JPS6166267A - Track access device - Google Patents

Abstract

PURPOSE:To lock in quickly and stably the tracking servo by driving a fine control means in response to the drive signal of a rough control means in a drive mode of this rough control means and therefore attaining the accurate reproduction of the signals sent from a pickup even in an access mode. CONSTITUTION:A disk 1 is revolved by a motor 2 via a control circuit 12, and a control circuit 11 performs the focus and tracking servo operations. A microcomputer 10 delivers an access command for execution of a basic action. In this case, a tracking servo loop is opened and a radius position detecting circuit 6 detects the distance to an access target. Then the target shift speed of a carriage corresponding to said detected distance is delivered from a target speed generating circuit 7. The difference between a target speed and the actual speed of a pickup 3 detected by a relative speed detecting circuit 5 to the disk 1 is obtained through an amplifier 8. Then a linear motor 4 is driven in accordance with the difference signal obtained from the amplifier 8. Thus the servo is applied. A drive current of the motor 4 is detected 13 and multiplied 14 by a prescribed coefficient for fine control of a beam spot.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a trunk access device in an information recording and reproducing apparatus that records or reproduces information on the trunk of a disc such as a video disc or a digital audio disc.

[Prior Art] In such an information recording/reproducing apparatus, for example, in order to search for a desired image or the like, the recording/reproducing means may be relatively moved in the radial direction of the disk at high speed. FIG. 3 shows a device for such a case, which was proposed by the present applicant as U.S. Pat. In the figure, numeral 1 denotes a disk on which tracks are formed concentrically or spirally, and is rotated by a spindle motor 2. As shown in FIG. Reference numeral 3 denotes a pickup as a recording/reproducing means, which reproduces information by irradiating the disk 1 with, for example, a laser beam.

Reference numeral 4 denotes a linear motor as a rough adjustment means for roughly adjusting the relative position of the pickup 3 in the disk radial direction, and 1 moves the pickup 3 mounted on a carriage (not shown) in the radial direction of the disk 1 at high speed. 5 is a detection circuit that detects the relative speed between the beam spot on the disk (pickup 3) and the track from the signal reproduced by the pickup 3; 6 is a detection circuit that detects the direction in which the beam spot crosses the track from the signal reproduced by the pickup 3. 67, which is a detection circuit that detects the position of the beam spot (pickup 3) in the radial direction by counting the number of beams and detecting the position of the beam spot (pickup 3) in the radial direction.
8 is a target speed generation circuit that receives the output of the detection circuit 6 and generates a target transport speed signal of the carriage corresponding to the radial position of the pickup 3; 8 is the target speed of the carriage from the generation circuit 7 and the detection circuit 5; A differential amplifier 69 is a linear motor drive control circuit that drives the linear motor 4 in response to a signal from the differential amplifier 8. A microcomputer 10 controls the operations of various circuits. 11 is a focus/tracking drive control circuit that controls the focus state and tracking state of the beam emitted from the pickup 3 on the disk. 6 Although not shown, it finely controls the relative position of the pickup 3 with respect to the track of the disk 1. The tracking control means as a fine adjustment means includes a mechanism for controlling the position of the objective lens and mirror of the pickup 3, and the like.

12 is a spindle drive control circuit that drives the motor 2.

However, a command was issued from the microcomputer 10,
The spindle drive control circuit 12 rotationally drives the motor 2,
While the focus/tracking drive control circuit 11 is performing focus control and tracking control, when the microcomputer 1o further issues an access command to move the pickup 3 to a track at a predetermined address at high speed, the tracking servo loop opens. Then, the position detection circuit 6 detects the distance from the current position of the pink-up 3 to the target track to be accessed. Based on this detection output, the generating circuit 7 outputs a target moving speed signal of the carriage. -6 Since the relative speed detection circuit 5 detects and outputs the current speed of the carriage, the differential amplifier 8 outputs a signal to drive the carriage at the target speed.

