JPH0748258B2 - Optical disk drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disk drive device, and more particularly to an optical disk drive device that performs access control for allowing an optical spot to access an arbitrary track on an optical disk.

[Prior Art] FIG. 7 shows a Japanese Patent Application No. 60- by the same applicant filed on May 15, 1985, entitled "Optical disk drive".
FIG. 11 is a block diagram showing a configuration of a conventional optical disc drive device described in 101439 specification. In the figure, the optical disk 10
1 has a large number of recording tracks of high-density pits in a large number of concentric circles or spirals. The disk motor 102 adheres the optical disk 101 to a spindle and rotates it.

On the other hand, the optical head 104 forms a light spot on the optical disc 101 and moves it in the radial direction, and includes a frame 105, a light source 106 such as a semiconductor laser, a collimator lens 107, a polarization beam splitter 108, and a λ / 4 plate. 109, optical path changing mirror 110,
The objective lens 111 that focuses the light beam from the light source 106 on the medium surface of the optical disc 101 to form a light spot 115, and the objective lens 111 to accurately position the light spot 115 on the recording track of the optical disc 101. Of the return light reflected by the tracking actuator 112 and the optical disc 101, which are slightly moved in the radial direction of 2
It is composed of a split photodetector 113 for splitting.

The adder / subtractor amplifier circuit 114 outputs the sum signal as an information signal by taking the sum of the outputs of the split photodetector 113, and the split detector 11
The output of 3 is subtracted to output the tracking error signal to the track crossing number counter 118 and the speed detection circuit 120.

The track crossing number counter 118 includes an addition / subtraction amplifier circuit 114.
Is input to detect the number of tracks traversed by the optical head 104, and the output is sent to the target speed generation circuit 119.

This target speed generation circuit 119 is provided with a track crossing number counter 1
18 outputs are input and the target speed signal of the light spot 115 is generated at the time of access to drive the head actuator drive control circuit.
I am trying to output to 117.

The output of the polarity switching circuit 2 is also input to the head actuator drive control circuit 117,
Based on these outputs, the head actuator drive control circuit 117 drives and controls the head actuator 116.

The head actuator 116 is driven by the head actuator drive control circuit 117, and moves the optical head 104 in the radial direction of the optical disc 101.

The speed detection circuit 120 detects the speed at which the light spot 115 crosses the track on the optical disc 101, and the output thereof is output to the polarity switching circuit 2. The speed detection circuit 120 and the polarity switching circuit 2 constitute a speed detection circuit 124.

The polarity switching circuit 2 includes an access direction command generating circuit 12
The output of 3 is input, and the polarity switching circuit 2 is output by the output of the access direction command generating circuit 123.
Switches the polarity of the output of the speed detection circuit 120. That is, the detected speed (scalar amount) having a direction is switched so as to become the detected speed (vector amount).

Further, FIG. 8 is a transfer function block diagram of the speed control system in which FIG. 7 is expressed by a transfer function. In the figure, the subtraction result of the output Vr of the target speed generation circuit 119 and the detected speed Vs * from the speed detection circuit 120 is input to the gain compensation circuit 5. The gain compensating circuit 5 determines the band of the speed control system.

The gain compensation circuit 5, the notch filter 122, and the head actuator drive circuit 6 are included in the head actuator drive control circuit 117. The notch filter 122 is a mechanical resonance characteristic G of the head actuator shown by block 8 in the head actuator 116. _It compensates _L (s).

Further, since the head actuator drive circuit 6 normally adopts a current drive system, it also incorporates a drive current detection circuit.

The head actuator 116 is composed of a block 7 and a block 8. The block 7 is a block that receives the force constant of the head actuator and the block 8 receives the acceleration as an input and shows the transfer characteristic of the head actuator 116.
Is the mass of the movable part, G _L (s) is the mechanical resonance characteristic of the head actuator 116, and S is the Laplace operator. Description of other configurations is omitted because it is the same as that of FIG. 7, but K _V of the target speed generation circuit 119 and the speed detection circuit 124 is the speed detection sensitivity,
Further, τ means the track crossing period of the light spot 115.

