JP3339972B2 - Optical disk drive device and information signal evaluation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive having a function of searching for an in-focus position on an optical pickup medium information recording surface of an optical pickup.

[0002]

2. Description of the Related Art In recent years, with the increase in the density of recorded information, more precise focus error control has been required for optical disk drive devices.

An example of the above-described conventional optical disk drive will be described below with reference to the drawings.

FIG. 9 is a block diagram of a conventional optical disk drive. In FIG. 9, reference numeral 100 denotes an optical disk, which is mounted on a rotating shaft of a spindle motor 101. An optical pickup 102 has a laser light emitting element, an objective lens, and an objective lens actuator, and irradiates the optical disc 100 with a focused laser beam. The optical pickup 102 is further provided with a light receiving element, from which an information reproduction signal and a focus error signal are output. The information reproduction signal (RF) is
The information recorded on 0 is read by a laser beam through an objective lens, and converted into an electric signal and output. The focus error signal (FE) is obtained by outputting an amount corresponding to the distance between the focal position of the focused laser beam and the information recording surface of the optical disc 100 as an electric signal. This focus error signal is fed back to the objective lens actuator of the optical pickup 102 via the feedback means 103, and as a result, control is performed so that FE = 0. At this time, the servo signal light receiving element is strictly adjusted in advance so that the focal position coincides with the information recording surface of the optical disc 101. However, the mounting of the servo signal light receiving element may be slightly displaced due to a change over time, a temperature change, or the like. At this time, even if FE = 0, there is an error between the focal position and the information recording surface. An existing condition occurs. When information is reproduced in a state where there is a defocus, the focused laser beam on the information surface of the optical disk spreads, and the discrimination ability of recorded information is reduced. As a result, the frequency of identification errors in the RF signal reproduced from the signal increases. Therefore, before reproducing the information, it is necessary to observe the state of the deviation by some method and search for the focal point position.

[0005] Reference numeral 111 denotes a transition signal generating circuit which first changes the focus control system by applying this output S to a focus control circuit 103 via a sample hold circuit 106 (for example, a straight line such as -FE0 → 0 → + FE0). (Which changes dynamically). If the offset amplitude is sufficiently large, the laser beam focus moves across the information recording surface. 104 is an amplitude detecting means,
The change in the amplitude of the RF signal at this time is detected. 10
Reference numeral 5 denotes a maximum value detection circuit which detects that the amplitude of the RF signal has become maximum at the moment when the laser beam focus crosses the information recording surface. Further, the sample hold circuit 106 holds the value of the shift signal S at the time of the maximum amplitude of the RF signal, and sets the value as the correction offset amount ΔFE.
Add to 3. At this time, the focal point of the focused laser beam is almost in the vicinity of the optical disk recording medium surface, and this relationship is kept almost constant by the focus control circuit. In addition,
It is assumed that the above series of operations is separated by the controller 107. (For example, Optical Memory Symposium '90 Proceedings, pages 9-10)

[0006]

However, in the above-described configuration, a large-amplitude transition signal S is added to the focus control system in order to search for the in-focus position. When long continuous information must be continuously reproduced by a device that handles a disk or a video disk, the focus position can be searched only when the optical disk drive is started. As a result, there has been a problem that the temporal change of the temperature characteristic and the like of the light receiving portion of the optical pickup cannot be followed, and the focus position may be largely shifted after a long use. Further, since the change in the amplitude does not appear so remarkably with respect to the focus shift, there is a problem that it is difficult to increase the detection sensitivity of the in-focus position.

[0007] An object of the present invention is to solve the above problems.

[0008]

SUMMARY OF THE INVENTION The present invention provides an information reproducing signal.
And the phase error between the reference clock and the detected phase
So that the average of the difference between the lead and the phase lag is 0
Optical disk drive with PLL for executing feedback control
Eve device for detecting the phase lead and phase lag
Sum calculating means for generating a sum signal of the summed signals, and the sum signal
Low-pass filter to generate information evaluation signal by smoothing
And the information evaluation signal is minimized.
Offset applying means to displace the actuator
An optical disk drive device characterized by having
I do.

[0009]

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical disk drive according to a first embodiment of the present invention. The configuration of the present embodiment will be described with reference to FIG.

In FIG. 1, reference numeral 100 denotes an optical disk,
1 is a spindle motor. An optical pickup 1 includes an objective lens 1a, a focus actuator 1b,
It comprises a tracking actuator 1c, a laser diode 1d, and a light receiving element 1e having a plurality of light receiving sections. Reference numeral 2 denotes a head amplifier, which combines and outputs a focus error signal FE, a tracking error signal TE, and an information reproduction signal RF from the output signal group of the light receiving element 1e. The focus error signal FE and the tracking error signal TE are supplied to the focus actuator 1b,
It is supplied to the tracking actuator 1c.

