JP3192867B2 - Pulse width fluctuation detection device and in-focus position detection device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is, re-light disk drive
The present invention relates to a pulse width fluctuation detecting device for detecting a pulse width fluctuation of a raw signal with high accuracy, and a focusing position detecting device using the same.

[0002]

In recent years, focus locating device Ri Tsutsua become indispensable to optical disk drive apparatus, the fine
Every time also being high demand. Hereinafter, an example of a conventional in-focus position searching device will be described with reference to the drawings.

FIG. 13 is a block diagram of a conventional in-focus position searching device. In FIG. 13, reference numeral 101 denotes an optical disk, which is mounted on a rotating shaft of a spindle motor 110. An optical pickup 102 has a laser light emitting element, an objective lens, and an objective lens actuator, and irradiates the optical disc 101 with a focused laser beam. The optical pickup 102 further includes an information signal light receiving element and a servo signal light receiving element. The information signal light receiving element outputs, as an information reproduction signal (RF), information obtained by reading information recorded on the optical disk 101 with a laser beam via an objective lens. The servo signal light receiving element outputs an amount corresponding to the distance between the focal position of the focused laser beam and the information recording surface of the optical disc 101 as a focus error signal (FE). This focus error signal (FE) is fed back to the objective lens actuator of the optical pickup 102 via the focus control circuit 103, and as a result, the focus position and the optical disk 1
01 is kept constant with the information recording surface. If this distance is "0", that is, if the focal position is on the information recording surface, the information can be reproduced without any problem. However, if the information is reproduced in a state where the defocus is large, the focused laser beam on the information surface of the optical disk expands and the recording is performed. The ability to identify information is reduced. As a result, the frequency of identification errors in the information reproduction signal (RF) reproduced from the signal becomes high. Therefore, it is necessary to search for a focal point before reproducing information.

Reference numeral 111 denotes a disturbance signal generation circuit, which outputs a disturbance signal (S) as a sample / hold circuit (S /
H) The objective lens actuator is changed appropriately by adding to the focus control circuit 103 via 106.
An amplitude detection circuit 104 detects a change in the amplitude of the information reproduction signal (RF) at this time. Reference numeral 105 denotes a maximum value detection circuit, which detects that the amplitude of the information reproduction signal (RF) has become maximum. Further, the sample hold circuit 106 holds the value of the disturbance signal (S) at the maximum amplitude of the information reproduction signal (RF) and adds it to the focus control circuit 103 as a correction offset amount (ΔFE). 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 substantially constant by the focus control circuit 103. (For example, Optical Memory Symposium '90 Proceedings, pages 9-10)

[0005]

However, in the above-described conventional focus position detecting apparatus, when searching and adjusting the focus position, the value of the disturbance signal (S) is adjusted to correct the defocus. It takes time to make the focus position coincide with the recording surface, and the change in the amplitude of the information reproduction signal (RF) due to defocus is insensitive, making it difficult to detect the focus position with high accuracy. There was a problem that.

In addition, when the residual error of the focus control system due to the shake of the optical disk surface is large, if the disturbance signal (S) is added, the objective lens actuator will shake greatly and may deviate from the focus control range. Had. SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an in-focus position detecting device capable of sensitively detecting out-of-focus, and capable of detecting an in-focus position with high accuracy and stability, and a pulse width fluctuation detecting device used for the in-focus position detecting device. The purpose is to do.

[0007]

Pulse width variation detecting apparatus according to claim 1 of the present invention to solve the above problems SUMMARY OF THE INVENTION, the pulse width based on the information signal more reproduced from the optical disk medium in an optical pickup A pulse width fluctuation detecting device for detecting fluctuation and outputting the electric signal as an electrical signal, wherein the information
The signal is a first input signal and the reference signal is a second input signal.
Phase comparing means for detecting a leading phase difference and a lagging phase difference of the first input signal with respect to the second input signal , so that an average value of a difference between the leading phase difference and the lagging phase difference becomes zero. means for feedback controlling the frequency and phase of the reference signal, before Symbol proceeds by adding the phase difference and delay phase difference, its
Characterized in that the means for outputting a low frequency component as the pulse width variation detection signal and ingredients Bei. Claims of the present invention
The pulse width fluctuation detecting device described in 2 is an optical disk medium .
A detected pulse width variation detector for outputting as an electric signal the path <br/> variation in pulse width based on more information signals to be reproduced Hikari Luo pickup, clock extraction for extracting synchronizing clock signal from the information signal Means, variable delay means for delaying the information signal by an arbitrary period, latch means for determining and outputting the information signal at the rising or falling edge of the clock signal, and the variable delay
An output signal from the latch means as a first input signal;
The output signal from the first stage as a second input signal;
Adds the phase difference and delay phase difference lead of said second input signal of the power signal, characterized by comprising a means for outputting the low frequency component as the pulse width variation detection signal.
Also, the focused position locator according to claim 6 of the present invention, there is provided a focus position search apparatus having the pulse width variation detecting apparatus according to claim 1 or 2, wherein the pulse width variation detecting means, the pulse Optical fluctuation pickup means
Light from the light-emitting element of the
Information of the optical disk medium by the emitted laser beam
The light receiving element of the optical pickup by scanning the information recording surface
Pulse information obtained from the information reproduction signal output from the
The fluctuation of the pulse width of the
Configured to output as the gas signal, the of the a focus control means for controlling the arbitrary target value the distance between the focus and the optical disc medium of the objective lens, when the variation amount of the previous SL pulse width has the minimum value wherein the distance between the focus and the optical disc medium of the objective lens; and a focus error correction means for supplying to said focus control means as the target value. Ma
Further, the in- focus position detecting device according to claim 7 of the present invention ,
3. A focal point position detecting device comprising the pulse width fluctuation detecting device according to claim 1 or 2 as a pulse width fluctuation detecting device, wherein the pulse width fluctuation detecting device is an optical pickup.
Light emitted from the light-emitting element to the optical disk medium through the objective lens
Recording information on the optical disk medium by using the laser beam
From the light receiving element of the optical pickup by scanning the recording surface
Binary pulse information signal obtained from the output information reproduction signal
The fluctuation of the pulse width of the signal from the specified pulse width
Configured to output as items, the a focus control means for controlling the arbitrary target value the distance between the focus and the optical disc medium of the objective lens, the objective when the variation amount of the previous SL pulse width has the minimum value Focus error correction means for supplying the distance between the focus of the lens and the optical disc medium as the target value to the focus control means, and the focus of the objective lens and the optical disc
Between the distance to the medium and the optional target
The difference as focus error information, focus error change detecting means for detecting a small change amount of the focus error of the focus error information in one rotation cycle of the spindle motor on which the optical disk medium is mounted, and a disturbance signal having the rotational period so as not to exceed the range, characterized by comprising a means for supplying to said focus control means.