FIG. 9 shows an example of the gain characteristic of G _L (s) in the block 8 of FIG. 8, which shows the frequency ω _L (usually KH _Z )
Has a large resonance peak at.

On the other hand, FIG. 10 shows the gain characteristic | G _N (s) | of the notch filter 122 of FIG. 8, where ω _N = ω _L, and | G _N (s) || 1 / G G _N (s) so that _L (s) |
To design.

Figures 11 and 12 show the open-loop characteristics of Figure 8.
Figure 11 shows G _N (s) = 1 / _GL (s), and Figure 12 shows G
_This means a case where _N (s) ≠ 1 / _GL (s).

The conventional optical disk drive device is configured as described above. In FIG. 7, first, the disk motor drive control circuit 103
Based on the tracking error signal detected by the photodetector 113 and the addition / subtraction amplification circuit 114 by the well-known operation of the optical head 104 after the disk motor 102, that is, the optical disk 101, starts to rotate and reaches the steady rotation speed by By controlling the tracking actuator 112,
The light spot 115 follows the center of a track on the optical disc 101.

Further, at the time of track access, the number of tracks of the optical disk 101 which the optical spot 115 has traversed is counted by the track traversing counter 118, and at the same time, the target speed generation circuit 119 outputs it according to the number of remaining tracks up to the target track. The head actuator drive control circuit 117, which has input the target speed and the track crossing speed of the light spot 115 by the speed detection circuit 124, controls the speed so that the speed approaches zero as the light spot 115 approaches the target track.

Further, referring to FIG. 8, the operation of the speed control system during track access will be described in detail. The speed deviation signal Ve, which is the difference between the target speed signal Vr output from the target speed generation circuit 119 and the detected speed signal Vs * output from the speed detector 124.
Is transmitted to the head actuator drive circuit 6 via the gain compensation circuit 5 and the notch filter 122, and a drive current is applied to the head actuator 116. As a result, the head actuator 116 starts moving at the speed V _L , and the light spot 115 crosses the track on the optical disc 101.

On the other hand, assuming that the track shake velocity generated by the rotation of the optical disc 101 is Vd, the head actuator 11
The difference between the speed of 6 and the track runout speed Vd is the speed detection circuit 120.
Detected as the detected speed signal Vs *, and this detected speed signal
By feeding back Vs *, the entire speed control system operates so that the detected speed signal Vs * matches the target speed signal Vr.

The loop transfer function (open loop characteristic) from the speed deviation signal Ve to the detected speed signal Vs * is G ₀₁ (s) = Vs * (s) / Ve (s) = K _C K _A K _F K _{V / MS · G N (s} ) G L (s) · (1-e -sτ) / Sτ ......
(1)

When G _N (s) = 1 / G _L (s) can be designed, as shown in FIG. 11, the mechanical resonance characteristics of the head actuator 116 in the high range do not appear, but due to variations between devices, etc.
When G _N (s) ≠ 1 / G _L (s), as shown in FIG. 12, the mechanical resonance characteristic of the head actuator 116 appears in the high frequency range, and the peak of the mechanical resonance characteristic exceeds O _dB. If there,
The speed control system becomes unstable.

Also, due to the dead time of the zero-order hold characteristic of the speed detection circuit 124, the phase is greatly delayed near the track crossing frequency.

[Problems to be Solved by the Invention] The conventional optical disk drive apparatus as described above has the following problems.

(1) Since the speed at which the light spot 115 crosses the track is detected based on the track crossing cycle, if the track is slowly crossed at low speed, a time delay (dead time) occurs in speed detection, and Since the control system tends to be unstable, the cutoff frequency of the speed control system must be designed low, and speed deviation tends to increase.

(2) When the light spot 115 passes through the dropout portion or the data address recording portion of the optical disc 101 and the dropout or data address recording period is erroneously detected as the track crossing period, the light spot 115 is actually moving at a low speed. However, since the speed detection circuit 124 malfunctions as if the speed is high, the speed control system is disturbed.

