JPH0850721A - Recording method of light information - Google Patents

Abstract

PURPOSE:To make it possible to form a recording part of a fine ellipse, to obtain thereby an excellent reproduction signal waveform and to lessen jitter at the starting and final ends of the recording part, and to increase a surface recording density of information. CONSTITUTION:A light beam of the largest pulse width, at least, out of pulse- shaped light beams modulated by an information signal is divided into two or more light pulse strings. The pulse width of a first light pulse 1 for forming the starting end part of a recording part (pit 8) is made an integral multiple of the pulse width of each of light pulses 2 to 7 in the pulse string subsequent thereto and the pulse width of each light pulse in the second and subsequent pulse strings is made 1/2 (duty ratio 50%) of the repetition period thereof. Moreover, a recording power of each light pulse in the second and subsequent pulse strings is set to be 1.0 to 2.0 times larger than the recording power of the first light pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recording optical information, and more particularly, to a method of dividing a light beam pulse-modulated by an information signal and applying light from a starting end to a terminating end of a recording section. The present invention relates to a method of averaging irradiation energy of a beam.

[0002]

2. Description of the Related Art Information is recorded on an optical information recording medium by moving an optical information recording medium and an objective lens of an optical head relative to each other while an information signal from the objective lens is formed on a recording film formed on the optical information recording medium. The recording film corresponding to the information signal is applied to the recording film by irradiating a pulsed light beam modulated by
This is performed by forming pits in the perforated recording film, or reversed magnetic domains in the magneto-optical recording film).

When a recording film is continuously irradiated with a light beam having a long pulse width, a part of the thermal energy converted from light energy is used as energy for preheating the recording portion at the beginning of the recording portion, Since thermal energy is accumulated by the action of heat conduction toward the end side of the recording medium, the planar shape of the recording portion becomes a so-called teardrop shape with a wider width toward the terminal side. If the planar shape of the recording section becomes teardrop-shaped, the start and end of the recording section will not be formed accurately. Therefore, the so-called pit-edge type optical information recording that detects the start and end positions of the recording section and reproduces a signal In the medium, the jitter (the amount of fluctuation of the pit edge with respect to the detection window width) becomes large and accurate binarization cannot be performed, and the recording portion becomes wider than the predetermined shape, so that crosstalk is likely to occur. Further, since excessive thermal energy acts on the end side of the recording portion, the substrate and the base film may be deformed, which may increase noise.

Therefore, conventionally, in order to eliminate such inconvenience, the light pulse for forming one recording portion is divided into a plurality of light pulses having a small pulse width, and the light energy applied to the recording film is averaged. Various ideas have been made.

For example, in Japanese Patent Laid-Open No. 63-266633 (hereinafter referred to as a first known example), the light irradiation energy of the first light pulse for forming the starting end portion of the pit (pulse width of light pulse × light). (Recording power of pulse) and the light irradiation energy of the last light pulse for forming the end portion of the pit are larger than the light irradiation energy of the light pulse for forming the middle portion of the pit. ing.

Further, in Japanese Patent Laid-Open No. 3-35425 (hereinafter referred to as a second known example), a recording waveform for forming one recording mark is composed of a recording pulse train consisting of a plurality of pulses, and the recording pulse train. The pulse width of at least one of the first two pulses of the pulse width is larger than the pulse width of each pulse in the subsequent pulse train that follows and is constant regardless of the mark length to be recorded, and each pulse in the subsequent pulse train is There is described a recording method in which the pulse width and the pulse period of are equal to each other.