[0008]

According to the above arrangement, when the outgoing laser beam defocuses with respect to the information recording surface of the optical disk medium, the waveform of the information reproduction signal reproduced by the optical pickup is rounded. Based on this waveform, and outputs a binary pulse information signal binarizing means pulse width is changed. Based on the binary pulse information signal, the pulse width variation detection device outputs an electric signal corresponding to the variation of the binary pulse information signal with respect to the reference pulse width. As described above, among the signal jitters that cause the identification error of the information reproduction signal, only the fluctuation of the pulse width particularly caused by the defocus is directly detected. The amount of defocus with respect to an arbitrary target value detected by the focus error correction means at the timing when the fluctuation amount of the pulse width obtained by the pulse width fluctuation detection device is minimized is transmitted as a focus error correction signal through the focus control circuit. Feedback is fed back to the objective lens actuator of the pickup, and the defocus is corrected.

In addition, the signal amplitude is determined based on the small fluctuation amount of the focus error detected from the focus error information by the focus error fluctuation detecting means so that the sum of the residual error of the optical disc and the periodic disturbance signal is always constant. The amplitude of the periodic signal generated by the periodic signal generating means is changed in synchronization with the rotation of the spindle motor.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pulse width fluctuation detecting apparatus according to an embodiment of the present invention and an in-focus position detecting apparatus using the same will be described below with reference to the drawings. FIG. 1 is a block diagram of a focus position detecting device according to a first embodiment of the present invention. In FIG. 1, an optical disk 1 as an optical disk medium, a spindle motor 10, an optical pickup 2, and a focus control circuit 3 as focus control means operate in the same manner as those shown in the conventional example (FIG. 13). 4 second as binarizing means
A binary circuit, a binary provided appropriate thresholds for the optical pickup 2 from the reproduction information reproduction signal (RF)
And reduction, RF pulse signal (P as binary pulse information signals
RF). Reference numeral 5 denotes a pulse width fluctuation detecting means as a pulse width fluctuation detecting device, and the RF pulse signal (P
It detects how thick or narrow the RF (RF) pulse width is relative to the pulse width of the reference signal, and outputs the amount as a pulse width fluctuation detection signal (PD). Reference numeral 6 denotes a minimum value detection circuit that detects a point that is the minimum value (minimum value) of the pulse width fluctuation detection signal (PD),
It emits a pulse signal.

The operation of the in-focus position searching device configured as described above will be described below with reference to FIGS. 1 and 2. First, the focus error signal (FE) output from the optical pickup 2 is fed back to the objective lens actuator of the optical pickup 2 via the focus control circuit 3. As a result, the distance between the focal point of the emitted laser beam and the information recording surface of the optical disk via the objective lens is kept substantially constant. However, at this time, the focal point of the emitted laser beam is not always exactly on the information recording surface of the optical disk. That is, there is an error (defocus) between the two.

FIG. 2 shows the waveform of the information reproduction signal (RF) and the waveform of the RF pulse signal (PRF) with respect to the defocus amount. When the focused laser beam of the optical pickup 2 scans information pits formed on the recording surface of the optical disk 1, an information reproduction signal (RF) as shown in FIG. Furthermore, the two potential (Vth) in threshold by the binarization circuit 4
The value is converted into an RF pulse signal (PRF). At this time, if there is no defocus, the pulse width of the RF pulse signal (PRF) has a predetermined length (T). This length (T) is
Generally, it corresponds to a reference cycle of a clock included in information recorded on the optical disc 1 or an integer multiple thereof. Here, when the defocus occurs, the information reproduction signal (R
The waveform of F) changes as shown in FIG. That is,
Since the focused laser spot on the recording surface of the optical disk 1 spreads, the detection resolution of information pits is reduced, and as a result, the information reproduction signal (RF) has a waveform as if it had passed through a low-pass filter. At this time, the information reproduction signal (RF)
Since the characteristic deteriorates sequentially from the harmonic components included in the components, the amplitude of the fundamental wave component does not decrease. However, as a result of the rounded waveform, the pulse width of the RF pulse signal (PRF) is shorter than a predetermined length (T). Further, when the amount of defocus increases, the characteristic degradation extends to the fundamental wave component, and a decrease in the amplitude is observed. Here, FIG. 2 shows an example in which an isolated pit mark is reproduced. However, when a plurality of pit marks are continuously formed, the RF pulse signal (PRF) may be thickened due to mutual interference.

