JPS6318253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disk-shaped record carrier (optical disk) used in an optical recording/reproducing device such as a video disk.
It is related to the structure of

As an optical recording/reproducing device, for example, an optical disk coated with or vapor-deposited with a photosensitive material is rotated, and the optical disk is irradiated with a minute spot of light from a laser light source or the like, which is focused to a diameter of 1 μm or less, and the light is recorded. By modulating the output intensity with the recording signal, video signals and digital signals can be recorded in real time on the optical disk as changes in refractive index such as phase changes due to unevenness, changes in light and shade, and changes in reflectance and transmittance due to hole formation, etc. An apparatus has been proposed that is capable of recording such information and reproducing the recorded information by detecting changes in optical characteristics. In such an apparatus, in order to achieve high recording track density and partial recording, it has been considered to form groove-shaped guide tracks in advance on the optical disk. In order to search for optical disks with such groove-shaped guide tracks, address information is required for each track. This address information can be preformed together with the grooved guide track. When recording information on such an optical disk with a guide track in which address information is provided for each track, it is necessary to control so that information is not recorded in the address area of each track. Furthermore, when reproducing tracks and reading information, it becomes necessary to distinguish between address areas and information areas. To distinguish address signals from information signals,
By inserting very different signal patterns, it is also possible to extract the address signal from the track reproduction signal. However, in this method, if the frequencies of the address signal and the information signal are close, it becomes difficult to separate the two signals. Furthermore, when performing a track search by transporting minute spot light at high speed, detection of the start end of an address area becomes unstable, so this method cannot be said to be appropriate. When recording digital signals on an optical disk such as the one described above, it becomes necessary to input a number of address signals into one track for even faster searching. Even during high-speed search, it is necessary to reliably detect the start end of such an address area and reproduce the address.
The address information is arranged in the radial direction of the disk in an arc shape forming a certain angle with respect to the center of the disk. This arc-shaped part is placed in a part other than the information track area, for example, the start end detection mark (index mark) of the address area is placed on the inner periphery of the track area.
form. If this index mark is formed as a groove structure similar to the groove-shaped guide track, the position of the address area can be formed with high accuracy when stamping the disk. Further, a rotation start position mark is required on the optical disk in order to match the phase of the information signal with the motor that rotates the optical disk. Furthermore, when recording digital signals on such an optical disk, the track may be divided into several sectors and recorded. In such a case, a sector mark indicating the starting position of each sector is also required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk and a detection method therefor that can accurately detect the position start end in the track direction in an optical recording/reproducing apparatus as described above even during high-speed searching.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an embodiment showing the structure of an optical disk of the present invention. Figure 1a shows a plan view of the optical disc. Since such disks are mainly used to record digital signals, 1
The four tracks are divided into four sectors _S1 to _S4 . This disk has two address areas 1 on each concentric track, and an address start detection mark (address mark) 3 is formed on the circumference of the optical disk within an arc having the same angle as the address area. 4 is a sector start end detection mark. In the case of FIG. 1, marks are formed at four locations because it is divided into four sectors. 5 is a rotation start end detection mark. This is used to control the rotational phase of the disk motor that rotates the optical disk. In this way, the optical disc is divided into an information signal track area (including an address signal area) 6 and an index mark area 7. FIG. 1b shows a sectional view along the track of the index mark area 7. FIG. The groove structure of such an index mark is shown in FIG. 2a. Reference numeral 8 represents one index mark, and guide grooves 9 having the same pitch as the information track area are arranged in the radial direction within a circular arc having an angle α necessary for detecting the starting position. By doing so, index marks can be formed at accurate positions at the same time in the same process as cutting the guide groove tracks of the optical disk. Therefore, an enlarged view of the portion 10 where the index marks 3, 4, and 5 of FIG. 1 are lined up is shown in FIG. 2b. FIG. 3a shows an example in which the index mark 8 is formed as a pit 11 having an uneven shape in the track direction. Similarly, FIG. 3b is an enlarged view of 10 when three index marks are arranged in a row.

