JPH0750020A - Optical information processor - Google Patents

Abstract

PURPOSE:To correct offset strictly by measuring the relationship between the position of an objective lens and the offset amount of a tracking error signal based on the tracking error signal and the output signal of a position detecting means. CONSTITUTION:The number of moving tracks is detected by counting tracking signal in movement with a linear motor with a track counting circuit 64. Two RF sensors 19 and 20 convert a magneto-optical signal and a pre-format signal into the electric signals. The signals are amplified with preamplifiers 52 and 53. Then, the signals undergo differential detection, same-phase detection and peak detection in an RF-signal processing circuit 69. The output is processed in a CPU 66. Then, the signal output passes an external interface circuit 67 and outputted into an external apparatus as the digital information. Meanwhile the envelope of the signal, which has undergone RF signal processing, is detected with a detection circuit 70 in the intact state of the analog signal. The signal is inputted into a digital-signal processing circuit 48 as the level signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information processing apparatus for recording / reproducing information on / from an optical disk or the like.

[0002]

2. Description of the Related Art In recent years, "digital signal processing method" for performing digital signal processing which has been conventionally performed by analog has become popular, and compact discs (CD), digital audio tapes (DAT), communication lines, etc. Has been put to practical use in a wide range of fields. This is because the "digital signal processing method" can realize a complicated signal processing algorithm by software, which simplifies the hardware and reduces the system cost, and allows flexibility in changing specifications such as selection of filter constants and algorithms. This is because it has merits such as being able to respond. In addition, because of the progress of IC technology, digital signal processing ICs and DSPs (digital signal processors) having high-speed arithmetic processing speeds have become available at low prices.

On the other hand, an optical information processing device such as an optical disk is
From a read-only type CD to a write-once type (DRAW) to a rewritable type magneto-optical disk, rapid progress has been made as a high density and large capacity memory. In particular, the magneto-optical disk is required as an external memory of a computer, in addition to the above-mentioned high density and large capacity, high reliability and high speed access.

For this reason, the electric servo system is also required to be controlled by complicatedly combining outputs from various sensors. An example of a conventional magneto-optical disk device will be described with reference to FIG.

In FIG. 16, the light beam emitted from the semiconductor laser 1 is made into a parallel light beam by the collimator lens 2, and is made into a light beam having a substantially circular cross section by the polarization beam splitter 3 with a beam shaping function. The parallel light beam is reflected by the prism 4
It is reflected by and is incident on the objective lens 5. Objective lens 5
Is movable in a focus direction 6 and a tracking direction 7 by an actuator (not shown) and focuses a minute light spot on the disk 9. Disk 9
A magneto-optical recording layer is formed, the direction of arrow 10 is the track direction, and the direction of arrow 11 is the center of rotation of the disk. The prism 4, the objective lens 5, the actuator, etc.
It is fixed to the carriage 13 and moves in the radial direction of the disk 9 using a linear motor (not shown) or the like.

The reflected light from the disk 9 is collimated again by the objective lens 5 and is bent by the prism 4,
Heading for the polarizing beam splitter 3. The light beam reflected by the polarization beam splitter 3 in the direction of the detection optical system passes through the condenser lens 15 and is reflected by the beam splitter 16 in the direction of the servo sensor 18, and the RF sensors 19, 20.
It is divided into light beams that are transmitted in the direction.

The condenser lens 15 includes, for example, an element that produces astigmatism, and the light flux is condensed on the servo sensor 18. The servo sensor 18 is a four-division sensor 18
-1 to 18-4. Then, while observing that the light spot is focused on a predetermined track on the disk 9, the servo sensor 18 is positioned in the three-axis directions and adjusted so that equal outputs are generated from the four sensors. There is.

The luminous flux transmitted through the beam splitter 16 is
The beam is split into two by the polarization beam splitter 17, and is focused on the radio / flexibility (RF) sensor 19 and the RF sensor 20, respectively. The semiconductor laser 1, the collimator lens 2, the RF sensor and the like are all fixed to the head fixing portion 14.

The example of the optical disk device shown in FIG. 16 is a so-called separation optical system in which a carriage 13 and a head fixing portion 14 are separated from each other, which enables high speed access.

The actuator section of the conventional magneto-optical disk device will be described with reference to FIG.

In FIG. 17, 5 is an objective lens,
It is fixed to the bobbin 21. Reference numerals 22 and 23 are a tracking coil and a focusing coil, respectively.
The bobbin 21 is driven in the tracking direction 7 and the focus direction 6 in cooperation with the tracking magnet 24 and the focusing magnet 25 fixed to the position 6. 27 is
The support shaft of the bobbin 21 and 28 are under limiters for determining the lowermost end of the bobbin. A counterweight 29 of the objective lens 5 is fixed to the bobbin.

Reference numeral 30 is a light emitting diode, and 31 is
This is a flex for the light emitting diode 30. The light flux emitted from the light emitting diode 30 passes through the slit 32, is shaped, and is projected on the two-divided sensor 34 as a light flux 33. The light emitting diode 30 is fixed to 21, and when the actuator is displaced in the tracking direction, the light receiving surface 34-1 of each of the two split sensors of the light flux 33,
Since the amount of light incident on 34-2 changes, the position of the objective lens 5 can be detected by calculating these outputs. Reference numeral 35 is a flexure for the two-divided sensor 34.

The linear motor portion of the conventional magneto-optical disk device will be described with reference to FIG.

In FIG. 18, 5 is an objective lens, 21 is a bobbin, 24 is a magnet, 26 is a yoke, and 27 is a bobbin supporting shaft, which are fixed to the carriage 13 as actuators. The carriage 13 is supported by rails 36-1 and 36-2 by bearings 37-1 and 37-2 and is movable in the disk radial direction 12, and the linear motor unit includes a coil 38, a yoke 39, a magnet 40. -1, 40-2, etc., and drives the carriage 13 in the disk radial direction. In this example, linear motors are attached to both sides of the carriage to enable high speed access. Reference numeral 41 is a spindle motor for rotating the disk.

