JP2633195B2 - Optical information processing device - Google Patents

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 and reproducing information on an optical disk or the like.

[0002]

2. Description of the Related Art In recent years, the "digital signal processing method" for performing digital signal processing, which has been conventionally performed by analog, has become popular, such as a compact disk (CD), a digital audio tape (DAT), and a communication line. Has been put to practical use in a wide range of fields. This is because the "digital signal processing method" can realize complicated signal processing algorithms by software, so that hardware can be simplified and the system cost can be reduced, and it is possible to flexibly change specifications such as selection of filter constants and algorithms. This is because it has such advantages as being able to respond. In addition, advances in IC technology have made it possible to obtain digital signal processing ICs and DSPs (digital signal processors) having a high processing speed at low prices.

On the other hand, optical information processing apparatuses such as optical discs
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 large-capacity memory. In particular, a magneto-optical disk is required as an external memory of a computer to have high reliability, high speed access, and the like in addition to the high density and large capacity described above.

[0004] For this reason, the electric servo system also requires control in which outputs from various types of sensors are combined in a complicated manner. An example of a conventional magneto-optical disk device will be described with reference to FIG.

In FIG. 16, a light beam emitted from a semiconductor laser 1 is converted into a parallel light beam by a collimator lens 2 and is converted into a light beam having a substantially circular cross section by a polarizing beam splitter 3 having a beam shaping function. The parallel light beam passes through the prism 4
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 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.

[0006] The reflected light from the disk 9 is again converted into a parallel light beam by the objective lens 5 and bent by the prism 4.
It goes to the polarization 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 and 20.
The light is split into light beams transmitted in the direction.

The condensing lens 15 includes, for example, an element that generates astigmatism, and the light flux is condensed on the servo sensor 18. The servo sensor 18 is a quadrant 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 three axial directions and adjusted so that equal outputs are generated from the four sensors. I have.

The luminous flux transmitted through the beam splitter 16 is
The light is split into two by a polarization beam splitter 17 and condensed on a radio frequency (RF) sensor 19 and an 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 unit 14.

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

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

In FIG. 17, reference numeral 5 denotes an objective lens,
It is fixed to the bobbin 21. Reference numerals 22 and 23 denote 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 focus magnet 25 fixed to 6. 27 is
Reference numeral 28 denotes a support shaft for the bobbin 21, and reference numeral 28 denotes an under limiter for determining the lowermost end of the bobbin. Reference numeral 29 denotes a counterweight of the objective lens 5 which is fixed to the bobbin.

Reference numeral 30 denotes a light emitting diode, and 31 denotes
This is a flexible light emitting diode 30. The light beam emitted from the light emitting diode 30 passes through the slit 32 and is shaped, and is projected as a light beam 33 on the two-divided sensor 34. The light emitting diode 30 is fixed to 21, and when the actuator is displaced in the tracking direction, each light receiving surface 34-1 of the two-divided sensor of the light beam 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 denotes a flexure for the two-division sensor 34.

A linear motor section of a conventional magneto-optical disk drive 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 support shaft, which are fixed to the carriage 13 as actuators. The carriage 13 is supported on rails 36-1 and 36-2 by bearings 37-1 and 37-2, etc., is movable in the disk radial direction 12, and the linear motor section includes a coil 38, a yoke 39, and 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. 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.

The servo sensor 18 is used when the objective lens 5 is located at the center of the light beam from the semiconductor laser 1 and the light beam is focused 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 for the focus error detection method, 18-1 to 18-4
If the outputs from the respective sensors are S _{1 to} S ₄ , a difference in the output of the diagonal sum is observed according to the focus shift between the disk 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, the output is 0 when the light spot is focused on the disk, negative when the disk is close, and positive when the disk is far. Get.

The tracking error detection method uses a push-pull method. The push-pull method is a method of observing the balance of the diffracted light from the guide groove of the disk in the far field, and the distribution of the diffracted light is determined according to the radial displacement between a predetermined track on the disk and the light spot. And the difference between the outputs of the sensors divided by the dividing line in the tangential direction 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, the output is 0 if the light spot is on the track, negative if the light spot is shifted in the inner circumferential direction, and shifted in the outer circumferential direction of the disk. If you do, you get a positive output.

