JPH04345929A - Optical recording/reproducing device - Google Patents

Abstract

PURPOSE:To ensure the prescribed value for the phase characteristic by applying a standard reference signal to a servo loop, detecting the complex amplitude of the reference signal at a prescribed part of the servo loop with the orthogonal heterodyne detection, and calculating the gain and the phase of a servo system from the detected amplitude and the complex amplitude of the standard reference signal stored previously. CONSTITUTION:A normal optical recording/reproducing device is provided with a digital signal processor 30, a sine wave numerical value table 31 for application of sine waves, an A/D converter 32, a D/A converter 33, a switch 34 which switches the input applied to the converter 32 with an instruction of the processor 30, and a switch 35 which switches the output of the converter 33 with an instruction of the processor 30. Then the gains of the variable gain amplifiers 37, 40 and 43 are switched with the instructions of the processor 30 to an adder 36 which adds together the outputs of a differential amplifier 8 and the switch 35, an adder 39 which adds together the outputs of a differential amplifier 11 and the switch 35, an adder 42 which adds together the outputs of a tracking servo circuit 41 and the switch 35, etc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an optical recording and reproducing method that uses a light source such as a semiconductor laser to optically reproduce information or record and reproduce code information, video and audio information, etc. on a recording and erasable medium. It is related to the device.

0002

2. Description of the Related Art An example of a conventional optical recording/reproducing apparatus will be described below with reference to the drawings. FIG. 8 is a block diagram of a conventional optical recording/reproducing apparatus. As shown in FIG. 1, in a typical optical recording/reproducing apparatus, an information recording/reproducing track 2 is formed on an optical disc 1. The light beam 4 emitted from the laser diode 17 is converted into parallel light by a collimator lens 18, passes through a half mirror 19, is converged into a minute light spot 3 by an objective lens 5, and is irradiated onto the optical disc 1. The reflected light from the optical disk 1 passes through the objective lens 5, is partially reflected by a half mirror 19, and is divided into two by a half mirror 20. half mirror 2
The reflected light that exits 0 passes through the coupling lens 21,
The photodetector 22 and the reproduction signal detector 7 convert it into an electrical information reproduction signal.

[0003] The light passing through the half mirror 20 is divided into two by a half mirror 23. The light reflected by the half mirror 23 passes through the coupling lens 24, is partially blocked by the knife edge 25, enters the two-split photodetector 26, and is detected by the differential amplifier 8 as an electrical focus error signal. A focus servo circuit 9 performs processing such as phase compensation on the focus error signal, and a focus actuator 10 moves the objective lens 5 in a direction substantially perpendicular to the medium surface of the optical disc 1 in accordance with the output of the focus servo circuit 9, thereby changing the light beam 4. Focus servo is performed to focus the focus on the recording medium surface of the optical disc 1.

The light passing through the half mirror 23 passes through the coupling lens 27 and then passes through the two-split photodetector 2.
8 and is converted into an electrical tracking error signal by a differential amplifier 11. A tracking servo circuit 12 performs processing such as phase compensation on the tracking error signal, and a tracking actuator 13 moves the objective lens 5 in a direction substantially perpendicular to the signal recording/reproducing track 2 based on the output of the tracking servo circuit 12 to form a light spot 3. Tracking servo is performed to follow the information recording/reproducing track 2.

The output of the tracking servo circuit 12 is input to a traverse servo circuit 14, subjected to processing such as phase compensation, and outputted.A linear motor 15 is driven in accordance with the output of the traverse servo circuit 14, and fixed to a transfer table 16. Optical head 6 and focus actuator 10
Then, traverse servo is performed to move the tracking actuator 13 in a direction substantially perpendicular to the signal recording/reproducing track 2. The above is the configuration of a general optical information recording/reproducing device.