The servo system of the magneto-optical disk device described with reference to FIGS. 16 to 18 will be described with reference to FIG.

In the servo sensor 18, when the objective lens 5 is at the center of the light beam from the semiconductor laser 1 and the light beam is condensed by the objective lens 5 on the track of the disk 9 as a minute spot of about 1 micron. The four sensors 18-1 to 18-4 are adjusted so as to generate equal outputs. In this example, since the astigmatism method is used as the focus error detection method, 18-1 to 18-4 are used.
When the outputs from the respective sensors are S _{1 to} S ₄ , respectively, the difference in the output of the diagonal sum is observed according to the focus shift between the disc and the spot, and the following focus error signal S _AF is obtained.

S _AF = (S ₁ + S ₃ )-(S ₂ + S ₄ ) For example, when the light spot is focused on the disc, the above output is 0, when the disc is close, it is negative, and when it is far, it is positive output. To get

The push-pull method is used as the tracking error detection method. The push-pull method is a method of observing the balance of the diffracted light from the guide groove of the disc in the far field, and the distribution of the diffracted light is determined according to the radial displacement of a given track on the disc and the light spot. Is unbalanced, the difference in the outputs of the sensors divided by the tangential dividing line of the sensor 18 is observed, and the following tracking error signal S _AT
Is obtained.

S _AT = (S ₂ + S ₃ )-(S ₁ + S ₄ ) For example, if the light spot is on a track, the above output is 0, if it is shifted in the inner circumferential direction of the disc, it is negative, and if it is shifted in the outer circumferential direction of the disc. If you get a positive output.

In the push-pull method, when the objective lens 5 largely shifts in the radial direction (tracking direction) due to a multi-track jump or the like, the light beam focused on the servo sensor 18 moves in the radial direction. In addition to the unbalance of the diffracted light distribution depending on the track deviation, an offset occurs in the auto tracking (hereinafter referred to as AT) output. In order to perform high-speed access, it is advantageous that the objective lens can be moved about 100 to 150 tracks from the center of the light flux from the semiconductor laser 1. Since this offset is almost proportional to the amount of deviation from the center of the light beam of the objective lens, it can be easily corrected if the position of the objective lens can be detected.

Therefore, in this example, the objective lens position detecting means (hereinafter referred to as a lens position sensor) as described with reference to FIG. 17 is provided. The outputs from the two sensors 34-1 and 34-2 arranged in the radial direction are respectively S _LP1 ,
As S _LP2 , when the objective lens is at the center of the light beam, the following lens position (hereinafter referred to as LP) output S _LP is adjusted to 0.

S _LP = S _LP1 −S _LP2 For example, if the objective lens 5 is located at the center of the light beam, the above output is 0, positive when it is displaced in the inner peripheral direction of the disc, and negative when it is displaced in the outer peripheral direction of the disc. Get the output of.

Further, since the output of the lens position sensor represents the positional deviation between the carriage 13 and the objective lens 5, if the linear motor is driven using this, the objective lens position can always be kept at the center of the light beam.

Although the servo sensors and the like have been described above, they cannot be perfectly aligned mechanically. Therefore, when performing conventional analog servo signal processing, the sensor output after the mechanical adjustment is performed. It is usual to provide an adjusting volume (not shown) or the like on the to make electrical adjustment.

Next, the servo signal processing will be briefly described.

Outputs S _{1 to} S ₄ from the servo sensor 18
Is amplified by the preamplifier 43, and then taken out by the arithmetic circuit 44 as AT and auto focus (hereinafter referred to as AF) output as described above. Lens position sensor 34
The outputs S _LP1 and S _{LP2 from} are amplified by the preamplifier 45 and then taken out by the arithmetic circuit 46 as lens position outputs. Among these, the AT output and the LP output are added by the adder circuit 47, and are corrected so that no offset is generated in the tracking error signal even if the objective lens position is displaced (post-correction AT output). The AF output, the corrected AT output, and the LP output are respectively captured by the servo signal processing circuit 48 and output to the AF driver 49, AT driver 50, and linear motor driver 51 at appropriate timings. The drive signals from the respective drivers are the AF coil 23, the AT coil 22,
Output to the linear motor coil 38, focus control,
Tracking control is performed.

Next, the RF system will be described with reference to FIG.

In FIG. 20, 19 and 20 are the above-mentioned RF sensor and RF sensor, respectively. Reference numerals 52 and 53 are preamplifiers that amplify the outputs from the RF sensors 19 and 20, respectively. 54 and 55 are RF sensors 19 and 20, respectively.
Is an amplifier that differentially adds the outputs of. In the magneto-optical signal output 56, the rotation of the polarization plane of the light flux due to the magneto-optical effect is detected by the beam splitter 17 and detected as the difference between the outputs of the RF sensors 19 and 20. Further, the preformatted signal 57 such as a sector mark or an address causes a uniform increase / decrease in the amount of light incident on the RF sensors A and B, and is therefore detected as the sum of the outputs of the RF sensors 19 and 20.

A conventional magneto-optical disk will be described with reference to FIG.

In FIG. 21, 11 is the center of the disk, and is provided with a track 58 and a guide groove (groove) 59 in a spiral shape. Preformatted signals such as sector marks and addresses are used for pits 60
Is divided into a header part which is preformed in the form of 1 and a data part in which the user records information as a magneto-optical signal in the form of magneto-optical pits 61.

[0031]

In the magneto-optical disk device having the above-described structure, it is impossible to mechanically perfectly align the servo sensor and the like. It was difficult to reduce the cost because the electric power supply was installed and the electric adjustment was made.

