JPH0727701B2 - Tracking servo device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tracking servo device in an information recording disk reproducing device.

BACKGROUND ART In an apparatus for reproducing an information recording disc (hereinafter, simply referred to as a disc) such as a video disc or a digital audio disc, an information reading spot of a pickup should always accurately follow a recording track regardless of eccentricity of the disc. A tracking servo device for controlling is indispensable.

This tracking servo device generates a tracking error signal according to the amount of deviation of an information reading spot with respect to a recording track of the disc in the disc radial direction, and an actuator for biasing the information reading spot in the disc radial direction according to the tracking error signal. Is a so-called closed loop control system in which the position of the recording track is controlled by driving the. Further, in such a servo device, the servo loop is opened (open) during the so-called jump operation for jumping over a track.
In this state, a predetermined acceleration driving force is applied to the actuator, and then a predetermined braking force is applied, and thereafter, the servo loop is closed (closed) at a predetermined timing to perform servo pull-in. However,
There is a problem in that the track may not be accurately jumped to the target track due to variations in the track pitch of the disc or large error components.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a tracking servo device capable of accurately jumping to a target track.

The tracking servo device of the present invention detects the cycle of the tracking error signal at the time of a jump, and applies a predetermined first driving force to the actuator for a predetermined period in response to the jump command, thereby making it possible to divide the target track into a track immediately before and a target track. It is characterized in that the second driving force in the opposite direction to the first driving force is applied to the actuator with a magnitude that increases as the period of the tracking error signal decreases during the period.

EXAMPLES Examples of the present invention will be described below with reference to the drawings.

In the tracking servo apparatus according to one embodiment of the present invention shown in FIG. 1, three beam spots obtained by converging a laser beam, that is, a recording information reading spot S ₁ and a disc of this spot S ₁ are formed. During relative movement, a pair of preceding and following tracking information detecting spots S ₂ and S ₃ are irradiated onto a recording track T of the disc from a pickup (not shown) in a positional relationship shown in the figure. Light reflected by these beam spots enters photoelectric conversion elements 1 to 3 incorporated in the pickup.

The photoelectric conversion element 1 is composed of four light receiving elements which are arranged so as to be divided into four by two straight lines orthogonal to each other on the light receiving surface and which are independent of each other, and the total output of these elements is a reproduction RF (high frequency) signal. Become.

The respective outputs of the photoelectric conversion elements 2 and 3 are supplied to the differential amplifier 4, the difference between the two outputs is detected, and the difference output becomes a tracking error signal. The tracking error signal output from the differential amplifier 4 is supplied to the equalizer amplifier 5 to be subjected to phase compensation, and the drive circuit 7 is supplied via the changeover switch 6.
Is supplied to. The driving circuit 7 applies a driving force corresponding to the input voltage to the actuator 8 to bias the information reading spot S1 in the disk radial direction so that the information reading spot S1 accurately follows the recording track T. From the above,
A tracking servo loop is formed.

On the other hand, capacitor 11, constant current source 12, on-off switch 1
3, 14 and the voltage follower 15 form a charging / discharging circuit 16.
The capacitor 11 is charged when a constant current is supplied from the constant current source 12 through the switch 13, and when the switch 14 is turned on, both ends are short-circuited to discharge the stored charge. The terminal voltage of the capacitor 11 is output via the voltage follower 15. The output of the charge / discharge circuit 16 is supplied to the adder 18 via the inverting amplifier 17, and the adder 18 is further supplied with the offset voltage from the offset voltage generating circuit 19. The output of the adder 18 is connected to one fixed contact of a changeover switch 22 via an on / off switch 21, and also to a changeover switch via a switch 21 and an inverting amplifier 23.
22 is connected to the other fixed contact. An accelerating voltage generating circuit 26 is connected to an input line of the inverting amplifier 23 via an on / off switch 25. Also, this input line is grounded via a resistor 27. The movable contact of the changeover switch 22 is connected to one fixed contact of the changeover switch 6, and the changeover switch 6 selects the output signal of the equalizer amplifier 5 and the signal from the changeover switch 22.

Changeover switch 22 and on / off switches 13, 14, 21, 2
ON / OFF of 5 is controlled according to each signal output from the timing signal generation circuit 28. Timing signal generation circuit
The output of a comparator 29 that compares the tracking error signal with the ground level described above is connected to 28, and a jump command signal and FW are generated according to the key operation of the keyboard 30.
A command signal generation circuit 31 that generates a D / REV command signal is connected. The FWD / REV command signal output of the command signal generating circuit 31 is connected to the changeover switch 6 to control the selection state of the changeover switch 6. Timing signal generation circuit 28
Is formed by, for example, a microcomputer.

