JP3691412B2 - Information writing control method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk information writing control method and apparatus, and more particularly, to a write control method for accurately writing information to an optical disk apparatus that writes and reads information by a laser beam, and to the same. Relates to the device.
[0002]
[Prior art]
In recent years, with the increase in capacity of computer systems, expectations for optical disks such as magneto-optical disks and phase change optical disks have increased as rewritable large-capacity files. For this reason, an optical disc apparatus for optically recording large-capacity document data and image information (image information) on a disc-like medium has been developed, and products aiming at the OA market have already come out.
[0003]
Information recording on an optical disk is performed, for example, by reversing the magnetization of the medium or changing the crystal state of the medium by the thermal effect of laser beam irradiation on the disk medium. Among the recording methods, in particular, in so-called long hole recording in which the length of a write bit (for example, laser irradiation) and a non-write bit (for example, laser non-irradiation) bears information, an accurate bit shape is written on the medium. Is particularly important in reducing read errors and increasing device reliability.
[0004]
The optical disk to which the present invention is applied includes a magneto-optical disk and the like as long as it is of the long hole recording system.
[0005]
FIG. 30 shows a compact disc format signal (hereinafter referred to as a CD signal) as an example of long hole recording. In this example, a high signal (“H”) and a low signal (“L”) are 3τ to 11τ (τ is The unit cycle is 230 ns), and the lengths of High and Low are responsible for information.
[0006]
In a conventional optical disk apparatus, for example, a high signal of 5τ is irradiated with a laser only for a time of 5τ (230 ns × 5 = 1150 ns), and a low signal is not irradiated with a laser. .
[0007]
In this case, since the medium is rotating at a constant speed, the pulse width nτ (n = 3 to 11) of the writing information is the bit length on the medium nL (L: unit length on the medium corresponding to time τ). ) And recorded. An example of this state is shown in FIGS. 31 (a) and 31 (b).
[0008]
However, in such a conventional optical disc information writing control method and apparatus, when the rotation speed of the medium is decreased (L is shortened) in order to perform higher density recording, the bit writing is performed. Due to the influence of the generated heat, for example, a bit shape as shown in FIG. 31C is written for a long bit of n ≧ 7, and the C / N ratio deteriorates when reading information, resulting in a reading error. There was a problem.
[0009]
In order to cope with this problem, a laser beam corresponding to a high signal is intermittently (pulsed) applied. For example, the method is disclosed in the following documents (1) to (6). Yes.
(1) JP 63-160017 A
(2) JP 63-263632 A
(3) JP 62-229542 A
(4) JP 63-266632 A
(5) JP 63-153726 A
(6) JP 63-266633 A
[0010]
[Problems to be solved by the invention]
However, with the above-described known method, the deterioration of the C / N ratio when the rotation speed of the medium is slowed down cannot be reduced to some extent.
[0011]
That is, when the rotation speed of the medium is decreased, not only the heat generated at the time of writing the bit but also the effect of the remaining heat (residual heat) generated at the time of the previous bit writing becomes large. This is because the writing start position of the bit varies depending on the length of the interspace (the immediately preceding space length), and as a result, the mark length varies.
[0012]
Although the above-mentioned known method is a countermeasure against the heat of the write bit, no countermeasure against the residual heat from the immediately preceding bit is taken, and it cannot be said that the countermeasure against the C / N ratio deterioration at the time of high-density writing is sufficient. .
[0013]
In addition, as related to measures against residual heat from the previous bit,
(7) JP 63-269321 A
(8) Japanese Patent Laid-Open No. 63-302424
(9) Japanese Patent Application Laid-Open No. 64-59633
There are techniques described.
[0014]
However, the contents described in the publications (1) to (9) do not solve the problem of the present invention at all as described later.
[0015]
The technologies described in the above documents are specifically described as follows.
(1) JP 63-160017 A
In this apparatus, the means for controlling the laser light is configured to divide and apply the laser light into a plurality of pulses within a time corresponding to the length of the signal bit, and the laser light control means has the length of the signal bit. The laser light is divided in accordance with this, the leading pulse width of the divided laser light pulse is made larger than the succeeding pulse, and the pulse intensity of each leading pulse of the divided laser light pulse is made larger than the succeeding pulse.
[0016]
Therefore, although writing with pulsed laser light is described, no specific pulsing means is described, and the above problems have not been solved.
[0017]
(2) JP 63-263632 A
In this apparatus, the means for controlling the laser beam is configured to apply the laser beam as two pulses divided immediately before the end of the period to be irradiated within the time according to the length of the signal bit. The one described in Japanese Patent Laid-Open No. 63-160017 is further simplified to obtain the same effect, but the problem cannot be solved for the same reason as described above.
[0018]
(3) JP 62-229542 A
To a pulse oscillator that generates a pulse having a predetermined pulse width corresponding to a light beam irradiation time suitable for the recording sensitivity of a recording layer of a recording medium at a fixed period, and to a laser drive circuit for a pulse signal output from the pulse oscillator And a gate circuit that controls the derivation according to the recording pulse output from the recording pulse generator, and the laser driving circuit controls the light output of the laser light source by the output of the gate circuit.
[0019]
However, it relates to means for pulsing a CD signal, and the pulse width is constant and cannot be changed in principle within a recording pulse.
[0020]
(4) JP 63-266632 A
In an information recording method in which recording is performed by changing the atomic arrangement of a recording medium by irradiating an energy beam such as light or an electron beam, a single pulse width shorter than the time required for the center of the energy spot to pass from end to end of the recording point. A recording point is formed by one or a plurality of pulses. However, it is more preferable if writing is performed with a pulsed laser beam and the pulse width is narrower than 3/4 of the bit length, more preferably smaller than 1/2, and particularly preferably smaller than 1/4. However, it does not describe any pulsing method.
[0021]
(5) JP 63-153726 A
The amount of energy of each radiation pulse in a group of successive radiation pulses has already been generated by the temperature rise in the information body caused by one radiation pulse and previous radiation pulses in that group. It is determined by the position within the group in consideration of the condition that the sum total with the temperature is always constant, and consists of all nine claims relating to the method and apparatus. This is an application by a co-author of the paper cited in the present specification and has almost the same contents as the paper, and the problem cannot be completely solved (details will be described later).
[0022]
(6) JP 63-266633 A
It is disclosed that the write signal pulse is divided into three parts: a start part, an intermediate part, and a terminal part. However, the pulse width of each part can be set independently, and pulse prohibition means for prohibiting the generation of each pulse independently is not disclosed, and for the purpose of obtaining the optimum write bit shape as described later Is not suitable and the problem cannot be solved completely. Further, there is no description about controlling the length of the write signal in accordance with the immediately preceding space length, which is a main component of the present invention.
[0023]
(7) JP 63-269321 A
The laser light control means shortens the laser light irradiation time when forming a long bit, or shortens the laser light irradiation time when forming a bit with a short blank length immediately before. It is what. Specific means for shortening the laser beam irradiation time when forming a bit with a short blank length immediately before the formation of a bit such as a CD master or write-once disc, etc. Is not shown at all. Furthermore, it is normal writing and no description is given of pulsed writing. Therefore, there is no suggestion of a specific technique that can solve the above-described problems.
[0024]
(8) Japanese Patent Laid-Open No. 63-302424
The laser light control means shortens the irradiation time of the laser light when forming a bit with a short previous blank length, and accelerates the start of laser light irradiation when forming a bit with a long previous blank length. In the same manner as the technique described in the seventh publication, the specific technical means and pulsed writing are not described at all, and there is no suggestion of a specific technique that can solve the problem.
[0025]
(9) Japanese Patent Application Laid-Open No. 64-59633
In order to avoid the phenomenon that the diameter of the subsequent writing bit becomes large when the writing interval is short in the optical disk apparatus for bit position recording, the bit laser is detected when the interval is short and the writing laser power is reduced. Is. It has been disclosed to detect the pulse interval and change the amount of laser light accordingly. However, this example is not mark length recording, but bit position recording, and the recording method is completely different. Therefore, the problem cannot be solved as in the techniques described in the above publications (7) and (8).
[0026]
Therefore, the present invention maintains a precise recording bit shape, that is, a recording bit having a predetermined shape whose writing start position is a specified position, even when high-density writing is performed, and obtains a reproduction signal with a good C / N ratio. It is an object of the present invention to provide an optical disc information writing control method and apparatus capable of performing the same.
[0027]
[Means for Solving the Problems]
In order to achieve the above object, the optical disc information writing control method according to the present invention corrects not only the influence of heat generated during the bit writing but also the influence of residual heat generated during the immediately preceding bit writing.
[0028]
  That is, the present invention provides an information write control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which the length of a recording bit bears information. The length of the information signal corresponding to the space signal part immediately before is counted by a pulsed clock, and a control signal indicating the space length corresponding to the count value is output at the end of the space signal part, and the mark signal part Is configured as a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses and a space portion between the pulses of the plurality of pulses,By delaying the generation position of at least one of the first to nth pulses by a delay time corresponding to the control signal indicating the space length, and changing only the width of the space portion in the series of pulse trains. , Controlling the series of pulse trains according to the space length,The mark signal portion is written by applying the controlled pulse train to the light irradiation means.
