JPH035975A - Seek circuit for optical disk - Google Patents

Abstract

PURPOSE:To easily form a seek circuit to be an integrated circuit by time- sequentially operating a D/A converter, which converts data showing the number of tracks to a target track to an analog signal, during seek. CONSTITUTION:A D/A converter 30 is provided to obtain the value of an analog signal x<0.5> from the data counting a distance to the target track with a purpose to calculate a distance x to the target track to be a target value and a function x<0.5> to apply speed servo so that a speed can be smoothly 0 in this distance x. Then, a circuit means is provided to feed back the value of the analog signal x<0.5> to this D/A converter 30 as a reference voltage at prescribed timing. The analog signal x<0.5> and an analog signal x are time-sequentially obtained from the D/A converter 30 and a differentiating signal is formed at timing to output the analog signal x. Then, speed information x' are formed to show the speed of an actuator. Thus, the speed servo circuit of an optical head is composed of the simple integrated circuit.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a seek circuit for an optical disk, and in particular, the seek circuit for an optical disk of the present invention is an integrated circuit that controls the seek speed. In an optical disk seek circuit, the speed of the optical head during jumping is controlled by the speed V (large) when moving the track and the function F of the distance to the seek target track, thereby shortening the access time to the target track. , the function 1'7 and the speed V (large) are obtained by D-A converting data corresponding to the number of tracks being traversed, and this algorithm can be applied to a small-scale IC circuit. It is designed so that it can be configured by

[Prior Art] An optical disk device that can irradiate an optical disk with a laser beam to record information and read out the recorded information is generally equipped with an optical head that moves in the radial direction of the optical disk. A coarse actuator for moving the entire optical head is driven by, for example, a linear motor.

FIG. 4 shows an outline of such an optical head. The optical head 1 has a pair of tracks extending in the radial direction of the magneto-optical disk, which traverses a recording track 3 formed on the magneto-optical disk 2. A coarse actuator (linear motor) 5 is arranged to slide relative to the guide rods 4A and 4B, and a coarse actuator (linear motor) 5 is mounted on the coarse actuator 5 and is configured to swing by a minute angle in the direction of the arrow about the rotation axis 7. It is formed from a fine actuator (two-axis mechanism) 6 arranged.

Reference numeral 8 denotes an objective lens that irradiates the magneto-optical disk 2 with a laser beam emitted from the microactuator 6, and the laser beam tracks the recording track 3 of the magneto-optical disk 2, thereby causing the laser beam to emit light from the rotating magneto-optical disk 2. It is possible to read or write information.

Also, the seek operation for accessing the optical head 1 to a desired track on the magneto-optical disk 2 is performed by moving the optical head 1 to -M.
By supplying a predetermined drive signal to the coarse actuator 5, the entire optical head is moved in the radial direction of the magneto-optical disk 2 to seek a target track.

By the way, in such a magneto-optical disk device,
In order to reduce the overall time required to access the target track, the coarse actuator 5 is moved at high speed, and the movement speed is approximately
It is preferable to perform control so that the value becomes 0'' so that tracking control can be performed immediately.

FIG. 5 shows a block diagram of a high-speed seek control circuit (Japanese Patent Application No. 62-206971) proposed earlier by the present applicant, in which 11 is a control circuit for performing a seek operation;
The counter circuit 12 is controlled by the control circuit 11 to an initial value "
A count-up operation is performed from "0" to half the number of tracks to be sought, and a count-down operation is performed until the subsequent target recording track is reached.

That is, the counter circuit 12 receives a start signal SsT and an up/down signal CN T manually input from the control circuit 11.
From the rising edge of uo, the traverse count signal Stv indicating the number of tracks traversed during seek is sequentially counted up, and then the up/down signal C is counted up.
When N T up falls at the timing when half of the number of tracks to be sought is counted in the control circuit 11, a countdown operation is performed, and the count value CT is sent to the following D/A converter 13.

As a result, from the D/A converter 13, as shown in FIG. 6(a), while the coarse actuator 18 moves to the recording track t2°, which is half the number of tracks txt to be sought, The drive voltage V which increases sequentially is applied to the switch circuit 15. Addition circuit 16. It is supplied to the coarse actuator 18 via the drive circuit 17.

Subsequently, while the coarse actuator 18 moves from the recording track t2°, which is half of the number of tracks ttl to be sought, to the target recording track ti1, the up-down signal CN T un (FIG. 6(b) )
) falls, and the counter circuit 12 performs a countdown operation, so that the drive voltage V, which decreases sequentially as the coarse actuator 18 moves, is applied to the coarse actuator 18.
The traverse count signal STV is used as a whole to form a position servo loop based on the amount of movement of the coarse actuator 18.

