JP2751480B2 - Optical information reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reproducing apparatus for optically reading information from a recording medium, and more particularly to a tracking control signal detecting apparatus.

2. Description of the Related Art In recent years, an optical information reproducing apparatus that optically reads information from a recording medium such as a video disk and a digital audio disk has been widely used. In these, information is recorded in information tracking having a fine width, and in order to reproduce information from these, generally precise tracking control is required. In order to perform tracking control, it is necessary to detect a tracking error, and this is usually performed using optical means. In order to optically detect the tracking error, a method of detecting a tracking error from a phase difference between respective signals output from two portions of a photoelectric detector that receives a detection light and outputs an electric signal (hereinafter, a method of detecting the tracking error) This is called a “phase difference method”), or a pair of sub-beams and a photoelectric detector for detecting a tracking error are provided separately from the main beam and the photoelectric detector for reading information, and the tracking error is determined from the level difference between the respective signals. (Hereinafter referred to as a “three-beam method”) is already known.

One of the major features of the optical information reproducing device is that the access time of the target information is short, but in order to take advantage of this feature, how quickly and stably apply the tracking servo to the target information track. It is important that

Hereinafter, a first conventional example and a second conventional example of the above-described optical information reproducing apparatus will be described with reference to the drawings.

FIG. 7 shows a first conventional example of a tracking control signal detecting device of an optical information reproducing device using a phase difference method. In FIG. 7, 1 is a photoelectric detector, 2a is first delay means, 2b is second delay means, 3a is first addition means,
3b is a second adding means, 4 is a phase comparing means, 5 is a low-pass filter, 6 is a comparator, 7 is a preamplifier, 17 is
A dark level detector 18 detects an envelope on the dark level side of the photoelectric detector of the RF signal. Reference numeral 18 denotes a comparator. The operation of the first conventional example of the tracking control signal detecting device configured as described above will be described below.

It is assumed that the photoelectric detector 1 includes four light receiving cells A, B, C, and D as shown in the figure. The signals of the cells C and D of the photoelectric detector located on the front side with respect to the traveling direction of the information track with respect to the dividing line substantially perpendicular to the direction in which the information track mapping extends, respectively, are first and second delay means 2a, The signal is delayed by 2b, and is added to the signals of the cells A and B of the photoelectric detectors corresponding to the respective diagonal directions by the first and second adding means 3a and 3b, respectively. When there is no tracking error, there is no phase difference between these sum signals, but it is already known that when a tracking error occurs, a phase difference occurs between them (for details, see JP-A-52-93222). Gazette). Therefore, the output signals from the first adding means 3a and the second adding means 3b are compared in phase by the phase comparing means 4, and the ripple component is removed from the output by the low-pass filter 5, whereby a tracking error signal can be obtained. (For example, JP-A-57-181433) By comparing the tracking error signal with its reference level by the comparator 6, a CROSS signal can be obtained. The information reading signal is amplified by the preamplifier 7 and becomes an RF signal. Further, the envelope signal on the dark level side of the RF signal is extracted by the dark level detector 17, and the OFTR signal can be obtained by comparing the envelope signal N with a predetermined reference level O. The positional relationship of the RF signal, the envelope signal N, the OFTR signal, the tracking error signal, and the CROSS signal with the information track is as shown in FIG.

The CROSS signal is used to count the number of tracks over which the light beam for information reading jumps when accessing a target information track, and to detect jumping of tracks in trick play such as a pause operation. The OFTR signal is used for tracking servo stability determination and the like.

Also, from the phase relationship between the CROSS signal and the OFTR signal, it is possible to detect a direction signal in which the light beam is moving during access to a target information track. This will be described with reference to FIG. In FIG. 9, 19a and 19b are edge detectors, and 20a, 20b and 21 are D flip-flops. In FIG. 8, when the information reading beam is moving in the direction of arrow E, the relationship between the CROSS signal and the OFTR signal is as shown in FIG. 9 (b), and the direction shown in FIG. 9 (a). The direction signal becomes “H” level by the detection circuit. When the moving direction is the direction of arrow F in FIG. 8, the direction signal is "L".
Level. At this time, when the CROSS signal and the OFTR signal are inverted, since there are many edges, D-flip-flops 20a and 20b are provided to shape the waveform. This signal P
This makes it possible to count the number of tracks jumped more accurately than directly counting the CROSS signal,
In addition, the tracking brake device that converges the mechanical vibration of the tracking device in a short time can be operated by the direction signal.

FIG. 10 shows a second conventional example of a tracking control signal detecting device of an optical information reproducing device using a phase difference method.

