JPH07114739A - Optical disk device - Google Patents

Abstract

PURPOSE:To prevent the access time from becoming longer in a coarse seek servo for feeding a carriage into the vicinity of the radial position of a target track address even when an offset exists in an electric circuit in a servo loop. CONSTITUTION:In a velocity servo, an ending position where t velocity of a velocity profile VP3A utilized for a velocity reference signal becomes zero is set in a position TBc exceeding a target track position TB. Consequently, even when the offset exists in the electric circuit in the servo loop, the servo has a minute velocity DELTAv in the advancing direction until the target track position, so that a situation of returning the carriage does not take place. Because of no return, a counting operation of a clock pulse CK is also smoothly carried on, and upon coincidence of the target track position TB and a set clock pulse number (n), the device can smoothly be shifted to a positional servo operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device suitable for application to, for example, an optical disk drive.

[0002]

2. Description of the Related Art Conventionally, in an optical disk drive, a carriage having an optical pickup is moved in a radial direction of an optical disk rotated by a spindle motor, and the optical pickup drives recording and / or recording on an arbitrary track on the optical disk. ) You can play it.

When the time for moving the carriage having the optical pickup from a certain track position on the optical disk to the target track position is defined as the access time, this access time is preferably shorter.

When a carriage having an optical pickup is moved to a target track position, first, a coarse seek servo using a linear motor or the like is used.
The carriage is moved at high speed to the vicinity of the target track roughly, and then a fine seek servo, that is, a tracking servo by an optical pickup is applied, the address recorded on the track is read, and the actual target track position, More specifically, the optical pickup is accurately moved to a target address position on the track, for example, a sector position.

FIG. 4 is a diagram for explaining the operation of the rough seek servo. In the example of FIG. 4, the carriage 4 accommodating the optical pickup 3 moves from the current track position (hereinafter, also simply referred to as current track position) TA to a target track position (hereinafter, simply referred to as target track position). ) In the radial direction R of the optical disk 2 by a linear motor (not shown) along a linear scale (not shown) on TB
The servo operation sent to will be described.

In this case, the trapezoidal speed profile VP shown in FIG. 4 is given to the linear motor through a reference input terminal of a comparison amplifier (not shown) which constitutes a servo loop. The detection speed signal of the carriage 4 sent in the radial direction R is supplied to the comparison input terminal of the comparison amplifier (not shown).

This trapezoidal velocity profile VP is composed of three parts, a constant positive acceleration rising profile VP1, a constant velocity profile VP2 and a constant negative acceleration falling profile VP3. When the moving distance is short, as shown by the dotted line in the figure, a triangular velocity profile VP is provided which is composed of two parts, a rising profile VP1 of constant positive acceleration and a falling profile VP3 of constant negative acceleration. .

The trapezoidal (triangular) vertices of these velocity profiles VP serve as position detectors integrally attached to the carriage 4 etc. when the current track position TA and the target track position TB are given. It is set in advance in a counter (not shown) as an integral multiple of the number of clock pulses from the encoder.

In the example of FIG. 4, for example, n is set in the counter as the set clock pulse number from the current track position TA to the target track position TB. That is, the carriage 4 starts to move in the radial direction R, and the speed servo can be switched to the position servo when n clock pulses have been counted.

[0010]

As can be seen from FIG. 4, at the zero cross point of the falling profile VP3 of the speed profile VP according to the above-mentioned conventional technique, the moving speed v of the carriage 4 becomes zero at the target track position TB. Was given.

That is, as shown in detail in FIGS. 4 and 3A, from the current track position TA to the target track position TB.
Up to this point, the position servo is designed to start when the counter counts n clock pulses CK.

By the way, as described above, the velocity profile V such that the velocity v becomes zero at the target track position TB.
When P is given, as shown in the actual falling profile VP3a of the alternate long and short dash line in FIG. 3A, when there is an offset in the electric circuit such as the comparison amplifier in the servo loop, the position before the target track position TB is reached. Position TB
There was a case where the speed v became zero at a.

However, when the feed speed of the carriage 4 in the radial direction R becomes zero at a position TBa before the target track position TB, that is, when the carriage 4 is stationary, the carriage 4 moves in the reverse direction (FIG. 4). In the example, there is a case where the situation of returning inward in the radial direction R) occurs.

At the time of returning, since the counter has counted up to the n-1th counter and has not counted the nth counter yet, the counter tries to count up to the nth counter while reversing. As a result, as shown in FIG. 3A, the nth clock pulse C of the clock pulse CK shown by the alternate long and short dash line.
The velocity servo ends when K is counted, and the position servo is switched to the stationary state.

