JP3218556B2 - Optical information recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an optical information recording apparatus, and more particularly, to an apparatus for correcting a pit diameter variation due to conduction heat of recording irradiation light. And an optical information recording device. 2. Description of the Related Art As an apparatus for recording and reproducing information by forming pits on an optical information recording medium (hereinafter abbreviated as an optical disk apparatus), there is a conventional apparatus as shown in FIG. In this optical disk device, the semiconductor laser 3a is excited by a signal current modulated by the laser drive circuit 11. The modulated light output from the semiconductor laser 3a by the excitation is converged on the recording medium 1 through the collimating lens 3b, the beam splitter 3d, and the objective lens 3c, and forms pits 1a to record information. As a method of forming pits, a method of making a hole in a recording film, a method of changing a crystal state of a medium to change a reflectance, and the like are known. At the time of reproduction, the recording film is irradiated with weak light so as not to change, and the light reflected by the medium is reflected by the objective lens 3c,
A signal is detected by a photodiode 3f through a beam splitter 3d and a condenser lens 3e. As a method of recording information, there is a method in which the content of data is made to correspond to the position of a pit. For example, a pit 1a is formed at a location where information is 1 as shown in FIG. The laser drive circuit in such an optical disk apparatus supplies a current that emits a constant weak light during reproduction and a strong pulse-like current during recording.
What is described in the gazette is well known. [0004] In the above-described optical disk device, it is necessary to control the size of the pits correctly, and when the pit diameter becomes small, the detection signal decreases. Conversely, if the pit diameter becomes too large, adjacent pits may fuse with each other, making it impossible to identify the pits. Since the size of the pit diameter is determined by the irradiation power and irradiation time of the irradiation light, and the thermal characteristics and recording sensitivity of the recording medium, it is desirable to set the irradiation time and irradiation power in advance according to the characteristics of the medium. It is possible to form a pit with a size of. However, as the recording density increases and the distance between pits decreases,
The effect of the heat conduction extends not only to the pits being formed but also to the pits to be recorded next. FIG. 4 is a diagram showing a temperature rise of a recording film when a laser beam is irradiated. The horizontal axis indicates the distance from the center of the irradiated laser spot, and the vertical axis indicates the temperature of the recording film. When the medium is stationary, excess heat diffuses isotropically from the center of the spot. However, when the medium is moving like an optical disk, more heat flows backward as shown in FIG. I do. Therefore, when the pit interval becomes short, the influence of the diffusion heat flowing backward affects the pit to be recorded next. FIGS. 5A and 5B show the heat distribution during recording and the state of pits formed. FIG. 5A shows the recording laser light amount corresponding to data, and FIG. 5B shows the temperature distribution on the recording film. . Heat distribution 1c when the distance from the previous pit is long like d1
On the other hand, when the distance is as short as 2d, the peak temperature of the heat distribution 1d relatively rises due to the influence of the immediately preceding recording pulse. Since a pit is formed in a portion where the temperature of the recording film exceeds a certain threshold temperature th, as shown in FIG. 5C, when the pit interval is short, the pit 1b recorded later becomes large. I will. As is apparent from the above description, in the related art, since recording is performed with irradiation light having a constant power regardless of the pit interval, there is a problem that the pit diameter varies depending on the pit interval. An object of the present invention is to provide an optical information recording apparatus which corrects such distortion of the pit diameter so that pits are always formed with a uniform size even when the recording density is high. It is in. An object of the present invention is to provide an optical information recording apparatus, comprising: means for detecting an interval between recording pulses; and means for switching the amount of irradiation laser light for forming a pit. This is achieved by recording with a relatively small (or large) recording laser light amount for forming a rear pit when the interval is narrow (or wide). As apparent from the above description, the effect of heat propagation depends on the interval between recording pulses, and appears when the pulse interval is short. Therefore, only when the pulse interval is detected and it is short and the effect of heat propagation appears, the pits with the correct diameter are corrected by reducing the amount of laser light and recording the amount of conducted heat from the previous recording pulse. Can be formed. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a block diagram of one embodiment of the present invention. FIG. 1 shows an embodiment in which the present invention is applied to an optical disc apparatus capable of additionally recording, wherein 1 is an optical disc, 2 is a spindle motor, 3 is an optical head, and the optical head 3 is a semiconductor laser 3a, a collimating lens. 3b and an objective lens 3c. The recording signal 4s is inputted from the input terminal 4 and inputted to a D flip-flop 5a (hereinafter abbreviated as D-FF), while being inputted to two NAND gates 5c and 5d. Reference numeral 10 denotes a clock input terminal. D-FF
The Q output of 5a is input to the second D-FF 5b and the NAND gate 5d. The inverted Q output of the D-FF 5a is NAN
It is input to the D gate 5c. The Q output of the D-FF 5b is also connected to the NAND gate 5c. Here, D-FFs 5a and 5b and NAND gates 5c and 5
d constitutes means for detecting the interval between recording pulses of the recording signal 4s. The recording signal 4s is transmitted to the first laser driving circuit 7
Is input to AND gates 6a and 6b. Another input terminal of the AND gate 6a is connected to the output of the NAND gate 5d, and the output terminal is connected to the second laser drive circuit 8. The input of the AND gate 6b is connected to both the outputs of the NAND gates 5c and 5d in addition to the recording signal 4s, and outputs an AND signal to the third laser drive circuit 9.
The first, second and third laser driving circuits 7, 8, 9 are connected to a laser diode 3a. Next, the operation of this embodiment having the above configuration will be described. In the present embodiment, when the recording pulse is continuous,
This is a case where correction is applied to each of the clock intervals. First, the case where the recording pulse interval is one clock is detected by the NAND gates 5c of the D-FFs 5a and 5b.
FIG. 7 is a time chart showing the relationship between these signals. FIG. 3A shows a clock signal and FIG. 3B shows a recording signal 4s.
It is. As can be seen from FIG.
P and 4Q are recording pulses at one clock interval, and the recording pulse 4R is an example of a continuous recording pulse. The output 5aQ of the D-FF 5a is
s is a signal delayed by one clock cycle T ((c) in the figure), and similarly, the output 5bQ of the D-FF 5b is a signal delayed by two clock cycles 2T ((d) in the figure). NAND
The output 5cs of the gate 5c is composed of recording pulses 4P and 4Q having a pulse interval of one clock cycle T as shown in FIG.
Has been detected. Similarly, D-FFs 5a and 5b and NAND
The gate 5d detects the case where the recording pulse is continuous, and as shown in FIG.
At R, the output 5ds becomes "L" level. The laser drive circuits 7, 8, and 9 are circuits that supply a drive current to the laser diode 3a according to each input signal. FIG. 8 is a circuit diagram showing an example of the laser drive circuit. The input signal 4s is level-shifted by the transistor 7a and the resistors 7b and 7c, and is connected to the base of the transistor 7d. Transistor 7d, 7f, and the current source 7 e constitute a current switch operates to suck the drive current 7i from the laser diode 3a when the input signal 4s is at the "H" level. Resistor 7g and current source 7
h gives the reference level of the switch. Terminal 7K is a positive power supply and 7j is a negative power supply. The first laser drive circuit 7 supplies a recording signal 4s
Are connected as they are, but the second laser drive circuit 8
The AND signal 6as of the recording signal 4s and the detection signal 5ds of the continuous pulse is input from the AND gate 6a. This signal is a signal obtained by stopping the operation of the second laser drive circuit 8 only when the pulse of the recording signal is continuous as shown in FIG. An AND gate 6bs of a recording signal 4s, a continuous pulse detection signal 5ds, and a signal 5cs for detecting a case where the pulse interval is one clock cycle is supplied to the third laser drive circuit 9 by an AND gate. 6b.