In the push-pull method, when the objective lens 5 is largely displaced 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 unbalanced distribution of the diffracted light according to the track deviation, an offset occurs in the output of the auto tracking (hereinafter, referred to as AT). In order to perform high-speed access, it is advantageous if the objective lens can be used by being moved from the center of the light beam from the semiconductor laser 1 by about 100 to 150 tracks. Since this offset is almost proportional to the amount of displacement of the objective lens from the center of the light beam, it can be easily corrected if the position of the objective lens can be detected.

Therefore, in this example, an 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 S _LP1 ,
As S _LP2 , the following lens position (hereinafter referred to as LP) output S _LP is adjusted to be 0 when the objective lens is at the center of the light beam.

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

Since the output of the lens position sensor indicates the displacement between the carriage 13 and the objective lens 5, if this is used to drive the linear motor, the objective lens position can always be maintained at the center of the light beam.

Although the servo sensors and the like have been described above, they cannot be completely aligned mechanically. Therefore, when the conventional analog servo signal processing is performed, the sensor output is adjusted after the mechanical adjustment. It is common practice to provide an adjustment volume (not shown) or the like for electrical adjustment.

Next, servo signal processing will be briefly described.

Outputs S _{1 to} S ₄ from servo sensor 18
After being amplified by the preamplifier 43, the signal is extracted by the arithmetic circuit 44 as an AT and an auto focus (hereinafter, referred to as AF) output as described above. Lens position sensor 34
The outputs S _LP1 and S _LP2 are amplified by the preamplifier 45 and then taken out as a lens position output by the arithmetic circuit 46. Among them, the AT output and the LP output are added by the adding circuit 47, and the tracking error signal is corrected so that no offset occurs in the tracking error signal even if the position of the objective lens is shifted (corrected AT output). The AF output, the corrected AT output, and the LP output are taken into the servo signal processing circuit 48 and output to the AF driver 49, the AT driver 50, and the linear motor driver 51 at appropriate timing. Driving signals from the respective drivers are AF coil 23, 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, reference numerals 19 and 20 denote the aforementioned RF sensor and RF sensor, respectively. Reference numerals 52 and 53 denote preamplifiers for amplifying the outputs from the RF sensors 19 and 20, respectively. 54 and 55 are RF sensors 19 and 20 respectively.
This 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 beam 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 preformat signal 57 such as a sector mark or an address increases or decreases the amount of light incident on the RF sensors A and B uniformly, and is 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, reference numeral 11 denotes the center of the disk, on which tracks 58 and guide grooves 59 are provided spirally. In the track, a pre-format signal such as a sector mark or an address contains pits 60.
And a data section in which the user records the magneto-optical signal as information in the form of a magneto-optical pit 61.

[0031]

In the magneto-optical disk drive having the above-described structure, it is impossible to mechanically align the servo sensor and the like completely. And electric adjustments are made one by one, so that it was difficult to reduce the cost.

Further, since the above-mentioned focus or tracking error detection method does not directly detect the condensing state of the light spot on the disk, the relative position of the servo sensor and the light spot on the servo sensor, or In the case where the position of the semiconductor laser or the like is displaced due to some external force after the adjustment, the light spot is not correctly focused on a predetermined track on the disk. Changes in these states can often occur due to temperature changes, vibration during transportation, and the like, and reduce servo accuracy. Or,
Even if the servo sensor itself does not shift, the temperature of the semiconductor laser changes due to temperature changes, and the deflection angle of the light beam in the polarizing beam splitter with a beam shaping function changes.
The light spot position on the servo sensor may move.

Also, in a multi-track jump or the like,
Since the AT offset generated when the objective lens is used at a position shifted in the radial direction changes due to variations in the depth of the guide groove of the disk, etc., unless the offset value is adjusted for each disk, the tracking accuracy decreases. .

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

[0035]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical head for irradiating a light beam on an optical recording medium having a track formed thereon, and a light beam mounted on the optical head and condensing 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 indicating a displacement between a track irradiated with the light beam and a track from an output of the photodetector. A tracking actuator for moving the objective lens in a direction transverse to a track; a tracking control means for correcting the positional deviation by driving the tracking actuator in accordance with the tracking error signal; and a track for the objective lens with respect to the optical head. Position detecting means for detecting a relative position in a direction crossing the optical recording medium, and recording information on the optical recording medium. And / or in the optical information processing apparatus for performing reproduction, after moving the center of the objective lens to the center position of the light beam serving as the reference position based on the output signal of the position detection means, moving the objective lens near the reference position. This is achieved by providing a means for finely oscillating and detecting an offset amount of the tracking error signal from the tracking error signal at this time and a means for correcting the tracking error signal based on the detected offset amount.

