JP2650466B2 - Optical head controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head control device of an optical recording / reproducing apparatus for recording or reproducing a signal on a record carrier surface using a converged light beam.

2. Description of the Related Art A technique of a conventional optical head control device of an optical recording / reproducing apparatus is disclosed in Japanese Patent Publication No. 59-22290. Hereinafter, a conventional example will be described with reference to the drawings. FIG. 2 shows the configuration of a conventional optical head control device.

The light beam 2 emitted from the semiconductor laser 1 is converted into parallel light by the collimator lens 3 and the polarization beam splitters 4 and 1 /
The light is focused on an information track 8 of a record carrier 7 (hereinafter referred to as an optical disk) via a four-wavelength plate 5 and an aperture lens 6. The optical disk 7 is driven and rotated by a motor 13. Next, the light reflected from the surface of the record carrier passes through the stop lens 6 again, becomes parallel light, passes through the quarter-wave plate 5, passes through the polarizing beam splitter 4, and is separated by the mirror 9, and one of the light condensing lenses
It passes through 10 and enters a focus shift detector 11 to constitute a knife-edge detector.

The other light enters the track shift detector 12 to constitute a far-field detector.

The focus shift detector 11 is made of a two-divided PIN diode, and is set so that the same amount of light is incident on each PIN diode when the focal point of the light beam and the vertical position of the optical disk 7 coincide with each other. Have been.

When a position shift occurs between the focal point of the light beam and the surface of the record carrier of the optical disk 7, an imbalance occurs in the amount of light incident on the PIN diode, and unbalanced photocurrents are supplied to the amplifier circuits 14 and 15 provided respectively. The current-to-voltage conversion is performed and amplified by the differential amplifier circuit 34, and the differential amplifier circuit 34 outputs a focus shift signal 35. The focus shift signal 35 passes a current to the focus coil 18 via a gain switching circuit 38, a phase compensation circuit 39 for compensating the phase of the focus control system, and a drive circuit 40 to control the position of the aperture lens 6.

In this way, the focal point of the light beam 2 of about 1 μmφ is controlled with high precision in the direction perpendicular to the recording carrier surface of the optical disk 7 with an error of, for example, ± 0.5 μm or less.

Similarly, the track position is controlled by controlling the focus of the light beam 2 detected by the track shift detector 12 and the information track 8.
The imbalance corresponding to the deviation is amplified by the amplifier circuits 16 and 17 and the differential amplifier circuit 36, and becomes a track deviation signal 37.

The track shift signal 37 passes a current to the track coil 19 via a gain switching circuit 41, a phase compensation circuit 42 for compensating the phase of a track control system, and a driver circuit 43, and moves the aperture lens 6 in a direction perpendicular to the information track 8. Drive to accurately focus the light beam 2 at a pitch of, for example, 1.6 μm and a width of 0.8 μm.
The control is performed so as to follow the information track 8 of m with an error of about ± 0.1 μm.

Here, when an optical disc 7 having a different reflectivity is used, the reflectivity is changed by recording, or the power of the semiconductor laser 1 for recording a signal on the information track 8 is changed, the light beam 2 is changed. Even if the position shift between the light-condensing point and the record carrier surface of the optical disk 7 does not change, the amount of reflected light changes, so that the current flowing through the focus coil changes, the gain of the control system changes, and control becomes unstable.

Similarly, the gain of the track control system changes.

Therefore, conventionally, gain switching circuits 38 and 41 are provided and the adder 44 is provided in accordance with recording and reproduction on the information track 8.
The gain of the control system is switched according to the amount of reflected light detected in step (1).

The pull-in operation of the focus control is to set the comparator level A near the zero point of the S-shaped curve of the focus shift signal as shown in FIG. 4 and close the control loop when passing through the X point which is the comparator level A. Done by

At this time, the gain switching circuits 38 and 41 are not operated when detecting the comparator level A at the time of pulling in the focus control shown in FIG. 4, but are operated after closing the focus loop.

SUMMARY OF THE INVENTION However, in the above-described configuration, an optical disk 7 having a different reflectivity is used, the reflectivity is changed by recording, and a semiconductor laser is used for recording a signal on the information track 8. For example, changing the power of 1 changes the gain of the control system, and correspondingly increasing the control gain within a certain range increases the scale of the gain switching circuit.