(3) The head actuator 116 usually has a large mechanical resonance in the vicinity of several KHz, and the notch filter 122 is inserted in the head actuator drive control circuit 117 to remove this, but if there are a plurality of resonance frequencies. ， The circuit scale becomes large, and the resonance frequency varies from device to device.
If the frequency of the notch filter 122 shifts, the speed control system becomes unstable.

(4) Since the light spot 115 does not have a function of detecting the direction in which the light beam crosses the track, and the speed polarity is simply switched depending on the direction (inner circumferential direction or outer circumferential direction) to be originally accessed, the track speed is low at low speed. If the transverse direction reverses to the direction to be accessed due to shake or disturbance speed, positive feedback is applied to the speed control system, and the optical head 104 may run away.

The present invention has been made to solve the above problems, and compensates the dead time of the speed detection circuit, improves the stability of the speed control system, widens the band of the system, and reduces the speed deviation, Disturbance of the speed control system can be reduced even if the speed detection circuit malfunctions in the dropout or address data section on the optical disk, the notch filter is removed to simplify the circuit, and mechanical resonance at any frequency is achieved. It is an object of the present invention to provide an optical disk drive device that can suppress the influence of the above, and can prevent the optical head from running away even if the track crossing direction of the light spot is reversed due to the disturbance speed.

[Means for Solving Problems] An optical disk drive apparatus according to the present invention includes at least an objective lens that forms a light spot on an optical disk having a large number of tracks, and a photodetector that receives reflected light from the optical disk. Optical head, a head actuator for moving at least a part of the optical head in the radial direction of the optical disk when performing track access to the track of the optical disk, and a track crossing of a light spot moving in the radial direction of the optical disk. Speed detecting means for detecting a speed signal from the light receiving output of the photodetector; acceleration detecting means for detecting an acceleration signal of the optical head from a drive signal of the head actuator; track crossing speed signal from the speed detecting means; The acceleration signal from the acceleration detection means is input If the frequency corresponding to the moving speed of the optical head is lower than a predetermined reference frequency, a track crossing estimated speed signal matching the track crossing speed signal output from the speed detecting means is generated, and the movement of the optical head is performed. When the frequency corresponding to the speed is higher than the reference frequency, state observing means for generating an estimated track crossing speed signal that matches the integrated signal of the acceleration signal from the acceleration detecting means, and the track crossing number of the optical head. Target speed generating means for calculating a track crossing target speed signal from the head actuator, and a head actuator for controlling the head actuator based on the track crossing target speed signal from the target speed generating means and the track crossing estimated speed signal from the state observing means. And a drive control means.

[Operation] In the present invention, at the time of track access, the state observing unit detects the light spot by the signal obtained by switching the polarity of the output of the speed detection circuit depending on the track crossing direction of the light spot and the output signal of the drive current detection circuit of the head actuator. The track crossing speed is estimated and the track crossing speed of the light spot is controlled.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of an optical disk drive according to the present invention. In the figure, the same parts as those in FIG. 7 are designated by the same reference numerals to avoid redundant description, and the parts different from those in FIG. 7 will be mainly described. Reference numerals 101 to 120 are the same as those of the conventional device.

The direction detection circuit 1 has an addition / subtraction amplifier circuit 11 on its input side.
The difference signal and sum signal output of 4 are input, and the light spot 115
Detects the direction crossing the track of the optical disc 101. The polarity switching circuit 2 switches the polarity of the output of the speed detection circuit 120 according to the output of the direction detection circuit 1. The speed detection circuit 20 is composed of a direction detection circuit 1, a speed detection circuit 120, and a polarity switching circuit 2.

The state observer 3 receives the drive current signal detected by the drive current detection circuit 121 that detects the drive current of the head actuator 116 and the speed detection signal having the polarity output from the polarity switching circuit 2 as input, It estimates the speed close to the value of. The output of the state observer 3 is sent to the head actuator drive control circuit 117.