Reference numeral 5 denotes a rotation detecting means which detects that the spindle motor 101 has made one rotation, and outputs a rotation detection pulse signal REV. Reference numeral 7 denotes a track jump pulse generating means which adds a track jump pulse TJP to the tracking error signal TE every time the rotation detection pulse signal REV is input, and executes a track still operation.

Reference numeral 8 denotes a binarizing circuit, which is an information reproduction signal RF.
Is binarized by providing an appropriate threshold value to obtain a digital signal (WD). Reference numeral 9 denotes a buffer memory for writing the digital signal WD in synchronization with the write clock CKW, reading the digital signal WD in synchronization with the read clock CKP, and forming an information output signal RD. Reference numeral 10 denotes a memory controller which manages addresses for writing and reading to and from the buffer memory 9 and generates a signal EW for enabling the write clock CKW. Further, a control signal STON for permitting the track still jump is supplied from the memory controller 10 to the gate 6. Reference numeral 11 denotes a clock extracting unit that extracts a clock component from the information reproduction signal RF and uses it as the write clock WCK.

Reference numeral 12 denotes an information signal evaluation means for uniquely detecting the degree of deterioration of the information reproduction signal RF. For example, it detects how much the rising timing of the binary signal of the information reproduction signal RF fluctuates with respect to the rising of the reference signal (detects the amount of jitter), and converts the amount to an electric signal (information evaluation signal: (VRF). Reference numeral 13 denotes an offset controller that generates an offset fine adjustment signal ± ΔFE based on the rotation detection signal REV, the control signal STON, and the information evaluation signal VRF. Reference numeral 14 denotes a focus offset accumulating means for accumulatively adding the offset fine adjustment signal ± ΔFE to determine a focus offset amount.

The operation of the optical disk drive configured as described above will be described below with reference to FIGS.

First, the laser beam emitted by the laser diode 1d of the optical pickup 1 is reflected by the information recording surface of the optical disc 100 via the objective lens 1a, and reaches the light receiving element 1e again through the objective lens 1a. Light receiving element 1
e is appropriately divided, and the head amplifier 2 synthesizes the focus error signal FE, the tracking error signal TE, and the information reproduction signal RF from the output signal group. The focus error signal FE passes through the feedback circuit 3 and the optical pickup 1
As a result, the distance between the focus of the laser beam emitted from the objective lens and the information recording surface of the optical disk is kept substantially constant. The tracking error signal TE is fed back to the tracking actuator 1c by the feedback circuit 4, and as a result, the laser beam focus scans on the information track formed in a spiral shape on the optical disc 100. As described above, while the focus / tracking control loop is operating, the information reproduction signal RF such as a moving image recorded along the optical disk information track can be continuously reproduced.

This information reproduction signal is converted into a digital signal WD by the binarizing means 8, and then written into the buffer memory 9 in synchronization with the write clock CKW. Since the write clock CKW is extracted from the information reproduction signal RF as described above, the write speed at this time is the transfer rate of the information reproduction signal RF. The buffer memory 9 is a so-called FIFO (First In First Out), and is read out in chronological order in synchronization with the read clock CKR. Here, between the two clocks, “write clock CKW frequency> read clock C
KR frequency ".

That is, the data is read from the buffer memory 9 at a speed lower than the writing speed. However, since the capacity of the buffer memory is limited, if the writing is continued at a speed faster than the reading, the memory is naturally overrun. Therefore, the memory controller 10 changes the enable flag EW from H → L when the memory buffer 9 is about to be filled with information.
Then, the supply of the write clock CKR is stopped, and the write operation is interrupted until the buffer memory 9 becomes sufficiently empty. The filling degree of the memory buffer 9 is determined by counting up the write clock CKW and the read clock CKR, respectively.
It can be known by comparing the difference with the total memory capacity. At this time, if continuous tracking to the optical disk is continued, the information of the buffer memory write inhibition period is lost, so the tracking still must be performed at the timing when the writing is interrupted. The control signal S for this
TON is issued from the memory controller 10.

The rotation detecting means 5 detects that the spindle motor 101 on which the optical disk 100 is mounted has made one rotation, and issues a rotation detection pulse signal REV. This signal REV is supplied to the jump pulse generating means 7 when the gate 6 is opened by the control signal STON. The state of the above signals is shown in FIG. The signal TJP emitted from the jump pulse generating means 7 is composed of an acceleration pulse (+ side) and a deceleration pulse (-side), and is applied to the tracking control loop. First, the tracking actuator is accelerated in the backward direction by the acceleration pulse, and a deceleration pulse is applied at an appropriate timing to apply a brake to reach the track one lap before. As a result, the laser beam spot repeatedly scans the same track.

