JPS6242364A - Device for detecting rotary synchronizing mark - Google Patents

Abstract

PURPOSE:To improve the accuracy of mark detection by providing two photodetectors and detecting a rotary synchronizing mark from the differential signal of a reflectance change between a position crossed with a mark and a position other than the mark in its vicinity so as to reduce the effect of a flaw or dirt on a disk surface. CONSTITUTION:In constituting the titled device that a rotary synchronizing mark 33 is driven in the direction of the arrow X at the upper side of a photodetector 24 of a mark detector comprising a light emitting diode 11b and two photodetectors 24, 25, when the mark crosses the photodetector, waveforms shown in (b-1), (b-2) appear as the output signal of the photodetectors 24, 25. Each detection signal is amplified differentially as shown in (b-3) by the 1st differential amplifier circuit 26. The signal subjected to differential amplification is compared with a DC voltage V1 from the 1st DC voltage generating circuit 28 by a waveform shaping circuit 27, becomes a binary signal (b-5) and becomes a rotary synchronizing signal and a disc type discrimination signal. When a dirt 34 on the disc surface is amplified differentially, the level does not almost effect on the waveform shaping and the dirt is not detected as a mark in error.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to information recording disks (hereinafter referred to as disks) such as video disk players and data file devices.
The present invention relates to a rotation synchronization mark detection device in a recording, reproducing, and erasing device.

2. Description of the Related Art In general, a rotation synchronization signal for a disk motor, which rotates a disk at a desired rotation speed and phase when a disk is mounted, is obtained by detecting a rotation synchronization mark recorded on the disk. FIG. 3 shows an example of a rotation synchronization mark.

In FIG. 3, part 2 is an information recording track that is spiral or concentric and has a constant trunk pitch, and is an area where information signals can be recorded on the track using a laser beam or the like. be. 4 is a rotation synchronization mark for controlling the rotational phase of the disk motor that rotates the disk. This rotation synchronization mark 4
, similar to the information recording track 2, are formed as a groove structure during master recording. However, whereas the information recording track 2 forms a concentric or spiral continuous track by continuously recording with a laser beam of constant intensity over the entire circumference except for the address 3, the rotation synchronization mark ,
Grooves are intermittently formed by irradiating a laser beam with a constant intensity only over a certain angular variation. Therefore, while the area other than the mark in the rotation synchronization mark area is an extremely smooth flat surface, the rotation synchronization mark area has a groove structure, and the reflected light is scattered due to the unevenness of the surface, which reduces the reflectance. A rotation synchronization mark can be detected as a difference. Specifically, a light emitting diode and a photodetector detect the difference in reflectance between the rotational synchronization marks on the disk and convert it into an electrical signal.

Next, a specific example of the configuration of the rotation synchronization mark detection device is shown in FIG. A simple operation for detecting a rotation synchronization mark will be explained using FIG. A disk 5 is mounted on a rotating shaft of a disk motor 7 by a clamper 6. A rotation synchronization mark detector 11 consisting of a light emitting diode 11b and a photodetector 11a is placed on the disk 5 rotated by the disk motor 7, facing the area where the rotation synchronization mark is recorded, and is rotationally synchronized with the disk 5. A slit that is elongated in the radial direction and has a desired width in the rotational direction is arranged between the mark detector 11 and the mark detector 11 . This slit is provided to improve the accuracy of reading the rotation synchronization mark. A constant current source 12 is provided for the light emitting diode 11b.
A desired current is supplied to the light source, and the light is emitted with a desired amount of light. The photodetector 11a detects the difference in reflectance between the rotation synchronization mark and other parts and converts it into an electrical signal. The detected signal is binarized by the waveform shaping circuit 13 and becomes a rotation synchronization signal. This rotation synchronization signal becomes a reference signal for the rotation phase control circuit 9 of the disk motor. The output signal of the rotation phase control circuit 9 is converted into a drive signal by the disk motor drive circuit 8, and the rotation phase of the disk motor 7 is changed according to the phase of the rotation synchronization signal.

Now, Japanese Patent Application No. 59-16518 proposes that a mark indicating the type of disc be provided outside the information track band. By using the disc according to this proposal, it is possible to construct a system that can record and play back many types of discs by identifying marks recorded in advance on the disc.

In particular, since the discrimination mark is formed in the same groove as the information recording trunk, the discrimination mark can also be formed at the same time as the information recording track is formed. This method also has the advantage that the positions of the identification marks and addresses can be formed with high precision.The disc according to the above proposal will be briefly described below.

FIG. 5 shows an embodiment of the disk according to the above proposal. In FIG. 6, parts assigned the same numbers as in FIG. 3 are parts that perform the same functions as in FIG. 3. The difference from the disc shown in FIG. 3 lies in the discrimination mark 14. This discrimination mark also serves as a rotation synchronization mark, and among the three marks shown in the figure, the first mark serves as a rotation synchronization mark. The type of disc can be identified by the number or position of these marks.