In response to this signal, the linear motor drive control circuit 9 issues an output to the linear motor 4, so that the carriage is moved at a high speed at the target speed. Therefore, the pickup 3 mounted on the carriage is controlled to move at a speed corresponding to the distance to the target address.

When the pick-up 3 is being transported at high speed in the radial direction of the disk, when the radial position detection circuit 6 detects that the pickup 3 has crossed the target number of tracks, the microcomputer 10
stops the transport by the linear motor 4 and closes the tracking servo loop. Therefore, the beam spot follows a predetermined track. In this way, it approaches the track of the target address and further drives the fine adjustment means to reach the target track.

[Problems to be Solved by the Invention] However, in such conventional devices, since the tracking actuator as a fine adjustment means supports the objective lens etc. with respect to the pickup housing by a spring or the like, fine adjustment is difficult. When the coarse adjustment means on which the adjustment means is loaded is being transported at high speed.

The tracking actuator (objective lens) as a fine adjustment means vibrates with respect to the carriage, and this can be expressed by a transfer function as shown in FIG. Here, M is the weight of the moving part of the linear motor 4 (carriage), K1 is the thrust constant of the linear motor 4, m, a
, respectively represent the weight, velocity resistance, and spring constant of the movable part of the tracking actuator. That is, the transfer function of the linear motor 4 is Kl/MS, and the transfer function of the objective lens is (-m s") / (m s”+c s+
k), the speed of the objective lens seen from the carriage is V
=I(ni/MS)(-ms”/(ms”÷cs+
k)), where the equation is the drive current of the linear motor 4.

When the objective lens vibrates relative to the carriage in this way, the objective lens moves from its neutral position, and the beam spot also moves on the detector (light receiving element) for signal reproduction or tracking control, causing tracking errors. This causes a DC offset of the signal and a level fluctuation of the reproduced signal. As a result, accurate detection of the relative velocity and radial position described above becomes difficult. Furthermore, since the objective lens vibrates, it is difficult to lock in immediately when approaching the vicinity of the target address and performing tracking pull-in. This has also been a hindrance to speeding up and increasing the speed of access operations.

[Means for solving problems]

FIG. 1 shows the structure of an information recording and reproducing apparatus according to the present invention. In FIG. 1, parts corresponding to those in FIG. In addition to the configuration shown in FIG. 1, this device has a detection correction circuit consisting of a drive signal detection circuit 13 and a coefficient circuit 14 (which may be integrally configured as one circuit).

The detection circuit 13 detects the drive current and drive voltage to the linear motor 4. The coefficient circuit 14 calculates the detection output from the detection circuit 13 using a predetermined coefficient, amplifies or attenuates it, and outputs the result. The output of the coefficient circuit 14 is supplied to the drive control circuit 11, and a tracking actuator serving as a fine adjustment means is driven.

[Function] With the spindle drive control circuit 12 controlling the motor 2 to rotate the disk 1, and the focus/tracking drive control circuit 11 performing focus servo and tracking servo,
The basic operation when an access command is issued from the microcomputer 10 is the same as that described above.

In other words, the tracking servo loop is used as an oven,
The distance to the access target is detected by the radial position detection circuit 6, and the target speed generation circuit 7 generates a target moving speed of the carriage corresponding to this distance. The difference between the actual speed of the pickup 3 relative to the disk detected by the relative speed detection circuit 5 and the target speed is obtained by the differential amplifier 8, and the linear motor drive control circuit 9 controls the linear motor 4 in response to this difference signal. , the servo is applied so that the carriage moves at a target speed corresponding to the remaining distance.

On the other hand, the drive current of the linear motor 4 is detected by the detection circuit 13, and multiplied by a predetermined coefficient by the coefficient circuit 14. This signal is supplied to the tracking actuator via the drive control circuit 11, and the position of the beam spot is finely adjusted.