For example, the laser power at the time of recording on the optical disc 7 is 15
It is about mW, which is about 1 mW during data reproduction. Considering changes in the reflectance from the optical disk such as aging and dust adhesion, changes in the signals output from the differential amplifier circuits 34 and 36 are easy.
More than 20 cultures.

To make the gain change of the control system due to the change of the light amount from the optical disk to about 1 dB, the number of switching stages of the switching circuit is 25
More steps are required. The gain is switched by converting the output of the adder circuit 44, which is the reflected light amount signal, into a digital signal. However, even if the gain is continuously changed by an analog circuit based on the output signal of the adder circuit 44, the circuit scale becomes large.

In the case of digital control in which a focus shift signal or a track shift signal is converted from analog to digital (hereinafter referred to as AD conversion) and control is performed using digital values, the dynamic range of the input signal to the AD conversion circuit is reduced to reduce the circuit scale. It is required that the digital control unit be small and that the arithmetic processing of the digital control unit be small in order to stabilize the control system.

In view of the above problems, the present invention uses an optical disc 7 having a different reflectivity, changes the reflectivity after recording, or changes the power of the semiconductor laser 1 for recording a signal on the information track 8. Digital control for changing the amplification rate of the focus shift and track shift signals according to the light amount signal, while the input of the focus shift, track shift signal and light amount signal to the AD conversion circuit is within a predetermined range. It is intended to provide an optical head control device which can easily perform the above arithmetic processing.

If the gain switching circuit is not operated at the time of pulling in the focus control, a comparator level corresponding to a change in the amount of light from the optical disk cannot be obtained, and the start point of the focus control shifts, and the desired convergence position shown in FIG. Instead, it is detected at a position beyond the point X. Also, if the gain switching circuit is operated at the time of the focus control pull-in, the focus shift signal is normalized by the light amount signal, so that the position where the light amount signal is small, for example, Y shown in FIG.
The point before the point is detected as the focus control start point.

The present invention has been made in view of the above problems, and even if an optical disk 7 having a different reflectivity is used or a recorded and the reflectivity changes, a stable focus pull-in operation with a constant focus pull-in position based on the compare level is achieved. A possible optical head control device is provided.

Also, in order to accurately obtain a focus shift signal with an AD conversion circuit having a constant input dynamic range, it is necessary to increase the amplification factor. In this case, the starting point changes, the speed cannot be controlled using the S-shaped curve, and a stable pull-in operation cannot be performed.

Means for Solving the Problems In order to solve the above problems, an optical head control device according to the present invention comprises an output signal of a light amount detecting means for detecting a light amount from a record carrier, that is, an optical disk, a focus shift detecting means and a track shift detecting means. A focus shift gain variable means, a track shift gain variable means, and first and second light quantity gain variable means for amplifying or attenuating the light, a focus shift gain variable means, a track shift gain variable means, a first And after changing the amplification factor so that the output signal of the second light intensity amplification variable means becomes a predetermined value, the focus shift amplification rate variable means and the track are changed according to the signal of the first light intensity amplification variable means. In this configuration, the gains of the shift gain changing means and the second light quantity gain changing means are changed.

Further, the convergence position of the light beam is passed through the surface of the record carrier by the focus moving means, and the maximum value of the output signal of the light intensity amplification variable means, or a value near the maximum value is stored in the storage means, and the stored value corresponds to the stored value. When the comparison value is exceeded, the operation of changing the gains of the focus shift gain changing means, the track shift gain changing means, and the light quantity gain changing means is started.

Further, the focus shift means is controlled by the head control means to converge the light beam near a desired position on the record carrier, and then changes in accordance with the output signal of the light quantity amplification rate variable means. The configuration is such that the amplification factor is increased.