[0036]

FIG. 1 is a block diagram showing an embodiment of a control circuit used in an optical information processing apparatus according to the present invention. Here, the servo sensor 18, the preamplifier 43, and the arithmetic circuit 44 are connected as shown, and are connected to a digital signal processing circuit 48 via an input switching circuit 62 and an analog / digital A / D (digital / analog) converter 63. The arithmetic circuit 44 is also connected to the track count circuit 64. This output is connected to a digital signal processing circuit 48. Lens position sensor 3
4 is connected to an input switching circuit 62 via a 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 a digital signal processing circuit 48 via a motor driver 68. The two RF sensors 19 and 20 are connected to an RF signal processing circuit 69 via preamplifiers 52 and 53, and one output is connected to an input switching circuit 62 via a detection circuit 70 and the other is a digital signal. 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, a D / A converter 72,
The four sample-and-holds (S
/ H) circuits 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 for monitoring 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 device is provided by the input switching circuit 6.
2 are connected.

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 a preamplifier 43, and then processed by an arithmetic circuit 44 into a focus error signal, a tracking error signal, and a focus tracking sum signal. After one of these signals is selected by the input switching circuit 62, the A / D
The signal is converted into a digital signal by the converter 63 and input to the digital signal processing circuit 48. Digital signal processing circuit 4
Numeral 8 outputs a digital control value to the D / A converter 72 to control the AT coil and the AF coil so that the tracking error level and the focus error level become zero. The analogized control signal is selected by the output switching circuit 73 and 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 a magneto-optical signal, it is necessary to irradiate the disk with a laser beam, but the digital signal processing circuit 48 sets the laser beam control value to D / D.
Output to the A converter 72. The analog signal is passed through an S / H circuit 74 after being selected by an output switch 73.
The data is input to the laser driver 78. The laser driver controls the laser diode 1 so as to obtain a light amount necessary for reading and writing. A monitor photodiode 79 for monitoring the emitted light is attached to the laser diode, and its output is supplied to an input switching circuit 6 via a preamplifier 80.
2 is input. By monitoring the amount of light with the monitor photodiode 79, the digital signal processing circuit 48 can accurately control the amount of laser emission. The signal line directly connected from the digital signal processing circuit 48 to the laser driver 78 is a laser ON / OFF signal line at the time of writing.

The lens position sensor 34 is composed of a two-part photodiode, and is illuminated by a light emitting diode (LED) 30 for a lens position sensor. A change occurs in the output of the photodiode due to a change in the position of the objective lens. This output is amplified by the preamplifier 45, input to the input switching circuit 62, passes through the A / D converter 63, and is sent to the digital signal processing circuit 48. Is entered. The output of the home position sensor 65 for detecting 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 devices. ing.

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

The spindle motor 42 is a motor driver 6
The start and stop are controlled by the CPU 66 via the digital signal processing circuit 48.

The linear motor coil 38 is driven via a driver 51 by a speed command from a digital signal processing circuit 48. When the linear motor starts, 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 a magneto-optical signal and a preformat signal into an electric signal. This signal is amplified by preamplifiers 52 and 53, and then subjected to differential detection, in-phase detection, and peak detection in an RF signal processing circuit 69. This output passes through a digital signal processing circuit 48 as digital data, is processed by a CPU 66, and is output as digital information to an external device through an external interface circuit 67. On the other hand, the envelope of the signal subjected to the RF signal processing is detected by the detection circuit 70 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 correctly.

FIG. 2 shows a procedure for automatically adjusting 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, and only the AF servo is used to measure the offset value of the tracking error signal, and this is corrected. (Step 1) Examples of the offset corrected at this time include a positioning error at the time of adjustment of the servo sensor and the like, a position shift after the adjustment, a warpage of the disk, and the like.

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 operations can be performed simultaneously or individually. In the calibration of the objective lens position sensor, the number of tracks on the disk is counted to determine the absolute position of the objective lens from the center of the light beam, and the output is used to calibrate the output of the objective lens position sensor. Thereby, the linearity of the objective lens position sensor is corrected.