As shown in FIG. 7 (g), the signal 6bs stops the operation of the third laser drive circuit 9 when the pulse of the recording signal is continuous and when the pulse interval is one clock cycle. is there. Since the driving current of the laser diode 3a is the sum of the driving currents 7i, 8i and 9i drawn into the three driving circuits 7 to 9, it is as shown in FIG. 7 (i). That is, when the pulse interval is two clocks or more apart, a pulse current of 7i + 8i + 9i flows, but the third laser drive circuit 9 operates for the recording pulses 4P and 4Q whose pulse interval is one clock cycle. Therefore, only a pulse current of 7i + 8i flows. Furthermore, since both the third laser drive circuit 9 and the second laser drive circuit 8 do not operate for the continuous pulse 4R,
Only the current 7i flows. Therefore, when the pulse interval is short,
Since the recording current flowing through the laser diode 3a is relatively small, the amount of recording irradiation light is also small, and as shown in FIG. 6, it is possible to correct the amount of heat propagated by the recording light irradiated immediately before. As a result, the peak temperature of the recording film becomes constant, and pits having the same size can always be formed on the recording film. 6A, 6B, and 6C, similarly to FIGS. 5A, 5B, and 5C, the recording laser light amount (or the laser diode 3) corresponding to the data, respectively.
a), the temperature distribution on the recording film, and the pit diameter. In this embodiment, three laser driving circuits 7 and
Drive current 7 flowing to laser diode 3a from 8, 9
Although the case where i, 8i, and 9i are equal is shown, these values may be different depending on the characteristics of the medium. For example, FIG.
As shown in (j), it is possible to set 7i: 8i: 9i = 4: 2: 1, and it is possible to form more accurate pits by making it variable depending on the type of medium. . Next, a second embodiment of the present invention will be described. FIG. 9 is a block diagram of the second embodiment, in which the same reference numerals as in FIG. 1 denote the same or equivalent components. FIG.
0 is an operation explanatory diagram of the above embodiment. In this example,
The recording data 4s shown in FIG. 10B is not directly used as a recording signal, the recording pulse width .tau.p is half the data period T as shown in FIG. This is a case where the correction is applied only to the minimum recording pulses P1, P2, and P3. The operation of the second embodiment will be described below in detail with reference to FIGS. The recording data 4s is delayed by one clock cycle T in the D-FF circuit 5a, and becomes a signal 5aQ shown in FIG. The logical product of this signal 5aQ and the signal obtained by inverting the logic of the recording data 4s by the inverter 15 is output from the AND gate 12. The AND signal 12s is shown in FIG. 10D, and is connected to the K input of the JK-FF circuit 11, while the J input is connected to the recording data 4s. The JK-FF circuit 11 has a clock signal CLK.
The Q output signal 11Q becomes 1 when the J input is 1, and returns to O when the K input is 1. Therefore, a signal as shown in FIG. 10E is obtained, and this signal 11Q functions as a control signal for stopping the operation of the second laser drive circuit 8. Now, the width τp corresponding to the recording data 4s
The recording pulse signal having a small width is obtained by forming the logical product of the recording data 4s and the clock signal CLK by the AND gate 13, and is as shown in FIG. The recording pulse signal 13s is directly input to the first laser driving circuit 7, and the recording current 7i shown in FIG. 10G flows through the laser diode 3a. On the other hand, to the second laser drive circuit 8, a signal obtained by gating the recording pulse signal 4s with the Q output signal 11Q of the JK-FF 11 is added. Is not output. Therefore, the second laser driving circuit 8
The current flowing through the laser diode 3a is shown in FIG.
(H). In this embodiment, the ratio of the first and second laser drive currents is 7i: 8i = 2: 1, and the recording current 3ai finally flowing through the laser diode 3a is: FIG.
