JPH0323976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for irradiating a light spot onto an information storage medium in which an information signal and an address signal are recorded along a spiral or concentric track of multiple revolutions;
The present invention relates to an information recording medium access method for accessing a desired track at high speed.

A method of searching for a desired track from an optical video disk on which video signals are recorded concentrically or spirally at high density on a rotating disk is described in detail in, for example, Japanese Patent Laid-Open No. 51-21727. That is, an address signal is inserted into a vertical blanking period of a video signal, and this composite video signal is recorded on a disk in a spiral or concentric pattern. During playback, an arbitrary track is tracked, the composite video signal recorded on that track is played back, the address signal inserted in the vertical blanking period of the video signal is extracted, and the address signal specified from the outside is read. and the detected address signal. If the designated address number and the detected address number do not match, the playback device is moved in the radial direction of the disc until they match. For example, in fields where high-speed access is required, such as optical file memory, searching tracks one by one may require a diameter of 30 mm.
If information is recorded on a cm disk with a track spacing of 2 μm, 5×10 ⁴ tracks will be recorded, and it is required to search for one track within 100 msec.

Conventionally, as a device for searching arbitrary tracks at high speed, there is, for example, a computer magnetic disk device. This device is equipped with a dedicated disk for detecting the position of the magnetic head. On this disk dedicated to head position detection, magnetic tracks approximately 60 μm wide are arranged concentrically. The magnetic head for reading out a disk dedicated to head position detection and the head for reading out another disk on which information is recorded are moved together in the radial direction over the respective disks by a voice coil. Furthermore, in order to move the reproducing magnetic head to the desired information track, the voice coil is controlled using a signal from the head position detecting magnetic head.

FIG. 4 shows magnetic tracks 101, 102, 103, 104,
105 shows the shape of the head 100, and also shows a search signal 107 from the magnetic head when the head moves in the radial direction. This search signal 10
Currently, in magnetic disks, the positioning of the moving part including the magnetic head is controlled using a voice coil with an accuracy of about 10 μm.

By the way, a small light spot is irradiated onto the surface of a conventional optical video disk (bandwidth: 4MHz) on a 30cm disk with a track width of 2μm and 5× ¹⁰⁴ tracks of video signals (bandwidth: 4MHz), and the resulting reflected signal is used to control the voice coil. When I try to control it, the average pit length where the video signal on the track is recorded is approximately
50m using a voice coil because it is 2μm
High-speed access on the order of seconds is impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an access method that eliminates the conventional disadvantage of not being able to perform high-speed access and allows a high-speed search for a desired track.

The present invention will be described in detail below with reference to Examples.

FIG. 1 shows an example of an information storage medium used in the present invention, and shows tracks recorded on a rotating disk. 1 is a rotating disk, 2, 2'
3 is a track group that is a collection of multiple tracks on which address signals and video signals are recorded;
3' and 3'' are identification tracks for identifying the track groups 2 and 2', and 4 is the rotation center of the rotating disk.Here, in the case of a circular information storage medium, the track refers to a concentric track that rotates many times. or one spiral track that can be considered as a quasi-concentric track with multiple rotations.Identified tracks 3, 3', 3'' are track 3,
A signal different from the signals recorded in 3' and 3'', for example a DC signal, is recorded, and functions as a scale for identifying the track groups 2 and 2' during an access operation.