During this still operation, an operation for searching for an optimum focus point is performed. First, when receiving the control signal STON, the offset controller 13 generates a positive or negative offset fine adjustment signal + ΔFE, −ΔFE.
The fine adjustment signal is cumulatively added by the focus offset accumulating means 14, and a correction offset (transition) signal FE0 is obtained.
Is added to the focus control loop. At this time,
If there happens to be a defocus in the direction opposite to the offset fine adjustment signal, the defocus is reduced but may be enlarged on the contrary. The information signal evaluation means output signal VRF is used to determine this. In the present invention, the information signal evaluation means is assumed to observe the jitter of the information reproduction signal RF.
As in the conventional example, the reproduction amplitude may be used.
The reproduction signal jitter takes a minimum value at the in-focus position, and the value increases according to the defocus. The focus offset is finely adjusted while observing this output. This algorithm may be, for example, one as shown below. Here, VRF ^-1 means an information evaluation signal before adding an offset fine adjustment signal.

As a result of this algorithm, the information evaluation signal V
Continue adding + ΔFE or −ΔFE so that RF decreases. As an example, the operations of step2 and step3 are shown in FIG.
B. At this time, the focus offset accumulating means 14
Accumulates the fine adjustment signal ± ΔFE from the start of the focal point position search. Therefore, if the information evaluation signal VRF becomes sufficiently small as a result of the cumulative addition, at this time, FE0
Is an appropriate offset correction amount. The smaller the absolute amount of ΔFE is, the higher the adjustment accuracy is, but the search time is increased. Therefore, it is preferable that the depth is approximately 1/10 of the depth of focus. For example,
In an optical system having an NA of 0.5 and a wavelength (λ) of 800 nm, the focal depth is λ / 2NA ² = 1.6 μm.
It is desirable that the thickness is about 0.16 μm.

While this search is being performed, new information is not read from the optical disk medium 100, and the information stored in the buffer memory 9 is read and transferred. When the buffer memory approaches empty, the memory controller 10 releases the control signal STON and restarts reading of information. That is, the track jump is stopped by closing the gate 6, and continuous reproduction is started. Further, the enable flag EW is changed from L to H, and the writing to the buffer memory 9 is restarted. At the same time, the offset controller 13 interrupts the search operation. At this time, step 7: If VRF <VRF- ^1, then the process is interrupted as it is so as not to interrupt the search while adding an incomplete offset. step8: If VRF ≧ VRF- ^1, then a fine-tuning signal having a polarity opposite to that of the previous time is added and the processing is interrupted. Such an algorithm may be executed.

Thereafter, the same operation is repeatedly executed. That is, when the buffer memory 9 becomes full again, the control signal STON is issued, and the in-focus point search processing is restarted.

As described above, according to the present embodiment, the focus control is finely offset (shifted) during the intermittent reproduction, so that the search of the focal point is always executed without affecting the reproduction of information. be able to.

Although the fine adjustment signal ΔFE is a constant in the present embodiment, the fine adjustment signal ΔFE may be changed as appropriate. That is, a relatively large value (for example, 0.3 μm) may be taken in the initial stage of the adjustment, and the fine adjustment amount may be reduced (for example, 0.1 μm) as approaching the focal point.

Here, an embodiment of the information signal evaluation means 12 described in the above embodiment will be described.

Hereinafter, a second embodiment of the present invention will be described.

FIG. 3 is a block diagram of the information signal evaluation means (12) in this embodiment.

In FIG. 3, reference numeral 121 denotes a binarizing circuit;
2 is a phase comparison circuit, 124 is a differential circuit, 125 is an integration circuit, 126 is a VCO (Voltage Controlled Oscillator), and the above components form a PLL. That is, as shown in FIG. 4, the binarized information reproduction signal RF is
The reference clock CK is supplied to the V input to the U input of 22, and if the rising phase of the former is ahead of the latter, a pulse signal having a width corresponding to the advance is output to the UP.
Conversely, if the former rises later than the latter, a pulse signal having a width corresponding to the delay is output to the DN output.
As shown in FIG. 3, this circuit includes two pairs of flip-flops each triggered by the rise of the information reproduction signal RF and the reference signal CK, and a NAND gate which performs a feedback reset on the flip-flop by the logical product of the outputs of the two. Be composed. The outputs of both flip-flops are UP,
DN. The differential signal of both the UP and DN outputs is taken, further integrated to control the oscillation frequency of the VCO 126, and this output is fed back to the V input as a reference clock CK, whereby the information reproduction signal RF and the reference clock CK are obtained. Can be set to zero.
However, even if the average value is 0, the phases of both do not always coincide completely. Small fluctuations of phase lead / lag around 0, that is, jitter exist. The magnitude of this jitter depends on the amount of defocus. That is, the jitter is minimized at the in-focus position, and the jitter (phase / fluctuation amount) increases as the defocus increases. Since this jitter only needs to look at the amount of variation regardless of the phase lead / lag,
What is necessary is just to measure the pulse width of the pulse signal of both the P and DN outputs, and what is smoothed is used as the jitter detection signal, that is, the information evaluation signal VRF.

