JPH04345926A - Optical head controller - Google Patents

Abstract

PURPOSE:To attain the stable digital control of an optical head by keeping the input signals applied to an A/D converter in a prescribed range despite the change of the light quantity reflected from an optical disk due to the recording and erasing operations, etc., and therefore maintaining the accuracy of a digital signal. CONSTITUTION:The maximum value of output of a 1st light quantity amplification factor varying means 27 is detected for a prescribed period so that the output of the means 27 is equal to a prescribed level when a light beam follows an information track. A digital signal processing circuit 31 calculates and varies an amplification factor so as to secure the prescribed value. Then the amplification factors of a focus error amplification factor varying means 25 and a track error amplification factor varying means 26 are increased or reduced in response to the increase or the reduction of the amplification factor calculated by the circuit 31. Thus the input applied to an A/D converter 30 is kept within a prescribed range. Then the stale digital control is attained without deteriorating the accuracy of the digital value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head control device for an optical recording/reproducing device that records or reproduces a signal on a record carrier surface using a converged light beam. be. 2. Description of the Related Art A conventional technology for an optical head control device for an optical recording/reproducing apparatus is described in Japanese Patent Publication No. 59-22290. A conventional example will be described below with reference to the drawings. FIG. 2 shows the configuration of a conventional optical head control device. A light beam 2 emitted from a semiconductor laser 1 is converted into parallel light by a collimator lens 3 and is focused on an information track 8 of a record carrier 7 (hereinafter referred to as an optical disk) via a polarizing beam splitter 4, a quarter-wave plate 5, and an aperture lens 6. be illuminated. Optical disk 7 is motor 1
3 and rotates. Next, the light reflected from the record carrier surface passes through the aperture lens 6 again and becomes parallel light.
The light passes through the /4 wavelength plate 5, passes through the polarizing beam splitter 4, and is separated by the mirror 9, and one passes through the condenser lens 10 and enters the defocus detector 11, forming a knife-edge type detector. The other light enters the track deviation detector 12, which constitutes a far field type detector. [0004]The focus shift detector 11 has a two-part PIN.
The PIN diodes are made of diodes, and are set so that the same amount of light is incident on each PIN diode when the focal point of the light beam and the recording carrier surface of the optical disk 7 are aligned in the vertical direction. When a positional shift occurs between the focal point of the light beam and the recording carrier surface of the optical disk 7, an imbalance occurs in the amount of light incident on the PIN diode, and an unbalanced photocurrent is generated in each amplifier circuit 14. , 15, and is amplified by the differential amplifier circuit 34, and the differential amplifier circuit 34 outputs a focus shift signal 35. This focus shift signal 35 causes a current to flow through 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 having a diameter of approximately 1 μm is controlled in the direction perpendicular to the record carrier surface of the optical disk 7 with high precision, for example, with an error of ±0.5 μm or less. Similarly, in controlling the track position, the imbalance caused by the deviation between the focal point of the light beam 2 detected by the track deviation detector 12 and the information track 8 is detected by the amplifier circuits 16 and 17 and the differential amplification. It is amplified by a circuit 36 and becomes a track deviation signal 37. The track deviation signal 37 causes a current to flow through the track coil 19 through a gain switching circuit 41, a phase compensation circuit 42 for compensating the phase of the track control system, and a drive circuit 43, and causes the aperture lens 6 to move relative to the information track 8. Drive in the vertical direction to accurately set the focal point of the light beam 2, for example, at 1
．． The information track 8 is controlled to follow an information track 8 having a pitch of 6 μm and a width of 0.8 μm with an error of approximately ±0.1 μm. [0009] Here, optical discs 7 having different reflectances may be used, the reflectance may change upon recording, or the semiconductor laser 1 may be used to record signals on the information track 8.
When the power of the focus coil 18 is changed, the amount of reflected light changes even if the positional deviation between the focal point of the light beam 2 and the recording carrier surface of the optical disk 7 does not change, so the current flowing through the focus coil 18 changes, causing a change in the control system. The gain changes and control becomes unstable. Similarly, the gain of the track control system changes as well. Therefore, conventionally, the gain switching circuit 38,
41 is provided, and according to recording and reproduction on the information track 8,
Alternatively, the gain of the control system is switched depending on the amount of reflected light detected by the adder 44. [0012] However, with the above configuration, optical disks 7 with different reflectances are used, the reflectance changes due to recording, and signals are not sent to the information track 8. When the power of the semiconductor laser 1 is changed for recording, the gain of the control system changes greatly.
Correspondingly, if a control gain is to be controlled within a certain range, there is a problem in that the scale of the gain switching circuit becomes large. For example, the laser power when recording on the optical disk 7 is about 10 mW, and when reproducing data, the laser power is about 1 mW.
It will be about. Considering changes in reflectance from the optical disk due to aging, dust adhesion, etc., the change in the signals output from the differential amplifier circuits 34 and 36 can easily be 20 times or more. [0014] 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, in order to reduce the circuit scale of the AD conversion circuit, the number of digital conversion bits is In order to stabilize the control system, it is required that the digital value precision of the focus shift signal or track shift signal to the digital control unit is not impaired. [0015] Therefore, in view of the above-mentioned conventional problems, the present invention solves the following problems:
