JPH035974A - Seek device for optical disk - Google Patents

Abstract

PURPOSE:To shorten time for moving a tracking actuator by acceleration and deceleration even when a target track is seeked by providing a means to viriably control the pulse width of a single pulse generating means according to a moving distance to the target track. CONSTITUTION:The output pulse of a single pulse generator 2 is made variable by the control signal of a pulse width setting means 6. The tracking actuator kicked by a track jump command is controlled to be accelerated by the output of the single pulse generating means at first, to be decelerated at a prescribed rate next and to be a prescribed speed in the target track. Thus, the seek time to the target track is shortened and operation is controlled to a tracking state in the target track without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc seek device suitable for moving a tracking actuator to seek a target track.

[Summary of the Invention] The optical disk seek device of the present invention includes an edge detection means for detecting a zero-crossing point of a tracking error signal, and an edge detection means for detecting a zero-crossing point of a tracking error signal, in order to detect a track of an optical disk that a laser beam crosses during seeking. includes a single pulse generating means for outputting a signal with a predetermined pulse width triggered by the output of the above, and a control means for changing the output pulse width of the single pulse generating means depending on the number of tracks traversed during a seek, and a jump command. The speed at which the tracking actuator is moving is controlled by the output of the single pulse generating means, and the seek speed is controlled so that the access operation is performed smoothly on the target track. be.

[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 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. 6 shows an outline of such an optical head, in which a pair of optical discs 11 traverses a recording track 13 formed on a magneto-optical disc 12 and extends in the radial direction of the optical disc. It is made up of a coarse actuator (linear motor) 15 arranged to slide with respect to a guide, and a fine actuator (two-axis mechanism) 16 mounted on the coarse actuator 15.

17 indicates an objective lens that irradiates the magneto-optical disk 12 with a laser beam emitted from the micro actuator 16;
By tracking the recording track 13 of the magneto-optical disk 12 with this laser beam, information can be read from or written to the rotating magneto-optical disk 12.

Further, the seek operation for accessing the optical head 11 to a desired track on the magneto-optical disk 12 is performed by supplying a predetermined drive signal to the coarse actuator 15 or the fine actuator 16 of the optical head 11 at -M to set the beam spot. It moves in the radial direction of the magneto-optical disk 12 to seek a target track.

Incidentally, in such an optical disk device, a speed servo is applied to the actuator during seek in order to reliably access the target track, and the speed of the tracking actuator is controlled so that the access operation is performed smoothly on the target track. It is preferable to do so.

FIG. 7 shows an overview of the optical disk seek device previously proposed by the present applicant, in which 1 is an O-cross detection unit that detects the O-cross point of the tracking error signal during traversal, and 2 is a monostable multi-bi break. shows. The output of the monostable multivibrator 2 is connected to the b contact of the input switching circuit 5 via the OR gate 3 and the first inversion switch 4a, and is supplied to the tracking actuator.

In this seek device, during normal recording and reproducing operations, the a contact of the input switching circuit 5 is selected, and the tracking error signal Et is supplied to the tracking actuator via this a contact to apply tracking servo.

When accessing the target track by supplying a jump command to the tracking actuator, the b contact of the input switching circuit 5 is selected, and the first jump direction signal SJD instructs the movement direction of the tracking actuator.
Then, the second switches 4a and 4b are switched, and the kick pulse Sxp is supplied via the OR gate 3 and the first inversion switch 4a, as shown in FIG.

Since the tracking actuator is accelerated in a predetermined direction by this kick pulse, the tracking error signal Et supplies a signal during traversal (traverse signal E,) to the 0-cross detector 1, as shown in FIG. Then, at the O cross point of the traverse signal E, the trigger signal T1
is supplied to the monostable multivibrator 2, and a single pulse P having a constant pulse width t0 is supplied to the tracking actuator via the OR gate 3 and the first reversing switch 4a.

Note that this single pulse P is biased (-1/2xV) by resistors R and R, and if it becomes a deceleration voltage below the 0 level, the tracking actuator is activated at the level shown by diagonal lines. The tracking actuator will be accelerated above the 0 level.

