se and the side beam detection signal Sf are 18
This results in level fluctuations with a mutual phase difference of 0 degrees.

The positions of the main beam and two side beams as described above with respect to the optical disk D are set by the optical system block lO.
This is done, for example, by adjusting the rotation angle of the grating 2 with the grating 2 mounted in a predetermined position. , optical disc D
The arrangement relationship between the beam spot Bm of the main beam and the beam spots Be and Bf of the two side beams under the proper tracking state in FIG. 9 is not in the proper state as shown by the solid line in FIG. 9
As shown by the dashed lines in the figure, the beam spots Be and Bf by the two side beams are respectively displaced from their proper positions to the outside of the recording track T, resulting in Be' and BV (hereinafter referred to as ° (referred to as “open state °゛)”
Or, as shown by the two-dot chain line in FIG. 9, the beam spots Be and B by the two side beams are
A state in which the respective positions of f are displaced from their proper positions to the inner side of the recording track T (Be" and Br" (hereinafter referred to as "
There is a possibility that the position of the main beam and the two side beams with respect to the optical disk D may be set so that the main beam and the two side beams are in a closed state (referred to as a closed state °°).

When the arrangement relationship between the beam spot Bm by the main beam and the beam spots Be and Bf by the two side beams is set to an "open state", the recording track T is in the first position with respect to the main beam and the two side beams. When moving in the direction indicated by the arrow in FIG. 5, the side beam detection signal Se changes in level compared to the level change in the proper state, as shown by the dashed line in FIG. 7A. On the other hand, the side beam detection signal Sf has a level change that is advanced in phase, as shown by a line at one point tl' in FIG. In addition, if the recording track T moves in the direction shown by the arrow R in FIG. 5 with respect to the main beam and the two side beams, , the side beam detection signal Se is assumed to have a level change whose phase is delayed compared to the level change in the proper state, as shown by the dashed line in FIG. 8A, and on the other hand,
The side beam detection signal Sf has a level change that is more advanced in phase than the level change in the proper state, as shown by the dashed line in FIG. 8C. On the other hand, the beam spot Bm by the main beam and the beam spot Be by the two side beams
When the arrangement relationship of and Bf is set to a “closed state”,
When the recording track T moves in the direction indicated by the arrow in FIG. 5 with respect to the main beam and the two side beams, the side beam detection signal Se is
As shown by the two-dot chain line in FIG.
As shown by the two-dot chain line in FIG. When the recording track T moves with respect to the beam in the direction shown by the arrow R in FIG. 5, the side beam detection signal Se is as shown by the two-dot ilI line in FIG. The side beam detection signal Sf is assumed to have a level change whose phase is advanced compared to the level change when it is in a proper state, and the side beam detection signal Sf is as shown in FIG.
As shown by the two-dot chain line, the level change is delayed in phase compared to the level change in the proper state.

D Problems to be Solved by the Invention Regarding the optical system block IO as described above, the beam spot Bm by the main beam and the beam spot Bm by the two side beams Be and B on the optical disk D
The arrangement of f is appropriate.

It is possible to detect whether the state is in the "open state" or "closed state," and furthermore, to detect the extent of the "open state" or "closed state." This is required when correcting the position settings of the main beam and the two side beams with respect to the optical disk D, and setting for tracking control.

Therefore, in order to perform such detection based on the level fluctuations of the main beam detection signal St and the side beam detection signals Se and Sf as described above, the rotating optical disk D was passed through the objective lens 6. The main beam and two side beams are made incident without tracking control, and as a result, due to the eccentricity of the rotating optical disk D, the recording track T provided on the optical disk D becomes the main beam. The beam and the two side beams are brought into a state in which they move in the direction indicated by the arrow mark or arrow R in FIG. 5, and under that state, the side beam detection signal Se and It is conceivable to obtain the mutual phase difference between the side beam detection signal Sf and the side beam detection signal Sf.