  According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. A space recognition unit that counts the length of the information signal corresponding to the space signal portion immediately before by a pulsed clock and outputs a control signal indicating a space length corresponding to the count value at the end of the space signal portion; The information signal corresponding to the mark signal portion is configured as a series of pulse trains composed of first to n-th (n (integer) ≧ 2) plural pulses and a space portion between the plural pulses,By delaying the generation position of at least one of the first to nth pulses by a delay time corresponding to the control signal indicating the space length, and changing only the width of the space portion in the series of pulse trains. , The series of pulse trains according to the space length.And a pulse control means for controlling, and writing the mark signal portion by applying the controlled series of pulse trains to the light irradiation means.
  Further, the present invention provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, and a control signal indicating a space length corresponding to the count value is output at the end of the space signal portion, and the mark signal portion The corresponding information signal is configured as a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses, and at least the first pulse of the series of pulse trainsThe generation position of the leading edge is delayed by a delay time corresponding to the change of every 1τ of the space length based on the control signal indicating the space length, the pulse width of the pulse is compressed, and the series of pulse trains are changed,The mark signal portion is written by applying the controlled series of pulse trains to the light irradiation means.
  According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. A space recognition unit that counts the length of the information signal corresponding to the space signal portion immediately before by a pulsed clock and outputs a control signal indicating a space length corresponding to the count value at the end of the space signal portion; and The information signal corresponding to the mark signal portion is formed into a series of pulse trains composed of a plurality of first to nth (n (integer) ≧ 2) pulses, and at least the first pulse of the series of pulse trainsThe generation position of the leading edge is delayed by a delay time corresponding to the change of the space length every 1τ based on the control signal indicating the space length, and the pulse width of the pulse is compressed to change the series of pulse trains.Pulse signal control means, and writing the mark signal section by applying the controlled series of pulse trains to the light irradiation means.
  Here, it is preferable to reset the count value at the end of the information signal corresponding to the mark signal portion.
  Further, it is preferable that the space recognition means resets the count value at the end of an information signal corresponding to the mark signal portion.
  Further, it is preferable that the relationship of the pulse period T = τ.
  Further, the present invention provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is And outputting the information signal corresponding to the mark signal portion as a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses and a space portion between the pulses of the plurality of pulses, By controlling the generation position of the pulse, the interval of the space portion can be set and changed, and at least the interval of the space portion of the series of pulse trains is changed to the pulse. The setting is changed according to the control signal indicating the space length so that the position of the last pulse of the row becomes a specified position based on the information signal corresponding to the mark signal portion, and the controlled pulse train is used as the light irradiation means. It is characterized in that writing is performed by application.
[0029]
According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is The space recognition means for outputting, and the information signal corresponding to the mark signal section is made into a series of pulse trains composed of a plurality of pulses and a space portion between each of the plurality of pulses, and the generation position of the pulses in the series of pulse trains Is configured so that the interval of the space portion can be set and changed, and at least the space portion of the series of pulse trains Pulse train control means for changing the interval according to the immediately preceding space length recognized by the space recognition means so that the position of the last pulse of the pulse train becomes a specified position based on the information signal corresponding to the mark signal section And is provided.
[0030]
Further, the present invention provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which a recording bit length carries information. An information signal corresponding to: a) a start part for quickly raising the temperature of the medium to a writable temperature; b) an intermediate part for keeping the raised medium temperature in balance with heat dissipation; and c) a light beam. An information signal corresponding to the mark signal part is divided into a plurality of pulses for each of the three parts. Thus, a series of pulse trains pulsed into a plurality of first to n-th (n (integer) ≧ 2) pulses corresponding to the length of the information signal corresponding to the mark signal portion is formed, and the mark signal portion Equivalent When the signal length changes corresponding to the information, the number of pulses in the intermediate part of the pulse train is changed, and the length of the information signal corresponding to the space signal part immediately before the mark signal part Is counted by a pulsed clock, the count value is held at the end of the space signal section, a control signal indicating a space length corresponding to the count value is output, and the first pulse generating means is configured to output the series of pulse trains. The first pulse is generated by controlling the pulse width of the first pulse at the top of the first pulse in accordance with the control signal indicating the space length, and the second to n-th pulse generating means are the second to second pulses of the series of pulse trains. a first pulse having a pulse width corresponding to the change in the space length generated by the first pulse generating means and the second to nth pulse generating means generated by the second to nth pulse generating means. First By forming the series of pulse trains with the pulses, the series corresponding to the change in the space length so that the position of the last pulse of the pulse train is a prescribed position based on the information signal corresponding to the mark signal portion. The pulse train is controlled, and writing is performed by applying the controlled pulse train to the light irradiation means.
[0031]
According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. An information signal corresponding to: a) a start part for quickly raising the temperature of the medium to a writable temperature; b) an intermediate part for keeping the raised medium temperature in balance with heat dissipation; and c) a light beam. An information signal corresponding to the mark signal part is divided into a plurality of pulses for each of the three parts. Thus, a series of pulse trains pulsed into a plurality of first to nth (n (integer) ≧ 2) pulses corresponding to the length of the information signal corresponding to the mark signal portion is formed, and the mark signal portion Equivalent When the signal length changes corresponding to the information, the pulse forming means for changing the number of pulses in the intermediate part of the pulse train, and the information corresponding to the space signal part immediately before the mark signal part Space recognition means for counting the length of the signal with a pulsed clock, holding the count value at the end of the space signal section, and outputting a control signal indicating the space length corresponding to the count value; Pulsing means controls the pulse width of the first pulse at the head of the series of pulse trains in response to the change in the space length based on the control signal, and generates the first pulse; , Second to nth pulse generating means for generating the second to nth pulses of the series of pulse trains, respectively, and the first to nth pulses generated by the first to nth pulse generating means are output. A first pulse having a pulse width corresponding to a change in the space length generated by the first pulse generator and a second pulse generated by the second to nth pulse generators. By configuring the series of pulse trains with the nth pulse, the space length can be changed so that the position of the last pulse in the pulse train is a specified position based on the information signal corresponding to the mark signal section. The above-described series of pulse trains are controlled, and the controlled pulse train is applied to the light irradiation means to perform writing.
[0032]
Here, it is preferable that the count value is reset at the end of the information corresponding to the mark signal portion.
[0033]
The space recognition means preferably resets the count value at the end of information corresponding to the mark signal portion.
[0034]
Further, the present invention provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is And the pulse generation means configures an information signal corresponding to the mark signal portion into a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses, and at least of the series of pulse trains At least the first pulse width of the first pulse is controlled in accordance with the change of the space length every 1τ based on the control signal, and the first to nth pulses are generated, respectively. By configuring the series of pulse trains with the first to nth pulses controlled according to the length of the pulse train, the length of the start portion of the pulse train is set to at least the head of the pulse train according to the recognized immediately preceding space length. Control is performed by controlling the width of the pulse.
[0035]
According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is The output space recognition means and the information signal corresponding to the mark signal section constitute a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses, and at least at least one of the series of pulse trains. Both the first pulse width of the first pulse is controlled in accordance with the change of the space length every 1τ based on the control signal, and the first to nth pulses are generated, respectively. By configuring the series of pulse trains with the first to n-th pulses controlled according to the length of the pulse train, the length of the start portion of the pulse train is determined according to the immediately preceding space length recognized by the space recognition means. And pulse train control means for controlling the pulse train by controlling at least the width of the first pulse of the pulse train.
[0036]
Further, the present invention provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is And outputting the information signal corresponding to the mark signal portion as a series of pulse trains composed of a plurality of first to n-th (n (integer) ≧ 2) pulses and a space portion between the pulses of the plurality of pulses, The width of the space portion can be set and changed by controlling the generation position of the pulse, and at least the width of the space portion of the series of pulse trains is changed to the space. That setting is changed in response to a control signal indicative of the length, characterized by.
[0037]
According to the present invention, there is provided an information write control device for writing an information signal composed of a mark signal portion and a space signal portion on an information recording medium in which a recording bit length carries information. The length of the information signal corresponding to the space signal portion immediately before is counted by a pulsed clock, the count value is held at the end of the space signal portion, and a control signal indicating the space length corresponding to the count value is The space recognition means for outputting, and the information signal corresponding to the mark signal section is made into a series of pulse trains composed of a plurality of pulses and a space portion between each of the plurality of pulses, and the generation position of the pulses in the series of pulse trains The interval of the space portion can be set and changed by controlling the at least space portion of the series of pulse trains. , Characterized by providing a pulse train control means for setting change in accordance with the immediately preceding space length, which is recognized by the space recognition means.
[0038]
The present invention also provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc for recording information whose length of recording bits bears information. The information signal corresponding to is a series of pulse trains composed of a plurality of pulses, and part or all of the pulse train is an information signal corresponding to the immediately preceding space signal section so that the position of the last pulse of the pulse train is a specified position. The time compression is performed in accordance with the length of the pulse, and the pulse train compressed in time is applied to the light irradiation means to perform writing.