Even if optical discs with different reflectances are used, the reflectance changes due to recording, or the power of the semiconductor laser changes to record signals on the information track, the input to the AD conversion circuit will be It is an object of the present invention to provide an optical head control device in which the digital value accuracy of a focus shift signal or a track shift signal to a digital control unit is not impaired by keeping the value within a predetermined range. Means for Solving the Problems The optical head control device of the present invention amplifies or Attenuating focus shift amplification factor variable means, track shift amplification factor variable means, first and second light amount amplification factor variable means, focus shift amplification factor variable means, track shift amplification factor variable means, and first and second light amounts. a head control means for controlling the focus moving means and the track moving means from the output of the amplification factor variable means, and when the light beam follows the information track by the head control means, the output of the first light amount amplification factor variable means is set to a predetermined value. The maximum value of the output of the light intensity amplification factor variable means is detected for a predetermined period so that the value becomes the value, and the amplification factor is changed so that the value becomes the predetermined value. In response to an increase or decrease in the output of the variable means, the amplification factors of the focus shift amplification factor variable means, the track shift amplification factor variable means, and the second light amount amplification factor variable means are decreased or increased, and the second light amount amplification is performed. In response to the increase or decrease in the output of the ratio variable means, the outputs of the focus shift amplification factor variable means and the track shift amplification factor variable means are decreased or increased, and the focus moving means and the track moving means are controlled by the head control means. It is configured to do this. [Operation] With the above-described configuration, the present invention adjusts the output of the light amplification factor variable means so that when the light beam follows the information track, the output of the first light amplification factor variable means becomes a predetermined value. detects the maximum value of for a predetermined period, changes the amplification factor so that the detected value becomes a predetermined value, and adjusts the amplification of the focus deviation amplification factor variable means and the track deviation amplification factor variable means in response to an increase or decrease in the amplification factor. AD by increasing or decreasing the rate
After setting the input to the conversion circuit within the specified range and setting the amplification factor,
Decreasing and increasing the amplification factors of the focus deviation amplification factor variable means, the track deviation amplification factor variable means, and the second light intensity amplification factor variable means in response to the increase and decrease in the output of the first light intensity amplification factor variable means; and decreasing the outputs of the focus shift amplification factor variable means and the track shift amplification factor variable means in response to the increase or decrease in the output of the second light amount amplification factor variable means;
The focus moving means and the track moving means are controlled by the head control means, so that optical disks with different reflectances are used, the reflectance changes by recording, and signals are recorded on the information tracks. Therefore, even if the power of the semiconductor laser changes, the precision of the digital value of the focus shift signal or track shift signal to the digital control section is not impaired. [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. Descriptions of the optical systems of the focus deviation detection means and the track deviation detection means will be omitted since they are the same as in the conventional example. A photocurrent corresponding to the vertical positional deviation between the focal point of the light beam detected by the focus deviation detector 11 and the recording medium surface of the optical disk 7 is transmitted to the amplifier circuits 14 and 15.
The current is converted into voltage. The converted signal is differentially amplified by a differential amplifier circuit 20 to become a defocus signal. The focus shift signal enters the AD conversion circuit 30 via the focus shift amplification variable circuit 25 and the switch circuit 29, and is converted into a digital signal. After the converted digital signal is subjected to loop gain adjustment, phase compensation processing, etc. in a digital signal processing circuit 31, a current is applied to the focus coil 18 via a drive circuit 32 to drive the aperture lens 6. By driving this aperture lens 6, the convergence position of the light beam is controlled to follow the recording carrier surface of the optical disk 7. Regarding the track position control, the positional deviation signal between the light beam and the information track detected by the track deviation detector 12 is converted into current and voltage by the amplifier circuits 16 and 17, and the converted signal is converted into a differential signal. The amplification circuit 22 generates a track deviation signal. The track deviation signal enters the AD conversion circuit 30 via the track deviation amplification factor variable circuit 26 and the switch circuit 29, and is converted into a digital signal. After the converted digital signal is subjected to loop gain adjustment, phase compensation processing, etc. in the digital signal processing circuit 31, a current is applied to the track coil 19 via the drive circuit 33 to drive the aperture lens 6. By driving this aperture lens 6, the track position of the light beam is controlled to follow the information track of the optical disk 7. The output signals of the amplifier circuits 14, 15, 16, and 17 are all added by adder circuits 21, 23, and 24. This adder circuit 24 obtains a value proportional to the amount of light reflected from the optical disc 7. In order to obtain a value proportional to the amount of reflected light, the outputs of the amplifier circuits 14, 15, 16, and 17 are added here. It can also be obtained as a configuration that performs the following. The digital signal processing circuit 31 controls the switch circuit 29 and connects the focus shift amplification factor variable circuit 25, the track shift amplification factor variable circuit 26, and the first and second light amount amplification factor variable circuits via the AD conversion circuit 30. 27
