JPH02108244A - Optical information reproducing device - Google Patents

Abstract

PURPOSE:To stabilize a tracking control by detecting a phase difference between outputs of one pair of diagonal cells of a four-divided photoelectric detector as divided in a track moving direction and its vertical direction, delaying the output of a cell which is advanced in phase and adding this to the other output. CONSTITUTION:The photoelectric detector 11 is divided into four sections by the dividing lines 11a and 11b in the information track moving direction R2 and the vertical direction to this. When a phase depth of a bit formed on a recording medium is shifted from a multiple of integer of lambda/4, a phase difference is generated in the R2 direction by a far-field pattern formed on the detector 11 even at the time of focusing. Output signals of the cells C and D are further advanced in phase than output signals of the cells A and B. These phase difference are detected by adders AD1 and AD2, and the output signals of the cells C and D are delayed via a control means (delay amt. controller) 12, and then they are added to the output signals of the cells A and B by adders AD3 and AD4 respectively. These output signals are passed through waveform shaping means 14a and 14b respectively and then compared to each other in phase by a phase comparing means 15 to generate a tracking error signal to be outputted via an LPF 16.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides optical information processing from a recording medium, such as an optical disk, on which pit rows representing information are formed. The present invention relates to an optical information reproducing device that reads (2), and more specifically relates to its tracking control.

[Conventional technology]

In recent years, optical information reproducing devices such as video disc reproducing devices and digital audio disc reproducing devices that optically read information from a recording medium such as an optical disc on which a bit string representing information is formed have been widely used. Information is recorded on information tracks with a minute width on the recording medium, and in order to reproduce the information from there, precise tracking control is generally required. In order to perform tracking control, it is necessary to detect tracking errors, and this is usually done optically. A method of detecting a tracking error from a phase difference of signals (hereinafter referred to as a "phase difference method") is already known.

FIG. 3 shows a basic configuration for detecting a tracking error using the phase difference method in an optical information reproducing apparatus. In the figure, ■ is a photoelectric detector, 3
a and 3b are addition means, 4a and 4b are waveform shaping means, 5 is phase comparison means, and 6 is a low-pass filter.

The operation of the above configuration will be explained below.

In FIG. 3, the direction of extension of the map of the information track created when light incident from a semiconductor laser light source (not shown) is reflected on the surface of the recording medium and the reflected light is projected onto the surface of the photoelectric detector 1 is indicated by an arrow R1. In the following, it will be referred to as "extending direction R1." As shown in the figure, the photoelectric detector 1 is divided into four parts A, B, C, and D by a dividing line 1a that is approximately parallel to the extending direction R1 and a dividing line 1b that is approximately perpendicular to the extending direction R1.
It is divided into two light receiving cells. Adding means 3a outputs a sum signal obtained by adding output signals from two light receiving cells A and C arranged diagonally, and adding means 3b outputs a sum signal obtained by adding output signals from two light receiving cells A and C arranged diagonally, and adding means 3b outputs a sum signal obtained by adding output signals from two light receiving cells A and C arranged diagonally. A sum signal obtained by adding the output signals from the BD is output.

When there is no tracking error, there is no phase difference between these sum signals, but when a tracking error occurs, a phase difference occurs between them. Therefore, adding means 3a and 3
Waveform shaping means 4a and 4b respectively output the output signals from b.
After shaping the waveforms, a phase comparing means 5 compares the phases of these waves, and a low-pass filter 6 removes the ripple component from the output, thereby obtaining a tracking error signal (such prior art is, for example, a special technique). Publication No. 52-93222 and JP-A No. 57-1
It is disclosed in Japanese Patent No. 81433. ).

[Problem to be solved by the invention]

However, in the above configuration, when the phase depth of the bit formed on the recording medium deviates from an integral multiple of a quarter wavelength, the far field on the photoelectric detector I is used for tracking control, etc. When the image moves in a direction perpendicular to the extending direction R1, the offset value of the tracking error detection signal fluctuates, causing a problem that tracking control becomes unstable.

This is due to the following reasons. Two light receiving cells A arranged on one side with respect to the dividing line 1b perpendicular to the extending direction R1
, DC or B, C) and the two light receiving cells B, C (or AD) arranged on the other side, the phase difference of the output signal is determined by the focus state of the light spot converged on the recording medium. It changes depending on. Such a phase difference will hereinafter be referred to as a "focus phase difference." When the phase depth of the bit formed on the recording medium is an integral multiple of a quarter wavelength, the focus phase difference becomes zero when focusing, and when dayfocusing, the phase difference changes depending on the direction and dayfocus amount. occurs.