Further, since the above-mentioned focus or tracking error detection method does not directly detect the condensed state of the light spot on the disk, the relative position of the servo sensor and the light spot on the servo sensor, or If the position of the semiconductor laser is displaced due to some external force after adjustment, the light spot will not be correctly focused on a predetermined track on the disk. Changes in these states can often occur due to changes in temperature, vibration during transportation, etc., and reduce servo accuracy. Or
Even if there is no displacement in the servo sensor itself, the wavelength of the semiconductor laser changes due to temperature changes, and the deflection angle of the light beam at the polarization beam splitter with a beam shaping function changes.
In some cases, the light spot position on the servo sensor may move.

Also, in multi-track jump, etc.,
Since the AT offset that occurs when the objective lens is used at a position displaced in the radial direction changes due to variations in the depth of the guide groove of the disc, etc., unless the offset value is adjusted for each disc, tracking accuracy is degraded. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical information processing apparatus which does not require a complicated adjustment process and can rigorously correct an offset of a tracking error signal. And

[0035]

The above object of the present invention is to provide an optical head for irradiating an optical recording medium on which a track is formed with a light beam, and to mount the light beam on the track and focus the light beam on the track. An objective lens, a photodetector for detecting light reflected or transmitted by the medium of the light beam, and means for generating a tracking error signal representing the positional deviation between the irradiation position of the light beam and the track from the output of the photodetector. A tracking actuator for moving the objective lens in a direction traversing the track; tracking control means for driving the tracking actuator according to the tracking error signal to correct the positional deviation; and a track of the objective lens with respect to the optical head. And a position detecting means for detecting a relative position in a direction crossing the optical recording medium. And / or in an optical information processing device for reproduction, means for measuring the relationship between the position of the objective lens and the offset amount of the tracking error signal from the tracking error signal and the output signal of the position detecting means, and the measured Achieved by providing storage means for storing the relationship, and means for obtaining an offset amount from the output signal of the position detection means based on the relation stored in the storage means, and correcting the tracking error signal by the obtained offset amount. To be done.

[0036]

1 is a block diagram showing an embodiment of a control circuit used in an optical information processing apparatus of the present invention. Here, the servo sensor 18, the preamplifier 43, and the arithmetic circuit 44 are connected as shown, and are connected to the digital signal processing circuit 48 via the input switching circuit 62 and the analog / digital A / D) converter 63. The arithmetic circuit 44 is also connected to the track count circuit 64. This output is connected to the digital signal processing circuit 48. Lens position sensor 3
4 is connected to the input switching circuit 62 via the preamplifier 45. The output of the home position sensor 65 is connected to the digital signal processing circuit 48, and the central processing unit (CPU) 66 is bidirectionally connected to the digital signal processing circuit 48 and the external interface circuit 67. The spindle motor 42 for rotating the disk is connected to the digital signal processing circuit 48 via a motor driver 68. The two RF sensors 19 and 20 are connected to the RF signal processing circuit 69 via the preamplifiers 52 and 53, and one output is connected to the input switching circuit 62 via the detection circuit 70 and the other is digital. The signal is input to the signal processing circuit 48. The memory 71 for storing various data is connected to the digital signal processing circuit 48.
From the digital signal processing circuit 48, the D / A converter 72,
Four sample and hold (S
/ H) circuit 74, 75, 76, 77, and driver 7
The laser diode 1, the focus coil (AF coil) 23, the tracking coil (AT coil) 22, and the linear motor coil 38 are connected via 8, 49, 50, and 51, respectively. A monitor photodiode 79 that monitors the light emitted from the laser diode is connected to the input switching circuit 62 via a preamplifier 80. Also,
The temperature sensor 81 for detecting the temperature inside the machine is the input switching circuit 6
Connected to 2.

Next, the basic operation of the circuit shown in FIG. 1 will be described.

The light beam incident on the servo sensor 18 is converted into a voltage signal by the preamplifier 43, and then arithmetically processed into a focus error signal, a tracking error signal, and a focus tracking sum signal by the arithmetic circuit 44. One of these signals is selected by the input switching circuit 62 and then A / D
It is converted into a digital signal by the converter 63 and input to the digital signal processing circuit 48. Digital signal processing circuit 4
Reference numeral 8 outputs a digital control value to the D / A converter 72 so as to control the AT coil and the AF coil so that the tracking error level and the focus error level become zero. The analog control signal is selected by the output switching circuit 73, held by the S / H circuits 75 and 76, respectively, and then output to the drive circuits 49 and 50. The driver drives the AF coil 23 and the AT coil 22, respectively.

On the other hand, in order to read and write the magneto-optical signal, it is necessary to irradiate the disk with laser light, but the digital signal processing circuit 48 sets the laser light control value to D /
Output to the A converter 72. The analog signal passes through the S / H circuit 74 after being selected by the output switch 73,
It is input to the laser driver 78. The laser driver controls the laser diode 1 so that the amount of light necessary for reading and writing can be obtained. A monitor photodiode 79 for monitoring the emitted light is attached to the laser diode, and its output is input through the preamplifier 80 to the input switching circuit 6
Entered in 2. By monitoring the light amount with the monitor photodiode 79, the digital signal processing circuit 48 can accurately control the laser emission light amount. The signal line directly connected to the laser driver 78 from the digital signal processing circuit 48 is a laser ON / OFF signal line at the time of writing.

The lens position sensor 34 is composed of a two-divided photodiode and is illuminated by the lens position sensor light emitting diode (LED) 30. The output of the photodiode changes due to the change in the position of the objective lens. This output is amplified by the preamplifier 45, then input to the input switching circuit 62, passes through the A / D converter 63, and is input to the digital signal processing circuit 48. Is entered. The output of the home position sensor 65, which detects that the actuator has moved to the home position on the outer peripheral side, is input to the digital signal processing circuit 48.