[0006]

[Problems to be Solved by the Invention] However, in the conventional servo device described above, in order to perform servo stably, an operator uses a frequency characteristic measuring device such as a spectrum analyzer to adjust the focus, tracking, and traverse servo loops. Because the servo gain was set to a predetermined value by measuring the frequency characteristics and adjusting the potentiometers etc. installed to change the gain of each servo signal processing circuit, adjusting the servo gain was time-consuming and Another problem is that when the servo error signal detection sensitivity of the optical head and the characteristics of the actuator and linear motor change due to temperature changes, the gain of the servo loop changes and the servo operation becomes unstable.

[0007]

SUMMARY OF THE INVENTION The present invention provides an optical recording/reproducing apparatus that automatically adjusts the loop gain and phase characteristics of focus servo, tracking servo, and traverse servo to predetermined values.

In order to achieve the above object, the optical recording and reproducing apparatus of the present invention includes a servo error signal detection means for detecting a deviation of a minute spot of a light beam from a control target position, and a servo error signal detection means for detecting a deviation of a minute spot of a light beam from a control target position. servo means for moving to and holding a position; reference reference signal generating means for adding a reference reference signal to the servo loop; means for detecting the complex amplitude of the reference reference signal applied to the servo loop by orthogonal heterodyne detection; calculation means for calculating the phase and/or gain characteristics of the servo loop from the output of the complex amplitude detection means and the complex amplitude of the reference reference signal stored in advance; and adjustment means for changing the phase and gain characteristics of the servo loop. , a control means for instructing the adjustment means according to the output of the calculation means to change the phase and/or gain characteristics of the servo loop to a predetermined value, and determining in advance the value of the sine wave signal or cosine wave signal. It has a configuration that includes a numerical table stored in the table.

[0009]

[Operation] In the servo device of the optical recording/reproducing apparatus configured as described above, while the servo means performs servo based on the servo error signal detected by the servo error signal detection means, the standard reference signal generating means performs servo control. A sine wave standard reference signal of a single frequency is added to the loop, and the signal complex amplitude detection means detects the complex amplitude of the standard reference signal applied within the servo loop by quadrature phase heterodyne detection, and the complex amplitude detection means The phase and gain characteristics of the servo loop are calculated from the output of the servo loop and the complex amplitude of a standard reference signal added to the servo loop stored in advance, and the control means gives instructions to the phase/gain adjustment means according to the calculation output. Set the phase and gain characteristics of the servo loop to predetermined values.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording/reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows a digital signal processor (hereinafter abbreviated as DSP) as the arithmetic control means.
1 is a block diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention using the . In FIG. 1, 1 is an optical disk, 2 is a signal recording/reproducing track, 3 is a light spot, 4 is a light beam, and 5 is a light beam.
is an objective lens, 6 is an optical head, 8 is a differential amplifier, 11
is a differential amplifier, 10 is a focus actuator, 13
is a tracking actuator, 15 is a linear motor,
Reference numeral 16 denotes a transfer table, and the above elements are similar to those described in the conventional embodiment.

30 is a DSP, and 31 is a sine wave numerical value table. 32 is an AD converter, 33 is a DA converter, 34 is a switch that switches input to the AD converter 32 according to instructions from the DSP 30, and 35 is a DA converter 33 according to instructions from the DSP 30.
36 is an adder that adds the output of the differential amplifier 8 and the output of the switch 35; 39 is an adder that adds the output of the differential amplifier 11 and the output of the switch 35; 42 is a tracking servo circuit 41 This is an adder that adds the output of the switch 35 and the output of the switch 35. 37, 40, 4
3 is a variable gain amplifier whose gain is switched according to instructions from the DSP 30; 38 is a focus servo circuit that switches phase characteristics according to instructions from the DSP 30. 41 is a tracking servo circuit that switches phase characteristics according to instructions from the DSP 30. The focus servo circuit 38 and the tracking servo 41 basically have the same circuit configuration.