FIG. 6 shows an example of the configuration of a discrimination mark detection and identification device. Compared to FIG. 4, a decoder circuit 16 for identifying the discrimination mark is added. Similar to the operation described above, the photodetector 11a converts the difference in reflectance into an electrical signal, and the waveform shaping circuit 13 converts it into a binary signal. 2. The decoder circuit 15 uses the converted discrimination signal to identify the discrimination signal and determine what type of disc it is. In this way, the synchronization mark detection device can also detect the type of disc.

Problems to be Solved by the Invention However, the above configuration has the following problems.

To identify synchronization marks and discrimination marks recorded on a disc, a light emitting diode and a photodetector are used to detect the difference in reflectance between the discrimination mark parts on the disc surface. If there are other parts where the reflectance has changed due to scratches or the like, erroneous marks will be detected in addition to the correct marks in the waveform-shaped electrical signal. Detection of such an erroneous signal will lead to malfunction of the device. Rotation synchronization marks and discrimination marks are detected by different reflectances, but since the reflectance can easily change due to dirt or scratches on the disk surface, dirt, scratches, cloudiness, etc. can cause rotation synchronization marks to be detected. There is a good chance that it will be mistakenly identified as a discrimination mark.

As described above, while it is effective to record a rotation synchronization mark or a discrimination mark on a disk, there is a problem in that it is prone to malfunction due to dirt, scratches, etc. on the disk surface.

Therefore, a disc with improved mark detection accuracy was proposed in Japanese Patent Application No. 111152/1983. The above proposal is to solve the conventional problems, and in order to make it possible to record or play back various types of discs with one recording/playback device,
The purpose is to automatically determine the type of disc with high accuracy.

The above proposal includes one or more discrimination marks indicating the type of disc at a specific position on the inner or outer circumferential side of a concentric or spiral information track, and a mark that is sufficiently wider than the discrimination mark. It is a disk that has one or more. FIG. 7 shows an embodiment of the above proposal, in which reference numeral 2 denotes an information recording track band having a spiral or concentric shape and a constant track pitch, and an information signal is recorded on the track using a laser beam or the like. This is an area where it is possible to Reference numeral 1 denotes a center hole 3 through which a disk is attached to a disk motor, and is an address area in which the address of each track is recorded. These are the same as the conventional example. 16 to 23 are discrimination marks that are the characteristics of the above proposal.

In the conventional example, a discrimination mark was recorded at only one location, but here, marks are recorded at seven other locations. Furthermore, the mark 23 in particular is formed much wider than the other marks. This mark 23 is called a flag mark, and marks 16 to 23 are called first to seventh marks, respectively. The flag mark and the first to seventh marks are detected by a mark detector having a conventional configuration and converted into electrical signals. When the detection signal is passed through a desired low frequency door transducer, only the flag mark can be extracted due to the difference in mark width.
If you create a gate signal to extract each signal from to the seventh mark and use this gate signal to detect each mark, you can eliminate the conventional problem of reading incorrect marks due to dirt or scratches on the disk surface. This makes it possible to read marks stably and with high precision.

Although this method of forming marks recorded on a disc greatly improves the conventional problems, a method for solving the problems is also needed on the mark detection device side.

Means for Solving the Problems In order to solve the above-mentioned problems, the rotation synchronization mark detection device of the present invention differentially amplifies the detection signal of the mark below the conventional photodetector, and The dynamically amplified signal is subjected to waveform shaping into a binary signal by a waveform shaping circuit, and is used as a rotation synchronization mark detection signal. Furthermore, the amount of light from the light source is adjusted depending on the reflectance of the disc.

Effect: Due to the above-described configuration, the present invention reduces erroneous reading of marks due to dirt or scratches on the disk surface or changes in reflectance compared to conventional rotation synchronous mark detection devices, and provides stable and accurate reading. It becomes possible to read tall marks.

Embodiment Hereinafter, a rotation synchronization mark detection device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a rotation synchronization mark detection device according to an embodiment of the present invention. FIG. 2(a) illustrates a mark detection section in an embodiment of the present invention,
(b) shows an example of the waveform of each part shown in FIG. Components in FIG. 1 that are given the same numbers as in FIG. 6 have the same functions as those in FIG. 6. In the figure, 24 to 32 are blocks according to the present invention. Note that (b-1) to (b-5) each correspond to (b-1) in FIG. 2(b).
-1) to (b-5).