In this case, the carriage 4 is stopped by the position servo at a position x relatively distant from the target track position TB, and the carriage 4 is moved to the target track position TB by a track jump or the like by the tracking servo.
There is a problem that it takes an extra time for the optical pickup 3 constituting the above to arrive and the access time becomes long.

The present invention has been made in consideration of such a problem, and makes it possible to prevent the access time from becoming long even when an electric circuit in the servo loop has an offset. An object is to provide an optical disk device.

[0017]

According to the present invention, a carriage 4 having an optical pickup 3 and movable in a radial direction R of an optical disk 2 is moved by using a speed servo and stopped by using a position servo. In the optical disk device for moving from the arbitrary track position TA of the optical disk 2 to the target track position TB, the speed profile VP3 used as the speed reference signal Sv in the above speed servo.
The end position at which the speed of 0 becomes a zero value is set to a position TBc that exceeds the target track position TB.

[0018]

According to the present invention, in the speed servo for moving the carriage 4 having the optical pickup 3 in the radial direction R, the end position where the speed of the speed profile VP3A used as the speed reference signal Sv becomes zero value is set as a target. The position TBc that exceeds the track position TB is set. Therefore, even if there is an offset in the electric circuit in the servo loop, the carriage 4 having the optical pickup 3 moves back up to the target track position TB and has a minute speed Δv. The situation does not occur.

More specifically, since there is no reversion, the counting operation of the clock pulse CK is also smoothly continued, and when the target track position TB and the set clock pulse number n match, the position servo operation is smoothly performed. be able to. As a result, the situation that the access time becomes long does not occur.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are given to those corresponding to those shown in FIGS. 3A and 4.

FIG. 1 shows the structure of the optical disk device according to this embodiment as a whole. In this optical disk device, an optical pickup 3 accesses an optical disk 2 rotated by a spindle motor 1 so that an information signal recording or reproducing operation is performed.

Here, the optical disk 2 may be any of a write-once optical disk, a rewritable optical disk, a CD-ROM, or a read-only optical disk. In the example of FIG. 1, a CD-ROM is mounted.

The optical pickup 3 is integrally attached to the carriage 4 and moves under the drive of the linear motor 5 along the linear scale 6 in the radial direction R (radius inner direction R1 and radius outer direction R2) of the optical disk 2. Is able to.

Based on the information signal read from the optical disc 2 by the optical pickup 3, for example, a track address at a position in the radial direction R at which the optical pickup 3 is currently located (hereinafter, referred to as a current track address, if necessary). TA is grasped in the control circuit 10.

On the other hand, the host computer 11 supplies the control circuit 10 with the data of the target track address (hereinafter referred to as a target track address, if desired) TB to be accessed on the optical disk 2.

Therefore, hereinafter, the current track address TA
From the radial position of the target track address TB to the radial position of the target track address TB by the seek operation to move the optical pickup 3 in the outer radial direction R
The positioning operation for moving to No. 2 will be described.

In this case, first, the control circuit 10 outputs a speed reference signal Sv having a trapezoidal or triangular profile, which is a positive (non-inverting) input terminal of a comparison amplifier 13 which is a differential amplifier, an adder circuit 14 and When the optical pickup 3 is supplied to the linear motor 5 through the drive amplifier 15, the optical pickup 3 starts to move through the carriage 4, for example, in the radial outer direction R2.

While the optical pickup 3 is moving in the radial outward direction R2, the A phase of substantially sinusoidal shape having a 90 ° (π / 2) phase difference from the encoder 4A as a position detector constituting the carriage 4 is provided. The signal A and the B-phase signal B are output. In this case, as is well known, the encoder 4A is arranged to read two rows of small hole groups formed above and below the linear scale 6 in the radial direction R, for example, with a phase difference of 90 ° for every 200 μm. Each of the two rows of small hole groups is composed of two photo interrupters arranged in the carriage 4. The encoder 4
As A, not only such an optical type, but also a magnetic type or an electrostatic type can be used.

From the A-phase signal A and the B-phase signal B, the inverted A-phase signal bar A and the inverted B-phase signal bar B which are inverted by the inverting amplifiers 17 and 18 are created.

FIG. 2A shows the A-phase signal A, the B-phase signal B, the inverted A-phase signal bar A and the inverted B-phase signal bar B (hereinafter, these signals are collectively referred to as necessary.
Signal A, bar A, B, bar B. ) Shows the waveform. As can be seen from the figure, A-phase signal A and B-phase signal B
Have a phase difference of 90 °, and the A-phase signal A and the inverted A-phase signal bar A have a phase difference of 180 ° with the B-phase signal B and the inverted B-phase signal bar B, respectively.

The signals A, A, B and B are supplied to the multiplexer 25, and one appropriate signal is selected according to the values of the control signals C1 and C2 supplied to the control terminal of the multiplexer 25. , The position signal P is created.

Further, the signals A, A, B, and B are differentiated by a differentiating circuit 21 composed of, for example, a capacitor and a resistor, and a differential A phase signal A'and a differential inverted A phase signal bar A '. , Differential B-phase signal B ′ and differential inversion B-phase signal bar B ′ (hereinafter, these signals are collectively referred to as differential signal A ′, bar A ′, B ′, and bar B ′, if necessary. ).

FIG. 2B shows a differential signal A ', bars A', B ',
The waveform of bar B'is shown. These differential signals A ′,
Bars A ', B', and B'are speed signals, and the higher the speed, the higher the level. These differential signals A
', Bar A', B ', and bar B'are supplied to the multiplexer 26, and an appropriate one signal is selected and detected according to the values of the control signals C1 and C2 supplied to the control terminal of the multiplexer 26. The speed signal V is supplied to the negative (inverting) input terminal of the comparison amplifier 13.

Further, the A-phase signal A and the B-phase signal B are supplied to the comparison circuit 22 which constitutes the comparison circuit 24. The comparison circuit 22 makes a determination "A>B", and outputs a control signal C1 which is a binary signal of level "1" when this determination result is satisfied and level "0" when this determination result is not satisfied (see FIG. 2C). ). Furthermore, the A-phase signal A and the inverted B-phase signal bar B are supplied to the comparison circuit 23 that constitutes the comparison circuit 24. The comparison circuit 23 makes a determination “A> bar B”, and outputs a control signal C2 which is a binary signal of level “1” when this determination result is satisfied, and level “0” when this determination result is not satisfied (FIG. 2C). reference).

As shown in FIGS. 2C and 2D, when the control signals C1 and C2 are "1,0", the multiplexers 25 and 26 respectively output A as the position signal P.
The phase signal A is output, and the differential A phase signal A is output as the speed signal V.
'Is output. Similarly, the signal B (B ') when "1,1", the signal bar A (bar A') when "0,1", and the signal bar B (bar B ') when "0,0".
Is output.

FIG. 2E shows the waveform of the position signal P thus created, and FIG. 2F shows the waveform of the velocity signal V.

As shown in FIG. 1, the control signal C1 and the control signal C2 are supplied to the input side of one exclusive OR circuit 52 constituting the clock generation circuit 51.

In this case, the exclusive OR circuit 52
2H appears on the output side of the delay circuit 53.
2D, the output waveform is represented as shown in FIG. 2I. Therefore, the waveform of the clock signal CK obtained at the output side of the other exclusive OR circuit 54 is as shown in FIG. 2G.

The position signal P is supplied to the linear motor 5 through the amplifier 36, the position servo on / off switch 37, the adder circuit 14, and the drive amplifier 15.

The on / off switch 37 is used for the control circuit 10.
It is adapted to be switched based on the control signal C4 from.

Then, actually, the current track address T
When the carriage 4 having the optical pickup 3 is moved in the outward radial direction R2 by the seek operation from the radial position of A to the radial position of the target track address TB, the moving distance based on the target track address TB and the current track address TA is set. The count number of the corresponding clock signal CK, that is, the count value n is calculated in the control circuit 10, and the calculated count value n is preset in a down counter (not shown) in the control circuit 10. Since the track pitch of the optical disc 2 and the like are stored in the ROM in the control circuit 10 in advance, this calculation is easy.

When performing a seek operation, the control circuit 1
According to the difference signal (output signal of the comparison amplifier 13) between the speed reference signal Sv and the speed signal V supplied from the control circuit 10 with the ON / OFF switch 37 in the OFF state (state shown) by the control signal C4 of 0. Apply speed servo. That is, when the output signal of the comparison amplifier 13 is substantially supplied to the linear motor 5, the carriage 4, that is, the optical pickup 3 is moved in the direction of the radial position having the target track address TB.

Here, the speed reference signal Sv has a trapezoidal profile, but the falling profile VP3 of the speed profile VP according to the above-mentioned conventional technique has a zero cross point at the target track position TB as shown in FIG. 3A. While the speed v is given so as to have a zero value, in this embodiment, as shown in FIG. 3B, the zero cross point of the speed profile VP3A at the falling edge of the speed profile VP is the n-th clock pulse CK. The position is set to a position TBc that is beyond the target track address TB (a far position).