On the other hand, if the phase depth of the bit deviates from an integral multiple of a quarter wavelength, the focus phase difference will not be zero even during focusing. That is, an offset occurs in the focus phase difference. The sign and magnitude of the offset of this focus phase difference change depending on the direction and magnitude of the shift in focus phase depth. When the far-field image is formed symmetrically with respect to the dividing line 1a that is substantially parallel to the extending direction R1, the phase difference between the phase signals of the light-receiving cells A, C, B, and D arranged diagonally is At the time of detection, the focus phase difference is canceled and does not become an offset of the tracking error signal. However, if the far-field image formed on the photoelectric detector l is displaced asymmetrically with respect to the dividing line 1a, then the light-receiving cells A, CiB, D arranged diagonally
When detecting the phase difference between each phase signal, the focus phase difference is not canceled out, and when a tracking error signal is detected from the phase difference between the phase signals, this focus phase difference becomes an offset of the tracking error signal.

Moreover, if the phase depth of focus deviates from an integer multiple of a quarter wavelength to a shallower direction, the direction of the offset will change when the objective lens is displaced by tracking control to follow the eccentricity of the recording medium, etc. In addition, when the tracking control is lost and the object crosses the track with the objective lens eccentric, a driving force is generated that further eccentricizes the objective lens, and in some cases, the tracking control goes out of control. Sometimes.

On the other hand, if the phase depth of the bit deviates from an integer multiple of a quarter wavelength in a deeper direction, the offset of the tracking error signal that occurs when the far-field image is displaced is opposite to that in the above case. In this case, the above-mentioned disadvantages are small, but if the amount of offset of the tracking error signal increases, the tracking control becomes inaccurate, which causes disadvantages.

It is an object of the present invention to provide an optical information reproducing device that solves the above-mentioned technical problems and allows tracking control to be performed in a much more stable manner.

[Means to solve the problem]

In the optical information reproducing device of the present invention, an information track of a recording medium on which a pit row representing information is formed is divided by a dividing line substantially parallel to the extending direction of the mapping and a dividing line substantially perpendicular to the extending direction. a photoelectric detector having four light-receiving cells arranged in the same direction, and forming a far-field image of a light spot converged on the recording medium across the four light-receiving cells; and a dividing line substantially perpendicular to the extending direction. a first adding means for adding output signals from two light-receiving cells arranged on one side with respect to the direction of extension; A first delay means and a second delay means are each configured with an all-pass filter that receives each output signal, delays and outputs the output signal, and whose delay amount is variable; a second addition means for adding the output signals from the delay means; output signals from the first and second addition means are provided;
delay amount control means for detecting these phase differences and outputting a delay amount control signal in the direction of canceling the phase difference to the first and second delay means; and an output signal of the first delay means; The third delay means adds the output signal from the light receiving cell arranged diagonally to the light receiving cell corresponding to the first delay means.
and a fourth addition for adding the output signal of the second delay means and the output signal from the light receiving cell disposed at a diagonal position of the light receiving cell corresponding to the second delay means. and tracking error detection means for detecting a tracking error from the phase difference between the output signal of the third addition means and the output signal of the fourth addition means and outputting a trunking error signal. be.

[For production]

According to the configuration of the present invention, the photoelectric detector that forms a far-field image of a converged light spot on a recording medium is substantially perpendicular to a dividing line that is substantially parallel to the extending direction of the mapping of the information track of the recording medium. It has four light receiving cells divided by a dividing line. Among the output signals from these four light-receiving cells, the outputs from the two light-receiving cells arranged on one side of the dividing line substantially perpendicular to the extending direction are added by the first adding means, and the outputs are added to the other side. Each output signal from the two light-receiving cells provided is input to first and second delay means each comprising an all-pass filter.

The delay amounts of the first and second delay means are changed by a delay amount control signal from the delay amount control means.

The delay amount control means is supplied with the output signal of the second addition means for outputting a sum signal of the output signals of the first and twentieth delay means, and the output signal of the first addition means, and The delay amount control signal in the direction of canceling the phase difference is the first delay amount control signal.
and a second delay means. In this way,
The focus phase difference mentioned above is canceled out.

The tracking error detection means includes a third addition means for adding an output signal of the first delay means and an output signal from a light receiving cell at a diagonal position of the light receiving cell corresponding to the first delay means; The output signal of the second delay means and this second delay means
A tracking error is detected from the phase difference between the respective output signals from the fourth adding means that adds the output signals from the light receiving cells at diagonal positions of the light receiving cells corresponding to the delay means. That is, the tracking error is detected after the focus phase difference is canceled out. by this,
Even if the phase precision of the focus formed on the recording medium varies, tracking control can be performed stably without causing fluctuations in the offset of the tracking error signal.