[0007]

According to the technique described in the first known example among the above-mentioned known examples, since the start end and the end of the recording part are emphasized respectively, the jitter at the edge part of the start end and the end of the recording part is emphasized. However, since the intermediate portion of the recording portion has a narrow and non-uniform shape, the reproduced signal waveform is disturbed, the C / N of the reproduced signal is deteriorated, and a reproduction error is likely to occur. On the other hand, according to the technique described in the second known example, the light pulse is emphasized at the start edge portion of the recording portion, so that the jitter is improved, but at the end edge portion of the pit, the light pulse is weak and the pit width is small. Since the width becomes narrower, the jitter becomes larger. Further, none of the techniques described in the known examples is effective in improving the recording density because the shape of the recording portion does not become a fine oval shape. Further, in any of the techniques described in the known examples, since the combination of divided pulses is complicated, the recording pulse generation circuit becomes complicated and the recording / reproducing apparatus becomes expensive.

The present invention has been made in order to solve the disadvantages of the prior art, and its object is to record a neat ellipse with a recording / reproducing apparatus having a recording pulse generating circuit having a relatively simple structure. An object of the present invention is to provide an optical information recording method capable of forming a part.

[0009]

In order to achieve the above-mentioned object, the present invention provides a recording film formed on an optical information recording medium while relatively moving the optical information recording medium and an objective lens of an optical head. In the optical information recording method of irradiating a pulsed light beam modulated with an information signal from an objective lens on the recording film to form a recording portion corresponding to the information signal and recording information, the information signal is modulated. Of the pulsed light beams thus generated, at least the light beam having the longest pulse width is divided into two or more light pulse trains, and the pulse width of the first light pulse for forming the starting end portion of the recording portion is set to The pulse width of each light pulse in the pulse train is an integer multiple, and the pulse width of each light pulse in the second and subsequent pulse trains is 1/2 or more of the repetition period, and each light in the second and subsequent pulse trains. Of pulse s times the recording power of the first light pulse of the recording power (however, 1.0 <s <2.0) was set to.

When the information signal is modulated by the 1-7 modulation method, among the two or more divided optical pulses,
The pulse width of the first optical pulse is m times the pulse width of each optical pulse in the subsequent pulse trains (where m is a positive integer of 3 or less), and the pulse of each optical pulse in the second and subsequent pulse trains The width is set to 1/2 or more of the repetition cycle, and the recording power of each optical pulse in the second and subsequent pulse trains is t times the recording power of the first optical pulse (however, 1.0 <
Setting t <1.8) gives good results.

Further, when the information signal is modulated by the 2-7 modulation method, the pulse width of the first optical pulse among the two or more divided optical pulses is set to the respective light in the subsequent pulse trains. N times the pulse width of the pulse (where n is a positive integer of 5 or less), and the pulse width of each optical pulse in the second and subsequent pulse trains is ½ or more of its repetition period,
Furthermore, the recording power of each optical pulse in the second and subsequent pulse trains is u times the recording power of the first optical pulse (however,
Setting 1.0 <u <1.8) gives good results.

The information recording method of the present invention can be applied to all known write-once type optical information recording media and rewritable type optical information recording media. However, the main component is tellurium, and a hole is formed in the light beam irradiation portion. It is particularly suitable for a so-called perforated optical information recording medium in which information is recorded by the method.

[0013]

When the pulse width of the light pulse is increased, the light irradiation energy applied to the recording film increases, and the heat energy converted from the light irradiation energy also increases. When such a large amount of heat energy is applied to the starting end portion of the recording portion, a part of this thermal energy is used as energy for preheating the recording portion, so that the formation of holes is promoted and the emphasized starting end portion can be formed. The heat generated by the irradiation of the first light pulse is transferred to the area adjacent to the portion irradiated with the first light pulse. Therefore, by irradiating this adjacent region with the second light pulse whose average irradiation energy is smaller than that of the first light pulse, a pit having the same width as the starting end portion can be formed. Hereinafter, for each area adjacent to it, when the light pulse having the pulse width, the duty ratio, and the recording power listed in the above-mentioned means is sequentially irradiated, the heat energy transmitted from the adjacent area and the heat energy given by the pulse irradiation are Since the total and the thermal energy consumed for forming the recording portion can be almost balanced, a pit having the same width as the starting end portion can be formed up to the end portion. Further, the optical pulse having the pulse width, the duty ratio, and the recording power listed in the above means can be made from a combination of one reference pulse, so that the structure of the recording pulse generation circuit can be simplified. it can.