In such a case, under the condition that the moving direction of the recording track T with respect to the main beam and the two side beams is constant, it is determined based on the mutual phase difference between the side beam detection signal Se and the side beam detection signal S. Therefore, the arrangement relationship of the beam spot Bm by the main beam and the beam spots Be and Bf by the two side beams on the optical disc D is in the proper state, the "open state" and the "closed state".
Furthermore, it is possible to detect whether the opening is in the open state or the degree to which the opening is in the closed state.

However, since the movement of the recording track T with respect to the main beam and the two side beams is caused by the eccentricity of the rotating optical disk D, the recording track T with respect to the main beam and the two side beams is caused by the eccentricity of the rotating optical disk D. The moving direction of the optical disk D changes from the direction shown by the arrow in FIG. 5 to the direction shown by the arrow R, and vice versa, every half rotation period of the optical disk D. therefore,
Side beam detection signal Se and side beam detection signal Sf
Based on the mutual phase difference between the beam spot Bm of the main beam and the beam spots Be and Bf of the two side beams on the optical disc D, it is determined whether the arrangement relationship between the beam spot Bm by the main beam and the beam spots Be and Bf by the two side beams is in an appropriate state or in an open state. or"
Although it is possible to determine whether it is in the 'closed state' and to detect the degree of the 'open state' or 'closed state', the phase lead/lag state between the side beam detection signal Se and the side beam detection signal Sf is cannot be detected, therefore, the optical disc D
Beam spots Bm and 2 by the main beam at
Beam position by the side beam of the book) Is the arrangement relationship of Be and Bf in the open state or the closed state?
It is not possible to determine whether this is the case.

In view of this, the present invention provides an optical disc reproducing system that employs the so-called 3-beam system, in which three light beams consisting of a main beam and two side beams located on both sides of the main beam are used. 2, by the photosensitive part equipped on it.
It is possible to accurately detect the phase lead/delay state between the side beam detection signals obtained for each of the side beams of the book, or both the phase lead/delay state and the phase difference with a relatively simple configuration, and as a result, The arrangement relationship between the beam spot of the main beam and the beam spot of the two side beams on the optical disc is in a proper state.
To provide a phase difference detection device that can accurately determine whether the state is an open state or a closed state, and furthermore accurately detect the degree of an open state or a closed state. The purpose is to

E. Means for Solving the Problems In order to achieve the above-mentioned object, the phase difference detection device according to the present invention has an annular recording rack that surrounds a central hole and rotates around the central hole. Three light beams, consisting of a main beam and two side beams located on both sides of the main beam, which are incident on the optical disk and reflected by the optical disk, are transmitted to the first... A photosensitive section to be detected by second and third photodetecting means, and second and third lights connected to the photosensitive section and corresponding to the first detection signal corresponding to the main beam obtained from the first photodetecting means. Either one of the second and third detection signals corresponding to each of the first and second side beams respectively obtained from the detection means, or the difference between the second detection signal and the third detection signal is determined. a first phase comparator that detects the lead or lag in the phase of the difference signal obtained by the
a second phase comparison section that detects a mutual phase relationship between the detection signals of the second phase comparison section and a phase comparison control section;
In the phase comparison section, the phase lead/lag of the third detection signal with respect to the second detection signal is detected, and the phase lead/lag of the second detection signal with respect to the third detection signal is detected. is selectively performed according to the comparison output signal obtained from the first phase comparison section, and the second phase comparison section detects the phase lead/lag state between the second and third detection signals, or the phase lead/lag state between the second and third detection signals. It is configured to set a state in which a phase lead/lag determination signal representing a phase lead/lag state and a phase difference between the second and third detection output signals is obtained.