The offset correction of the tracking error signal when the objective lens deviates 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 magnitude of the offset due to variations in the depth of the guide groove by the disk 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 offset value is determined by applying AF and AT servos so that the reproduction amplitude of a signal (such as a sector mark or an address signal) preformatted on the disk is maximized. This makes it possible to correct an AF offset caused by a positioning error at the time of adjustment of a servo sensor or the like, a position shift after the adjustment, a thickness of the disk substrate, a variation in the refractive index, a variation in the guide groove of the disk, and the like.

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

As in step 4, the AT gain is adjusted. (Step 5) Next, the gain of the linear motor is adjusted. (Step 6) Apply AF and AT servo to a predetermined track, apply appropriate disturbance to the linear motor from the digital signal processing circuit, and use the output of the objective lens position sensor calibrated in step 2 to determine the response of the linear motor. Do it. Variations of the linear motor at the initial stage and after the elapse of time can be corrected.

Finally, the linearity of the laser power monitor is corrected for the monitor photodiode incorporated in the semiconductor laser. (Step 7)
In the magneto-optical disk drive, the laser power is changed by about 10 times at the time of data reproduction and at the time of erasing and writing, so that the linearity of the monitor is poor due to the return light from the disk. Therefore, this may be corrected using the output of the servo sensor. Thereby, recording / reproducing with optimal laser power becomes possible.

Hereinafter, the correction method in each of the above steps will be described in detail.

The tracking at the reference position of the objective lens (on the optical axis)
King error signal offset correction method 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 brought to the center position of the light beam from the semiconductor laser (hereinafter referred to as the lens reference position). As a method, when the focus actuator is lowered to the lowest point, the mechanical pin of the actuator is fitted at the middle point. Or you may
The output of the preamplifier 45 of the lens position sensor 34 is adjusted at the time of manufacture so as to be a predetermined value at the lens reference position, and at the time of correction, the output of the lens position sensor is first set to the predetermined value. Alternatively, the lens position may be moved electrically.

In this state, the focus pull-in operation is performed so that the focus is substantially at the focus point. Next, a tracking error signal at the time of crossing the 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 while the lens is fixed at the reference point to vibrate the linear motor. If the linear motor is vibrated sinusoidally, the objective lens vibrates so as 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 may be used in which the objective lens is slightly vibrated in the tracking direction at the reference position while the linear motor is fixed at the home position so as not to move. In this way, it is possible to obtain a tracking error signal including an offset near the lens reference position.

As shown in FIG. 3, the tracking error signal has an offset. This signal is a tracking signal output from the arithmetic circuit 44 as described above. The signal is converted into a digital signal by the sampling pulse shown in FIG. 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, thereby recognizing 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. In the tracking operation after the completion of the correction, the offset value A
The tracking offset value obtained here is subtracted from the digital tracking error signal before offset correction obtained via the / D converter 63 to generate a tracking error signal after offset correction, and the tracking error value after offset correction is calculated. To control the tracking loop.

Calibration of Objective Lens Position Sensor The output of the lens position sensor 34 has the 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 calculating (S _LP1 −S _LP2 ) / (S _LP1 + S _LP2 ), it is possible to remove the in-phase fluctuation such as the temperature fluctuation of the sensor output and detect the position of the objective lens. . However, since S _LP1 and S _LP2 do not change linearly with respect to 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 position of the objective lens at the center of the light beam of the semiconductor laser, the focus and tracking are pulled in and the disk is rotated. Since the disk is eccentric, the tracking actuator swings in the tracking direction following the eccentricity, and the outputs S _LP1 and S _{LP2 of the} two lens position sensors 34 fluctuate accordingly. As shown in FIG. 5, this fluctuating S _LP1 ,
S _LP2 is sampled by a rotation synchronization sampling pulse synchronized with the rotation of the disk, digitized by an A / D converter 63, passed through a digital signal processing circuit 48, and stored in a memory 71 eccentric data during one rotation. This data is used for removing the eccentric component in accordance with the data of the objective lens position described below.

Next, the tracking servo loop is opened, and the tracking actuator is moved to the movable range of the objective lens (for example, ± 250 microns = ± 170 tracks).
A track jump is performed only during this time, and during that time, the data of the relationship between the lens position sensor outputs S _LP1 , S _LP2 and the objective lens position displacement is performed. While moving the objective lens position from -170 track to +170 track, the outputs of S _LP1 and LP 2 are sampled every 10 tracks, and A / A
Perform D conversion. The outputs of S _LP1 and S _LP2 fluctuate under the influence of eccentricity as shown in FIG. Here, the data obtained by subtracting the eccentricity by using the above-mentioned eccentricity data is stored in the memory 71.