, 28 are sequentially taken in. Depending on the captured data, the digital signal processing circuit 31 converts the amplification factor variable circuits 25, 26, 27, 28 into
The amplification factor is changed and controlled 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 resistor circuit 47, a switch circuit 45 obtains a signal with a predetermined voltage division ratio, and the obtained signal is output via an amplifier circuit 46. The selection of the switch circuit 45 is based on the switch changeover signal 48 from the digital signal processing circuit 31.
done by. In the digital signal processing circuit 31, the input to the AD conversion circuit 30 is the focus shift amplification factor variable circuit 25,
Each of the track deviation amplification factor variable circuit 26 and the first and second light amount amplification factor variable circuits 27 and 28 is controlled to fall within a predetermined range. The operation of the variable amplification factor circuit will be explained using FIG. FIG. 4(a) is an example of an input signal that enters the variable amplification circuit, and it increases constantly from the initial voltage I to the maximum voltage J.
Or when the amplification factor variable circuit 25, 2 is reduced to a constant value
The operations of 6, 27, and 28 are shown in FIGS. 4(b) and 4(c). The amplification factor of the first variable amplification factor circuit 27 is determined by the maximum output voltage L of the variable amplification factor circuit, which is determined by the input dynamic range of the AD conversion circuit 30 at a predetermined input voltage J.
It shall be less than or equal to the value divided by . Since the main factor that changes the maximum voltage J is the change in laser power during recording, the amplification factor is set in consideration of this change in laser power. Figure 4(b)
Here, the output with respect to the initial input voltage I is set to K. The amplification factor of the first variable light amplification factor circuit 27 is set to a predetermined value in the initial state, for example, when starting up the device or in the reproduction state, and is fixed at the time of recording or erasing data. I'll keep it. Therefore, the output voltage of the first variable amplification factor circuit 27 varies linearly with the amount of reflected light. FIG. 4(c) shows focus deviation, track deviation, and the operation of the second light amount amplification factor 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 is M.
becomes. When the input voltage increases as shown in FIG. 4(a), the amplification factor does not change from point E to point F, but when it exceeds point F, the amplification factor is switched. When the input voltage increases further, G
The amplification factor is switched at the point. The switching point is stored in the digital signal processing circuit 31, and is controlled by comparing it with the output of the first variable amplification factor circuit 27. Further, when the input signal decreases as shown in FIG. 4(a), the amplification factor is switched at points G' and F' with a predetermined hysteresis. In this way, the focus shift signal, the track shift signal and the second light amount amplification factor variable circuits 25 and 26
, 28 are controlled so that the output falls within a predetermined range to the AD conversion circuit 30. In FIG. 4, points F, G, F', and G' are used as switching points, but by providing more switching points, the output signal range N can be optimally set. Although the present embodiment has hysteresis at the switching point, at least the input to the AD conversion circuit can be kept within a predetermined range, and the accuracy of the control input signal is not impaired. In order to improve the accuracy of the control input signal in the AD conversion circuit, the values of the initial voltage K shown in FIG. 4(b) and the initial voltage M shown in FIG. 4(c) are important. The reflected light quantity signal from the optical disk is influenced by the grooves of the information track, and becomes sinusoidal in correspondence with the grooves, as shown in FIG. 5(a). Further, even if the control is performed to follow the information track, the address portion of the optical disc is affected as shown in FIG. 5(b), and the amount of reflected light is reduced. However, the amount of reflected light may increase at the address portion depending on the unevenness of the track of the optical disc that is subject to follow-up control. Therefore, when setting the amplification factor of the first variable light amplification factor circuit 27, the maximum value of the output of the first variable light amplification factor circuit 27 is detected for a predetermined period in the track control state, and based on this maximum value, the maximum value of the output of the first variable amplification factor circuit 27 is detected. Then, the amplification factor that will be the initial voltage K in consideration of the maximum voltage L shown in FIG. 4(a) is calculated and set. Next, based on the calculated amplification factor, the first light amount amplification factor variable circuit 27 and the focus shift amplification factor variable circuit 2