According to the present invention, the output of the focus shift detecting means and the track shift detecting means corresponds to the output signal of the light quantity amplification rate varying means which amplifies or attenuates the signal of the light quantity detecting means for detecting the light quantity from the optical disk. By amplifying or attenuating the signal by the focus shift gain changing means and the track shift gain changing means, the input to the AD conversion circuit can be within a predetermined range, and the first and second light quantity gain changing means are provided. After changing the gain so that the output signals of the focus shift gain changing means, the track gain changing means, and the first and second light gain changing means become predetermined values, the first light gain is changed. The head control means increases the focus shift gain variable means, the track shift gain variable means and the second light quantity gain variable means in response to the signal of the variable means. By using a configuration in which the rate is changed, in the arithmetic processing of the head control means, an amplification rate corresponding to the output change of the first light quantity amplification rate variable means can be obtained, and a focus shift signal and a track shift signal corresponding to the light quantity signal can be obtained. The calculation process of the change of the amplification factor of the corresponding focus shift and tracking shift signals becomes easy.

Further, the convergence position of the light beam is passed through the surface of the record carrier by the focus moving means, and the maximum value of the output signal of the light intensity amplification variable means or a value near the maximum value is stored, and a comparison value corresponding to the stored value is stored. Since the gains of the focus shift gain changing means, the track shift gain changing means, and the light quantity gain changing means are changed from when they are exceeded, the starting point of the focus control becomes constant and a stable focus pull-in operation can be performed.

In addition, after the light beam is converged to a desired position on the record carrier, the gain of the focus shift amplification rate variable means is increased, so that during the focus pull-in operation, a pull-in start point of a focus shift signal corresponding to the light amount from the optical disk or At the time of focus control in which an S-shaped curve is detected and a light beam follows the surface of the record carrier, a focus shift signal can be taken in accurately, and stable control can be performed.

Embodiment An optical head control device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration diagram of an optical head control device according to an embodiment of the present invention.

The description of the optical system of the focus shift detecting means and the track shift detecting means is the same as that of the conventional example, and therefore will be omitted.

Amplifying circuits 14 and 15 convert current and voltage of the photocurrent corresponding to the vertical position shift between the focal point of the light beam detected by the focus shift detector 11 and the recording medium surface of the optical disk 7.

The converted signal is differentially amplified by the differential amplifier circuit 20 and becomes a defocus signal.

Focus shift signal variable circuit for focus shift gain
The signal enters the AD conversion circuit 30 via the switching circuit 25 and the switch circuit 29 and is converted into a digital signal.

The converted digital signal is a digital signal processing circuit
After the phase compensation calculation processing is performed in 31, a current is supplied to the focus coil 18 via the drive circuit 32,
Drive.

By driving the aperture lens 6, the convergence position of the light beam is controlled to follow the record carrier surface of the optical disk.

Also, regarding the control of the track position, the position shift signal between the light beam detected by the track shift detector 12 and the information track is voltage-converted with current by the amplifier circuits 16 and 17, and the converted signal is converted by the differential amplifier circuit. At 22, a track shift signal is generated.

The track shift signal enters the AD conversion circuit 30 via the track shift amplification rate variable circuit 26 and the switch circuit 29, and is converted into a digital signal.

The converted digital signal is a digital signal processing circuit
After the phase compensation calculation processing is performed in 31, a current is supplied to the track coil 19 via the drive circuit 33 to drive the aperture lens 6.

By driving the aperture lens 6, the track position of the light beam is controlled to follow the information track of the optical disk.

The output signals of the amplification circuits 14, 15, 16, 17 are added to the addition circuits 21, 2,
Added by 3, 24.

The addition circuit 24 obtains a value proportional to the amount of reflected light from the optical disk 7.

In order to obtain a value proportional to the amount of reflected light, the outputs of the amplifier circuits 14, 15, 16, 17 are added here.
It is obtained as a configuration for performing the addition of 14, 15 or the addition of the amplification circuits 16, 17.

A digital signal processing circuit 31 controls a switch circuit 29, and through an AD conversion circuit 30, a focus shift amplification rate variable circuit 25, a track shift amplification rate variable circuit 26, and first and second light quantity amplification rate variable circuits 27 and 28. Are sequentially taken in.

Digital signal processing circuit 31 according to the captured data
Controls the amplification factors of the amplification factor variable circuits 25, 26, 27, and 28 so that a predetermined value is obtained.

