JPS6342035A - Recording method for information to optical information recording medium - Google Patents

Abstract

PURPOSE:To easily form accurate information pits even on an optical information recording medium of low scanning speed by interruptedly projecting a laser light as a pulse light. CONSTITUTION:In case of formation of one information pit, the laser light is projected interruptedly, namely, as the pulse light when a spot S scans an extent (x). Consequently, the outline of the formed information pit is waved and is not linear, but trouble of reading is not especially caused. Thus, information pits are formed without reducing the laser light power even in case of a low scanning speed, and the flat area of a graph can be used as the control area similarly to write on a recording medium of high scanning speed, and the pit width is accurately controlled.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is a method for recording information on an optical information recording medium, particularly suitable for recording on an optical t1 information recording card using a laser beam. related to information recording methods.

(Prior Art) Currently, devices that optically record and reproduce information, including optical disk devices, are in widespread use. In these devices, information is recorded by forming minute information pits on an information recording medium. This information pit is generally formed by scanning with laser light.

(16 Problems to be Solved by the Invention) In recent years, optical information recording cards have been attracting attention as a new optical information recording medium. However, when forming information pits on such an optical information recording card, a problem arises in that it is difficult to form accurate information pits using the method used for conventional optical discs.

This problem is due to differences in scanning speed. For example, in the case of an optical disc, an optical disc with a diameter of 2001 is 50 Orl)
If the laser beam is scanned by rotating at the rotation speed of III, the scanning speed of the outermost track is approximately 520 cm/sec.
c. On the other hand, in the case of an optical information recording card, the scanning speed is at most about 8 to 101/sec, which is about two orders of magnitude smaller.

It has been experimentally confirmed that when the scanning speed decreases in this way, it becomes extremely difficult to control the information pit width. The results of this experiment are shown in FIGS. 3 and 4. Third
The figure is a graph showing the relationship between laser light power and pit width when forming information pits on an optical disk with a fast scanning speed, and Figure 4 shows the relationship between forming information pits on an optical information recording card with a slow scanning speed. These are the same graphs of
It is a characteristic graph when 0-830M laser is irradiated. Depending on the material of the medium [although there are some differences,
Almost the same characteristics can be obtained with optical recording media commonly used today. As shown in the graph, pits are formed when the laser beam power exceeds a predetermined threshold value WT□, and as the power increases, the width of the formed pits also increases. However, since the scanning speed in Figure 4 is similar to that in Figure 3 (as mentioned above, the difference is only about two orders of magnitude), the pit width will be larger in the latter when the same laser light power is applied. .

Now, the information pits actually formed are tllJQ pits in the scanning direction X, as shown in FIG. Here, the pit ix can be controlled by the scanning period of the laser beam, but the pit width y must be controlled by the laser beam power. Usually, this pit width y is controlled to about 1 to 1.5 μm. Referring to the graph in Figure 3, in order to make the pit width 1 to 1.5 μm, the laser light power should be adjusted to a-
It is sufficient if the control is performed during the period b. However, in the graph of FIG. 4, in order to similarly set the pit width to 1 to 1.5 μm, the laser light power must be controlled between c and d. That is, in the case of an optical information recording card, the adjustment range of the laser light power becomes narrow, making it difficult to accurately control the pit width. To put it bluntly, in FIG. 3, the flat region of the graph can be used as the it, +1111 range, whereas in FIG. 4, the rising region of the graph must be used as the control range. Therefore, when forming pits with accurate widths on optical information recording cards, more stringent conditions are required for the stability of the laser beam and the uniformity of the sensitivity of the recording medium.

Therefore, an object of the present invention is to provide an information recording method that can easily form accurate information pits even on an optical information recording medium with a slow scanning speed tη.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a method for recording information on an optical information recording medium in which a laser beam is scanned in a predetermined direction to form elongated information pits on the optical information recording medium. By irradiating light intermittently, it is possible to easily form accurate information pits even on optical information recording media with slow scanning speeds.

(Function) Conventionally, writing information pits on optical discs, etc.
Scanning was performed while continuously irradiating laser light. However, if the same method is applied to a recording medium with a slow scanning speed, such as an optical information recording card, the laser light power must be reduced.

ml, when writing is performed using a laser beam of a predetermined wavelength and a predetermined spot diameter, if the laser beam power is P, the laser spot diameter is ω, and the laser irradiation time is t, then the recording medium receives Energy per unit area ff1E can be approximately expressed by equation (1).