Further, the control mode detection circuit 4 outputs a command to reset the integrator in the state observer 3 while the light spot 115 is following the track center.

FIG. 2 is a transfer function block diagram of the speed control system expressing FIG. 1 by a transfer function. In the figure, the state observer 3, the control mode detecting circuit 4, and the speed detecting circuit 20 are the same as those in FIG. 1, and the gain compensating circuit 5 and the force constant 7 of the head actuator are shown.
And block 8 is the same as in FIG.

The state observer 3 is composed of gain elements 9, 10, 13 and a feed gain element 11 and an integrator 12.

The gain element 9 is the force constant 7 of the head actuator 116.
Is a gain element that has a gain K _F equal to, and receives a drive current signal detected in the head actuator drive circuit 6 as an input, and outputs an estimated value of the drive force as a gain element 10, a head actuator 116, an optical head 104, and the like. Is a gain element having a gain 1 / M equal to the reciprocal of the moving part mass at the time of access, and the feedback gain element 11 is a detection speed signal Vs detected by the speed detection circuit 20.
It is a feedback gain element that receives the difference between * and the estimated speed signal s that is the output of the gain element 13.

The integrator 12 is an integrator that receives an accurate estimated value of the acceleration signal obtained by adding the output of the feedback gain 11 to the acceleration output from the gain element 10, and outputs the output of the control mode detection circuit 4. It can be reset by.

The gain element 13 is a gain element simulating the speed detection circuit 20 and outputs the estimated speed signal s.

FIG. 3 is a diagram showing waveforms at various parts during speed control. In the figure, reference numeral 14 is the addition / subtraction amplifier circuit 114 in FIG.
Is a track crossing sensor signal, reference numeral 15 is an output signal (detection speed signal) Vs * of the speed detection circuit 20, reference numeral 16 is an estimated speed signal s output from the state observer 3, and reference numeral 17 is feedback in FIG. Estimated velocity signal s output from the state observer 3 when the gain L of the gain element 11 is 0
Is.

FIG. 4 is a diagram showing the relationship between the track groove and the detection signal. FIG. 4 (a) is a cross-sectional view of the optical disc, designated by reference numeral 18
Is a track groove portion, and reference numeral 19 is an inter-groove portion. Fig. 4 (b)
Is a subtraction output signal (tracking error signal) of the addition / subtraction amplifier circuit 114 of FIG. 1, FIG. 4 (c) is also an addition output signal (sum signal), and FIGS. 4 (d) and 4 (e) are respectively It is the comparison signal of FIG. 4 (b) and FIG. 4 (c).

FIG. 5 is a diagram showing open-loop transfer characteristics of the respective control systems shown in FIG. 2 and showing frequency characteristics of gain and phase.

In the optical disk drive configured as described above,
The light from the light source 106 is collimated by the collimator lens 107, is linearly polarized through the polarization beam splitter 108, passes through the λ / 4 plate, is reflected by the mirror 110, and is steadily rotated by the objective lens 111. A light spot 115 is formed on the existing optical disc 101.

The light reflected from the optical disc 101 returns from the objective lens 111 to the polarization beam splitter 108, is reflected by the polarization beam splitter 108, and enters the split photodetector 113.

The light incident on the split photodetector 113 is photoelectrically converted by the split photodetector 113, and this photoelectrically converted signal is added / subtracted by an amplification circuit 114.
To be a sum signal and a tracking error signal.

At the time of track access, the sum signal and the tracking error signal are the track crossing number counter 118 and the speed detection circuit 120.
And the direction detection circuit 1.

Based on the detection result of the direction detection circuit 1, the detected speed signal output from the speed detection circuit 120 is used in the polarity switching circuit 2 depending on whether the light spot 115 is moving in the outer peripheral direction or the inner peripheral direction of the optical disc 101. After switching the polarity, the detected speed is input to the state observer 3. At the same time, the drive current signal of the head actuator 116 detected by the drive current detection circuit 121 is also input to the state observer 3.