In summary, when the defocus increases, the waveform of the information reproduction signal (RF) starts to deteriorate from its harmonic components, and the pulse width of the binarized signal changes first. When the wave component is reached, the amplitude decreases. Therefore, by observing the change in the pulse width, it is possible to detect the amount of defocus before observing the change in the amplitude. The detailed function of the apparatus for observing the pulse width, that is, the pulse width fluctuation detecting means 5 will be described as a pulse width fluctuation detecting apparatus from the fourth embodiment onward. Here, this defocus amount is minimized. A device for searching for a focal point will be described.

FIG. 3 shows a focus error signal (F) when a defocus amount, that is, a correction offset amount (.DELTA.FE) exists.
FIG. 5 illustrates a relationship between E) and a pulse width fluctuation detection signal (PD). As shown in FIG. 3A, generally, the focus error signal (FE) changes as shown in FIG. In the conventional example of FIG.
As a result, the distance between the focal point of the focused laser beam and the information recording surface of the optical disc 101 becomes constant. "However, in practice, a servo tracking residual is generated due to the influence of the surface deflection of the optical disc 1. Is controlled so that the average value of the distances between them becomes constant with periodic fluctuation. At this time, if the defocus (ΔFE) is constantly present, the focus position is closer to the one when the focus position is displaced to either one of the average values than to the average value. When the defocus amount (ΔFE) is larger than the periodic fluctuation width, that is, in the case of FIG.
The pulse width fluctuation detection signal (PD) is a focus error signal (FE)
Minimum at one peak. The minimum value detection circuit 6 detects the timing at which the pulse width fluctuation detection signal (PD) output from the pulse width fluctuation detecting means 5 becomes minimum.
Emit a pulse signal. The focus error correction circuit 7 as a focus error correction means at this timing outputs a focus error signal (FE).
Is sampled, and the defocus amount (ΔFE ₁ ) as a focus error correction signal at this time is added to the focus control circuit 3 as a correction offset amount. As a result, the defocus substantially becomes (ΔFE−ΔFE ₁ ) (FIG. 3B). At this time, assuming that the focus position falls within the periodic fluctuation, the pulse width fluctuation detection signal (PD) becomes minimum when the information recording surface of the optical disk 1 happens to cross the focus position as shown in FIG. Takes a value and changes to wrap around. If the focus error signal (FE) is sampled at this minimum value and added to the focus control circuit 3 as a correction offset amount (ΔFE ₂ ), the focal point position can be brought to the center of the periodic fluctuation (FIG. c)). At this time, the initial defocus amount (ΔFE) is corrected by the two degrees (ΔFE ₁ , ΔF
E ₂ ), that is, ΔFE = ΔFE ₁ + ΔFE ₂
Becomes Actually, in FIG. 3, (a) → (b) → (c)
In order for the process to proceed, a plurality of asymptotic processes are required. Further, in order to cope with a temporal change in the defocus amount (ΔFE), the cumulative focus error correction signal is given by ΔFE _i = ΔFE _i−1 It is better to always execute correction such as + ΔFE _x . Here, ΔFE _i−1 and ΔFE _i are (i−1) th (previous), i
It is the correction offset amount in the process of this time (this time),
ΔFE _x is a correction offset amount newly added in the current process.

As described above, according to the present embodiment, it is possible to detect the defocus with high sensitivity and further correct the focus to search for the in-focus position with high accuracy. In this embodiment, the in-focus position search is executed on the assumption that the focus error signal (FE) periodically fluctuates as shown in FIG. 3 with the focus servo applied. Does not always fluctuate periodically.

That is, when the optical disc 1 happens to have a very small surface runout, the focusing operation may not be performed correctly. Therefore, it is conceivable to forcibly add a disturbance signal to the focus control circuit 3 as shown in the conventional example.
In this case, if surface fluctuation is added to this, the fluctuation of the focal position becomes too large, which adversely affects the reproduction characteristics. Therefore, in the next embodiment, an apparatus for searching for a focal point while keeping the amount of change in the focal point constant irrespective of the magnitude of the surface shake will be described.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of an in-focus position searching device according to a second embodiment of the present invention. In FIG. 4, an optical disk 1, a spindle motor 10, and a focus control circuit 3 have the same functions as those described in the first embodiment. Reference numeral 40 denotes an RF as an information reproduction signal evaluation function detecting means.
Evaluation function detection means for outputting the degree of deterioration of the information reproduction signal (RF) with respect to the focus error as a unitary amount. For example, it comprises a binarizing circuit 4 and a pulse width fluctuation detecting means 5 of the first embodiment shown in FIG. Reference numeral 60 denotes an extremum detection circuit for detecting the minimal value (or maximal value) of the RF evaluation function. In the foregoing embodiment, the pulse signal is generated by detecting the minimum value of the pulse width fluctuation detection signal (PD). The focus error correction circuit 7 samples the focus error signal (FE) with the above-mentioned pulse in the same manner as in the first embodiment. In this embodiment, furthermore, a focus error fluctuation detecting circuit 81 as a focus error fluctuation detecting means, and a differential operation circuit (Xmax−
X) 82, periodic disturbance signal generation circuit 83 as periodic signal generation means, variable gain amplifier 84 as variable amplification means
have.