However, at this time, it is necessary to remove the offset pulse due to the delay inside the phase comparison circuit 122. That is, if there is no delay in the above circuit, if signals in phase are input to the inputs U and V, signals (very thin) having a pulse width of 0 should be output to the outputs UP and DN. Thus, an (offset) pulse signal having a width corresponding to the delay of the flip-flop and the NAND gate constituting the same circuit is output. When the differential of the output of the phase comparator is used for the PLL, this offset component is canceled each other, so that there is no problem. However, when the jitter is detected from the sum signal of both outputs as in this embodiment, this offset component is used. Is added. Therefore, in this embodiment, a feedback reset circuit is formed by the flip-flop and the NOT gate having the same delay characteristics as the flip-flop and the NAND gate, and the dummy pulse having the same width as the offset pulse is input each time the information reproduction signal RF is input. A DM is generated, and the offset is removed. The EXOR 129 performs this logically. The buffer 128 is an OR gate 1 (for generating UP + DN) for timing adjustment.
With the same delay as 27.

The jitter pulse (pulse edge fluctuation) PJ generated in this manner is supplied to a charge pump circuit 13 composed of a diode switch and a low-pass filter.
At 0, the pulse width is converted to a voltage. That is, the capacitor is charged while the jitter pulse signal PJ is at H, and this charge is held when it becomes L. As a result, a voltage substantially proportional to the pulse width is obtained. The sample-and-hold circuit 131 samples and holds this voltage to generate a hold signal HJ. The sample hold timing is determined by the delay element 133 based on the U input. This timing is further delayed by the delay element 134, and the switch 13
In step 2, the charge pump 130 is discharged. FIG. 4 shows the relationship between the jitter pulse signal PJ and the hold signal HJ. The dotted line in the figure is the charge voltage.

The hold signal is further smoothed by a low-pass filter 135 and output as an information evaluation signal VRF.

As described above, in this embodiment, the information evaluation signal VRF can be generated from the output of the PLL phase comparator.

In this embodiment, the EXOR 129 is used to remove the offset pulse. However, after the dummy pulse DM is converted into a voltage by a charge pump and a sample and hold circuit of another system, the EXOR 129 is subtracted from the information evaluation signal VRF. You may do it. This eliminates the need for fine timing adjustment between the phase comparator output and the dummy signal.

Although the clock extracting means 11 is used in the first embodiment, this can be generally realized using a PLL. Therefore, it can be shared with the PLL shown in the second embodiment. in this case,
The reference clock signal CK generated by the VCO 126 may be used as the write clock CKW.

As described above, in the first embodiment, the method of making the reproduction rate from the optical disk higher than the reading rate from the buffer memory and performing the search for the in-focus position during the reproduction waiting period is described. In the example, the method of collecting the information evaluation signal at the time of focusing search from the PLL jitter has been described. In the first embodiment, a conventionally used amplitude detection means may be used as the information signal evaluation means (in the case of using jitter, the minimum value search is used, but in the case of the amplitude, the maximum value search is used). In digital recording in which information is recorded in binary of 1 or 0, jitter can be performed with higher sensitivity than amplitude in order to more strictly evaluate an information reproduction signal.

However, while jitter detection can be performed with high sensitivity, it is sensitive to noise, so that it is necessary to consider this point sufficiently. The information reproduction signal is not always reproduced under a certain condition. That is, although the information reproduction signal is composed of signals of a plurality of frequencies (the spectrum is dispersed), the amount of jitter generated (at the same defocus) differs depending on each frequency. You will have fluctuations. Furthermore, there are fluctuations in jitter due to disturbances in the reproduction signal due to damage to the surface of the optical disc 100, which adversely affect accurate focus search as information evaluation signal noise. To minimize this, the low-pass filter 13 shown in FIG.
It is necessary to increase the time constant of 5 to enhance the smoothing of the information evaluation signal VRF. However, as a result, at the time of focusing search, a change in jitter cannot be detected even when a shift signal is applied at a high speed, and it becomes difficult to apply wobbling control as used in, for example, US Pat. No. 4,032,776. . This method is a classical method of searching for an extreme value (maximum value or minimum value) of the evaluation function using a relatively small amplitude displacement signal. In the above-described conventional example, the focus actuator is vibrated at a high speed, A product detection of the fluctuation of the information reproduction signal amplitude is performed, and the maximum point of the reproduction signal amplitude is searched to find a focal point position. Instead of the reproduced signal amplitude, the reproduced signal jitter (VRF)
And if the minimum point can be searched, the focus can be adjusted to the in-focus position with higher accuracy. However, since high-speed wobbling cannot be performed as in the related art, some contrivance is required. This will be described in the following third embodiment.

Hereinafter, a third embodiment of the present invention will be described.