At the same time, the drive current signal of the head actuator 116 detected by the drive current detection circuit 121 is also input to the state observer 3.

Further, at this time, the reset of the integrator 12 inside the state observing device 3 is released by the output of the control motor detecting circuit 4 so that the state observing device 3 operates.

On the other hand, the output of the track crossing number counter 118 is transmitted to the target speed generation circuit 119, and the target speed according to the number of remaining tracks is output from the target speed generation circuit 119.

The head actuator drive control circuit 117 drives and controls the head actuator 116 based on the output of the target speed generation circuit 119, the output of the state observer 3 and the output of the drive current detection circuit 121, so that the light spot 115 Controls track crossing speed.

2 and 3, the operation of the state observer 3 will be mainly described. The output of the gain compensation circuit 5 that determines the band of the speed control system is a drive command signal for the head actuator 116, which is converted into a drive current by the head actuator drive circuit 6, and the head actuator 116 outputs a force constant K _F.
It becomes the driving force by [N / A], and is multiplied by 1 / M which is the reciprocal of mass to become the acceleration, and the acceleration is integrated.
Further, the high-range resonance characteristic G of the head actuator 116
Also affected by _L (s), head actuator 1 at speed V _L
16 moves.

Further, if the track deflection speed due to eccentricity of the optical disc 101 is Vd, the difference between V _L and V d becomes the track crossing speed of the light spot 115, which is detected by the speed detection circuit 20 and the speed detection sensitivity K Converted to an electric signal with a gain of _V [V / m / s].

At this time, as shown in FIG. 3, the detected speed signal 15 detected from the track crossing cycle of the track crossing sensor signal 14 which is the output of the addition / subtraction amplifier circuit 114 is the average of the immediately preceding half tracks only after the track crossing is detected. Since it is obtained as the traverse speed, it has a staircase waveform like the detected speed signal 15 during deceleration, and has a zero-order hold characteristic as shown in the speed detection circuit 120. Moreover, since the track crossing period becomes longer as the speed becomes lower, τ has a small value at the high speed and a large value at the low speed.

The state observer 3 basically has a head actuator 116.
The transfer characteristic of the speed detection circuit 20 and the transfer characteristic of the speed detection circuit 20 are simulated by an electronic circuit.
_L (s) and zero-order hold characteristic of the speed detection circuit 20 (1
^-E-sτ ) / Sτ is not included.

In the state observer 3, first, the drive current signal i _L of the head actuator 116 detected by the drive current detection circuit 6 is used as acceleration information by the gain elements 9 and 10.

Further, the difference between the estimated speed signal s multiplied by the gain K _V in the gain element 13 and the output signal (detection speed signal) Vs * of the speed detection circuit 20 is calculated, and the feedback gain element 11 multiplies by L / K _V and integrated. By adding to the input acceleration information to the device 12,
The addition speed information is modified so that the estimated speed signal s converges to the detected speed signal Vs *.

By the way, the drive current signal i _L of the head actuator 116, which is the two inputs of the state observer 3, and the detected speed signal Vs
The transfer characteristic from * to the estimated speed s which is the output of the state observer 3 is s = 1 / (S + L) ・ K _F K _V / M ・ i _L + L / (S + L) ・ Vs *… …
(2)

That is, the transfer characteristics from the drive current signal i _L to the estimated speed signal s and the detected speed signal Vs * to the estimated speed signal s both have a first-order lag, and the time constant is 1 / L or L> 0 Observer 3 is stable. That is, L is a parameter that determines the speed of convergence of the estimated speed signal s, for example, 1
If it is converged with a time constant of ms, select L = 1000.

Below, the meaning of Eq. (2) is considered by separating the bands. First, since K _F i _L / M corresponds to the acceleration of the head actuator 116, if the track runout speed Vd of the optical disk is sufficiently smaller than the speed V _L of the head actuator 116, in order, | Vs * || 1 / S ・ K _F K _V / M ・ i _L | …… (3) If S = jω, (i) when ω << L (| S | << L) s1 / L ・ K _F K _V / M ・ i _L + Vs * …… (4) If L1000, then (3) From the formula | Vs * || 1 / S ・ K _F K _V / M ・ i _L | ≫ | 1 / L ・ K _F K _V / M ・ i _L | ……
(5) Therefore, sVs * (6).