In this case as well, a pit groove is formed within a circular arc having an angle α necessary for detecting the starting end. In order to stably detect the index mark as described above even during high-speed retrieval, a detection system for detecting the index mark area 7 is required separately from the laser light source for reading out the information signal track area 6. However, it is not necessary to focus the light beam on each track of the index mark 8, and the purpose of detecting the start point can be achieved by detecting only the change in reflectance of the index mark 8 as a whole. Therefore, an inexpensive incoherent light detection system using a light emitting diode and a phototransistor can be used. FIG. 4 is a diagram showing an optical recording/reproducing apparatus equipped with a detector for index mark areas. The light driven by the laser beam drive circuit 12 passes through the diaphragm optical system 13 and is irradiated onto the optical disk 2 by the diaphragm lens 28, where it enters the information track area 6.
Read the signal from. A signal of the reflected light from the optical disk 2 is reproduced using a photodetector 14. 1
Reference numeral 5 denotes an address reproducing circuit that reads out only the address signal from the reproduced signal. 16 is a disk motor for rotating the optical disk, and 17 is a linear motor for moving the optical disk 2 in the radial direction for searching. The index area 7 is detected using a photodetector 18 using a light emitting diode and a phototransistor, and is input to a signal processing circuit 19. The reproduced rotation start position mark 5 is the disk motor 16
The address start position mark 3 provides the address reproducing circuit 15 with timing for reading the address. Further, the sector start end detection mark 4 controls the timing of reproduction and recording of the information track of each sector. The circuit configuration of the signal processing circuit 19 is shown in FIG. Incoherent light emitted from the light emitting diode 20 is emitted onto the index mark area 7 on the optical disk 2. When the index mark is irradiated with light, the amount of reflected light changes, and the photodiode 21 detects this change. The detection signal is inputted to an amplifier 22, and then inputted to a bandpass filter 23 to remove the influence of changes in light amount due to surface wobbling of the optical disk 2. Further, a comparator 24 converts the detection signal into a pulse. Here, FIG. 6 shows waveforms at various parts of the circuit configuration. Figure 6a shows index mark area 7.
2 shows a cross-sectional view in the same circumferential direction. When light falls on the index mark, it is scattered, so the output of the phototransistor has a small amplitude as shown in FIG. 6b. FIG. 6c shows the waveform of the comparator output c. The index pulse c output from the comparator 24 is input to the retriggerable multivibrator 25, which outputs a signal with a pulse width of T<t<2T from the rising edge of the pulse. (FIG. 6d) Here, T represents the period when index marks are continuously formed as shown in FIG. 6c. This output is input to the D-flip-flop 26, latched by the index pulse c clock mentioned above, and output to the _Q1 terminal (FIG. 6e). Furthermore, it is input to the next stage D-flip-flop 27, and the output shown in FIG. 6f is obtained at the output terminal _Q2 . And the output c...
The AND circuit 30 obtains the AND output of , and outputs it as a sector start detection signal (FIG. 6g). Further, the logical product output of the outputs c, e, and f is obtained by the AND circuit 31 and outputted as a rotation start end detection signal (h in FIG. 6). Furthermore, the output c・e・
The logical AND output of f is obtained by the AND circuit 32 and is obtained as an address start end detection signal (FIG. 6i).

As described above, by forming the index mark on the inner circumference of the optical disk 2 using the same process as the guide groove in the information track area, it is possible to easily obtain a stable information position detection signal even during high-speed searches. .