Next, a jump operation of one track in the FWD direction in the tracking servo device according to the present invention having such a configuration will be described. First, when the command signal generation circuit 31 generates a jump command signal (a) as shown in FIG. 2 (a) in response to a key operation on the keyboard 30, the timing signal generation circuit 28 is shown in FIG. 2 (b). Reset signal (b) is generated. The reset signal turns on the switch 14 to discharge the electric charge stored in the capacitor 11. At the same time as the jump command signal, the FWD / REV command signal indicating the jump direction is output from the timing signal generation circuit 28 and the changeover switch 22
Is supplied to. The changeover switch 22 selectively outputs the input signal of the inverting amplifier 23 when the jump direction is the FWD direction, and selectively outputs the output signal of the inverting amplifier 23 when the jump direction is the REV direction. When the generation of the reset signal is stopped, the jump switching signal (k) and the first time width pulse (d) are generated. Second
Since the jump change signal shown in FIG. 9 (k) drives the changeover switch 6, the changeover switch 6 outputs the output signal of the changeover switch 22 from the output signal of the equalizer amplifier 5, and the tracking servo loop is opened. The first time width pulse is a pulse having a first predetermined time T _A width as shown in FIG. 2 (d) and is, for example, 0.1 msec. In response to the first time width pulse, the switch 25 is turned on for the first predetermined time, and the acceleration voltage AP is supplied from the acceleration voltage generation circuit 26 to the drive circuit 7 via the switch 25, the switch 22 and the changeover switch 6. The acceleration voltage AP is a voltage that gives the actuator 8 a first driving force. Therefore, the actuator 8 is driven by the drive circuit 7 only during the generation period of the first time width pulse to accelerate and move the information reading spot in the FWD direction. As a result, when the tracking error signal (c) shown in FIG. 2 (c) output from the differential amplifier 4 reaches the ground level (zero cross point), that is, when it reaches the center position of the track, the output of the comparator 29 is output. The level (e) is inverted from the low level to the high level as shown in FIG. 2 (e), and the timing signal generation circuit 28 generates the charge control signal (g) in response to the rise. However, in the case of one track jump and the output level of the comparator 29 is already high level, the charge control signal (g) rises at the fall of the reset signal (b). The charge control signal shown in FIG. 2 (g) turns on the switch 13, so
11 is charged and the terminal voltage (h) of the capacitor 11 gradually rises from the reference level (earth level) as shown in FIG. 2 (h). This terminal voltage is supplied to the inverting amplifier 17 via the voltage follower 15 and the phase is inverted. Inverting amplifier 17
The output voltage of 1 is added to the offset voltage OFS by the adder 18 and converted as shown in FIG. 2 (i).

The information reading spot moves in the FWD direction due to the inertia of the actuator 8 even after the disappearance of the first time width pulse. And
When the information reading spot reaches the center position between the tracks,
In response to the tracking error signal, the output level of the comparator 29 changes from high level to low level as shown in FIG. 2 (e). Timing signal generation circuit by this low level
Since 28 stops generating the charge control signal, the rise of the terminal voltage (h) of the capacitor 11 stops as shown in FIG. 2 (h), and this terminal voltage is a voltage proportional to the high level output period of the comparator 29. Becomes Also, the timing signal generation circuit 28
Generates a second time width pulse by the low level output of the comparator 29. Second time width pulse is a pulse having a second predetermined time T _B width as shown in FIG. 2 (f), for example, 0.05 msec. This second time width pulse is a switch
Since 21 is turned on for the second predetermined time, the output voltage of the adder 18, that is, the positive voltage BP (FIG. 2 (j)) with respect to the negative accelerating voltage AP, is the switch 21, the switch 22, and the changeover switch. It is supplied to the drive circuit 7 via 6. The drive circuit 7 drives the actuator 8 in the direction opposite to the generation period of the first time width pulse for the generation period of the second time width pulse to give the braking force of the actuator 8 to decelerate the movement of the information reading spot in the FWD direction. This braking force changes according to the voltage BP. That is, the charge control signal (g) is generated during the period in which the information reading spot is from the center position of the track to the center position between the tracks, and
The terminal voltage (h) of 11 rises at a predetermined speed. The voltage (i) obtained by inverting the terminal voltage (h) of the capacitor 11 decreases from the offset voltage OFS to the voltage BP at a predetermined speed during that period. The offset voltage OFS corresponds to the voltage at the center position of the tracks, and the voltage BP corresponds to the voltage at the center position between the tracks. Therefore, the voltage BP, which is the voltage that gives the second driving force to the actuator 8, becomes higher as the time taken for the information reading spot to move from the track center position to the track center position is shorter. Since the time length of the information reading spot moving from the center position of the track to the center position between the tracks is proportional to the cycle of the tracking error signal as shown in FIG. 2C, the cycle of the tracking error signal is small. The second driving force is applied to the actuator 8 with an increasing magnitude. The timing signal generation circuit 28 stops the generation of the jump switching signal at the same time when the generation of the second time width pulse is stopped.
As a result, the changeover switch 6 is connected to the equalizer amplifier 5
The tracking servo loop is closed because it is switched to the side.

