JPH0414432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a track access device in a disc recording/reproducing apparatus such as a video disc player or a digital audio disc player.

[Conventional technology]

Disc recording and reproducing devices such as video disc players and digital audio disc players are equipped with a fine adjustment means for finely adjusting the position of a pick-up for recording or reproducing information on the disc with respect to a track formed on the disc. Coarse adjustment means is provided for moving the means in the radial direction of the disk and coarsely adjusting its position. In such an apparatus, for example, when accessing (searching) a predetermined track, the coarse adjustment means is driven to move the pickup in the radial direction of the disk at high speed. At the time of such access, the applicant shall:
He has previously proposed a device in which the fine adjustment means mounted on the coarse adjustment means does not vibrate (Utility Application No. 59-115086 (Utility Model Application No. 61-33275)). A similar application is JP-A No. 59-165278. FIG. 4 is a block diagram of such a conventional device. In the figure, 1 is a disk, which is rotated by a motor 2. As shown in FIG. A pickup 3 includes an objective lens 4, and is placed on a carriage 5. Reference numeral 6 denotes a linear motor as a coarse adjustment means for moving the carriage 5 in the disk radial direction and roughly adjusting the position of the pickup 3. Reference numeral 7 denotes a relative speed detecting means for detecting the relative speed of the pickup 3 with respect to the disk 1. For example, from the playback signal of the pickup 3, the relative speed at which the beam irradiated from the pickup 3 to the disk 1 crosses the track is detected.
Reference numeral 8 denotes a radial position detection circuit which detects the direction and number of beams crossing the track from the reproduction signal of the pickup 3, and detects the position of the pickup 3 in the radial direction on the disk 1. A target speed generating circuit 9 generates a signal corresponding to a target moving speed of the carriage 5 in the disk radial direction in response to a signal from the radial position detecting circuit 8. 10
is a differential amplifier that outputs the difference between the signal from the relative speed detection circuit 7 and the signal from the target speed generation circuit 9, and the linear motor drive control circuit 11 drives the linear motor 6 in response to this difference output. It's becoming like that. Reference numeral 12 denotes a current detection circuit that detects the driving current of the linear motor 6 as its driving force. The signal output from the current detection circuit 12 is processed by a predetermined coefficient x in a coefficient circuit 13, and then supplied to a focus/tracking drive control circuit 14, which finely adjusts the position of the objective lens 4 (beam) relative to the track, for example. A tracking control means (actuator) serving as a fine adjustment means is driven. Further, the focus/tracking drive control circuit 14 detects the focus state from the signal of the pickup 3 and controls the focus of the objective lens 4. 15 is a spindle drive control circuit that drives the motor 2.
16 is a relative speed detection circuit 7 and a radial position detection circuit 8
This is a microcomputer that monitors the output signals of the linear motor drive control circuit 11, focus and tracking drive control circuit 14, spindle drive control circuit 15, and other operations.

The operation will be explained with reference to FIG. When the microcomputer 16 issues an access command to search a predetermined track, the radial position detection circuit 8 detects the distance to the access target position, and the target speed generation circuit 9 sets a target speed corresponding to that distance. be done. The current speed of the carriage 5 is detected by a relative speed detection circuit 7, and the difference from the target speed is detected by a differential amplifier 10.
is output from. Therefore, the linear motor drive control circuit 11 drives the linear motor 6 so that the carriage 5 reaches the target speed. In this way, the speed of the pickup 3 is controlled so that the speed corresponds to the remaining distance to the target address. When the radial position detection circuit 8 detects that a predetermined number of tracks have been crossed, the microcomputer 16 stops driving the linear motor 6, closes the tracking servo loop, and directs the beam (pickup 3) to the target track. , and perform normal playback operations from there, for example.

On the other hand, during access when the linear motor 6 is being driven, the drive current is detected by the current detection circuit 12, and the coefficient circuit 13 sets a predetermined coefficient x.
After being applied, the signal is input to the focus/tracking drive control circuit 14, and the objective lens 4 constituting the tracking control means is driven.

Now, the drive current of the linear motor 6 is i, the entire mass of the carriage 5 is M, the thrust constant of the linear motor 6 is K, the mass of the objective lens 4 in the tracking control means is m, the braking coefficient is c, the spring constant is k,
Assuming that the magnetic flux density is B and the effective wire length of the coil is l, the transmission block diagram from the drive current i to the speed of the carriage 5 and the speed V of the objective lens 4 as seen from the carriage 5 is shown in FIG. Therefore, the speed V of the objective lens 4 as seen from the carriage 5 is: V=i[xBl/(ms+c+k/s)-Km/M(ms+c+k/s)]...(1). If we find the coefficient x that makes the speed V in equation (1) zero, we get x=Km/MBl...(2). This means the value obtained by dividing the acceleration per drive current of the linear motor 6 by the acceleration per current of the tracking control means. By setting the coefficient x to the value determined by equation (2) in this way,
Drive current i of linear motor 6 at the time of access
regardless of the objective lens 4 on the carriage 5.
was made to remain stationary.

