JPH0252348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording/reproducing device, and more particularly, to detecting a rotation start position mark of a disk on which concentric circular or spiral guide tracks and address information are formed in advance for each guide track. be.

With the recent development of highly sensitive optical recording materials, in addition to the playback-only function of conventional video disks, they are now capable of recording and playing back signals in real time by themselves. Such optical recording and reproducing devices generally irradiate a disk with a photosensitive material on it or evaporate it with light whose intensity is modulated by a recording signal, and produce changes in unevenness, refractive index, reflectance, etc. on the disk. Information such as video signals can be recorded in real time as changes in the optical characteristics of
A device has already been proposed that can reproduce recorded information by detecting changes in its optical characteristics. In such a device, in order to record a group of video signals, etc. on selected tracks on a disk and to realize playback, the track to be recorded is formed in advance on the disk as a guide track, for example, in the shape of a groove, and then a guide track is formed on the disk. When forming the
At the same time, address information is formed on each guide track using a serial number from the outer circumference (or inner circumference) to the inner circumference (or outer circumference) of the disk as a phase change of the unevenness.

A disk with guide tracks has address information on each track formed in an arc shape forming a certain angle with respect to the center of the disk. Now, when recording a TV image on one track of this disk, it is necessary to prevent image information from being recorded in the address information section of this track. To do this, it is necessary to control the rotation of the disk so that the vertical synchronization signal of the TV image signal and the address information part are recorded in substantially the same phase. For this purpose, it has been proposed to separately provide a rotation start position mark on the disk at a position corresponding to the address information.

This rotation start position mark is formed by adhering aluminum foil, vapor depositing a mirror material, or the like. In addition, as a forming method that takes into account the positional accuracy and productivity of this rotation start position mark, at the same time as forming the guide track,
It has been proposed to form a rotation start position mark consisting of a plurality of arcuate guide tracks on the inner or outer circumference of the disk.

The rotation start position mark is used to detect the rotation of the disk in order to rotate the disk in synchronization with an external video signal during recording, and to rotate the disk in synchronization with an internal reference oscillator during playback. It is also used to determine the timing when reading the rotation start position mark, so it is extremely important for the operation of this disk device to stably and accurately detect the rotation start position mark.

Detection of the rotation start position mark does not use an optical head using a laser, but instead uses elements such as a light emitting diode and a phototransistor, so the sensitivity and frequency characteristics are not good, and it is difficult to track the surface runout of the disk. Therefore, it is not easy to detect the rotation start position mark while covering the difference in reflectance between disks and being unaffected by scratches on the disk.
In particular, it has been confirmed that some scratches have a reflectance comparable to that of the rotation start position mark.

FIG. 1 shows an example of a conventional optical disk. The optical disk 1 is composed of a track portion 2 consisting of a groove-shaped guide track, absolute track address information portions 3 and 4 formed on the guide track, and a rotation start position mark 5. The absolute address information sections 3 and 4 are formed at an angle α with respect to the center 6 of the optical disk 1.

FIG. 2 is an enlarged cross-sectional view of a part of the track, in which part of the guide track 2 and the address information section 3 are shown in a line. The track address information is formed as uneven pits in the form of a modulation signal such as FM modulation or PE modulation.

FIG. 3 is an enlarged cross-sectional view of the rotation start position mark 5. The disk 1 corresponding to the rotation start position is cut and detected as a difference in reflectance using a light emitting diode and a phototransistor.

FIG. 4 shows an example of the configuration of a rotation start position mark reading device. 1 is the aforementioned disk, and 6 is a motor for rotating the disk 1. The light beam emitted from the light source 7 is reflected by the aforementioned rotation start position mark 5, enters the light receiver (8), is converted into an electric signal, is amplified by the amplifier 9, and reaches the output terminal 10.

Figure 5 shows the output terminal 10 of a conventional example having the configuration shown in Figure 4.
This is an example of the waveform for one rotation of the disk. 20 is a DC component fluctuation waveform caused by disk warping, uneven reflectance, etc., 21 is a waveform example of the rotation start position mark 5, and 22 and 23 are waveform examples of noise caused by scratches and dust on the disk. be. When noise of the same level appears in the same direction as the rotation start position mark 5 as in this waveform example, it is difficult to detect it separately. Further, the width of the noise waveform may be comparable to the width of the rotation start position mark 5.