[0039]
Further, the present invention provides an optical disc information writing control device for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc for recording information whose length of recording bits bears information. And a space recognition for recognizing the length of the information signal corresponding to the space signal immediately before the information signal corresponding to the mark signal portion. And a time compression means for time-compressing a part or all of the pulse train based on the recognition result of the space recognition device so that the position of the last pulse of the pulse train is a specified position. And
[0040]
The present invention also provides an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc for recording information whose length of recording bits bears information. The information signal corresponding to is a series of pulse trains composed of a plurality of pulses and a space portion between the pulses, and the pulse or / and space portion width of the pulse train is the prescribed position at the position of the last pulse of the pulse train. As described above, control is performed according to the length of the information signal corresponding to the immediately preceding space signal portion, and writing is performed by applying the controlled pulse train to the light irradiation means.
[0041]
Further, the present invention provides an optical disc information writing control device for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc for recording information whose length of recording bits bears information. Information corresponding to the space signal portion immediately before the information signal corresponding to the mark signal portion, and pulse forming means for converting the information signal corresponding to the portion into a series of pulse trains composed of a plurality of pulses and a space portion between the pulses Space recognition means for recognizing the length of the signal, and control of the width of the pulse or / and space portion of the pulse train based on the recognition result of the space recognition means so that the position of the last pulse of the pulse train is a specified position And a pulse train control means.
[0042]
The present invention also relates to an information writing control method / apparatus for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc that performs information recording in which a recording bit length carries information. The information signal corresponding to the signal part is a series of pulse trains pulsed into a plurality of pulses, and the pulse width and / or amplitude of the series of pulse trains is immediately before the information signal corresponding to the mark signal part. In accordance with an information signal corresponding to the space signal portion, the writing end position is controlled to be a mark signal portion having a predetermined shape at a specified position, and writing is performed by applying the controlled pulse train to the light irradiation means. It is characterized by doing so.
[0043]
The present invention also relates to an information writing control method / apparatus for writing an information signal composed of a mark signal portion and a space signal portion on an optical disc that performs information recording in which a recording bit length carries information. An information signal corresponding to the signal part; a) a start part for quickly raising the temperature of the medium to a writable temperature; b) an intermediate part for keeping the raised medium temperature in balance with heat radiation; c) By dividing the information signal corresponding to the mark signal part into a plurality of pulses, the mark signal is divided into three parts: an end part that keeps the temperature drop caused by the end of the light beam irradiation at a predetermined condition. When a series of pulse trains corresponding to the length of the information signal corresponding to the portion is formed and the length of the information signal corresponding to the mark signal portion changes corresponding to the information, the pulse of the intermediate portion of the pulse train is changed. And the width and / or amplitude of the pulses of a series of pulse trains according to the information signal corresponding to the space signal portion immediately before the information signal corresponding to the mark signal portion, Control is performed so that the writing end position is a mark signal portion having a predetermined shape at a specified position, and writing is performed by applying the controlled pulse train to the light irradiation means.
[0044]
These control the pulse so that the position of the final pulse becomes a specified position.
[0045]
In the present invention, the write signal of the recording bit is pulsed, and the length and / or amplitude of the pulse train of the pulsed write signal of the recording bit is a space signal immediately before the write signal. It is controlled according to the length. Therefore, it is possible to effectively correct the influence of heat generated when writing the recording bit immediately before the recording bit, and a good bit shape can be obtained regardless of the mark length and the space length.
[0046]
Therefore, even when high-density writing is performed, an accurate recording bit shape is written only by adding simple hardware, and a high-quality reproduction signal having a good C / N ratio can be obtained.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
"Analysis of problems in conventional technology"
First, the present inventor examined an accurate analysis of the above-mentioned problems and a solution thereof. The first problem, that is, the phenomenon that the normal bit shape is not written when the rotational speed of the medium is slowed down for high density recording, can be considered as follows. When the rotation speed of the medium is a normal rotation speed, the local temperature rise of the medium due to laser beam irradiation and the temperature drop due to heat dissipation of the medium maintain a certain balance, and the boundary where writing by the thermal effect is performed (hereinafter, The writing boundary) almost coincides with the laser beam. Accordingly, for example, if a bit of 11τ is written, a bit of length 11L and width d (d: diameter of the laser beam) is formed on the medium.
[0048]
On the other hand, if the rotation speed of the medium is reduced for high-density recording, the laser beam irradiation energy per unit area increases, so the temperature drop due to heat dissipation cannot be met in time, and heat gradually accumulates as the irradiation time increases. As a result, heat also flows to positions before and after the beam irradiation position. Since there is a lower limit to the energy of the laser beam necessary for writing in a certain time due to the thermal effect, for example, even when the rotation speed is halved, the laser beam energy is halved for writing. The above phenomenon always occurs.
[0049]
Therefore, when writing a long bit such as 7τ or more, for example, the heat accumulation increases as the laser beam advances to the 2L position, the 3L position, and the 4L position, and the influence of heat on the adjacent position gradually increases. The boundary also extends beyond the laser beam diameter d. At the end of the bit, that is, in the above example, in the vicinity of the 7L position, the laser beam irradiation ends immediately and the temperature drop due to heat radiation becomes dominant, so the writing boundary becomes almost the beam diameter.
[0050]
Considering such a model, the bit shape shown in FIG. 31 (c) can be explained. In particular, in a phase-change medium that performs recording by changing the reflectivity by changing the crystalline state (crystalline phase), the high-low information is written by changing the crystalline state by rapid cooling or slow cooling from the molten state. The influence of the heat flow from the position is remarkable.
[0051]
As an example, consider a phase change medium in which high information is written by rapid cooling. If the write bit length becomes longer than a certain length (for example, 7τ or more) and there is an influence of heat on the adjacent position, for example, the 3τ position. Is affected by the flow of heat from the 4τ position, from 5τ at the 4τ position, and then sequentially from the (n + 1) τ position at the nτ position. As a result, it is gradually cooled rather than rapidly cooled. It becomes a close condition. In such a state, writing high information of a bit longer than a certain degree becomes very unstable. In order to obtain a stable high writing state even when writing a long bit, that is, to realize a stable rapid cooling state, the laser beam is intermittently applied between the writing bit lengths nτ (n = 3 to 11) ( It is effective to perform writing by irradiating in a pulsed manner. D.J.Gravesteijn et al "Phase-change optical data storage in GaSb", Applied Optics,26, 4772 (1987) describe writing by a pulse train having a width of 80 ns at a frequency of 4.3 MHz (τ = 230 ns).
[0052]
The present inventor wrote various high write bit lengths (hereinafter referred to as mark lengths) on the medium according to the example of the above-mentioned literature, and observed the bit shape. As a result, as described in the above document, in writing with a pulse train having a constant pulse width, even if the pulse width is changed or the optical power is appropriately changed, the mark length 3τ It was not possible to find a pulse width condition that realized a good bit shape over 11τ. That is, in the case of 3τ having the shortest mark length, a good bit shape was obtained when writing with 3 pulses having a pulse width of 180 ns, but 11τ having the longest mark length was written with 11 pulses of this condition. In other words, the light energy is too large, and the bit shape abnormality similar to the writing by the continuous light shown as the conventional example has occurred.
[0053]
On the other hand, under the pulse width condition of 120 ns that gives a good bit shape in the case of 11τ, the bit of 3τ could not be written normally due to the lack of light energy.
[0054]
A method for recording by changing the pulse width of the pulse train constituting the mark is disclosed in JP-A-63-266633 as described above. In this disclosed example, the pulse train is divided into three parts, that is, a start part, an intermediate part, and a terminal part, and the pulse width of the start part and the terminal part is made larger than the pulse width of the intermediate part. However, in the method disclosed here, when each part of the start part (hereinafter referred to as the start part), the intermediate part, and the end part (hereinafter referred to as the end part) is composed of a plurality of pulses, the pulse width of each pulse in each part is set. Since it cannot be set independently, it is not suitable for the purpose of obtaining an optimum write bit shape under various combinations of pulse widths.
[0055]
Therefore, the present inventor considered a device to be described later that can independently set each pulse width of the pulse train constituting the mark, and written and written various mark lengths under various pulse width combinations. The bit shape was observed.
[0056]
FIG. 1 shows an example of a suitable write pulse condition obtained from the above observation result and the write bit shape at that time. Specifically, FIG. 1A uses an input signal that repeats 7τ high information (mark) and 7τ low information (space), and uses a pulse period T = τ (230 ns), a first pulse width 200 ns, Write bit when writing is performed under conditions of 2 pulse width 150 ns (starting part), third pulse width 120 ns, fourth to sixth pulse width 100 ns (intermediate part), and seventh pulse width 130 ns (ending part) The shape is shown. Significant improvement in bit shape was seen compared to writing with a continuous laser beam (FIG. 30 (c)).
[0057]
FIG. 1B shows a first pulse width of 200 ns, a second pulse width of 150 ns (starting portion), a third pulse width of 120 ns, and a fourth to tenth pulse width of 100 ns for a 7τ space and an 11τ mark. An intermediate part) shows a bit shape written under the condition of an eleventh pulse width of 130 ns (end part). Similarly, FIG. 1C shows a first pulse width of 200 ns, a second pulse width of 150 ns (starting portion), and a third pulse width of 130 ns (ending portion, in this case, an intermediate portion) for a 7τ space 3τ mark. The bit shape written under the condition of (no pulse is output) is shown. In any case, a good bit shape was obtained as in FIG.
