JPH027248A - Method for recording signal on optical master disk - Google Patents

Abstract

PURPOSE:To always record a signal with desired width and length in spite of the length of a pit by controlling light strength corresponding to the pulse width i.e. the length of the pit of a signal waveform to be recorded. CONSTITUTION:Address information consisting of pit signals of a sector mark part 1, a vfo part 2, and an ID part 3, etc., is recorded on an optical master disk as a pre-pit part by a laser beam. Here, the strength of the laser beam is controlled corresponding to the pulse width of the signal waveform to be recorded. In other words, the strength of the laser beam is decreased when recording the signal of a long pit like the one of the sector mark part 1, and the strength of the laser beam is increased when recording the pit signal like the one of the vfo part 2. In such a way, it is possible to always obtain the pit of desired shape in spite of the size of the pit.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to the recording of signals on a master optical disc using a laser beam, so-called laser cutting.

<Prior Art> In recent years, optical discs that record, reproduce, or erase information using light have been actively developed.

In these optical discs, tracks are provided concentrically in a spiral disc, and a light spot is scanned along the tracks to record, reproduce, or erase information. In this track, address information such as the track number is formed in advance in the form of minute pits as a pre-pit section, and information can be recorded or played back at any location based on this address information. can.

An optical disk master provided with such a prepit portion is manufactured by boat as follows. First, a photoresist is applied onto a glass master disk, and while the resist master disk is rotated, a laser beam from a light source such as an Ar laser is narrowed down into a spot by an optical system and irradiated onto the photoresist, thereby creating a spiral track. exposed to light.

At this time, a pre-pit portion having a desired pit shape is formed by modulating the laser beam from the light source with a signal corresponding to the address information.

This glass master disk is developed to obtain the desired uneven pattern,
By electroforming a metal such as Ni thereon and then peeling it off, a so-called stamper having unevenness opposite to the desired unevenness can be obtained. Using this stamper as a mold, the unevenness is transferred onto a plastic disc by pressing or injection molding to obtain an optical disc.

In the optical disc obtained in this way, address information is recorded as a pre-pit part as described above.
According to the optical disc format by L5O (International Organization for Standardization), as shown in Figure 4, this address information includes sector mark 1, which indicates the beginning of a unit of information (sector), and clock synchronization. vro to take
It is composed of bit signals such as a part 2 and an ID part 3 corresponding to a track number and the like. The sector mark part l is
It is a long pit signal, and the vfo section 2 is a continuation of the shortest bit signal.

When recording these address information as a pre-pit section on the master optical disc as described above, for example,
If we use a laser beam with the light intensity pattern shown in Figure 6,
Since the VFO section 4 is the shortest pit signal with a short pulse width, it is difficult to record sufficiently due to a decrease in the transfer function (0TF) of the optical system, whereas the sector mark section 5 is a shortest pit signal with a short pulse width. Since the target is long, there is little deterioration in recording characteristics and there is no possibility of insufficient recording. That is, in recording address information, long pits such as the sector mark portion 5 are recorded in desired shapes in both width and length;
Short bits, such as , tend to be narrow in width and short in length.

In order to compensate for the lack of recording in the VFO section 4, if the light intensity shown in FIG. 6 is uniformly increased as a whole for recording, the bit width of the sector mark section 5 will become unnecessarily wide. FIG. 7(A) is a plan view showing the shape of the recording pit at this time, and FIG. 7(B) is a waveform diagram of the reproduced signal. In FIG. 7(A), reference numeral 6 denotes a group for tracking, and the bits of the address information are formed between the groups 6. The bit width Wt of the sector mark section 7 is equal to
The bit width W2 is unnecessarily wide. When the address information of bits with this shape is reproduced, the seventh
As shown in Figure (B), an unnecessary spike signal IO is generated in the sector mark section 9, making it difficult to detect the sector mark section 9 properly and causing malfunction.

The reason why this spike signal IO occurs can be considered as follows. That is, as shown in FIG. 7(A), the width of the center 11a of the pit 11 of the sector mark portion 7 is relatively large compared to the diameter of the light spot, so that the rate of light diffraction is small. Therefore, the reflectance becomes high, whereas at the tips 11b of the pits 11, the rate of light diffraction becomes larger than at the center due to the influence of the edges.

Therefore, the reflectance of light is lower at the tip 11b than at the center 11a, and a spike signal IO is generated.

<Objective of the Invention> The present invention has been made in view of the above points, and an object of the present invention is to enable recording with a desired width and length at all times, regardless of the length of the bit.

<Structure of the Invention> In order to achieve the above-mentioned object, the present invention provides a method for recording a signal on an optical disc master using a laser beam, in which the intensity of the recording laser beam is controlled according to the pulse width of the signal waveform to be recorded. That's what I do.

