JPH0812746B2 - Information reproducing apparatus having high-speed reproducing function - Google Patents

Description

The present invention relates to an information reproducing apparatus having a high speed reproducing function.

FIG. 1 shows a conventional information reproducing apparatus capable of not only normal reproduction but also high speed reproduction such as double speed or triple speed. In FIG. 1, three spot lights 2 to 4 obtained by converging a laser beam onto a recording track 1 are irradiated in the illustrated positional relationship. That is, when the spot light 2 for detecting information is on the recording track 1, the other two spot lights 3 and 4 are located on both side edges of the recording track 1. Therefore, when the spot light 2 is deviated in the direction orthogonal to the track (radial direction of the recording disk), the light amount difference between the reflected lights of the two spot lights 3 and 4 corresponds to the deviation direction and its magnitude. Each of the reflected lights of these spot lights 2 to 4 is converted into an electric signal by the photoelectric conversion elements 5 to 7, respectively. The respective outputs of the photoelectric conversion elements 6 and 7 are supplied to the differential sump 8. From the differential amplifier 8 to the photoelectric conversion element 6
A signal corresponding to the level difference between the outputs of 7 and 7 is output, that is, a signal corresponding to the light amount difference of the reflected light of the spot lights 3 and 4. The output of the differential amplifier 8 is supplied as a tracking error signal to the drive circuit 10 after passing through the phase compensation circuit 9. The output of the drive circuit 10 is the tracking actuator 11
Is supplied to one of the input terminals. A resistor R ₁ for current detection is connected between the other input terminal of the tracking actuator 11 and the ground. A voltage corresponding to the drive current supplied to the tracking actuator 11 is generated across the resistor R ₁ and is supplied to the drive circuit 10. Drive circuit 10
Is configured to supply the drive current corresponding to the tracking error signal to the tracking actuator 11 by the voltage generated across the resistor R ₁ . The tracking actuator 11 is, for example, an objective lens (not shown)
Formed by a movable portion on which the movable portion is mounted, a support portion that supports the movable portion with a spring or the like, and a means that displaces the movable portion in the radial direction with respect to the recording track 1 in accordance with the supplied drive current. ing. This tracking actuator
A driving current corresponding to the tracking error signal is supplied to the driving circuit 11 so that the spot light 2 for information detection is controlled so as to accurately track the recording track.

The above-mentioned portion forms a tracking servo loop as a fine adjustment means for highly accurately controlling the relative position of the information detection point in the radial direction with respect to the recording track.

On the other hand, the output of the photoelectric conversion element 5 is supplied to the demodulation circuit (not shown) as an RF signal read from the recording disk and is also supplied to the speed detection circuit 12. Speed detection circuit
For example, 12 is a structure for extracting the envelope component of the RF signal, detecting the relative moving speed in the radial direction with respect to the recording track of the information detection point by the frequency of this envelope component, and outputting a voltage according to the moving speed. Has become. The output voltage of this speed detection circuit 12 is
Supplied to 13. The differential amplifier 13 outputs a signal corresponding to the difference between the output voltage of the speed detection circuit 12 and the reference voltage Vr.
The output signal of the differential amplifier 13 is supplied to one input terminal of a changeover switch circuit 15 via a compensation circuit 14. The voltage generated across the resistor R ₁ is supplied to the other input terminal of the changeover switch circuit 15 via the phase compensation circuit 16. A control signal output from a high speed reproduction operation control circuit (not shown) is supplied to the control input terminal of the changeover switch circuit 15. The changeover switch circuit 15 is configured to selectively output either one of the output of the compensation circuit 14 and the output of the phase compensation circuit 16 according to the control signal. The output of the changeover switch circuit 15 is supplied to the drive circuit 17. The output of the drive circuit 17 is supplied to one input terminal of a carriage motor 18 that drives the carriage carrying the tracking actuator 11 in the radial direction with respect to the recording track 1. A resistor R ₂ for current detection is connected between the other input terminal of the carriage motor 18 and the ground. This resistance R ₂
A voltage corresponding to the drive current supplied to the carriage motor 18 is generated between both ends of the drive voltage and is supplied to the drive circuit 17. Like the drive circuit 10, the drive circuit 17 is configured to supply the drive current corresponding to the output of the changeover switch circuit 15 to the carriage motor 18 by the voltage generated across the resistor R ₂ .