[0058]
To consider the physical meaning of this experimental result,
(1) The part that quickly raises the medium to a writable temperature .... (starting part)
(2) The part that keeps the temperature rising at the start part in balance with the heat dissipation of the medium ... (intermediate part)
(3) A part that keeps the temperature drop that occurs with the end of laser beam irradiation under favorable conditions .... (End part)
It can be interpreted that it consists of the above three functions. Therefore, when the mark length is changed, changing the length of the intermediate portion by increasing / decreasing the pulse of the intermediate portion merely changes the length of the portion having the function of maintaining the temperature, and does not depend on the mark length. It can be fully understood that a good bit shape can be obtained.
[0059]
However, as shown in FIGS. 1 (a) and 1 (b) for the intermediate pulse, a better bit shape can be obtained by making the pulse width of the leading pulse wider than other pulse widths.
[0060]
In the experiments described so far, only the mark length has been focused, and the space length has been made constant for convenience. However, in an actual CD signal, information is recorded by a combination of marks and spaces having a length from 3τ to 11τ. Accordingly, the space from writing a mark to writing the next mark always changes between 3τ and 11τ. In particular, in a phase change medium in which recording is performed by changing the crystal state by rapid or slow cooling of the medium, there is a concern about the influence of residual heat when writing the immediately preceding bit.
[0061]
In order to clearly grasp the influence of the residual heat, the space length was changed from 3τ to 11τ, and the accompanying change in the mark length was observed. FIG. 32 shows this state.
[0062]
(In_0.40Sb_0.60)_0.94Ge_0.06Using a recording film having the composition: 60 nm, the experiment was performed under a linear velocity of 1.2 m / s.
[0063]
The horizontal axis indicates the space length immediately before the writing mark of interest, and shows the results when the writing mark length is 3τ7τ and 11τ. In the figure, x indicates data for normal writing (laser power 5 mW) without pulse formation, and ◯ indicates data when pulse formation is performed under the above-described preferred pulse conditions (laser power 12 mW).
[0064]
In the case of normal writing, if the space length immediately before is 3τ and 11τ, the difference in writing mark length reaches 300 ns (equivalent to 1.3τ), and it is impossible to correctly determine the mark length. .
[0065]
When pulsed writing is performed, the difference in writing mark length between the previous space lengths 3τ and 11τ is 150 ns, which is certainly improved. However, since this value corresponds to 65% of the value of τ (= 230 ns) and exceeds 0.5 τ which is a criterion for determining each mark length at the time of reading, all the mark lengths cannot be correctly determined. .
[0066]
Since the influence of the residual heat is great in this way, the actual slot recording signal represented by the CD signal cannot be accurately written and accurately read only by pulsing with the conventional technique.
[0067]
The following embodiment solves the above-mentioned problems, accurately writes a long hole recording signal represented by a CD signal, and can obtain a high-quality reproduction signal with a good C / N ratio and an optical disc information writing control. A method and apparatus are provided.
[0068]
“First Example”
2 to 7 are views showing a first embodiment of an optical disk information writing control method and apparatus according to the present invention. FIG. 2 is an overall configuration diagram of the optical disk information writing control apparatus. In this figure, the writing control apparatus is roughly divided into an input CD signal D₀(Corresponding to the write signal of the recording bit) is input and the CD signal D₀Are delayed within a predetermined range, and a CD signal (first delay signal D) delayed by the first delay circuit 1 is delayed.₁) For further delaying within a predetermined range, and output signals (first and second delay signals) of the first and second delay circuits 1 and 2. D₁, D₂) To generate a start part control signal A, an intermediate part control signal B, and an end part control signal C, and a write signal of a recording bit, that is, an input CD by these control signals. Signal D₀Is divided into three parts, a start part, an intermediate part, and an end part, and a pulsing circuit (pulse forming means) 4 for generating a pulse corresponding to each part, and the input CD signal D₀And a pulse train control circuit (pulse train control means) 10 for recognizing the space length immediately before and controlling the length of the pulse train according to the space length.
[0069]
The pulsed output from the pulsing circuit 4 is input to the laser diode 5, and the laser diode 5 generates a laser beam based on this pulsed output. The laser beam is condensed through the lens 6 and irradiated to the optical disk medium 8 rotating around the rotation axis 7 to perform long hole recording. The laser diode 5 and the lens 6 constitute laser irradiation means 9.
[0070]
The first delay circuit 1 and the second delay circuit 2 are preferably digital means such as a shift register that can obtain a delay synchronized with the clock, but may be analog means such as a delay line. In the present embodiment, the first delay time is described as τ and the second delay time is set as 2τ. However, this is not essential, and the minimum space length (in the case of a CD signal) determined in advance by a code standard. May be 3τ) or less, and may be decimal numbers such as 1.5τ and 0.25τ.
[0071]
The details of the pulsing circuit 4 are shown in FIG. 3, and only one set of the pulsing circuit 4 is shown in FIG. 3 for the sake of convenience. However, in practice, each of the start part, the intermediate part, and the end part is shown in FIG. The circuit shown is necessary.
[0072]
In FIG. 3, the pulsing circuit 4 includes a clear circuit 11, a counter 12, a delay circuit 13, a decode circuit 14, a pulse width setting circuit 15, and an OR gate 16 as a collective circuit. The clear circuit 11 includes a delay circuit 17, an inverter 18, and a NAND gate 19. The clear circuit 11 generates a signal for clearing the counter 12 in synchronization with the falling edges of the control signals A, B, and C, and outputs the signal to the clear terminal of the counter 12. . The control signals A, B, and C are input to the count enable terminal of the counter 12, and the pulsed clock is input to the clock terminal. Taking the case where the control signal A is first input to the counter 12 as an example, the counter 12 starts counting when the signal becomes “H” and stops counting when the signal becomes “L”. At this time, a clear pulse having a pulse width determined by a delay time (for example, 50 ns) of the delay circuit 17 is applied from the clear circuit 11 to the clear terminal of the counter 12, and the contents of the counter 12 are reset to “0”.
[0073]
Specifically, as shown in FIG. 4, when a control signal A having a width of 2τ is input, the content of the counter 12 changes from 0 → 1 → 2 → 0. 2 which is the output of the counter 12⁰Digit (A, A bar), 2¹Digit (B, B bar), 2²Digit (C, C bar), 2^ThreeThe digit (D, D bar) is input to the decoding circuit 14 at the next stage, and the decoding circuit 14 is constituted by, for example, AND gates 20a to 20n (n = 15 in this embodiment). The reason why n = 15 is that 15 from “1” to “F” are used and “0” is not used.
[0074]
The pulse width setting circuit 15 includes mono-multivibrators 21a to 21n (first to n-th pulse generating means, n = 15 in the present embodiment). These include, for example, the mono-multivibrator 21a (first pulse generating means). ), A pulse width adjusting means 22 made of a volume is provided. The same applies to the other mono-multivibrators 21b to 21n (second to n-th pulse generating means), and therefore each pulse width of the first pulse, which will be described later, is set independently. Is possible.
[0075]
Here, when the content of the counter 12 is “0”, A = B = C = D = 0, A bar = B bar = C bar = D bar = 1, and all the inputs of the decoding circuit 14 are “ Since there is no combination that becomes “1”, the output side of the decoding circuit 14 remains “0” and no signal appears. On the other hand, when the content of the counter 12 is “1”, A = B bar = C bar = D bar = 1 and A = B = C = D = 0, so that A / B bar / C bar / D bar Appropriately delayed (eg, 50 ns) pulsed clock appears only on the output side of the AND gate 20a with the input combination, triggering the mono multivibrator 21a. When the content of the counter 12 is “2”, since B = A bar = C bar = D bar = 1 and B bar = A = C = D = 0, a pulsed clock appears only in the AND gate 20b. Trigger the multivibrator 21b. Hereinafter, although not shown in order as the contents of the counter 12 become “3, 4, 5,... 15”, the mono multivibrators 21c, 21d. That is, the mono multivibrators 21a to 21n generate the first pulse, the second pulse,..., The nth pulse (n = 15) to be generated by the start part control signal A. If the width of the start part control signal A is 2τ as in the example shown in FIG. 4 and this is not changed, only two AND gates and mono multivibrators are required.
[0076]
The outputs of the mono multivibrators 21a to 21n are synthesized by an OR gate 16 as a collective circuit, and output as a start part pulse in which the first pulse, the second pulse,..., The nth pulse appear sequentially on the time axis. The intermediate part pulse and the end part pulse are generated and output in the same manner as the start part pulse. Furthermore, the start part pulse, the intermediate part pulse, and the end part pulse are synthesized by a collective circuit (not shown) (similar to the collective circuit of FIG. 4), and applied to the laser diode 5 as a pulsed output shown at the bottom end of FIG. The
[0077]
Next, in describing the control signal generation circuit and the pulse train control circuit, first, the basic operation of the control signal generation circuit will be described with reference to the timing chart shown in FIG.