The CPU 66 for managing the overall sequence operation in the present invention is connected to the digital signal processing circuit 48 and controls the operation thereof, and is also connected to the external interface circuit 67 to manage the exchange of data with external equipment. ing.

The memory 71 is a digital signal processing circuit 48.
Alternatively, various data sent from the CPU 66 via it is stored.

The spindle motor 42 is a motor driver 6
The rotation is controlled by 8, and its start and stop are controlled by the CPU 66 through the digital signal processing circuit 48.

The linear motor coil 38 is driven via the driver 51 by the speed command from the digital signal processing circuit 48. When the linear motor is activated, the tracking error signal of the arithmetic circuit 44 appears as a track crossing signal. The number of moving tracks can be detected by counting the tracking signal during the movement of the linear motor by the track counting circuit 64. The digital signal processing circuit 48 calculates a target moving speed and the like from the target track number and the current track number.

The two RF sensors 19 and 20 convert the magneto-optical signal and the preformatted signal into electric signals. This signal is amplified by the preamplifiers 52 and 53 and then subjected to differential detection, in-phase detection and peak detection processing by the RF signal processing circuit 69. This output is sent as digital data through the digital signal processing circuit 48, is processed by the CPU 66, is passed through the external interface circuit 67, and is output as digital information to an external device. On the other hand, an envelope of the RF signal-processed signal is detected by the detection circuit 70 as it is as an analog signal, and the signal of the magnitude level is sent to the digital signal processing circuit 48 via the input switching circuit 62 and the A / D converter 63. Is entered. This is used when judging the magnitude of the RF signal level to detect whether focus and tracking are operating properly.

FIG. 2 shows a procedure of automatic adjustment of the servo system in the apparatus of the present invention.

First, the objective lens is first placed at the center of the light beam from the semiconductor laser, the AF servo is applied only, and the offset value of the tracking error signal is measured and corrected. (Step 1) Examples of the offset corrected at this time include a positioning error during adjustment of the servo sensor, a positional deviation after the adjustment, and a warp of the disk.

Next, calibration of the objective lens position sensor and offset correction of the tracking error signal when the objective lens deviates from the center of the light beam are performed. (Step 2) These two can be performed simultaneously or individually. The objective lens position sensor is calibrated by counting the number of tracks on the disc to know the absolute position of the objective lens from the center of the light beam, and using this to calibrate the output of the objective lens position sensor. As a result, the linearity of the objective lens position sensor is corrected.

The offset correction of the tracking error signal when the objective lens is deviated from the center of the light beam is for correcting the linearity between the objective lens position and the offset value of the tracking error signal caused by the cause described in step 1. At the same time, the size of the offset due to the variation in the depth of the guide groove due to the disc is also corrected.

Next, offset correction of the focus error signal is performed. (Step 3) This may be performed by replacing the process of Step 2. The AF and AT servos are applied to determine the offset value so that the reproduction amplitude of the signal (sector mark, address signal, etc.) pre-formatted on the disk becomes maximum. As a result, it is possible to correct the AF offset due to the alignment error during adjustment of the servo sensor or the like, the positional deviation after adjustment, the thickness of the disc substrate, the variation in the refractive index, the variation in the guide groove of the disc, and the like.

Next, AF gain adjustment is performed. (Step 4) AF and AT servos are applied, an appropriate focus disturbance is applied from the digital signal processing circuit, the response thereto is measured, and a predetermined appropriate gain is adjusted. It is possible to simultaneously correct the initial and elapsed variations of the actuator and the variations of the disk.

The AT gain is adjusted in the same manner as in step 4. (Step 5) Next, the gain of the linear motor is adjusted. (Step 6) AF and AT servos are applied to a predetermined track, an appropriate disturbance is applied to the linear motor from the digital signal processing circuit, and the response of the linear motor is measured using the output of the objective lens position sensor calibrated in step 2. Do it. It is possible to correct variations of the linear motor at the beginning and after the passage of time.

Finally, the linearity of the laser power monitor is corrected for the monitor photo diode incorporated in the semiconductor laser. (Step 7)
The output from the magneto-optical disk device is used by changing the laser power by about 10 times at the time of data reproduction and erasing / writing, so that the linearity of the monitor is poor due to the returning light from the disk. Therefore, this may be corrected by using the output of the servo sensor. As a result, recording / reproducing with the optimum laser power becomes possible.

The correction method in each of the above steps will be described in detail below.

Track at the objective lens reference position (on the optical axis)
Offset Correction Method for King Error Signal First, the carriage is moved to the home position so as not to erase the data already recorded at the time of correction. The movement to the home position is detected by a home position sensor 65 including a photo interrupter and a mechanical switch. Next, the objective lens is moved to the center position of the light beam from the semiconductor laser (hereinafter referred to as the lens reference position). As a method, the mechanical pin of the actuator is fitted at the midpoint when the focus actuator is lowered to the lowest point. You may choose to match
Adjustment is made at the time of manufacture so that the output of the preamplifier 45 of the lens position sensor 34 becomes a predetermined value at the lens reference position, and at the time of correction, the lens position sensor output is first set to the predetermined value. The lens position may be moved electrically.

In this state, the focus pull-in operation is carried out so that the focus becomes the focus point. Next, a tracking error signal when crossing a track is generated by the following method. As one of the methods, there is a method in which the linear motor coil 38 is energized to vibrate the linear motor while the lens is fixed at the reference point. If you vibrate the linear motor sinusoidally, the objective lens will vibrate to cross the track.
The tracking error signal ((S ₂ +
_{^{S 3) - (S 1 +}} S 4)) can be obtained. As a second method, a method of slightly oscillating the objective lens in the tracking direction at the reference position while keeping the linear motor fixed at the home position so as not to move may be used. In this way, a tracking error signal including an offset can be obtained near the lens reference position.