With the above configuration, the tracking actuator 11
Since the movable range of the movable part is about ± 0.5 mm, the control range of the relative position of the information detection point is narrowed by the tracking servo loop alone, and the information detection point is wide over the entire radius of the recording disk. Cannot follow the recording track. For this reason, the carriage on which the tracking actuator 11 is mounted is moved in the radial direction with respect to the recording track, and the relative position of the information detection point is set so that the information detection point is located substantially in the center of the control range of the tracking servo loop. A carriage servo loop is formed as a rough adjusting means for controlling the control with a relatively low accuracy. That is, during normal reproduction, the output of the phase compensation circuit 16 is selectively output from the changeover switch circuit 15.
Then, the carriage is driven so that the drive current supplied to the tracking actuator 11 becomes zero, and the relative position of the information detection point is controlled.

Next, during high speed reproduction, the output of the compensating circuit 14 is selectively output from the changeover switch circuit 15 to form the radial servo loop for controlling the interlacing operation in which the information detection point jumps from one recording track to another recording track. To be done. As a result, the carriage is driven so that the output voltage of the speed detection circuit 12 becomes equal to the reference voltage Vr, and the relative moving speed of the information detection point in the track radial direction becomes equal to the speed corresponding to the reference voltage Vr. Controlled by.

A second block diagram of the conventional information reproducing apparatus as described above is shown.
Shown in the figure. In FIG. 2, the difference between the target value, that is, the displacement of the recording track in the radial direction with respect to the information detection point and the difference of the displacement of the objective lens in the radial direction with respect to the recording track is optically detected and the voltage is applied by the element 19 including the differential amplifier 8. Is converted into a tracking error signal. This tracking error signal is applied to the phase compensation circuit 9
Is supplied to the element 22 composed of the drive circuit 10 through the element 20 composed of the element and the switch circuit 21 which is turned off at the time of high speed reproduction.
Element 22 converts the tracking error signal into a drive current. This drive current is converted into a displacement in the radial direction of the objective lens with respect to the recording track by the element 23 including the tracking actuator 11. At the same time, this drive current is converted into a voltage by element 24 consisting of resistor R ₁ . Then, during normal reproduction, this voltage is transmitted through the element 25 composed of the compensation circuit 16 and the changeover switch circuit 15 to the element 26 composed of the drive circuit 17 and the carriage motor 18.
And is converted into a displacement of the carriage in the radial direction with respect to the recording track. That is, element 26 has a transfer characteristic that indicates the displacement of the carriage with respect to the drive voltage to the carriage motor. The displacement of the carriage is converted into a displacement of the objective lens in the radial direction with respect to the recording track by an element 27 including a movable portion of the tracking actuator 11 and a supporting means. That is, the displacement caused by the element 26 causes the objective lens to have factors other than the drive voltage, that is, factors including viscosity between the carriage and the objective lens and inertia of the objective lens when the objective lens is moved by the carriage. However, the objective lens is displaced. A tracking actuator 11 such as in element 23 showing the displacement due to this displacement of the carriage and the displacement with respect to the drive current supplied.
The displacement due to is added to give the displacement of the objective lens. In the element 23, the actuator independently displaces regardless of the carriage motor, so that the element 23 has a parallel relationship with the element 27.