F effect In the phase difference detection device according to the present invention configured as described above, the comparison output signal obtained from the first phase comparator section is determined by the comparison output signal obtained from the annular recording track with respect to the three light beams incident on the optical disk. It has a change depending on the direction of movement, which is perpendicular to the tangential direction. The phase comparison control section determines, based on the comparison output signal obtained from the first phase comparison section, that the moving direction of the annular recording track with respect to the three light beams incident on the optical disk is, for example, the fifth When the direction is -, which corresponds to the direction indicated by the arrow in the figure, in the second phase comparator,
An operation is performed in which the phase lead or lag of the third detection signal with respect to the second detection signal is detected, and the moving direction of the annular recording track with respect to the three light beams incident on the optical disk is determined, for example, as described above. In the second direction corresponding to the direction shown by the arrow R in FIG. Allow the action to take place. As a result, even when the moving direction of the three light beams incident on the optical disk changes, the second phase comparator section changes the direction of movement to be perpendicular to the tangential direction of the annular recording track. and the third detection signal, or the second detection signal is
In addition to the phase lead/lag state between the third detection signals, a phase lead/lag determination signal is obtained that accurately determines the phase difference.

Then, based on the phase lead/lag discrimination signal, the beam spot of the main beam and the two beam spots on the optical disk are determined.
The placement relationship of the beam spot due to the book's side beam is
It is possible to determine whether the state is in the proper state, "open state" or "closed state", and furthermore, whether it is in the "°open state" or "°open state" or "
The degree of "closed state" can be accurately detected.

G Example G-1 configuration (Figure 1) FIG. 1 shows an example of a phase difference detection device according to the present invention.

An example of this is an optical disc D shown in FIG.
An optical disk is provided with an annular recording track such as a spiral recording track surrounding a central hole or a large number of concentrically arranged recording tracks, and is rotated around the central hole. As shown in Fig. 4, three light beams consisting of a main beam and two side beams located on both sides of the main beam are made incident, and the three light beams reflected by the optical disk are received. The photosensitive section 8 shown in FIG. 6 is provided in the optical system block. Regarding the photosensitive section 8 shown in FIG. 1, parts and signals corresponding to each part and each signal shown in FIG. 6 are shown with the same reference numerals as in FIG. 6, and redundant explanation will be omitted. be done. The main beam and two side beams incident on the optical disk from the optical system block are under proper tracking conditions,
The incident mode is such that a beam spot Bm by the main beam and beam spots Be and Bf by the two side beams are formed on the optical disk as shown in FIG.

Then, the main beam detection signal SL obtained from the addition section 13 in the photosensitive section 8, the side beam light detection section 12e
The side beam detection signal Se obtained from the side beam detection section 12 and the side beam detection signal Sf obtained from the side beam photodetection section 12 are respectively supplied to comparison input terminals of the level comparators 21, 22 and 23. The reference input terminals of each of level comparators 21, 22, and 23 are kept at ground potential.Level comparator 2
1, 22 and 23, the husband h and the waveform shaped output signal Pt
, Pe and Pf are obtained.

The waveform-shaped output signals pt and Pe obtained from the level comparators 21 and 22 are connected to D-type flip-flops (D
-FF) 24 clock terminal (C) and data terminal (D
) are supplied respectively. The D-FF 24 forms a phase comparison section that detects the phase lead/lag of the waveform shaped output signal Pe with respect to the waveform shaped output signal Pt, and a comparison output signal Ss is obtained from its output terminal (Q) and is interlocked. switch 25a
.

Switching section 2 with built-in 25b, 25C and 25d
5 control terminal. Further, the waveform-shaped output signal Pe obtained from the level comparator 22 is passed through the switches 25a and 25b in the switching section 25.
ζ, r)-can be supplied to the clock terminal (C) and data terminal (D) of the FF 26, respectively, and
It is supplied to one input terminal of the exclusive OR circuit 27. D-F F 26 is a waveform shaping output signal Pc
A phase comparison section is formed to detect the mutual phase relationship between the output signal Pf and the waveform-shaped output signal Pf, and a comparison output signal Sp is obtained from its output terminal (Q) and is led out to the output terminal 28. Further, the waveform-shaped output signal P" obtained from the level comparator 23 is converted into a polarity-inverted waveform-shaped output signal "■" in the inverter 29, and is sent to the clock terminal of the D-FF 26 via the switch 25c and 25d in the switching section 25. (C) and data terminal (D), respectively, and is also supplied to the other input terminal of the exclusive OR circuit 27. From the exclusive OR circuit 27, a pulse output signal Pd is obtained and supplied to a low pass filter (LPF) 30, LPF3
The output signal sh from 0 is derived to the output terminal 31.