In FIG. 10, 1 is a photoelectric detector, 2a is first delay means, 2b is second delay means, 3a is first addition means, 3b is second addition means, 4 is phase comparison means, Is a low-pass filter, 6 is a comparator, 7 is a preamplifier, 8 is an absolute value detecting means, and 22 is a level detecting means. The operation of the second conventional example of the tracking control signal detecting device configured as described above will be described below.

Since the tracking error signal, the CROSS signal, and the RF signal can be obtained in the same manner as in the first conventional example, detection of the OFTR signal will be described below. First and second addition means
As described above, the output signals 3a and 3b have no phase difference when there is no tracking error, but have a phase difference when there is a tracking error. The tracking phase difference signal has a waveform as shown in FIG. 2 due to the relative positional relationship between the information track and the beam spot. This is because a tracking phase difference signal indicates a tracking error on an information track, but a large phase difference occurs randomly between information tracks because signals of information tracks on both sides are superimposed on an output signal of a photoelectric detector. This phase difference signal becomes a tracking error signal as shown in FIG. On the other hand, an absolute value signal of the tracking phase difference signal is generated by the absolute value detecting means 8, and has a waveform substantially as shown in FIG. FIG. 11 shows an example of a conventional configuration of the level detecting means 22. In FIG. 11, 10 is a charge pump, 11 is a voltage limiter, 12 is a detecting means, and 23 is a comparator. The tracking phase difference signal E in FIG. 10 has a polarity discretely as shown in FIG. 4 with respect to time, and has a pulse width according to the relative positional relationship between the information track and the beam spot. Detected
The absolute value signal F of the tracking phase difference signal is output from the absolute value detecting means 8 as shown in FIG. The signal F operates the charge pump 10 provided with the voltage limiter 11 so that the output voltage does not become lower than the predetermined reference voltage, and the output signal G becomes as shown in FIG. This signal G is detected by the detection means 12 and a signal H as shown in FIG. 4 is output. FIG. 12 shows the signals G and H in more detail. This signal H is compared with a predetermined level R and a comparator.
By comparing at 23, an OFTR signal is obtained. The RF signal, OFTR signal, tracking error signal, and CROSS signal thus obtained can be used for a tracking control signal and tracking stability determination, as described in the first conventional example.

However, in the configuration as in the first conventional example, the CROSS signal and the OFTR signal necessary for detecting the direction signal are extracted from the tracking error signal and the RF signal, respectively. When the phase difference between the tracking error signal and the RF signal occurs due to the optical axis deviation of the optical system of the information reading means or the optical characteristic deviation in the manufacturing of the information recording medium, There has been a problem that the detection circuit malfunctions and becomes unstable. Also, because the OFTR signal detects and extracts the dark level envelope of the RF signal, it is difficult to set the detection time constant, and it is only possible to obtain the correct OFTR signal when jumping over a track in a limited frequency range. There were also problems.

Further, in the configuration as in the second conventional example, although the problem pointed out in the first conventional example has been solved, the output signal of the photoelectric detector between the information tracks has the signal of the information track on both sides. Due to the fact that a large tracking phase difference is generated randomly for superposition, it is difficult to generate a large tracking phase difference due to the phase relationship between the information pits arranged on the information tracks on both sides. The predetermined level R has to be set sufficiently smaller than the level of the absolute value signal of the tracking error signal in consideration of the case where the time interval that occurs is long. As a result, the detection sensitivity of the OFTR signal is increased, and the OFTR signal is generated even with a small dropout (defect) of the information recording medium, and the OFTR signal is generated even when a tracking servo tracking error is large. There are problems that the detection circuit malfunctions, complicated condition judgment is required to use the OFTR signal for stability determination of the tracking servo, and the duty ratio of the OFTR signal becomes large. Was.

In view of the above problems, the present invention is less affected by the deviation of the optical characteristics of the information reading means and the information recording medium, can detect the OFTR signal stably over a wide range of track jump frequencies, and By providing a tracking control signal detector that can easily be used for tracking servo stability determination without having to set the detection sensitivity of the OFTR signal high, it is possible to provide an optical information reproducing device that can be accessed stably at high speed. Things.