E first P-t/ω ・・・・・・・・・・・・・・・
・・・・・・・・・・・・(1) Here, if the scanning speed of the recording medium is ■ and J, then t-ω/V ・・・・・・・・・・・・
It is known that it can be expressed as (2), so by substituting this relationship into equation (1), we get E絢P/Vω・・・・・・・・・・・・・・・・・・
......(3) is obtained. In other words, if the scanning speed () becomes slower, even if the same laser light power P is used for recording, the energy per unit area received by the recording medium will be
E becomes larger. Therefore, in order to keep the energy BE at an appropriate value, P must be lowered.

When the laser light power P is reduced in this way, the f! As mentioned above, the i area must be the control 21I area.

In the method according to the present invention, since scanning is performed while continuously irradiating laser light as pulsed light, information pits can be formed without reducing the laser light power even if the scanning speed becomes slow. As in the case of writing on a recording medium with a high scanning speed, the flat area of the graph can be used as a control area, making it possible to accurately control the pitch width.

(Example) Examples illustrating the present invention will be described below. It will then be deprinted.

When forming one information pit using the conventional method, the second
As shown in the figure, when scanning the spot S by a distance of X,
Laser light is continuously irradiated. On the other hand, in the method according to the present invention, the spot S is
When scanning a distance of , the laser beam is irradiated intermittently, that is, as pulsed light. Therefore, in the method according to the present invention, although the contour line of the formed information pit is wavy and not a straight line, no particular problem arises in reading it.

FIG. 5 is a graph showing the relationship between the laser light power and the width of the pits formed when information pits are formed by irradiating the optical information recording card with laser light as pulsed light according to the present invention. This graph is an actual value obtained as a result of writing using a writing system similar to that used in FIGS. 3 and 4 and irradiating a laser beam with a duty ratio of 70%.

It can be seen that in order to set the pit width to 1 to 1.5 μm, the laser light power may be controlled between e and f. control area i
ii! Since it is possible to use a flat region of the graph as (e-f), the control region becomes considerably wider than the conventional method (control@regions C to d) shown in FIG. Therefore, it is possible to form information pits with accurate pit widths even in a writing system where instability of the laser beam and non-uniformity of the sensitivity of the recording medium occur.

The duty ratio of the pulsed light (the ratio of 111 periods of light irradiation to one cycle of pulsed light that is intermittently supplied) must be selected to such an extent that the information pits form one continuous closed region. Must be. That is, as shown in FIG. 1, when the duty ratio is decreased, one spot S
1 and the adjacent spot S2 become farther apart, so that the distance between the spots S2 and S2 increases to the point where the two spots are completely separated.
- If the tee ratio is lowered, it will no longer be possible to form one information pit. Therefore, the duty ratio cannot be lowered beyond a certain level. In order to smooth the outline of the information pit that is formed,
It is desirable that the duty ratio be as large as possible. However, if the duty ratio is made too high, the effect of the present invention will be reduced (in an extreme case, if the duty ratio is set to 100%, continuous light will be produced, no different from the conventional method). Generally, it is most preferable to set the duty ratio to 50 to 80%.

In carrying out the method according to the present invention, it is preferable to use a semiconductor laser as a writing light source.

In the case of a semiconductor laser, pulse driving can be easily performed, and it also has the advantage of having a longer life than continuous driving.

(Effects of the Invention) As described above, according to the present invention, since information pits are formed using pulsed light, a wide pitch width control area can be secured even for a recording medium with a slow scanning speed. Positive 1AI pit width control can be performed.

[Brief explanation of drawings]

FIG. 1 is a diagram of the principle of the recording method according to the present invention, FIG. 2 is a diagram of the principle of the conventional recording method, FIG. 3 is a graph showing the restricted area when writing to an optical disc by the conventional method, The figure is a graph showing the control area when writing is performed on an optical information recording card using the conventional method, and FIG. 5 is a graph showing the ai control area when writing is performed on the optical information recording card using the recording method according to the present invention. It is. S, Sl, S2... Laser light spot, X... Information pit length, y... Information pit width, WTll... Threshold. Applicant's agent Mr. Sato Figure 1 Figure 2

Claims (1)

[Claims] 1. An information recording method in which laser light is scanned in a predetermined direction to form elongated information pits in the predetermined direction on an optical information recording medium, in which the laser light is intermittently irradiated as pulsed light. A method for recording information on an optical information recording medium, characterized in that: 2. A method for recording information on an optical information recording medium according to claim 1, characterized in that the duty ratio of the pulsed light is selected so that the information pits form one continuous closed area. . 3. The method for recording information on an optical information recording medium according to claim 2, wherein the duty ratio of the pulsed light is 50 to 80%. 4. The method for recording information on an optical information recording medium according to any one of claims 1 to 3, wherein the optical information recording medium is an optical information recording card. 5. A method for recording information on an optical information recording medium according to any one of claims 1 to 4, characterized in that a semiconductor laser is used as a light source of the laser beam.