FIG. 3 shows an example of the configuration of the variable amplification factor circuit. The input signal enters a resistance circuit 47, a signal having a predetermined voltage division ratio is obtained by a switch circuit 45, and is output via an amplifier circuit 46. Selection of switch circuit 45 is digital signal processing circuit
This is performed by a switch switching signal 48 from 31.

The digital signal processing circuit 31 has an input to the AD conversion circuit 30 that is a focus shift amplification rate variable circuit 25, a track shift amplification rate variable circuit 26, and first and second light quantity amplification rate variable circuits 27 and 28.
Are controlled so as to fall within a predetermined range.

FIG. 5 shows an example of the configuration of the digital signal processing circuit 31.

Digital signal processing circuit is input circuit section 49, output circuit section
52, a DSP 53, which is a signal processor with a built-in multiplier as an arithmetic unit, a ROM 50 of a memory for storing instructions for operating the DSP, and a RAM 51 for storing data, and input and input data of digital signals from the AD conversion circuit 30 , Output to the drive circuits 32 and 33, and output for control of the amplification factor variable circuit and the switch circuit 29.

The DSP 53 may be constituted by a microcomputer or a dedicated digital circuit.

 The operation of the variable gain circuit will be described with reference to FIG.

FIG. 6 (a) shows an example of the input signal. The operation of the amplification factor variable circuits 25, 26, 27, 28 when the voltage is constantly increased or decreased from the initial voltage I to the maximum voltage J is shown in FIG. These are shown in FIGS.

The gain of the first variable light quantity amplification circuit 27 is equal to or less than a value obtained by dividing the maximum output voltage L of the gain variable circuit determined by the input dynamic range of the AD conversion circuit 30 by the predetermined input voltage J. Since the main factor in which the maximum voltage J changes is a change in the laser power during recording, the amplification factor is set in consideration of the change in the laser power. In FIG. 6B, the output with respect to the initial input voltage I is K.

The amplification factor of the first light intensity amplification variable circuit 27 is set in an initial state, for example, when the apparatus is started up or in a reproduction state, and is fixed at the time of recording or erasing data.

Therefore, the output voltage of the first light intensity amplification variable circuit 27 changes linearly with respect to the input voltage.

FIG. 6C shows the operation of the focus shift, track shift and the second light quantity amplification rate variable circuits 25, 26, and 28.

The amplification factor is selected so that the output voltage with respect to the initial input voltage I falls within the output voltage range N, and the initial output voltage becomes M.

When the input voltage increases as shown in FIG. 6 (a), the amplification factor does not change from the point E to the point F, but when the input voltage exceeds the point F, the amplification factor is switched. When the input voltage further increases, the gain is switched by the digital signal processing circuit 31 at point G. The switching point is stored in the digital signal processing circuit 31 and is controlled by comparing with the output of the first light intensity amplification variable circuit 27. When the input signal decreases as shown in FIG. 6 (a), G 'having a predetermined hysteresis,
The amplification factor is switched at point F '.

In this manner, the focus shift signal, the track shift signal, and the amplification factors of the second light quantity amplification rate variable circuits 25, 26, and 28 are controlled by the open control, and the output is input to the AD conversion circuit 30 within a predetermined range.

In FIG. 6, points F, G, F 'and G' are set as switching points, but the output signal range N can be set optimally by providing more switching points.

The digital signal processing circuit 31 controls the switch circuit 29, and sequentially outputs the output signals of the focus shift amplification rate variable circuit 25, the track shift amplification rate variable circuit 26, and the second light quantity amplification rate variable circuit 28 via the AD conversion circuit 30. The output of the take-in / focus shift amplification rate variable circuit 25 and the output of the track shift amplification rate variable circuit 26 are connected to a second light quantity amplification rate variable circuit 28.
Divide by the output of.

A phase compensation calculation process is performed on the divided value, a current is supplied to the focus coil 18 and the track coil 19 through the drive circuits 32 and 33, the aperture lens 6 is driven, and the focus position of the light beam is changed to the surface of the record carrier of the optical disc. And the track position of the light beam is controlled to follow the information track of the optical disk.

In this way, even if the reflectivity of the optical disk changes or the power of the semiconductor laser changes, FIG.
As shown in (5), since the input voltage to the AD conversion circuit 30 changes within a predetermined range, calculation can be performed with high accuracy, and stable control can be performed.