The moving speed SV of the coarse actuator 18 is shown in FIG. 6(C).
As shown in FIG. 1, based on the speed signal Sv obtained from the speed sensor circuit 19, while the coarse actuator 18 moves to the recording track t2°, which is half of the number of tracks t21 to be sought, the speed servo loop accelerates at a high speed. Controlled to stand up.

On the other hand, since sufficient acceleration is obtained while the coarse actuator 18 moves from the recording track two, which is half of the number of tracks t21 to be sought, to the target recording track til+, a negative feedback circuit is formed in the speed servo loop. As a result, the number of remaining tracks up to the target recording track t21 and the moving speed Sv of the coarse actuator 18 converge to "0", and when the coarse actuator 18 reaches the target recording track tz+, the moving speed decreases. It is possible to reliably control Sv to "0".

According to the above configuration, while the coarse actuator 18 moves from the start of the seek operation to the recording track t2° which is half of the number of tracks t2□ to be sought, the coarse actuator 18 increases sequentially as the coarse actuator 18 moves, and then the rough While the actuator 18 is moving from the recording track t2o, which is half the number of tracks to be sought, to the target recording track t21, the coarse actuator 18 is driven and controlled using a drive voltage V that gradually decreases as the coarse actuator 18 moves. Accordingly, when the coarse actuator 18 moves to above the target recording track tz+ to seek,
The moving speed Sv of the coarse actuator 18 can be reliably controlled to "0".

[Problems to be Solved by the Invention] By the way, since the above-described seek device uses the electromotive force generated when crossing a magnetic field as a speed sensor signal, the time point at which the coarse actuator 18 starts moving is ,
At the point where the coarse actuator 18 slows down near the target track, it becomes extremely difficult to obtain an accurate velocity signal (SV).

In other words, when the movement speed of the coarse actuator is low, the signal level induced in the detection coil constituting the speed sensor decreases, and the S/
N reduced speed signals are output.

Then, especially 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 actually reach zero when it reaches the target track. .

In addition, in order to smoothly converge the speed of the actuator at the target track, instead of using the distance X to the target track as the control amount of the actuator, the function √x
However, there is a problem in that a separate D/A converter or ROM table is required to calculate -''T, which complicates the circuit scale.

[Means for Solving the Problems] The present invention solves these problems, and easily calculates the distance X to the target track, which is the target value, and the distance X smoothly using the IC circuit. It was created with the purpose of obtaining a function i that gives a speed servo that makes the speed 0, and is a D/A converter that obtains the value of an analog signal f from data counting the distance to the target track. , means for obtaining the analog signal F and the analog signal X from the D/A converter in a time-division manner, and forming a differential signal at the timing when the analog signal A speed information sentence indicating the speed is formed.

[Operation] Extracts the target track number to be sought and the number of tracks up to the target track as data from the current track number, and supplies this data to a D/A converter configured to output a J function. distance W to the target track
Convert lx to an analog signal with √x.

Furthermore, this analog signal F is configured to be fed back as a reference voltage to the D/A converter, and the value of X is determined by converting data into an analog signal based on this fed back reference signal. FT and X can be calculated in one time division manner by inputting data up to the target number of tracks to one D/A converter.

In addition, since the moving speed of the actuator can be calculated by differentiating X, the speed servo circuit of the optical head can be constructed with a simple IC circuit.6 [Embodiment] Fig. 1 shows an embodiment of the seek circuit of the present invention. 20 indicates, for example, the total number of tracks on the optical disc is to,
In the case of 000 lines, an up/down counter (hereinafter simply referred to as a counter) is loaded with 16 bits (8 x 8 bits) data, and 21 is the 14 output from the counter 20.
This is a 14-8 bit decoder that takes in, for example, the upper 8 bits of data from the bit data and outputs an "H" level signal to one of 28 output terminals.

Note that the output of this bit decoder 21 is voltage-divided by a series resistor (r I * r l...r,) to which a reference voltage 'V r e t is applied in order to perform D-A conversion. A plurality of (256) switches (S, , S, . . . , Sn) are sequentially opened and closed to select the selected voltage.

The counter 20 stores the number of tracks up to the target track (
14 bits), bit data indicating the direction, and 1 bit data indicating whether the analog signal of the seek target value should be linear (X) or smooth (-rM) are loaded, and the actuator moves. A signal Srv, which is obtained by shaping a traverse signal (tracking error signal) outputted in the middle by a comparator C0NI, is supplied as a clock signal. The clock signal STV is used to subtract the contents of the counter 20, which is normally loaded with data indicating the number of tracks up to the target track.

In addition, the reproduced RF signal output during traverse is shaped by a comparator CON, and a D-flip-flop (D-
FF) 22 detects the relative direction of the beam spot and the optical disk.

