JPH054136Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to an improvement in the pregroove of a recordable optical disc.

(b) Conventional technology A laser beam from a semiconductor laser is focused on a disk using a tellurium-based metal with a low melting point as a recording film to form recording pits of approximately 1 μφ during recording, and the power of the laser beam is reduced during reproduction. Optical disk systems have been proposed and are being put into practical use that are capable of reproducing and writing additional signals by irradiating recording pits and receiving the reflected light. This optical disk usually has a diameter of 30 cm and a track pitch of about 2 μm, and can record video information for about 30 minutes.

However, while forming recording tracks at arbitrary addresses on a plain optical disk, in order to ultimately continuously form recording tracks with a pitch of 2 μm, a large and highly accurate recording device is required, which increases costs. do not have.

Therefore, in order to make the recording track constant and continuous and to ensure address continuity, a spiral guide groove (pre-groove) is usually formed in advance on the optical disk. Note that address signals are multiplexed in this guide groove at a field period in order from the starting end to enable searching during recording and reproduction. The guide grooves are formed on the master disk using a high-precision, large-sized cutting device, similar to the formation of the master disk of a playback-only video disk record. A replica disk is formed from the disk master disk on which the guide grooves are formed, and a write-once optical disk on which a recording film is formed is formed using the replica disk as a mother disk.

However, when a moving image is additionally recorded using such an optical disc, FM video information and FM audio information are additionally recorded except for the address track. For video information, there is no problem because the address track is located in the vertical blanking period, but for audio information, the FM modulation carrier is missing for each address track period in the field period, which causes noise in the FM demodulation output. becomes.

Therefore, in order to remove this noise, a hold circuit is usually provided to hold the audio signal level constant during the address track reproduction period.

(c) Purpose of the invention Therefore, the present invention proposes a new and effective optical disc that reduces noise without providing this hold circuit.

(d) Structure of the invention The invention makes it possible to add a frequency multiplexed signal consisting of FM video information and FM audio information to a pregroove formed by continuously forming a guide track and an address track in a spiral shape. A distinctive feature of optical discs is that they record FM audio carriers on the address track in a frequency multiplexed manner.

(E) Embodiment The present invention will be described below according to an embodiment illustrating the invention.

First, FIG. 1 is an explanatory diagram schematically showing the pregroove near the address area formed on the optical disc of this embodiment, and FIG. 2 is a waveform diagram of video information and audio information corresponding to the address area. , 3rd
The figure is a circuit block diagram for forming a pregroove.

In the optical disk D of this embodiment, 1
A pregroove consisting of a groove-shaped guide track GT and a pit-shaped address track AT is continuously formed in a spiral shape so that video information for a frame can be recorded. The address track
The AT is formed intermittently in correspondence with a specific line in the vertical blanking period in the field period, and as a result, as shown in FIG. 1, the address area AE formed by the address track AT has a diameter of It will be distributed radially in the direction. Note that each recording period of the address track AT is two horizontal synchronization periods.

Therefore, when frequency multiplexing recording of FM video information and FM audio information is performed later, the guide track is
Records will be made only on GT.

In order to form a spiral pregroove, this embodiment employs the address track recording circuit shown in FIG. 3 in a large categorizing device for recording an optical disk master.

First, the video signal generation circuit 1 generates a blank video signal having no video information. This blank video signal is a signal in which the entire video period is in a blanking state, and is a signal containing only a synchronization signal.

Further, the address signal generation circuit 2 generates a binary address signal in synchronization with two predetermined horizontal synchronization periods during the blanking period of the blank signal.

The blank video information and the address signal are multiplexed in a superimposition circuit 3, and the resulting multiplexed signal is subjected to FM modulation in an FM modulation circuit 4.

The oscillation frequency of the oscillation circuit 5 is set to 1.8MHz, which corresponds to the modulation carrier frequency of the FM audio information, and generates an oscillation output corresponding to the non-signal audio information.

The FM modulation output including the address signal and the 1.8 MHz oscillation output are frequency multiplexed in the multiplex circuit 6 and supplied to the gate circuit 7. This gate circuit 7 is
It is intermittently opened only during the address track recording period.

Therefore, the optical modulation means (not shown) which uses this gate output as a control input intermittently records the address track AT on the master disk at the field period.
The light modulation means normally stops light modulation when no control signal is input, and during a period when no gate output is generated, the laser beam is continuously irradiated to form a groove-shaped guide track GT.

In the reproduced video information A and reproduced audio information B obtained by reproducing this address track, an address signal appears on the video information side and silence information appears on the audio information side, as shown in FIG.

Optical disc D obtained by duplicating a master disc on which pregrooves have been recorded in advance as described above.
is attached to a video disc recorder with a simple configuration, and video information and audio information are recorded using FM modulation from a desired address. As a result, video and audio signals and address signals are quickly recorded on the track.

When reproducing an optical disc recorded in this way, the carrier phase of the reproduced FM audio information becomes discontinuous before and after the address signal recording period, and pulse noise is generated in the FM demodulation output, but the noise generation period is Because it is short, the harsh sound is reduced.

(F) Effects of the invention Therefore, according to the invention, there is no carrier dropout condition associated with address track regeneration, no hold circuit is required, and pulse noise before and after the address track regeneration period occurs because the period of occurrence is short. Doesn't cause any harshness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing a pregroove near the address area formed on the optical disc of this embodiment, and FIG. 2 is a waveform diagram of video information and audio information corresponding to the address area. FIG. 3 is a circuit block diagram for forming a pregroove. Explanation of main drawing numbers, AT...address track,
CT...Guide track.

Claims (1)

[Claims for Utility Model Registration] An optical system that allows a frequency multiplexed signal consisting of an FM video signal and an FM audio signal to be added to a pregroove formed by continuously forming a guide track and an address track in a spiral shape. 1. An optical disc characterized in that address information and an FM audio carrier are frequency-multiplexed recorded on the address track when forming the pregroove.