FIG. 2 shows a specific example of a focus servo circuit and a tracking servo circuit. FIG. 2 shows an example of a servo circuit in which the phase characteristics of the circuit are switched between three types. In FIG. 2, 111, 115, 119 are operational amplifiers, 112, 11
3, 116, 117, 120, 121 are resistors, 114
, 118, 122 are capacitors, switch 123 is DS
The input of the power amplifier 109 is connected to the operational amplifier 1 according to the instruction of P30.
11, operational amplifier 115, and operational amplifier 119. Operational amplifier 111 and resistors 112 and 113
and a phase compensation circuit composed of a capacitor 114, an operational amplifier 115, resistors 116 and 117, and a capacitor 11.
The phase compensation circuit made up of 8 and the phase compensation circuit made up of operational amplifier 119, resistors 120 and 121, and capacitor 122 have characteristics that the gain at the gain intersection frequency of the servo loop is the same and only the phase differs. It is something that you have.

44 is a traverse servo circuit, which is a DSP
The phase characteristics are switched according to the instruction at 30. A specific example of the traverse servo circuit 44 is shown in FIG. FIG. 3 shows an example of a traverse servo circuit in which the phase characteristics of the circuit are switched between three types. In FIG. 3, 130, 135, 139, 143 are operational amplifiers, 131, 132, 136, 137, 140
, 141, 144, 145 are resistors, 133, 134,
138, 142, 146 are capacitors, switch 147
switches the input of the power amplifier 148 to one of the operational amplifier 135, the operational amplifier 139, and the operational amplifier 143 in response to an instruction from the DSP 30. operational amplifier 135 and resistor 136,
137, a phase compensation circuit composed of a capacitor 138, an operational amplifier 139, resistors 140, 141, and a capacitor 142, and an operational amplifier 14.
3, resistors 144, 145, and capacitor 146 have characteristics that the gain at the gain intersection frequency of the servo loop is the same and only the phase differs. A circuit composed of an operational amplifier 130, resistors 131, 132, and capacitors 133, 134 has substantially the same frequency characteristics as the tracking actuator, and is used to estimate the displacement of the tracking actuator from the neutral position.

The operation of the optical recording/reproducing apparatus according to the embodiment of the present invention constructed from the above elements will be explained with reference to FIG. FIG. 5 is a flowchart showing the operation of the DSP 30. First, the operation of adjusting the characteristics of the focus servo will be explained. Switch 34 according to instructions from DSP 30
is connected to the output side of the differential amplifier 8, and the switch 35 is connected to the adder 36 side. With the focus servo, tracking servo, and traverse servo operating, the DS
P30 reads the numerical data of the sine wave waveform from the sine wave numerical value table 31. A specific example of the sine wave numerical value table 31 is a ROM or a RAM. FIG. 7 shows an example when the sine wave numerical value table 31 is composed of 16 pieces of data. Specifically, the numerical value corresponding to rn is set in advance by R.
It is stored in OM or RAM. DSP3
0 can output a sine wave signal by sequentially reading these signals at fixed time intervals and outputting them as analog signals using a DA converter.

The DSP 30 uses r of the sine wave value table 31.
Data is read out in order from 0, multiplied by a predetermined coefficient kf, converted into an analog signal by a DA converter, outputted as a standard reference signal, and added to the focus error signal by an adder 36. The DSP 30 reads the focus error signal d0 that has been digitally converted by the AD converter 32, multiplies it by r0 read from the sine wave value table, and stores it in the memory A.
Assign to ci. Next, the DSP 30 multiplies the read focus error signal d0 by r4 read from the sine wave value table 31 and assigns it to the memory Acr. If N is the number of data for one period of the sine wave signal, then sine wave value table 3
By reading 1 from a position shifted by N/4, a cosine wave signal can be obtained.

Next, after a predetermined time Ts, the DSP 30 reads out the next data r1 from the sine wave value table 31, converts it into an analog signal using a DA converter, and adds it to the focus servo error signal. The DSP 30 reads the focus error signal d1 converted into digital by the AD converter 32, and adds r1 read from the sine wave value table 31 to this.
is multiplied by , and added to the above Acr, and then integrated. Next, the DSP 30 outputs the read focus error signal d1.
is multiplied by r5 read from the sine wave value table 31,
It is added to the Aci and then integrated. The address to read the above operation from the sine wave numerical table 31 is r2,
r3, . . . and r6, r7 < . . . While advancing by 1, read up to r15 of the sine wave value table, then return to r0 and perform calculations K times of a positive number multiple of the period of the sine wave. , integrate the data.

