JPS61252775A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To separate a sound signal band from a video signal band and to prevent their mutual interference by overlapping an address signal on a high frequency component side band wave area of video signal. CONSTITUTION:A frequency spectrum of an address signal 4 is positioned at an intermediate section of a spectrum of a video signal 3 and a spectrum of a sound signal 5, in a vertical blanking period of the video signal 3 and on a lower first side band wave area of the video signal 3 in view of frequency. Thereby, the mutual interference of the video signal 3, the address signal 4 and the sound signal 5 is prevented and a complete frequency difference between the video signal 3 and the sound signal 5 is provided and the separation thereof can be easily and characteristically maintained.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an optical system in which video information is written on a disk-shaped medium and the written video information is optically read out using a laser beam. The present invention relates to a digital recording/reproducing device.

Conventional technology In the case of so-called laser discs, an aluminum reflective film is formed on one side of a transparent glass disk, and a row of minute holes (image tracks) are formed in a spiral or concentric pattern on this reflective film. Video information (signal) in such a way
This is what was written.

The video signal is written in FM modulated form like a VTR,
A row of holes is created whose length in the longitudinal direction of the video track is modulated and at the same time in the spacing direction.

When a laser beam is irradiated perpendicularly from the side of a transparent plastic disc that does not have a reflective film, it will be reflected well where there is a reflective film, but there will be almost no reflection at the holes, so the intensity of the reflected light of this laser beam will be By detecting this, the video signal can be reproduced. Actual laser
In the case of a disc, a protective film that absorbs light, for example, is attached on top of the reflective film, and two discs are then glued back to back so that the protective films are in contact with each other to form an L-plate disc. In this way, different video information (signals) can be written on both sides of a single disc-shaped medium. In the case of laser discs, the video signal is stretched out in the time axis direction and recorded slowly to create a master disc. Product discs are mass-produced based on this master disc. Therefore, even if it takes time to produce the master disc and it costs a little more, one product disc can be produced at a low cost by producing a large number of product discs. However, it is impossible to record video signals from a television camera or television receiver on this laser disk, for example, as with a VTR at home.

On the other hand, there is also an optical disc on which video signals can be recorded and reproduced using a laser beam on a disk-shaped medium.

There are two types of optical discs of this type; one type allows recording, but once recorded information cannot be erased and new information can be re-recorded; DRAW Direct Read Af
The other type of optical disk is called a rewritable (erasable) type optical disk, in which previously recorded information can be erased and new information can be recorded. Both the write-once type and the rewritable type have almost the same shape and structure.

Taking a write-once optical disc as an example, its shape and structure will be explained with reference to FIG. groove 13 (for example, width 0.
8 μm.

A pitch of about 166 μm) is provided, and a recording film 1 is formed on it.
4 is formed. This groove 13 becomes a video signal recording track. Conversely, there is a method of recording in the downward direction (convex part) of the enlarged cross-sectional view of (A) between the grooves, but since it is the same thing, let's record the bottom of groove 13 (concave part). The case of recording will be explained. On the video signal recording track of the optical disc 11, an address signal for specifying the track is mechanically and digitally written in one or more locations on the circumference in the form of a code signal. A cross section (enlarged view) along the video signal recording track of the location where the address signal is written is shown in (b). An address signal 15 is mechanically etched into the bottom of the groove of the substrate 12, and the depth of this etching is approximately the same as the thickness of the recording film 14.

The surface of the recording film 14 may be coated as necessary (for example, the surface of the recording film 14
A protective film (not shown) may be added. In an actual optical disc, there are two disks with the same structure (or one is just a transparent plastic disk).
are glued together via a spacer with the side with the recording film facing inside. The laser beam is an optical system (
(not shown) is controlled by a focus servo so that the bottom of the groove 13 in FIG. 2(a) is always in focus. If the power of the laser beam is sufficiently large, the recording film will be altered or sublimated by the heat at the location where the strong light hits, changing the reflectance of the light. During reproduction, a recorded video signal can be reproduced by applying a weak laser beam that does not alter the recording film and detecting changes in the amount of reflected light due to changes in reflectance. In the case of a rewritable optical disk, a film whose reflectance changes reversibly depending on the way the laser beam is irradiated or a film which is magnetized is used as the recording film. Optical recording that uses a magnetized film is called magneto-optical recording.The recording film is heated and cooled in advance to a Curie point or higher in a uniform magnetic field in one direction to uniformly magnetize the film, and during recording, it is magnetized in the opposite direction. This is a recording method that takes advantage of the fact that by applying a laser beam in a uniform magnetic field, the laser beam is strongly applied and the magnetization of the recording film is reversed only when it exceeds the Curie point. In this case, the signal is reproduced by using the Kell effect and detecting the rotation of the plane of polarization. In the case of a laser disc, the video signal can be written slowly over a sufficient amount of time when creating the master disc (writing video information), so it is possible to record as finely as possible during playback.

