JPH0731317B2 - Optical recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording method suitable for use in recording of a video disc, an optical disc for recording data, and the like.

[Outline of Invention]

The present invention is an optical recording method suitable for use when recording on a recording medium such as a video disc or an optical disc for data recording, which uses a gas laser device for oscillating a multimode laser as a laser source and modulates the laser. In an optical recording method for recording data on a recording medium using an acousto-optic modulator, a beat frequency between longitudinal modes of a laser is set to _L
[Hz], the carrier frequency of the acousto-optic modulator is c [Hz], and the recording frequency band is 0 to [Hz], | m · _L− n · c | ≧ (where m and n are integers) ) The beat frequency _L between longitudinal modes and the carrier frequency c are selected so as to satisfy the equation (4), so that an unnecessary spectrum signal does not occur in the recording frequency band and good recording can be easily performed. It is a thing.

[Conventional technology]

Conventionally, when manufacturing a master disk for an optical disk such as a video disk, for example, a glass master disk having a photoresist coated on the surface is irradiated with laser light to expose a portion corresponding to a pit portion, and then developed to form a pit portion. ing. Then, the recording signal is recorded by changing the emitted laser light into a signal that changes corresponding to the recording signal that is FM-modulated.

In this way, the principle of an example of the structure for manufacturing the master is
Shown in the figure. In FIG. 1, (1) shows a gas laser device that performs multimode oscillation such as an argon laser,
The laser light la output from the laser light output unit (1a) of the gas laser device (1) is supplied to the laser light input unit (2a) of the acousto-optic modulator (2). The acousto-optic modulator (2) modulates the laser light supplied to the laser light input section (2a) according to a modulation signal obtained by superimposing the ultrasonic carrier signal obtained in the ultrasonic input section (2b). The laser light output section (2c) causes the laser light to be output while being refracted. Then, a slit (3) is arranged in the vicinity of the laser light output part (2c) of the acousto-optic modulator (2), and the slit (3) is provided with a laser beam lb straight through the acousto-optic modulator (2). Sometimes laser light lc is blocked and refracted
In this case, a through hole (3a) for passing the light is provided, and in combination with the acousto-optic modulator (2), it functions as a laser light switching element. Then, a master disk (4) such as a video disk is rotatably arranged in the optical path of the laser light lc that has passed through the through hole (3a) of the slit (3). Actually, from this gas laser device (1) to the master (4)
A plurality of lenses, mirrors, etc. are arranged in the optical path up to and are configured in the master manufacturing apparatus.

With this configuration, the signal supplied to the ultrasonic wave input unit (2b) of the acousto-optic modulator (2) can control the laser light la as well as control the rectilinear movement and refraction of the laser light la. ON / OFF control of laser light irradiation of
The pits are formed on the master (4) in a predetermined state. The use of the acousto-optic modulator (2) in this way has the advantage of simplifying the configuration of the optical path.

[Problems to be solved by the invention]

By the way, when the laser light is switched by using the acousto-optic modulator (2) in this way, there is a disadvantage that an unnecessary spectrum signal is generated in the refracted output laser light lc. For example, if the spectrum signal is generated and recorded within the video signal band when the master disc of the video disc is manufactured, noise is generated on the screen or the like when the video disc manufactured from the master disc is reproduced.

In order to eliminate the generation of such an unnecessary spectrum signal, for example, the laser device (1) may be made to oscillate in a single mode, but in this case, the output of the laser beam drops to about half that of the multimode laser. Therefore, there is an inconvenience that it cannot be used for manufacturing a master that requires a high output laser beam such as a video disk.

The present invention has been made in view of the above problems, and an object thereof is to provide an optical recording method in which an unnecessary spectrum signal does not occur in recorded data even when a high-power multimode laser is used.

[Means for solving problems]

The optical recording method of the present invention is, for example, as shown in FIG.
In an optical recording method in which a gas laser device (1) that oscillates a multi-mode laser is used as a laser source, and an acousto-optic modulator (2) is used to modulate the laser to record data on a recording medium (4), The beat frequency between the longitudinal modes of _{L is} [Hz], the carrier frequency of the acousto-optic modulator (2) is c [Hz], and the recording frequency band is 0 to
When [Hz] is set, the beat frequency _L between longitudinal modes and the carrier frequency c are selected so as to satisfy the expression of | m · _L− n · c | ≧ (where m and n are integers). .

[Action]

The optical recording method of the present invention uses the above-mentioned | m · _L −n · c |
By satisfying the expression ≧, unnecessary spectrum signals are generated only outside the recording frequency band, unnecessary spectrum signals are not generated within the recording frequency band, and good recording can be easily performed.