The operation of the in-focus position searching device of the second embodiment configured as described above will be described below. The focus error fluctuation detection circuit 81 detects and outputs the amplitude of the fluctuation of the focus error signal (FE) as the minute fluctuation amount of the focus error. For example, a circuit for sampling and holding the maximum value and the minimum value of the focus error signal (FE) is provided, and a circuit for calculating the difference between the two is provided. Let this output be X. The differential operation circuit 82 generates an output (Xmax-X) from this. Xmax is a constant value for determining the maximum value of the focal displacement as described later. The variable gain amplifier 84 includes a periodic disturbance signal generation circuit 83
The periodic disturbance signal (S) as the periodic signal of (Xmax−
X) is amplified at an amplification rate (gain) proportional to X) and added to the focus control circuit 3.

Here, if there is no surface deflection of the optical disk 1, X = 0, and the variable gain amplifier 84 amplifies the periodic disturbance signal (S) with the maximum gain Xmax. This becomes a forced disturbance signal and causes the objective lens actuator of the optical pickup 2 to swing. On the other hand, assuming that the optical disk 1 has a surface wobble and the focal displacement amount due to the surface wobble is Xmax, the gain of the variable gain amplifier 84 becomes 0 and no forced disturbance signal is applied. As a result, there is always a focal displacement of Xmax irrespective of the presence or absence of surface deflection, and the focus position search can be always performed.

The value of Xmax only needs to be such as not to affect the information reproduction characteristics, and is desirably about half or less of the focal depth of the focused laser beam emitted from the optical pickup 2. For example, when the laser wavelength (λ) is 800 nanometers (nm) and the beam NA is 0.5, the depth of focus is ± (λ / 2) · (NA) ² = ± 1.6μ.
m, Xmax ≦ 0.8 μm (μ
m).

Here, a case will be described in which the surface deflection of the optical disk 1 is extremely large, and the focus deviation amount exceeds Xmax. If the periodic disturbance signal (S) is generated at a period completely synchronized with the focal point deviation, the present embodiment operates to reduce the focal point displacement. That is, X> Xma
x, the gain of the periodic disturbance signal (S) is (Xmax
-X) <0, so that a signal having a phase opposite to that of the focus fluctuation is applied to the focus control circuit 3, and as a result, the focal displacement is canceled. In other words, the periodic disturbance signal (S) acts as a feedforward signal to reduce the focus control circuit 3. However,
If the phase of the focus fluctuation does not match the phase of the periodic disturbance signal (S), the focus displacement may be increased instead. Therefore, in the next embodiment, one device for matching the phases of both will be described.

Hereinafter, a third embodiment of the present invention will be described. FIG. 5 is a configuration diagram of a main part of a focal point position searching device according to a third embodiment of the present invention. In FIG. 5, reference numerals 81a and 81b denote focus error fluctuation detection circuits for detecting the orthogonal components of the fluctuation of the focus error signal (FE), that is, the amplitudes (X, Y) of the sin (sine) component and the cosin (cosine) component. I do. Reference numerals 82a and 82b denote differential operation circuits as differential operation means, which calculate (Xmax-X) and (Ymax-Y) for the amplitudes (X, Y) of both orthogonal components. 84a,
84b is a variable gain amplifier, (Xmax-X),
The two orthogonal components (Sx, Sy) of the periodic disturbance signal as the first and second periodic signals are amplified with a gain of (Ymax-Y). 83a and 83b are periodic disturbance signal generation circuits,
In synchronization with the rotation of the spindle motor 10, si
Periodic disturbance signal (Sx, Sy) of n component and cosin component
Generate Reference numeral 90 denotes an addition circuit, which adds the outputs of the variable gain amplifiers 84a and 84b as first and second variable amplifiers and supplies the result to the focus control circuit 3.

The operation of the in-focus position searching device configured as described above will be described below. First, the periodic disturbance signal generation circuits 83a and 83b respectively generate a periodic disturbance signal (Sx) of a sine wave component and a periodic disturbance signal (Sy) of a cosine wave component in synchronization with the spindle motor. As a specific configuration, for example, the waveform of the periodic disturbance signal (Sx, Sy) is recorded in advance in the ROM, and the rotational synchronization signal (FG) supplied from the spindle motor 10 is counted up by the ROM. Are sequentially read. Focus error fluctuation detection circuit 81
Reference numerals a and 81b decompose the fluctuation component of the focus error signal (FE) into the orthogonal components. Specifically, for example, the product of the focus error signal (FE) and each of the periodic disturbance signals (Sx, Sy) may be calculated. After amplifying the periodic disturbance signal (Sx, Sy) with a gain obtained by differentially processing the result and adding the amplified signal to the focus control circuit 3, the focus error signal is output at the amplitude of Xmax and Ymax for each orthogonal component. (F
E) can be displaced. Further, each orthogonal component of the focus error signal (FE) is a periodic disturbance signal (Sx,
Sy), the respective amplitude fluctuations are equal to Xmax
, Ymax, the periodic disturbance signals (Sx, Sy) act to cancel the respective excess components.

