JP2912981B2 - Optical information recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical information recording / reproducing apparatus for an optical information carrier provided with a guide groove for tracking such as a magneto-optical disk or a write-once optical disk. In particular, it relates to detection of tracking information.

[Prior Art] Conventionally, a guide groove is provided on an optical information carrier such as a magneto-optical disk or a write-once optical disk, and the tracking of an information recording / reproducing beam is controlled by using the guide groove. The technology is known. As a method for detecting tracking information, a method called a push-pull method has been mainly used. In this method, tracking information is obtained by detecting a difference in the intensity of ± 1st-order diffracted light generated when one light beam is applied to a guide groove.

However, this method utilizes the change in the light quantity distribution of the reflected light field from the optical information carrier in accordance with the difference in the intensity of the ± 1st-order diffracted light caused by the degree of the light beam impinging on the guide groove. The optical information carrier is greatly affected by the inclination of the optical information carrier with respect to the beam optical axis, the shape of the guide groove, the displacement of the lens optical axis with respect to the beam optical axis, and the displacement of the photodetector. For this reason, the demands on the mechanical properties of the optical information carrier are strict, and also for the optical information recording / reproducing device, the assembly adjustment accuracy of the optical head,
Sufficient attention must be paid to component displacement due to aging. Moreover, even if such care is taken, it is difficult to make the offset of the light beam with respect to the center axis of the track zero, and to reduce the lens shift, a course actuator and a fine actuator are required. An optical information recording / reproducing apparatus is complicated and expensive, for example, by adopting a two-stage servo system for controlling the optical information in conjunction with an eta.

As a method for solving such a problem, a three-beam method using three light beams is known.

This is because a laser beam emitted from a laser diode is converted into a parallel beam by a collimator lens, then converted into a 0th-order diffracted light and ± 1st-order diffracted light by a diffraction grating, the 0th-order diffracted light is a main light beam, and the ± 1st-order diffracted light is a sub-light. The light beam is condensed on the magneto-optical disk, and the data signal and focus information recorded on the magneto-optical disk can be obtained from the main light beam reflected from the magneto-optical disk. The tracking information can be obtained from the sub-light beam.

Here, on the magneto-optical disk, the spots of the two sub-light beams are such that their center scanning trajectories are on both sides of the center scanning trajectory of the main light beam, and the center scanning trajectory of the main light beam is on the center line of the track. When they are coincident, the sub-light beams are arranged so as to equally hit the guide grooves on both sides of the track, respectively, and are arranged so as to be equidistant with respect to the spot of the main light beam. These sub-light beams reflected from the magneto-optical disk are received by separate photodiodes, and the tracking information is obtained by taking the difference between the output signals of these photodiodes.

According to the three-beam method described above, the tracking information is detected using only the difference in the amount of light of the two sub-light beams, which are the ± 1st-order diffracted lights, so that it is hardly affected by the tilt of the disk with respect to the beam optical axis. Also, since the imaging spots of these sub-light beams need not deviate from the photodiodes that receive the reflected sub-light beams, the position adjustment of these photodiodes is easy.

By the way, when an optical information carrier is used for recording code data, a pre-pit is generally formed on the optical information carrier. As an example, a header portion indicating address information is formed as a pre-pit for each sector. Where such a pit exists, the amount of reflected light of the sub-light beam fluctuates, which affects the detection accuracy of tracking information. However, the length of the header portion is determined by the area where data is recorded (data area). , The effect is not so great.

On the other hand, the data area may be provided with a so-called ROM area in which data is previously recorded in pre-pits. When data is reproduced from such a ROM area, the reflected light amount of the sub-light beam fluctuates due to the pre-pit for a longer time than in the case of only the header portion, and correct tracking information cannot be obtained. Hereinafter, the effect of the pre-pit on the detection of the tracking information will be described with reference to FIG.

FIG. 5 (a) shows a guide groove on an optical information carrier and each light beam in a three-beam system. The space between the guide grooves is a track on which data is recorded. ± 1st order diffracted light (sub light beam)
Is shifted by 1/4 track pitch on both sides of the 0th-order diffracted light (main light beam) in the direction perpendicular to the track (direction of arrow X), and before and after the 0th-order diffracted light in the track direction (direction of arrow Y). Is set to 1.6 μm, and the optical information carrier is irradiated with a shift of about 40 μm.

