JPH0240575Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reproducing apparatus, and more particularly to a recorded information reproducing apparatus that instantly jumps a recorded information detection point across a plurality of recording tracks to enable high-speed reproduction.

A conventional device of this type opens a tracking servo loop in response to a jump command and generates a drive signal for a pick-up, which is a recording information detection point, to jump over two or more adjacent recording tracks at once. By detecting that the pick-up has skipped a predetermined number of two or more recording tracks, the tracking servo loop is closed and the generation of the drive signal is cut off, and the skip command signal is transmitted for a desired period desired by the user. The configuration is such that it occurs periodically to achieve high-speed playback.

However, in conventional playback devices, when the distance the pickup jumps becomes long, the relative moving speed of the information detection point with respect to the recording track during the jump operation changes due to the eccentricity of the recording disk, etc. The required time varied and the lock-in operation of the tracking servo after the jumping operation was completed was unstable. For this reason, the conventional reproducing apparatus has the disadvantage that the high-speed reproducing operation performed by performing the skipping operation within a limited time such as the vertical retrace period becomes unstable.

Therefore, the applicant of the present invention has proposed an apparatus in which the speed of relative movement of the recorded information detection point to the track during the jump operation is kept substantially constant to achieve stable high-speed reproduction operation. A block diagram of the device is shown in FIG. 1. In FIG. 1, three spot lights 2 to 4 obtained by converging a laser beam onto a recording track 1 are irradiated with the positional relationship shown in the figure. has been done. That is, when the information detection spot light 2 is on the recording track 1, the other two spot lights 3 and 4 are located on both side edges of the recording track 1. Therefore, when the detection spot light 2 shifts in the direction perpendicular to the track (radial direction of the recording disk), both the spot lights 3 and 4
The difference in the amount of reflected light corresponds to the direction of the shift and its magnitude. The reflected lights of both spot lights 3 and 4 are converted into electrical signals by photoelectric conversion elements 5 and 6, respectively. Each output of these photoelectric conversion elements 5 and 6 is supplied to a differential amplifier 7. The differential amplifier 7 outputs a signal corresponding to the level difference between the outputs of the photoelectric conversion elements 5 and 6, that is, a signal corresponding to the difference in the amount of reflected light of the spot lights 3 and 4. The output of this differential amplifier 7 is sent as a tracking error signal to an equalizer amplifier 9 via a loop switch 8.
is supplied to perform phase compensation. The output of this equalizer amplifier 9 passes through an adder 10 and becomes an input to a drive amplifier 11. A tracking mirror 12 that uses the output of the drive amplifier 11 to shift the spot lights 2 to 4 in a direction perpendicular to the recording track 1.
The drive coil 13 is driven, and the information detection spotlight 2 is controlled so as to accurately track the recording track. Note that the loop switch 8 is configured to be in an open state when a high level signal is supplied to the control input terminal.

The above-described portions form a tracking servo loop, and the mirror 12 and drive coil 13 form a tracking actuator. Further, the DC component of the output of the drive amplifier 11 is extracted by a low-pass filter (not shown) or the like, and then sent to a slider motor drive circuit (not shown) for moving the tracking mirror 12 in a direction perpendicular to the track. Supplied. loop switch 8
The Q output a of the R-S flip-flop 15 and the output b of the track detection circuit 16 are supplied to the control input terminal of the circuit via an OR (logical sum) gate 14. A jump command signal is supplied to the set input terminal of the R-S flip-flop 15 from a high-speed reproduction operation control circuit (not shown) or the like. The Q output a of this R-S flip-flop 15 is also supplied to a drive signal generation circuit 17. The track detection circuit 16 also generates a signal corresponding to the sum of a signal obtained by removing the RF component from the information detection output obtained by the information detection spot light 2 and each output of the photoelectric conversion elements 5 and 6. The information detection spot light 2 is compared in level and outputs an on-track signal consisting of a low level signal when the information detection spot light 2 is present on the recording track. The output b of this track detection circuit 16 is
Presettable down as position detection means
It is also supplied to a clock input terminal of a counter (hereinafter abbreviated as counter) 18 and a drive signal generation circuit 17. Data N corresponding to the distance from the information detection spot light 2 to the target track is supplied to the load input terminal of the counter 18 from the high-speed reproduction operation control circuit etc. when a jump command signal is generated. Preset. Data indicating the count value of the counter 18 is supplied to a zero detection circuit 19 and a four-track detection circuit 20. The zero detection circuit 19 is configured to output a zero detection signal consisting of, for example, a high level signal when the supplied data becomes zero.
The zero detection signal output from the zero detection circuit 19 is supplied to the reset input terminal of the R-S flip-flop 15. Further, the 4-track detection circuit 20 is configured to output a 4-track detection signal c consisting of, for example, a high level signal when the supplied data becomes 4 or less. 4-track detection signal c output from this 4-track detection signal
is supplied to the drive signal generation circuit 17.