Means for Solving the Problems In order to solve the above-mentioned problems, an optical information reproducing apparatus according to the present invention comprises a dividing line substantially parallel to a direction in which a mapping of an information track of a recording medium on which information is recorded in an uneven manner extends. An optical pickup having a light receiving cell divided at least into four by a dividing line substantially perpendicular to the light receiving cell and forming a far-field image of a light spot converged on the recording medium over the four light receiving cells. A photodetector, two light-receiving cells disposed on one side divided by a dividing line substantially perpendicular to a direction in which the information track extending on the photodetector extends, and a photodetector on the other side. First and second delaying the signals output from the two light receiving cells on either side in a direction to cancel the phase difference at the time of focusing the output signal between the two light receiving cells disposed. Delay means; A first adding means for adding an output signal from the first delay means and a corresponding output signal from a light receiving cell disposed at a diagonal position of the light receiving cell; Second adding means for adding the output signal of the light receiving cell and the corresponding output signal from the light receiving cell disposed at the diagonal position of the light receiving cell; and a signal from the first adding means and the second adding means. Phase comparing means for detecting a phase difference of an output signal; absolute value detecting means for detecting an absolute value of a phase difference output signal of the phase comparing means; and an output signal of the absolute value detecting means, wherein the light spot is an information track. When it is higher than the predetermined level I that does not occur, the detection signal is output when it is detected that the level is higher than the predetermined level I. Release That is characterized in that a level detector of a so-called Schmidt operations.

The present invention detects the absolute value of the tracking error signal that has become larger than a predetermined level I that does not occur when the light spot is on the information track, and outputs a detection signal. By detecting that the signal has become larger than the predetermined level J smaller than the level I and canceling the detection signal, an OFTR signal is obtained by a level detector performing a so-called Schmitt operation, whereby the optical axis of the optical system of the information reading means is obtained. A cross signal and OFTR signal that maintain a stable phase relationship without being affected by the shift or the optical characteristic shift of the information recording medium,
Since the OFTR signal can be detected stably even in a wide range of track jump frequencies, the direction detection circuit does not malfunction and there is no need to set the detection sensitivity of the OFTR signal high, so the tracking servo can be easily stabilized. A tracking control signal detection means capable of detecting an OFTR signal that can be used for the determination can be configured.

As a result, the number of tracks jumped can be counted more accurately, and the tracking brake device that converges the mechanical vibration of the tracking device in a short time can be stably operated.

Embodiment Hereinafter, an optical information reproducing apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a tracking control signal detecting device of an optical information reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a photoelectric detector, 2a is a first delay means, 2b is a second delay means, 3a is a first addition means, 3b is a second addition means, 4 is a phase comparison means, Is a low pass filter, 6 is a comparator, 7 is a preamplifier, 8 is an absolute value detecting means, and 9 is a Schmitt operation level detecting means. The operation of the tracking control signal detecting means of the optical information reproducing apparatus configured as described above will be described below with reference to FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG.

It is assumed that the photoelectric detector 1 includes four light receiving cells A, B, C, and D as shown in the figure. The signals of the cells C and D of the photoelectric detector located on the front side with respect to the traveling direction of the information track with respect to the dividing line substantially perpendicular to the direction in which the information track mapping extends, respectively, are first and second delay means 2a, The signal is delayed by 2b, and is added to the signals of the cells A and B of the photoelectric detectors corresponding to the respective diagonal directions by the first and second adding means 3a and 3b, respectively. As described above, 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, the output signals from the first adding means 3a and the second adding means 3b are compared in phase by the phase comparing means 4, and the ripple component is removed from the output tracking phase difference signal E by the low-pass filter 5 to perform tracking. An error signal can be obtained. In addition, a CROSS signal can be obtained by comparing the tracking error signal with its reference level by the comparator 6. This tracking phase difference signal is substantially the second due to the relative positional relationship between the information track and the beam spot.
It is a waveform as shown in the figure. This is because a tracking phase difference signal indicates a tracking error on an information track, but a large phase difference occurs randomly between information tracks because signals of information tracks on both sides are superimposed on an output signal of a photoelectric detector. This phase difference signal is subjected to a low-pass filter 5 to remove a ripple component, and the positive and negative tracking phase difference signals are canceled and averaged between tracks, thereby forming a tracking error signal as shown in FIG. On the other hand, an absolute value signal of the tracking phase difference signal is generated by the absolute value detecting means 8 as shown in FIG. An example of the configuration of the Schmitt operation level detecting means 9 is shown in FIG. In FIG. 3, 10 is a charge pump,
11 is a voltage limiter, 12 is detection means, 13a and 13b are comparators, and 14 is an RS (reset set) flip-flop. When the tracking phase difference signal E in FIG. 1 is represented on the axis of time, it has a discrete polarity as shown in FIG. 4, and has a pulse width corresponding to the relative positional relationship between the information track and the beam spot. The absolute value signal F of the tracking phase difference signal is output from the absolute value detecting means 8 as shown in FIG. The signal F operates the charge pump 10 provided with the voltage limiter 11 so that the output voltage does not become lower than the predetermined reference voltage.
It looks like the figure. This signal G is detected by the detection signal 12, and a signal H is output as shown in FIG. FIG. 5 shows the signals G and H in more detail. This signal H is compared with a predetermined level I by a comparator 13a, and a signal K indicating that the signal H has become larger than the predetermined level I
Is obtained. Further, a comparator for comparing the signal H with a predetermined level J set lower than the predetermined level I
13b, a signal L indicating that the signal H has become larger than the predetermined level J is obtained. By inputting the signals K and L to the set input and the reset input of the RS flip-flop 14, an OFTR signal is obtained from the non-inverted output of the RS flip-flop 14.