Here, when viewed in the direction of the arrow X, it is assumed that the ± 1st-order diffracted lights are arranged on the right side of the 0th-order diffracted light and the -1st-order diffracted lights are arranged on the left side thereof. The reflected light amount of each light beam becomes maximum when the center of the light beam coincides with the center line of the track, and becomes minimum when it coincides with the center line of the guide groove. Therefore, now, the 0th-order diffracted light while rotating the optical information carrier, ±
When the first-order diffracted light is moved in the direction of the arrow X, the amount of reflected light of each light beam corresponding to the position of the center of the zero-order diffracted light changes as shown in FIG. 5B. That is, these reflected light amounts change periodically with the track pitch, but +1.
The change in the reflected light amount of the 0th-order diffracted light is advanced by 1/4 cycle than the change in the reflected light amount of the 0th-order diffracted light, and the change in the reflected light amount of the -1st-order diffracted light is delayed by 1/4 cycle.

FIG. 5 (b) shows the change in the amount of reflected light of each light beam when no prepit is formed on the track.
When the center of the 0th-order diffracted light coincides with the center line of the track, the reflected light amounts of the ± 1st-order diffracted light become equal, and when the center of the 0th-order diffracted light is shifted by 1/4 track pitch from the centerline of the track, the ± 1st order The difference in the amount of reflected light of the folded light is maximized.

The above description is directed to the case where the track is irradiated with a portion where no pre-pit is formed. However, when irradiating the portion where the pre-pit is formed, the reflected light of each light beam is intensity-modulated by the pre-pit. This is shown in FIGS. 5 (c) and 5 (c) 'with reference to the time axis t.

FIG. 5 (c) shows the change in the reflected light amount of the + 1st-order diffracted light, and FIG. 5 (c) 'shows the change in the reflected light amount of the -1st-order diffracted light. In each of the figures, the dashed line is a change in the amount of reflected light when there is no pre-pit. Even when there is a pre-pit, when the center of the + 1st order diffracted light coincides with the track center line, these reflected light amounts should be maximum. However, this is the case where the interval between the pre-pits, that is, the density is constant. In practice, the density of the pre-pit changes according to the information content, and the higher the density, the greater the light interference effect and the lower the amount of reflected light. For this, +
Even if the center of the first-order diffracted light coincides with the track center line, the amount of reflected light does not always become the maximum, and even if the center of the zero-order diffracted light coincides with the track center line, the reflected light amount of the ± 1st-order diffracted light Do not always match.

Therefore, in order to eliminate the influence of the pre-pit, the output signal of the photodetector that receives the reflected light of the ± 1st-order diffracted light is passed through an LPF (low-pass filter), and the average value (that is, the DC component) is removed except for the modulation by the pre-pit. It is conceivable that tracking information is obtained by extracting the DC components and comparing the levels of these DC components.

However, the DC component obtained is also shown in FIG.
As shown by the solid line as the average value in (c) ′, the average value varies depending on the modulation of the prepits, that is, also depends on the density of the prepits. The tracking information signal is as shown by a solid line in FIG. 5 (d). In FIG. 5 (d), the dashed line indicates the correct tracking information signal obtained from the reflected light amount of the ± 1st-order diffracted light indicated by the solid line in FIG. 5 (b) when there is no pre-pit, and it is clear from this comparison. Thus, a normal tracking information signal cannot be obtained.

The present applicants have proposed an optical information recording / reproducing apparatus which has solved the problem relating to lines (Japanese Patent Application No. 2-159892). Less than,
This will be described with reference to FIGS. 6 and 7.

FIG. 6 (a) is a top view of the optical system, and FIG. 6 (b) is a side view thereof, wherein 1 is a laser diode, 2 is a collimating lens, 3 is a diffraction grating, 4 and 5 are beam shaping prisms, 6
Is a beam splitter, 7 is a rising mirror, 8 is a focusing lens, 9 is a half mirror, 10 is a half-wave plate, 11 is a mirror, 12 is a converging lens, 13 is a cylindrical lens, and 13 and 15 are light detectors. Vessel, 16 is a Wollaston prism, 17 is a focusing lens, 18
Is a magneto-optical disk.

6 (a) and 6 (b), the laser diode 1
Is collimated by the collimating lens 2 and the beam shaping prisms 4 and 5 to form a parallel beam of circular spots. Become. Beam splitter 6
Then, the S that is slightly mixed in the incident main and sub light beams
It reflects all of the polarized light components and part of the P-polarized light components, and passes only the P-polarized light components. The main and sub light beams that have passed through the beam splitter 6 are raised by a rising mirror 7 and are focused on an optical information carrier 18 by a focus lens 8.