According to the above configuration, the light intensity is controlled according to the pulse width of the signal waveform to be recorded, that is, the length of the bit.
This prevents insufficient recording when short bits are used, and conversely, when long pits are used, the width of the pits becomes wide and unnecessary spike signals are not generated in the reproduced signal.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a recording apparatus for implementing the method of the present invention, and in the same figure,! Reference numeral 2 denotes a signal generator for generating a signal S1 corresponding to address information to be recorded on a master optical disc, and also outputs an intensity designation signal S2, which will be described later. Reference numeral 13 denotes a signal generator 12 for generating a signal S1 corresponding to address information to be recorded on a master optical disc. This laser cutting device 13 is a laser cutting device that performs exposure according to a signal Sl from the argon laser. The optical disc is equipped with an optical system that guides the laser beam from the disc to the optical disc master coated with resist.

The present invention is directed to the sector mark section 1 in FIG. vf.

This is a method for recording address information constituted by pit signals such as part 2 and ID part 3 as a pre-pit part on an optical disc master using a laser beam, and the intensity of the laser beam is adjusted according to the pulse width of the signal waveform to be recorded. I try to control it.

In this example, the sector mark part! The intensity of the laser beam is lowered when recording long pit signals such as in the sector mark area, and the intensity of the laser beam is increased when recording short pit signals such as the VFO area 2 other than the sector mark area.

In other words, when recording address information by irradiating a laser beam onto an optical disc master coated with photoresist,
I'm doing it like this:

A signal Sl corresponding to address information from the signal generator 12
is output to the laser cutting device 13, and
An intensity designation signal S2 that designates the intensity of the laser beam according to the pulse width of the signal to be recorded is output to the laser cutting device 13. This intensity designation signal S2 is a high-level signal for reducing the intensity of the laser beam when recording a sector mark portion l with a long pulse width, and is a high-level signal for reducing the intensity of the laser beam when recording a sector mark portion l with a long pulse width. During recording, this is a low level signal to increase the intensity of the laser beam.

In the laser cutting device 13, based on the intensity designation signal S2, the laser beam is modulated by an optical modulator according to the signal S1 to obtain modulated light with an intensity corresponding to the intensity designation signal S2. This modulated light is narrowed down into a spot by an optical system and is irradiated onto an optical disc master coated with photoresist, as in the past, to expose a spiral track and form a pit-shaped pre-pit section corresponding to the address information. be done.

FIG. 2 is a signal waveform diagram of the above embodiment, and FIG.
is the light intensity pattern of the signal to be recorded, and (B) in the figure is the intensity designation signal S2. When the pulse width W is long as in the sector mark part 14, the intensity designation signal S2 becomes high level and the light intensity is lowered, and as in the VFO part I5 other than the sector mark part 14, the pulse width W is short. Sometimes, the intensity designation signal S2 becomes low level and the light intensity is increased.

FIG. 3(A) is a plan view showing the shape of the pit recorded in this manner, and FIG. 3(B) is a waveform diagram of the reproduced signal. When recording long pits such as the sector mark part 16, the intensity of the laser beam is lowered, and conversely, when recording short pits such as v r o 1417 other than the sector mark part 16, the intensity of the laser beam is increased. This makes it possible to make the pit width of the VRO portion 17 wide and to have a desired length while keeping the pit width of the sector mark portion 16 relatively narrow. Therefore, unnecessary spike signals do not occur in the reproduced signal as in the conventional example shown in FIG. 6(B).

Incidentally, the relationship between recording power and line width is shown in FIG. In FIG. 5, the horizontal axis represents recording power, and the vertical axis represents line width. Line A corresponds to a group, that is, a sector mark portion with a long pit, and line B corresponds to a vfo portion. As shown in FIG. 5, for example, in order to make the widths of the sector mark part and the vfo part the same W, the recording power is set to Pg for the sector mark part and Pvf for the vfo part.
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<Effects of the Invention> As described above, according to the present invention, since the intensity of the laser beam is controlled according to the pulse width of the signal waveform to be recorded, the desired shape can always be achieved regardless of the length of the pit. It is now possible to obtain pits, and it is no longer possible to record insufficiently when the pits are short or to cause spike signals in the reproduced signal due to the width becoming unnecessarily wide when the pits are long.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a recording apparatus for carrying out the method of the present invention, Fig. 2 (A) is a waveform diagram showing the light intensity pattern of the recording signal, and Fig. 2 (B) is a waveform diagram of the intensity designation signal. , FIG. 3(A) is a plan view of a bit recorded by the method of the present invention,
Figure 3 (B) is a waveform diagram of the reproduced signal, Figure 4 is a signal waveform diagram showing the structure of address information, Figure 5 is a diagram showing the relationship between recording power and line width, and Figure 6 is a diagram of the conventional example. FIG. 7(A) is a waveform diagram showing a light intensity pattern of a recording signal, FIG. 7(A) is a plan view of a pit in a conventional example, and FIG. 7(B) is a waveform diagram of a reproduction signal in a conventional example. 12... Signal generator, 13... Laser cutting device.

Claims (1)

[Claims] (1) A method for recording signals on a master optical disc using a laser beam, the method comprising: controlling the intensity of the laser beam according to the pulse width of a signal waveform to be recorded.