The transfer function between the carriage speed of the drive current in the linear motor 4 and the speed V of the objective lens viewed from the carriage is as shown in FIG. Here, X represents the coefficient of the coefficient circuit 14, and B and L represent the magnetic flux density and line length of the tracking actuator, respectively. That is, the transfer function of the coefficient circuit 14 is
M)m/(ms+c+/s)). Therefore, find the value of the coefficient X that makes V zero.

X=:K11l/MBL. In other words, this value is a coefficient that expresses the acceleration per unit current of the linear motor 4 by the acceleration per unit current of the tracking actuator.Since it is set to a coefficient or this value, it is independent of the drive current of the linear motor 4. The speed V can be made zero. This means that even when the carriage is being transported at high speed, the objective lens does not vibrate on the carriage and remains substantially stationary.

Thereafter, when the detection circuit 6 detects that the pickup 3 has crossed the target number of tracks.

The microcomputer 10 controls the linear motor drive control circuit 9 to stop the linear motor 4 from transporting the pickup 3, closes the tracking servo loop as a fine adjustment control means, and causes the beam spot to follow a predetermined track. This is the same as in the conventional case.

In the above case, the relative moving speed and radial position of the pickup 3 with respect to the carriage are detected from the reproduction signal of the pickup 3.

The carriage may be provided with a speed sensor, a position sensor, etc., and these may be detected from sources other than the reproduction signal, and the carriage may be driven by a rotary motor or the like instead of a linear motor. Further, the tracking actuator may also be supported by a spring or may have a configuration other than a near motor.

[Effects] As described above, in the present invention, when the coarse adjustment means is driven, the fine adjustment means is also driven in response to the drive signal, so that the fine adjustment means does not vibrate during access. , the signal can be accurately reproduced from the pickup even during access, and tracking servo lock-in can be performed quickly and stably. Therefore, faster access is possible. Furthermore, since the relative speed and radial position can be detected from the reproduced signal, the number of parts can be reduced and the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the information recording and reproducing apparatus of the present invention, and FIG.
FIG. 3 is a diagram showing the transfer function, FIG. 3 is a block diagram of a conventional information recording/reproducing apparatus, and FIG. 4 is a diagram showing the transfer function. 1...Disc 2...Spindle motor 3...
・Pickup 4...Linear motor 5...Relative speed detection circuit 6...Radial position detection circuit 7...Target speed generation circuit 8...Differential amplifier 9...
・Linear motor drive control circuit 10...Microcomputer 11...Focus/tracking drive control circuit
12...Spindle drive control circuit 13...Drive signal detection circuit 14...Coefficient circuit or higher

Claims (6)

[Claims] (1) In an information recording and reproducing device that records or reproduces information on a disk in which tracks are formed concentrically or spirally, a recording and reproducing means is used to roughly adjust the relative position of the recording and reproducing means in the radial direction of the disk. The apparatus comprises an adjustment means and a fine adjustment means for fine adjustment, detects a signal for coarsely adjusting the position of the recording and reproducing means, calculates the signal with a predetermined coefficient, and coarsely adjusts the position of the recording and reproducing means. , a track access device characterized in that the position of the recording/reproducing means is finely adjusted at the same time using the calculated signals. (2) The apparatus has a detection means for detecting at least one of the relative position and relative velocity of the recording and reproducing means in the radial direction of the disk, and the detecting means detects the relative position and relative velocity of the recording and reproducing means from the reproduction signal obtained from the recording and reproducing means. The track access device according to claim 1, wherein the track access device detects a relative position or relative velocity. (3) The detected signal for coarsely adjusting the recording/reproducing means is an input signal to an actuator for coarsely adjusting the position of the recording/reproducing means. truck access equipment. (4) The track access device according to claim 3, wherein the input signal is a drive current signal to the actuator. (5) The track access device according to claim 3, wherein the input signal is a drive voltage signal to the actuator. (6) The track access device according to any one of claims 1 to 5, wherein the detection of the coarse adjustment signal and the calculation of the signal are performed integrally.