As described above, according to this embodiment, the displacement of the focus error signal (FE) and the phase of the periodic disturbance signal (Sx, Sy) can be adjusted, and as a result, as described in the previous embodiment. Such feedforward control can be reliably performed. In the second and third embodiments, R
Although the F evaluation function detecting means 40 has been described as having the same function as the pulse width fluctuation detecting means 5 shown in the first embodiment, this is the same as the information reproducing signal (RF) as shown in the conventional example. May be detected.

In the third embodiment, an example has been described in which an orthogonal component having a cycle of one rotation of the optical disc 1 is extracted from a change in the focus error signal (FE). Includes quadrature components twice or three times the period. Therefore, it is preferable to provide a focus error fluctuation detection circuit, a periodic disturbance signal generation circuit, a differential operation circuit, and a variable gain amplifier for these orthogonal components of the harmonic components.

The high-precision in-focus position searching apparatus using the pulse width fluctuation detecting means 5 has been described above.
A specific example of the pulse width fluctuation detecting device as the pulse width fluctuation detecting means 5 will be described. Hereinafter, a fourth embodiment of the present invention will be described. FIG. 6 is a block diagram of a pulse width fluctuation detecting device according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 501 denotes a phase comparison circuit as phase comparison means, which is an UP signal (UP) based on the advance or delay of the phase of an RF pulse signal (PRF) with respect to a reference clock signal (CLK) as a binary pulse reference signal. Alternatively, it outputs a DN signal (DN). 502 is a differential circuit, and 503 is an integrating circuit. Reference numeral 504 denotes a voltage controlled oscillator (VCO), which generates a reference clock signal (CLK) having a frequency corresponding to the output of the integrating circuit 503. 505 is an adding circuit,
Reference numeral 6 denotes a low-pass filter (LPF) whose output becomes a pulse width fluctuation detection signal (PD). Here,
Differential circuit 502, integrating circuit 503, and voltage controlled oscillator 5
04 together with feedback means.

The operation of the pulse width fluctuation detecting device configured as described above will be described below. Phase comparison circuit 501, differential circuit 502, integration circuit 503, VCO 50
4 constitutes a so-called PLL (Phase Lock Loop). First, an RF pulse signal (PRF) is input as a U signal (U) to a U terminal as a first input terminal of the phase comparison circuit 501, and a reference clock signal (CLK) is applied to a V terminal as a second input terminal. Input as signal (V). Based on the phase difference between the RF pulse signal (PRF) and the reference clock signal (CLK), the phase comparison circuit 501 outputs the UP signal (UP) from the UP terminal as the first output terminal and the second signal from the UP terminal as the first output terminal. A DN signal (DN) is output from a DN terminal as an output terminal of the respective devices as shown in FIG.

That is, when the RF pulse signal (PRF) is ahead of the reference clock signal (CLK) at the rising and falling edges (section A).
A pulse signal having a width corresponding to the advance
The signal is output from the UP terminal as a signal (UP). On the other hand, when the signal is delayed (section B), a pulse signal having a width corresponding to the delay is output from the DN terminal as a DN signal (DN). The phase advance / delay becomes a positive / negative pulse signal by the differential circuit 502 and further becomes a voltage signal cumulatively added by the integrating circuit 503. VCO 504 is
A clock signal having a frequency corresponding to this voltage value is generated as a reference clock signal (CLK) and fed back to the V terminal of the phase comparison circuit 501. As a result, the reference clock signal (CLK) is controlled such that the average of the phase difference with respect to the RF pulse signal (PRF) becomes zero.

At this time, if there is no fluctuation in the pulse width, no pulse signal (phase difference) appears as an output from the UP terminal and the DN terminal as a result of the feedback. Here, if the RF pulse signal (PRF) has a pulse width smaller than the reference clock signal (CLK) (section C), first, the DN signal (DN) is supplied to the DN terminal at the rising edge, and the UP signal is supplied at the falling edge. (UP) is output to the UP terminal as a phase difference pulse. Also, R
The F pulse signal (PRF) is a reference clock signal (CLK)
If it is wider (section D), the UP signal (UP) is output as a phase difference pulse to the UP terminal at the rising edge, and the DN signal (DN) is output to the DN terminal at the falling edge.

As described above, since the frequency and phase of the reference clock signal (CLK) are controlled by the PLL so that the average of the phase difference between the two inputs becomes zero, the width fluctuation of the RF pulse signal (PRF) is controlled. If there is, UP terminal, D
The UP signal (U) having the same width as the output to the N terminal
P) and the DN signal (DN) are output. Accordingly, as a result, the RF pulse signal (P
RF), only the fluctuation component of the pulse width is output.
A smoothed DC voltage is output from the low-pass filter 506 as a pulse width fluctuation detection signal (PD).

In this embodiment, the phase comparison circuit 5
The configuration of 01 is not particularly limited as long as it has the above-mentioned functions. For example, as shown in FIG. 7, the rising edge and the falling edge of the RF pulse signal (PRF) are detected by mono-multi, respectively, and the earlier signal of the edge signal and the edge of the reference clock signal (CLK) is detected. One is to set a flip-flop at the edge and reset it later. As a result, the signal having each terminal for outputting the value obtained by adding the UP signal (UP) from the UP terminal and the DN signal (DN) from the DN terminal and performing the differential operation, that is, the added signal ( The output terminal may have an addition terminal ((UP + DN) terminal) that outputs UP + DN and a differential terminal ((UP-DN) terminal) that outputs a differential signal (UP-DN). Output addition signal (UP + DN) (UP
+ DN) terminal can be directly realized by, for example, an exclusive OR operation (exclusive OR). However, with a relatively simple configuration, the addition signal (UP + D
N) and the differential signal (UP-DN), it is better to output the UP signal (UP) from the UP terminal and the DN signal (DN) from the DN terminal independently. . Another example of the phase comparison circuit 501 will be described in the following embodiment.