(Second Method) In the first method, the objective lens position is continuously moved from the -170 track to the +170 track to perform data skipping during the movement. Jump and close the tracking loop to perform data collection. First, the operation is the same as that of the first method until the position of the objective lens is brought to the optical center point and the tracking loop is turned on. However, in the second method, the eccentricity data is not executed. Here, during one or several rotations of the disc, the objective lens position output S
_LP1, reads the S _LP2, get removed objective lens position of the eccentric components determine the average value output an output therebetween S _LP1, S _LP2 in the digital signal processing circuit 48. Here, as shown in FIG. 7, a track jump is executed by a predetermined number of tracks, the tracking loop is closed at the objective lens position after the movement, and the output of the objective lens position is read for one or several rotations to obtain an average value. The objective lens position output at that point is obtained. As described above, the track jump and the calculation of the average value of the data are repeated, and the output value of the objective lens position from which the eccentric component is removed in the entire movable range of the objective lens is stored in the memory 71.

(Third Method) In the first and second methods, data is collected while continuously moving the position of the objective lens or performing a track jump. In this system, data is collected by performing tracing. . First, the position of the objective lens is jumped 170 tracks inward, and the tracking loop is closed. Since the disk has spiral grooves formed from the inner circumference to the outer circumference, if this state is maintained, the position of the objective lens is traced from the inner circumference to the outer circumference. Here, data tracing of the objective lens position output is performed every rotation while tracing. This way,
Since the data eccentricity is performed every one rotation, the eccentric component is not captured, and the data eccentricity-removed data is automatically extracted.

In any one of the first to third methods, the data of the relationship between the objective lens position and the output of the lens position sensor has been completed, but when this data is actually used, the objective data from the output of the objective lens position is used. The lens position must be determined. One method is to have a conversion table in the memory 71. Here, a numerical operation method using a digital signal processing circuit (DSP or the like) capable of high-speed operation will be described.

Basically, this is a method of approximating the lens position by a fifth-order equation.

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

[0066]

[Outside 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
May be determined by, for example, the least-squares method so as to minimize the position error. K is for correcting the difference between the output levels of S _LP1 and S _{LP2. If} the objective lens is at the lens reference position and has been adjusted in advance so that S _LP1 = S _LP2 , K = 1 may be set.

When the objective lens deviates 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 to some extent, it is sufficiently possible to correct the tracking offset using this relationship. In this case, the offset correction is performed in the digital signal processing circuit.

However, here, a method for performing the offset correction more strictly will be described. At the same time that the data of the relationship between the objective lens position and the output of the lens position sensor is obtained, a tracking signal is observed when the objective lens is shifted from the reference position in the radial direction, and the offset between the objective lens position and the tracking error signal is observed. Ask for a relationship. As shown in FIG. 8, a signal at the time of track crossing is mixed in the tracking error signal. Therefore, after reading the peak value and the bottom value of the tracking error signal, the center value is calculated as the tracking error signal. This value may be stored 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 may be obtained, and a digital signal processing circuit (DSP or the like) capable of calculating at high speed may be used. There is also a method of performing a numerical operation by using.

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

Offset Correction of Focus Error Signal In 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 a disk is maximized. There is a way.

First, the AF and AT servos are applied, and the amplitude value of the signal in the preformat section when an 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 and the vertical axis are signal amplitude values. Early AF
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), the amplitude of the preformat signal is offset to the minus side in FIG. Assume that the amplitude of the preformat signal when the amount is added (point P _{2 in} FIG. 9) is the value shown in FIG. 10B. When the two values of the amplitudes x and y are stored and compared, since x> y, the maximum point of the preformat 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 defined 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, repeating this operation, search that there is just focus point between points P ₄ and the point P _6.

Next, the predetermined offset amount is set to the first half.
Will narrow the range of search as a point P _4, go drove the offset amount at the just focus point by repeating the same operation around the point P ₅ in the middle of the point P _6. This operation is continued until there is no difference between the preformat signal amplitudes to be compared. As a result, the determined focus offset amount is stored and always applied to the focus error signal. It should be noted that the detection sensitivity of the just focus point is improved by using a signal after differentiation using a differentiating circuit (not shown) as the preformat signal.