(Ii) When ω >> L (| S | >> L) s1 / S ・ K _F K _V / M ・ i _L ＋ L / S ・ Vs * …… (7) From equation (3), | L / S ・Vs * | << | Vs * || 1 / S ・ K _F K _V / M ・ i _L | …… (8) Therefore, s1 / S ・ K _F K _V / M ・ i _L …… (9) .

From equations (6) and (9), the track crossing estimated velocity signal Vs of the light spot which is the output of the state observer 3 matches the detected velocity signal Vs * in the low frequency region, and the head actuator drive current i _L It turns out that it agrees with the integral. The frequency at which the division occurs is L [rad / sec], which coincides with the band of the state observer 3. Here, if L =
If ∞, then from equation (2), s = Vs * (10) and the conventional speed control system (8th
(Fig.) And the time response of the estimated velocity signal Vs is the third
Since it matches the output signal 15 in the figure, the dead time generated in the speed detection circuit 20 cannot be compensated. On the other hand, if L = 0, from Eq. (2), s = 1 / S · K _F K _V / M · i _L (11), and the time response of the estimated speed signal s is estimated as shown in FIG. Since it matches the speed signal 17, it is not affected by the dead time of the speed detection circuit 120 and the high frequency resonance characteristic of the head actuator 116 at all, but it is estimated that a slight offset is superimposed on the drive current i _L The estimation error of is increased.

At this time, the estimated speed signal s does not include the track swing speed Vd at all, and the estimated speed signal s is not the track crossing speed of the light spot 115 but the estimated value of the moving speed _VL of the head actuator 116. Therefore, at low speeds, when the moving speed V _L becomes so small that the track runout speed Vd cannot be ignored, the estimated speed signal of the track crossing speed (estimated value)
The error of s becomes large.

Therefore, the estimated speed is set by setting the gain L of the feedback element 11 sufficiently lower than the high-frequency resonance frequency of the head actuator 116 and the track crossing frequency of the light spot 115 and sufficiently higher than the track deflection basic frequency of the optical disc 101. The time response of the signal s is the broken line 16 in FIG.
As shown by, the waveform becomes an intermediate waveform between the output signals 15 and 17, and the dead time generated in the speed detection circuit 120 can be compensated to some extent.

In addition, since the transfer characteristic from the detected speed signal Vs * to the estimated speed signal s can be expressed by the first-order low-pass filter characteristic that is 1 / (1 + S / L) by the formula (2), dropout or recording on the optical disc 101 is performed. Even if the output signal (detection speed signal) Vs * is disturbed by the pits, the estimated speed signal s is hardly disturbed.

Further, while the light spot 115 is tracking on the track, the integrator 12 is reset by a command from the control mode detection circuit 4, and the speed is switched to the speed control mode. Is obviously zero, there is no error in the initial value of the estimated velocity output from the state observer 3 immediately after the transition to the velocity control mode. Even if an error occurs, the error is 1 / L
It converges to 0 with the time constant of.

Next, when calculating the open-loop transfer function of the speed control system shown in FIG. 2, G ₀₂ (s) = K _C K _A K _F K _V / MS ・ (S + L ・ G _L (S) ・ ( 1-e ^−sτ )) / Sτ / (S +
L) = K _C K _A K _F K _V / MS ・ (1 + L / S ・ G _L (S) (1-e ^−sτ )) / Sτ / (1
+ L / S) (12), and the high-range resonance characteristics G of the head actuator 116
_{If L} (s) has a peak frequency of ω _L , _L << ω _L
By setting the L in such a way _{that, | L / S · G L} (s) | S = jωL L / ω L | G L (Jω L) | ......
From (13), the effect of the size of the high-frequency resonance peak of the head actuator 116 on the open-loop characteristic of Eq. (12) is suppressed to L / ω _L times, and as shown in FIG. 12
The high frequency peak in the gain characteristic is smaller than that in the figure.