Hereinafter, a fifth embodiment of the present invention will be described. FIG. 9 is a state transition diagram of the phase comparison circuit according to the fifth embodiment of the present invention. In FIG. 9, a, b, c, d, e, f
Is a node representing a state. Numerical values in the figure mean U: V signal (U: V) / UP: DN signal (UP: DN). The operation of the state transition diagram will be described by taking the section A in FIG. 8 as an example. State a is a U, V signal (U, V
V) are both 0, that is, L (representing a low level). Nothing is output at this time. Here, when the RF pulse signal (PRF) as the U signal (U) rises first, the UP signal (UP) becomes 1, that is, H (Hig)
h (representing the h level) ((U: V) / (UP: DN)
= 10/10), and transits to the state b. Next, when the reference clock signal (CLK) as the V signal (V) rises, the UP signal (UP) becomes 0 ((U: V) / (U
P: DN) = 11: 00), and transits to the state d. State b
During this period, the UP signal (UP) becomes 1, which means that a phase advance pulse at the rising edge is issued. State c means that a phase-lag pulse is issued, and states e and f mean that a phase advance and a phase-lag pulse are emitted at the falling edge, respectively.

If the logic circuit for realizing the above state transition diagram is designed, the operation shown in FIG. 8 can be realized. First, as shown in FIG. 10, the state of a to f is changed to 3 bits (S1: S
2: S3), and as shown below, the lower two bits (S2: S3) as output UP and DN signals (U
(P, DN), the circuit can be simplified. From FIG. 10, the logical expression for realizing the above state transition is as follows: S1 = U · S1 + V · S1 + U · V ·! S1 S2 = U ・! V! S1 +! U ・ V ・ S1 S3 =! U ・ V ・! S1 + U.! V · S1.

At this time, the UP and DN signals (UP and DN)
May be: UP = S2 DN = S3 As shown in FIG. 7, the feature of this embodiment is that it does not require the detection of rising and falling edges using a mono-multi, and is realized by a relatively simple circuit configuration using only a simple logic circuit as a logic element group. What you can do.

As described above, according to this embodiment, a phase comparison circuit can be realized with a simple configuration. Hereinafter, a sixth embodiment of the present invention will be described. FIG. 11 is a block diagram of a pulse width fluctuation detecting device according to a sixth embodiment of the present invention. In FIG. 11, a differential circuit 502, an integrating circuit 50
3. The addition circuit 505 and the low-pass filter 506 operate in the same manner as that shown in FIG. Reference numeral 510 denotes a clock extraction circuit as clock extraction means, which extracts a reference clock signal (CLK) as a clock signal from the RF pulse signal (PRF). 512 is D as latch means.
It is a flip-flop (acting as a latch) that determines the rising and falling edges of the RF pulse signal (PRF) at the edge of the reference clock signal (CLK). 5
Reference numeral 13 denotes a variable delay circuit serving as a variable delay unit, and an RF pulse signal (PR) is provided in accordance with the output potential of the integration circuit 503.
F) is delayed. Further the phase comparator circuit 514, FIG. 7
It is shown by.

The operation of the pulse width fluctuation detecting device configured as described above will be described. First, the configuration as shown in FIG.
The phase comparison circuit 514 detects the edges of the two input signals (U, V) and compares them .
The periods of the two input signals (U, V) must be exactly the same ( during PLL operation). But in general,
The RF pulse signal (PRF) is modulated and includes a period that is an integral multiple of the basic period. On the other hand , the reference clock signal (CLK) has only the basic period. In such a case , if a PLL having an exclusive-OR type phase comparison circuit is used as the clock extraction circuit 510 , the reference clock signal (CLK) is synchronized with the fundamental period component of the RF pulse signal (PRF). be able to.
However, this type of clock extraction circuit 510 does not essentially output the rising and falling edges, but separates the leading and lagging phases into two outputs as in the phase comparison circuit of FIG. Can not do it. Therefore, the clock extraction circuit 510 cannot detect a pulse width variation. Therefore, in the present embodiment, as described above, the clock signal circuit 5 that extracts the reference clock signal (CLK) from the RF pulse signal (PRF)
10, ie, a clock signal extraction function by a PLL and a pulse width fluctuation detection function by a phase comparison circuit 514 configured as shown in FIG.

The clock extraction circuit 510 comprises a phase comparison circuit as an exclusive OR type phase comparison section, an integration circuit as a loop filter, and a phase locked loop (PLL) having a VCO, and an RF pulse signal (PR
The VCO output is synchronized with F), and this is output as a reference clock signal (CLK). Since the rising and falling edges of the RF pulse signal (PRF) passing through the D flip-flop 512 are all given by the reference clock signal (CLK), the reference signal has no pulse width variation. However, since the phase is delayed by about half a clock with respect to the signal before the input, it is necessary to delay the PRF signal and make the phases of the two signals uniform. It is conceivable to use a fixed delay line as a means for this delay, but an RF pulse signal (PRF)
, The phase error occurs between the output signal of the D flip-flop 512 and the output signal of the delay line, which may be erroneously detected as a pulse width variation. Therefore, in this embodiment, this phase error is detected by the phase comparison circuit 514, and this is fed back to the delay amount control terminal of the variable delay circuit 513 via the integration circuit 503 and absorbed. The above situation is shown in FIG.

