JP2701322B2 - 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 on an information track having a fine width. In order to reproduce information from the information track, 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 tracking error detection are provided separately from the main beam for reading information and the photoelectric detector, and the tracking error is calculated from the level difference between the respective signals. A detection method (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, an example of the above-described conventional optical information reproducing apparatus will be described with reference to the drawings.

FIG. 3 shows a tracking control signal detecting device of a conventional optical information reproducing device using a phase difference method.
In FIG. 3, 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, 5 Is a low-pass filter, 6 is a comparator, 7 is a preamplifier, 10 is a light level detector that detects the envelope on the light level side of the photoelectric detector of the RF signal, and 11 is a comparator.

The operation 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 the signals are added to the cells A and B of the photoelectric detector 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). Then, 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 a ripple component is removed from the output by the low-pass filter 5 to obtain a tracking error signal. Can be. A cross signal can be obtained by comparing the tracking error signal with its reference level by a comparator 6 (for example, Japanese Patent Application Laid-Open No. 57-181433). The information reading signal is amplified by the preamplifier 7 and becomes an RF signal. Also, the envelope signal on the light level side of the RF signal is extracted by the light level detector 10, and the envelope signal is compared with a predetermined reference level.
An OFTR signal can be obtained. The relationship among the RF signal, the light level detection signal, the OFTR signal, the tracking error signal, and the cross signal 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 the 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 while accessing the target information track. In FIG. 4, when the information reading beam is moving in the direction of arrow E, the direction signal is set to "H" by the direction detecting circuit shown in FIG.
Level. When the moving direction is the direction of the arrow F in FIG. 4, the direction signal is at "L" level. At this time,
Since many edges exist when the cross signal and the OFTR signal are inverted, D-flip-flops 12 and 13 are provided to shape the waveform. This signal makes it possible to count the number of tracks jumped more accurately, and to operate a tracking brake device that converges the mechanical vibration of the tracking device in a short time.

However, in the above configuration, 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 relationship between the tracking error signal and the RF signal is slightly shifted due to the optical axis shift of the optical system or the optical characteristic shift in the production of the information recording medium,
There is a problem that the direction detection circuit malfunctions and becomes unstable. In addition, since the OFTR signal detects and extracts the bright level envelope of the RF signal, the detection time constant is difficult to set, and the correct OFTR signal can only be obtained when jumping over a track in a limited frequency range. He also had points.

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to an OFTR signal detection device which is less affected by a shift in optical characteristics of information reading means and an information recording medium, and is capable of detecting an OFTR signal stably over a wide range of track jump frequencies. The present invention provides an optical information reproducing apparatus capable of performing stable and high-speed access by providing the optical information reproducing apparatus.

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. And a photodetector having a light receiving cell divided 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. 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 perpendicular to the direction in which the information track extends on the photoelectric detector. 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 output signal during Output signal from delay means First adding means for adding an output signal from a light receiving cell disposed at a diagonal position of the light receiving cell corresponding thereto, a pair of an output signal from the second delay means and a light receiving cell corresponding thereto. Second adding means for adding an output signal from the light receiving cell disposed at the corner position, and phase comparing means for detecting a phase difference between the output signals from the first adding means and the second adding means. An absolute value detecting means for detecting an absolute value of a phase difference output signal of the phase comparing means, and a level detector for detecting that an output signal of the absolute value detecting means has become larger than a predetermined value at a predetermined frequency or more. It is provided with.

According to the present invention, the OFTR signal can be obtained by detecting that the absolute value of the tracking phase difference signal has exceeded a predetermined level at a predetermined frequency or more by the above-described configuration. In addition, a cross signal and an OFTR signal that maintain a stable phase relationship without being affected by the optical characteristic deviation of the information recording medium can be obtained, so that the direction detection circuit does not malfunction and the conventional OFTR signal While the detection means could not detect the correct OFTR signal when jumping over a track in a limited frequency range, DC
From a higher track jump frequency, it is possible to more accurately count the number of tracks jumped, and a tracking brake device that converges the mechanical vibration of the tracking device in a short time. It can be operated stably.