As shown in FIG. 3, the tracking error signal has an offset component. Although this signal is the tracking signal output from the arithmetic circuit 44 as described above, it is A / D converted by the sampling pulse shown in FIG. It is input to the circuit 48. The digital signal processing circuit 48 obtains the peak value and the bottom value of the waveform from the digitized tracking signal, and further obtains the midpoint of these values to recognize them as offset values. In order to obtain the peak value and the bottom value more accurately, it is desirable to capture the tracking error signal several times or more. The offset value obtained in this way is stored in the memory 71, but in the tracking operation after the completion of correction, the arithmetic circuit 44
The tracking offset value obtained here is subtracted from the digital tracking error signal before offset correction obtained via the D / D converter 63 to create a tracking error signal after offset correction, and this tracking error value after offset correction is calculated. It is used to control the tracking loop.

Calibration of the objective lens position sensor The output of the lens position sensor 34 has a characteristic that the two sensor outputs S _LP1 and S _LP2 change in opposite directions with respect to the displacement of the objective lens, as shown in FIG. Basically, by performing the calculation of (S _LP1 −S _LP2 ) / (S _LP1 + S _LP2 ), the in-phase variation such as the temperature variation of the sensor output can be removed and the objective lens position can be detected. . However, since S _LP1 and S _LP2 do not change linearly with the objective lens position, it is necessary to know the relationship between the sensor output and the objective lens position by the following method.

(First Method) With the objective lens position at the center of the light flux of the semiconductor laser, both focusing and tracking are brought into the retracted state and the disc is rotated. Since the disk has eccentricity, the tracking actuator sways in the tracking direction following the eccentricity, and the outputs S _LP1 and S _{LP2 of the} two lens position sensors 34 also fluctuate accordingly. As shown in FIG. 5, this fluctuating S _LP1 ,
S _LP2 is sampled by a rotation synchronization sampling pulse which is synchronized with the rotation of the disk, digitized by the A / D converter 63, passed through the digital signal processing circuit 48, and the eccentricity data during one rotation is stored in the memory 71. This data is used for removing the eccentric component in the data of the objective lens position described below.

Next, the tracking servo loop is opened, and the tracking actuator is moved within the objective lens movable range (for example, ± 250 microns = ± 170 tracks).
Only the track jump is performed, and during that time, the data of the relationship between the lens position sensor outputs S _LP1 and S _LP2 and the objective lens position displacement is read. While moving the objective lens position from -170 track to +170 track, the outputs of S _LP1 and LP2 are sampled every 10 tracks, and A /
Perform D conversion. The outputs of S _LP1 and S _LP2 fluctuate under the influence of eccentricity as shown in FIG. Here, the eccentricity data is used to extract the eccentricity, and the data from which the eccentricity is removed are stored in the memory 71.

(Second Method) In the first method, the position of the objective lens is continuously moved from −170 track to +170 track and the data is moved during the movement. Jump, close the tracking loop, and perform data retrieving. First, the procedure is the same as the first method until the objective lens position is brought to the optical center point and the tracking loop is turned on, but in the second method, decentering data restoration is not performed. Here, the objective lens position output S during one rotation or several rotations of the disk
_LP1 and S _LP2 are read, the outputs of S _LP1 and S _LP2 during that time are averaged by the digital signal processing circuit 48, and the objective lens position output from which the eccentric component is removed is obtained. Here, as shown in FIG. 7, a track jump is executed for a predetermined number of tracks, the tracking loop is closed at the objective lens position after the movement, and the objective lens position output is read during one or several revolutions to obtain an average value. Obtain the objective lens position output at that point. In this way, the track jump and the data return average value calculation are repeated, and the objective lens position output value from which the eccentric component is removed in the entire objective lens movable range is stored in the memory 71.

(Third Method) In the first and second methods, the data movement is performed while continuously moving the objective lens position or performing the track jump, but in this method, the tracing is performed to perform the data movement. . First, the objective lens position is jumped inward by 170 tracks to close the tracking loop. Since the disk has spiral grooves from the inner circumference to the outer circumference, the position of the objective lens is traced from the inner circumference to the outer circumference if left in this state. Here, while tracing, the data of the objective lens position output is changed every rotation. This way,
Since the data shifting is performed for each rotation, the eccentricity component is not captured, and the data shifting is automatically performed with the eccentricity component removed.

In any of the above-mentioned first to third methods, the data transfer of the relationship between the objective lens position and the lens position sensor output is completed. However, when actually using this data, the objective from the objective lens position output is used. You have to find the lens position. One method is to have a conversion table in the memory 71, but here, a numerical operation method using a digital signal processing circuit (DSP or the like) capable of high-speed operation will be described.

Basically, it is a method of approximating the lens position by a quintic equation.

Position = A · (X + B · X ² + C · X ³ + D
^{· X 4 + E · X 5} ) where, X is normalized objective lens position output value, A,
B, C, D and E are constants. That is,

[0066]

[Outer 1] Here, G and K are constants. G is the aforementioned S _LP1 , S
_When the value of _LP2 is substituted, the range of X is selected to be + -1.0. A, B, C, D and E are S _LP1 and S _LP2
For example, the least squares method may be used to minimize the position error from the value of. K is for correcting the difference between the output levels of S _LP1 and S _LP2 , but if it is adjusted in advance so that S _LP1 = S _LP2 when the objective lens is at the lens reference position, K = 1 may be set.

If the objective lens is displaced from the reference position,
Offset correction of racking error signal Since there is a linear relationship between the offset amount of the tracking error and the displacement of the objective lens position, it is sufficiently possible to correct the tracking offset using this relationship. In this case, the offset correction is executed in the digital signal processing circuit.