As described above, according to the present embodiment, by detecting the OFTR signal from the tracking phase difference signal, the CORS necessary for detecting the direction signal in the configuration as in the first conventional example is obtained.
The S signal and OFTR signal are the tracking error signal and R signal, respectively.
The phase relationship between the tracking error signal and the RF signal due to the optical axis deviation of the optical system of the information reading means and the optical characteristic deviation in the production of the information recording medium due to the extraction from the F signal When the deviation occurs, the direction detection circuit malfunctions and becomes unstable, and the detection time constant is set because the dark level envelope of the RF signal is detected and extracted from the OFTR signal. It is difficult to solve the problem that a correct OFTR signal can be obtained only when jumping over a track in a limited frequency range.

Further, according to the present embodiment, by providing the Schmitt operation level detecting means 9, the output signal of the photoelectric detector between the information tracks in the configuration as in the second conventional example is changed to the signal of the information tracks on both sides. When a large tracking phase difference is generated at random because of the superposition of the information, it is difficult to generate a large tracking phase difference due to the correlation between the information pits arranged on the information tracks on both sides. The predetermined level R does not need to be set sufficiently small with respect to the level of the absolute value signal of the tracking error signal in consideration of the case where the time interval in which the error occurs becomes longer. Therefore, the detection sensitivity of the OFTR signal is reduced. Is high, an OFTR signal is generated even with a small dropout (defect) of the information recording medium, and the tracking servo follows Even when the difference is large, an OFTR signal is generated, and complicated condition judgment is required to use the OFTR signal for stability determination of the tracking servo, and the duty ratio of the OFTR signal increases. The problem of getting lost can be solved.

Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 shows a second configuration example of the Schmitt operation level detecting means 9 of FIG. 1, wherein 15 is a comparator and 16 is an inverter. The operation will be described below.

The signal H obtained in the same manner as in the first embodiment is input to a comparator 15 to which positive feedback has been applied by a resistor, and the signal H is higher than a predetermined level M by a value determined by the positive feedback amount and higher. The output of the comparator 15 becomes "L" level, and when the signal H becomes smaller than the predetermined level M by a value smaller than the predetermined level M by a positive feedback amount, the output of the comparator 15 becomes "H" level. . The OFTR signal is obtained by inverting the output signal of the comparator 15 by the inverter 16. The value determined by the positive feedback amount can be arbitrarily set by the ratio of the two resistor values.

As described above, the Schmitt operation level detecting means 9 provided with the comparator 15 multiplied by the positive feedback amount by the resistor.
Is provided, the same effect as in the first embodiment can be obtained at low cost.

Although the photoelectric detector 1 is divided into four in the first and second embodiments, it may be divided into more. Also, the first
The second delay means includes two light receiving cells arranged on one side divided by a dividing line substantially perpendicular to a direction in which the information track extending on the photoelectric detector 1 extends, and the other side. In order to cancel the phase difference at the time of focusing of the output signal between the two light receiving cells disposed on the one side, the respective signals output from the two light receiving cells on one side are delayed. It may be a purpose and means for advancing each signal on the other side. Although the operations of the absolute value detecting means 8 and the level detecting means 9 have been described using analog signals, it goes without saying that the operations may be digital signal operations or computer software operations. No. Also, it should be added that the present invention is not limited by the detection method of the tracking error signal or the CROSS signal.