As a method for detecting the amplitude value of the preformat signal, there is the following method.

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

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

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 a filter using a filter for extracting only a certain band in which the variation of the AF offset amount is remarkably represented by the variation of the amplitude value.

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

As a second method, there is a method of directly taking in magneto-optical signal information in the data portion of the disk and monitoring the amplitude value. 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 point where the amplitude value of the magneto-optical signal becomes the maximum is read (corresponding to the point P in FIG. 11B), and this value is always added to the focus error signal. Can be 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,
Apply AF and AT servos, set the objective lens as the reference position,
One track is followed or a track trace is made. In FIG. 12, the focus error value (the offset has been 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 at the same frequency as the 0 dB crossover frequency of the auto focus loop gain is given. The amplitude of the disturbance value is given by increasing or decreasing the data in the digital signal processing circuit, and its cycle can be given in (1 / crossover frequency) seconds. The amplitude value data at B after the application of the disturbance value is compared with the amplitude value data at A before the application by the division circuit 90. In the case of (B <A) or (B> A), the K value in the multiplication circuit 91 is obtained. Is performed so that (A = B), and gain adjustment is performed.

The second method is a method that can be performed even when the digital signal processing circuit 48 is limited to a gate array in FIG.
Is compared with the amplitude value of A after output of the gate array, 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. Also, since the reading value at A and the reading value at B have different phases and cannot be read at the same timing, one period of the disturbance is sampled to detect the amplitude values of A and B and to compare them. A comparator 85 and a gain setting circuit 85 for making the gate array perform gain adjustment are separately required.

On the input side of the gate array, A /
Gain adjustment can also be performed by applying a disturbance after the D converter 63 and comparing the amplitude value after the application with the amplitude value after the input switching circuit 62.

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

Linear motor gain adjustment As shown in FIG. 1, the linear motor gain is adjusted by applying a disturbance of the same frequency as the 0 dB crossing frequency in the linear motor loop gain to the linear motor coil 38, thereby causing the displacement of the linear motor. Is detected by the output of the lens position sensor.

(First Method) Servo is applied so that the linear motor is 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 a disturbance to the linear motor coil via the D / A converter 72 and the like. The linear motor vibrates due to the disturbance, but since the tracking servo is applied, the objective lens vibrates in the disk radial direction in accordance with the movement of the linear motor so as to maintain tracking. Therefore, the lens position sensor also generates 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 0 dB cross frequency) when a certain disturbance amplitude is applied. What is necessary is just to set the operation 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, a disturbance is generated by an oscillator 82 provided outside the digital signal processing circuit 48 as shown in FIG. As in the first method, focus, tracking,
Each servo of the linear motor is applied, the objective lens position is a reference position, and the disturbance frequency is a 0 dB crossover frequency. 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 operation gain so that the displacement of the linear motor becomes a predetermined value (0 dB at 0 dB crossover frequency) when a constant disturbance amplitude is applied. In this method, since an analog oscillator is used, it is not necessary to generate an oscillation waveform in a digital signal processing circuit, so that 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 a disturbance is applied to the linear motor to oscillate the object lens in the radial direction of the disk. 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 the 0 dB crossover frequency, as in the first method. In this case, counting the eccentric component causes an error in the detection of the displacement amount.Therefore, in advance, only the eccentric component is counted in a state where no disturbance is applied, and subtracted from the count value in a state where the disturbance is applied. is necessary. However, in this method, an error of about one track at the maximum may occur, but if the displacement amount is set to be large, the amount is not a problem.

Laser Power Monitor Linearity Correction The laser power control in the present invention is performed by detecting the output signal from the monitor photodiode 79. However, since the monitor alone is affected by the return light from the disk, the laser power is controlled. The power of the laser beam applied to the disc cannot be controlled with perfect accuracy.

Therefore, in the present invention, the linearity is corrected using the reflected light from the disk. The reflected light from the disk is received by the servo sensor 18 and is converted into a sum signal (S ₁ + S ₂ + S ₃ + S ₄ ) by the arithmetic circuit 44 after current-voltage conversion. After the A / D conversion, the sum signal is input to the digital signal processing circuit 48.
Is input 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 so as to emit a laser beam of 10 mW having 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, for example, 0.1V
If the data on the relationship with the monitor output is obtained while lowering the laser output so as to gradually decrease, the monitor output can be corrected based on the sum signal output. Correction data is stored in the memory 71. Correcting the monitor output with this data and controlling the laser power enables accurate laser irradiation.