FIG. 5 is a block diagram of the optical disk drive of the third embodiment.

In FIG. 5, an optical pickup 1 includes an objective lens 1a, a focus actuator 1b, and a light emitting unit 1.
d a flat half mirror that generates astigmatism in addition to d.
As shown in FIG. 6, a light receiving element 1e divided into four orthogonal sections is provided.
Numeral 31 denotes an arithmetic means for generating a diagonal sum signal (A + C, B + D) of each of the divided portions (A, B, C, D) of the light receiving element 1e. Variable gain amplifiers 32 and 33 amplify the diagonal sum signal with gains 1 + α and 1-α, respectively. 34 is a differential means, 3 is a feedback means, and 35 is an addition means, and a signal passing through the above-mentioned components is fed back to the focus actuator 1b.

36 is a sine wave (transition signal) generating means,
Is a variable delay means, and 38 is a gain controller. 7
Numeral 0 denotes an adding means, which generates a total addition signal of the light receiving element 1e and sets it as an information reproduction signal RF. Reference numeral 120 denotes a jitter detection circuit (information signal evaluation device), which is shown in FIG. 72 is a multiplying means, and 73 is a low-pass filter. Thus, the gains 1 + α and 1−α are determined. Reference numeral 39 denotes a phase detecting means for detecting a phase difference between the sine wave S and the focus error signal FE.

The third embodiment configured as described above will be described below.

First, when the sine wave signal S (= sin ωt) generated by the sine wave generation means 36 is applied to the focus servo loop, the focus actuator 1b changes accordingly. Assuming that this variation is Δx, Δx = asin (ωt−ψ) (1) (a: constant). ψ is the tracking delay of the focus servo. When the focus actuator 1b changes, the output signal VRF of the jitter detection circuit 120 also changes. now,
Assuming that the output of the jitter detection circuit 120 with respect to the focus shift x is approximated by VRF = bx ² + c (2) (b, c: constant), (1) is substituted into (2), and VRF = b ( x ₀ + Δx) ² + c = b ｛x ₀ + asin (ωt-ψ)｝ ² + c (3) Here, x ₀ is a DC component of a focus shift caused by an optical pickup adjustment error or the like, and is an object to be removed in the present invention.

The sine wave signal S is further given a delay ψ of the same amount as the servo loop follow-up delay by the variable delay means 37, and the product is calculated with the jitter detection signal VRF. VRF × asin (ωt-ψ) = (abx 0 2 + c) sinθ + 2a 2 bx 0 sin 2 θ + a 3 bsin 3 θ: θ = ωt-ψ (4) Integrating the product output signal by the integrating means 73, sin [theta , S
Since in ³ θ is an odd function, the integral value is 0. Therefore, when only the second term is calculated, V = ∫ (VRF × asin θ) dθ = 2a ² bx ₀ ∫sin ² θdθ = 2πa ² bx ₀ (5) is, the signal V is obtained which linearly proportional to the focus offset x _0. x ₀ = 0 when there is no focus offset, and the jitter detection function (2) naturally takes the minimum value at this time.

If the multiplied signal V is fed back to the focus servo loop as it is, control is performed so that V = 0. In this embodiment, the multiplied signal V is used not as an "offset" but as a balance correction.
As described above, the main factor of the focus offset is caused by the optical axis shift of the light incident on the light receiving element, that is, the light receiving balance. Before describing this, a method of detecting a focus error signal using the light receiving element will be briefly described. First, astigmatism occurs when the light beam reflected from the optical disc medium 100 passes through the flat plate half mirror 1f. That is, two points separated in the optical axis direction can be focused.
Further, the shape of the image at each focal point is an elliptical shape orthogonal to each other. Therefore, the light receiving means 1 divided into four orthogonal sections
e is set at approximately the center of both focal points, the light receiving portions A and C are adjusted so as to be in the longitudinal direction of one image, and the light receiving portions B and D are adjusted so as to be in the longitudinal direction of the other image. If the intersection is adjusted so as to completely coincide with the optical axis, the outputs A, B, C, D
By calculating FE = (A + C)-(B + D) (6), a focus error signal is obtained.
In this case, FE = 0 in the focused state.

Actually, however, A + C ≠ B + D is established even in the focused state because of the optical axis shift, so that FE = 0 is not achieved, and if focus control is performed so that FE = 0, an offset occurs. Therefore, in this embodiment, the gain balance adjustment is performed on the bidiagonal sum signal so that (1 + α) (A + C) = (1−α) (B + D) at the focal point, and FE = (1 + α) (A + C) − (1 −α) (B + D) (8) The focus error signal is obtained from the equation (8), and the optical axis is equivalently adjusted. This α is determined from the multiplied signal V by the gain controller 38 in the following manner.