However, a method of performing offset correction more strictly will be described here. At the same time when the data of the relationship between the objective lens position and the lens position sensor output is obtained, the tracking signal when the objective lens is displaced from the reference position in the radial direction is observed at the same time, and the objective lens position and the offset amount of the tracking error signal are compared. It seeks a relationship. As shown in FIG. 8, the tracking error signal is mixed with a signal when the track crosses. Therefore, after reading the peak value and the bottom value of the tracking error signal, the center value thereof is calculated as the tracking error signal. There is a method of storing this value as a conversion table in the memory 71, or an approximate expression as described in the description of the correction of the lens position sensor is obtained and a digital signal processing circuit (DSP etc.) capable of high speed calculation is used. There is also a method of numerical calculation.

Since the tracking error signal in this case is a signal in a range much higher than the eccentricity, the sampling pulse needs to have a high frequency so that the peak and the bottom of the tracking error signal can be sufficiently captured. For example, if only the eccentricity is about 500, which is 10 times the eccentricity component 50 Hz
However, in order to read the signal when crossing the track, a sampling pulse of 10 times 10 kHz, which is about 1 kHz of the tracking error signal when crossing the track, is required.

Offset Correction of Focus Error Signal In the offset correction of the focus error signal, as a first method, an offset value is determined so that the reproduction amplitude of a signal (sector mark or address signal) preformatted on the disc becomes maximum. There is a way.

First, AF and AT servos are applied, and the amplitude value of the signal in the preformat section when the offset is forcibly added to the focus error signal is monitored. This will be described with reference to FIG. In FIG. 9, the horizontal axis is AF.
The offset amount, the vertical axis is the amplitude value of the signal. Early AF
The amplitude of the pre-format signal when a predetermined offset amount is added to the plus side (point P _{3 in} FIG. 9) around the offset position (point P _{1 in} FIG. 9) is offset to the minus side in (a) of FIG. It is assumed that the amplitude of the pre-formatted signal when the amount is added (point P _{2 in} FIG. 9) has the value shown in FIG. When two values of the amplitudes x and y are stored and compared with each other, since x> y, the maximum point of the preformatted signal amplitude value, that is, the just focus point is on the plus side from the current position. .

Next, in FIG. 9, a point obtained by adding a predetermined offset value to the plus side of the point P ₃ is set as a new center point P ₄ . Furthermore, new memory amplitude value of the preformat signal at P ₅ that by adding a predetermined offset value to the positive side of the point P _4, is compared with the amplitude memory value of the preformat signal at point P _3. Since the amplitude value is larger than the point P ₃ at point P _5, there will be more just focus point on the positive side. In this way, this operation is repeated to search for the just focus point between the points P ₄ and P ₆ .

Next, the predetermined offset amount is set to the first 1/2
As a result, the search range is narrowed down, and the same operation is repeated centering on a point P ₅ which is an intermediate point between the points P ₄ and P ₆ to drive the offset amount at the just focus point. Then, this operation is continued until there is no difference in the amplitudes of the preformat signals to be compared. The focus offset amount thus determined is stored and continuously applied to the focus error signal. It should be noted that the just-focus point detection sensitivity is improved when the pre-formatted signal is differentiated using a differentiating circuit (not shown).

There are the following methods for detecting the amplitude value of the preformatted signal.

A. A method in which the photocurrents from the RF sensors 19 and 20 are amplified by the preamplifiers 52 and 53, the output thereof is directly monitored, and the peak value at this time is held to detect the DC component.

B. Although the output of the RF sensor preamplifiers 52 and 53 is differentiated by a differentiating circuit (not shown), the peak of the signal is known. However, the method is to detect the peak of the signal after the differentiation by monitoring the pp value.

C. A method in which the signal output after differentiation is subjected to single-wave rectification or double-wave rectification and the peak value is monitored and detected.

D. A method of monitoring the output of this filter by using a filter for extracting only a certain band in which the fluctuation of the AF offset amount remarkably appears in the fluctuation of the amplitude value.

All the information of these amplitude values is A / D converted and fetched, and processed in the digital signal processing circuit 48.

As a second method, there is a method of directly taking in the magneto-optical signal information in the data portion of the disk and monitoring the amplitude value thereof. The procedure is the same as the first method.

Alternatively, the focus error signal shown in FIG.
A signal for changing the offset amount as shown in FIG. 11B may be added to monitor the output of the magneto-optical signal after the differentiating circuit as shown in FIG. At this time, the voltage value of the AF offset application signal at the position where the amplitude value of the magneto-optical signal becomes the maximum is read (corresponding to point P in FIG. 11B), and this value is always added to the focus error signal to adjust the just It can be in focus.

[0082] A first method of automatic focus gain adjustment auto focus gain adjustment will be described with reference to FIG. 12. FIG. 12 is a pseudo block diagram of a processing procedure in the digital signal processing circuit 48. First,
AF and AT servos are applied, and the objective lens is used as the reference position.
One track is made to follow or a track trace state is set. In FIG. 12, the focus error value (the offset is removed in the above process) and the sum signal value are digital data after A / D conversion, and the output value and the evaluation value are all digital data. .
Here, a disturbance value that does not cause an error is given at the same frequency as the 0 dB cross frequency of the autofocus loop gain. The amplitude of the disturbance value is given by increasing / decreasing the data in the digital signal processing circuit, and its period can also be given in (1 / intersection frequency) seconds. The division circuit 90 compares the amplitude value data of B after the application of the disturbance value with the amplitude value data of A before the application of the disturbance value, and in the case of (B <A) or (B> A), K in the multiplication circuit 91. The gain is adjusted by performing an operation so that the value of becomes (A = B).