[0078]
Input CD signal D₀Passes through the first delay circuit 1 and the first delay circuit D₁And the same signal D₁Further passes through the second delay circuit 2 and the second delay signal D.₂It becomes. In the present embodiment, the first delay time is described as τ and the second delay time is 2τ for convenience, but this is not essential, and the minimum space length (CD signal determined in advance by the code standard) In this case, it may be 3τ) or less, and may be decimal numbers such as 1.5τ and 0.25τ.
[0079]
The signal D entering the control signal generating circuit 3₀, D₁, D₂Is subjected to a logical operation, A = D₁・ (D₁Bar D₂Bar), B = (D₀・ D₁) ・ (D₁・ D₂) And C = (D₁・ D₂A control signal called B-bar is formed.
[0080]
Here, “·” represents a logical product, and “bar” represents negation. The control signal A is a start part control signal, B is an intermediate part control signal, and C is an end part control signal. Input CD signal D₀The timing of each control signal A, B, and C with respect to is shown in FIG. 4, but the pulse width of the start part control signal A coincides with the delay time of the second delay circuit 2 (2τ in the example of FIG. 3) and ends. The pulse width of the part control signal C coincides with the delay time of the first delay circuit 1 (τ in the example of FIG. 3), and the pulse width of the intermediate part control signal B is first and second from the pulse width of the input CD signal. This corresponds to the value obtained by subtracting the delay time of the second delay circuits 1 and 2. This is a natural result obtained from the logical operation forming the control signals A, B, C. Therefore, when changing the pulse width of the start part control signal A and / or the pulse width of the end part control signal C, the delay time of the second delay circuit 2 and / or the delay time of the first delay circuit 1 are set. Change it.
[0081]
Each control signal A, B, C enters the pulse forming circuit 4 and is converted into a pulse having a number corresponding to the pulse width of each control signal A, B, C and an appropriate pulse width, and drives the laser diode 5. Then, the optical disk medium 8 is irradiated and long hole recording is performed.
[0082]
Next, the operation of the pulse train control circuit will be described with reference to FIGS. In the pulse train control circuit, first, when the space length is shorter than this signal length, a reference signal for reducing the mark length (finally the length of the pulse train) is generated. As shown in FIG. 5, the generation of the reference signal includes a mono multivibrator 43 having a clear terminal, delay circuits 44 and 45, inverters 46 and 47, an AND gate 48, and a NAND gate 49, and constitutes a pulse train control circuit 42. The chart is reset at the falling edge of the input CD signal as shown in FIG.₀D delayed by τ from the signal₁The circuit is set at the falling edge of the signal, and the reference signal E is generated therefrom. Reference numeral 50 denotes a pulse width adjusting means of the mono multivibrator 43 made of volume, and adjusts the reference signal length to 7τ, for example.
[0083]
FIG. 7 shows the timing of the CD signals of mark 3τ, space 3τ, mark 3τ, space 7τ, mark 5τ as an example. (A) is the input CD signal D.₀, (A) is the first delayed signal D₁, (C) is the second delay signal D₂, (D) is the third delay signal D_Three(O) is D₀・ D₁, (F) is D₁・ D₂, (Ki) is D₁・ D_Three, (K) are intermediate control signals B (B = (D₀・ D₁) ・ (D₁・ D₂)), (G) is signal A (A = D₁・ (D₁・ D₂) Bar) and (co) are end control signals C (C = (D₁・ D₂) · B bar), (sa) is the start part auxiliary signal D (D = D)₁・ (D₁・ D_Three) Bar), (S) is a reset signal, (S) is a set signal, (C) is a reference signal E (E = 7τ), (S) is a signal F (F = D · E), (T) is a signal A ′ (A ′ = A · F bar), (H) is a pulsed clock T (T = τ), and (T) is a pulsed output.
[0084]
In FIG. 7, the reference signal E originally has a length of 7τ. However, if a reset signal comes before this (5τ in the example of FIG. 7), it becomes “L”, and “H” is again set by the set signal after τ. Set to “L” after 7τ. The timing at which the reference signal E is set is the first delay output D₁Because it coincides with the fall of₁If E is “H” at the beginning of the mark, the immediately preceding space length is shorter than 7τ, and if E is “L”, it can be determined that it is 7τ or more.
[0085]
When the space length is shorter than 7τ, the start portion auxiliary signal D is used to shorten the mark length and control the pulse train. The signal D is a first delayed signal D₁Is delayed by a length (τ in the example of FIG. 7) to reduce the mark length._ThreeUsing D = D₁・ (D₁Bar D_ThreeBar). Next, D · E = F (mark length control signal) is generated from the reference signal E, and A · F bar = A ′ is further generated as a start portion control signal. A ′ has a start position delayed by τ when the immediately preceding space length is shorter than the reference signal, and is the same start position as A when it is longer than the reference signal length. Since the end position is exactly the same as A, the write mark length can be controlled according to the length of the immediately preceding space length. Instead of the control signals A, B, and C described in the basic operation section of the control signal generation circuit, A ′, B, and C are input to the pulsing circuit 4 as control signals, so that the previous space length is obtained. A pulsed output (lower end in FIG. 7) having a pulse train having a length corresponding to is obtained.
[0086]
From the above, in this embodiment, the write signal of the recording bit is divided into three parts, each of the three parts is pulsed, and the pulse width of each pulsed pulse can be set independently. The medium can be irradiated with a laser beam under the optimum conditions for each of the three portions. Furthermore, since the space length immediately before the write signal can be determined and the length of the output pulse train can be controlled according to the space length, the influence of the residual heat from the immediately previous write bit can be effectively corrected, and the high density Even when writing is performed, an accurate recording bit shape can be maintained and a reproduction signal with a good C / N ratio can be obtained.
[0087]
In the above description, the counter of the pulsing circuit is binary 4 digits, but the present invention is not limited to this, and it is possible to increase the number of digits and add more pulse width setting circuits. Needless to say. Of course, the pulse width may be determined by digital means such as a counter instead of the mono multivibrator that generates the first to nth pulses.
[0088]
Furthermore, although an analog mono-multivibrator is used to generate the reference signal of the pulse train control circuit, it can be realized by digital means such as a counter. Further, in the above description, an example in which only one reference signal is provided is shown for convenience, but a plurality of such reference signals are combined, and a plurality of start part auxiliary signals are combined, for example, a mark length −τ for space lengths 3τ to 4τ. It goes without saying that finer control may be performed such that the mark length is −0.5τ at 5τ to 7τ, and the mark length is unchanged at 8τ to 11τ.
[0089]
“Second Example”
FIG. 8 is a diagram showing a second embodiment of the present invention. In this embodiment, the period T of the pulsed clock is (1/2) · τ. That is, as shown in the timing chart of the operation in FIG. 8, in this embodiment, since the resolution of pulsing is double that of the first embodiment, a finer pulse width can be set. In this case, if the pulse width condition of the pulse at the start portion is to be the same as in the first embodiment, the pulse width settings of the mono multivibrator 21a and the mono multivibrator 21c are set to be the same as in the first embodiment, and the mono multivibrator 21b is set. The mono multivibrator 21d may be set to a small pulse width so that the trailing edge of the pulse does not exceed the trailing edge of the pulse set by the mono multivibrator 21a or the mono multivibrator 21c.
[0090]
In the pulsing circuit 4 shown in FIG. 3, the outputs of the mono multivibrator 21a, the mono multivibrator 21b,..., The mono multivibrator 21n are logically synthesized by the OR gate 16 that is a collective circuit. There will be no failure. Alternatively, the mono multivibrator 21a and the mono multivibrator 21c may be set to (1/2) · τ, and the remaining pulse width may be set by the mono multivibrator 21b and the mono multivibrator 21d. The same applies to the end portion. It goes without saying that the resolution may be increased by making the period of the pulsed clock finer to (1/3) · τ and (1/4) · τ.
[0091]
“Third Example”
9 to 11 are views showing a third embodiment of the present invention. In this embodiment, as shown in FIG. 9, a plurality of pulsed outputs (Ch1 and Ch2) are output from a pulsed circuit (pulsed means) 31 as shown in FIG. 2 channels) are output to the first and second optical output generation circuits 32 and 33, respectively, and are supplied to the laser diode 34. The first pulse and the second pulse of the start, middle, and end of each channel Pulse: A feature is that pulse prohibiting means 35 for prohibiting generation of the nth pulse independently is provided.
[0092]
The pulse prohibiting means 35 is composed of a switch group such as a snap switch, and is specifically shown as shown in FIG. That is, a pulse inhibition means 35a is provided at the next stage of the AND gates 20a... 20n as the decode circuit 14 and is connected to the mono multivibrators 36a to 36n. Is generated. Similarly, the other pulse prohibiting means 35b is provided, connected to the mono multivibrators 38a to 38n, and further integrated by the collective circuit 39 to generate the channel 2 of the pulsed output.
[0093]
FIG. 11 shows the timing of the third embodiment and the state of the light output of the laser diode 34. The mark length 5τ, the width 2τ of the start portion control signal A, the width τ of the end portion control signal C, the pulsed clock T = The case of (1/2) · τ is shown as an example.