Next, during high-speed reproduction, the relative moving speed of the objective lens in the radial direction with respect to the recording track is optically detected and converted into a frequency by the element 28 including means for extracting the envelope component of the RF signal in the speed detection circuit 12. It This frequency is converted into a voltage in the speed detection circuit 12 by means of an element 29 comprising means for converting the frequency into a voltage. The difference voltage between the voltage output from the element 29 and the reference voltage Vr is composed of the compensation circuit 14 and the element 30 and the changeover switch circuit.
It is supplied to the element 26 via 15 to control the moving speed of the objective lens in the radial direction of the recording track.

In the block diagram as described above, the element 27 including the movable part, the supporting means, etc. in the tracking actuator 11
The transfer function G ₁ (s) of is as follows.

G ₁ (s) = (cs + k) / (ms ² + cs + k) (1) where m is the mass of the movable part of the tracking actuator 11, c is the viscosity of the support part of the tracking actuator 11, and k is the tracking actuator 11 Is the elasticity of the support portion.

Further, the transfer function G ₂ (s) of the element 26 is as follows.

G ₂ (s) = 1 / Js ² (2) Here, J is the moment of inertia of the rotor of the carriage motor 18.

Further, the element 29, that is, the means for converting the frequency into the voltage in the speed detection circuit 12 usually includes a low-pass filter for waveform shaping. The transfer function G ₃ (s) of this low-pass filter is expressed by the following equation.

_{G 3 (s) = 1 /} (1 + sT 1) ...... (3) Here, T ₁ is a time constant. Further, in the equation (3), the transfer function of the primary low-pass filter is shown.

From equation (1), element 27 is the resonance frequency. It can be seen that the frequency characteristics are such that the phase rotation becomes −90 ° or more. Further, it can be seen from the equation (2) that the element 26 has a frequency characteristic such that the phase rotation is constant at -180 °. Further, the transfer function of the equation (3) has a phase rotation of − at a frequency sufficiently higher than the cutoff frequency.
It shows that there is a frequency characteristic of 90 °.

Therefore, the phase characteristic of the open loop frequency response of the radial servo loop formed by the elements 26, 27, 28, 29 and 30 during high speed reproduction is as shown by the solid line a in FIG. phase frequency becomes -180 ° lower than the resonance frequency f _o. Therefore, considering the stability of the radial servo loop, it is necessary to set the gain crossing point, that is, the frequency at which the gain of the open loop frequency response becomes OdB, to be lower than the phase crossing point. The bandwidth could not be widened as shown by the solid line b. Therefore, the conventional information reproducing apparatus has a drawback that the transient response of the radial servo that moves the information detection point in the radial direction with respect to the recording track during high-speed reproduction has a long rise time and a slow response. At this time, the phase characteristic and the gain characteristic of the closed loop frequency response of the radial servo loop are respectively the fourth characteristic.
As shown by solid lines c and d.

Therefore, it is an object of the present invention to widen the bandwidth of the radial servo loop that is formed during high-speed reproduction and moves the information detection point in the radial direction with respect to the recording track, and enables the jumping operation with good responsiveness. It is to provide a reproducing device.

An information reproducing apparatus having a high speed reproducing function according to the present invention,
A recorded information reproducing apparatus for a disk which performs high speed reproduction by an interlacing operation in which an information detecting point formed by a pickup jumps from one recording track to another recording track on the disk, and the information detecting point and the recording are recorded. Tracking error generating means for generating a tracking error signal indicating an error in the relative position of the disk in the radial direction of the disk, and a drive signal according to the supplied control signal are supplied so that the information detection point is within a predetermined drive range. A tracking actuator for driving the disk in the radial direction, a coarse adjustment means for controlling the drive of the pickup in the radial direction of the disk according to the drive signal, and a moving speed of the information detection point in the radial direction of the disk. A moving speed detector that detects and generates a speed signal according to the moving speed. Means for supplying the tracking error signal to the tracking actuator as the control signal during normal reproduction, and the tracking actuator as the control signal using a difference signal corresponding to the level difference between the speed signal and a reference signal during the high speed reproduction. And a signal supply means for supplying to the.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

As shown in FIG. 5, in the information reproducing apparatus according to the present invention, the output of the phase compensating circuit 16 is directly supplied to the drive circuit 17 and the output of the differential amplifier 8 is supplied to the output of the phase compensating circuit 9 and the complete integration. The output of the mold compensation circuit 31 is a changeover switch circuit
It has the same construction as the device of FIG. 1 except that it is supplied alternatively to the drive circuit 10 by 15. The perfect integration type compensation circuit 31 is configured so that the transfer function is as shown in the following equation.