In the drive signal generation circuit 17, the output b of the track detection circuit 16 is input to the trigger input terminal of a monostable multivibrator (hereinafter abbreviated as monostable multi) 21 and one input terminal of a 3-input AND gate 22. Supplied. 3 input AND
The other two input terminals of the gate 22 are supplied with the Q output d of the monostable multiplier 21 and the Q output a of the R-S flip-flop 15, respectively. An analog switch 23 and a capacitor C ₂ are connected in series between the two external terminals of a time limit setting resistor R ₁ and a capacitor C ₁ of the monostable multi 21. The analog switch 23 is configured to be turned on when a high level signal is supplied to the control input terminal. A control input terminal of this analog switch 23 is supplied with a 4-track detection signal c. The output e of the three-input AND gate 22 is supplied to the trigger input terminal of the monostable multi 24. The output f of the monostable multi 24 is supplied to a control input terminal of a changeover switch 25. Changeover switch 25
One input terminal of is grounded. Further, the Q output of the R-S flip-flop 15 is supplied to the other input terminal of the changeover switch 25 via a resistor _R2 . The output terminal of this changeover switch 25 is provided with a signal supplied to one input terminal when a low level signal is supplied to the control input terminal, and a signal supplied to the other input terminal when a high level signal is supplied to the control input terminal. The signal applied to the terminal is derived.
The signal derived from the output terminal of the changeover switch 25 is supplied to the negative side input terminal of the operational amplifier 26. The Q output g of the monostable multi 24 is supplied to the positive input terminal of the operational amplifier 26. Further, a feedback resistor R ₄ is connected between the negative input terminal and the output terminal of the operational amplifier 26. The output of the operational amplifier 26 is supplied to the adder 10 via a polarity inversion circuit 27 as a drive signal h. Polarity inversion circuit 2
7 is configured to invert the polarity of the drive signal h in response to a FWD (forward direction)/REV (reverse direction) reproduction command.

In the above configuration, a jump command signal is output from the high-speed reproduction operation control circuit, etc., and the R-S flip-flop 15 is set to the set state, and the Q output a of the R-S flip-flop 15 is set at time _t1 as shown in FIG. 2A. When the level becomes high, a high level signal is supplied to the control input terminal of the loop switch 8. Then, the loop switch 8 is turned off, and the tracking servo loop is opened. At the same time, the count 18 is preset to, for example, "100" as the data N output from the high-speed reproduction operation control circuit. At this time, the monostable multi 24 is not inverted and the output f is at a high level as shown in F in the figure. Therefore, the Q output a of the R-S flip-flop 15, which is supplied to one input terminal, is derived from the output terminal of the changeover switch ₂₅ via the resistor R2. Also, since the Q output g of the monostable multi 24 is at a low level, the positive input terminal of the operational amplifier 26 is grounded, and the operational amplifier 26 and resistors R ₂ and R ₃ receive the Q output a as input. It functions as an inverting amplifier circuit. Therefore, the drive signal h output from the operational amplifier circuit 26 becomes lower than the ground level as shown in FIG. Start moving in the direction.

As the information detection spot light 2 moves, an on-track signal consisting of a low level signal is generated every time it skips a recording track, and the output b of the track detection circuit 16 becomes as shown in FIG. Then, when the on-track signal disappears, that is, when the output b of the track detection circuit 16 rises, the count value of the counter 18 becomes small. Furthermore, when the on-track signal is generated, that is, when the output b falls, the monostable multi 21 is triggered, and the Q output d remains at a high level for a time T ₁ corresponding to the time constants C ₁ and R ₁ as shown in D of the same figure. becomes.

Thereafter, the moving speed of the spot light 2 relative to the recording track in the radial direction is accelerated, and the time during which the output b is at a low level becomes shorter and becomes less than _T1 , and the output b and the Q output d as shown in FIG.
3 input AND over the period when both are at high level
The output e of the gate 22 becomes high level. When this output e becomes a high level, the monostable multi 24 is triggered, and the output f remains at a low level for a predetermined time _T2 from the time when the output e becomes a high level, as shown in FIG. Then, the negative input terminal of the operational amplifier 26 is grounded, and the operational amplifier 26 and the resistor
R ₃ acts as a non-inverting amplifier circuit which receives the Q output g of the monostable multi 24 as an input. The Q output g of the monostable multi 24 remains at a high level for a predetermined time T ₂ from the time when the output e becomes a high level, as shown in FIG. Therefore, the drive signal h is the output e
The spot light 2 remains at a level higher than the ground level for a predetermined period of time _T2 after reaching a high level.
The relative moving speed of is reduced to a predetermined speed V ₁
is controlled to be almost constant.