Α = ∫Vdt (9) That is, the variable gain amplifiers 32 and 33 → focus actuator → light receiving means 1e → jitter detection means 120 → multiplier 72 → gain controller 38 → variable gain amplifiers 32 and 33 constitute a closed loop. Is determined when the closed loop reaches an equilibrium state. Now, α =
If 0 and there is a focus offset, V ≠
A multiplied signal of 0 is generated, and this is time-integrated to determine a coefficient α represented by (9). As a result, when the offset is reduced, the multiplication signal V is also reduced.
When = 0, α becomes a constant value, and the gain balance is determined.

The merit of removing the offset by adjusting the gain balance in this embodiment is that the servo loop does not run away when the light does not reach the light receiving means due to a scratch on the disk surface or the like. In other words, simply adding a correction offset causes the offset to act as a DC shift when there is no light, and accelerates the focus actuator in one direction.
= 0, so this does not occur.

The feature of this embodiment is that the jitter detection signal V
The sine wave signal S to be multiplied by RF is to be delayed by variable delay means. If the frequency of the sine wave signal S is sufficiently higher than the band frequency (〜2 kHz) of the focus servo loop, in (1), ψ = 180 °, and the focus is obtained by simply inverting the polarity without delay. A signal in phase with the fluctuation can be obtained.

However, when the jitter detecting means of FIG. 3 is used as in this embodiment, a sine wave having a high frequency cannot be used as described above. The reason is that if jitter is to be detected with a sufficient SN, averaging must be performed sufficiently. Therefore, even if a focus transition is given at a high frequency, the jitter fluctuation accompanying this disappears during this averaging process, and (1) )
This is because the focus correction signal V cannot be obtained even if (5) is executed. Therefore, in the present embodiment, a sine wave signal S having a sufficiently low frequency (about 10 to 100 Hz) in the servo band is used.

However, at this time, the delay of the focus actuator has a finite value of 0 <ψ <180 °. Therefore, it is necessary to use the variable delay means 37. This delay phase difference ψ
Can be obtained by detecting the phase difference between the sine wave signal S and the focus error signal FE by the phase detecting means 39.

Although the method of using astigmatism to detect a focus error signal has been described in the present embodiment, other methods may be used as long as they substantially generate two focal points. For example, a half mirror is placed in the reflected light beam path, and a light receiving unit is provided before and after each of the focal points of the reflected light and the transmitted light, and a signal corresponding to the magnitude of the irradiation light at each light receiving unit is transmitted to the above (A + C). ) And (B + D), offset correction can be performed in the same manner.

As described above, according to the present embodiment, the jitter can be minimized by adding a period change equal to or less than the focus servo band frequency to the focus servo loop. Further, in the next embodiment, a method will be described in which a noise component can be removed even if the time constant of the low-pass filter 135 of the information signal evaluation circuit in FIG. 3 is reduced.

In this embodiment, the jitter detection circuit 120
3 is used, but the present invention is not limited to this as long as at least the information reproduction signal jitter is detected. For example, as long as the offset pulse as described above can be ignored, a configuration in which a circuit for generating a dummy pulse is removed from the configuration shown in FIG. 3 may be used. In this embodiment, the sine wave signal S and the jitter detection signal VRF are used.
Was multiplied using the multiplying means 72, but this may be approximately performed without using the multiplying means. For example, even if the latter is sampled and held at the former peak point, a result similar to a multiplication operation can be obtained.

Hereinafter, a fourth embodiment of the present invention will be described.

FIG. 7 is a block diagram of an optical disk drive according to a fourth embodiment of the present invention.

In FIG. 7, an optical disk 100, a spindle motor 101, an optical pickup 1, a head amplifier 2, feedback means 3, 4, a rotation detecting means 5, a track jump signal generating circuit 7, and an information signal evaluating means 12 are provided in the first embodiment. Therefore, the third embodiment may be used. 22 is a synchronous multiplying means,
This is to generate a pulse signal having a cycle obtained by dividing one rotation of the spindle motor 101 by a predetermined number. Numeral 23 denotes a counter which generates a control signal C whose state switches each time the one-rotation detection signal REV is received. Reference numeral 25 denotes a switch for switching the output lines VRFa and VRFb of the information evaluation signal VRF by the control signal C, reference numerals 26a and 26b denote buffer memories for temporarily storing these output signals, and reference numeral 27 denotes a counter for generating the write address. Reference numeral 28 denotes an offset generation unit that generates a focus offset shift in accordance with the control signal C. 29 is a clock generating means, 30 is a switch, and 31 is a counter. 32 calculates the difference between the information stored in the buffer memories 26a and 26b,
Differential means for outputting as VRF.

The operation of the fourth embodiment configured as described above will be described below.