[0014]

1 (a) to 1 (c) show a light beam splitting method according to an embodiment, the shape of a pit formed by this method, and a reproduction signal waveform read from the pit forming portion.

In this embodiment, as an optical information recording medium, a doughnut-shaped tempered glass having a diameter of 30 cm and a thickness of 1.2 mm is laminated on one surface with an ultraviolet curable resin and an organic base film material such as nitrocellulose. A perforated optical disk having a prepit formed of a body and a replica layer of a light beam guide groove, and a tellurium-selenium-based recording film having a thickness of 27 nm containing tellurium as a main component is provided on the replica layer. I was there. A semiconductor laser having a wavelength of 680 nm was used as the light beam, and the relative linear velocity between the recording track and the light spot was adjusted to 11 m / s.

Writing signals to the optical disc is as follows.
The optical head is tracking-controlled so that the center of the laser spot emitted from the objective lens to the disc surface is always aligned with the center of the guide groove formed on the optical disc, and the focus of the objective lens is always on the recording film. Focusing control was performed so as to match, and the recording laser light modulated corresponding to the recording information was irradiated.

In this example, as shown in FIG. 1A, the longest pulse (8T) in the 1-7 modulation system was divided into seven pulse trains and recorded at a duty ratio of 50%.
In the figure, reference numeral 1 is a first light pulse, 2 is a second light pulse,
Reference numeral 3 is a third light pulse, 4 is a fourth light pulse, 5 is a fifth light pulse, 6 is a sixth light pulse, and 7 is a seventh light pulse. P _w1 is the recording power of the first optical pulse 1, P _w2 is the recording power of the second to seventh optical pulses 2 to 7,
T ₁ is the pulse width of the first optical pulse 1, T ₂ is the second to seventh
The pulse widths of the optical pulses 2 to 7 are shown. Furthermore, t
₁ indicates a pulse interval time between the first optical pulse 1 and the second optical pulse 2, and t ₂ indicates a pulse interval time between the optical pulses after the second optical pulse 2.

The pulse width T ₁ of the first optical pulse ₁ is the second
˜3 times the pulse width T ₂ of the seventh optical pulse 2-7, and the recording power P _w2 of the second to seventh optical pulse 2-7 is 1 of the recording power P _w1 of the first optical pulse 1. It was 6 times. Also,
The pulse interval time t ₁ between the first light pulse 1 and the second light pulse 2 and the pulse interval time t ₂ between each light pulse after the second light pulse 2 are equal to each other, and The pulse interval time t ₂ and the pulse width T ₂ between each optical pulse after optical pulse ₂
And made them equal.

FIG. 1B shows the shape and size of the pit formed when the laser power P _W for writing is set to 6 mW using the recording method of this example. As is clear from this figure, according to the recording method of this example, the elliptical pit 8 having a substantially uniform pit width can be formed from the start end side to the end side of the pit.

FIG. 1C shows the waveform of the reproduction signal read from the recording pit of FIG. 1B. As is clear from this figure, according to the recording method of the present example, it is possible to obtain a clean reproduced signal waveform without disturbance, realize a high C / N, and slice this reproduced signal waveform at an appropriate signal level S. By doing so, signal reproduction with almost no jitter can be realized.

<Comparative Example> FIGS. 2A to 2C show a laser beam irradiation method according to a comparative example, a shape of a pit formed by the irradiation method, and a reproduction signal waveform read from the pit forming portion. Indicates.

In this comparative example, as shown in FIG.
In forming the longest pulse in the -7 modulation method,
The light beam is divided into seven optical pulse trains, the pulse width of the first optical pulse is maximized, and the subsequent optical pulse trains are pulse trains of the same cycle with a smaller pulse width than that, with a duty ratio of 50%. Recorded. Other conditions were the same as those in the above-mentioned example.

