JPH0319062Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical pickup device used in an information reading device such as a digital audio disk playback device or a video disk playback device.

[Technical background of the invention and its problems] For example, an optical pickup for optically reading tracks on a recording medium such as a disk is equipped with a focusing mechanism that determines the focal point position and a tracking drive mechanism that determines the scanning spot position. In particular, the configurations shown in FIGS. 2 and 3 have been known as examples for tracking adjustment, in other words, for controlling the pickup light spot position.

That is, in order to accurately track and scan the information track of an optical disk on which high-density recording is being performed, the output of a well-known optical detector that detects tracking deviations is used to finely adjust and control the position of the light spot of the optical pickup. It controls a minute drive unit, a so-called actuator unit, and a feed motor that moves the housing itself equipped with an optical pickup in the tracking direction. An example of the structure is as shown in FIG. 2, which is a rotatable optical disk 1. Tracking direction of optical pickup to scan information track 2
tr, the feed motor 7 engages the rack 4 provided integrally with the pick-up housing 3 to the pinion 5 to move the relative position of the objective lens 6, and on the other hand, the pick-up housing serves as a minute drive unit. An actuator 13 is provided around the objective lens 6 in the lens 3 as shown in FIG.
As shown in the figure, a support mechanism is configured to rotatably support the objective lens 6 together with a focusing drive mechanism (not shown) about a shaft 8 that is installed in the housing, and a tracking coil 10 is wound around a support arm 9.
In addition, magnets 11 and 12 are disposed facing the coil 10, and by exciting the coil 10, the support arm 9 is rotated and the relative position of the objective lens 6 is changed. The actuator 13
follows fast movements such as track eccentricity,
Since the above-mentioned feed motor 7 is used for the resulting relative movement of the housing 3, the position control in the tracking direction is performed by controlling the position of the actuator within the housing 3 by various means related to the structure of the actuator. is detected, and the motor is controlled to move so that the actuator is positioned approximately at the center within the housing.

On the other hand, within the housing, the support arm 9 is held at approximately the center position by an elastic body 14 such as rubber or a spring, as shown in FIG. Generally, a method is used in which f ₀ is detected and the motor 7 is driven so as to be positioned approximately at the center.
The present applicant's patent application states that other actuator structures are more effective because of the disadvantages such as the existence of
It is clear in the application No. 59-37284.

Regarding the structure of such an actuator, the same configuration is as shown in FIG. 4 using the same numbers from FIG.
Although a detailed explanation thereof is omitted, the differential transformer 17 is constructed by winding the coils 15 and 16 with respect to the magnets 11 and 12 so that they are in opposite phases to each other and have approximately the same number of turns. If the tracking coil 10 is used as a primary coil (excitation coil), it is provided as a secondary coil that generates an induced electromotive force corresponding to changes in magnetic flux, and is connected with opposite polarity. A difference in voltage appears due to the relative position of the coil 10 as it is displaced from its position.

A signal outside the racking servo band is superimposed and applied to the coil 10 as a reference signal for detecting the position of the actuator together with the servo signal, and the output of the differential transformer 17 is synchronously detected with the signal outside the band to detect the position of the actuator. Detecting the position within the body.

Therefore, there is no need to provide an elastic body, and the synchronously detected signal is used as a position control signal for the motor 7.

Furthermore, the tracking servo of the actuator 13 and the same direction position control of the housing 3 are in a series servo relationship, and when the tracking servo is locked, the pick-up position changes from the reference position to the right side of the figure as shown in FIG. If the pick-up section is shifted in the direction shown in FIG. .

Such a structure has a great advantage as mentioned above because the mechanical structure related to the tracking drive is simple, but when the actuator is significantly displaced within the housing, for example, before the servo lock is activated, such as when the power is turned on, etc. More specifically, if the drive range corresponding to the amount of disk eccentricity extends outside the actuator movable range, scanning and follow-up cannot be performed, resulting in a problem in which the servo cannot be locked.

Additionally, if an excessive position control signal is applied in relation to the displacement of the initial position, the housing is moved at high speed, and if the tracking actuator's servo exceeds the speed at which it can be captured, the actuator's servo and There have been cases where both the servos that feed the casing have become unable to lock, causing the casing to run out of control.

[Purpose of the invention] The present invention determines whether or not the actuator servo can be locked by monitoring the level of the detection circuit, and also uses the output of the detection circuit as a signal to return the actuator to its reference position. The purpose is to solve problems.