The complex amplitude of the frequency component of the standard reference signal in the focus error signal can be obtained by dividing the accumulated data when the sine wave signal is output for K periods by N×K÷2. The above operation is nothing but quadrature phase heterodyne detection.

Here, since the complex amplitude of the standard reference signal is the value obtained by multiplying the value of the sine wave numerical value table 31 by a predetermined coefficient kf, this is designated as U, and the frequency of the standard reference signal in the detected focus error signal is Letting the complex amplitude of the component be X,
A complex representation Gc of the gain of the servo loop at the frequency of the applied standard reference signal is determined by calculating Gc = X / (U + X). Here, the real part U of the standard reference signal
r is Ur=0×kf, and the imaginary part Ui is Ui=1×kf. The real part Xr of the detected signal is Xr = Ac
r÷(N×K÷2) The imaginary part Xi is Xi=Aci÷(N×K÷2). The gain G is obtained by calculating G=(Gr2+Gi2)(1/2) from the real part Gr and the imaginary part Gi of Gc. In order to match the detected G to a predetermined gain G0 set in advance, the DSP 30 calculates G0/G, provides the G0/G data to the variable gain amplifier 35, and adjusts the gain of the servo loop to a predetermined value. do.

The phase P of the servo loop at the frequency of the added standard reference signal is determined by calculating P=tan-1 (Gi/Gr) using the DSP 30. In order to match the detected phase P to a predetermined phase set in advance, the DSP 30 gives an instruction to the focus servo circuit, and when the measured phase lead is smaller than a predetermined value, the phase compensation circuit with a large phase lead is instructed to perform the measurement. By switching the phase characteristics of the servo loop, when the measured phase lead is larger than a predetermined value, a phase compensation circuit with a smaller phase lead is used, and when the measured phase lead is approximately a predetermined value, the phase compensation circuit is left as is. , the phase characteristic of the servo loop can be adjusted to approximately a predetermined value. Furthermore, P
Alternatively, the shift in the phase characteristics of the servo loop may be determined directly from the value of Gi/Gr without calculating tan-1, and the phase characteristics may be switched.

Regarding tracking servo, DSP3
With the instruction 0, the switch 34 is connected to the differential amplifier 11 and the switch 35 is connected to the adder 39, and the gain and phase characteristics of the servo loop can be adjusted in the same manner as the adjustment of the focus servo. When adjusting the tracking servo, the sine wave numerical table may be the same as that used for adjusting the focus servo, or a different one may be used. Furthermore, by changing the time interval Ts for reading numerical values from the table, it is possible to output a standard reference signal of a different frequency from that used when adjusting the focus servo. Furthermore, the frequency can be changed by thinning out and outputting the values in the sine wave numerical value table 31. Furthermore, by outputting the same data of the sine wave numerical value table 31 multiple times, the frequency of the standard reference signal can be changed. Further, the values of the coefficient kf and the number of repetitions K may be different from the values used when adjusting the focus servo.

Next, an example of the adjustment of the traverse servo in the embodiment of the present invention will be explained with reference to FIG. FIG. 6 is a flowchart showing the operation of the DSP 30 when adjusting the traverse servo. First, according to instructions from the DSP 30, the switch 34 is connected to the output side of the tracking servo circuit 41, and the switch 35 is connected to the adder 42 side. With the focus servo, tracking servo, and traverse servo operating, the DSP 30 sequentially reads data from r0 on the sine wave numerical table 31, multiplies it by a predetermined coefficient kt, and calculates D.
The A converter converts it into an analog signal and outputs it as a reference reference signal, which is added to the tracking drive signal output from the tracking servo circuit 41 in an adder 42 . DS
P30 reads the tracking drive signal d0 that has been digitally converted by the AD converter 32, multiplies it by r0 read from the sine wave value table 31, and assigns it to the memory Aci. Next, the DSP 30 uses the read tracking drive signal d0 to read out r from the sine wave value table 31.
Multiply by 4 and assign to memory Acr.