5. Calculate the amplification factor of the variable track deviation amplification factor circuit 26, and set the amplification factor so that it falls within the output voltage range N shown in FIG. 4(c). By doing this, the optimum amplification factor of the light amount amplification factor variable circuit can be set without being influenced by the address section and without causing the maximum voltage value L to exceed the dynamic range of the AD conversion circuit. The maximum value of the output of the first variable amplification factor circuit 27 is detected through a predetermined filter, and the amount of reflected light increases at the address portion in accordance with the unevenness of the track of the optical disk 7 to be tracked. Even in this case, the optimum amplification factor of the light amount amplification factor variable circuit can be set for tracking control without being affected by the address section. The digital signal processing circuit 31 controls the switch circuit 29 and controls the focus shift amplification factor variable circuit 25 , the track shift signal amplification factor variable circuit 26 , and the second light intensity amplification factor variable circuit 28 via the AD conversion circuit 30 . The output signals are sequentially taken in, and the output of the variable focus shift amplification factor circuit 25 and the output of the variable track shift amplification factor circuit 26 are divided by the output of the second variable light amount amplification factor circuit 28 . Based on this value, phase compensation processing etc. are performed, current is applied to the focus coil 18 and the track coil 19 via the drive circuits 32 and 33, the aperture lens 6 is driven, and the focus position of the light beam is adjusted to the optical disk. The track position of the light beam is controlled to follow the information track of the optical disc. By doing this, even if the power of the semiconductor laser changes or the reflectance of the optical disk changes,
As shown in FIG. 4C, since the input voltage to the AD conversion circuit 30 changes within a predetermined range, accurate calculations can be made and stable control can be performed. Further, a focus shift amplification factor variable circuit 25 which is changed by the output of the first light amount amplification factor variable circuit 27
And when the variable accuracy of the amplification factor of the track deviation amplification factor variable circuit 26 is high, the output of the focus deviation amplification factor variable circuit 25 and the output of the track deviation amplification factor variable circuit 26 are used as the output of the second light amount amplification factor variable circuit 28. Even without division, stable control can be performed in which the loop gain does not change even if the reflectance of the optical disc changes. FIG. 6 shows the flow of an embodiment of the present invention. (Step S1) A focus pull-in operation is performed. (Step S2) Perform focus control. (Step S3) A tracking pull-in operation is performed. (Step S4) Tracking control is performed. (Steps S5 and S6) The maximum value of the output of the first variable amplification factor circuit is detected for a predetermined period. (Step S7) The amplification factor of the first light amount amplification factor variable circuit is calculated and set from the maximum value. (Step S8) From the calculated amplification factor of the first variable light amplification factor circuit, the amplification factors of the second variable light amplification factor circuit, focus shift amplification factor variable circuit, and track shift amplification factor variable circuit are converted, calculated, and set. do. (Step S9) An increase/decrease value is calculated from the output of the first variable light amplification factor circuit, and the amplification factors of the second variable light amplification factor circuit, the variable focus shift amplification factor circuit, and the variable track shift amplification factor circuit are increased or decreased. In addition, in response to an increase or decrease in the output of the second light intensity amplification factor variable circuit, calculation processing is performed to decrease or increase the output of the focus shift amplification factor variable circuit and the track shift amplification factor variable circuit, and focus control and tracking control are performed. I do. In the flow shown in FIG. 6, (step S1), (
Step S2), (Step S3), (Step S4)
The amplification factor of each variable amplification factor circuit in focus control and tracking control is set to a predetermined value, and in (step S2) the focus control is performed in response to an increase or decrease in the output of the second variable amplification factor circuit. Focus control may be performed by decreasing or increasing the output of the variable deviation amplification factor circuit, and in (step S4), the track deviation amplification factor may be varied in response to the increase or decrease in the output of the second variable light intensity amplification factor circuit. Tracking control may be performed by decreasing or increasing the output of the circuit. As described above, the present invention changes the amplification factor so that the output of the light amount amplification factor variable means becomes a predetermined value when the light beam follows the information track, and By amplifying or decreasing the amplification factors of the focus shift amplification factor variable means and the track shift amplification factor variable means in response to the increase or decrease of This is to ensure that it is not damaged. After setting the amplification factor, the focus shift amplification factor variable means, the track shift amplification factor variable means, and the second light intensity amplification factor are adjusted in response to an increase or decrease in the output of the first light intensity amplification factor variable means. Decrease or increase the amplification factor of the variable means, and decrease or increase the outputs of the focus shift amplification factor variable means and the track shift amplification factor variable means in response to the increase or decrease in the output of the second light amount amplification factor variable means. By controlling the focus moving means and the track moving means by the head control means, optical disks 7 with different reflectances can be used, the reflectance can be changed by recording, and signals can be recorded on the information tracks. Therefore, even if the power of the semiconductor laser is changed, the digital value precision of the focus shift signal or track shift signal to the digital control section does not change, and stable control can be performed.