When the direction detection signal and the jump direction match, the counter 20 is set to a subtracting mode via the EX-OR circuit 23, and when they are different, the counter 20 is set to an incrementing mode.

14-8 bit decoder 21, reference voltage V r e f
, voltage dividing resistors (r l+ rl...rn) and switches (S, , S,...Sn), each voltage dividing resistor By weighting the output position of the 14-8 bit decoder 21 or by weighting the output position of the 14-8 bit decoder 21, an output signal of the J function can be obtained.

Therefore, as shown in FIG. 2, an analog signal is output to the output line of the D/A converter such that y=F for input data y.

The analog signal FT on the output line is passed through the buffer amplifier BA to the sample switches S,,S,.

S3. is supplied to,S,,,S,.

Each sample switch s, s, s, , s4°S6 is alternately switched by a sample clock CPH (not shown). For example, at the first timing P,
The reference voltage V r e f is the second buffer amplifier BA2.
The signal is supplied to the D/A converter via the D/A converter. At this point, as shown in FIG. 3(a), the analog signal f is outputted to the output line and sent to the sample hold circuit SH via S4.

is memorized. Then, the output shows FT, which is a function of the distance to the target track, as shown in FIG. 3(b).

It is also stored in the sample hold capacitor Cs via the switch S3.

Next, at timing N, as shown in FIG. 3(a), the reference voltage v1. ．． Sample hold capacitor C instead of
Since the analog signal FT of 3 is supplied to the D/A converter, the data being output at this time becomes FT-r=X, and becomes a cross-conversion output where y=x. This analog signal X is then supplied to the second sample and hold circuit S H2 via switch S8, and its voltage is
) shows distance information to the target truck.

The analog signal X held in the second sample and hold circuit S
d t =large.

In other words, the actuator speed information can be obtained as large.

This speed information statement and the first sample hold circuit SH
, (function of the distance to the target track) is subtracted in a comparator 25 to form a seek drive signal Sd for the actuator 26.

Note that 27 is a seek drive signal Sd depending on the jump direction.
This is an inverting circuit that inverts the polarity of .

The seek device of the present invention uses one D/A converter in time division as described above, and outputs an analog signal X proportional to input data y and an analog signal √x that is a function of the analog signal X. As a result, the analog signal FT and speed information text required to smoothly converge the actuator speed to the target track can be obtained with a simple circuit, and it is also easy to integrate into an IC. .

Note that, in order to increase the jump speed of the actuator, it is preferable to use the distance X to the target track as the target value at the start of the seek.

In the case of the present invention, when setting the target value to X, another timing signal is supplied to the switch S4 via the switching circuit SW, and P
The configuration is such that the timing and the N timing are inverted, so that the analog signal X can also be obtained from the first sample and hold circuit SH.

However, in this case, it becomes difficult to converge the speed of the actuator to 0 at the target track, and the access time increases.

Therefore, when the output data of the counter 20 reaches, for example, half of the target track, a flag is attached to the output data of the counter 20 so as to output the analog signal FT as described above, and this data is used to control the switching circuit SW. You may also do so.

[Effects of the Invention] As explained above, the optical disk seek circuit of the present invention employs a D/A converter that converts the data of the number of tracks up to the target track into an analog signal F signal during a seek, and By operating the /A converter in a time-sharing manner, the analog signal X can be obtained simultaneously, so the signals f, This can be obtained without using a ROM table, and has the effect that the seek circuit can be easily integrated into an IC.

FIG. 5 is a block diagram of a conventional seek device, and FIGS. 6(a), (b), and (c) are waveform diagrams showing the operation of FIG. 5.

In the figure, 20 is an up-grain counter, 21 is a 14-8 bit decoder, 24 is a differential circuit, and 26 is an actuator.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a D/
Graphs showing conversion curves of A converter, Figure 3 (a) (b)
(c) is a graph showing the curves of analog signal X and analog signal F.

Claims (2)

[Claims] (1) In an optical disk seek circuit in which the moving speed of the optical head is ■, the distance to the seek target track is x, and the distance x is the target value, the speed servo is applied at the moving speed ■. A D that outputs an analog signal x by outputting √x as an analog signal serving as a target value for distance data to a target track, and feeding back the analog signal √x as a reference voltage at a second timing. 1. A seek circuit for an optical disc, characterized in that a /A converter is provided, and a drive signal for the optical head is formed by an output value obtained by subtracting the analog signal √x and the differential value ▪ of the analog signal x. (2) At the start of the seek, the analog signal x is used as the target value.
The optical disk seek circuit according to claim 1, wherein the optical disc seek circuit is configured to output.