Embodiment Hereinafter, an optical information reproducing apparatus according to an 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 an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a photoelectric detector divided by a division line substantially parallel to the direction in which the mapping of the information track extends and a division line substantially perpendicular thereto, and 2a denotes a first light-receiving cell connected to the light receiving cell C. The delay means, 2b is a second delay means connected to the light receiving cell D, and 3a is a first adding means for adding the output of the light receiving cell A and the output of the first delay means 2a. Reference numeral 3b denotes second adding means for adding the output of the light receiving cell B and the output of the second delay means 2b. 4
Is a phase comparing means for detecting a phase difference between the outputs of the first and second adding means, 5 is a low-pass filter, 6 is a comparator, 7 is a preamplifier, and 8 is an absolute value of the output of the phase comparing means 4. The absolute value detecting means 9 is a level detecting means for detecting that the output signal of the absolute value detecting means has become larger than a predetermined value at a predetermined frequency or more.

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 FIGS.

As described above, the output signals of the first and second adding means 3a and 3b do not have a phase difference when there is no tracking error, but have a phase difference when there is a tracking error. This phase difference signal has a waveform substantially as shown in FIG. 2 (signal J). This is because a phase difference indicates a tracking error on an information track, but a large phase difference is randomly generated 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 by the low-pass filter 5. On the other hand, an absolute value signal of the tracking phase difference signal is generated by the absolute value detecting means 8. The result is substantially as shown in FIG. 2 (signal K). The level detecting means 9 detects the envelope of the absolute value signal, compares the detected signal with a predetermined level, and outputs an OFTR signal. The setting of the detection time constant of the level detecting means 9 is compared with the setting of the light level detector 10 because the value of the absolute value signal on the information track and the value between the information tracks have a large difference. Thus, a sufficiently easy and stable OFTR signal can be obtained.

In this embodiment, the photoelectric detector 1 is divided into four parts.
Further, it may be multi-divided. 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.

Effect of the Invention As described above, the present invention provides a light receiving cell of a photoelectric converter divided into four by a dividing line substantially parallel to a direction in which a mapping of an information track extends and a dividing line substantially perpendicular to the dividing line. In the direction to cancel the phase difference at the time of focusing of the output signal between the two light receiving cells arranged on one side and the two light receiving cells arranged on the other side, which are separated by a simple dividing line,
Means for delaying the respective output signals of the two light receiving cells on either side, the respective output signals from the delay means and the corresponding output signals from the light receiving cells disposed at diagonal positions of the light receiving cells And addition means for respectively adding
A phase comparing means for detecting a phase difference between output signals from the respective adding means, an absolute value detecting means for detecting an absolute value of the phase difference output signal of the phase comparing means, and an output signal of the absolute value detecting means. And a level detector for detecting that the frequency has become larger than a predetermined value more than the frequency of the data. Can detect the OFTR signal stably
By providing the OFTR signal detection device, it is possible to provide an optical information reproducing device capable of performing stable high-speed access.

[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 signal waveform diagram for explaining the operation of FIG. 1, FIG. 3 is a block diagram of a tracking control signal detecting device portion of a conventional optical information reproducing device, and FIG.
FIG. 5 is a block diagram showing an example of the moving direction detecting means of the tracking device of the optical information correcting device, and its waveform diagram. 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, 11 comparator, 7 pre-amplifier, 8 absolute value detecting means, 9 level detecting means, 10 bright level detector.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akihiko Nishioka 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-165738 (JP, A) JP-A-52- 93222 (JP, A) JP-A-57-181433 (JP, A)

Claims (1)

(57) [Claims] 1. A light receiving cell divided into four parts 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.
A photoelectric detector that forms a far-field image of a light spot converged on the recording medium over the four light receiving cells;
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 perpendicular to the direction in which the information tracks extend on the photoelectric detector. First and second delay means for delaying respective signals output from the two light receiving cells on either side in a direction to cancel a phase difference at the time of focusing of an output signal between the first and second signals; A first adding means for adding an output signal from the delay means of the above and a corresponding output signal from a light receiving cell arranged at a diagonal position of the light receiving cell;
Second adding means for adding the output signal from the delay means and the corresponding output signal from the light receiving cell disposed at the diagonal position of the light receiving cell, the first adding means and the second adding means.
Phase comparing means for detecting a phase difference of an output signal from the adding means, an 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 being a predetermined value. An optical information reproducing apparatus, comprising: a level detector for detecting that the frequency has become larger than a predetermined value more than the frequency.