JPH01154328A - Optical information recording and reproducing device capable of multivalued recording - Google Patents

Abstract

PURPOSE:To form marks of different recording states in corresponding to the irradiating quantity of a laser light so as to make multivalued recording possible by controlling the projecting quantity of the laser light within a prescribed range when recording is made on a recording medium which is composed of a single layer and has a smooth recording characteristic. CONSTITUTION:When the reproduced reflecting light quantity of a no-recording section and the reflecting light quantity of a recording section are respectively represented by R0 and R1, the percentage modulation C can be defined as C=(R0-R1)/(R0+R1). A recording film of an ICO-N film is deposited on a base plate by an RF magnetron sputtering using an In target and setting the mixing ratio of CH4, O2, and N2 of the mixed gas at 54:23:23. This recording medium has the saturation point of percentage modulation at 20mW. The 90% and 10% projecting power against the saturation are respectively set to a2 and a1 and the projecting light quantity is controlled so that A=(a2-a1) can become >=3. When a mark recorded under such condition is reproduced, three clearly distinctive values of percentage modulation which are 0(zero) at '0' value, 0.3 at '1' value, and 0.5 at '2' value are obtained.

Description

[Detailed description of the invention] [Purpose of the invention] (Field of use in IM business) The present invention relates to an optical information recording device capable of multilevel recording.

(Conventional technology) In recent years, it has been used as a high-density, large-capacity information storage device.

Optical disk memory devices using lasers are emerging.

Hard disks can be roughly divided into three types: read-only types, write-once types, and rewritable types. In the write-once type, recording is performed by forming marks with a length of about p on tracks separated by a pitch of, for example, about 1.6ρ, and during playback, a weaker laser beam than during recording is applied.
The presence or absence of a mark is read based on the difference in the amount of reflected light.

The method for recording information on this optical disk is to irradiate the recording area with strong laser light and deform the recording film (forming pits, bubbles, etc.) by increasing the temperature of the irradiated area. Also, this information.

Two states are recorded, with or without marks ("0" or "1"), and during playback, these marks are irradiated with laser light and the above two states ( "
0" or "1") and read the binary information.

Currently, this optical recording is desired to have even higher density.
Methods such as multi-layer recording and multi-level recording, in which multiple recording layers are used, are being considered.

This multilayer recording is one in which several recording films are laminated. For example, a method has been considered in which an intermediate layer is provided between each recording layer to avoid interference between the layers and to focus on each layer to perform independent recording on each recording layer. However, this method is still difficult to put into practical use due to difficulties in laminating multilayer recording films during manufacturing and focusing the laser beam on each layer during recording and reproduction.

In addition, multi-value recording means the above-mentioned ro" for one mark,
rOJ, rlJ for binary records such as “IN”
.

This method attempts to store three or more values such as "2", etc. As a method for this multi-value recording, a method has been considered in which a multi-value recording film is formed using a stack of recording media (a stack of the same medium or a stack of different types of media).

A first example will be shown below using FIG.

FIG. 5 is a diagram showing the principle of ternary recording using a two-layer structure. The recording film used a two-layer structure in which a low melting point recording material No. 54 was used as the first layer and a high melting point recording material No. 55 was used as the second layer. During recording, 51 is in a non-recording state rQJ, and 52 is irradiated with a weak power such that only the first layer [1] film changes and the second layer film does not change.
Three-level recording is performed with recording of 1 and recording of ``2'', which irradiates the second layer of 53 with a power strong enough to cause a change. During reproduction, a ternary signal is read by detecting changes in the amount of reflected light for each depth.

Another example will be shown below using FIG.

This is an example in which three-value recording is possible using bubble mode recording using a two-layer structure.