[Summary of the invention] A tracking actuator that is rotatable or swingable within a housing and is electromagnetically driven by a servo signal to finely control the position of a light spot of an optical pickup, and the actuator. A detection circuit that detects the displacement from the reference position within the housing, and an electromagnetic sensor that is rotatable or swingable within the housing, and is electromagnetic by a servo signal to finely control the position of the light spot of the optical pickup. a tracking actuator driven by a tracking actuator, a detection circuit for detecting displacement of the actuator from a reference position within the housing, and an output of the detection circuit for returning the actuator to the reference position. an optical pick-up comprising: a feedback loop for feeding back to the casing; and a transfer means for transporting the casing in a direction in which the output of the detection circuit is inputted as a position control signal for the casing and positions the actuator relative to the reference position. The apparatus includes a level detection circuit for detecting the output level of the detection circuit, supplying a servo signal to the actuator in response to the output from the level detection circuit, opening/closing the feedback loop, and the transfer means. A control circuit for controlling output supply from the detection circuit to the detection circuit.

[Embodiment of the invention] {First embodiment} FIG. 1 shows a first embodiment of the invention, in which the actuator 13 has the configuration shown in FIG. 4 above,
An arithmetic unit 20 is provided to pass an out-of-band signal (reference signal) through an LPF (low-pass filter) 19 and to superimpose it with a so-called servo signal in order to minimize tracking errors. Both terminals of coils 15 and 16, which are connected to the king coil 10 and are disposed facing the coil 10, are connected to a synchronous detection circuit 21, and are provided with an input terminal for a reference signal to be used as the extraction frequency, that is, the detection The circuit 21 extracts only a signal having the same frequency as the above-mentioned reference signal from the differential outputs of the coils 15 and 16 related to the tracking drive as a detection circuit 29 for detecting displacement.

Further, a switch 28 serving as a switching means is provided at the output stage of the detection circuit 21, and the switch 28 connects the detection output to the motor 7 via a driver (not shown) and uses it as a position control signal for the casing. ,
Alternatively, as shown in the figure, a feedback loop from the output stage to the actuator 10 is used to substantially apply the output to the actuator, and it is switched to use it as a return signal to return the actuator to the reference position.

The return signal is provided when the actuator is significantly displaced and the servo cannot be retracted, and its polarity is such that when the signal is applied to the coil 10, the direction from the displaced position is towards the reference position. It is configured to be excited and driven in a direction that approaches the former, and a DC value of opposite polarity is obtained for displacement in the opposite direction.

23 and 24 are phase compensation circuits for preventing oscillation within the loop.

Further, the servo signal applied to the arithmetic unit 20 is provided via a switch 27, and the switch 27 is configured to switch whether or not to apply the servo signal to the arithmetic unit. The switching is controlled by a control circuit 35 constituted by the window comparator 25.

The window comparator 25 has the characteristics shown in FIG. 8, that is, when the input level exceeds ±Vth, an H (high) level is output, and when the input level is low, an L (low) level is output. It is a thing,
In the figure, the output level of the detection circuit 21 is provided as an input, and the output of the window comparator is provided as an input to the timer 26.
given to.

The ±Vth level is set for the displacement of the actuator that causes the above-mentioned problem, and if a value exceeding this level appears, it becomes difficult to pull in the servo with the displacement position as the initial position.

The timer 26 is provided to hold the H level for a certain period of time when the window comparator outputs an H level.If the switch 27 is the switching state of the switches 27 and 28, the servo signal is not applied to the arithmetic unit. If it is 28,
Cut off the servo connection between the actuator and the housing feed,
Keep the return signal applied to the actuator.

On the other hand, the position of the actuator within the housing is obtained from the differential transformer by using a reference signal frequency as a so-called carrier wave, which is amplitude-modulated in relation to the tracking drive. In addition to being extracted from the phase shifter, an output of opposite polarity corresponding to the amount of displacement at the phase-inverted portion, that is, the portion driven in opposite directions from the reference position within the housing of the actuator, is obtained.

The motor is driven by this output as a position control signal.

The detected output extracted from the superimposed signal by synchronous detection has a characteristic corresponding to the amount of displacement at the phase inversion part, that is, the part driven in the opposite direction from the center position of the actuator, as shown in Figure 7, and has the same characteristics. The actuator reference position in the figure has a detection output of 0.
That is, the origin is located at a position within the housing where the magnetic flux from the coil 10 to both coils 15 and 16 is equal.

As a reference signal, the transmission characteristics of the so-called actuator of an optical pickup generally slope downward from the low-frequency resonant frequency _f0 to the high-frequency side due to the secondary vibration characteristics. The high frequency side is set outside the king servo band and corresponds to negligible actuator operation, and even if applied to the coil 10 together with the servo signal, the actual actuator movement due to the reference signal is There is no drive, and the drive of the actuator is controlled by the servo signal that should originally be controlled.