Also, unlike the frequency characteristic of the notch filter 122 of FIG. 10, the high-frequency resonance frequency ω _L does not have to be a specific frequency, and if the frequency is ω _L >> _L , the suppression effect at any frequency is obtained. And even if there are multiple peaks, they are suppressed uniformly. Like the mechanical resonance characteristic G _L (s), the phase delay and gain drop due to the zero-order hold characteristic of the speed detection circuit 20 in Eq. (12) are alleviated, the phase of the open loop characteristic extends to the high range, and the system stability is improved. Is improved.

In FIG. 4A, an adder / subtractor amplifier circuit 114 obtained when the light spot 115 crosses the track groove on the optical disc 101.
Subtraction output signal (Fig. 4 (b)) and addition output signal (Fig. 4 (b))
Utilizing the fact that there is a 90 ° phase difference between Fig. 4 (c)) and Fig. 4 (e) when the waveform of Fig. 4 (d) rises.
If the level of “H” level or the “L” level of FIG. 4 (e) at the time of rising of the waveform of FIG. 4 (d),
It can be seen that the light spot 115 moves from left to right, and if the level of FIG. 4 (e) is reversed, the light spot 115 moves from right to left.

As described above, if the direction crossing direction of the light spot 115 is detected by the direction detecting circuit 1 and the polarity of the output of the speed detecting circuit 120 is switched depending on the direction crossing the track of the light spot 115, the speed control system becomes positive feedback. Stable operation.

FIG. 6 shows another embodiment of the present invention, which is an equivalent conversion of FIG. Therefore, the detected speed signal Vs *, the transfer function from the drive current signal i _L to the estimated speed signal s, and the open-loop transfer function coincide with the expressions (2) and (12), respectively.

Further, in FIG. 1, the polarity switching circuit 2 is provided immediately after the speed detection circuit 120, but the polarity may be switched so that the speed control system always becomes negative feedback. It may be provided immediately after the circuit 121 and after the state observer 3.

Further, in the above-mentioned embodiment, the track crossing speed or direction of the light spot 115 is detected based on the signal obtained by adding / subtracting and amplifying the output of the divided photodetector, but it is not necessarily the addition / subtraction amplified signal of the output of the divided photodetector. However, for example, when a sample servo system using an optical disk having no track groove is adopted, a tracking signal (track deviation signal) detecting means or a track crossing number detecting means and a signal corresponding to the total reflected light amount signal are detected. The track crossing speed or direction may be detected on the basis of the output of.

Alternatively, the direction may be detected from the address information of the optical disk or the like.

Further, in the above embodiment, the polarity of the output of the speed detection circuit 120 is switched based on the direction detection result detected by the direction detection circuit, but basically the direction is not reversed during speed control, and If the direction is reversed for a short time,
Since the estimated speed signal s which is the output of the state observing device 3 is determined almost only from the drive current signal i _L by the equation (9), the speed control system does not become a positive feedback, and the configuration without the direction detection circuit is adopted. Alternatively, the polarity of the output of the speed detection circuit may be switched based on the access direction command and input to the state observing device 3.

Further, in FIG. 2, the case where a linearly driven linear motor is used as the head actuator is described in detail, but a rotary actuator may be used, for example.
In that case, the mass M of the movable part in FIGS. 2, 3, and 4 is replaced by the moment of inertia J of the movable part.
That is, any type of actuator may be used as long as it is an actuator that drives the head. Further, the head actuator does not need to drive the entire head, and only a part of the head may be driven, for example, when a separate type actuator is used, and the light spot is largely moved in the radial direction of the disk during track search. Any actuator will do, first
It may also serve as the tracking actuator 112 in the figure.