Therefore, as shown by the moving speed V in Figure 8, the tracking actuator's moving speed V gradually increases immediately after the kick, but reaches a constant speed when the pulse ratio of the single pulse P becomes about 50%. A decreasing speed servo is added.

The number of tracks crossed by a jump of the tracking actuator is detected by a counter (not shown) or by the output of an address decoder. For example, when 2N-1 0 cross points are detected during an N track jump, the contact of the input switching circuit 5 is activated. C is selected and a braking pulse S IIR of a predetermined width is applied via the second reversing switch 4b to control the movement speed to almost 0 at the target track, and at the same time, the a contact of the input switching circuit 5 is turned on. Then, the tracking error signal Et is detected and N tracks are accessed.

[Problems to be Solved by the Invention] The theta method as described above is particularly useful when performing several hundred track jumps because a speed servo is added each time a track is crossed during traverse. , can be at a constant speed at the final target track.

Therefore, this final speed is the braking pulse 5I
If the setting is made so that when IR is applied, the value becomes close to 0 in a period of half a track (the speed at which the tracking servo is applied), there is an advantage that the target track can be reliably accessed.

However, since the tracking actuator is controlled to have a constant speed while it is moving, there are disadvantages in that the utilization rate of the acceleration power source is poor and the seek speed is slow.

[Means for Solving the Problems] The present invention has been made with the aim of solving such problems, and includes a means for detecting the position and number of tracks crossed during a seek operation, and a means for detecting the number and position of tracks crossed during a seek operation, and a means for detecting the number and position of tracks crossed during a seek operation. and a means for supplying the output of the single pulse generating means as a jumping signal, the pulse width of the single pulse generating means being variable depending on the distance traveled to the target track. It is equipped with a means for controlling.

[Operation] The tracking actuator kicked by the track jump command is initially controlled to be accelerated by the output from the single pulse generation means, and then decelerated at a predetermined rate to reach a predetermined speed on the target track. Therefore, the seek time to the target track can be shortened, and the tracking state can be reliably controlled at the target track.

[Embodiment] FIG. 1 is a block diagram showing the principle of a seek device of the present invention, and FIG. 2 shows its operating waveforms.

In FIG. 1, 1.2.3 indicates a 0-cross detector, a single pulse generator consisting of a monostable multi-by-break, etc., and an OR gate, as in FIG. 7.

Also, 4a and 4b are the first. and a second inversion switch, which is switched by a control section (not shown) in accordance with the jump direction.

Note that 5 is an input switching circuit.

In the present invention, the output pulse of the single pulse generator 2 is configured to be variable by the control signal of the pulse width setting means 6.

As will be explained later in the embodiments, the pulse width setting means 6 basically receives information on the number of tracks up to the seek target value, and has a narrow pulse width at the jump start point compared to the monostable multivib break 2. However, when jumping to the target track, the
This control is performed so that the pulse width becomes wider as the number of ν decreases.

Since the present invention is provided with the above-mentioned pulse width setting means 6, a jump command is input and the input switching circuit 5
When a contact point is selected and a kick pulse SKP is input, the tracking actuator is accelerated as in the conventional case. Then, as shown in FIG. 2, every time one track is crossed, a single pulse PM, which becomes a deceleration pulse, is output from the single pulse generator 2 in response to the trigger signal Tg from the O-cross detector 1. Initially this single pulse P,4
Since the pulse width of is to, which is extremely narrow, the tracking actuator continues to rapidly accelerate.

However, after that, due to acceleration, the traverse signal E
At the same time as the period of 11 becomes shorter, the width of the single pulse P increases (tr - t 2 - tz ) L. When the amount of deceleration signal becomes larger than the amount of acceleration signal, the tracking actuator enters a region where it receives deceleration, Its speed gradually decreases. Then, 2N half a period before the target track N
At point -1, the pulse width tzs-+ of the single pulse PM becomes maximum, and at this point the C contact of the input switching circuit 5 is selected,
By applying the braking pulse SBR, the tracking speed is reduced to such a speed, and by selecting the contact point a of the input switching circuit 5 at this time, the tracking state for the target track can be achieved.