[Problem that the invention seeks to solve]

As described above, the conventional device detects the acceleration α of the carriage 5 from the drive current i of the linear motor 6,
The coefficient x is determined so as to cancel the inertial force applied to the objective lens 4 on the carriage 5 due to this acceleration α, thereby preventing the objective lens 4 from vibrating during access. That is, when the thrust force of the linear motor 6 is F, it is assumed that F=Mα=Ki (3), and the acceleration α was obtained from equation (3). However, equation (3) only holds true when the device is installed horizontally and there is no substantial gravitational component in the moving direction of the carriage 5. In this case, the drive current i of the linear motor 6 and the acceleration α of the carriage 5 are not proportional, and not only is it impossible to move the carriage 5 with the desired acceleration, but also the objective lens 4 vibrates on the carriage 5. This has the disadvantage that stable access operations cannot be performed.

[Means for solving problems]

FIG. 1 is a block diagram of a track access device according to the present invention, and parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present invention, the output of the linear motor drive control circuit 11 (drive current i of the linear motor 6)
The DC component of is detected by the low pass filter 21, and its value is sampled and held by the sample hold circuit 22. This held value is then supplied to coefficient circuits 24 and 25 via a switch 23. The output of the coefficient circuit 24 is added to the output of the coefficient circuit 13 and supplied to the focus/tracking drive control circuit 14, and the output of the coefficient circuit 25 is added to the output of the differential amplifier 10 and supplied to the linear motor drive control circuit 11. It is becoming more and more common. The sample and hold circuit 22 and switch 23 are controlled by a microcomputer 16. The other configurations are the same as in FIG. 5.

[Effect]

The effect will now be explained. As shown in FIG. 2, if the device is inclined by a predetermined angle θ with respect to the horizontal direction and the access operation is performed by moving the carriage 5 to the right, the following equation holds true.

Mα=F+Mgsinθ=Ki+Mgsinθ...(4) Note that g is the gravitational acceleration.

By the way, if the drive current of the linear motor 6 is i' and the acceleration of the carriage 5 is α' when the carriage 5 is installed horizontally, then Mα'=Ki'...(5) ∴α'=Ki'/M ...(6) becomes. Even when the carriage 5 is tilted by an angle θ, the drive current i required to obtain an acceleration α equal to the acceleration α′ when it is horizontal (α=α′) is as follows: i=i′−Mgsinθ/K ...(7) becomes. In other words, even when the carriage 5 is tilted, in order to obtain the desired acceleration when the carriage 5 is horizontal, it is necessary to adjust the drive current when the carriage 5 is horizontal.
It is necessary to compensate i' with a current according to the angle θ.

By the way, in the normal state where the disk is being recorded or played back (the tracking servo loop is closed) before an access operation is performed, the DC component of the tracking error due to disk eccentricity or tilt angle θ (low frequency range), the linear motor 6 compensates for tracking. That is, when the tracking servo loop is closed, the DC current flowing through the linear motor 6 is nothing but the compensation current Mgsinθ/K in equation (7). Therefore, immediately before or after issuing an access command, the microcomputer 16 causes the sample and hold circuit 22 to sample and hold the normal DC current of the linear motor 6, which is detected via the low-pass filter 21, and substantially controls the device. Detect the tilt angle θ. Then, while the tracking server loop is open and the linear motor 6 is being driven for access operation, the switch 23, which had been open until then, is closed, and the sampled and held value (corresponding to the compensation current Mgsinθ/K) is ) is output to the coefficient circuits 24 and 25. The current value corresponding to this compensation current Mgsinθ/K is the coefficient y
is added to the output of the differential amplifier 10 via a coefficient circuit 25 having a
is supplied to the linear motor 6 via. Therefore, even when the carriage 5 is tilted by an angle θ, the carriage 5 can be driven with the desired acceleration when it is horizontal. The coefficient y of the coefficient circuit 25 is determined by applying the output current of the coefficient circuit 25 to the linear motor drive control circuit 11 so that the value of the current applied to the linear motor 6 becomes equal to the output of the sample and hold circuit 22 (for example, If there is no amplification or attenuation during that time, set y=1).

Next, compensation for deflection of the objective lens 4 placed on the carriage 5 during access will be explained. When the carriage 5 is tilted by an angle θ, the neutral position of the objective lens 4 in the normal state when the tracking servo loop is closed is from the horizontal neutral position X ₀ when the device is tilted by the angle θ. As a result, the position is shifted by the displacement Xe caused by the force mgsinθ applied to the objective lens 4. Therefore _, when accessing, the objective lens 4 is at a position (X ₀
+Xe) must be compensated so that it does not move.

If ^the same compensation as in the conventional case is performed, the displacement X of ^the objective lens 4 during access ^is as follows: ) becomes. The first term in equation (8) is the displacement Xe due to the tilt, the second term is the displacement due to the inertial force of the objective lens 4 when the carriage 5 moves, and the third term is the displacement due to compensation by the coefficient circuit 13. From equation (4), acceleration α
When calculating, α=Ki/M+gsinθ...(9), and by substituting equations (2) and (9) into equation (8), we get X=0=X ₀ ...(10). In other words, if the same compensation as the conventional one is performed when the carriage 5 is tilted, the neutral position of the objective lens 4 (X ₀ +
Xe) to the neutral position X ₀ of the objective lens 4 when the carriage 5 is in a horizontal state, which causes the objective lens 4 to vibrate.