The track pitch on the optical information carrier 18 is 1.6 μm
Then, the sub-light beam is irradiated with 0.4 .mu.m (1/4 times the track pitch) to the left and right in the track width direction of the main light beam and about 40 .mu.m before and after in the longitudinal direction of the track.

Assuming that the optical information carrier 18 is a magneto-optical medium, the Kerr effect corresponding to the magnetic field strength due to the recording of information is generated in the main and sub reflected light beams, the polarization plane is rotated to generate an S-polarized component, and P The polarization component decreases. Thus, the optical information carrier 18
The main and sub-light beams reflected from the mirror pass through a focus lens 8 and are reflected by a rising mirror 7 to be split by a beam splitter 6.
Is incident on. The beam splitter 6 reflects all of the S-polarized light components and part of the P-polarized light components of the main and sub light beams.

The main and sub-light beams reflected by the beam splitter 6 are split into two by a half mirror 9 and one of the main and sub-light beams reflected by the half mirror 9 is reflected.
The sub-light beam passes through the half-wave plate 10 and is divided by the Wollaston prism 16 into a P-polarized component and an S-polarized component. The P-polarized light component and the S-polarized light component of the main light beam are separated by a focusing lens 17 into a photodetector comprising a two-division photodiode.
Irradiate 15 separate photodiodes. By taking the difference between the output signals of these photodiodes, an information signal magnetically recorded on the optical information carrier 18 can be obtained, and by taking the sum of the output signals of these photodiodes, the information signal is recorded on the optical information carrier 18 by a pre-pit. The resulting bright and dark signals can be obtained.

The other main and sub light beams that have passed through the half mirror 9 pass through the converging lens 12 and the cylindrical lens 13, are reflected by the mirror 11, and are irradiated on the photodetector 14. The photodetector 14 is composed of a four-division photodiode and two single photodiodes disposed on both sides of the four-division photodiode. The main light beam (0-order diffracted light) reflected by the mirror 11 is reflected by the four-division photodiode. ), And one sub-light beam (+ 1st-order diffracted light) reflected on the mirror 11 to one of the two single photodiodes, and the other sub-light beam reflected on the mirror 11 onto the other single photodiode. (-1st-order diffracted light) is irradiated.

A tracking information signal and a focusing information signal are formed from the output signal of the photodetector 14.
The means for detecting these information signals will be described with reference to the drawings. However, in the figure, 14a is divided into four photo-diodes, 14a ₁ to 14A ₄ are photodiode, 14b, 14c are photodiode, the operation amplifier 19 and 20, the LPF, 22 is a waveform equalizing circuit 21, 23 the upper Envelope detection circuit, 24 is a lower envelope detection circuit, 25 is a differential amplifier, 26 is a switch, 27 and 28 are amplifiers, 29 is a differential amplifier, 30, 31 is a waveform equalization circuit, and 32 and 33 are upper Envelope detection circuit, 34 and 35 are lower envelope detection circuits, 36 is an operational amplifier, 37 is a switch, 38 and 39 are level comparison circuits, 4
0 is a delay circuit, 41 to 44 are AND gates, and 45 is an input terminal.

Photodetector 14 is two photodiode 14b disposed four divided photodiode 14a comprising four photodiode 14a ₁ to 14A ₄ and on both sides thereof, and is composed of a 14c, is divided into four photo-diodes 14a The main light beam reflected from the optical information carrier is received, the photodiode 14b receives the sub light beam (+ 1st-order diffracted light), and the photodiode 14c receives the sub light beam (-1st-order diffracted light). The spot of the main light beam generated on the four-division photodiode 14a is the same as the main light beam passing through the converging lens 12 and the cylindrical lens 13 (FIG. 6 (a)). 18 (FIG. 6), the photodiodes 14a ₁ and 14a are not in the focusing position.
₄ and the linear direction connecting the photodiodes 14a ₂ and 14a ₃ are each formed into an elliptical shape whose axial direction is the axial direction. The ratio of the two axes of the ellipse is from the optical information carrier 18 to the focusing lens 8. It changes according to the distance of.

Then, the operational amplifier 19 controls the focus lens 8 by subtracting the sum of the output signals of the photodiodes 14a ₁ and 14a ₄ from the sum of the output signals of the photodiodes 14a ₂ and 14a ₃ in the four-division photodiode 14a. To obtain a focusing information signal e.