G-2 Operation (Fig. 1, Fig. 2, Fig. 3) When performing the detection operation by the example of the phase difference detection device according to the present invention as described above, the optical system is attached to the rotating optical disk. The main beam and two side beams passing through the block are made incident without tracking control, and as a result, due to the eccentric rotation of the optical disk, an annular recording track provided on the optical disk is formed. A state is taken in which the main beam and the two side beams move in the direction shown by the arrow or arrow R in FIG. 5. In such a state, the main beam detection signal st and the side beam Beam detection signals Se and S
[is as shown by the solid line, the dash-dot line, or the dash-double line in FIGS. 7A, B, and C1 and FIG. () and is supplied to level comparators 21, 22 and 23, respectively.

In this way, the arrangement relationship of the beam spot h B m by the main beam and the beam spots Be and Bf by the side beam on the optical disk is such that the beam spots Be and 13 [ by the side beam When in the "open state", which will be referred to as "IS e' and Bf", due to its eccentric rotation during each rotation of the rotating optical disk, the annular recording track a half-rotation period HL during which the main beam and the two side beams move in the direction indicated by the arrow in FIG.
And, following that, an annular recording track is indicated by arrow R in FIG. 5 for the main beam and two side beams.
During the half-rotation period HR during which the beam moves in the direction indicated by , the level and
The waveform-shaped output signal pt obtained from the comparator 21 is obtained as a rectangular wave signal as shown in FIG. 2A. On the other hand, as shown in FIG. 2B, the waveform-shaped output signal Pe obtained from the level comparator 22 based on the side beam detection signal Se is 90% higher than the waveform-shaped output signal pt during the half-rotation period HL. It is obtained as a rectangular wave signal whose phase is advanced by a phase angle greater than
The signal is obtained as a rectangular wave signal whose phase is delayed by a phase angle greater than 90 degrees. Furthermore, the waveform-shaped output signal Pf obtained from the level comparator 23 based on the side beam detection signal Sr is converted into an inverted waveform-shaped output signal T obtained by passing through the inverter 29, as shown in FIG. , during the half-rotation period HL, the waveform-shaped output signal P
It is obtained as a rectangular wave signal whose phase is advanced by a phase angle smaller than 90 degrees with respect to t, and in the half-rotation period HR, the phase is advanced by a phase angle smaller than 90 degrees with respect to the waveform shaped output signal Pt. Obtained as a delayed square wave signal.

As a result, in the D-FF 24 to which the waveform-shaped output signals PL and Pe are supplied, the level of the waveform-shaped output signal Pe at the rising edge of the waveform-shaped output signal PL is detected, and the comparison output signal obtained from the D-FF 24 is detected. Ss is
As shown in FIG. 2C, it takes a constant positive value during the half-rotation period HL, and takes a constant negative value during the half-rotation period HR. In the switching unit 25 to which the comparison output signal Ss from the D-FF 24 is supplied to the control terminal, the switches 25a and 25c are turned on during the half-rotation period HL in which the comparison output signal Ss takes a positive L constant value. , and the switches 25b and 25d are turned off. Also, during the half-rotation period HR in which the comparison output signal Ss takes a constant negative value, the switches 25b and 25d are turned on, and the switches 25a and 25c are turned off. state.