As explained above, in the seek device of the present invention, the single pulse PM for speed servo applied during traverse
is configured to change depending on the position of the tracking actuator during movement, and when the tracking actuator is sufficiently far from the target track, a drive signal in an acceleration state is supplied, and the drive signal changes from the midpoint position to the target track to a deceleration state. Since the jump time to the target track is controlled to be as follows, the jump time to the target track is shorter than that of the conventional method.

[Embodiment (1)] FIG. 3 shows an embodiment of the present invention in which the single pulse generating means is implemented by a digital counter.
l is the O cross comparator la.

D-flip-flop lb, lc and ex-OR circuit 1
d shows a zero-cross detector formed by d.

As shown in FIG. 4, the configuration of this 0-cross detector 1 converts the traverse signal ElI generated during seek into a pulse signal Ep that is inverted at the 0-cross point, and converts this pulse signal into D - The pulse signals E, , E, □ are formed by delaying the period of the clock signal (CLK) by the foot flops lb and 1c, and both of them are e
By supplying it to the x-OR circuit 1d, an edge pulse P at the 0 cross point is output.

This edge pulse Pg is input to a single pulse generator 2 that generates a single pulse, which is composed of a B counter 2b that counts the clock CLK, an A counter 2a that subtracts by the edge pulse, and a flip-flop 2c. . Then, Bka Kunku 2 of this single pulse generator 2
At the same time, the flip-flop 2b is set.

Also, it is input to the clock terminal of the A counter 2a which presets counting data in the B counter 2b, and the A counter 2a
The output value is controlled to decrease at a constant rate each time the edge pulse P6 arrives.

The B counter 2b counts the clock signal CLK, and 21=
When W counts, the carry output C7 stops counting and resets the flip-flop 2c.

Let N be the number of tracks to the seek target track,
As shown in FIG. 4, when the first edge pulse Pg is output, the flip-flop 2c is set, and the count data of 2N+C is preset to the B counter 2b from the A counter 2a (C is a constant).

The B counter becomes W by counting W-2N-C clock CLK, and the carry C output at that time becomes W.
y resets the flip-flop 2c and disables its own counter.

Next, at the same time as the second edge pulse Pε is output, the flip-flop 2C is reset, and the A counter 2
Count data is preset from a, and this count data is set to a value decreased by -1 from the previous preset value, that is, 2N-1-C.

Therefore, since the B counter 2b outputs a carry CA when counting W-2N-1-0, the pulse width of the single pulse generated by the second edge pulse is determined by the period of the clock signal CLK being tc. t CX (W-2N+
1-C), and only the pulse width tc becomes wider.

Thereafter, a single pulse will be output from the flip-flop 2C every time the edge pulse PE arrives by a similar operation, but when the number of traverse tracks becomes 2N-1, the width of the first single pulse is teX ( W−C), and this value becomes a constant that sets the final speed of the tracking actuator just before the target track.

Then, when the count data of the A counter 2a becomes C, the output of the comparator 7 is inverted, a signal for selecting the C contact of the input switching circuit 5 is output from the seek controller 8, and the braking pulse S aq is supplied as described above. be done.

Thereafter, contact point a is selected to access the seek target track.

Note that the seek controller 8 controls the direction F/of the target track.
At the same time as switching the changeover switches 4a and 4b by H, an initial preset value for the number of tracks N up to the target is supplied to the A counter 2a.

[Example (2)] FIG. 5 shows another embodiment of the invention.

In this embodiment, the D-flip-flop 1e and the ex-OR
1f is added, and the edge pulse PP, including the edge pulse Pt+-n one clock before, is output from ex-OR1f, and a direction detector 10 is provided to detect the relative moving direction of the optical disk and the spot. ,
A comparator 10a detects the 0 cross point of the RF multiplied signal, and detects the level of this output and the traverse signal.
- A flip-flop 10b is added.