Secondary light beam of the photodiode 14b (+ 1st-order diffracted light)
The output signal having a level corresponding to the light amount is amplified by the amplifier 28 and then supplied to the differential amplifier 29 and the waveform equalization circuit 31. An output signal having a level corresponding to the light amount of the sub-light beam (-1st-order diffracted light) of the photodiode 14c is output to the amplifier 27.
After that, it is supplied to the differential amplifier 29 and the waveform equalization circuit 30. In the differential amplifier 29, the output signal of the amplifier 27 is subtracted from the output signal of the amplifier 28, and a signal c having a level proportional to the light amount difference between the two sub-light beams is obtained. The output signal c of the differential amplifier 29 is mainly in an area (non-ROM area) of the optical information carrier 18 (FIG. 6A) where no prepits are present.
This is tracking information when scanning is performed by the sub light beam.

As described above, the primary and secondary light beams are
When the area (ROM area) where the pre-pits exist on 18 is scanned, the main and sub-light beams reflected therefrom are modulated according to the density of the pre-pits, and the light quantity fluctuates. As a result, the output signals of the amplifiers 27 and 28 include AC components having a frequency corresponding to the density of the pre-pits, and the amplitudes of these AC components are also affected. Waveform equalizing circuits 30 and 31 compensate for amplitude fluctuations of the AC component due to the density of the pre-pits on the output signals of the amplifiers 27 and 28, and the amplitudes of these AC components correspond to the position of the auxiliary light beam in the track width direction. So that

The output signal of the waveform equalization circuit 30 is detected by an upper envelope detection circuit 32 to generate a signal (upper envelope signal) a representing the upper envelope of the AC component, and the lower envelope detection circuit 34 A signal (lower envelope signal) b that is detected and represents the lower envelope of the AC component is generated. Similarly, the output signal of the waveform equalization circuit 31 is supplied to the upper envelope detection circuit 33 and the lower envelope detection circuit 35, and the upper envelope signal a 'and the lower envelope detection signal b for the AC component are supplied. 'Is generated. In the operational amplifier 36, the arithmetic processing of (ab)-(a'-b ') is performed. Here, (ab) is the difference between the upper envelope signal a and the lower envelope signal b, and is the waveform equalization circuit 30.
Represents the amplitude of the AC component in the output signal of (a′−
Similarly, b ′) represents the amplitude of the AC component in the output signal of the waveform equalization circuit 31. Accordingly, the signal d output from the operational amplifier 36 is the difference between the amplitudes of the AC components in the output signals of the waveform equalizing circuits 30 and 31, that is, the area where the main and sub-light beams are present on the optical information carrier 18 where the prepit exists. Represents the tracking information when scanning is performed.

The switch 37 is controlled by a control signal j from an input terminal 45. When the main and sub light beams scan an area without pre-pit on the optical information carrier 18, the switch 37 is closed to the A side and the output signal c of the differential amplifier 29 is closed. Is selected as the tracking information signal i, and when the main and sub-light beams scan the area where the prepits are present on the optical information carrier 18, it is closed to the B side and the output signal d of the operational amplifier 36 is selected as the tracking information signal i. I do. The tracking control of the main light beam is performed by the tracking information signal i.

In this manner, good tracking control can be performed in an area where the optical information carrier 18 has no pre-pits or in an area where the pre-pits exist, and the optical information carrier that does not form the pre-pit and the optical information carrier that provides the pre-pit can be controlled. However, good tracking control is possible.

Further, since the photodiodes 14b and 14c need only completely receive the sub-light beam reflected from the optical information carrier,
The assembling accuracy of the optical system such as the arrangement of the photodiodes 14b and 14c is eased, so that the optical system can be configured at low cost, and the accuracy of the optical information carrier can be eased.

 Next, other parts of FIG. 7 will be described.

Each photodiode 14a of the four-divided photodiode 14a
The output signals _{1 to} 14a ₄ are added by the operational amplifier 20, and a signal having a level proportional to the amount of the main light beam received by the four-division photodiode 14a is obtained. On the one hand, the output signal of the operational amplifier 20 is supplied to the switch 26 after the modulation component due to the pre-pit is removed by the LPF 21, and the output signal of the operational amplifier 20 is supplied to the switch 26 by the waveform equalization circuit 22 having the same function as the waveform equalization circuits 30 and 31. After the amplitude fluctuations due to the component pre-pits are compensated, the upper envelope detection circuit 23, the lower envelope detection circuit 24 and the differential amplifier 25
As a result, a signal representing the amplitude of the AC component is generated and supplied to the switch 26.