In the case of jumping n tracks in the FWD direction,
The timing signal generation circuit 28 generates a charge control signal in response to the nth inversion of the output level of the comparator 29 to the high level, and in response to the nth inversion of the output level of the comparator 29 from the high level to the low level. Generate a second duration pulse.

In the case of a track jump in the REV direction, FWD
Since the changeover switch 22 selects the output signal of the inverting amplifier 23 according to the / REV command signal, the voltage AP output from the acceleration voltage generation circuit 26 and the voltage BP output from the adder 18 are phase-inverted by the inverting amplifier 23. Is supplied to the drive circuit 7,
The information reading spot is accelerated and moved in the REV direction.

FIG. 3 shows another embodiment of the present invention. In this tracking servo device, the output signal of the differential amplifier 4 is supplied to the microprocessor 35 via the sampling circuit 33 and the A / D converter 34. Microprocessor
The drive value calculated by 35 is supplied to the drive circuit 7 via the D / A converter 36. Further, the sampling clock pulse is supplied from the microprocessor 35 to the sampling circuit 33, the A / D clock pulse is supplied to the A / D converter 34, and the D / A clock pulse is further supplied to the D / A converter 36. .

Next, the operation of the tracking servo device according to the present invention having such a configuration will be described with reference to the operation flow chart shown in FIG.

The microprocessor 35 first determines whether or not the jump command signal is supplied from the command signal generation circuit 31 (step 51). If the jump command signal is not supplied, the equalizer is calculated and the calculated value is supplied to the D / A converter 36 as the drive value J (step 52). If the jump command signal is supplied, the tracking is performed. The servo loop is opened and it is determined whether the jump direction is the FWD or REV direction from the contents of the FWD / REV command signal (step 53).

When the jump direction is the FWD direction, initialization is performed by setting the calculated value C of the counter T _C equal to 0 (step 54), and the drive value J is set equal to a predetermined value J _AP (<0) and D is set.
It is output to the / A converter 36 (step 55), and 1 is added to the count value C of the counter T _C (step 56). A first driving force is given to the actuator 8 by the driving circuit 7 by the driving value J _AP . Then, it is judged whether or not the count value C is equal to C ₁ (for example, 4) (step 57), and if C ≠ C _1, then
Perform step 55 again. This causes counter T _{C to} be C ₁
The voltage AP is output from the D / A converter 36 until the driving circuit 7 is counted.
And the information reading spot is moved in the FWD direction. If C = C ₁ , the actuator 8 by the drive circuit 7
In order to stop the driving of (1), the drive value J is made equal to 0 and outputted (step 58), and the count value C of the counter T _C is made equal to 0 for initialization (step 59). Next, the count value C of the counter T _C is incremented by 1 (step 6
0), the output value Dn of the A / D converter 34 is read, and it is determined whether or not the output value Dn is smaller than 0 (step 61). Dn ≧
If it is 0, it is determined that the tracking error signal has not reached the zero cross point, and step 60 is executed again, and Dn
If <0, it is determined whether or not the previous output value Dn _{-1 of} the A / D converter 34 is 0 or more (step 62). If Dn _-1 <0, the step 60 is executed again assuming that the tracking error signal has not reached the zero cross point, and if Dn _-1 ≧ 0, the information reading spot accelerates in the FWD direction to move between tracks. Since the tracking error signal has reached the zero cross point due to reaching the center position, it is determined whether or not the count value C of the counter T _C is larger than the predetermined value N (step 6).
3). If C> N, the drive value J is made equal to the predetermined value Jn _{+ 1} and output (step 64). If C ≦ N, it is determined whether or not the count value C is smaller than the predetermined value N (step 6).
Five). If C = N, the drive value J is made equal to the predetermined value Jn and output (step 66), and if C <N, the drive value J is made equal to the predetermined value Jn _-1 and output (step 67). here,
The predetermined values Jn _{+ 1} , Jn, and Jn- ₁ have a relationship of | Jn _{+ 1} | <| Jn | <| Jn- ₁ |. That is, the smaller the count value C of the counter T _C from the time when J = 0 is executed in step 58 to the time when the zero cross point is reached, the greater the braking force.