First, it is assumed that the track jump pulse TJP generated by the rotation detecting means 5 and the track jump signal generation circuit 7 is applied to the tracking control loop, and the track still operation is started. At this time, the first rotation detection signal REV is supplied to the counter 23, and the output of the control signal C changes from 0 to 1. Upon receiving the output C = 1, the switch 25 conducts to the VRFa side, and the information evaluation signal VRF is written to the buffer memory 26a. The operation at this time is the spindle motor 10
It is executed in synchronization with one rotation. That is, the signal WCK generated by the synchronous multiplier 22 has a predetermined number of pulses per rotation of the motor, and the counter 27 generates a write address from the pulses. As a result, an information evaluation signal at a point obtained by equally dividing a given number of tracks on the optical disc 100 into a predetermined number is written into the buffer memory 26a.

When the spindle motor 101 completes one rotation, and enters the next rotation, the track jump pulse TJ is returned again.
P is output, and the optical pickup operates the same track again. Since the rotation detection signal REV is input to the counter 23 again, the state of the control signal C changes from 1 to 2.
In response, the switch 25 switches to the VRFb side,
The information evaluation signal VRF is written to the buffer memory 26b. Also at this time, since the writing is executed in synchronization with the synchronous multiplication signal WCK, the information evaluation signal VRF at the same point group as before is written. However,
This time, the control signal C = 2 is the offset generation means 2
8, the offset generating means 28 generates a sinusoidal focus shift signal XFE as shown in FIG. This signal is applied to the focus control loop and intentionally causes a defocus. Therefore, the information evaluation signal VRFb observed at this time has a variation corresponding to the defocus. FIG. 8 shows the state at this time together with the information evaluation signal VRFA for the first rotation. Information evaluation signal VRF
Originally has a fluctuation component due to a reproduction information pattern, damage to an optical disk medium, or the like, which depends on the reproduction position of the optical disk, and thus it can be considered that the same fluctuation is superimposed at the same location. Accordingly, by subtracting this from the information evaluation signal VRFb obtained by adding the focus shift in the second rotation with reference to the information evaluation signal VRFa in the first rotation, the fluctuation component is removed as shown in FIG. In addition, it is possible to extract only a change component caused only by the focus shift. This is because the buffer memories 26a and 26b have already stored the information evaluation signals for two tracks of the track.
This can be realized by simultaneously reading out the information from the data and calculating both outputs by the differential means 32. The read timing is determined by the counter 23 when the rotation detection signal REV for the third rotation of the optical disk is used.
Then, when the control signal C changes from 2 to 3, the gate 30 is opened, and the read clock RCK generated by the clock generator 29 is supplied to the counter 31 to generate a read address.

As described above, according to the present embodiment, it is possible to remove information evaluation signal noise due to signal spectrum and medium damage without excessive smoothing means.

As described above, according to the above embodiment, the following effects are exhibited. (1) A buffer memory 9 for temporarily writing a reproduced information signal and reading the information signal at a speed lower than the reproduction speed of the information signal, and a tracking control for a signal for interrupting the writing operation and causing the laser beam to perform still tracking on a predetermined track. A memory controller 10 for supplying the system;
By providing the offset controller 13 for giving the focus offset during the interruption period, it is possible to add a focus transition between the intermittent reproductions, and as a result, it is possible to always execute the focus search. (2) Instead of the conventional amplitude means, the differential phase comparator 12
2 and the use of the information signal evaluation device having the time-to-voltage conversion means 130 for time-converting the added output pulse signal, the jitter component of the information reproduction signal RF that changes sensitively to defocus is not regarded as the evaluation value. , It is possible to increase the exploration sensitivity. (3) When the information signal evaluation device is used, a signal obtained by multiplying a signal obtained by delaying the sinusoidal focus shift signal by a predetermined amount by the output of the device and feeding back the result to a focus control system has a small amplitude and a low amplitude. The search using the frequency shift signal becomes possible, and as a result, the S / N of the jitter detection can be improved. (4) The information signal evaluation device output signal VRF at the time of the first still tracking is temporarily stored, and the content of the temporary storage means is subtracted from the output signal to which the focus shift signal is added at the time of the second still tracking. By doing
By removing a noise component generated by a pattern of recorded information or a scratch on the optical disc, the jitter detection sensitivity can be dramatically improved.

When the in-focus point search is performed using the information signal signal from which the noise component has been removed by the above-described method, the first focus search is performed.
Either of the method of the third embodiment or the third embodiment can be executed with higher accuracy and more quickly.

In this embodiment, the information evaluation signal is directly stored in the buffer memories 26a and 26b. However, when the information evaluation signal is combined with the first and second embodiments,
The averaged information evaluation signal may be stored.

[0066]

As is apparent from the above description, the present invention has an advantage in that even when continuous information is handled, a focus search can be executed by adding a focus transition while information is handled.

Further, the present invention has an advantage that the search sensitivity can be further increased as compared with the conventional art.

Further, the present invention has an advantage that the S / N of jitter detection can be further improved as compared with the related art.