These index marks can not only stably detect information positions, but also control the timing of track jumping during searches. For example, when information is recorded in the form of a spiral track, it becomes necessary to repeatedly reproduce tracks of the same circumference. At times like this, 1
It is necessary to jump the track every rotation. The above-mentioned rotation start end position detection mark 5 may be detected at the timing of this jumping.
However, a time delay is required between detecting the rotation start point and starting the pick-up of the optical head for reading information and performing jumping. Therefore, as shown in FIG. 7, the mounting position of the photodetector 18 for detecting the rotation start position detection mark 5 is shifted by an angle β. By doing this, jumping can be performed so that the information of one track can be stably reproduced from the beginning of the address signal. The aperture lens 28 of the optical head starts jumping earlier by an angle β as shown in FIG.
By performing jumping, the information can be replayed stably from the beginning. FIG. 8 shows waveforms at various timing portions during jumping. FIG. 8a shows the detected pulse waveform of the index mark, and FIG. 8b shows the reproduced address signal at the beginning of information. FIG. 8c shows the rotation start detection pulse, but since the mounting position of the index mark photodetector 18 is shifted by β, the actual timing is as shown in FIG. 8d. d
Jumping is activated by the signal. Figure 8e
represents the amount of movement of the optical head in the disk radial direction. By doing this, jumping is completed in 29 sections, so that the optical head can stably reproduce information from the beginning.

When information is to be recorded on both sides of the optical disc 2, it becomes necessary to detect the front and back sides of the disc. Even in such cases, index marks can be used effectively. Index marks with different groove structures are formed on the front and back sides. For example, by making the number or width of marks different, it is possible to detect the front and back sides using a method similar to the circuit configuration described above. Furthermore, by forming different index marks on different disks, the type of disk can also be identified. Detecting the front and back sides and types of discs using index marks has the following advantages. There is no need to illuminate a laser light source for reading information tracks and to search for tracks containing this information. Furthermore, if different reproducing light power and recording power are required for each optical disk, the optimum optical power can be selected for each disk without irradiating laser light.

As explained above, by using the index mark of the present invention, the rotation start position, address start position, and sector start position can be detected stably even during high-speed searches. Furthermore, since this index mark can be formed in the guide groove of the optical disk or during cutting of the information bits, it is possible to use the same accurate process as the conventional method. Furthermore, it is possible to identify the occurrence of the track jumping start timing, the front and back sides of the disk, and the type without using a laser light source.

[Brief explanation of the drawing]

FIG. 1a is a plan view showing an outline of an optical disk according to an embodiment of the present invention, b is a sectional view taken along the track direction, FIG. 2a is an enlarged perspective view of the main parts, and b is an enlarged plane view Fig. 3a is an enlarged perspective view of the same main part, b
is an enlarged plan view of the same, FIG. 4 is a block diagram of a playback device using the optical disk of the present invention, FIG. 5 is a block diagram of the main parts, FIG. 6 is an explanatory diagram of the same operation, and FIG. FIG. 8 is a diagram showing an example of the mounting position of the index mark detector, and FIG. 8 is an operation explanatory diagram showing the processing system for the output from the index mark detector. 1...Address area, 2...Optical disk, 3...Address start end detection mark, 4...Sector start end detection mark, 5
... Rotation start end detection mark, 6... Information signal track area, 7... Index mark area, 20... Light emitting diode, 21... Photo transistor.

Claims (1)

[Scope of Claims] 1. In an optical disk having concentric or spiral tracks, a rotation start detection mark for detecting one rotation of the optical disk, and an address area for each sector that divides each track into sectors. 1. An optical disk characterized in that an address start detection mark for detecting the position of an address is formed in an area other than an information signal track area with a concave-convex phase groove structure. 2. An optical disk according to claim 1, characterized in that the rotation start end mark and the address start end detection mark are formed with a phase groove structure that allows it to be identified that they are different marks. 3. An optical disk according to claim 1, characterized in that rotation start position marks of different phase groove structures are formed on the front and back sides of the optical disk to detect the front and back sides of the disk. 4. An optical disk according to claim 1, characterized in that a rotation start position mark of a phase groove structure that differs depending on the type of optical disk is formed.