The present invention eliminates noise caused by scratches and dust when detecting the rotation start position mark described above, and also removes noise caused by warping of the disk, uneven reflectance, etc.
The present invention provides an optical recording/reproducing device having a rotation start position mark detector that detects a stable rotation start position mark by removing DC fluctuations.

The configuration of the present invention will be explained below based on the drawings.
FIG. 6 shows a configuration diagram of an embodiment of the rotation start position mark detector of the present invention. In Figure 6, the fourth
Components that are the same as those in the figures are given the same numbers and detailed explanations will be omitted. 1 is a disk, 2 is a guide track portion, 5 is a rotation start position mark, and 6 is a disk motor. The rotation start position mark 5 is detected by a first detector composed of a light source 7 and a light receiver 8, and is converted into an electrical signal and output. On the other hand, a second detector consisting of another set of light sources 30 and a light receiver 31 is connected to the first detector.
It is installed on the same radial direction as the detector and very close to it, and outputs the DC fluctuation due to the reflectance and warpage of the disk near the rotation start position mark 5. Furthermore, if scratches or dust adhere to the circumference of the rotation start position mark 5 and noise occurs in the output of the first detector that detects the rotation start position mark 5, the Noise also occurs in the output of the second detector provided in the second detector.

Next, the output of the first detector (Fig. 6a)
and the output of the second detector (Fig. 6b), respectively.
The signal is input to DC amplifiers 9 and 23, and the output thereof is input to a differential amplifier 33. In the differential amplifier 33, the first
DC fluctuation components due to warpage and reflectance of disk 1 output from the second detector and the second detector as well as noise caused by scratches and dust are removed.
Rotation start position mark 5 detected by the first detector
Only the waveform of is outputted from the terminal 34.

FIG. 7 shows the above waveform diagram. Figure 7a is the first
20 is the output wave of the detector (light source 7 and receiver 8 in Figure 6), and as in Figure 5, 20 is the DC component fluctuation waveform due to disk warpage and reflectance unevenness, 21
22 and 23 show the waveform of the rotation start position mark, and the noise waveforms caused by scratches and dust. FIG. 7b shows the output waveform of the second detector (light source and receiver 31 in FIG. 6), 40 is the DC component variation form, 41,
42 indicates a noise waveform. FIG. 7c shows the waveform of the output terminal 34 of the differential amplifier 33, and shows only the waveform of the rotation start position mark 21 which is output after DC fluctuations and noise have been removed.

As described above, according to the present invention, the first detector that detects the rotation start position mark and the second detector that does not detect the rotation start position mark are provided, and by making a difference between them, It is possible to eliminate the effects of disc reflectivity unevenness, warping, etc., as well as the effects of scratches and dust, and it is also possible to detect only the rotation start position mark, so this optical recording and reproducing device is equipped with a rotation start position mark. can be operated stably. Also, the output of each detector
Passing it through a DC amplifier is also effective in preventing the occurrence of sag in the rotation start position mark signal.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of a disk equipped with a guide track and a rotation start position mark, Fig. 2 is a partially enlarged sectional view of the guide track shown in Fig. 1, and Fig. 3 is a rotation start position shown in Fig. 1. Enlarged cross-sectional view of the marked part,
FIG. 4 is a configuration example diagram of a rotation start position mark detector, FIG. 5 is a waveform example diagram of the detector shown in FIG. 4, and FIG. 6 is an embodiment of the rotation start position mark detector according to the present invention. FIG. 7 is a waveform example diagram of the detector shown in FIG. 6. DESCRIPTION OF SYMBOLS 1... Disk, 2... Track part, 5... Rotation start position mark, 7, 30... Light source, 8, 31
...Photoreceiver, 9,32...DC amplifier, 33...Differential amplifier.

Claims (1)

[Scope of Claims] 1. An optical system having a disk having concentric or spiral guide tracks and a rotation start position mark for detecting one rotation of the disk, and a detection means for detecting the rotation start position mark. In addition to the first detection means for the rotation start position mark, a second detection means is provided at a position where the rotation start position mark is not detected, and the first detection means and the second detection means 1. An optical recording/reproducing apparatus characterized in that a rotation start position mark is detected from the differential output of the . 2. Claim 1, characterized in that the second detection means is provided in the same radial direction as and in the vicinity of the first detection means for detecting the rotation start position mark.
The optical recording/reproducing device described in 2.