Here, when the main light beam scans an area without prepits on the optical information carrier 18, the output signal of the LPF 21 becomes four.
The light receiving amount of the main light beam received by the divided photodiode 14a represents the amount of light received. When the main light beam scans the area where the pre-pit exists on the optical information carrier 18, the output signal of the differential amplifier 25 receives the main light beam. Express the amount.

The switch 26 is controlled by a control signal j from an input terminal 45. When the main light beam scans an area on the optical information carrier 18 where there is no pre-pit, the switch 26 is closed to the A side and the output signal of the LPF 21 is changed to the main light beam. When the main light beam scans an area on the optical information carrier 18 where the pre-pits are present, it is closed to the B side and the output signal of the differential amplifier 25 is selected as the light quantity signal f.

When the optical information carrier 18 is mounted on the optical information recording / reproducing apparatus and the optical information carrier 18 is started, the focus lens 8 shown in FIG. 6A is lifted from below and approaches the optical information carrier 18. As the spot of the main light beam on 14a becomes smaller, the level of the light quantity signal f rises. When the level of the optical signal f exceeds a preset threshold, focusing control based on the focusing information signal e starts. In this way, the focusing servo circuit can be quickly pulled in at the time of startup.

The level of the tracking information signal i obtained by the switch 37 is compared with 0 potential by the level comparing circuit 39, and a rectangular wave signal k which rises and falls alternately at successive zero cross points of the tracking information signal i is generated. This rectangular wave signal k is supplied to the AND gate 41, and the level is inverted and supplied to the AND gate 42. Further, this rectangular wave signal k is slightly delayed by the delay circuit 40, then level-inverted and supplied to the AND gate 41,
The signal is supplied to the AND gate 42. Accordingly, a rising edge pulse m having a time width equal to the delay time of the delay circuit 40 is obtained from the AND gate 41 at the rising edge of the rectangular wave signal k, and a falling edge pulse n is also obtained from the AND gate 42. .

On the other hand, the light quantity signal f obtained by the switch 26 is compared with the reference voltage V1 by the level comparing circuit 38, and the gate signal p
Is formed. This gate signal p is supplied to AND gates 43 and 44.
Supplied to The AND gates 43 and 44 are turned on when the light quantity signal f is at a level equal to or higher than the reference voltage V1, and pass the rising edge pulse m and the falling edge pulse n to become the track crossing signals g and h.

These track traversing signals g and h are alternately generated at the zero cross timing of the tracking information signal i when the main light beam moves across the track on the optical information carrier 18. However, the zero cross point of the tracking information signal i occurs when the center of the main light beam is on the center line of the track and when the center of the guide groove between the tracks is on, and one of the crossing signals g and h is mainly used. If the center of the light beam is on the track center line, the other will occur when the center of the main light beam is at the center of the guide groove, and
The track crossing signal generated when the center of the main light beam is on the track center line differs depending on the moving direction of the main light beam.

To determine this, AND gates 43 and 44 controlled by a gate signal p output from the level comparison circuit 38 are provided. That is, the gate signal p is always "H" when the center of the main light beam is on the track center line.
(High level) and the AND gates 43 and 44 are turned on.
Therefore, if the rising edge pulse m is generated when the center of the main light beam is on the track center line, the rising edge pulse m passes through the AND gate 48 to obtain a track crossing signal g, and conversely, the falling edge pulse m If n occurs when the center of the main light beam is on the track center line, the falling edge pulse n passes through the AND gate 44 to obtain a track crossing signal h.

By counting the track traversing signal g or h, the number of tracks that the main light beam has traversed can be detected, whereby the position and speed at the time of the track seek can be detected.

[Problems to be Solved by the Invention] According to the above-mentioned technology, the main light beam is also transmitted to a predetermined track after the seek even when the optical pickup is transferred in the radial direction of the magneto-optical disk by the course actuator. When pulling in the tracking to set the position,
The tracking information i obtained from the sub-light beam output from the switch 37 in FIG. 7 is used. according to this,
The following problems arise.

The problem is the switching timing of the switch 37 when the ROM area and the non-ROM area are mixed. When trying to start tracking, that is, at the time of tracking pull-in, if the light beam irradiation part is near the boundary between the ROM area and the non-ROM area, pull-in may not be performed normally. Also, as described above, when the tracking error signal is counted to obtain the number of tracks moved, when the optical head is moved in the radial direction of the magneto-optical disk, that is, when the seek operation is performed, the ROM area,
There is a problem that a mistake is made in counting the number of tracks while the switch 37 is switched after judging that the non-ROM area has entered from one side to the other.