〔Example〕

An embodiment of the optical recording method of the present invention will be described below with reference to the accompanying drawings. In this example, as the recording device, the device whose principle is shown in FIG. 1 is used.

In this example, a gas laser device (1) is used to manufacture a master disk (4) of a video disk using an acousto-optic modulator (2) as shown in FIG. here,
When the master plate (4) is irradiated with laser light in this way, the length of the resonator of the gas laser device (1) (mirror (1
b), the length between (1c)) is L, and the accompanying beat frequency between longitudinal modes of the laser light is _L , (However, C is the speed of light in the medium). The intensity distribution of this longitudinal mode becomes strong around a specific frequency band as shown in FIG. 2, for example. Then, assuming that the frequency of the carrier signal supplied to the acousto-optic modulator (2) is c [Hz], the spectrum signal s unnecessary for the laser light passing through the acousto-optic modulator (2) is expressed by the following formula (2). It is understood that the problem occurs under the conditions shown in.

s = | m · _L −n · c | (2) (where m and n are integers) In this case, particularly when m = 3 or 4, and n = 2, a signal with strong spectrum intensity may be generated. I passed on experimentally.
Therefore, if the recording band of the video signal recorded on the video disk is 0 to 15 [MHz], for example, 15 [MHz]
If the condition of the equation (2) is set so that the spectrum signal s is not generated in the band up to, no unnecessary spectrum signal is generated in the recording signal. That is, if the condition of | m · _L −n · c | ≧ 15 [MHz] is satisfied, an unnecessary spectrum signal s is not generated between 0 and 15 [MHz]. In this case, the resonator length _L
Is determined by the gas laser device (1), the carrier signal frequency c of the ultrasonic wave supplied to the acousto-optic modulator (2) is selected. For example, if the beat frequency interval _L between longitudinal modes is 135 [MHz], the carrier signal frequency c is 127.5 to 142.5 [MHz], 195 to 210 [MH].
z] and 0 when set in the range of 277.5 to 292.5 [MHz]
An unnecessary spectrum signal with high intensity is generated in the range of ~ 15 [MHz]. Therefore, if you avoid each of the above frequency bands,
For example, as shown in FIG. 3, a strong unnecessary spectrum signal s is generated only in the range of 0 to 15 [MHz], and 0 to 15 [MH] is generated.
Unnecessary strong spectral signals are not generated in the range [z].

For production of a master disk of a video disk, the beat frequency _L between longitudinal modes corresponding to the length of the resonator is preferably in the range of 80 to 150 [MHz] in consideration of the output of the laser device. The carrier signal frequency of the acousto-optic modulator is preferably about 200 [MHz]. Therefore, considering the above conditions within this range, for example, _{L 2} = 135 [M
If Hz] and c = 224 [MHz], unnecessary spectrum signals can be suppressed between 0 and 20 [MHz], and good video signals can be recorded without noise during reproduction.

As described above, according to the recording method of this example, although the acousto-optic modulator (2) is used to perform switching and modulation of laser light, an unnecessary spectrum signal is generated in the recording video band. do not do. Therefore, as the gas laser device (1), a device that performs multimode oscillation with a large output can be used, and a video signal can be recorded well. Since the carrier signal c is set on the electric circuit side, complicated adjustment is not required on the laser optical path side. Further, since the acousto-optic modulator (2) has a small characteristic change due to temperature, the laser light can be stably modulated, and a signal can be satisfactorily recorded. Further, since a gas laser device (1) having a large output can be used, good recording can be performed even in so-called double beam writing in which one laser beam is divided into two or more and recording is performed by the plurality of laser beams. it can.

Although the present invention has been described as an apparatus for manufacturing a master disk of a video disk in the above-mentioned embodiments, it can be applied to various recording media for recording using laser light, such as an optical disk recording apparatus for recording digital data. Of course, it can be applied to a recording device. Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the optical recording method of the present invention, there is an advantage that an excellent spectrum signal is not generated in the recording frequency band and good signal recording can be easily performed on the recording medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a recording apparatus used in an embodiment of the optical recording method of the present invention, and FIGS. 2 and 3 are diagrams for explaining an embodiment of the present invention. (1) is a gas laser device, (2) is an acousto-optic modulator,
(4) is a master.

Claims (1)

[Claims] 1. An optical recording method in which a gas laser device for oscillating a multi-mode laser is used as a laser source, and data is recorded on a recording medium by using an acousto-optic modulator for modulating the laser. The beat frequency is _L [Hz], and the carrier frequency of the acousto-optic modulator is c [H]
z] and the recording frequency band is 0 to [Hz], the beat frequency _L between the longitudinal modes and the carrier frequency are satisfied so that the expression | _mL- n-c | ≧ (where m and n are integers) is satisfied. An optical recording method characterized in that c is selected.