As described above, according to the present embodiment, the modulated RF pulse signal (PR
A pulse width fluctuation detection signal (PD) is obtained from F), and the pulse width fluctuation amount can be detected. In this embodiment, the case where the phase difference between the RF pulse signal (PRF) and its latch signal is automatically corrected has been described. However, as described above, the phase difference may be corrected using a fixed delay line. . In this case, the addition signal (U
Since only (P + DN) is required, an exclusive OR circuit can be used instead, and the circuit is simplified.

[0039]

As described above, according to the present invention, when the out-of-focus of the emitted laser beam occurs with respect to the information recording surface of the optical disk medium, the waveform of the information reproduction signal reproduced from the optical pickup becomes round. Dread. Based on this waveform, binarizing means for outputting a binary pulse information signal whose pulse width is changed. On the basis of the binary pulse information signal, the pulse width variation detection device outputs an electric signal corresponding to the variation of the binary pulse information signal with respect to the reference pulse width. As described above, among the signal jitters that cause the identification error of the information reproduction signal, only the fluctuation of the pulse width particularly caused by the defocus is directly and accurately detected. The amount of defocus with respect to an arbitrary target value detected by the focus error correction means at the timing when the fluctuation amount of the pulse width obtained by the pulse width fluctuation detection device is minimized is transmitted as a focus error correction signal through the focus control circuit. Feedback is fed back to the objective lens actuator of the pickup, so that defocus can be corrected. Therefore, the in-focus position can be detected with high sensitivity, the defocus can be detected sensitively, and the in-focus position can be detected with high accuracy and stability.

Further, the amplification factor of the variable amplifying means is adjusted so that the sum of the surface deflection residual of the optical disc and the periodic signal is always constant. And the amplitude of the periodic signal generated by the periodic signal generating means can be changed in synchronization with the rotation of the spindle motor. For this reason, it is possible to suppress the focus fluctuation at the time of searching for the focal point.

[Brief description of the drawings]

FIG. 1 is a block diagram of an in-focus position searching device according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of an operation with respect to defocus in the embodiment.

FIG. 3 is an explanatory diagram of an operation during one rotation at the time of defocus in the embodiment.

FIG. 4 is a block diagram of an in-focus position searching device according to a second embodiment of the present invention;

FIG. 5 is a block diagram of a main part of a focus position detecting device according to a third embodiment of the present invention;

FIG. 6 is a block diagram of a pulse width fluctuation detecting device according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram illustrating an example of a phase comparison circuit according to the embodiment;

FIG. 8 is a timing chart for explaining the operation of the phase comparison circuit of the embodiment.

FIG. 9 is a state transition diagram of the phase comparison circuit according to the fifth embodiment of the present invention.

FIG. 10 is a diagram showing correspondences with logical values of the phase comparison circuit of the embodiment.

FIG. 11 is a block diagram of a pulse width fluctuation detecting device according to a sixth embodiment of the present invention.

FIG. 12 is a timing chart for explaining the operation of the embodiment.

FIG. 13 is a schematic configuration diagram of a conventional in-focus position searching device.

[Explanation of symbols]

4 Binarization circuit 5 Pulse width fluctuation detection means 7 Focus error correction circuit 40 RF evaluation function detection means 81 Focus error fluctuation detection circuit 83 Periodic disturbance signal generation circuit 84 Variable gain amplifier 501 Phase comparison circuit 502 Differential circuit 503 Integration circuit 504 Voltage controlled oscillator (VCO) 506 Low-pass filter 510 Clock extraction circuit 512 D flip-flop 513 Variable delay circuit

Claims (11)