Next, after a predetermined time Ts, the DSP 30 reads out the data r0 of the sine wave value table 31 again, converts it into an analog signal using a DA converter, and adds it to the tracking drive signal. The DSP 30 reads the tracking drive signal d1 digitally converted by the AD converter 32, multiplies it by r0 read from the sine wave value table 31, adds it to the above-mentioned Aci, and then integrates it. Next, the DSP 30 multiplies the read tracking drive signal d1 by r4 read from the sine wave value table 31, adds it to the Acr, and then integrates it. M
After repeating this several times, the value read from the sine wave numerical value table 31 is incremented by 1, and the same calculation is performed using r1 and r5.

[0023] From now on, the addresses for reading out the repetition explained above from the sine wave value table 32 are r2, r3, . . .
・, again, advance by 1 as r6, r7, etc., and read up to r15 of the sine wave value table 31, and then read r6, r7, etc.
Returning to 0, the calculation is performed K times, which is a positive multiple of the period of the sine wave, and the data is integrated. If the number of data in one cycle of the numerical table is N, and the number of times the same data is output repeatedly is M, then divide the accumulated data when outputting a sine wave for K cycles by N×K×M÷2. As a result, the complex amplitude of the frequency component of the standard reference signal in the tracking drive signal can be obtained. The frequency of the standard reference signal at this time is 1/M of the standard reference frequency when adjusting the focus servo and tracking servo. This frequency is set near the frequency where the gain of the tracking actuator and the gain of the traverse servo are equal. The characteristics of the traverse servo can be adjusted by performing the same calculation and adjustment as when adjusting the focus servo and tracking servo from the detected complex amplitude.

[0024]The gain/phase characteristics change greatly due to temperature changes. Therefore, by adjusting the gain/phase characteristics at predetermined time intervals, it is possible to suppress changes in the characteristics with respect to temperature that change over time. Since the temperature change of the device is large when the device starts operating, it is preferable to perform the adjustment at short intervals when the device starts operating, and to perform the adjustment at longer time intervals after a predetermined time. Furthermore, when a disk is installed, the operating state of the device changes and the temperature of the device changes, so it is better to perform the adjustment at short intervals when the disk is installed, and at longer time intervals after a predetermined time. Further, a temperature measuring means may be provided so that adjustments can be made when the temperature changes.

Since the stability of the servo loop is determined by the frequency characteristics near the gain intersection, it is important to find the characteristics at the frequency points near the gain intersection. Therefore, it is effective to measure the characteristics at a frequency near the gain intersection and with less noise such as the address of the disk. Further, if the frequency of the standard reference signal is set near the gain intersection frequency of the servo loop, the loop gain is approximately 1, so the accuracy of complex amplitude detection and gain calculation of the signal can be improved.

[0026] In the standardized 86 mm magneto-optical disk, there are areas called calibration zones on the inner and outer peripheries, and these positions are positions that have typical characteristics of the recording/reproducing area of the disk. So you can make adjustments here. In addition, for discs that have a recording/playback area and a playback-only area recorded with uneven signals, the gain is measured on the high-density track located on the inner circumference of the disc, and this is used as a representative of the playback-only area.
The gain measured in the calibration zone area may be stored as a typical characteristic of the recording/reproducing area of the disc, and the values may be switched and used for the recording/reproducing area and the reproduction-only area of the disc.

The standard reference signal to be added to the servo loop may be placed anywhere within the servo loop, for example within the servo circuit or after the servo circuit. In addition, by memorizing in advance the characteristics between the point at which the standard reference signal is applied and the point at which the complex amplitude of the standard reference signal added within the servo loop is measured, the point at which the complex amplitude of the signal is measured can be set regardless of the point within the servo loop. The characteristics of the servo loop can be calculated anywhere.