FIG. 6(a) shows the first layer formed of 61 metal films on the substrate.
(b) shows how the laser irradiated area changes due to bubble formation, and (C) shows how the laser irradiated area disappears. It is a figure showing each. This film can be used with weak recording power (b
), and the re-main reflected light amount is 0 in the non-recorded area.
”, the film is made to disappear as shown in (c) with strong recording power, and the amount of playback reflected light is not so high that it becomes a state of “2”. Three-level recording is performed. This is an example where this is possible. In this example, when detecting only the amount of reflected light,
Since it is difficult to clearly distinguish between 0''rlJ and r2J,
The recording state is distinguished by simultaneously detecting the amount of transmitted reproduction light.

That is, the transmitted light is weak in the unrecorded area in (a) and the bubble formation area in (b), and the transmitted light is strong in the area where the recording film disappears in (C). By combining this with each value of the amount of reflected light, the reliability of signal discrimination is increased.

Still another example will be shown below using FIG.

This is an example in which three-value recording is possible using a single layer.

FIG. 7 shows 71 recording immature areas (preholes) and 72 normal recording areas (holes) using a film that records by the disappearance of the recording film (generally called pits, holes, etc.). FIG. 3 is a diagram showing the amount of reflected light for reproduction versus recording power. This takes advantage of the fact that the recording film forms a small swell in the immature recording area of 71 with respect to the lost record (hole) which is the normal recording area of 72. Since this record immature area corresponds to the bubble in Figure 6(b),
Three-value recording is performed using bubbles (preholes) and vanishing areas (holes), and this single-layer medium can also be used to record three-value data using the same method used to distinguish between bubbles and vanishing in a two-layer film explained in Figure 6. This is an example where value recording is possible. However, in this method, the 71 area is very narrow and it is difficult to control during recording, and the bubbles in the unrecorded area are small, so when playing back, the unrecorded area is The recording layer had a laminated structure of several recording materials as mentioned in the example above. Manufacturing these recording films requires controlling the film thickness for each layer, which increases the number of steps and increases costs.Furthermore, film thickness control and film composition accuracy are more difficult than when manufacturing a single recording film. There were other difficult problems.

In the type that performs multi-level recording using a single recording film, it is difficult to control the amount of irradiation light during recording as mentioned above, and furthermore, there are problems such as difficulty in distinguishing signals during reproduction.

In addition, in conventional multilevel recording, the recording sensitivity changes greatly depending on changes in the amount of recording irradiation light, so fluctuations in the amount of recording irradiation light, non-uniformity of the medium, and jitter in the rotation system occur.

Due to fluctuations in amplitude or offset due to variations in the composition of each disc, the reproduced signal level may fall within the predetermined standard range of each multilevel signal, or may fall within the standard range. The problem was that false detections could occur due to deviations from the target.

Therefore, the present invention has been made in view of the above problems, and its purpose is to perform multi-level recording using a recording film with a gentle recording characteristic formed on a single recording medium, and which requires only the amount of laser irradiation during recording to produce 8 rays. An object of the present invention is to provide an optical information recording/reproducing device that can perform multi-level recording.

[Structure of the invention]

(Means for Solving the Problems) In the optical information recording and reproducing apparatus of the present invention, firstly, an optical information recording and reproducing apparatus records and reproduces information by forming marks on a recording film by irradiating a laser beam. In the recording medium, the recording sensitivity of the recording film to the amount of light irradiated during recording is expressed as a characteristic (generally referred to as "characteristic") that is very smooth, that is, the reproduction reflection of the non-recorded area. The amount of light is R0, the amount of reflected light from the recording section is R1, and C=
When defined as (Ro-R1)/(Re + R1) (hereinafter C is referred to as modulation rate), the modulation rate is 90 The recording power that gives a modulation rate of % is 82,
Also.

Let a be the recording power at which the modulation rate is 10% with respect to the saturated modulation rate, and furthermore, when A = (a2at) is defined, it is assumed that in the recording medium, A is 3 or more. Second, with respect to the saturated modulation rate where the modulation rate of the reproduction reflected light amount does not change as the recording irradiation amount increases, b2 is the irradiation light amount at which the modulation rate becomes 90%, and the saturated modulation rate W
Let b□ be the amount of irradiated light that gives a modulation rate of 10% with respect to the do.