FIG. 2B shows the shape and size of the pit formed when the laser power P _W for writing is set to 6 mW using the recording method of this example. As is clear from this figure, according to the recording method of the present example, the pit 11 on the end side is larger than the pit width on the start side, and the pit 11 having an uneven pit width is formed in the middle part.

FIG. 2C shows the waveform of the reproduction signal read from the recording pits of FIG. 2B. As is clear from this figure, according to the recording method of this example, the disturbance of the reproduced signal waveform is large, the C / N is significantly reduced, the jitter is large, and the slice signal level S must be set to an appropriate value. Playback errors are likely to occur.

In the above embodiment, the light beam is divided into a plurality of light pulse trains only for the longest pulse in the 1-7 modulation method, but the light beam is divided for all pits recorded corresponding to the information signal. It can also be divided. Also, the light beam can be split only for pits having a predetermined length or more. Of course, the method of the present invention can be applied to an optical disk device that employs any modulation method other than the 1-7 modulation method.

Further, in the above embodiment, the driving device for the punched type optical disk has been described as an example, but it is needless to say that the invention can be applied to all known optical disk driving devices such as a magneto-optical disk driving device.

[0027]

As described above, according to the present invention,
By irradiating a light beam, the recording portion formed on the optical information recording medium can be formed into a neat ellipse,
In addition, the amount of jitter at the start and end of the recording section can be reduced. Therefore, a good reproduction signal waveform can be obtained from the recorded optical information recording medium, and the areal recording density of information can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical information recording method according to an example.

FIG. 2 is an explanatory diagram of an optical information recording method according to a comparative example.

[Explanation of symbols]

 1 1st optical pulse 2 2nd optical pulse 3 3rd optical pulse 4 4th optical pulse 5 5th optical pulse 6 6th optical pulse 7 7th optical pulse 8, 11 pits

Claims (4)

[Claims] 1. A pulsed light beam modulated by an information signal from an objective lens on a recording film formed on the optical information recording medium while relatively moving the optical information recording medium and the objective lens of the optical head. Of the pulsed light beam modulated by the information signal in the method for recording information by irradiating the recording film with a recording portion corresponding to the information signal and recording the information. The beam is divided into two or more optical pulse trains, the pulse width of the first optical pulse for forming the start end of the recording section is set to an integral multiple of the pulse width of each optical pulse in the subsequent pulse trains, and 2 The pulse width of each optical pulse in the second and subsequent pulse trains is set to 1/2 or more of the repetition period, and the recording power of each optical pulse in the second and subsequent pulse trains is set to 1.0 of the recording power of the first optical pulse. ~ 2. A method of recording optical information, which is characterized by setting the magnification to 0 times. 2. The information recording method according to claim 1,
The information signal is signal-modulated by the 1-7 modulation method, and the pulse width of the first optical pulse of the divided two or more optical pulses is m of the pulse width of each optical pulse in the subsequent pulse train.
(Where m is a positive integer less than or equal to 3), and the pulse width of each optical pulse in the second and subsequent pulse trains is ½ or more of its repetition period, and further in each of the second and subsequent pulse trains. A recording method of optical information, wherein the recording power of the optical pulse is set to 1.0 to 1.8 times the recording power of the first optical pulse. 3. The information recording method according to claim 1,
The information signal is modulated by the 2-7 modulation method, and the pulse width of the first light pulse of the two or more divided light pulses is the pulse width n of each light pulse in the subsequent pulse train.
(Where n is a positive integer less than or equal to 5), and the pulse width of each optical pulse in the second and subsequent pulse trains is ½ or more of its repetition period, and further in each of the second and subsequent pulse trains. A recording method of optical information, wherein the recording power of the optical pulse is set to 1.0 to 1.8 times the recording power of the first optical pulse. 4. The information recording method according to claim 1,
An optical information recording method, wherein the optical information recording medium is a write-once type optical information recording medium containing tellurium as a main component and recording information by forming a hole in a light beam irradiation portion.