[Brief explanation of the drawing]

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 a conventional optical head control device.

FIG. 3 is a block diagram showing a variable amplification factor circuit according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing an example of input/output characteristics of the variable amplification factor circuit in the same embodiment.

FIG. 5 is a waveform diagram showing a convergence position of a light beam and a light amount signal.

FIG. 6 is a flowchart for explaining the above embodiment of the present invention.

[Explanation of symbols]

1 Semiconductor laser 7 Optical disk 11 Focus shift detector 12
Track deviation detector 25 Focus deviation amplification factor variable circuit 27 First light intensity amplification factor variable circuit 28 Second light intensity amplification factor variable circuit 30 AD conversion circuit

Claims (3)

[Claims] 1. A light beam irradiation means for irradiating a light beam onto a record carrier; a defocus detection means for detecting a convergence state of the record carrier and the light beam; and an information track formed on the surface of the record carrier. track deviation detection means for detecting a positional deviation of the light beam; light amount detection means for detecting the amount of light reflected from the record carrier; and driving the light beam irradiation means in a direction substantially perpendicular to the surface of the record carrier. a focus moving means, a track moving means for driving the light beam irradiation means in a direction substantially perpendicular to the information track, an output of each of the detection means of the focus shift detection means, the track shift detection means, and the light amount detection means; Focus shift amplification factor variable means, track shift amplification factor variable means, and light amount amplification factor variable means for amplifying or attenuating signals, respectively; outputs of the focus shift amplification factor variable means, track shift amplification factor variable means, and light amount amplification factor variable means; and a head control means for controlling the focus moving means and the track moving means, the head control means causing the output of the light amount amplification factor variable means to be a predetermined value when the light beam follows the information track. Optical head control characterized in that the amplification factor is changed so that the amplification factor is increased or decreased, and the amplification factors of the focus shift amplification factor variable means and the track shift amplification factor variable means are decreased or increased in response to the increase or decrease in the amplification factor. Device. 2. A light beam irradiation means for irradiating a light beam onto a record carrier, a focus shift detection means for detecting a convergence state of the record carrier and the light beam, and an information track formed on the surface of the record carrier. track deviation detection means for detecting a positional deviation of the light beam; light amount detection means for detecting the amount of light reflected from the record carrier; and driving the light beam irradiation means in a direction substantially perpendicular to the surface of the record carrier. a focus moving means, a track moving means for driving the light beam irradiation means in a direction substantially perpendicular to the information track, an output of each of the detection means of the focus shift detection means, the track shift detection means, and the light amount detection means; a focus shift amplification factor variable means, a track shift amplification factor variable means, and first and second light amount amplification factor variable means for respectively amplifying or attenuating a signal; head control means for controlling the focus moving means and the track moving means based on the outputs of the first and second light intensity amplification factor variable means; The amplification factor is changed so that the output of the first light amplification factor variable means becomes a predetermined value, and after setting the amplification factor, the focus is adjusted in response to an increase or decrease in the output of the first light amplification factor variable means. Decrease or increase the amplification factors of the deviation amplification factor variable means, the track deviation amplification factor variable means, and the second light intensity amplification factor variable means, and in response to the increase or decrease in the output of the second light intensity amplification factor variable means. An optical head control device characterized in that the focus shift means and the track shift means are controlled by decreasing or increasing the outputs of the focus shift amplification factor variable means and the track shift amplification factor variable means. 3. A light beam is made to follow the information track, a maximum value of the output of the first light amount amplification factor variable means is detected for a predetermined period, and the amplification factor is varied so that the detected value becomes a predetermined value. The optical head control device according to claim 2, characterized in that: