JP2684732B2 - Optical disk seek device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk seek device useful when an optical head is moved to access a desired track of an optical disk.

[Summary of the Invention]

A seek device for an optical disk according to the present invention compares a moving signal for moving a coarse actuator to a target track at high speed with a speed signal indicating a moving speed of the rough actuator, and supplies a drive signal for the rough actuator to the optical disk. In the seek device, when the address data can be read out during the seek, the movement signal to the target track formed by the address data is compared with the current speed signal calculated by the address data. Since the coarse actuator is driven by the drive signal of, the control speed can be controlled so that the moving speed of the optical head becomes completely zero on the target track, and the access time can be shortened. .

[Conventional technology]

An optical disk device capable of irradiating an optical disk with a laser beam to record information and reading the recorded information is generally equipped with an optical head that moves in the radial direction of the optical disk. The coarse actuator for moving the is driven by, for example, a linear motor or the like.

FIG. 5 shows an outline of such an optical head. The optical head 1 crosses a recording track 3 formed on a magneto-optical disk 2 and extends in a radial direction of the magneto-optical disk. A coarse actuator (linear motor) 5 arranged so as to slide with respect to the guide rods 4A and 4B, and mounted on the coarse actuator 5 so as to swing about the rotation shaft 7 in the direction of the arrow by a slight angle. It is formed of a fine actuator (biaxial mechanism) 6 arranged.

Reference numeral 8 denotes an objective lens for irradiating the magneto-optical disk 2 with a laser beam emitted from the fine actuator 6, and the laser beam tracks the recording track 3 of the magneto-optical disk 2 so that the magneto-optical disk 2 rotates. The information can be read or written.

Further, in the seek operation of accessing the optical head 1 to a desired track of the magneto-optical disk 2, in general, by supplying a predetermined drive signal to the coarse actuator 5 of the optical head 1, the entire optical head is moved to the radius of the magneto-optical disk 2. It is designed to move in the direction and seek the target track.

By the way, in such a magneto-optical disk device, in order to shorten the time required to access the target track as a whole, the coarse actuator 5 is moved at a high speed, and the moving speed of the target recording track is almost the same. It is preferable to control so as to be “0” so that tracking control can be performed immediately.

FIG. 6 is a block diagram of a high-speed seek control circuit (Japanese Patent Application No. 62-206971) proposed by the applicant earlier, and 11 is a control circuit for performing a seek operation. Under the control of the control circuit 11, the circuit 12 counts up from the initial value “0” to half the number of tracks to be sought, and counts down to the next target recording track. There is.

That is, the counter circuit 12 sequentially counts up the traverse count signal S _TV indicating the number of tracks traversed during seek from the rising timing of the start signal S _ST and the up / down signal CNT _UD input from the control circuit 11, Following this, the up / down signal CNT _UD is
At the timing of counting by half the number of tracks to be sought at, a countdown operation is performed, and the count value CT is sent to the subsequent D / A converter 13.

As a result, from the D / A converter 13, as shown in FIG.
_While moving up to the recording track t ₂₀ which is half of _21, the driving voltage V _{30 which} becomes higher sequentially as the coarse actuator 18 moves.
Is supplied to the coarse actuator 18 via the switch circuit 15, the adder circuit 16, and the drive circuit 17.

Next, the number of tracks that the coarse actuator 18 should seek.
Target recording track from t _{20 which is} half of t ₂₁
While moving up to t _{21, the} up / down signal CNT _UD (Fig. 7 (b)) given from the control circuit 11 falls, and the counter circuit 12 performs a countdown operation to sequentially decrease as the coarse actuator 18 moves. The driving voltage V ₃₀ is supplied to the coarse actuator 18, and the traverse count signal S _TV is used as a whole to form a position servo loop based on the movement amount of the coarse actuator 18.

The moving speed S _V30 of the coarse actuator 18 is shown in FIG. 7 (c).
As shown in, the speed signal S obtained from the speed sensor circuit 19
Based on the _V30, while the coarse actuator 18 is moved to a half of the recording track t ₂₀ the track number t ₂₁ should seek is controlled to rise at a faster acceleration in the velocity servo loop.

On the other hand, while the rough actuator 18 moves from the recording track t _{20 which is} half of the number t ₂₁ of tracks to be searched to the target recording track t _21, sufficient acceleration is obtained, so that negative feedback is performed in the speed servo loop. By forming the circuit, the number of remaining tracks up to the target recording track t ₂₁ and the moving speed S _V30 of the rough actuator 18 are gradually converged to “0”, and the rough actuator 18 is further moved to the target recording track t _21. Movement speed S when reaching ₂₁
It is designed so that the _V30 can be reliably controlled to "0".

According to the above configuration, while the coarse actuator 18 moves from the start of the seek operation to the recording track t ₂₀ which is half the number t ₂₁ of tracks to be seeked, the coarse actuator 1
Increases sequentially with 8 moves, followed by coarse actuator 1
8 while the move from one half of the recording track t ₂₀ of the number of tracks to be seeking to a target recording track t _21, the driving voltage V to be sequentially reduced in accordance with the movement of the coarse actuator 18
By controlling the drive of the coarse actuator 18 by using ₃₀ , the moving speed S _V30 of the coarse actuator 18 is surely controlled to “0” when the coarse actuator 18 moves to the target recording track t ₂₁ to be _sought. can do.

[Problems to be solved by the invention]

By the way, the seek device as described above uses, as the velocity sensor signal, the electromotive force when traversing in the magnetic field, so that the coarse actuator 18 starts moving,
And when the coarse actuator 18 slows down near the target track, it becomes very difficult to obtain an accurate velocity signal (SV).

That is, when the moving speed of the coarse actuator is low, the signal level induced in the detection coil that constitutes the speed sensor decreases and S /
A speed signal with N reduced is output.

Then, in particular, when the coarse actuator 18 approaches the target track, accurate speed servo cannot be applied, and as a result, the moving speed of the coarse actuator 18 does not become zero when the target actuator actually reaches the target track. .

If the target track cannot be accessed accurately, a seek operation for jumping the dense actuator is required again at this point, and there is a problem that it takes a long time to perform tracking on the target track.

Further, it is conceivable to use an optical speed sensor as the speed sensor, but in this case, a light source, an optical system lens, an optical disk, and the like are required, which causes a problem of increasing the cost of the optical head.

Further, even when a count error in the number of traverse tracks counted by the counter circuit occurs, the seek operation cannot accurately capture the target track.

[Means for solving the problem]

The present invention has been made in order to solve the various problems described above, and a drive signal is formed by comparing the output of a target value setting circuit for jumping a coarse actuator to a target track with the speed signal of the coarse actuator. In the optical disk seek device, when the address data of the optical disk can be read when the moving speed of the coarse actuator is low,
A means for setting a target value using this address data and a means for detecting the moving speed of the coarse actuator by detecting the timing at which the address data is obtained are used, and the drive signals output from these means are used. The seek operation of the coarse actuator is performed.

[Action]

An optical disk in which the optical disk is divided in the circumferential direction and the address information is recorded in the divided sectors can easily sample only the address data even during seeking, so when seek operation is performed at a low speed, The address data can be read relatively easily.

Therefore, even in the case of a seek device that performs a high-speed seek operation, the address data can be detected especially near the track of the target value, and the seek distance and speed to the target track are calculated based on this address data and driven. When the signal is formed, a highly accurate seek operation can be performed.

〔Example〕

FIG. 1 is a schematic diagram of the seek apparatus of the present invention.

In this figure, control circuit 11, counter circuit 12, D / A converter 13
As described above, the coarse actuator 18
To generate a target value signal for moving the track on a desired track, and the inverting circuit 14 supplies an inverting output when the switch circuit 15 switches depending on the seek direction.

During the seek operation, the b contact of SW ₁ is connected, and the output of the adder circuit 16 supplies the drive signal on which the speed servo is applied to the coarse actuator 18 via the drive circuit 17. Then, as described above, when the target value signal is accurate and the speed sensor circuit 19 outputs the speed information with high accuracy, the coarse actuator 18 can be stopped at the target track.

The seek apparatus of the present invention is provided with a seek control unit 20 and a sub-target setting unit 30 in addition to the main seek apparatus described above.

As will be described later, the seek controller 20 receives the address data of the optical disk and the control signal, and forms address data A _P at the start of seek and address data A _{0 of the} target track.

Also, the playback read mode of address data during a seek operation, when the address data is read to the time signals S ₁ to select the contact c of the switch SW ₁ is output.

The sub-target setting section 30 includes at least a track number detecting section 30A for detecting the number of tracks up to the target track, and a speed detecting section 30B for detecting the moving speed of the coarse actuator 18 based on the read address data.

By locking the displacement of the fine actuator during the seek of the rough actuator 18 by some method, the output of the speed detecting unit 30B detects the relative speed of the laser spot and the optical disc.

As described above, the seek apparatus for the optical disc of the present invention is provided with the sub-target setting section 30 that operates based on the address data in the conventional seek apparatus, and the output of the sub-target setting section 30 is the address. The signal S ₁ of the seek controller 20 indicating that the reading is possible is supplied to the coarse actuator 18.

That is, the speed curve of FIG. 7 is shown in FIG.
As shown in FIG. 5, the drive signal S _V2 of the sub-target setting unit 30 controls the portion indicated by the thick line which is lower than the low speed v ₀ in the seek start period t ₁ and the seek end period t ₂ .

Since the drive signal S _V2 output in the seek end period t ₂ is a speed servo signal formed based on the address data of the optical disc D, if the target track address is input to the seek controller 20, The target track can be controlled so that the moving speed of the coarse actuator becomes zero.

Further, when the seek distance of the optical disk is short, that is, when the number of traverse tracks is extremely small, the coarse actuator 18 is not sufficiently accelerated and its moving speed exceeds v ₀ as shown in FIG. 2 (b). There are times when it is not.

In this case, from the beginning, the drive signal S _V2 of the sub-target setting unit 30
Only by moving the coarse actuator 18, it becomes possible to perform a seek operation similar to the conventional multi-track jump by the coarse actuator 18.

FIG. 3 is a block diagram showing a specific example of the sub-target setting section 30, 31 is an address decoder for converting a reproduced address RF signal into address data, 32A and 32B are subtractors, and 33 is address data. When detected, it is a time detector that can output the detection interval as a function of time.

This time detection unit can be configured by a counter circuit that is reset by a flag of address data.

Reference numerals 34A and 34B denote address data latch circuits.
The address data held in the latch circuit 34A of
Next, the new address data is read and simultaneously transferred to the second latch circuit 34B. Then, the new address data is latched by the first latch circuit 34A.

Reference numeral 35 denotes a digital subtraction circuit that subtracts the address data latched in the first and second latch circuits 34A and 34B.

36 is the output of the digital subtraction circuit 36 and the time detector
An arithmetic circuit for calculating the moving speed of the coarse actuator 18 based on the output of 33.

In this arithmetic circuit, the time when the first address data A _N is output is t _n , and the time when the next read address data A _{N + x} is read is t _{n + x} | A _{N + x} −A _N | / | t _{n + 2} −
The moving speed v of the coarse actuator is calculated by calculating t _n |, and the calculated output is supplied to the subtractor 38 via the coefficient unit 37.

This sub-target setting unit 30 is the address data at the start of seek.
At the end of seek with A _P , that is, the target address data A ₀ is supplied as the other input of the subtracters 32A and 32B.

Therefore, the subtracter 32A outputs a signal M _A that increases with the seek operation, as shown in FIG.
32B outputs a signal M _B that decreases as the seek operation elapses.

These signals M _A and M _B are selected by the switch SW ₂ .

The switch SW ₂ is adapted to be switched in the main target value setting section 10 by a signal (C _UC ) for switching the counter circuit 12 from addition to subtraction.

Therefore, at the start of the seek, the signal M _A is input to the subtractor 38 to accelerate the coarse actuator 18, and at the same time, in the latter half of the seek operation, the signal M _B is selected and input to the subtractor 38 and the deceleration signal of the coarse actuator 18 is input. To form.

Since the moving speed of the coarse actuator 18 is fed back to the subtractor 38 from the arithmetic circuit 36, the moving speed of the drive signal from the sub-target setting section 30 also tends to be as shown in FIG. 7 (c).

The gain is changed after the D / A converter 39 to eliminate the level difference between the drive signals S _V1 and S _V2 when the switch SW ₁ is switched from the b contact to the c contact or from the c contact to the b contact. It is preferable to insert an amplifier. Also, an appropriate feedback amount is set by the coefficient unit 37 to control the settling speed.

The a contact of the switch SW ₁ supplies the direct current component of the tracking error signal to the coarse actuator 18 during normal recording / reproducing so that the optical head can track the track.

〔The invention's effect〕

As described above, in the seek apparatus for the optical disc of the present invention, when the seek operation is performed by the output of the target set value, the seek apparatus that detects the speed signal of the coarse actuator and adds the speed servo is When the moving speed of the actuator decreases and the address data is read, the seek operation of the coarse actuator is controlled based on the target value based on this address data and the speed information calculated from the address data. , The coarse actuator can be moved accurately when there is an error in the initial target value setting signal or before the seek ends when the sensitivity of the speed sensor decreases, and speed control with a small steady deviation at the end of the seek The tracking servo can be applied immediately at this point. There is an effect that.

Further, since it is easy to restart the tracking servo, there is an effect that the seek time is shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram of a seek apparatus of the present invention, FIGS. 2 (a) and 2 (b) are explanatory diagrams of a seek speed, FIG. 3 is a block diagram showing a specific example of a sub-target setting section, and FIG. a),
(B) is a graph of target value and velocity signal, FIG. 5 is an explanatory view of seek operation of the optical head, FIG. 6 is a block diagram showing a conventional optical disk seek device, and FIGS. 7 (a) and 7 (b). ，
(C) is an explanatory diagram of a drive voltage to a target value and a moving speed. In the figure, 10 is a main target setting unit, 20 is a seek control unit, and 30 is a sub target setting unit.

Claims (1)

(57) [Claims] 1. A speed sensor is provided on a coarse actuator for moving an optical head in a radial direction of an optical disk, and a speed signal obtained from the speed sensor is compared with a signal for moving the coarse actuator to a desired track. In an optical disk seek device that drives the coarse actuator by a differential output signal, when the address data of the optical disk is read during seek, the address data and the seek start point address data and / or the seek end point address data are read. Comparing the movement signal to the target track formed by comparing the speed signal of the coarse actuator calculated by the read address data at the present time, and the difference output signal as the drive signal of the coarse actuator. Characterized by being configured to be supplied That the optical disk of seek apparatus.