Therefore, during the half-rotation period HL, the waveform-shaped output signal Pe is supplied to the data terminal (D) of the D-FF 26 through the switch 25a in the switching unit 25, and the polarity-inverted waveform-shaped output signal Pf is supplied to the data terminal (D) of the D-FF 26 through the switch 25a in the switching unit 25. 25c to the clock terminal (C) of D-FF26.
6, the level of the waveform shaping output signal Pe at the rising edge of the polarity inversion waveform shaping output signal Pf is detected, and the phase lead/lag of the waveform shaping output signal Pe with respect to the polarity inversion waveform shaping output signal ear is detected. The comparison output signal Sp obtained from the -FF 26 is assumed to take a constant positive value, as shown in FIG. Also, the half-rotation period H
In R, the waveform-shaped output signal Pe is supplied to the clock terminal (C) of the D-FF 26 through the switch 25b in the switching section 25, and the polarity-inverted waveform-shaped output signal Pf is supplied to the D-FF 26 through the switch 25d in the switching section 25. The D-FF 26 detects the level of the polarity inverted waveform shaping output signal Pf at the rising edge of the waveform shaping output signal Pe, and determines the polarity of the waveform shaping output signal Pe. The phase lead or lag of the inverted waveform-shaped output signal Pf is detected, and the comparison output signal Sp obtained from the D-FF 26 assumes a constant positive value, as shown in FIG.

In this way, the switching unit 25 switches the D-FF 26 depending on the polarity of the comparison output signal Ss obtained from the D-FF 24.
The comparison output signal Sp obtained from D-FF 26 takes a constant positive value in both L and HR (half rotation period). Become something.

Further, an exclusive OR circuit 2 is supplied with the waveform shaping output signal Pe and the polarity inverted waveform shaping output signal f.
As shown in FIG. 2F, for the pulse output signal Pd from 7, one of the waveform shaping output signal Pe and the polarity inverted waveform shaping output signal r is at a high level in both the half rotation periods HL and 11R. The pulse train has a width corresponding to the period during which the other signal takes a low level, that is, a width corresponding to the phase difference between the waveform-shaped output signal Pe and the polarity-inverted waveform-shaped output signal Clove. Thereby, the output signal sh obtained from the LPF 30 has a level corresponding to the phase difference between the waveform-shaped output signal Pe and the polarity-inverted waveform-shaped output signal T, as shown in FIG. 2G.

On the other hand, the beam spot Bm of the main beam and the beam spot Bm of the side beam on the optical disc
When the positional relationship of e and Bf is in a "closed state" in which the beam spots Be and B by the side beams become the beam spots Be and Bf indicated by two-dot chain lines in FIG. , during the half-rotation period HL and the half-rotation period HR, the waveform-shaped output signal pt is obtained as a rectangular wave signal as shown in FIG. 3A (same as the rectangular wave signal shown in FIG. 2A). On the other hand, as shown in FIG.
It is obtained as a rectangular wave signal whose phase is advanced by a phase angle smaller than 90 degrees, and during the half-rotation period HR, a rectangular wave signal whose phase is delayed by a phase angle smaller than 90 degrees with respect to the waveform shaped output signal PL is obtained. obtained as. Further, as shown in the third diagram, the polarity-inverted waveform-shaped output signal Pf obtained from the waveform-shaped output signal Pr through the inverter 29 is rotated at an angle of 90 degrees with respect to the waveform-shaped output signal Pt during the half-rotation period HL. In addition, during the half-rotation period LIR, a rectangular wave signal is obtained as a rectangular wave signal whose phase is delayed by a phase angle greater than 90 degrees with respect to the waveform shaped output signal PL. It will be done.

As a result, in the D-FF2/I to which the waveform-shaped output signals pt and Pe are supplied, the level of the waveform-shaped output signal Pe at the rising edge of the waveform-shaped output signal pt is detected, and the level obtained from the D-FF 24 is detected. Comparison output signal S
As shown in FIG. 3C, s takes a constant positive value during the half-rotation period HL, and takes a constant negative value during the half-rotation period HL.