This embodiment is configured as described above.

Next, its operation will be explained.

When the actuator servo is locked and following the track, switches 27 and 28 are in the first position.
It is switched to the L side in the figure, a servo signal is applied to the arithmetic unit 20, and the output of the detection circuit 21 is given to the motor 7, which uses the output as a position control signal for the casing.

However, when locking the actuator servo during power startup or random access,
If the actuator is displaced to a position where the detection output exceeds ±Vth, it will be difficult to lock.

On the other hand, a DC value corresponding to the displacement is about to be applied to the motor 7, but a DC value exceeding the ±Vth level is also input to the window comparator, and the output of the window comparator becomes H level.

The output is transmitted via the timer 26 by switching the switches 27 and 28 to the H terminal side.
The application of the servo signal is then cut off, and the detection output is fed back to the actuator by the switch 28, and is applied as a signal to return the actuator to the reference position.

For this reason, the actuator is driven toward the reference position from a displacement position that cannot be retracted stably by the servo without being supplied with the servo signal, while the housing is not supplied with the position control signal, so it remains the same as before starting to return. stopped in position.

As the actuator displacement gradually shifts from the reference position by switching the switch described above, the detection output also becomes a low level, and the input to the window comparator becomes below the ±Vth level again, but the timer 26 Due to the presence of the switch, the level used for switching the switch remains at the H level for a certain period of time.

That is, the timer 26 is provided as a time constant means for holding the feedback output for a certain period of time in order to engage the servo in a state sufficiently close to the reference position.

Thereafter, when the output from the timer 26 becomes L level, the switches 27 and 28 are switched to the L terminal side, and the actuator is at the reference position or a displacement position very close to the reference position, that is, the detected output can lock the actuator servo. The tracking servo is located at a position where the output is at a low level, and the tracking servo is stably pulled in from this position.

Further, the means for switching the switch 28 to the L side is not limited to the timer, and the switch 28 may be switched to the L side after confirming that the servo of the actuator is locked.

{Second Embodiment} FIG. 9 shows a second embodiment of the present invention. Similarly, the actuator 13 has the configuration shown in FIG. ) 19, and has an arithmetic unit 20 to be superimposed with a so-called servo signal in order to minimize tracking errors, and the output terminal of the arithmetic unit 20 is connected to the above-mentioned tracking coil 10; Coils 15 and 16 that can be arranged
Both terminals of the detector circuit 21 are connected to a synchronous detection circuit 21, and are provided with an input terminal for a reference signal to be used as the extraction frequency.That is, the detection circuit 21 receives the above-mentioned reference signal from the differential output of the coils 15 and 16 related to the tracking drive. The detection circuit 29 that detects displacement extracts only signals having the same frequency as .

Further, a switch 28 is provided at the output stage of the detection circuit 21, and the switch 28 connects the detection output to the motor 7 via a driver (not shown) to use as a position control signal for the housing, or as shown in the figure. A feedback loop returns from the output stage to the actuator 10, and the output is substantially applied to the actuator, and it is switched whether it is used as a return signal to return the actuator to the reference position.

The return signal is provided when the actuator is significantly displaced and the servo cannot be retracted, and its polarity is such that when the signal is applied to the coil 10, the position from which the actuator was displaced changes to the reference position. It is configured to be excited and driven in a direction that approaches the opposite direction, and a DC value of opposite polarity is obtained for displacement in the opposite direction.

23 and 24 are phase compensation circuits for preventing oscillation within the loop.

Further, the servo signal applied to the computing unit 20 is provided via a switch 27, and the switch 27 is configured to switch whether or not to apply the servo signal to the computing unit, and the switch 27 is connected to the above-mentioned switch 28. and window comparators 30, 31,
A control circuit 35 is configured together with an inverter 32 and a flip-flop circuit 33.

The window comparator 30 has the characteristics shown in FIG. 10, that is, when the input level exceeds ±Vm, an H (High) level is output, and when the input level is low, an L (Low) level is output. On the other hand, the window comparator 31 has the characteristics shown in FIG.
High when input level exceeds ±Vn level
(high) level is output, and if the level is lower than this, L (low) level is output.

The output level of the detection circuit 21 is input to both of the window comparators, and the output of the window comparator is applied to the flip-flop circuit 33.

In addition, the ±Vm level setting is a value that is set for the displacement of the actuator that causes the above-mentioned problem. becomes difficult.