FIG. 15 shows an algorithm for implementing the servo system automatic adjustment 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 device is started up, or a temperature sensor provided in the device during use may cause a temperature change equal to or more than a predetermined value. And may be performed each time there is a concern about the displacement of the optical component or the like as described above. If automatic adjustment is performed each time a magneto-optical disk is newly loaded, a positioning error at the time of adjustment of a servo sensor or the like, or a position shift generated after adjustment can be easily corrected each time. In addition, it is also possible to correct all variations in AT offset, AF gain, AT gain, and the like that occur when the objective lens is shifted in the radial direction due to variations in the guide groove of the disk. Also,
AF caused by variations in the thickness and refractive index of the disk substrate
An offset, an AT offset caused by a warpage of the disk substrate, and the like can be simultaneously corrected.

When the temperature sensor shows a temperature change equal to or more than a predetermined value, if the automatic adjustment is performed, the displacement of the optical component due to the temperature change and the light spot on the servo sensor due to the change in the wavelength of the semiconductor laser will be described. It is possible to correct a displacement or the like. For example, in the magneto-optical disk device shown in FIG. 16, when the beam shaping ratio of the beam shaping prism 3 is 2 and the glass is BK7, the deflection angle of the light beam is about 3 seconds per 1 nm change in wavelength. Condensing lens 1
Assuming that the focal length of No. 5 is 40 mm, the light spot shift on the servo sensor is approximately 0.6 microns per 1 nm change in wavelength. Since the wavelength of the semiconductor laser changes by 0.3 nm every time the temperature changes by 1 degree, the shift of the light spot becomes almost 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 can be set to a value that is almost no problem. This eliminates the need for an achromatic prism using an expensive beam shaping prism combining a plurality of types of glass.

Although the automatic adjustment of the servo system has been described above, the present invention may be applied to any system other than the focus error detection system, tracking error detection system, and objective lens position detection system described in the embodiments. The focus error and the tracking error may use separate detectors.

Further, in the above-described embodiment, the configuration is such that the reflected light from the medium is detected.
The control means may be configured by detecting the transmitted light.

[0097]

As described above, in the optical information processing apparatus of the present invention, the center of the objective lens is moved to the center position of the light beam serving as the reference position based on the output signal of the position detection means of the objective lens. Then, a means for slightly vibrating the objective lens near the reference position, and detecting the offset amount of the tracking error signal from the tracking error signal at this time,
Since the means for correcting the tracking error signal based on the detected offset amount is provided, a complicated adjustment step is not required, and the offset of the tracking error signal can be easily corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a control circuit used in an optical information processing device 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 disk using an objective lens position sensor.

FIG. 6 shows a first method of calibrating the objective lens position sensor according to the present invention.
It is a figure for explaining the Example of.

FIG. 7 shows a second calibration method of the objective lens position sensor according to the present invention.
It is a figure for explaining the Example of.

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

FIG. 9 is a diagram illustrating a first embodiment of offset correction of a focus error signal according to the present invention.

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

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

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

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

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

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

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

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

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

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

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser 18 servo sensor 19 RF sensor 20 RF sensor 34 split sensor 79 monitor photodiode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Usui 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshihiko Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hisashi Baba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirotake Ando 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideo Nakajima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shinji Sakai 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kenji Tamaki 1248 Shimokagemori, Chichibu City, Saitama Prefecture Inside Canon Electronics Co., Ltd.

Claims (1)

(57) [Claims] 1. An optical head for irradiating a light beam onto an optical recording medium having a track formed thereon, an objective lens mounted on the optical head and condensing 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 a positional deviation between a track irradiated with the light beam and a track from an output of the photodetector, and moving the objective lens in a direction crossing the track. A tracking actuator to be moved; tracking control means for correcting the positional deviation by driving the tracking actuator in accordance with the tracking error signal; and position detection for detecting a relative position of the objective lens in a direction crossing a track with respect to the optical head. Means for recording and / or reproducing information on / from the optical recording medium. After moving the center of the objective lens to the center position of the light beam serving as the reference position based on the output signal of the position detecting means, the objective lens is slightly vibrated near the reference position, and the tracking at this time is performed. An optical information processing apparatus comprising: means for detecting an offset amount of a tracking error signal from an error signal; and means for correcting the tracking error signal based on the detected offset amount.