Therefore, in the present invention, the output of the sample and hold circuit 22 is applied to the focus/tracking drive control circuit 14 via the coefficient circuit 24, and only the displacement caused by the inertial force when the carriage 5 moves at the acceleration α is compensated. Therefore, even if the carriage 5 moves during access, the objective lens 4 does not vibrate. Therefore, the coefficient of the coefficient circuit 24 has the same magnitude as the coefficient of the coefficient circuit 13, but has the opposite polarity.
It is said that x.

That is ^, when ^the compensation according to the present invention is performed, the displacement X of the objective lens 4 at the ^time of access is as follows: (11) The first term in equation (11) is the displacement Xe due to the inclination,
The second term is the displacement of the objective lens 4 due to inertial force when the carriage 5 moves, and the third term is the displacement due to compensation of the coefficient circuits 13 and 24.

Here, the compensation current i'' is i''=Mgsinθ/K...(12) Therefore, by substituting equations (2), (9), and (12) into equation (11), X=mgsinθ/ (ms ² +cs+k) ...(13) It can be seen that the objective lens 4 is not displaced from the operational neutral position when the device is tilted.

The above-described operation of the present invention is expressed in a transmission block diagram from the drive current i to the speed of the carriage 5 and the speed V of the objective lens 4 as seen from the carriage 5 as shown in FIG. In other words, the speed V of the objective lens 4 seen from the carriage 5 is: V=ixBl/(ms+c+k/s) + [(i+i'')K/Ms-gsinθ/s] ×[ ^-ms2 /( ^ms2 +cs+k)]... ...(14) When substituting equations (2) and (12) into equation (14), equation (14) becomes V=0 ...(15).

The same applies to the case where the carriage 5 moves to the left, so a description thereof will be omitted.

In the above description, the linear motor 6 and the tracking control means are driven by current and the drive current is detected and controlled, but they may be driven by voltage and the drive voltage is detected and controlled. Further, the driving force can be detected not from the drive signal at the drive stage, but from the control signal or the like at a previous stage. Furthermore, the radial position and relative speed of the pickup 3 may be detected by providing a position sensor, a speed sensor, etc., instead of detecting from the reproduced signal. Furthermore, the configuration of the rough adjustment means and fine adjustment means is not limited to linear motors or the like. The present invention can also be applied to non-optical disk recording and reproducing devices.

〔effect〕

As described above, the present invention includes a fine adjustment means for finely adjusting the position of the pick-up with respect to a track formed on the disk, and a coarse adjustment means for coarsely adjusting the position by moving the fine adjustment means in the radial direction of the disk. , a detection means for detecting the driving force of the coarse adjustment means, and a coefficient means for processing the signal from the detection means with a predetermined coefficient, and when driving the coarse adjustment means to access a predetermined track, the coefficient means In a track access device that also drives the fine adjustment means in response to a signal from Since the signal from the driving coefficient means is also compensated, access can be performed with the desired acceleration without being affected by the installation angle of the device (carriage), and vibration of the fine adjustment means during access can be prevented. Therefore, even when the tracking servo loop is closed after the access operation is completed, the lock-in operation can be performed quickly. Furthermore, even during access in which the carriage is moved at high speed, the reproduced signal from the pickup is less likely to be adversely affected, making it possible to accurately detect the position and relative speed of the pickup from the reproduced signal.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the track access device of the present invention, Fig. 2 is a schematic front view of main parts when the installation angle is inclined, Fig. 3 is a transmission block diagram thereof, and Fig. 4 is a conventional one. Block diagram of the device, No. 5
The figure is a transmission block diagram. 1... Disc, 2... Motor, 3... Pickup, 4... Objective lens, 5... Carriage,
6...Linear motor, 7...Relative speed detection circuit,
8...Radial position detection circuit, 9...Target speed generation circuit, 10...Differential amplifier, 11...Linear motor drive control circuit, 12...Current detection circuit, 13, 2
4, 25... Coefficient circuit, 14... Focus, tracking drive control circuit, 15... Spindle drive control circuit, 16... Microcomputer, 2
1...Low pass filter, 22...Sample hold circuit, 23...Switch.

Claims (1)

[Claims] 1. Fine adjustment means for finely adjusting the position of the pick-up relative to a track formed on the disk; coarse adjustment means for coarsely adjusting the position by moving the fine adjustment means in the radial direction of the disk; and the coarse adjustment means. comprising a detection means for detecting the driving force of the detection means, and a coefficient means for processing the signal from the detection means with a predetermined coefficient,
When driving the coarse adjustment means to access the predetermined track, a track access device that also drives the fine adjustment means in response to a signal from the coefficient means detects the inclination angle of the device with respect to the horizontal direction. A track access device characterized in that the driving force of the coarse adjustment means is compensated in accordance with the angle, and the signal from the coefficient means for driving the fine adjustment means is also compensated.