_{G 4 (s) = (1} + sT 2) / s ...... (4) Here, T ₂ is a time constant.

In the above structure, the output of the phase compensation circuit 9 is selectively supplied to the drive circuit 10 during the normal reproduction, and the relative position of the information detection point in the radial direction with respect to the recording track is similar to the device of FIG. Control is made.

Next, during high speed reproduction, the output of the compensation circuit 31 is selectively output from the changeover switch circuit 15 to form a radial servo loop. Then, the tracking actuator is adjusted so that the output voltage of the speed detection circuit 12 becomes equal to the reference voltage Vr.
11 is driven and the carriage carrying this tracking actuator 11 is ejected. As a result, the relative moving speed of the information detection point in the radial direction with respect to the recording track is controlled to be equal to the speed corresponding to the reference voltage Vr.

A block diagram of the information reproducing apparatus according to the present invention as described above is shown in FIG. In FIG. 6, the output of the element 21 composed of the phase compensation circuit 9 and the element composed of the complete integration type compensation circuit 31.
The output of 32 is selectively supplied to the element 22 of the drive circuit 10 by the changeover switch circuit 15 and the output of the element 25 of the phase compensation circuit 16 is supplied to the drive circuit 17 and the carriage motor 18.
Element except that it is supplied directly to element 26 consisting of
20 to 29 are connected in the same manner as in FIG. The element 32 is supplied with the difference voltage between the voltage output from the element 29 and the reference voltage Vr.

In the block diagram above, the transfer function of element 23
G ₅ (s) is approximated by the following equation.

G ₅ (s) = 1 / (ms ² + cs + k) (5) The transfer function is the resonance frequency. It becomes the characteristic of the secondary type which has. The loop (elements 24, 25, 26, 27) of the carriage motor part has gain and compensation characteristics set by the compensation circuit characteristic 25 so that it will respond to frequencies that do not reach the resonance frequency of the tracking actuator during steady feed. There is. Therefore, as a whole, the phase rotation around f0 decreases.

Therefore, in the loop formed by the elements 22, 23, 28, 29, and 32 during high-speed reproduction, the influence of the element 27 having a large phase rotation can be reduced by the above-described configuration in the vicinity of the resonance frequency f _o, so that the open loop frequency of the radial servo loop can be reduced. The phase characteristic of the response is as shown by the solid line e in FIG. 7, and the phase intersection can be increased.

Here, the element 32, that is, the time constant T ₂ in the transfer function of the perfect integral compensation circuit 31 is set as shown in the following equation.

T ₂ ≈1 / 2πf ₀ (6) Further, the time constant T ₁ in the transfer function G ₃ (s) is set so that T ₁ <T ₂ .

Then, as is apparent from the equations (3), (4), and (6), the time constant T ₂ is associated with the open loop transfer function of the radial servo loop including the elements 29 and 32 formed at the high speed reproduction. frequency or the resonance frequency f _o frequency higher than the corresponding frequency or f _o to the zero point (turnover frequency) and and time constant T ₁ is a pole (roll-off frequency). Therefore, only the gain of the insert by the gain crossover open loop reduces the gain constant is increased below the resonance frequency f _o of the transfer function of the radial servo loop so as not to change in Element 32 increases. Therefore, the gain of the low frequency band can be increased by the element element 32, that is, the complete integration type compensation circuit 31.