In the focus pull-in operation, the comparator level B is set in the light amount signal as shown in FIG.

The comparison level B is such that a current flows through the focus coil 18 to move the aperture lens 6 so that the convergence position of the light beam passes through the surface of the record carrier of the optical disk. Is a value obtained by multiplying the ratio.

Next, a current is applied to the focus coil in the reverse direction, and the digital signal processing circuit detects that the comparison level B has been exceeded.
At this time, the gain of the focus shift gain variable circuit 25, the track shift gain variable circuit 26, and the first and second light quantity gain variable circuits 27 and 28 is changed.

Also, the digital signal processing circuit 31 normalizes the focus shift signal output from the focus shift amplification rate variable circuit 25 with the light quantity signal so that even when the light quantity from the optical disc changes at the time of focus pull-in, the comparator level which is the focus control start point. A does not change, and stable focus pull-in is performed.

 FIG. 8 shows a flowchart.

(1) The focus moving means is driven to bring the convergence position of the light beam closer to the optical disk, and the maximum signal of the light intensity amplification variable circuit is stored in the RAM 51 of the digital signal processing circuit.

(2) The comparison level B of the comparison value is calculated from the data stored in the RAM 51.

(3) By driving the focus moving means, the convergence position of the light beam is set slightly away from the optical disk.

(4) The output signal of the light intensity amplification variable circuit is compared with the comparator level B. If the output signal is large, the process returns to (5). If the output signal is small, the process returns to (3).

(5) Amplification rate variable processing of the light quantity amplification rate variable circuit, the focus shift amplification rate variable circuit, the track displacement amplification rate variable circuit, and normalization of the focus shift and the track displacement signal based on the output of the light quantity amplification rate variable circuit.

Also, the comparator level for starting the change of the amplification factor of the focus shift amplification ratio variable circuit 25, the track shift amplification ratio variable circuit 26, and the first and second light amount amplification ratio variable circuits 27 and 28 is as shown in FIG. 7B, the convergence position of the light beam is brought closer to the optical disk as shown in FIG. 7B, and the peak value D is detected. When the convergence position of the light beam is separated from the optical disk, the peak value D is proportional to the peak value D. The focus control start point does not change even when the amount of light from the optical disk changes even when the comparison level C is exceeded, and stable focus pull-in can be performed.

Further, after performing the operation of drawing the convergence position of the light beam to the record carrier surface of the optical disk, the amplification factor of the focus shift amplification variable variable circuit 25 that is changed corresponding to the output of the light intensity amplification variable circuit 28 is increased, When the convergence position of the light beam is controlled to follow the optical disk record carrier surface, a focus shift signal is accurately taken in, thereby enabling stable control.

 FIG. 9 shows a flowchart.

(1) The variable gain operation of the variable light quantity amplification circuit, the variable focus shift gain circuit, and the variable track shift gain circuit is started.

(2) The focus pull-in operation is completed.

(3) Increase the gain of the variable-focus-amplification-variable circuit with respect to the output of the variable-light-amplification-variable circuit. As a result, the accuracy of capturing the focus shift signal into the digital signal processing circuit is increased, and stable focus control is enabled.

(4) A track pull-in operation is performed. The convergence position of the light beam is made to follow the information track position of the optical disk.

(5) The variable gain operation of the first and second light quantity variable gain circuits is started.

Even if step (5) in the flow shown in FIG. 9 is performed before step (4), the normalization calculation processing performed while changing the amplification factor of the focus shift and track shift signals due to the light amount signal is easy.

The start of the amplification variable operation of the first and second light quantity amplification variable circuits is performed in (5), but may be performed in the state of (1). In this case, the initial amplification factors of the first and second light intensity amplification variable circuits are obtained from the maximum value of the light intensity signal obtained during the focus pull-in operation.

Effect of the Invention As described above, the present invention has two systems of light amount amplification rate variable means, one of which is adapted to the output change of the semiconductor laser, and the other is
By corresponding to the input of the AD conversion circuit, normalization of the focus shift signal and the track shift signal by the light amount signal can be performed with high accuracy by a small-scale digital signal processing circuit and simple processing.