(Function) In a recording medium with a single layer and smooth recording characteristics,
By controlling the amount of laser irradiation during recording, marks with different recording states corresponding to the amount of irradiation are formed, allowing multi-level recording.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.6 Figure 1 is a diagram showing the modulation rate with respect to the irradiation power of the recording film, and Figure 2 is a diagram showing the reproduction of each multilevel signal. A diagram showing the modulation rate of time,
FIG. 3 is a diagram showing the recording irradiation power of each multilevel signal.

As shown in FIG. 1, the present invention exhibits a constant value within the range of fluctuations caused by non-uniformity of the medium when the modulation factor is 20+nw or more. In other words, with a recording medium that has a saturation point at 20 mW,
The irradiation power at the 90% point with respect to this saturation point is 15d, 1
The experiment was carried out using a recording medium having a characteristic that the irradiation power at the 0% point was 8 mυ. This recording medium has a diameter of 130 m and a thickness of 1.
A 2I PC (polycarbonate) substrate was used, and an ICO-N film was used as the recording film.

To manufacture this ICO-N film, an RF magnetron sputtering device equipped with an indium target having a diameter of 127 ohm was used. C114, O2 and N for sputtering
A mixed gas of 2 was used. The mixing ratio (volume ratio) is 5
It was set as 4.23.23%. The pressure during discharge is 1.3×1
The applied power was O-2 Torr and 5001i1. By performing discharge for 2 minutes under these conditions, a recording film with a thickness of 1100 nm was deposited on the substrate.

Each recording power was controlled as shown in FIG. 3, with the "0" value mark turned on, the "1" value mark turning on 10 mW, and the "2" value mark turning on 15+nW. Here, the recording pulse width was set to 150 nm at a rotation speed of 900 rpm and a radius of 55 mm.

When the marks recorded under these conditions are reproduced, the modulation rate is as shown in Fig. 2: rQJ value is 0, "1" value is 0.3,
” value was clearly determined to be 0.5.

By using a recording film with such smooth recording characteristics, it is possible to perform multi-value recording with a single recording film, compared to the conventional multi-value recording method. This can also be realized by easy means that can be controlled only by the amount of irradiation light during recording. In addition, since the recording characteristics of the medium are smooth, even if the irradiation conditions during recording change slightly, such as uneven composition of the medium, jitter in the rotation system of the recording device, fluctuations in recording power, etc.

Since almost the same amount of reproduction reflected light can be obtained during reproduction, a highly reliable multi-level recording/reproduction device can be realized.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

For example, in this example, the recording irradiation light amount (total energy amount of light irradiated onto the medium by a single recording pulse) was controlled by the power level with a constant pulse width. FIG. 4 is a diagram showing methods other than the irradiation side shown in this example, in which (a) is an example of controlling by pulse width, (b) is an example of combining pulses, (
c) is an example of controlling by the combination and magnitude of pulses. As shown in Figure 4 (a), this can be controlled by pulse width, or both pulse width and magnitude, or (b)
) There is no limitation in shape, size, combination, etc., such as control by combining several pulses to form one mark as in (c). Furthermore, in this example,
Although the control is performed using a rectangular pulse, it may be of other shapes than the rectangular pulse.

Further, the recording medium is not limited to those used in this example, such as a recording film and a substrate, and any medium that satisfies the scope of the claims is included in the present invention.

As described above, any form is possible as long as it does not depart from the spirit of the present invention, and such form is included in the present invention.

〔Effect of the invention〕

According to the present invention, multilevel recording can be easily achieved using a recording film having smooth recording characteristics formed on a single recording medium using only the amount of laser irradiation during recording.

Therefore, in the recording system, it is an effective means of increasing the density using multilevel recording, and since it is possible to perform multiplex recording with only a single recording layer, which is the same as before, it is possible to use multilevel recording media. During manufacturing, variations in film thickness accuracy and composition from disc to disc in recording film formation.