Further, the present invention has an advantage that the jitter detection sensitivity can be remarkably improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disk drive device according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining an operation in the embodiment.

FIG. 3 is a block diagram of an information signal evaluation device according to a second embodiment of the present invention.

FIG. 4 is a timing chart for explaining an operation in the embodiment.

FIG. 5 is a block diagram and a partial configuration diagram of an optical disk drive device according to a third embodiment of the present invention.

FIG. 6 is a block diagram and a partial configuration diagram of an optical disk drive device according to a third embodiment of the present invention.

FIG. 7 is a block diagram of an optical disk drive device according to a fourth embodiment of the present invention.

FIG. 8 is a timing chart for explaining the operation in the embodiment.

FIG. 9 is a schematic diagram of a conventional optical disk drive device.

[Explanation of symbols]

 Reference Signs List 1 optical pickup 3, 4 feedback control means 5 rotation detection means 7 jump pulse generation means 9 buffer memory 10 memory controller 12 information signal evaluation means 13 offset controller 23 counter 26a, b buffer memory 27 counter 28 offset generation means 31 counter 32, 33 Variable gain amplifier 36 Sine wave generating means 38 Gain controller 37 Variable delay means 100 Optical disk 101 Spindle motor 120 Jitter detection circuit (information signal evaluation device)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-231477 (JP, A) JP-A-7-302426 (JP, A) JP-A-6-139587 (JP, A) JP-A-6-314587 162519 (JP, A) JP-A-6-96520 (JP, A) JP-A-6-231467 (JP, A) JP-A-5-274786 (JP, A) JP-A-8-77577 (JP, A) Hikaru 4-45315 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 08-7/10 G11B 20/10-20/16

Claims (8)

(57) [Claims] 1. A phase error between an information reproduction signal and a reference clock.
Detects the difference and averages the difference between the detected phase lead and phase lag
P for executing feedback control so that the value becomes 0
An optical disc drive device provided with an LL, wherein a sum signal of the signals obtained by detecting the phase advance and the phase delay is
A sum calculating means for generating, and an information evaluation by smoothing the sum signal.
A low-pass filter for generating a value signal, and further actuating the information evaluation signal to a minimum.
Having offset applying means for displacing the eta
An optical disk drive device characterized by the above-mentioned. 2. An information reproduction signal corresponding to a transition of a reference clock.
Pal according to the difference in lead time or difference in delay of signal transition
Phase comparison means for generating a pulse signal having a pulse width of
Time-voltage conversion means for converting a pulse width of a signal into a voltage,
Sample and hold means for holding the voltage value for a predetermined period
Information evaluation signal from the sample-and-hold means output.
2. The optical disk according to claim 1, wherein
Screen drive device . 3. An information reproduction signal is temporarily written,
Temporary storage means for reading out at a lower speed than the information reproduction signal
And temporary storage control for executing and interrupting the above writing
Means during which the information evaluation signal is
The feature is to displace the actuator so that it becomes smaller
The optical disk drive device according to claim 1, 4. A method for detecting one rotation of an optical disk medium and detecting
A rotation detecting means for generating a rotation signal;
During the write suspension period, the pulse signal
Tracking system for one-track jump signal according to occurrence
In addition to the control means, the focal point of the focused beam is
4. The optical disc according to claim 3, wherein the optical disc is moved to a position.
Screen drive device. 5. Writing to the temporary storage means is performed based on a reference clock.
4. The method according to claim 3, wherein the step is executed in synchronization with the task.
Optical disk drive device. 6. An information track provided on an optical disk medium.
Tracking system that controls the focused beam to scan
What optical disc drive apparatus der provided with the control means, said focusing beam less any portion of the information track
Control the tracking control means so that both scan twice.
A track repetitive scanning means for controlling an arbitrary portion of the information track when it is scanned for the first time;
Temporarily store the output signal of the obtained information signal evaluation means
A temporary storage means, and further scans any part of the track for the second time and thereafter.
Information evaluation signal obtained at the time of
Position of the focused ray according to the difference between the obtained information evaluation signals
2. The apparatus according to claim 1, further comprising means for correcting
Optical disk drive device. 7. The optical disk medium according to claim 7, wherein the track repetitive scanning means is an optical disk medium.
Tracking system for track jump signal according to rotation of
7. The optical device according to claim 6, wherein the optical data is supplied to control means.
Disk drive device . 8. An actuator control by generating an alternating signal.
Signal generating means to be added to the loop, and multiplying means for multiplying the information evaluation signal and the alternating signal by each other
If, accession to low-frequency component of the output signal of said multiplying means is 0
Correction control means for correcting the tutor position at any time, and further controlling the frequency of the alternating signal by the actuator control;
Below the band frequency of your loop, and
Means for delaying the phase by a predetermined amount and supplying it to the multiplication means
The optical disk drive according to claim 1, wherein the optical disk drive is provided.
Live equipment.