Further, in the above-described technique, a force in the disk radial direction is applied to the fine actuator due to acceleration and deceleration of the course actuator when performing an access operation, and even after the seek operation by the course actuator is completed. Residual vibration remains in the Ein actuator. Since the tracking following operation is performed after a lapse of time for these vibrations to attenuate, the above decay time must be added to the access time in addition to the seek time by the course actuator and the tracking pull-in time to start the following operation. And the access time becomes longer. With a two-dimensional shaft-sliding actuator, a couple should not occur and a lens should not be displaced by nature, but it is difficult to achieve perfect balance. Other types of fine actuators, such as spring-supported two-dimensional actuators and galvanomirrors, apply a larger inertial force, and therefore have a large amount of vibration.

Further, in order to suppress the residual vibration, an attempt has been made to detect a displacement amount of the fine actuator by newly providing a detector. However, if a position sensor for detecting the position of the lens is provided, an increase in weight and imbalance, an increase in cost due to the addition of machining, and an increase in adjustment work such as calibration of the optical axis movement amount and the sensor output are caused. There was.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information recording / reproducing apparatus which solves such a problem and enables quick access and tracking pull-in.

Means for Solving the Problems In order to achieve the above object, the present invention provides a three-spot system which uses a main light beam and two sub light beams to obtain tracking information using a sub light beam. In such an optical information recording / reproducing apparatus, a tracking information signal is also obtained from a main light beam, tracking control is performed by a push-pull method using the main light beam at the time of seek or tracking pull-in, and the tracking control is performed at the time of track following. Tracking control by a three-beam method using a light beam is performed.

[Operation] In the push-pull method in which tracking information is obtained from the main light beam to perform tracking control, as described above, the push-pull method is affected by the inclination of the optical information carrier with respect to the optical axis, but is not affected by the pit in the ROM area. . For this reason, the tracking control by the three-beam method is performed at the time of tracking, but the seek operation and the tracking pull-in operation which are not affected by the pit in the ROM area are performed by performing the tracking control by the push-pull method at the time of seeking or tracking pull-in. Can be made.

In addition, tracking information based on the push-pull method can be used to measure the number of track traversals, which means that the number of times the main light beam actually crosses the track is measured, making it unnecessary to switch between the ROM area and non-ROM area. As a result, accurate measurement values can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention, wherein 46 is an operational amplifier, 47 is a switch, and 48 is an input terminal. Reference numerals are given and duplicate description is omitted.

In Figure 1, this embodiment, the optical information recording and reproducing apparatus shown in FIG. 7, an operational amplifier 46 for calculating an output signal of photodiode 14a ₁ to 14A ₄ constituting the 4 division photodiode 14a, the A switch 47 for selecting one of the output signal q of the operational amplifier 46 and the tracking information signal i output from the switch 37 is added.
The output signal q of the operational amplifier 46 is supplied to the level comparison circuit 39.

 The optical system has the configuration shown in FIG.

As described above with reference to FIG. 7, the main light beam reflected from the optical information carrier 18 (FIG. 6) is incident on the four-division photodiode 14a. It consists of 0th-order diffracted light and ± 1st-order diffracted light by the guide grooves on both sides of the upper track and the pits in the ROM area. These ± 1st-order diffracted lights are irradiated up and down on the drawing with respect to the center of the 0th-order diffracted light. That is, the + 1-order diffracted light is irradiated to the photodiode 14a _1, 14a ₂ side, -1 order diffracted light is irradiated to photo-diodes 14a _3, 14a ₄ side.

Here, when the main light beam is correctly tracked so that its center coincides with the center line of the track, the total received light amount of the photodiodes 14a ₁ and 14a _{3 and} the total received light amount of the photodiodes 14a ₂ and 14a ₄ If the main light beam deviates from the correct tracking state, the total amount of received light will differ.

Therefore, the operational amplifier 46 is connected to the photodiodes 14a _{1 to} 14a ₄
Is calculated as shown in the figure, and the difference between the total received light amounts is obtained. The output signal q of the operational amplifier 19 thus obtained represents tracking information.