Since the first and second delay means are composed of all-pass filters, the frequency characteristics do not deteriorate, and the tracking error detection means and delay amount control means to which these outputs are input can stably operate. be able to.

[Embodiment] FIG. 1 is a block diagram showing the basic configuration of a portion related to tracking control of an optical information reproducing apparatus according to an embodiment of the present invention. This optical information reproducing device optically reads and reproduces information from a recording medium (not shown) such as an optical disk on which a bit string representing information has been formed, and is divided into four parts by orthogonal dividing lines 11a and llb. It is equipped with a photoelectric detector 11 divided into cells A, BC, and D.

The direction in which the information track of the recording medium in this photoelectric detector 11 extends is indicated by an arrow R2, and hereinafter referred to as [extension direction R2J, etc.]. The dividing lines 11a, l
lb is approximately parallel and approximately perpendicular to this extending direction R2, respectively. A far-field image of the light spot converged on the recording medium is formed across the four light receiving cells A, B, C, and D. This optical information reproducing device further includes a first adding means ADI for adding the output signals from the two light receiving cells A and B arranged on one side with respect to the dividing line 11b substantially perpendicular to the extending direction R2; The dividing line 11
A first delay means which is given output signals from two light receiving cells C and D arranged on the other side with respect to b, delays the output signals and outputs them, and whose delay amount is variable;
P01 delay means DL2 and the first and second delay means DL1. A second addition means AD2 that adds the output signals from DL2, and first and second addition means AD1. AD2
Given the output signals from , detect these phase differences,
The delay amount control signal in the direction of canceling this phase difference is transmitted to the first
and a delay amount control means 12 that outputs to the second delay means, an output signal of the first delay means DLI, and a light receiving cell disposed at a diagonal position of the light receiving cell C corresponding to the first delay means. A third adding means AD3 adds the output signal from the cell A, the output signal of the second delay means DL2, and the diagonal position (distribution) of the light receiving cell D corresponding to the second delay means DL2. a fourth addition means AD4 for adding the output signal from the light receiving cell B provided therein; and the third addition means AD3.
and a tracking error detection means 13 that detects a tracking error from the phase difference between the output signal of AD4 and the output signal of the fourth addition means AD4, and outputs a tracking error signal. A preamplifier 18 amplifies the read signal from the photoelectric detector 11 to create an RF multiplied signal, and obtains the read signal from a change in the current injected into the common substrate (not shown) of the photoelectric detector 11. There is.

The tracking error detection means 13 includes the third and fourth
Adding means AD3. Waveform shaping means 14a, 14b to which the output signals of the AD4 are respectively input, phase comparison means 15 to which the outputs of the waveform shaping means 14a, 14b are commonly inputted and detecting the phase difference between them, and this phase comparison means. The low-pass filter 16 removes ripple components from the I5 output to obtain a tracking error signal.

FIG. 2 shows the first and second delay means DL 1°DL.
2, and third and fourth addition means ^D3. It is an electric circuit diagram showing an example of a concrete composition with AD4.

The third adding means AD3 includes an operational amplifier 22a whose output signal is fed back to an inverting input terminal via a resistor 21a, and an output signal from the light receiving cell A is fed back to the inverting input terminal of the operational amplifier 22a through a resistor 23a. given through.

The first delay means DLL includes a resistor 24a connected between the inverting input terminal of the operational amplifier 22a and the light receiving cell C, and a terminal of the resistor 24a on the light receiving cell C side and the operational amplifier 2.
A variable capacitor 25a connected between the variable capacitor 25a and the non-inverting input terminal of the variable capacitor 25a, and a resistor 2 having one end connected to the terminal on the non-inverting input terminal side of the variable capacitor 25a and the other end grounded.
6a, constituting an all-pass filter. The variation in the amount of delay in the first delay means DLI is realized by changing the capacitance of the variable capacitor 25a in accordance with a delay amount control signal given from the delay amount control means 12 (see FIG. 1).

The configuration regarding the fourth addition means 404 and the second delay means OL2 is similar to the configuration regarding the third addition means AD3 and the first delay means DI, I, and corresponding parts have the same numerals and suffixes. Shown with a .

Regarding the optical information reproducing device configured as described above,
The operation will be explained below.