The second method is a method which can be carried out even when the digital signal processing circuit 48 is limited to the gate array in FIG. 13, and B after the disturbance is applied from the oscillator 82.
The amplitude value of A is compared with the amplitude value of A after the gate array output, and the gain is adjusted so that A = B. At this time,
Instead of B, C after the output switching circuit 73 may be used. Since the reading value at A and the reading value at B have different phases and cannot be read at the same timing, one cycle of the disturbance is sampled to detect the amplitude value of each of A and B, and to compare them. A comparator 85 and a gain setting circuit 85 for causing the gate array to perform gain adjustment are separately required.

On the gate array input side, A /
The gain can also be adjusted by applying a disturbance after the D converter 63 and comparing the amplitude value after the application and the amplitude value after the input switching circuit 62.

Auto Tracking Gain Adjustment The auto tracking gain adjustment is performed in the same manner as the auto focus gain adjustment.

Linear Motor Gain Adjustment As shown in FIG. 1, the linear motor gain adjustment applies a disturbance of the same frequency as the 0 dB cross frequency in the linear motor loop gain to the linear motor coil 38, and the displacement of the linear motor caused by this disturbance is caused. Is detected by the output of the lens position sensor.

(First Method) The linear motor servos so as to be fixed at the home position. Next, focus and tracking servo are applied so that the objective lens is at the reference position. Here, the digital signal processing circuit 48 generates a digital disturbance signal and applies the disturbance to the linear motor coil via the D / A converter 72 and the like. The linear motor vibrates due to disturbance, but since the tracking servo is applied, the objective lens vibrates in the disk radial direction according to the movement of the linear motor so as to maintain tracking. Therefore, the lens position sensor also produces an output synchronized with the vibration. Since the linear motor open loop gain is constant except for the mechanical sensitivity of the linear motor, the displacement of the linear motor becomes a predetermined value (0 dB at a crossing frequency of 0 dB) when a certain constant disturbance amplitude is applied. It suffices to set the calculation gain. The digital signal processing circuit 48 reads the output value of the lens position sensor and sets the linear motor servo loop gain so that the amplitude value becomes a predetermined value.

(Second Method) In this method, as shown in FIG. 13, a disturbance is generated from an oscillator 82 provided outside the digital signal processing circuit 48. As in the first method, focus, tracking,
Each servo of the linear motor is applied, the objective lens position is the reference position, and the disturbance frequency is the crossing frequency of 0 dB. Here, the output disturbance signal is taken in by the A / D converter 86, its amplitude is detected by the amplitude value detector 92, and evaluated by the digital signal processing circuit 48. The displacement of the linear motor is performed by detecting the output of the lens position sensor as in the first method. The digital signal processing circuit 48 determines the calculation gain so that the displacement of the linear motor becomes a predetermined value (0 dB at a crossing frequency of 0 dB) when a constant disturbance amplitude is applied. In this method, since an analog oscillator is used, it is not necessary to generate an oscillating waveform in the digital signal processing circuit. Therefore, not only the software load is reduced, but also a high frequency can be easily generated.

(Third Method) In this method, the objective lens is fixed at the reference position, the tracking servo is opened, and the linear motor is oscillated by disturbance to cause the objective lens to vibrate in the radial direction of the disk, and the track The displacement amount of the linear motor is detected by counting the tracking error signal at the time of crossing. The focus and linear motor servos are applied at the home position, and the disturbance frequency is a crossing frequency of 0 dB, as in the first method. In this case, if the eccentricity component is counted, an error occurs in the detection of the displacement amount.Therefore, it is possible to count only the eccentricity component in advance without applying the disturbance and subtract it from the count value in the state of the disturbance. is necessary. However, this method may cause an error of about 1 track at the maximum, but if the displacement amount is set to a large value, it is a problem-free amount.

Linearity Correction of Laser Power Monitor The laser power control in the present invention is performed by detecting the output signal from the monitor photodiode 79, but the monitor is affected by the return light from the disk only with this. It is not possible to control the power of the laser light applied to the disc with perfect accuracy.

Therefore, in the present invention, the linearity is corrected by using the reflected light from the disk. The reflected light from the disk is received by the servo sensor 18, converted into a current voltage, and then converted into a sum signal (S ₁ + S ₂ + S ₃ + S ₄ ) by the arithmetic circuit 44. The sum signal is A / D converted and then input to the digital signal processing circuit 48, while the monitor photodiode 79
Is output to the digital signal processing circuit 48 via the preamplifier 80 and the A / D converter 63. As shown in FIG. 14, the digital signal processing circuit 48 controls the laser driver 78 to emit a laser beam of 10 mW having a relatively good monitor linearity. At this time, if the sum signal is 10 V, the laser output is the sum signal / 1000 (W). Sum signal output is 0.1V
The monitor output can be corrected based on the sum signal output by reducing the laser output so as to decrease each time and returning the data with respect to the monitor output. The correction data is stored in the memory 71, and by using this data to correct the monitor output and control the laser power, accurate laser irradiation can be performed.

FIG. 15 shows an algorithm for carrying out the servo system automatic adjusting method of the present invention.

The automatic adjustment of the present invention may be performed every time the magneto-optical disk is loaded and the magneto-optical disk apparatus is started up, or the temperature sensor provided in the apparatus during use changes the temperature by a predetermined value or more. May be performed each time there is a concern that the positional deviation of the optical components as described above may occur. If automatic adjustment is performed each time the magneto-optical disk is newly loaded, it is possible to easily correct a positioning error at the time of adjustment of the servo sensor or the like and a positional deviation that occurs after the adjustment. In addition, it is possible to correct all variations in AT offset, AF gain, and AT gain that occur when the objective lens is displaced in the radial direction due to variations in the guide groove of the disc. Also,
AF due to variations in disk substrate thickness and refractive index
The offset, the AT offset caused by the warp of the disk substrate, and the like can be simultaneously corrected.