The tracking information signal q is supplied to the switch 47 together with the tracking information signal i from the switch 37.
The switch 47 is controlled by a control signal r from an input terminal 48, and selects a tracking information signal q at the time of seeking or tracking pull-in, and a tracking information signal i at the time of tracking follow-up, and a tracking information signal s (not shown). Supply to King servo circuit.

Further, the tracking information signal q is supplied to the level comparison circuit 39, and based on this, the track crossing signals g and h are generated.

In this manner, in this embodiment, the tracking information signal is obtained by the so-called push-pull method using the main light beam, and this is used for the tracking servo at the time of seeking or at the time of tracking pull-in. effects do not appear, in particular, at the time of tracking pull-in, also in the ROM area, photodiode 14a ₁ to 1
Since the output signals of 4a ₄ are in-phase, the tracking is not affected by the pits and the tracking can be quickly performed.

Also, at the time of seek, the track crossing signals g and h are generated from a single main light beam, so that the number of track crossings can be easily and accurately counted, and the position and seek speed of the light beam can be obtained accurately. .

FIG. 2 is a main block diagram showing another embodiment of the optical information recording / reproducing apparatus according to the present invention, wherein 49 is a two-part photodiode, 49a and 49b are photodiodes, 50 to 52 are operational amplifiers, Parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

In this figure, here, the P-polarized component (or the S-polarized component) of the main light beam enters the four-divided photodiode 14a of the photodetector 14, and the main light beam enters the separately provided two-divided photodiode 49. S-polarized component (or P
Polarization component) is incident. Accordingly, in the optical system of this embodiment, the P-polarized component (or the S-polarized component) is configured to be incident on the photodetector 14 in FIG. A two-division photodiode 49 shown in FIG. 2 is provided, and the S-polarized component (or the P-polarized component) of the main light beam is made incident thereon.

Similar to the embodiment shown in FIG. 1, by subtracting the sum of the output signal of photodiode 14a _1, 14a ₄ in operation amplifier 19 from the sum of the output signal of photodiode 14a ₂ to 14A _3,
A focus information signal e is obtained. The operational amplifier 20
In by adding the output signal of photodiode 14a ₁ to 14A _4, the level of the signal t corresponding to the amount of the P polarized light component of the main light beam (or S-polarized light component) is obtained. Photodiodes 49a and 49b in two-division photodiode 49
Are added by the operational amplifier 50, and the S signal of the main light beam is
A signal u having a level corresponding to the amount of the polarized light component (or the P-polarized light component) is obtained. In the operational amplifier 51, the operational amplifier 50
The output signal t of the operational amplifier 20 is subtracted from the output signal u of the above, whereby the data signal v recorded on the optical information carrier is obtained from the operational amplifier 51.

On the split photodiode 49, the position of the spot of the reflected main light beam changes in the directions of arrows A and A 'according to the irradiation position of the main light beam on the track on the optical information carrier. Therefore, depending on the tracking state of the main light beam with respect to the track, the photodiode 49a,
The light receiving amount of 49b changes, and the levels of these output signals change. Therefore, the output signals of the photodiodes 49a and 49b are subjected to subtraction processing by the operational amplifier 52, whereby a tracking information signal w by the push-pull method is obtained.

The other structure is the same as that of the embodiment shown in FIG. 1. By using this tracking information signal w instead of the tracking information signal q in FIG.
The same effect as the embodiment shown in FIG. 1 can be obtained.

By the way, as described above, at the time of seek, acceleration and deceleration of the course actuator causes vibration in the disk radial direction in the fine actuator. That is, at the time of seeking, as shown in FIG. 3 (a), the optical pickup is first accelerated by the course actuator, then reaches a constant speed, and then approaches the desired track and is decelerated. In this operation, the lens during optical pickup is displaced in the opposite direction on the disk radius between the time of acceleration and the time of deceleration of the optical pickup as shown by the curve in FIG. , The lens will vibrate.

To prevent this, the displacement of the lens due to the seek operation can be suppressed by detecting the displacement of the lens shown in FIG. 3 (c) and applying the tracking servo accordingly. If it is attempted to use the tracking information signals q and w shown in FIGS. 1 and 2 to detect this displacement amount, these will be shown in FIG. 3 (c) as shown in FIG. 3 (b). A signal in which a sinusoidal periodic signal due to traversing the guide groove is superimposed on the signal representing the indicated lens displacement amount.

FIG. 4 is a specific example of a means for detecting a signal (lens displacement amount signal) representing the lens displacement amount shown in FIG. 3 (c) from the tracking information signals q and w in FIGS. 1 and 2. 53 is an LPF (low-pass filter), 54 is a speed detector, 55 is a voltage comparator, and 56 is a switch.