[0094]
In this embodiment, T = (1/2) · τ, so that four pulse prohibiting means 35 are effective at the start part, two at the end part, and 16 at the middle part at maximum. Further, when the channel 1 and channel 2 pulse prohibiting means 35a and 35b are set as indicated by O in the figure (b), the pulsed output of each channel becomes as shown in the figure (c). Since the outputs of the channel 1 and the channel 2 are connected to the first optical output generation circuit 32 and the second optical output generation circuit 33, respectively, the optical output of the laser diode 34 is the first as shown in FIG. The two pulses have a light output of a second magnitude that is larger than normal, and the other pulses have a light output of a normal first magnitude.
[0095]
As described above, the pulse forming circuit 31 has a plurality of channels and has the pulse prohibiting means 35 for prohibiting the generation of each pulse independently, so that not only the pulse width as in each of the above embodiments but also the optical output can be obtained. Since it can be changed, the optimum write condition can be determined more finely.
[0096]
In this embodiment, the number of channels is 2, but it may be 3 or more so that the light output can be changed more finely. Further, the pulse prohibiting means does not necessarily have a switch, and it is needless to say that means for deleting the pulse generating means at that position or disconnecting the connection may be used.
[0097]
“Fourth Example”
FIGS. 12 and 13 are diagrams showing a fourth embodiment of the present invention. This embodiment corrects the influence of the residual heat coming from the immediately preceding write bit described in the section “Analysis of problems in the prior art”. As a means for controlling, the optical output of the write start unit pulse is controlled according to the immediately preceding space length. As the control signal, the mark length control signal F shown in the first embodiment is used. That is, as shown in FIG. 12, a light output control circuit 51 to which the mark length control signal F is input is provided in a part of the structure of FIG. 9 shown as the structure of the third embodiment, and the second light output generation circuit. 33. Then, as shown in the timing chart shown in FIG. 13 by the light output control circuit 51, the amplitude of the writing start portion pulse is changed according to the immediately preceding space length based on the mark length control signal F, and the light output is finely controlled. Is done. Therefore, the influence of the residual heat can be effectively corrected even with the method of the present embodiment.
[0098]
In the above description, for the sake of convenience, only one reference signal E and only one mark length control signal F are shown. However, as in the first embodiment, a plurality of reference signals E are used.₁~ E_nTo multiple mark length control signals F₁~ F_nNeedless to say, the light output control circuit may be configured to output a light output having a magnitude corresponding to each mark length control signal, and finer control may be performed.
[0099]
  "Fifth Example"
  FIG. 14 is a diagram showing a result of correcting the influence of residual heat according to the first and second embodiments of the present invention, and FIGS. 15 to 17 are diagrams showing a fifth embodiment of the present invention. In addition, this embodiment is claimed in claim 1,2This corresponds to the described invention.
[0100]
In the first embodiment, the mark writing start position is controlled by increasing or decreasing the number of generated pulses according to the length of the immediately preceding space length in order to correct the influence of the residual heat from the previously written bit. . FIG. 14 shows the case where the second embodiment is applied to the first embodiment, that is, the pulsed clock is (1/2) τ, and the pulse widths of the above-mentioned preferred write pulse conditions (pulsed clock τ) are substantially the same. Under a write pulse condition that is halved, the residual heat correction 0.5τ (the third delay signal D_ThreeThe delay time is 0.5τ) and the reference signal length is 6τ (the remaining heat correction is applied only when the immediately preceding space length is 3τ to 5τ). In the figure, ◯ indicates no residual heat correction, and Δ indicates the case where the residual heat correction is performed under the above conditions. When the immediately preceding space length is 3τ to 5τ due to the correction, the writing mark length is shortened by about 0.5τ, so that it falls within ± 0.5τ which is the discrimination criterion of the read signal, and the effect of the residual heat correction appears. Yes.
[0101]
However, with this method, the resolution of the writing start position is limited by the period of the pulsed clock. Therefore, if you want to make finer corrections, for example, if you want to change the write start position by 10 ns each time the previous space length changes by 1τ, a pulsed clock with a period of 10 ns (frequency 100 MHz) is required. Realization is difficult with the TTL used. In addition, if it is desired to control the write start position in response to every change of 1τ in the immediately preceding space length from 3τ to 11τ, nine reference pulses are required, and the amount of hardware increases considerably. .
[0102]
In the fifth embodiment, such fine writing start position control is to be realized with simple hardware. FIG. 15 is a diagram showing the configuration of the portion necessary for this purpose. In this figure, the pulse train control circuit of this embodiment is provided with the necessary number of leading pulses (the first pulse shown in FIG. 3). It includes a passage group 54, space recognition means 55 for recognizing the immediately preceding space length, and passage selection means 56 for selecting the passage of the first pulse according to the recognition result. The space recognition means 55 includes a counter 57 that counts the space length in units of 1τ, inverters 58 and 59, a delay circuit 60, a NAND gate 61, and AND gates 62a to 62n as decode circuits to which the output signal of the counter 57 is input. Consists of. The passage group 54 includes delay lines (DL) 63a to 63n connected in series as passages for the leading pulse, and the passage selection means 56 inputs ANDs to which the space lengths and outputs of the delay lines 63a to 63n are input. The gate 64a to 64n and an OR gate 65 as a collective circuit generate a trigger signal of the mono multivibrator 21a shown in FIG.
[0103]
In the above configuration, as shown in the timing chart of FIG.₁Inverted signal D₁If the bar is input to the enable terminal of the counter 57, the space portion is input and D₁When the bar becomes “H”, the counter 57 starts counting the clock. When the space part ends and the mark part is entered, D₁The bar becomes “L”, and the counter 57 stops while maintaining the previous contents. That is, when the mark portion starts, the counter 57 functions as a memory that stores information on the immediately preceding space length. Therefore, by decoding the contents of the counter 57, only one decoder output corresponding to the immediately preceding space length becomes “H” when the mark portion starts. FIG. 16 shows an example of outputs of 3 decoders (corresponding to space length 3τ) and 10 decoders (corresponding to space length 10τ). This output is used to select the passage of the first pulse. Counter 57 is D₁Reset at the rising edge of the bar and start counting the next space length.
[0104]
On the other hand, the leading pulse (starting first pulse) serving as the trigger of the mono multivibrator 21a shown in FIG. 3 is taken out before that and enters the delay lines 63a to 63n as the leading pulse passage group 54. The passage group 54 includes delay lines 63a to 63n (DL₁₁, DL_Ten...... DL_ThreeThe subscript attached to each of the delay lines 63a to 63n corresponds to the immediately preceding space length. Since the output of each of the delay lines 63a to 63n is connected to AND gates 64a to 64n controlled by the outputs of the AND gates 62a to 62n serving as the decoding circuit, a delay time path corresponding to the immediately preceding space length is provided. Only the passed pulse is taken out and triggers the mono multivibrator 21a (see FIG. 3). In this way, the space length immediately before the mark portion is recognized and the head pulse generation position is controlled accordingly.
[0105]
For example, by providing taps on the delay lines 63a to 63n in units of 5 ns, for example, the head pulse generation position can be controlled with this resolution, and a resolution of 10 ns or less can be achieved with a commonly used TTL. it can.
[0106]
In the above description, the number of passage selection means 56 is one, and only the start first pulse is delayed to correct the residual heat. However, a plurality of passage selection means 56 are provided, and the first to nth pulses of the start part are delayed. It is also possible to correct the residual heat. In this case, the space recognition means 55 may be one. Furthermore, the delay time of each passage selection means corresponding to each of the first to nth pulses of the start part is, for example, that the delay time of the first pulse when the immediately preceding space length is 3τ is 150 ns, The delay time is 140 ns, the delay time of the nth pulse is gradually changed to (150-10n) ns, or the delay time of the first pulse when the immediately preceding space length is 10τ is 20 ns. If the delay time of the two pulses is gradually changed to 15 ns,..., And the delay time of the nth pulse is (20-5n) ns, an output pulse train as shown in FIG. 17 can be obtained. Residual heat correction can be performed.
[0107]
“Sixth Example”
18 and 19 are views showing a sixth embodiment of the present invention. The control of the leading pulse position according to the space length immediately before described in the fifth embodiment is suitable for recording with a constant rotational linear velocity represented by CD (compact disc) among slot recording, It cannot be applied as it is to recording with a constant rotational angular velocity represented by a magnetic disk. In other words, in recording with a constant rotational angular velocity, the linear velocity increases as it goes to the outer peripheral portion of the disk with a larger rotational radius, and the recorded length on the medium is longer than that of the inner peripheral portion even if a signal having the same time is recorded. Long. Therefore, even if the immediately preceding space length is the same, the distance on the medium is longer at the outer peripheral portion than the inner peripheral portion, and the influence of the residual heat is small.
[0108]
Therefore, in the sixth embodiment, the delay time of each of the delay lines 63a to 63n is changed according to the rotation radius of the disk.