Figure 2a shows the tracks and playback data when a playback device passes over the disk in the radial direction of the disk, when the disk on which the tracks shown in Figure 1 are recorded is rotating at 1800 rpm. It shows the relationship between spots. In Figure 2a,
5, 5', 5'' are pits recorded electro-optically by video signals, and 6, 6', 6'' are pits 5, 6''.
5', 5'' is a track on which a video signal is recorded, and 7 is an identification track on which a DC signal is recorded.In order to record these signals in a form that can be optically reproduced, for example, As detailed in No. 34508, it can be recorded as a phase structure or an amplitude structure, where a phase structure is
The amplitude structure is recorded as a change in depth, and the amplitude structure is recorded as a change in reflectance or transmittance. 8 is a light spot for reproduction, and 9 is a moving direction of the light spot 8 for searching for a predetermined track. In Figures 1 and 2a, when the optical spot 8 is moved in the radial direction 9 with the disk 1 rotated, the signal detected by the photodetector of the reflected light from the optical spot 8 is shown in Figure 2b. It becomes like that. For example, if the pitch of a stored video signal is
Assuming that the speed is 5MHz and the disk rotation is 30Hz,
The moving speed of the optical spot 8 in the disk radial direction is
Set to 10cm/sec. Also, the recorded track width is
1 μm and the track spacing is 2 μm, the output signals 11, 11 of the photodetector obtained when the light spot crosses the tracks 6, 6', 6'' where pits 5, 5', 5'' are recorded by the video signal are ′,11″ is 5M
It is the product of the Hz signal and the 50KHz signal, that is, each of the output signals 11, 11', 11'' has about 100
A 5MHz pulse can be seen. On the other hand, the output signal 12 of the photodetector obtained when the light spot crosses the identification track 7 recording the DC signal is approximately 50KHz.
Only one pulse with a waveform corresponding to a period appears. Therefore, the track 6 on which the video signal was recorded,
6', 6'' and identification track 7, if the above signals 11, 11', 11'', 12 are passed through a 50KHz narrow band filter or low pass filter, a signal as shown in Fig. 2c is obtained. is obtained, and if this signal is further sliced along the dotted line shown in Figure 2c, the second
One pulse signal as shown in Figure d is obtained. That is, by detecting this pulse signal, it is possible to determine whether the light spot 8 has passed over the identification track 7, and by counting this pulse signal, the light spot can be quickly directed to a desired track group. Can be positioned. If you select an NTSC signal as the video signal, the pitch of approximately 7.5MHz is 5,
5', 5'' will be recorded on the disk.
In this case, the narrowband filter and slicer
In order to obtain pulses only from the identification track 7 that recorded the DC signal, the moving speed of the optical spot is 15
It is preferable that it is below cm/sec. A device for rapidly searching for a desired group of tracks from information recorded on a rotating disk using the pulses, and then searching for a track at a desired address is provided.
This will be explained using FIG. 2, FIG. 3, and FIG. In FIG. 3, 13 is a rotating disk. disk 1
As shown in FIGS. 1 and 2, the tracks recorded on tracks 3 are track groups 2, 2, and 3, in which pits 5, 5', and 5'' of video signals containing address signals are recorded.
2', and identification tracks 3, 3', and 3'' between which a DC signal is recorded.14
is a motor that rotates this disk 13 at 30Hz. 15 is a reproduction optical system, 16 is a reproduction optical system 1
This is a moving device that moves 5. As the moving device 16, for example, a voice coil used in computer magnetic disks can be used.
17, the moving device 16 can be mechanically braked at a predetermined location. When the drive circuit 17 is started by the start pulse 30, the reproducing optical system 15 is moved in the radial direction of the disk 13 by the moving device 16, and a signal as shown in FIG. 2b is output from the photodetector. This signal is passed through a circuit 19 consisting of a narrow band filter and a slicer as shown in FIG.
A pulse like this is obtained and supplied to the block counter 20, and this pulse is counted and used as a scale for identifying track groups. A comparator 22 compares the output of the block counter 20 and the output of the target block number register 21, and when they match, a signal is sent to the drive circuit 17 indicating that they match the desired track group. This signal mechanically brakes the moving device 16 to a stop within the target group of tracks. On the other hand, comparator 22
The signal from the tracker operates the tracking control circuit 28, and then the video signal during tracking is supplied to the video demodulation circuit 23, and the demodulated video signal is further supplied to the address detection circuit 25 via the switch 24. The address signal of the track on which the optical spot is located is detected. The address detection circuit can be implemented according to Japanese Patent Application Laid-Open No. 51-21727. The switch 24 is turned on by the signal from the comparator 22 that has passed through the delay circuit 31. The address detected by the address detection circuit 25 is compared with the output of the target address register 26 by a comparator 27, and a signal proportional to the difference is sent to the jump control circuit 25.
This signal drives the galvanometer mirror of the reproducing optical system, jumps the optical spot 8 to the track where the target address is recorded, and reads out the desired information. In addition, jump control circuit 2
9 controls the operation of moving the light spot from one track to another, for example:
It is detailed in Philips tech.Rev.33, 190-193, 1973, No.7.

The time required from when the brake is applied to the moving device 16 until the desired information is read is about 20 msec. On the other hand, the moving speed of the moving device 16 is the maximum
Since the speed is about 15 cm/sec, the average time required to search for desired information from a disk on which 54,000 frames of information are recorded with a track pitch of about 2 μm is about 0.5 seconds.

As explained above, according to the present invention, a desired track can be accessed at high speed. For example, in the case of a video disk, the average search time required to search for one frame of desired image information from among 54,000 frames of image information recorded concentrically or spirally on a rotating disk is about 0.5 seconds. is possible.

[Brief explanation of the drawing]

FIG. 1 shows an example of a recording information medium used in the present invention, and is a conceptual diagram of a track recorded on a rotating disk. FIG. 2 shows an example of a recording information medium used in the present invention.
An explanatory diagram of a method for detecting that a light spot has passed through an identification track, FIG. 3 is a diagram showing an example of a track search device implementing the present invention, and FIG. 4 is a diagram showing the relationship between the head and track of a magnetic disk and control signals. FIG.

Claims (1)

[Scope of Claims] 1. A multi-turn spiral or concentric track in which the information signal and the address signal are recorded as an array of pits in an optically reproducible form,
Using an information recording medium in which the tracks are divided into groups of multiple rotations, the irradiation position of the light spot is moved to the group containing the desired track based on a signal obtained from a scale for identifying the groups. After that, the difference between the address signal of the track on which the light spot is located and the address signal corresponding to the desired track is detected, and the irradiation position of the light spot is moved according to the difference to reach the desired track. An access method characterized by locating a light spot. 2. The scale comprises an identification track recorded on the information recording medium with a signal different from the information signal so as to distinguish between the groups, and a signal obtained when the optical spot passes through the identification track. 2. The access method according to claim 1, wherein the irradiation position of said light spot is moved to a group including said desired track based on said desired track. 3 comprising a first moving means for moving an optical system that irradiates the information recording medium with the light spot, and a second moving means provided within the optical system that moves the irradiation position of the light spot, The first moving means is driven based on a signal obtained from the scale, and the second moving means is driven based on a signal based on the difference.
3. The access method according to claim 1, further comprising driving a moving means. 4. The access method according to claim 3, wherein a voice coil is used as the first moving means. 5. The access method according to claim 4, wherein a galvanometer mirror is used as the second moving means.