A laser disc is usually a disc with a diameter of about 300 mm.
The video information (signal) is tightly written in a spiral shape from the innermost circumference of about 100 mm to the outermost circumference, which is close to the maximum diameter of the disc. There are two methods for writing video information: constant angular velocity (CAV) and constant linear velocity (CLV), but in either method, the device rotates at 30 Hz (one frame per rotation) near the innermost circumference.

As mentioned above, when reproducing video information (signal) from a laser disc, it is possible to reproduce a frequency band as high as the maximum reproducible limit, so for example, the curve marked as outermost characteristic 1 in Figure 1. It is possible to obtain a custom equivalent reproduction video frequency at the innermost circumference of the . On the other hand, in the case of write-once optical discs (almost the same applies to rewritable optical discs), for example, they are disc-shaped with an outer diameter of about 200 mm,
The innermost circumference diameter is about 1QQmm, and the video tracks are provided in a concentric circle up to the maximum diameter. In this case, recording and playback video frequency characteristics when the disk is rotated at a constant angular velocity (CAV) of 3QHz during both recording and playback (FM modulated, regarding writing to and reading from the disk) )
An example of this is shown in FIG.

In FIG. 1, the horizontal axis represents the frequency (MHz), and the vertical axis represents the recording/reproducing output signal level, both of which are plotted on a linear scale.

In the case of write-once type (same as rewritable type) optical discs, the recording of signals depends on the strength of the light, but instead of being written directly by light, when the light is irradiated onto the recording film, the light turns into heat and is then written. Since this is performed, a delay inevitably occurs, which deteriorates the characteristics. Therefore, for the same recording linear velocity, it is inevitable that recordable (or rewritable) optical discs will have worse recorded and reproduced video frequency characteristics than laser discs. As long as the disk (disc) rotates at a constant angular velocity (uniform disc rotational speed), the recording (reproduction) linear velocity is highest at the outermost periphery (track), and the recording (reproduction) linear velocity decreases toward the inner periphery. Therefore, the recorded/playback video frequency characteristics are best at the outermost circumference and worst at the innermost circumference. FIG. 1 shows an example of the maximum characteristic 1 and the innermost characteristic 2.

Problems to be Solved by the Invention In the case of laser discs, even on the innermost periphery, the characteristics of the outermost periphery of the write-once optical disc shown in FIG. The signal is written at an equivalent frequency such that In other words, the video signal is 7.5MHz sync chip (synchronous peak) and 178.2MHz Bedestar.

The Nippon Television Standard (NTSC) video signal is directly modulated into the white peak 9.3MHz FM signal. Assuming that the upper limit of the frequency band in the base band (original signal without FM modulation) of an NTSC video signal is 4.2 MHz, the frequency spectrum when FM modulated is 4 MHz (8.2 MHz equivalent to a pedestal).
MHz-4,2MHz) to an upper limit of 13.5MHz
(white peak equivalent 9.3 MHz + 4.2 MHz). However, in the case of FM modulation with a small modulation index as in this case, most of the energy is concentrated in the upper and lower first sidebands (sidebands), so the second and higher sidebands can be ignored. \do. FIG. 3 schematically shows an equal image recording FM video signal spectrum 21 in the case of a laser disc. The horizontal axis is the frequency (MHz), but the vertical axis is a completely schematic diagram. The central part of the video signal spectrum 21, where the baseband video signal is a scale, is in the deviation range (frequency shift), and what frequency the sync tip, pedestal, white peak, etc. are at. It shows whether it is compatible. The portion extending outside this deviation range indicates the spread of the side band spectrum. In addition, in the case of a laser disc, in addition to the video signal 21, the audio signal 2
Channel 22 is also FM modulated (center frequency 2.30
1136 MHz and 2.812499' MHz) and are written superimposed on the video signal 21. On the other hand, in the case of write-once type (same as rewritable type) optical discs, the frequency band that can be recorded and reproduced is narrower than that of laser discs, as mentioned above, so it is not possible to select the FM modulation frequency of the video signal as shown in Figure 3. .

Conventionally, one of the solutions to this problem is the so-called color under system (chromaticity signal low range Some recording format numbers (conversion method) are used.

That is, the video signal of the pace band before FM modulation is separated into a luminance component and a color component, and the luminance component is, for example, 4.4 MHz for the signal/chip and 4.75 MHz for the pedestal.
z, white peak of 5.5 MHz as an FM modulated video signal 23, and simultaneously superimposes the color component 24.
is low frequency converted to, for example, a center frequency of 63 BKHz, and the audio signal is further recorded as a two-channel FM signal 25. Of course, it is possible to record using such a color/under system, but on the other hand, color/under
The disadvantages of the under-one type, namely, the recording band of color signals in particular is narrow, and therefore the waveform characteristics are extremely poor, cannot be solved.