Therefore, during the half-rotation period HL, the waveform-shaped output signal Pe is supplied to the data terminal (D) of the D-FF 26 through the switch 25a in the switching unit 25, and the polarity-inverted waveform-shaped output signal Pf is supplied to the data terminal (D) of the D-FF 26 through the switch 25a in the switching unit 25. 25c to the clock terminal (C) of D-FF26.
6, the level of the waveform shaping output signal Pe at the rising edge of the polarity inversion waveform shaping output signal Pf is detected, and the phase lead/lag of the waveform shaping output signal Pe with respect to the polarity inversion waveform shaping output signal H is detected. The comparison output signal SP obtained from the -FF 26 is assumed to take a constant negative value, as shown in FIG. Also, the half-rotation period H
In R, the waveform shaping output signal Pe is supplied to the clock terminal (C) of the D-FF 26 through the switch 25b in the switching section 25, and the polarity inverted waveform shaping output signal Pe is supplied to the D-FF 243 through the switch 25d in the switching section 25. In D to FF26, the level of the polarity inverted waveform shaping output signal -Pr at the rising edge of the waveform shaping output signal Pe is detected, and the waveform shaping output signal is supplied to the data terminal (D) of the waveform shaping output signal Pe. The phase lead or lag of the polarity inverted waveform shaping output signal - "]" with respect to the signal Pe is detected, and the comparison output signal Sp obtained from the D-FFZ6 takes a constant negative value as shown in FIG. 3E. That is, the comparison output signal Sp obtained from the D-FF 26 takes a constant negative value during both the half-rotation periods HL and HR.

Further, an exclusive OR circuit 2 is supplied with the waveform shaping output signal Pe and the polarity inverted waveform shaping output signal Pf.
As shown in FIG. 3F, in the pulse output signal Pd from 7, one of the waveform shaping output signal Pe and the polarity inverted waveform shaping output signal Clo is high in both the half rotation period HL and 1■R. The pulse train has a width corresponding to a period in which one level is high and the other is low level, that is, a width corresponding to the phase difference between the waveform-shaped output signal Pe and the polarity-inverted waveform-shaped output signal Clove. Thereby, the output signal sh obtained from the LPF 30 has a level corresponding to the phase difference between the waveform-shaped output signal Pe and the polarity-inverted waveform-shaped output signal 7, as shown in FIG. 3G.

In this way, the comparison output signal s obtained from the D-FF26
p is output as a phase lead/lag determination signal representing the phase lead/lag state between the waveform shaping output signal Pe and the waveform shaping output signal Pf, and therefore between the side beam detection signal Se and the side beam detection signal Sf. It will be led out to the terminal 28, and the positional relationship of the beam spot Bm of the main beam and the beam spots Be and Bf of the side beams on the optical disc will be in an "open state" with a constant positive value. , the positional relationship between the beam spot Bm of the main beam and the beam spots Be and Bf of the side beams on the optical disk is in a "closed state" with a constant negative value.

Further, the output signal sh obtained from the LPF 30 is a detection signal that represents the phase difference between the waveform-shaped output signal Pe and the waveform-shaped output signal Pf, and therefore between the side beam detection signal Se and the side beam detection signal Sf. This signal is output to the output terminal 31 as an output signal, and when the positional relationship of the beam spot Bm by the main beam on the optical disc and the beam spots Be and Bf by the side beam is in the "open state" or the "closed state Pa", , represents the degree of its "open state" or "closed state".

G-3 Modification In the above example, the side beam detection signal Se obtained from the side beam photodetector 12e is supplied to the comparison input terminal of the level comparator 22, but instead of the side beam detection signal Se, , side beam detection signal S
A signal obtained by taking the difference between e and the side beam detection signal Sf obtained from the side beam photodetector 312f may be supplied.