(57) [Claims] 1. A pulse width variation detector for outputting a variation in the pulse width based on the information signal reproduced Ri by <br/> from the optical disk medium in an optical pickup as detected <br/> electrical signal, said The information signal is used as the first input signal and the reference signal is used as the second input signal.
And the second input of the first input signal
Phase comparing means for detecting a phase difference and delay phase difference lead of signals, and means for feedback control of the frequency and phase of the advanced phase difference and the delay phase difference mean value said reference signal so as to zero the difference, before Symbol proceeds by adding the phase difference and delay phase difference, the pulse width variation detecting apparatus characterized by the ingredients Bei and means for outputting the low frequency component as the pulse width variation detection signal. 2. A pulse width fluctuation detecting device which detects a fluctuation in a pulse width based on an information signal reproduced from an optical disk medium by an optical pickup and outputs the fluctuation as an electric signal, Clock extracting means for synchronously extracting a clock signal from an information signal, variable delay means for delaying the information signal by an arbitrary period, and a latch for determining and outputting the information signal at the rising or falling edge of the clock signal Means and an output signal from said variable delay means
As a first input signal and an output signal from the latch means
A second input signal, and the second input signal
Add the leading phase difference and the lagging phase difference for the input signal ,
Pulse width variation detecting apparatus characterized by comprising a means for outputting the low frequency component as the pulse width variation detection signal. 3. A lead phase difference and a lag position generated by an exclusive OR operation of a first input signal and a second input signal.
3. The pulse width fluctuation detection device according to claim 1 , wherein the pulse width fluctuation detection device is configured to add the phase difference and output a low-frequency component thereof as a pulse width fluctuation detection signal. 4. An information signal is supplied to the phase comparing means.
A first input terminal and a second input terminal to which a reference signal is supplied
Have the door, the information signal supplied to the first input terminal and U, the reference signal supplied to the second input terminal V
S1 = U ＝ S1 + VS ・ 1 ＋ UV ・! S1 S2 = U ・! V! S1 +! U ・ V ・ S1 S3 =! U ・ V ・! S1 + U.! A logic element group combined to output a signal corresponding to S1, S2, and S3 by executing a logical operation of V · S1; outputting a signal corresponding to S2 as a phase difference; The pulse width fluctuation detecting device according to claim 1, wherein a signal corresponding to the pulse width variation is output as a delay phase difference. 5. A clock extracting means comprising: a phase comparator of an exclusive OR operation type; a loop filter composed of an integration circuit; and a voltage controlled oscillation circuit for controlling an oscillation frequency by a voltage.
3. The pulse width fluctuation detecting device according to claim 2, wherein the pulse width fluctuation detecting device is formed by forming a phase locked loop . 6. A focal point position detecting device comprising the pulse width fluctuation detecting device according to claim 1 as pulse width fluctuation detecting means, wherein the pulse width fluctuation detecting means comprises an optical signal.
An optical disc from the light-emitting element of the pickup via the objective lens
Optical disc by a laser beam applied to the
Optical pickup by scanning the information recording surface of the optical recording medium
Obtained from the information reproduction signal output from the light receiving element
Of the pulse width of the value pulse information signal from a predetermined pulse width
Variations, configured to output as an electric signal, the amount of change of the focus control means and, before Symbol pulse width controlled to an arbitrary target value the distance between the focus and the optical disc medium of the objective lens has the minimum value focus position locator and the distance to and a focus error correction means for supplying to said focus control means as the target value between the focus and the optical disc medium of the objective lens when. 7. A focal point position detecting device comprising the pulse width fluctuation detecting device according to claim 1 or 2 as pulse width fluctuation detecting means, wherein the pulse width fluctuation detecting means comprises an optical signal.
An optical disc from the light-emitting element of the pickup via the objective lens
Optical disc by a laser beam applied to the
Optical pickup by scanning the information recording surface of the optical recording medium
Obtained from the information reproduction signal output from the light receiving element
Of the pulse width of the value pulse information signal from a predetermined pulse width
Variations, configured to output as an electric signal, the amount of change of the focus control means and, before Symbol pulse width controlled to an arbitrary target value the distance between the focus and the optical disc medium of the objective lens has the minimum value wherein a focus error correction means for supplying to said focus control means the distance between the focus and the optical disc medium of the objective lens as the target value, focus of the objective lens when
Distance between the point and the optical disk medium and the
A focus error change detecting means for detecting a difference between the focus error information and a target value as a focus error information, and detecting a minute change amount of a focus error of the focus error information in one rotation cycle of the spindle motor on which the optical disk medium is mounted; focus position locator, characterized in that the amount of slight change is provided with means for supplying to said focus control means a disturbance signal having the rotational period so as not to exceed a predetermined range. 8. A focus error correction means, configured to update the target value by cumulatively focus error correction value, i
The set to two or more integer, the (i-1) times the cumulative focus error correction signal being applied to the already focus control means in exploration until th and ΔFE _i-1, the focus error obtained in the i-th search when the correction signal is a ΔFE _x, a new _{ΔFE i = ΔFE i-1 +} ΔFE x as the i-th cumulative focus error correction signal
The in- focus position searching device according to claim 6 or 7, wherein the apparatus is configured to supply the target value to the focus control unit. 9. A depth of focus determined based on the objective lens and a wavelength of light emitted from a light emitting element, the predetermined range of a minute variation with respect to a target value of a distance between a focus of the objective lens and an optical disk medium. The in-focus position detecting device according to claim 7, wherein the value is not more than half. 10. A focus error fluctuation detecting means configured to detect a minute fluctuation amount with respect to a target value of a distance between a focal point of an objective lens and an optical disk medium.
When a predetermined value is set to Xmax, a differential operation unit for calculating (Xmax−X) for the minute fluctuation amount is provided, and a disturbance signal amplitude is determined based on an output of the differential operation unit. The in-focus position searching device according to claim 9 , configured as described above. As 11. periodic disturbance signal, configured to generate the first and second periodic disturbance signal are orthogonal to each other
With the focus error variation detection means, the less of the minute fluctuation amount with respect to the target value of the distance between the focus and the optical disc medium of the objective lens is decomposed into the two orthogonal components
Even one, then the amplitude of the first periodic disturbance signal and in-phase component, and configured to detect the other as an amplitude of the second period disturbance signal and in-phase component, the first periodic disturbance signal and in-phase component When the amplitude is X, the amplitude of the in-phase component with the second periodic disturbance signal is Y, and the predetermined values of the respective quadrature components are Xmax and Ymax, (Xmax−X ), (Ymax-
Y), and supplies the first periodic disturbance signal with an amplitude corresponding to (Xmax−X).
The in-focus position searching device according to claim 9 , wherein the second periodic disturbance signal is supplied with an amplitude corresponding to (Ymax-Y).