When the phase depth of the pit formed on the recording medium deviates from an integer multiple of a quarter wavelength, the far-field image formed on the photoelectric detector ll will be located above and below that of Fig. 1 even when focused. The brightness changes as it moves in the direction (that is, the extending direction R2). That is, an offset of the focus phase difference occurs. Here, for example, it is assumed that the output signals from the light receiving cells C and D lead the output signals from the light receiving cells A and B in phase. The first delay means DLI and the second delay means DL2 delay the output signals from the light receiving cells C and D so as to cancel out the offset of these focus phase differences.

After the output signals from the light receiving cells C and D are delayed in this way, the third adding means AD3 adds the output signals of the light receiving cells A and C, and the fourth adding means AD4 adds the output signals from the light receiving cells B and D. Add signals. A tracking error signal can be obtained by shaping the output signals from the third adding means AD3 and the fourth adding means AD4 by the waveform shaping means 14a and 14b, respectively, and by comparing the phases with the phase comparing means 15.

In this way, the far-field image on the photoelectric detector 11 becomes the first
Moving in the left-right direction of the figure, that is, in the direction intersecting the extending direction R2, the output signal from one of the two light-receiving cells becomes larger than the output signal from the other two light-receiving cells with respect to the dividing line 11a. However, since the offset of the focus phase difference is substantially canceled, the waveform shaping means 1 is used to offset the tracking error signal.
4a.

The output from 14b (the phase difference between No. 8 disappears).

Furthermore, as described above, the first and second delay means DLI
, DL2 is composed of an all-pass filter, so
It is possible to stably operate the delay amount control means 12 and the tracking error detection means 13 without deteriorating the frequency characteristics.

Next, the above-mentioned first and second delay means DL 1°DL
The signal delay in 2 will be explained. If the phase difference between the output signal from the first addition means ADI and the output signal from the second addition means AD2 is not zero, this phase difference becomes an offset of the tracking error signal; In this case, the offset of the tracking error signal disappears. The delay amount control means 12 outputs a delay amount control signal to the first delay means DLI and the second delay means DL2 according to this phase difference, and adjusts the delay amount so as to completely cancel out the focus phase difference. In this way, even if the phase depth of the bits on the recording medium changes and the offset of the focus phase difference changes, tracking control can always be performed stably.

That is, even if the far-field image of the light spot on the photoelectric detector 11 moves in a direction perpendicular to the extending direction R2 of the information track mapping due to movement of an objective lens (not shown) for tracking control, etc. Since the offset of the track tracking control signal never fluctuates and the tracking control is not performed stably, the tracking control is much more stable.

〔Effect of the invention〕

According to the optical information reproducing device of the present invention, the output signals of the two light receiving cells arranged on one side with respect to the dividing line substantially perpendicular to the extending direction of the mapping of the information track of the photoelectric detector are added to the first adding means. After each output signal of the two light receiving cells arranged on the other side is delayed by the first and second delay means respectively constituted by all-pass filters, the output signal is manually input to the second addition means, and The phase difference is detected from the outputs of the first and second adding means by one stage of delay amount control, and the phase difference is
The delay amount control signal in the direction of zero is applied to the first and second delay means, so that the difference in focus position is canceled by 1. Tracking error is detected in this manner, and the focus phase difference is canceled out. Therefore, even if the phase depth of the bits formed on the recording medium varies, the offset of the tracking error signal can be varied. Become.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the parts related to tracking and node control of an optical information recirculation device according to an embodiment of the present invention, and FIG. 1
and second delay means DL I.

Claims (1)

[Scope of Claims] Four partitions divided by a dividing line substantially parallel to the extending direction of the mapping of the information track of the recording medium on which the pit row representing information is formed and a dividing line substantially perpendicular to the extending direction. a photoelectric detector having a light receiving cell and forming a far-field image of a converged light spot on the recording medium across the four light receiving cells; a first adding means for adding the output signals from the two light receiving cells arranged; and a first adding means for adding the output signals from the two light receiving cells arranged on the other side with respect to the dividing line substantially perpendicular to the extending direction; a first delay means and a second delay means configured of all-pass filters that delay and output the given output signal and whose delay amount is variable; a second addition means for adding the output signals; and output signals from the first and second addition means are provided;
delay amount control means for detecting these phase differences and outputting a delay amount control signal in the direction of canceling the phase difference to the first and second delay means; and an output signal of the first delay means; The third delay means adds the output signal from the light receiving cell arranged diagonally to the light receiving cell corresponding to the first delay means.
and a fourth addition for adding the output signal of the second delay means and the output signal from the light receiving cell disposed at a diagonal position of the light receiving cell corresponding to the second delay means. and tracking error detection means for detecting a tracking error from the phase difference between the output signal of the third addition means and the output signal of the fourth addition means and outputting a tracking error signal. playback device.