On the other hand, the ±Vn level setting is shown in Figure 10, 1.
As is clear from the comparison in Figure 1, the absolute value level is set relatively low compared to the ±Vm level, but in the configuration of this embodiment, the level ±Vm
This is because there is a height difference between the two levels to prevent the switching operation from becoming unstable near the
The present invention is not particularly limited to the embodiment, and may be configured to determine the height difference based on the Vm level.

This is based on the output level of the window comparator 30, which determines that it is necessary to move the actuator toward the reference position and return it, and the window comparator 31 determines that the actuator has been displaced to a position where stable servo retraction is possible. This is to judge.

The output terminal of the window comparator 30 is the set input terminal (S terminal) of the flip-flop circuit 33.
The output of the window comparator 31 is connected to the flip-flop circuit 3 via an inverter 32.
The Q terminal output of the flip-flop circuit 33 is used for switching the switches 27 and 28.

The flip-flop circuit 33 is once reset when the power is turned on.

When the Q terminal output is at the L (low) level, the switch 27 is switched to apply a servo signal to the arithmetic unit, while the switch 28 is controlled to apply the detection circuit output to the motor 7 as a position control signal, (high) level, the application of the servo signal is cut off and the detection circuit output is returned to the actuator as a return signal.

Furthermore, as is clear from the above, when the output level provided by the window comparator exceeds the ±Vm level, the H (high) level arrives at the S terminal, and when it goes below the ±Vn level, the H (high) level arrives at the R terminal. The flip-flop circuit has H (high) on the S terminal.
Switches 27 and 28 are switched to the H side by level input, and switches 27 and 28 are switched to the H (high) level to the R terminal.
28 to the L side.

In the embodiment, the control circuit 35 includes a level detection circuit using a window comparator, and the switching of the switch is controlled by the height difference between these levels.

On the other hand, the position of the actuator within the housing is obtained from the differential transformer by using a reference signal frequency as a so-called carrier wave, which is amplitude-modulated in relation to the tracking drive. In addition to being extracted from the phase shifter, an output of opposite polarity corresponding to the amount of displacement at the phase-inverted portion, that is, the portion driven in opposite directions from the reference position within the housing of the actuator, is obtained.

The motor is driven by this output as a position control signal.

The detection output extracted from the superimposed signal by the basic detection has a characteristic corresponding to the amount of displacement at the phase inversion part, that is, the part driven in the opposite direction from the center position of the actuator, as shown in Fig. 7. The actuator reference position in the same figure has a detection output of 0.
That is, the origin is located at a position within the housing where the magnetic flux from the coil 10 to both coils 15 and 16 is equal.

As a reference signal, the transmission characteristics of the so-called actuator of an optical pickup generally slope downward from the low-frequency resonant frequency _f0 to the high-frequency side due to the secondary vibration characteristics. The high frequency side is set outside the king servo band and corresponds to negligible actuator operation, and even if applied to the coil 10 together with the servo signal, the actual actuator movement due to the reference signal is There is no drive, and the drive of the actuator is controlled by the servo signal that should originally be controlled.The present embodiment is constructed as described above, and its operation will be explained next.

When the actuator servo is locked and the recording track is being followed, the switches 27 and 28 are switched to the L side in FIG. 9, the servo signal is applied to the calculator 20, and the output of the detection circuit 21 is It is applied to the motor 7, and its output is used as a position control signal for the casing.

At this point, the detection output level does not exceed the ±Vm level, so the H level output is not input to the S terminal, and when the level falls within the ±Vn level related to driving, the H level output is passed through the inverter 32, so the H level output is not input to the S terminal. If the output is given to the R terminal or when the power is turned on, the flip-flop circuit 33 similarly enters the reset state in connection with the reset operation, the Q terminal output is at the L level, and the switches 27 and 28 are held at the L side. ing.

On the other hand, when the actuator is pulled into the servo from its initial position during power-on or random access, the actuator servo can be locked if the actuator's displacement position is within the housing at least within the ±Vm level. However, if this level is exceeded, the servo cannot be pulled in stably.

If the actuator is displaced beyond the ±Vm level, the output of the window comparator 30 becomes H level, and the flip-flop circuit 3
The H level arrives at the S terminal of No. 3, while the L level exceeds the ±Vn level and is input to the R terminal.

As a result, the flip-flop circuit 33 enters the set state, the Q terminal output becomes H level, the switches 27 and 28 are switched to the H side, the application of the servo signal is cut off, and the detection output is applied to the actuator as a return signal. is driven toward the reference position from a displacement position that cannot be retracted stably by the servo when no servo signal is provided, while the housing stops at the same position as before starting return because the position control signal supply is cut off. There is.