For example, a tracking information signal q as shown in FIG. 3 (b) obtained by the operational amplifier 46 of FIG. 1 is supplied to the LPF 53, and a periodic signal due to crossing the guide groove is removed. LP
The output signal of F53 becomes the lens displacement amount signal x via the switch 56.

By the way, when the moving speed of the optical pickup by the course actuator is low, the frequency of the periodic signal due to the crossing of the guide groove is low, and the LPF 53 cannot sufficiently remove the frequency. For this reason, an error occurs in the lens displacement amount signal x. In such a case, the lens displacement amount is small. Therefore, when tracking servo is applied with a lens displacement signal x having an error, the lens displacement may increase instead.

In order to prevent this, in FIG.
The seek speed is detected by the speed detector 54 from the track crossing signal g in the drawing, and the output signal of the speed detector 54 is compared with a preset reference voltage V2 by the voltage comparator 55 to thereby seek. A period in which the speed is equal to or higher than a predetermined speed is detected. The output signal of the voltage comparator 55 is a signal representing this period, and controls the switch 56 accordingly. The switch 56 is turned on during this period. Accordingly, a lens displacement signal x when the seek speed is equal to or higher than a predetermined speed is obtained from the switch 56.

In the embodiment shown in FIGS. 1 and 2, by performing tracking servo with the lens displacement amount signal x during the seek operation, the vibration of the lens at the end of the seek operation can be eliminated.

As the speed detector 54, an arbitrary device such as a frequency-voltage conversion circuit or digital counting of the cycle of the track crossing signal g can be used.

[Effects of the Invention] As described above, according to the present invention, in a three-spot optical information recording / reproducing apparatus, a ROM area, a non-R
The pull-in operation for the track where the OM area exists is stabilized, the vibration of the lens due to the seek operation is suppressed, the tracking can be quickly performed, and the access time can be reduced with a light-weight and low-cost optical head.

In addition, the number of traversing tracks during the seek is accurately measured, and the irradiation position of the light beam and the seek speed can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing a main part of another embodiment of the optical information recording / reproducing apparatus according to the present invention, and FIG. FIG. 4 is a block diagram showing a specific example of a means for extracting a lens displacement signal from a tracking information signal, and FIG. 5 is a block diagram showing a three-beam system. FIG. 6 is an explanatory diagram showing the effect of pre-pits upon detection of tracking information, FIG. 6 is a diagram showing an optical system of an optical information recording / reproducing apparatus previously proposed by the present applicant, etc., and FIG. FIG. 1 ...... laser diode, 3 ...... diffraction grating, 9 ...... focus lens 5, 14, 15 ...... photodetector, 14a ...... 4 division photodiode, 14a ₁ to 14A _4, 14b, 14c ...... photodiode, 18 optical information carrier, 20 operational amplifier, 29 differential amplifier, 36 operational amplifier, 37 switch, 46
Operational amplifier, 47: Switch, 49: 2-division photodiode, 49a, 49b: Photodiode, 50 to 52: Operational amplifier.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichiro Inuchi 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-1-50243 (JP, A) JP-A-1 -50244 (JP, A) JP-A-3-71439 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/085 G11B 7/09 G11B 7/095

Claims (3)

(57) [Claims] A guide groove for tracking is provided,
A main light beam for recording information on or reproducing information from a disc in which a ROM area in which prepits are formed and a non-ROM area in which no prepits are formed; and 1 so that it is placed separately on the left and right
Irradiating means for irradiating the disk with a pair of auxiliary light beams; and photoelectric conversion means for receiving reflected light of the main light beam and the auxiliary light beam from the disk and converting each of the reflected light to an electric signal. In the optical information recording / reproducing apparatus, the tracking control by the push-pull method using the main light beam is performed at the time of seeking or tracking pull-in, and the tracking control by the three-beam method using the sub light beam at the time of track following. Characteristic optical information recording / reproducing device. 2. The optical information according to claim 1, wherein the push-pull signal obtained by using the main light beam is used for counting the number of tracks during seek and / or detecting a seek speed. Recording and playback device. 3. The method according to claim 1, wherein a level change of a push-pull signal obtained by using said main light beam is detected during a seek and converted into a vibration amount of a fine actuator. An optical information recording / reproducing apparatus, characterized in that a servo for suppressing vibration of the fine actuator is applied by using the obtained fluctuation amount.