[0109]
In recording with a constant rotational angular velocity, which is an object of application of the present embodiment, there is provided means for enabling the current rotational radius position to be known from the position of the optical head or the address recorded in the medium. For example, a signal represented by a binary code is generally used. Therefore, in this embodiment, as shown in FIG. 19, the AND gates 71a to 71n as decoding circuits are inputted with radial position signals represented by binary signals, and an AND gate as an appropriate number of radial position decoders provided. Only one corresponding output from 71a to 71n is "H". Output S of each AND gate 71a-71n₁~ S_nIs an n-group AND gate 72A as a radial position selection gate as shown in FIG.₁~ 72A_n72B₁~ 72B_n... 72N₁~ 72N_nThe other input terminals of these gates are connected to the output taps 1, 2... N of the delay lines 63a to 63n. Each gate 72A₁~ 72A_n... 72N₁~ 72N_nAre grouped for each group and input to the OR gates 73a to 73n, and the next stage is provided with a space recognition means 55 partially shared with the fifth embodiment. Therefore, the output S of the radial position selection gate₁~ S_nBy setting one of them to “H”, one of the output taps 1, 2,..., N of the delay lines 63a to 63n is selected, and only the leading pulse signal passing through this output tap is the next stage delay. In addition to being input to the line, the first pulse is output by subsequent logical processing.
[0110]
The delay time between the input and output taps of each delay line 63a to 63n does not need to be the same for each delay line, and may be set according to the characteristics of the disk medium. Further, the passage selection means corresponding to the immediately preceding space length is exactly the same as in the fifth embodiment.
[0111]
In the above description, an example in which the residual heat is corrected only by the first pulse (starting portion first pulse) has been shown. However, similarly to the fifth embodiment, a plurality of circuits shown in FIGS. Needless to say, the residual heat correction using the nth pulse may be performed.
[0112]
  "Seventh Example"
  20 to 27 are views showing a seventh embodiment of the present invention. In this embodiment, the residual heat correction according to the immediately preceding space length is performed more finely than each of the embodiments described above..
[0113]
The pulse train control circuit 80 of this embodiment shown in FIG. 21 includes a space recognition circuit 81 and a time compression circuit 82.
[0114]
The space recognition circuit 81 is a circuit similar to the space recognition means 55 shown in FIG. 15, and generates a space length signal corresponding to the immediately preceding space lengths 3τ to 11τ.
[0115]
The time compression circuit 82 includes a voltage control delay circuit 83 and a delay time control circuit 84. The voltage control delay circuit 83 is a circuit whose delay time varies depending on the applied control voltage, and is composed of an element generally called VCVDL (Voltage Controlled Variable Delay Line) in which a variable capacitance diode and an inductance are combined. In this embodiment, two elements made by JPC are used, and a variable range of 1020 ns to 700 ns is obtained with respect to a control voltage of 0 to 15 V, as shown in FIG.
[0116]
Considering the case where, for example, a sawtooth control voltage having a length of 3τ (690 ns) shown in FIG. 23 is applied to the voltage control delay circuit 33, the delay time of the voltage control delay circuit 83 is equal to the elapsed time on the horizontal axis. Changes as shown in FIG. A pulse input to the voltage control delay circuit 83 at the timing of the elapsed time 0 propagates through the delay circuit 83. During the propagation, the delay time of the delay circuit 83 changes every moment as shown in FIG. Yes. Therefore, the pulse is delayed by an average value of the delay time (1020 ns) of the delay circuit 83 at the input timing and the delay time (700 ns) in the steady state, that is, (1020 + 700) / 2 = 860 ns, and appears at the output terminal. Further, the pulse input at the timing of the elapsed time of 300 ns is delayed by (880 + 700) / 2 = 790 ns because the delay time of the delay circuit 83 at that timing is 880 ns. As described above, the delay time decreases as the pulse is input with a delay from the time when the sawtooth control voltage is applied. However, since the control voltage is no longer applied to pulses input with a delay of 690 ns or more, the delay times are all 700 ns.
[0117]
FIG. 25 shows an example in which the pulse train is time-compressed based on the above principle. The residual heat correction value in the immediately preceding space length 3τ is 160 ns, and the corresponding sawtooth control voltage is 15 V and 690 ns shown in FIG. Further, it is assumed that the input pulse train is suitably pulsed with a mark length of 4τ shown in (a).
[0118]
The leading edge of the first pulse is delayed and output after 860 ns. Also, since the trailing edge of the first pulse is input after 100ns, it is delayed by (974 + 700) / 2 = 837ns from the above principle, and output at the time of 837 + 100 = 937ns if the elapsed time origin is the reference. Is done. Therefore, the first pulse width of the output pulse train is 937-860 = 77 ns. Similarly, the leading edge of the second pulse is 948 ns, the trailing edge is 1025 ns, and the pulse width is 77 ns, similar to the first pulse. Similarly, the third pulse has a leading edge of 1036 ns and a width of 62 ns, the fourth pulse has a leading edge of 1125 ns and a width of 46 ns, the leading edges of the fifth and sixth pulses are 1213 ns and 1301 ns, and the widths are 46 ns and 39 ns, respectively. Since the control voltage is in a steady state when the seventh pulse is input, the seventh and eighth pulses are output after being delayed by 700 ns. In this way, the output pulse train shown in (c) is obtained. In practice, a pulse train in which various mark lengths and space lengths are combined is input, but the position of the trailing edge of the final pulse is kept at a position delayed by 700 ns from the input pulse. That is, while maintaining the relationship between the mark length and the space length of the input signal, only the pulse train corresponding to the sawtooth control voltage width from the beginning of each pulse train is time-compressed for the residual heat correction.
[0119]
In the method of the fifth embodiment shown in FIG. 17, even if the residual heat correction is performed by delaying the first pulse by 160 ns and delaying the second, third, and fourth pulses by 150 ns, 140 ns, and 130 ns, respectively, each space portion is compressed. Only the pulse width itself is not changed. On the other hand, the method of the present embodiment is characterized in that not only each space portion but also each pulse width is compressed at the same rate.
[0120]
Taking the pulse train shown in FIG. 25A as an example, the total pulse width is 590 ns, and the ratio of the pulse train length to 885 ns (pulsing rate) is about 67%. On the other hand, in the method of the fifth embodiment shown in FIG. 17, since the total pulse width is the same and only the pulse train length is 885-160 = 725 ns, the pulsing rate is 590/725 = 0.81, 81%. And larger than the input pulse train. On the other hand, in the method of this embodiment, the total pulse width is 487 ns, and the pulse rate is 487/725 = 0.67, approximately 67%, which is the same as the pulse rate of the input pulse train.
[0121]
The pulse rate can also be considered as the energy density of the writing laser beam, and keeping it the same as the input pulse train, which is a suitable pulse condition, can write a more accurate bit shape even when residual heat correction is performed. It means that.
[0122]
Further, the range of the residual heat correction can be applied not only to the start part pulse but also to the intermediate part pulse. That is, in the residual heat correction by time compression in this embodiment, in principle, any input pulse train of any shape and combination can be compressed in a similar manner over the entire correction range. Therefore, the pulse train does not necessarily have to be separated into the start portion, the intermediate portion, and the end portion as in the above-described embodiments. For example, each of the mark lengths 3τ to 11τ is composed of a completely different combination of pulse trains. Even if it is, residual heat correction can be performed effectively.
[0123]
FIG. 26 shows an example of the delay time control circuit 84. The delay time control circuit 84 is connected to the first delay signal D.₁A correction range setting circuit 90 for generating a pulse having a width equal to the control voltage width, a sawtooth wave generation circuit 91 for converting the pulse into a sawtooth wave, and a suitable residual heat correction according to the results of the space recognition means 55 and 81 A delay time setting circuit 92 for setting a delay time for the output, and a subtraction circuit 93 for converting the output waveform into a waveform based on 15V.
[0124]
The correction range setting circuit 90 is composed of a mono multivibrator 94, and an input signal D as shown in FIG.₁A pulse having a constant width (see FIG. 27B) starting at the rising edge of each mark is generated. The pulse width can be set by the volume 94R, and in this example, the pulse width is 3τ (690 ns).
[0125]
The pulse is converted as shown in FIG. 27C by the sawtooth wave generation circuit 91 by the differentiation circuit 95 and enters the delay time setting circuit 92. Rf is a feedback resistor of the operational amplifier, and by adjusting this, the linearity of the sawtooth wave can be changed.
[0126]
The delay time setting circuit 92 includes nine sets of amplifiers 96 and switch means 97 corresponding to each space length. Since the amplification factor of each amplifier 96 is determined by Rf / R, the peak value of the output sawtooth wave can be changed by changing the feedback resistances Rf3 to Rf11 of each amplifier 96, and the output of each amplifier 96 is shown in FIG. ) Can be set. Switch means 97 such as an analog switch is connected to the output of each amplifier 96, and the switch is controlled by a space length signal output from the space recognition means 55. Therefore, only one sawtooth wave having a peak voltage corresponding to the space length (residual heat correction value) appears on the output side of the switch means 97.
[0127]
The subtraction circuit 93 is a 1 × inverting amplifier 98, which is composed of an operational amplifier and resistors Re and Rs, and outputs a difference between input terminals. Since the positive input terminal is connected to 15V, the waveform shown in FIG. 27E is output by subtracting the sawtooth wave input to the negative input terminal. Note that Re is for keeping the negative input terminal at 0 V when all the switching means 97 are off. The output of the subtraction circuit is applied to the voltage control delay circuit as a sawtooth control voltage, and the time compression described above is performed.