[0028] The complex amplitude is calculated each time the standard reference signal is output for one period, and the variance of the complex amplitude of the standard reference signal in the detected servo loop is determined. By performing measurements until the variance/N becomes equal to or less than a predetermined value, the gain detection accuracy can be kept constant.

Note that the servo circuit may be constructed of a digital filter using a DSP or the like. The gain/phase characteristics at this time can be set by changing the coefficients of the digital filter.

[0030]

[Effects of the Invention] As explained above, the present invention can automatically measure the gain and phase characteristics of a servo loop, adjust the gain and phase characteristics of the servo loop, and adjust the characteristics of the servo loop to a predetermined value. By setting this value, stable servo characteristics can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a specific circuit diagram of a basic focus servo circuit and a tracking servo circuit.

FIG. 3 is a specific circuit diagram of a traverse servo circuit.

FIG. 4 is an explanatory diagram showing a specific numerical example of a sine wave numerical value table.

FIG. 5 is a flowchart showing the operation of the DSP 30 when adjusting focus servo and tracking servo.

FIG. 6 is a flowchart showing the operation of the DSP 30 when adjusting the traverse servo.

FIG. 7 is a block diagram of a conventional optical information recording/reproducing device.

[Explanation of symbols]

30 DSP 31 Sine wave numerical table 36 Adder 37 Variable gain amplifier 38 Focus servo circuit 10 Focus actuator 39 Adder 40 Variable gain amplifier 41 Tracking servo circuit 13 Tracking actuator 42 Adder 43 Variable gain amplifier 44 Traverse servo circuit 15 Linear motor

Claims (7)

[Claims] 1. A servo error signal detection means for detecting a deviation of a minute spot of a light beam from a control target position, a servo means for moving and holding the light spot at a control target position, and a reference reference signal in a servo loop. means for detecting the complex amplitude of the reference reference signal applied within the servo loop by orthogonal heterodyne detection; and a reference reference signal previously stored as the output of the complex amplitude detection means for the signal. calculation means for calculating the phase and/or gain characteristics of the servo loop from the complex amplitude of the servo loop; adjustment means for changing the phase and gain characteristics of the servo loop; It is equipped with a control means for changing the phase and/or gain characteristics of the loop to a predetermined value, and a numerical table in which values of a sine wave signal or a cosine wave signal are determined and stored in advance, and a standard reference signal generation means and a quadrature phase control means are provided. An optical recording/reproducing device that outputs values of sine wave signals and cosine wave signals used in heterodyne detection according to the numerical table described above. 2. The optical recording and reproducing apparatus according to claim 1, wherein the frequencies of the disturbance signal and the sine wave signal and cosine wave signal for orthogonal heterodyne detection are changed by changing the reading time of the numerical table. 3. The frequency of the reference reference signal and the sine wave signal and cosine wave signal for orthogonal heterodyne detection is changed by changing the number of consecutive readings of the same value in the numerical table. Optical recording and reproducing device. 4. The optical recording according to claim 1, wherein data is thinned out and read out from the numerical table at predetermined intervals, and the frequencies of the standard reference signal and the sine wave signal and cosine wave signal for orthogonal heterodyne detection are changed. playback device. 5. The optical recording and reproducing apparatus according to claim 1, wherein the phase and/or gain characteristics of the servo loop are changed to a predetermined value at predetermined time intervals. 6. Changing the phase and/or gain characteristics of the servo loop to a predetermined value at short intervals when the optical recording/reproducing device starts operating, and at longer intervals after a predetermined time. The optical recording/reproducing apparatus according to claim 1, wherein the optical recording/reproducing apparatus performs the recording at intervals. 7. Changing the phase and/or gain characteristics of the servo loop to a predetermined value is performed at short intervals when the disk is mounted, and at longer intervals after a predetermined time. optical recording and reproducing device.