The output of the D-flip-flop 10b is used to detect whether the spot is moving toward the outer circumference or the circumference of the optical disk, and the switch 4a is reversed.

Further, in order to output the driving signal of the tracking actuator for jumping as positive and negative logic signals, a D counter 2d is added, and a second flip-flop 2e is provided which is reset by the D counter 2d.

Furthermore, in this embodiment, an up-down type counter is adopted as the A counter 2a that outputs information up to the target track, and the up-down control terminal is connected to the output of the D-flip-flop 10d of the direction detector 10 described above. An exclusive OR output of the output of the control signal F/H instructing the jump direction is supplied.

Therefore, when the speed of the tracking actuator decreases and the relative moving direction of the beam changes due to the eccentricity of the optical disk, for example, when the beam moves away from the target track, the count data supplied by the B counter 2b increases. This allows for even more accurate speed servo control.

Also, the newly added D counter 2d loads the B counter 2 at a timing one clock before the B counter 2b is loaded.
Since the configuration is such that the count value m-1 bit, which is obtained by subtracting 1 bit from the count value of b, is loaded, for example, when the tracking actuator moves quickly and carry CY is not output, this value is stored in the D counter 2d. When the count value B immediately before being loaded is loaded into the B counter 2b, W-Bc+1 clocks are counted and the second flip-flop 2e is reset.

Therefore, when the speed of the tracking actuator is high, a deceleration pulse corresponding to the speed is outputted from the second flip-flop 2e and outputted from the operational amplifier OP as a negative deceleration pulse. It is no longer necessary to form deceleration pulses using such a DC bias circuit, and it is possible to reduce power consumption and improve seek speed at the same time.

Furthermore, according to the third embodiment, even if there is a change in speed due to eccentricity of the optical disk during a track jump, accurate speed servo is performed for the target track, so access to the target track can be performed with even more precision. can be done.

[Effects of the Invention] As explained above, when performing a track jump, the optical disc seek device of the present invention uses a single pulse whose pulse width changes depending on the number of tracks up to the target track as a track jump drive signal. Therefore, even when several hundred track jumps are performed and a target track is sought, the movement time of the tracking actuator can be shortened by acceleration and deceleration.

Furthermore, since the seek speed immediately before the target track is managed, it is possible to stably enter the tracking state, which is an excellent advantage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the principle of the seek device of the present invention, FIG. 2 is a signal waveform diagram showing the operation of FIG. 1, FIG. 3 is a circuit diagram showing the first embodiment of the present invention, and FIG. FIG. 4 is an explanatory waveform diagram of a single pulse, and FIG. 5 is a circuit diagram showing another embodiment of the present invention.
FIG. 6 is an explanatory diagram of an optical head and an optical disk, FIG. 7 is a block diagram of a seek device showing the prior art of the present invention, and FIG. 8 is a signal waveform diagram showing the operation of FIG. 7. In the figure, l is a 0 cross detector, 2 is a single pulse generator, and 6
indicates the pulse width setting section. Figure 4

Claims (3)

[Claims] (1) traverse track number detection means for detecting the number of tracks that the tracking actuator that is kicked by the jump command signal crosses during seek; an edge detection means for detecting the 0-crossing point of the traverse signal; and detection by the edge detection means. a single pulse generating means triggered by the output of the single pulse generating means; a control means for limiting the output pulse width of the single pulse generating means in accordance with the number of tracks to be traversed; A seek device for an optical disc, characterized in that the seek device is configured to supply a signal to the tracking actuator. (2) The optical disc according to claim 1, wherein the single pulse generating means is constituted by a down counter whose predetermined count value is preset by the output of the edge detecting means. Seek device. (3) Claim (2) characterized in that the transverse track number detection means is configured to add or subtract the output of the edge detection means depending on the relative movement direction of the optical disk and the tracking actuator. The optical disc seek device described in .