Effects of the Invention As described above, the present invention provides at least four division lines that are substantially parallel to the direction in which the mapping of the information track on the recording medium on which information is recorded in the form of projections and depressions extends.
A photoelectric detector of an optical pickup having a divided light receiving cell and forming a far-field image of a light spot converged on the recording medium over the four light receiving cells, and mapping on the photoelectric detector Between two light receiving cells disposed on one side and two light receiving cells disposed on the other side, which are separated by a dividing line substantially perpendicular to the direction in which the information track extends. First and second delay means for delaying the respective signals output from the two light receiving cells on either side in a direction to cancel the phase difference at the time of focusing of the signal; First adding means for adding an output signal and an output signal from a light receiving cell disposed at a diagonal position of the light receiving cell corresponding thereto, and an output signal from the second delay means and corresponding thereto The diagonal position of the light receiving cell Second adding means for adding an output signal from the light receiving cell, phase comparing means for detecting a phase difference between the output signals from the first adding means and the second adding means, and a position of the phase comparing means. An absolute value detecting means for detecting an absolute value of the phase difference output signal; and detecting that the output signal of the absolute value detecting means has become larger than a predetermined level I which does not occur when the light spot is on the information track. A so-called Schmitt operation level detector that outputs a signal and detects that the level has become larger than a predetermined level J smaller than the predetermined level I and cancels the detection signal. There is little effect due to the deviation of the optical characteristics of the recording medium, and OF is stable over a wide range of track jump frequencies.
Since the TR signal can be detected and the detection sensitivity of the OFTR signal can be set appropriately, even if a small dropout (defect) of the information recording medium generates the OFTR signal or the tracking servo tracking error is large. It is possible to realize a tracking control signal detection device that can obtain an OFTR signal that does not generate an OFTR signal and that can easily use the OFTR signal for tracking servo stability determination. An optical information reproducing apparatus capable of performing the above can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a tracking control signal detecting device portion of an optical information reproducing device according to an embodiment of the present invention;
FIG. 2 is a waveform diagram illustrating the relative positional relationship between the information track and the light beam spot for explaining the operation of FIG. 1, and FIG. 3 is a diagram of the level detector 9 of the Schmitt operation of FIG. FIG. 4 is a block diagram of the embodiment of the present invention, FIG. 4 and FIG. 5 are time-axis waveform diagrams for explaining the operation of FIG. 1 and FIG. 3, and FIG. FIG. 7 is a block diagram of a tracking control signal detecting device portion of the optical information reproducing apparatus in the first conventional example, and FIG. 8 is information for explaining the operation of FIG. A signal waveform diagram centering on the relative positional relationship between the track and the light beam spot,
FIG. 9 is a block diagram and a waveform diagram showing an example of a moving direction detecting means of the tracking device of the optical information reproducing apparatus.
FIG. 1 is a block diagram of a tracking control signal detecting device portion of an optical information reproducing device according to a second conventional example. FIG. 11 is a configuration diagram showing an example of the configuration of the level detecting means 9 in FIG.
FIG. 12 is a time-based waveform diagram for explaining the operation of FIGS. 10 and 11. 1 ... photoelectric detector, 2a ... first delay means, 2b ... second
Delay means, 3a... First addition means, 3b... Second addition means, 4... Phase comparison means, 5.
6, 13a, 13b, 15, 18, 23 ... comparator, 7 ... preamplifier, 8 ... absolute value detecting means, 9 ... level detecting means for Schmitt operation, 10 ... charge pump, 11 ... limiter , 12 ... Detection means, 14 ... RS flip-flop, 16 ...
... Inverter, 17 ... Dark level detector, 19 ... Edge detecting means, 20a, 20b, 21 ... D flip-flop, 22 ... Level detecting means.

Claims (1)

(57) [Claims] 1. A light receiving cell which is divided at least into four by a dividing line substantially parallel to a direction in which an image of an information track of a recording medium on which information is recorded in an uneven manner extends and a dividing line substantially perpendicular to the dividing line. And a photoelectric detector of the optical pickup, which forms a far-field image of the light spot converged on the recording medium over the four light receiving cells, and an extension of the information track mapped on the photoelectric detector. Position at the time of focusing of an output signal between two light receiving cells provided on one side and two light receiving cells provided on the other side, which are separated by a dividing line substantially perpendicular to the direction in which they exist. First and second delay means for delaying the respective signals output from the two light receiving cells on either side in a direction to cancel the phase difference; output signals from the first delay means and corresponding signals Diagonal position of light receiving cell A first adding means for adding an output signal from the light receiving cell provided, and an output signal from the second delay means and a light receiving cell disposed at a diagonal position of the light receiving cell corresponding thereto. Second adding means for adding the output signals of the first and second adding means, a phase comparing means for detecting a phase difference between the output signals from the first adding means and the second adding means, and a phase difference output signal of the phase comparing means. An absolute value detecting means for detecting the absolute value of the signal; and a predetermined level I which is not generated when the light spot is on the information track.
Detecting that the level has become larger, outputs a detection signal, and outputs a predetermined level J smaller than the predetermined level I.
An optical information reproducing apparatus, comprising: a so-called Schmitt operation level detector for detecting that the detection signal has become smaller and canceling the detection signal.