After setting the drive value J, the count value C of the counter T _C is initialized to 0 (step 68), 1 is added to the count value C (step 69), and the calculated count value C is the predetermined value C ₂ (For example,
It is determined whether or not it is equal to 2) (step 70). C ≠ C ₂
If so, step 69 is executed again, and if C = C ₂ , the drive value J is made equal to 0 to stop braking (step
71). After that, the output value Dn of the A / D converter 34 is sequentially read, and it is determined whether or not the difference between the present output value Dn and the previous output value Dn- ₁ is 0 or more (step 72), and Dn-Dn _{If -1} ≧ 0, the tracking error signal reaches a negative peak voltage and starts to rise, so it is assumed that the target track is reached, the tracking servo loop is closed, the equalizer calculation is performed, and the calculated value is set as the drive value J and D / It is supplied to the A converter 36 (step 52). The microprocessor 35 repeatedly executes the above operation.

If the jump direction is the REV direction, the REV direction jump control process (step 73) is performed, and in this jump control process, the positive and negative values of the predetermined values J _AP , Jn ₊₁ , Jn, and Jn _-1 are reversed. Dn> 0, the information reading spot accelerated in the REV direction and reached the center position between tracks.
Dn _-1 ≤ 0 is detected and D is used for the judgment to close the servo loop.
The description is omitted because it is the same as the case of the FWD direction except that n and Dn ₋₁ are equal to 0 or smaller than 0.

Further, in the above-described embodiment of the present invention, the driving value J for braking is set to three predetermined values Jn _{+ 1} , Jn, according to the calculated value C.
Although it is set to any one of Jn ₋₁ , it is not limited to this and may be set to any of a plurality of values of 3 or more.

EFFECTS OF THE INVENTION As described above, in the tracking servo device of the present invention, the first predetermined amount is applied to the actuator in response to the jump command.
The driving force is applied only for a predetermined period of time, and the magnitude becomes larger as the cycle of the tracking error signal becomes smaller between the track immediately before the target track and the target track.
Since the actuator is provided with the second drive force in the direction opposite to the drive force, it is possible to accurately and stably jump to the target track even for a disc having a track pitch variation or a large error component. Therefore, the picture search of the video disc player, the high-speed reproduction, the music selection operation of the digital audio disc player, and the like become extremely good.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of each part of the apparatus shown in FIG. 1, and FIG. 3 is a block diagram showing another embodiment of the present invention. The figure is a flow diagram showing the operation of the microprocessor in the apparatus of FIG. Description of symbols of main parts 1 to 3 ... Photoelectric conversion element 5 ... Equalizer amplifier 8 ... Actuator 16 ... Charge / discharge circuit 28 ... Timing signal generation circuit

Claims (1)

[Claims] 1. A reference level changes only in accordance with a deviation amount of an information reading spot of a pickup with respect to a recording track of an information recording disk in a radial direction of the disk and only at a central position of the recording track and a central position between adjacent tracks. The pickup has a means for generating a tracking error signal, an actuator for changing the position of the information reading spot in the disk radial direction, and a driving means for driving the actuator, and the pickup of the pickup to a target track in response to a jump command. A tracking servo device for jumping an information reading spot, wherein the driving means detects a cycle of the tracking error signal at the time of jump, and a predetermined first driving force is applied to the actuator for a predetermined period according to the jump command. Giving the target track Means for applying to the actuator a second driving force in a direction opposite to the first driving force and having a magnitude that increases as the period of the tracking error signal becomes smaller between the immediately preceding track and the target track. And a tracking servo device.