[Effects of the Invention] As described above, according to the present invention, a status observing device is added to the speed control system of the optical disk drive at the time of track access, and the output of the speed detection circuit and the drive current of the head actuator are input to the status observing device. Since the track crossing speed of the light spot is estimated and the light spot crossing speed is controlled, the stability of the speed control system is improved, and the speed can be controlled not only for long distances but also for very short distances. ， The access time of the optical disk device can be greatly shortened,
Further, since the performance of the speed control system does not depend on the variation of the mechanical resonance frequency of the head actuator or the optical head and the number of resonance points, there is an effect that the head actuator and the optical head can be easily assembled.

[Brief description of drawings]

FIG. 1 is a block diagram of the overall configuration of an optical disk drive device showing an embodiment of the present invention, FIG. 2 is a block diagram of a speed control system in the optical disk drive device of FIG. 1, and FIG. 3 is an optical disk of FIG. FIG. 4 is a diagram for explaining the operation of the state observing device in the drive device, FIG. 4 is a diagram for explaining the operation of the direction detection circuit in the optical disc drive device of FIG. 1, and FIG. 5 is an open loop transfer characteristic diagram of the speed control system shown in FIG. FIG. 6 is a block diagram of a speed control system according to another embodiment of the optical disc driving apparatus of the present invention, FIG. 7 is a block diagram showing a configuration of a conventional optical disc driving apparatus, and FIG. 8 is a conventional optical disc driving apparatus. Block diagram of the speed control system of the speed control system, Fig. 9 is the high frequency resonance frequency characteristic diagram of the mechanical system, Fig. 10 is the frequency characteristic diagram of the notch filter in the speed control system of Fig. 8, Fig. 11 and Fig. 12 Fig. 8 An open-loop transfer characteristic diagram of a speed control system that. In the figure, 1 ... Direction detection circuit, 2 ... Polarity switching circuit, 3 ... State observer, 4 ... Control mode detection circuit, 20 ...
Speed detection circuit, 101 …… Optical disk, 104 …… Optical head, 1
14 ... Add / subtract amplifier, 115 ... Optical spot, 116 ... Head actuator, 117 ... Head actuator drive control circuit, 120 ... Speed detection circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] 1. An optical head comprising at least an objective lens for forming a light spot on an optical disc having a large number of tracks and a photodetector for receiving reflected light from the optical disc, and track access to the tracks of the optical disc. And a head actuator that moves at least a part of the optical head in the radial direction of the optical disk when performing the above, and a speed at which a track crossing speed signal of a light spot moving in the radial direction of the optical disk is detected from a light reception output to the photodetector. Detecting means, acceleration detecting means for detecting an acceleration signal of the optical head from a drive signal of the head actuator, inputting a track crossing speed signal from the speed detecting means and an acceleration signal from the previous period acceleration detecting means, The frequency corresponding to the moving speed of the head is When the frequency is lower than the reference frequency, a track crossing estimated speed signal that coincides with the track crossing speed signal output by the speed detecting means is generated, and when the frequency corresponding to the moving speed of the optical head is higher than the reference frequency. Is a state observing means for generating a track crossing estimated speed signal that matches the signal obtained by integrating the acceleration signal from the acceleration detecting means; and a target speed generating means for calculating a track crossing target speed signal from the track crossing number of the optical head. An optical disk drive device comprising: a head actuator drive control means for controlling the head actuator based on a track crossing target speed signal from the target speed generating means and a track crossing estimated speed signal from the state observing means. 2. A predetermined reference frequency of the state observing means,
It is set to be lower than both the mechanical resonance frequency of the configuration related to the driving of the optical head and the cross-track frequency of the optical spot of the optical head, and higher than the track deflection basic frequency due to the rotation of the optical disc. The optical disk drive device according to claim 1, wherein: 3. The method according to claim 1, wherein when the light spot of the optical head is tracking the track of the optical disk, the integration processing of the acceleration signal of the optical head by the state observing means is stopped. The optical disk drive device according to claim 1. 4. The optical disk drive according to claim 1, wherein the acceleration detecting means is configured to detect an acceleration signal of the optical head based on a drive current of the head actuator.