Further, since the phase intersection can be increased, the gain intersection can be increased without destabilizing the radial servo, and the gain characteristic of the open loop frequency response of the radial servo loop is as shown by the solid line f in FIG. Resonance frequency
The phase margin can be generated at a frequency higher than f _o . At this time, the phase characteristics and gain characteristics of the closed loop frequency response are as shown by solid lines g and h in FIG.

In the above embodiment, the moving speed of the information detection point during high-speed reproduction is controlled to be the speed corresponding to the reference voltage Vr. However, this reference voltage Vr is, for example, relative to the target track in the jumping operation of the information detection point. You may make it change according to a relative position. Further, in the above embodiment, the voltage and the reference voltage according to the moving speed of the information detection point
The voltage difference from Vr is the driving circuit via the perfect integration type compensation circuit 31.
Although the difference voltage is supplied to the driving circuit 10, the difference voltage may be directly supplied to the driving circuit 10 without passing through the perfect integration type compensation circuit 31.

As described above, according to the present invention, a phase margin occurs at a frequency higher than the resonance frequency f _o in the radial servo loop formed during high-speed reproduction. Therefore, the upper limit of the radial servo band should be set higher than the resonance frequency f _o. Can
The transient response characteristic can be improved. Therefore, it is possible to further increase the moving speed of the information detection point during high-speed reproduction. Further, if the complete integration type compensation is performed, the gain in the low frequency band is increased, and more stable servo can be applied. Therefore, even if the tracking actuator 11 having a low resonance frequency is used, it is possible to eliminate the lack of low-frequency gain and the disturbance of the radial servo due to the transient response of the lens.

INDUSTRIAL APPLICABILITY The present invention is suitable for an information reproducing apparatus that employs a system in which a carriage motor is directly driven by a linear motor or a rotary motor that can be approximated by a transfer function as a carriage motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conventional information reproducing apparatus, and FIG.
1 is a block diagram of the apparatus shown in FIG. 1, FIGS. 3 and 4 are graphs showing characteristics of a radial servo formed in the apparatus shown in FIG. 1, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a block diagram showing the device of FIG.
FIGS. 7 and 8 are graphs showing the characteristics of the radial servo formed in the apparatus of FIG. Explanation of main part code 12 …… Speed detection circuit 13 …… Differential amplifier 15 …… Changeover switch circuit 31 …… Complete integration type compensation circuit

Claims (3)

[Claims] 1. A recorded information reproducing apparatus for a disk which performs high-speed reproduction by an interlacing operation in which an information detection point formed by a pickup jumps from one recording track to another recording track on the disk. Tracking error generating means for generating a tracking error signal indicating an error in relative position between the point and the recording track in the radial direction of the disk,
A tracking actuator which is supplied with a drive signal corresponding to the supplied control signal and drives the information detection point in the radial direction of the disc within a predetermined drive range; and a pickup which moves the pickup in the radial direction of the disc in response to the drive signal. Coarse adjusting means for driving and controlling, moving speed detecting means for detecting a moving speed of the information detection point in the radial direction of the disk and generating a speed signal according to the moving speed, and the tracking error signal during normal reproduction. To the tracking actuator as the control signal, and a signal supply means for supplying the tracking actuator as the control signal with a difference signal corresponding to the level difference between the speed signal and the reference signal during the high-speed reproduction. An information reproducing apparatus having a characteristic high-speed reproducing function. 2. The signal supply means is [(1 + sτ) / s].
A transfer function (s is a complex variable, τ is a time constant), and the tracking actuator via the perfect integration circuit for the difference signal during the high-speed reproduction. The information reproducing apparatus having a high-speed reproducing function according to claim 1, characterized in that the information reproducing apparatus is supplied to the information reproducing apparatus. 3. The high-speed reproduction function according to claim 1, wherein the level of the reference signal changes according to the distance from the information detection point to a target recording track in the high-speed reproduction. An information reproducing apparatus having.