After that, spot light 2 covers the recording track by 4 more times.
When the vehicle moves to a position where it reaches the target track by jumping over the track, the count value of the counter 18 becomes 4. Then, as shown in Figure B, a 4-track detection signal c consisting of a high level signal is generated and the analog switch 23 is turned on (time _t2 ). As a result, the inversion time of the monostable multi 21 becomes a time _T3 corresponding to the time constant ( _C1 + _C2 ) _R1 , which is longer than _T1 . Therefore, _the relative moving speed of the spot light 2 is controlled to be substantially constant at the speed V2, which is lower than the speed _V1 , after time _t2 .

Then, when the spot light 2 skips over the last recording track to be skipped, the count value of the counter 18 becomes zero and the four-track detection signal c disappears (time t ₃ ). At the same time, a zero detection signal is output from the zero detection circuit 19, and the R-S flip-flop 1
5 is reset, and the Q output a becomes low level.
Then, the drive signal h becomes zero level, the tracking servo loop is closed, and the information detection spotlight 2 is positioned on the target track.

In the apparatus shown in FIG. 1, for example, when 100 tracking jump operations are performed, the waveform of the servo loop on/off state, the tracking servo error waveform, and the amount of deviation of the tracking actuator (the amount of deflection of the mirror 12). The waveforms are as shown in Figure 3 A and B.
and C, respectively. At the time when the jump operation is completed (t ₃ ), the amount of deflection of the mirror 12 is converted into the radial distance on the recording disk and is approximately 1.6×100=160 μm, assuming the track pitch is 1.6 μm. If the tracking servo loop is closed at this point, the servo will be locked in with an offset V ₀ that has a tracking error. It is believed that there are two reasons why such an offset occurs. One of them is that the frequency response characteristic of the tracking actuator is a low-pass filter characteristic as shown in FIG. The next drive signal h comes before it has returned to its original position. Therefore, the amount of deflection of the mirror 12 is accumulated and becomes approximately proportional to the number of jumping tracks. The other reason is mirror 12
When the tracking servo loop is closed with the amount of deflection as described above, the mirror 12
cannot immediately return to its original position, and the servo loop works to maintain the shifted state for a while. For this reason, the tracking error does not immediately become zero, but remains in a state with a certain offset _V0 . In addition, immediately after the 100 track jump (t ₃ )
The runout amount, which was 160 μm, gradually approaches the 0 level as shown in FIG. 3C due to the action of the slider servo, and therefore the offset during tracking error also gradually decreases.

The above-mentioned state with an offset of tracking error V ₀ means that the output of the differential amplifier 7 is V ₀ , which means that the detection spot light 2 has a tracking error from the center of the recording track 1.
This means that it is shifted by a distance corresponding to V ₀ .

Here, if the number of jump tracks is increased, the amount of mirror shake increases accordingly, and the offset amount of tracking error also increases. As this offset amount V ₀ approaches the peak level _Ve of tracking error, servo lock-in becomes unstable, and if V ₀ ≧V _e , lock-in becomes impossible. That is, if the number of jump tracks is increased, the offset increases and lock-in becomes unstable, resulting in a drawback that eventually lock-in becomes impossible.

Therefore, in the present invention, a correction signal of an amount equal to the offset amount of the tracking error corresponding to the amount of deflection of the tracking actuator is forcibly added and applied from outside the tracking servo loop, so as to substantially correct the tracking error. An object of the present invention is to provide a recorded information reproducing device that can perform stable servo lock-in by preventing offset from occurring in the king error itself.

The recorded information reproducing apparatus according to the present invention generates a signal corresponding to the amount of deviation of the tracking actuator that drives the recorded information detection point at least at the instant of closing of the tracking servo loop at the end of the jump operation. The servo error signal of the tracking servo loop is added to the servo error signal of the tracking servo loop.

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

FIG. 5 is a block diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are designated by the same reference numerals. In this example, a detection amount 28 for detecting the amount of shake of the tracking mirror 12 is added, and a correction signal corresponding to this amount of shake is added and applied to the tracking servo loop. For this purpose, an adder 29 is inserted in the output stage of the differential amplifier 7 to add the correction signals. The other configurations are the same as those shown in FIG. 1, and their explanation will be omitted.