Further, the side beam detection signal Se is supplied to the comparison input terminal of the level comparator 22, and the level comparator 22 also receives the side beam detection signal Se.
The side beam detection signal Sf is supplied to the comparison input terminal of the comparator 23, but instead, the side beam detection signal S' is supplied to the comparison input terminal of the level comparator 22, and
Even if the side beam detection signal Se is supplied to the comparison input terminal of A comparison output signal Sp is derived to the output terminal 28 as a phase lead/lag discrimination signal representing A derived output signal sh is obtained.

Furthermore, in place of the D-FF 26 in the above example, a phase lead/lag determination signal can be obtained that detects the phase difference in addition to the phase lead/lag state between the waveform shaping output signal Pe and the waveform shaping output signal Pf. A phase comparator may also be used. In such a case, the exclusive or times provided in the above example! 27. LPF 30 and output terminal 31 are unnecessary.

Effects of the Invention H As is clear from the above explanation, according to the phase difference detection device according to the present invention, the main beam and the two
A main beam detection signal and a main beam detection signal obtained from an optical disc playback system that adopts the so-called 3-beam system, in which three light beams consisting of the side beams of a book are used, and the two light beams are obtained through a photosensitive section provided therein. The phase lead/lag state or both the phase lead/lag state and the phase difference between the side beam detection signals of the side beam detection signals can be accurately detected. A late discrimination signal can be obtained with a relatively hour wheel configuration.

Then, based on the phase lead/lag discrimination signal, the beam spot of the main beam and the two beam spots on the optical disk are determined.
The placement relationship of the beam spot due to the book's side beam is
It is possible to accurately determine whether the device is in a proper state, an “open state” or a “closed state,” and also to accurately detect the degree of the “open state” or the “closed state.”

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the phase difference detection device according to the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation of the example shown in FIG. 1, and FIG. A schematic configuration diagram showing an example of an optical head used in a reproduction system of an optical disk system together with an optical disk. FIG. 5 is a diagram for explaining the main beam and two side beams that enter the optical disk from the optical head shown in FIG. 4. The figure provided, Figure 6, is the 4th
7 and 8 are respectively explanations of the main beam detection signal and side beam detection signal obtained from the photosensitive section shown in FIG. 5. FIG. 9 is a diagram used to explain the arrangement of the beam spot of the main beam and the beam spots of the two side beams on the optical disc. In the figure, 8 is a photosensitive section, 10 is an optical system block, 11 is a main beam photodetector, 12e and 12f are side beam photodetectors, 13 is an adder, 2122 and 23 are level comparators, 24 and 26 is a D-FF, 25 is a switching section, 27 is an exclusive OR circuit, 29
is an inverter, and 30 is an LPF. Waveform embroidery of the optical system block No. 4 Example H 37 Figure 8 Beam spot mode Figure 9

Claims (1)

[Claims] An annular recording track surrounding a central hole is formed, and the main beam is incident on an optical disk that is rotated around the central hole and is reflected by the optical disk, and a main beam located on both sides thereof. a photosensitive section for detecting three light beams consisting of two side beams by first, second, and third photodetecting means, respectively; For the first detection signal corresponding to the obtained main beam,
The above-mentioned 2 obtained from the above-mentioned second and third photodetecting means, respectively.
Either of the second and third detection signals corresponding to each of the side beams of the book, or the phase of the difference signal obtained by taking the difference between the second detection signal and the third detection signal. a first phase comparison section that detects lead/lag; a second phase comparison section that detects a mutual phase relationship between the second and third detection signals; The operation of detecting the phase lead/lag of the third detection signal with respect to the detection signal and the operation of detecting the phase lead/lag of the second detection signal with respect to the third detection signal are the same as those of the first detection signal. is selectively performed according to the comparison output signal obtained from the phase comparison section,
The second phase comparator outputs a phase lead/lag state between the second and third detection signals, or a phase lead/lag state representing a phase lead/lag state and a phase difference between the second and third detection signals. A phase difference detection device comprising: a phase comparison control section for setting a state in which a discrimination signal is obtained;