If automatic adjustment is performed every time the temperature sensor shows a temperature change of a predetermined value or more, the positional deviation of the optical components due to the temperature change and the light spot on the servo sensor due to the wavelength change of the semiconductor laser will occur. It is possible to correct misalignment and the like. For example, in the magneto-optical disk device shown in FIG. 16, assuming that the beam shaping ratio of the beam shaping prism 3 is 2 and BK7 is glass, the deflection angle of the light flux is about 3 seconds per wavelength change of 1 nm. Condensing lens 1
If the focal length of No. 5 is 40 mm, the light spot shift on the servo sensor is about 0.6 μm per wavelength change of 1 nm. Since the wavelength of the semiconductor laser changes by 0.3 nm per temperature change of 1 degree, the deviation of the light spot becomes about 6 microns at a temperature change of 30 degrees, which affects the tracking servo accuracy. However, if the temperature change is automatically adjusted every 5 degrees, the above value will be within a value that causes almost no problem. This eliminates the need for an achromatic prism using an expensive beam-shaping prism in which a plurality of types of glass are combined.

Although the automatic adjustment of the servo system has been described above, the present invention may be any method other than the focus error detection method, tracking error detection method, and objective lens position detection method described in the embodiments. Separate detectors may be used for the focus error and the tracking error.

Further, in the above-mentioned embodiment, the configuration is such that the reflected light of the medium is detected. However, when the medium is a transmission type,
The control means may be configured by detecting the transmitted light.

[0097]

As described above, the optical information processing apparatus of the present invention uses the tracking error signal and the output signal of the position detecting means for detecting the relative position of the objective lens with respect to the optical head to determine the position of the objective lens and the tracking error. A means for measuring the relationship with the offset amount of the signal, a storage means for storing the measured relationship, an offset amount is obtained from the output signal of the position detection means based on the relationship stored in the storage means, and the obtained offset amount Since the means for correcting the tracking error signal is provided, the complicated adjustment process is unnecessary, and the offset of the tracking error signal can be corrected exactly.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a control circuit used in an optical information processing apparatus of the present invention.

FIG. 2 is a flowchart showing a procedure of automatic adjustment in the apparatus of the present invention.

FIG. 3 is a diagram for explaining a method of correcting a tracking error signal offset value used in the present invention.

FIG. 4 is a diagram showing an output of an objective lens position sensor used in the present invention.

FIG. 5 is a diagram for explaining a method of detecting eccentricity of a disc by using an objective lens position sensor.

FIG. 6 is a first calibration method for an objective lens position sensor according to the present invention.
FIG. 6 is a diagram for explaining an example of FIG.

FIG. 7 is a second calibration method of the objective lens position sensor according to the present invention.
FIG. 6 is a diagram for explaining an example of FIG.

FIG. 8 is a diagram for explaining a method of calibrating the offset value of the tracking error signal when the objective lens of the present invention is displaced from the reference position.

FIG. 9 is a diagram for explaining a first example of offset correction of a focus error signal according to the present invention.

FIG. 10 is a diagram for explaining the first embodiment of the offset correction of the focus error signal of the present invention.

FIG. 11 is a diagram for explaining a second embodiment of the offset correction of the focus error signal of the present invention.

FIG. 12 is a diagram for explaining the first embodiment of the AF gain adjusting method of the present invention.

FIG. 13 is a diagram for explaining the second embodiment of the AF gain adjusting method of the present invention.

FIG. 14 is a diagram for explaining linearity correction of the laser power monitor of the present invention.

FIG. 15 is a diagram for explaining an algorithm for carrying out the present invention.

FIG. 16 is a diagram for explaining an optical system of a conventional magneto-optical disk device.

FIG. 17 is a diagram for explaining an actuator of a conventional magneto-optical disk device.

FIG. 18 is a diagram for explaining a linear motor of a conventional magneto-optical disk device.

FIG. 19 is a diagram for explaining a servo system of a conventional magneto-optical disk.

FIG. 20 is a diagram for explaining an RF system of a conventional magneto-optical disk device.

FIG. 21 is a diagram for explaining a conventional magneto-optical disk.

[Explanation of symbols]

 1 Semiconductor Laser 18 Servo Sensor 19 RF Sensor 20 RF Sensor 34 2-Division Sensor 79 Monitor Photodiode

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masayuki Usui 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshihiko Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (72) Inventor Hisabun Hisano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirotake Ando 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (72) Inventor Hideo Nakajima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shinji Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kenji Tamaki, Canon Electronics Co., Ltd. 1248 Shimokagemori, Chichibu, Saitama Prefecture

Claims (1)

[Claims] 1. An optical head for irradiating an optical recording medium on which a track is formed with a light beam, an objective lens mounted on the optical head for converging the light beam on the track, and reflection of the light beam by the medium. A photodetector for detecting light or transmitted light, a means for generating a tracking error signal indicating the positional deviation between the irradiation position of the light beam and the track from the output of the photodetector, and the objective lens in the direction crossing the track. A tracking actuator to be moved, a tracking control means for correcting the positional deviation by driving the tracking actuator according to the tracking error signal, and a position detection for detecting the relative position of the objective lens in the direction crossing the track with respect to the optical head. And an optical information processing device for recording and / or reproducing information on the optical recording medium. In the above arrangement, means for measuring the relationship between the position of the objective lens and the offset amount of the tracking error signal from the tracking error signal and the output signal of the position detecting means, storage means for storing the measured relationship, and position An optical information processing apparatus, comprising: means for obtaining an offset amount from an output signal of the detection means based on a relationship stored in the storage means; and means for correcting the tracking error signal by the obtained offset amount.