Therefore, even if there is an offset in the electric circuit in the servo loop, for example, the comparison amplifier 13, etc., the falling speed profile VP3A is shown in FIG.
The falling velocity profile VP shown by the one-dot chain line in B
If it is 3Aa (the position of the zero-cross point is the position T
(When it is Bb), the clock pulse C
At the target track address TB where n K is counted,
Since the carriage has the minute speed Δv in the traveling direction R2, the carriage 4 having the optical pickup 3 does not return.

More specifically, since there is no reversion, the counting operation of the clock pulse CK continues smoothly, and when the target track address TB and the set clock pulse number n match, the position servo operation smoothly shifts. be able to. As a result, the situation that the access time becomes long does not occur.

Of the speed profile VP, the zero cross point of the falling speed profile VP3 is located at the position TBc.
When the clock signal CK arrives from the clock generation circuit 51 in the state set to, the control circuit 10 subtracts the count value preset in the down counter by 1 at the rising edge of the clock signal CK. , When the value reaches the target track address TB in FIG. 3B, the on / off switch 37 is switched to the position signal P side by the control signal C4 to start the position servo.

Then, as shown in FIG. 2G, of the clock signal CK, for example, when the on / off switch 37 is switched to the position signal P side at the rising edge at time t1, the position signal P shown in FIG. Stable point QP
At 1, the position servo for the carriage 4 is started, and this position servo is continued.

While the position servo is continuing, the carriage 4 is held at the radial position. When the carriage 4 is held, fine seek servo, that is, tracking servo by the optical pickup 3 having a biaxial actuator and the control circuit 10 is performed, and the track address recorded on the track is the optical pickup. 3 is read by the control circuit 1 as a new current track address TA.
Stored in 0.

At the time of fine seek servo, the control circuit 10 compares the present track address TA with the target track address TB supplied in advance from the host computer 11, and if they are different, a track jump signal for each track. By supplying TJ to the optical pickup 3, the optical pickup 3 is made to seek to the target track address TB position.

As described above, according to the example of FIG. 1, in the speed servo for moving the carriage 4 having the optical pickup 3 in the radial direction R, the speed of the speed profile VP used as the speed reference signal Sv ends at zero value. The position is set to a position TBc that exceeds the target track address TB. Therefore, even if the electric circuit in the servo loop (for example, the comparison amplifier 13 and the addition circuit 1
4, the amplifier 15 etc.) also has a slight velocity Δv (see FIG. 3B) in the traveling direction up to the target track address TB, and the carriage 4 having the optical pickup 3 goes back. The effect that the situation does not occur is achieved.

More specifically, since there is no reversion, the counting operation of the clock pulse CK continues smoothly, and when the target track address TB and the set clock pulse number n match, the position servo operation smoothly shifts. be able to. As a result, the situation where the access time becomes long does not occur.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0053]

As described above, according to the present invention, in the speed servo for moving the carriage having the optical pickup in the radial direction, the end position where the speed of the speed profile used as the speed reference signal becomes zero value. Is set to a position beyond the target track position. For this reason, even if there is an offset in the electric circuit in the servo loop, the carriage will have a slight velocity in the traveling direction up to the target track position, and the carriage with the optical pickup will reverse. The effect of not doing is achieved.

More specifically, since there is no reversion, the clock pulse counting operation can be smoothly continued, and when the target track position and the set clock pulse number match, the position servo operation can be smoothly performed. .

As a result, the situation where the access time becomes long does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of an optical disk device according to the present invention.

FIG. 2 is a diagram showing waveforms and the like used for explaining the operation of the example in FIG. 1, where A is an A phase signal, B is each speed signal, C is a control signal, and D is a position signal and speed signal selection operation E is a position signal F is a velocity signal G is a clock signal H is a signal generated from a control signal I is a signal generated from a signal obtained by delaying the control signal.

FIG. 3A is a diagram used for explaining the operation of the conventional technique. FIG. 3B is a diagram used for explaining the operation of the embodiment.

FIG. 4 is a diagram used for explaining an operation of a rough seek servo.

[Explanation of symbols]

 1 Spindle Motor 2 Optical Disc 3 Optical Pickup 4 Carriage 4A Encoder 5 Linear Motor 6 Linear Scale 51 Clock Generation Circuit CK Clock Signal P Position Signal V Speed Signal VP Speed Profile TA Current Track Address TB Target Track Address

Claims (2)

[Claims] 1. A carriage, which has an optical pickup and is movable in a radial direction of an optical disk, is moved by using a speed servo and made stationary by using a position servo, and from an arbitrary track position of the optical disk to a target track position. In the optical disc device to be moved, the end position where the velocity of the velocity profile used as the velocity reference signal in the velocity servo becomes zero value is set to a position exceeding the target track position. apparatus. 2. The optical disk device according to claim 1, wherein the speed profile is a trapezoidal or triangular speed profile.