By doing this, at the moment when the loop is closed, a correction signal proportional to the amount of mirror shake is added to the servo error signal, so this correction signal is added to the servo error signal.
By setting the level equal to the offset V ₀ in Figure B, this correction signal causes the mirror 12 to
A deflection of 160 μm will be maintained. Therefore, the tracking error signal output from the differential amplifier 7 no longer contains an offset.
The servo tracking becomes stable. This operation remains the same even when the number of jump tracks increases, so
Lock-in is never possible.

FIG. 6 is a block diagram of another embodiment of the present invention, in which a correction signal is obtained by charging and discharging a capacitor. The correction signal generator 30 is a capacitor
_C3 , a current source 32 for charging this capacitor,
A switch 33 for turning on/off charging, a discharging resistor _R4 , a switch 34 for turning on/off discharging,
Buffer 31 that outputs the discharge signal as a correction signal
The output of this buffer 31 is input to the adder 29 via the polarity inversion circuit 36. This polarity inversion circuit 36 controls the polarity of the correction signal in accordance with the FWD/REV reproduction command, and has the same function as the polarity inversion circuit shown at 27.

The charge/discharge switches 33 and 34 are controlled by the Q output of the flip-flop 15 and the output of the Q output from the inverter 35, so that they are controlled to be turned on and off in a complementary manner to each other. The other configurations are the same as those in FIG.

In such a configuration, when the jump operation is not performed, the switch 33 is off;
4 is turned on to reset the discharge of capacitor _C3 . Switch 33 during jump operation
Since the capacitor C3 is on and the switch 34 is off, the capacitor _C3 is charged with a constant current by the current source 32 during that time, and its charging voltage rises with a constant slope. The peak value E of this voltage is the pulse width τ of the Q output of the flip-flop 15 (see Fig. 3A).
This width τ is proportional to the jump track number N. Since the amount of mirror shake is Ntp where tp is the track pitch, E∝τ∝N∝Ntp, and therefore E is proportional to the amount of mirror shake.

That is, the correction signal obtained by discharging this charging voltage E through a suitable resistor _R4 is added to the tracking error and the loop at the adder 29, so that the same effect as shown in FIG. 5 can be obtained. .
Note that the discharge time constant of the capacitor _C3 is determined according to the response characteristics of the slider servo loop. Also,
Not only the jump in the forward direction but also the jump in the reverse direction is made possible by the action of the polarity inversion circuit 36.

FIG. 7 is a block diagram of another embodiment of the present invention, showing another example of the correction signal generator 30.
That is, since the preset value N of the presettable counter 18 indicates the jump track number, this digital value is converted into D/A (digital/digital/
The signal is converted into an analog value by an analog converter 37, and this analog value is applied via a switch 38 to a time constant circuit including a capacitor C ₃ and a resistor R ₄ . The discharge output of this time constant circuit is supplied to the servo loop as a correction signal via a buffer 39.

The switch 38 is controlled by the Q output of the flip-flop 15, and the switch 38 is turned on at the moment the jump operation ends, and an analog voltage proportional to the jump track number, that is, the amount of mirror deflection, is discharged by time constants C ₃ and R ₄ . It is.
It is clear that by doing so, the same effects as the examples shown in FIGS. 5 and 6 can be obtained.

As mentioned above, according to the present invention, a correction signal is generated according to the amount of deflection of the tracking actuator, and this correction signal is applied to the loop at the moment the tracking servo loop is closed, thereby reducing tracking errors. As a result, offset substantially does not occur, and stable servo lock-in is possible. In particular, even with a tracking actuator having a small low-frequency gain, it is possible to easily jump a large number of tracks.

Although the optical information reading device has been described above, it can also be applied to other types, such as electrostatic type, and is also applicable not only to the device shown in the example in Fig. 1 but also to devices having various jump functions. Applicable.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a recorded information reproducing device proposed by the applicant, Figures 2 and 3 are operational waveform diagrams of the device shown in Figure 1, and Figure 4 is the frequency response characteristic of the tracking actuator. 5 to 7 are block diagrams of embodiments of the present invention. Explanation of the main parts, 1...Record track,
2... Recorded information detection spot, 8... Servo loop switch, 12... Tracking mirror, 13
... Drive coil, 28 ... Mirror shake amount detector,
29... Adder, 30... Correction signal generator.

Claims (1)

[Scope of utility model registration request] A recorded information reproducing apparatus is configured to interrupt a tracking servo loop in response to a jump command and jump a recorded information detection point from one recording track to another target recording track, the apparatus comprising: Also, at the closing instant of the tracking servo loop, a signal corresponding to the amount of deviation of a tracking actuator for driving the recorded information detection point is generated and added to a servo error signal of the tracking servo loop. A recorded information reproducing device characterized by comprising means.