As the actuator is displaced from the reference position by switching the above-mentioned switch, the detection output also becomes a low level, but this level is constantly monitored by the window comparators 30 and 31 and the flip-flop circuit 33. The L level is supplied from the Q terminal, and the switch is switched to the L side again when the actuator returns to the casing displacement position where the level is within ±Vn.

Therefore, the servo is pulled in with the position where the detected output becomes a low level output capable of locking the servo of the actuator as the initial position.

In the second embodiment, in addition to the level at which the return signal is applied, the level at which the tracking servo is drawn from the applied state is detected.
In particular, in cases where the device is used in a vehicle and severe vibrations are expected, even if the initial position is returned, the actuator may jump to a position where it cannot be retracted due to mechanical factors before the servo lock locks, and the timing of the servo lock may be interrupted. Although there is a possibility that the servo may miss, the effect is that the servo can be quickly retracted by monitoring the retractable level.

Also, when switching the switch 28 to the L side,
After confirming that the level is within ±Vn and that the actuator servo is locked,
It may be configured to switch to the side.

Further, in both embodiments, various design changes can be made depending on the situation, and the mechanical structure of the actuator does not have to be a rotating structure as in the embodiments, but may be a swinging structure.

[Effects of the invention] As described above, the optical pickup device of the invention uses the position control signal of the housing to effectively displace the actuator to a position where it can be pulled into the servo, and has a simple configuration. It is possible to stably pull the servo into the servo.

What should be noted is that it includes a control circuit that monitors the level and controls the return of the actuator depending on the difference in output level.

Therefore, a feedback loop is not formed during tracking when a position control signal is provided, that is, a return signal is not applied, and the stability of the tracking servo of the actuator is not disturbed, and the return to the actuator is not performed during tracking. The circuit related to the displacement of the actuator governs effective control without applying additional voltage due to signals and without deteriorating the actuator's movable characteristics, so the circuit design for servo pull-in can be simplified. .

Ultimately, it is possible to actively displace the actuator within the housing by applying a return signal, and regardless of the actuator's displacement state, the return signal can be supplied as a return operation to the offset position depending on the case. However, if the level is monitored and the return is controlled to the minimum necessary level as in the present invention, prompt retraction can be achieved in response to various situations.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of the main part showing the first embodiment of the present invention, Fig. 2 is an explanatory diagram of tracking servo operation, Fig. 3 is a structural diagram of a conventional actuator, and Fig. 4 is an implementation of the present invention. The actuator structure diagram of the example, Figures 5 and 6 are diagrams explaining the servo operation, Figure 7 is the characteristic diagram of the embodiment detection circuit, and Figure 8 is the characteristic diagram of the window comparator in the first embodiment. , No. 9
The figure is a circuit diagram of a main part showing a second embodiment of the present invention, and FIGS. 10 and 11 are characteristic diagrams of a window comparator used in the second embodiment. Explanation of symbols, 3... Housing, 7... Motor, 13
... Actuator, 29 ... Detection circuit, 35 ...
...control circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A tracking actuator that is rotatable or swingable within the housing and that is electromagnetically driven by a servo signal to finely control the position of the light spot of the optical pickup. a yuator, a detection circuit that detects displacement of the actuator from a reference position within the housing, and a feedback loop that feeds back an output of the detection circuit to the actuator in order to return the actuator to the reference position; In the optical pickup device, the optical pickup device includes a transfer means for receiving an output of the detection circuit as a position control signal for the casing and for moving the casing in a direction to position the actuator relative to the reference position. a level detection circuit for detecting the output level of the circuit; and supplying a servo signal to the actuator in response to the output from the level detection circuit, opening and closing of the feedback loop, and supplying a signal from the detection circuit to the transfer means. An optical pickup device comprising: a control circuit for controlling output supply. (2) The optical pickup device according to claim 1, wherein the control circuit feeds back the output of the detection circuit when the output of the detection circuit is above a predetermined level. (3) The optical pickup device according to claim 1 or 2, wherein the control circuit includes time constant means for maintaining the output feedback of the detection circuit for a certain period of time. (4) The control circuit includes a first level detection circuit that detects that the output of the detection circuit is equal to or higher than the first level, and a first level detection circuit that detects that the output of the detection circuit is equal to or lower than the first level. A second level that detects that the level is below a second level.
A level detection circuit according to claim 1 or 2, wherein output feedback of the detection circuit is controlled by the first and second level detection circuits. Optical pick-up device. (5) The optical pickup device according to claim 1, wherein the detection circuit performs position detection by synchronously detecting the differential output based on the tracking operation of the actuator at a predetermined frequency. .