As another means, as shown in FIG. 5, the video signal 26 may be of a type whose modulation frequency is slightly lower than that of the laser disc (for example, 5.5 MHz for the sync tip, 7 MHz for the pedestal).
, white peak 8.2 MHz), and the aforementioned address signal 27 is set at 500 KHz-1 MHz.

In this case, since the video signal is directly FM modulated, it is possible to obtain a playback quality superior to that of a consumer VTR, similar to a laser disc, but the gap between the video signal band 26 and the address signal band 27 is small, and the audio signal band is provided in that gap. It's difficult.

Means for Solving the Problems An object of the present invention is to provide a new means that solves the problems of the video signal recording format in the write-once type or rewritable optical disc. Focusing on the fact that it does not exist during the planning period,
The address signal is configured to exist only within the vertical blanking period, and this address signal is configured to overlap with the high-frequency component sideband region of the video signal.

By making the active address signal overlap the high-frequency component sideband region of the video signal, the audio signal band and the video signal band are separated and their mutual interference is prevented.

Example The present invention will be described with reference to the embodiment shown in FIG.

FIG. 1 shows the recording and reproducing (frequency ) is a diagram showing an example of the characteristics (the outermost characteristic 1 and the innermost characteristic 2) and the signal recording band format (video signal 3, address signal 4, and audio signal 5) of the embodiment of the present invention. The recording format of video signal 3 is exactly the same as the one shown in Figure 5.If possible, I would like to increase the modulation frequency to the level of the laser disc format shown in Figure 3, but it is not possible to use a write-once (or rewritable) optical disc. Since this is unreasonable in terms of the recording/reproducing (frequency) characteristics, it is set to the level shown in FIG. 1. Even so, there may be cases where the upper first sideband wave hardly passes through.

In that case, it is necessary to pay sufficient attention to distortion correction. As mentioned above, the address signal 4 must be mechanically written (engraved) into the groove at the stage of manufacturing the transparent plastic substrate of the disk, so it cannot be made isometrically at a very high frequency. Address signal 4 is a so-called pi-phase mark (
There is a lock between the bits based on the reference, and a reversal always occurs at the reference clock, and a "0" bit has no reversal other than the reference clock phase before and after it, and a "1" The coding method is such that the bit is inverted once exactly in the middle of the reference clock phase, and signal energy is concentrated at the reference clock frequency and its half frequency. The rotation of the disk is controlled so that the address signal 4 comes during the vertical blanking period when recording the video signal 3. During the vertical planking period, the video signal 3 does not contain any color signal components other than the burst signal, and therefore does not contain any high frequency components (when considering the base band).

In other words, the FM modulation band to be written to the disk is synchronized.
Most of the signal energy is concentrated around 5.5 MHz, which is equivalent to the chip, and 7 MHz, which is the pedestal level. For example, if the reference clock frequency of address signal 4 is chosen to be 2.8 MHz, the signal energy will be 2.8 MHz.
and concentrated at 1.4MHz.

In this way, the spectrum of the video signal 3 (vertical blanking period) will be between the 2.8 MHz double and triple harmonics, and mutual interference between the video signal and the address signal can be prevented. The audio signal (2 channels) 5 is recorded by being superimposed on the video signal 3 in the form of an FM signal having center frequencies at 0.7 and 1 MHz, for example.

Effects of the Invention As described above with respect to the embodiment shown in FIG. By locating the frequency within the lower first sideband band of the video signal 3, the video signal 3, the address signal 4, and the audio signal 5 are
This has the effect of preventing mutual interference between the two, and providing a sufficient frequency difference between the video signal 3 and the audio signal 5, making it easy to separate them and maintaining good characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the recording/reproducing characteristics of a write-once type (or rewritable type) optical disc to which the present invention is applied and a schematic spectrum diagram of an embodiment of the present invention. A diagram explaining the structure of a rewritable optical disc. Figure 3 is a signal spectrum diagram of a so-called laser disc. Figure 4 is a signal spectrum diagram of a conventional consumer VTR. Figure 5 is a signal diagram of a conventional write-once optical disc. It is a spectrum diagram.

Claims (1)

[Claims] Optical recording and reproducing that records and reproduces video signals using a light beam on a rotating disk-shaped write-once (DRAW) or rewritable (erasable) medium so as to form multiple concentric recording tracks. In the device, the video signal is
When recording in the form of a modulated signal and simultaneously recording an audio signal in the form of an FM modulated signal in the low range of the recording band, the address signal for identifying the recording track is set to the FM frequency deviation range (deviation range) of the video signal. At the time of manufacturing the disc-shaped recording medium, the address signal is written in advance in the middle part of the audio signal recording band in a form that overlaps with the lower first sideband band of the FM modulation of the video signal, and the writing position of the address signal is An optical recording/reproducing apparatus characterized in that the rotational phase of the disc-shaped recording medium is controlled during recording of the video signal so that the rotational phase of the disc-shaped recording medium is within a vertical blanking period of the video signal.