[0128]
The operational amplifiers used in the above circuits can take an output voltage of 15 V or higher, and are preferably high speed and high slew rate. For example, LH0032CG is preferably used.
[0129]
In the above example, the correction range setting circuit 90 and the sawtooth wave generation circuit 91 are configured by the mono multivibrator 94 and the differential circuit 95 using an operational amplifier. However, the present invention is not limited to this, and for example, an asymmetric time constant is set. Of course, the two circuits may be integrated using a sawtooth wave generated on the base side of the mono multivibrator.
[0130]
FIG. 20 shows an example of a suitable residual heat correction result according to this embodiment. In the figure, ◯ indicates data without correction and Δ indicates data with correction. The write pulse train has the preferable pulse conditions shown in FIG. 25A, the correction value (maximum correction) at the previous space length of 3τ is 160 ns, the correction value at the space length of 4τ is 100 ns, and so on. 20 ns, and all space lengths of 8τ or more were 10 ns. Although there is some nonlinearity, almost complete residual heat correction is performed.
[0131]
“Eighth Example”
28 and 29 show an eighth embodiment. In the seventh embodiment, the range of the residual heat correction (the width of the sawtooth wave control voltage) has been described as 3τ. This is because the minimum mark length of the CD signal is 3τ, and if the correction range is 5τ or more, for example, the final pulse position of the pulse train when the mark length is 3τ is greatly delayed from the specified position. On the other hand, there is a demand for a pulse train having a long mark length of 7τ or more, for example, to perform a wider range correction of, for example, 5τ or more to make the pulse train more similar to the input pulse train. In the present embodiment, the final pulse of a pulse train having a short mark length comes out to a specified position even when a wider range of correction is performed.
[0132]
FIG. 28 shows a delay time control circuit of this embodiment. This delay time control circuit is partly different from the circuit of FIG. 26, and is a switch 102 that selectively connects the negative input side of the subtraction circuit 101 to 0 potential, and a switch control circuit 103 that controls the opening and closing timing of the switch 102. And an inverter 104 that inverts the first delay signal and inputs the inverted signal to the switch control circuit 103. The switch control circuit 103 includes, for example, a first delay signal D₁A switch control signal such as a bar is input. D₁Since the bar is low at the time of marking and high at the time of space, if the switch is controlled at an appropriate timing by the switch control circuit 103 and the switch is controlled, the voltage on the negative input side of the subtracting circuit 101 is just before the end of the mark. It can be set to 0V.
[0133]
Considering the case where a pulse width of 4τ is set by the correction range setting circuit 90 and a pulse train having a mark length of 3τ is input to the voltage control delay circuit 83, the input waveform of the subtraction circuit 101 is as shown in FIG. The output waveform is the waveform shown in FIG. Therefore, when the output waveform of the subtraction circuit 101 is applied to the voltage control delay circuit 83, the delay time of the delay circuit 83 returns to the steady state just before the last pulse of the pulse train having the mark length of 3τ is input. Therefore, the timing at which the final pulse is output is the position of the input time point +700 ns, as in the case of the final pulse of the pulse train of other mark length.
[0134]
For a pulse train having a mark length longer than the pulse width set by the correction range setting circuit 90, the switch 102 is turned off until the control signal having the set pulse width is in a steady state. There is no effect.
[0135]
【The invention's effect】
According to the method of the present invention, even when high-density writing is performed, the influence of the residual heat from the adjacent writing position is effectively corrected so that the accurate recording bit shape, that is, the writing end position is the specified position. A recording bit having a predetermined shape can be written, and a high-quality reproduction signal having a good C / N ratio can be obtained.
[0136]
Further, according to the apparatus configuration of the present invention, the recording bit shape can be written by effectively correcting the influence of the residual heat only by adding simple hardware, and the same effect can be obtained. .
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of write pulse conditions and a write bit shape suitable for explaining the principle of the present invention.
FIG. 2 is an overall configuration diagram of the first embodiment.
FIG. 3 is a block diagram of a pulsing circuit according to the first embodiment.
FIG. 4 is a timing chart showing the basic operation of the first embodiment.
FIG. 5 is a circuit diagram of a reference signal generating circuit according to the first embodiment.
FIG. 6 is a timing chart of the reference signal generating circuit of the first embodiment.
FIG. 7 is a timing chart of the pulse train control circuit according to the first embodiment.
FIG. 8 is a timing chart of the second embodiment.
FIG. 9 is a diagram illustrating an output system of a pulsing circuit according to a third embodiment.
FIG. 10 is a detailed circuit diagram of the pulse prohibiting means of the third embodiment.
FIG. 11 is a timing chart of the third embodiment.
FIG. 12 is a diagram showing an output system of a pulsed output signal of the fourth embodiment.
FIG. 13 is a timing chart of optical output control according to the fourth embodiment.
FIG. 14 is a diagram illustrating a result of correcting the influence of residual heat according to the first and second examples.
FIG. 15 is a block diagram illustrating a configuration of a main part of a pulse train control circuit according to a fifth embodiment.
FIG. 16 is a timing chart of the fifth embodiment.
FIG. 17 is a diagram showing pulse output by a plurality of passage selection units in the fifth embodiment.
FIG. 18 is a diagram showing a circuit for generating a leading pulse according to the sixth embodiment.
FIG. 19 is a diagram showing a circuit for selecting a radial position according to the sixth embodiment.
FIG. 20 is a diagram illustrating an example of residual heat correction according to a seventh embodiment.
FIG. 21 is a diagram illustrating a configuration of a pulse train control circuit according to a seventh embodiment.
FIG. 22 is a diagram illustrating characteristics of the voltage controlled delay circuit according to the seventh embodiment.
FIG. 23 is a diagram illustrating a sawtooth control voltage and a delay time according to the seventh embodiment.
FIG. 24 is a diagram illustrating characteristics of the voltage controlled delay circuit according to the seventh embodiment.
FIG. 25 is a diagram showing an output pulse train subjected to residual heat correction by time compression according to the seventh embodiment.
FIG. 26 is a circuit diagram of a delay time control circuit according to a seventh embodiment.
FIG. 27 is a diagram illustrating operation waveforms of respective parts of the delay time control circuit according to the seventh embodiment;
FIG. 28 is a diagram showing a delay time control circuit for performing a wider range of remaining heat correction in the eighth embodiment.
FIG. 29 is a diagram illustrating operation waveforms of respective parts of the delay time control circuit according to the eighth embodiment;
FIG. 30 is a diagram illustrating an example of a CD signal.
FIG. 31 is a diagram showing the shape of a recording bit according to a conventional method.
FIG. 32 is a diagram showing a change in write mark length depending on the immediately preceding space length;
[Explanation of symbols]
1: first delay circuit (first delay means)
2: Second delay circuit (second delay means)
3: Control signal generation circuit (control signal generation means)
4, 31: Pulse circuit (pulse device)
5: Laser diode
8: Optical disk medium
9: Laser irradiation means
10, 80: Pulse train control circuit (pulse train control means)
32: First optical output generation circuit
33: Second optical output generation circuit
35: Pulse prohibition means
51: Light output control circuit
54: Passage group
55: Space recognition means
56: Passage selection means
81: Space recognition circuit (space recognition means)
82: Time compression circuit (time compression means)
83: Voltage control delay control circuit
84: Delay control circuit
90: Correction range setting circuit
91: Sawtooth wave generation circuit
92: Delay time setting circuit
93101: Subtraction circuit
94: Mono multivibrator
95: Differentiation circuit
96: Amplifier
97: Switch means
102: Switch
103: Switch control circuit

Claims (2)

In an information writing control method for writing an information signal composed of a mark signal portion and a space signal portion on a medium for recording information in which the length of a recording bit bears information,
The length of the information signal corresponding to the space signal portion immediately before the mark signal portion is counted by a pulsed clock, and a control signal indicating a space length corresponding to the count value is output at the end of the space signal portion,
The information signal corresponding to the mark signal portion is configured as a series of pulse trains composed of a plurality of first to nth (n (integer) ≧ 2) pulses and a space portion between the pulses of the plurality of pulses,
By delaying the generation position of at least one of the first to nth pulses by a delay time corresponding to the control signal indicating the space length, and changing only the width of the space portion in the series of pulse trains. , Controlling the series of pulse trains according to the space length,
The mark signal portion is written by applying the controlled pulse train to the light irradiation means;
An information writing control method characterized by the above. In an information writing control device for writing an information signal composed of a mark signal portion and a space signal portion to a medium for recording information in which the recording bit length carries information,
A space that counts the length of the information signal corresponding to the space signal portion immediately before the mark signal portion with a pulsed clock and outputs a control signal indicating the space length corresponding to the count value at the end of the space signal portion. Recognition means;
The information signal corresponding to the mark signal portion is configured as a series of pulse trains composed of a plurality of first to nth (n (integer) ≧ 2) pulses and a space portion between the pulses of the plurality of pulses,
By delaying the generation position of at least one of the first to nth pulses by a delay time corresponding to the control signal indicating the space length, and changing only the width of the space portion in the series of pulse trains. Pulse control means for controlling the series of pulse trains according to the space length;
With
The mark signal portion is written by applying the controlled series of pulse trains to the light irradiation means,
An information writing control device.

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