Further, difficult problems such as an increase in the number of steps do not occur.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the modulation rate with respect to the amount of light irradiated on the recording film.
Figure 2 is a diagram showing the modulation rate when reproducing each multi-level signal, Figure 3 is a diagram showing the recording irradiation light amount of each multi-level signal, and Figure 4 is a diagram showing the control method when recording each other multi-level signal. Diagram showing! Figure 5 is a diagram showing the principle of three-value recording using the conventional method, Figure 6 is a diagram representing the principle of three-value recording using another conventional method, and Figure 7 is a diagram showing the principle of three-value recording using another conventional method. FIG. 2 is a diagram illustrating the principle of ternary recording. Agent Patent Attorney Rules Mitsuyuki Matsuyama Figure 1 15 7chi 12゜ Figure 2 5・'f, '2J Figure 3 θ 1. '2'. (a) (b) (C) Figure 4 Figure 5 (α) (shi) (
)Figure 6Figure 7

Claims (9)

[Claims] (1) In an optical information recording and reproducing device that records and reproduces information by forming marks on a recording film by laser beam irradiation, the amount of reproduction reflected light in the non-recorded area is R_0, the amount of reflected light in the recorded area is R_1, Modulation rate C={R_0-R_1}
A_2
Also, let the recording power at which the modulation rate is 10% of the saturated modulation rate be a_1, and furthermore, A=(a_2-a_
1) An optical information recording/reproducing apparatus capable of multi-level recording, wherein A of the recording medium is 3 or more. (2) A patent claim characterized in that the recording irradiation conditions are such that each multi-value recording is performed by a difference in the amount of light irradiated during recording or the laser power, and that multi-value recording is performed by further controlling the amount of irradiated light. An optical information recording/reproducing device capable of multi-level recording according to item 1. (3) The level setting for each multi-value is to set one value for an irradiation light amount of a_1 or less, another value for an irradiation light amount of a_2 or more, and one or more values between a_1 and a_2. An optical information recording/reproducing apparatus capable of multi-level recording according to claim 1. (4) When setting the level of each multi-value, set one value for the irradiation light amount below b_1, another value for the irradiation light amount above b_2, and set one or more values between b_1 and b_2. An optical information recording and reproducing apparatus capable of multi-level recording as set forth in claim 2 or 3. (5) As a recording medium, indium is used as CH_4 and O_2
Optical information capable of multilevel recording according to claim 1, 2, 3, or 4, characterized in that a recording film sputtered in a mixed gas of and N_2 is used as the recording film. Recording and playback device. (6) For a saturated modulation rate where there is no change in the modulation rate of the reproduction reflected light amount with an increase in recording irradiation light amount, the irradiation light amount at which the modulation rate becomes 90% is b_2, and for the saturated modulation rate, 10 The amount of irradiated light that gives a modulation rate of % is b_1,
Furthermore, when we define B=(b_2-b_1)/b_2,
An optical information recording/reproducing apparatus capable of multi-level recording, wherein the recording medium has B of 0.3 or more. (7) A patent claim characterized in that the recording irradiation conditions are such that each multi-value recording is performed by a difference in the amount of light irradiated during recording or the laser power, and that multi-value recording is performed by further controlling the amount of irradiated light. An optical information recording/reproducing device capable of multi-level recording according to item 6. (8) When setting the level of each multi-value, set one value for the irradiation light amount below b_1, another value for the irradiation light amount above b_2, and set one or more values between b_1 and b_2. An optical information recording/reproducing apparatus capable of multi-level recording as set forth in claim 6 or 7. (9) Use indium CH_4 and O_2 as recording media
An optical information recording/reproducing apparatus capable of multilevel recording according to claim 6, 7, or 8, characterized in that a recording film sputtered in a mixed gas of N_2 and N_2 is used as the recording film.