Now, as shown in FIG. 2(a), the light emitting diode 11
b and two photodetectors 24 and 25.
If the rotation synchronization mark 33 is configured to rotate above the photodetector 24 side of the photodetector 9 in the direction of the arrow X shown in the figure, if the mark crosses the photodetector, b-1
), the waveform as shown in (b-2) is detected by the photodetector 24.
It appears as the output signal of 25. Each detection signal is
The first differential amplifier circuit 26 differentially amplifies the signal into a waveform as shown in (-ba). The differentially amplified signal is converted to DC by the first DC voltage generating circuit 28 by the waveform shaping circuit 27.
The voltage level is compared with the voltage level of voltage V1 (b-4), and a binary signal (b-5) is generated. This binary signal (b-s) becomes a rotation synchronization signal and a disc type determination signal. As is clear from FIG. 2(b), dirt 34 on the disk surface
When is differentially amplified, it becomes a level that has almost no effect when shaping the waveform, and it will not be mistakenly detected as a mark.It is the second light that receives the reflected light flux of the part other than the 3 marks. The output signal of the detector is converted into only low-frequency components by a reduction filter circuit 3o. The signal converted into only the low frequency component and the DC voltage signal generated by the second DC voltage generation circuit 31 are differentially amplified by the second differential amplifier circuit 32. The current value supplied from the constant current source 12 to the light emitting source 11b is changed according to the differentially amplified signal level. That is, due to this loop, the output signal level (b-2) of the second photodetector is always kept constant despite fluctuations and dispersions in the reflectance of parts of the disc other than the marks. For example, when the reflectance is lower than a desired level, the output signal of the low-frequency door filter 30 becomes smaller, the output of the second differential amplifier circuit 32 becomes larger, the current supplied to the light source 11b increases, and the amount of light emitted is increased. increases. Therefore, the output signal level of the second photodetector increases to the desired level. In this way, since variations in reflectance can be almost ignored, there is an advantage that voltages can always be compared at a constant level even when the detection signal is binarized.

It goes without saying that, as in the conventional example, if a desired slit is provided between the mark detector 29 and the disk, the accuracy of mark detection can be further improved.

Effects of the Invention As described above, the present invention provides two photodetectors and detects changes in reflectance at the position where the mark crosses and the change in reflectance, compared to the conventional rotary synchronous mark detection device consisting of a pair of light emitting sources and a photodetector. Since rotation synchronization marks are detected from differential signals of reflectance changes at positions other than the mark in the vicinity, the effects of scratches, dirt, etc. on the disk surface can be reduced, and the accuracy of mark detection can be improved. Stable rotational phase control of the disc motor can be provided. Also, regarding disc identification, it is possible to prevent malfunctions due to reading of incorrect marks. Also, by changing the light intensity of the light source, the desired level is always maintained.
Since it can be converted into a value, it is possible to reduce the influence of changes and variations in reflectance, which is extremely effective.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a rotation synchronization mark detection device showing an embodiment of the present invention, Fig. 2 (,) is an enlarged view of the main part showing the mark detection section, and Fig. 2 (b) is the same as Fig. 1. Fig. 3 is a top view of a disk on which a conventional rotational synchronization mark is recorded; Fig. 4 is a professional diagram showing an example of a conventional rotational synchronization mark detection device; Fig. 5 6 is a top view showing an example of a disc on which the disc type is encoded and a discrimination mark that also serves as a rotation synchronization mark is recorded; FIG. 6 is a block diagram showing an example of a device for detecting the discrimination mark from the disc shown in FIG. 5. , FIG. 7 is a top view showing an example of a disc in which the accuracy of reading discrimination marks is improved. 1...Center hall, 2...Information record e)5, 3...Address area, 4...
... Rotation synchronization mark, 6 ... Disc, 11
b...Light emission source, 24...First photodetector, 25...Second photodetector, 26...
- First differential amplifier circuit, 27... Waveform shaping circuit, 29... Mark detector. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure 5, 9 Figure 6

Claims (4)

[Claims] (1) Facing an information recording disk on which a rotational synchronization mark is recorded in advance, the rotational synchronization mark is located in the vicinity of the same radius as the rotational synchronization mark from the rotation center of the disk, and the emitted light beam is located at the rotational synchronization mark within the disk. at least one light emitting source disposed at a position where it is irradiated with light, and near the light emitting source,
a first photodetector disposed at a position where it can receive the reflected light beam on the disk surface of the emitted light beam irradiated to the rotation synchronization mark; a second photodetector disposed near the detector, on the outer circumference side or the inner circumference side in the radial direction of the disk, and at a position where the reflected light beam from the mark portion cannot be received; A differential amplifier circuit that differentially amplifies the output signal of each of the second photodetectors, and a waveform shaping circuit that binarizes the output signal of the differential amplifier circuit, and the waveform shaping circuit A rotation synchronization mark detection device characterized in that the rotation synchronization mark detection signal is a detection signal of the rotation synchronization mark. (2) The rotation synchronization mark detection device according to claim 1, characterized in that a slit having a desired width is provided at a desired position between the photodetector, the light emitting source, and the information recording disk. (3) The rotational synchronization mark detection device according to claim 1, which detects a mark encoding the type of the information recording disk, etc., in addition to the rotational synchronization mark provided in the information recording disk. . (4) The light emission amount of the light emitting source is changed depending on the magnitude of the output signal of the second photodetector, so that the output signal of the second photodetector is always at a desired level. A rotation synchronization mark detection device according to claim 1.