Further, the convergence position of the light beam is passed through the record carrier surface by the focus moving means, and the maximum value of the output signal of the light intensity amplification variable means or a value near the maximum value is stored. By adopting a configuration in which the gains of the shift gain variable means, the track shift gain variable means, and the first and second light quantity gain variable means are changed,
The comparator level for determining the start position of the focus control is limited without being affected by the change in the amount of light from the optical disk, and the start point of the focus control becomes constant, so that a stable focus pull-in operation can be performed.

Also, by changing the amplification factor of the focus shift variable gain circuit with respect to the output of the light quantity variable gain circuit during focus pull-in operation and focus control, focus pull-in is stabilized, and digital processing of the focus shift signal during focus control is performed. Increases the accuracy of taking in the circuit and enables stable control.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical head control device in one embodiment of the present invention, FIG. 2 is a block diagram of an optical head control device in a conventional example, FIG. 3 is a block diagram showing an example of an amplification factor variable circuit, 4 is a waveform diagram showing an example of a focus shift signal and a light amount signal, FIG. 5 is a block diagram showing an example of a digital signal processing circuit, FIG. 6 is a characteristic diagram showing an example of input / output characteristics of an amplification factor variable circuit, FIG. 7 is a waveform diagram showing a focus shift signal when the light beam convergence position is moved toward and away from the optical disk, and FIGS. 8 and 9 are flowcharts for explaining an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 7 ... Optical disk, 11 ... Focus shift detector, 12 ... Track shift detector, 25 ... Focus shift amplification rate variable circuit, 27, 28 ... First and second light quantity amplification Variable rate circuit, 30 AD converter circuit, 31 Digital signal processing circuit.

Claims (3)

(57) [Claims] 1. A light beam irradiating means for irradiating a light beam to a record carrier, a focus shift detecting means for detecting a convergence state between the record carrier and the light beam, and an information track formed on the surface of the record carrier. Track deviation detecting means for detecting a positional deviation from the light beam; light amount detecting means for detecting the light amount from the record carrier; and focus movement for driving the light beam irradiating means in a direction substantially perpendicular to the record carrier surface. Means, a track moving means for driving the light beam irradiation means in a direction substantially perpendicular to the information track, a focus shift amplification rate variable means for amplifying or attenuating an output signal of the focus shift detection means, and the track shift detection Means for amplifying or attenuating the output signal of the means, and means for amplifying or attenuating the output signal of the light quantity detecting means. A second light quantity amplification rate variable means, and the focus movement means and the track movement means are controlled by outputs of the focus shift amplification rate variable means, the track shift amplification rate variation means, and the first and second light quantity amplification rate variable means. A head control unit, wherein the head control unit divides an output of the focus deviation amplification ratio variable unit and an output of the track deviation amplification ratio variable unit by an output of the second light amount amplification ratio variable unit. Setting the amplification factor of the first light quantity amplification rate variable means to an amplification rate that amplifies or attenuates the output signal of the light quantity detection means to the maximum voltage allowed by the head control means; The output of the second light quantity amplification rate variable means, the output of the focus shift amplification rate variable means, and the track shift amplification rate variable in accordance with the output signal of the rate variation means. Change in the output stage alters the respective amplification factor to a predetermined range, the optical head control device and controls the focus movement unit and the track moving means at the output of the means for dividing. 2. The head control means includes storage means for storing a maximum value or a value near the maximum value of an output signal of the first light quantity amplification rate variable means, further controlling the focus moving means, By moving the light beam irradiation means,
The light beam and the record carrier are passed through a desired convergence position, and the maximum value of the output signal of the first light amount amplification rate variable means at a predetermined amplification rate or a value near the maximum value is stored in the storage means. After storing, the light beam irradiating means is moved again to pass a desired convergence position between the light beam and the record carrier, and the output of the first light quantity amplification rate changing means is stored in the storing means. 2. The optical head control device according to claim 1, wherein the amplification factors of the focus shift amplification factor varying means and the second light quantity amplification factor varying means are changed from when a comparison value corresponding to the value is exceeded. . 3. The head control means controls the focus moving means to converge the light beam near a desired position on the record carrier, and then performs an operation of increasing the amplification factor of the focus deviation amplification factor variable means. The optical head control device according to claim 1, wherein the control is started.