0 (i). As can be seen from this waveform, the peak currents P1i and P1 of the recording current at which the recording pulse is closest.
Since 2i and P3i are smaller than in other cases, the size of the pit formed is constant regardless of the pit interval as shown in FIG. 10 (j). Next, a third embodiment of the present invention is shown in FIG. 11, and its operation will be described with reference to FIG. In this embodiment, as in the second embodiment, recording is performed by narrowing the recording pulse cycle to half for the recording data. The effect of heat propagation mainly appears behind the pit, but when the recording density increases and the recording pulse interval becomes very close, the effect of heat diffusing in front of the pit cannot be ignored. In the present embodiment, correction for this effect is also performed. In FIG. 11, reference numeral 10 denotes an input terminal of a clock CLK1 which has a period corresponding to recording data, and reference numeral 20 denotes an input terminal of a clock CLK2 having a frequency twice that of the clock CLK1. 21-26
Denotes a D-FF circuit, and 27 to 30 denote AND gates. Other reference numerals indicate the same or equivalent components as those in FIG. As shown in FIGS. 12A and 12B, the rising edges of CLK1 and CLK2 are synchronized.
It is input to each of the D-FF circuits 21-26. The data is synchronized with the rising edge of CLK1 as shown in FIG. 12C, and the pulse width is from T to 3T. D
In the -FF circuits 21 to 23, the data 4s is delayed by one clock cycle, and for example, the output signal 22s of the D-FF circuit 22 is as shown in FIG. These delay signals and CLK1 are input to AND gates 27 to 30, and the outputs of AND gates 28 to 30 are further input to D-FF circuits 24 to 26, and the timing is adjusted by CLK2. D which is a driving signal of the laser diode 3a
The output signals of the FF circuits 24 to 26 are as shown in FIG.
(F) and (g) are obtained. Here, the first
The control signal 24s of the drive circuit 7 is a pulse train having a pulse width T / 2 with respect to the recording data as shown in FIG. The control signal 26s of the second laser drive circuit 8 is:
As shown in FIG. 9G, only the first pulse of the data is output. The control signal 25s of the third laser drive circuit 9 has a pulse width T as shown in FIG.
Is output only for certain data. The currents flown from the laser drive circuit by the above control signal are added, and the drive current shown in FIG. 12 (h) is passed through the laser diode 3a. As a result, the isolated pulse P1 has a large current of 7i + 8i + 9i. In the case of a continuous pulse, the leading pulse P2
Only for a and P3a, the current has a magnitude of 7i + 8i, and for the subsequent pulses P2b, P3b and P3c,
A current having a magnitude of only 7i flows. Here, the current 8i
Is the correction for the heat flowing out behind the pit, and the current 9
i is a correction for the amount flowing out in front of the pit. FIG.
(I) is a diagram showing a state of a pit 1a formed according to the present embodiment. In the third embodiment, three laser driving circuits 7 to 9 can be used in any combination. For example, if the medium has a relatively small influence of heat propagation, only the first and second drive circuits may be operated to correct only the heat flowing behind the pit. Further, recording may be performed only on the first drive circuit 7 for a medium with small heat propagation. The present invention is not limited to the three embodiments described above, and the number of stages to be corrected, the pulse interval, the amount of correction, and the like can be varied depending on the characteristics of the recording medium. Of course, the device obtained by these changes is included in the scope of the present invention. As described in detail above, according to the present invention, the variation in the pit diameter due to the conduction heat of the recording pulse can be corrected in advance, so that the pit diameter is always uniform regardless of the pit interval. And a pit having a desired size can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a first embodiment of the present invention. FIG. 2 is a configuration diagram of an optical disk device. FIG. 3 is a diagram showing a relationship between recording data and formed pits. FIG. 4 is a diagram illustrating a temperature rise of a recording film when recording light is irradiated. FIG. 5 is a diagram showing a relationship between a temperature of a recording film obtained by a conventional apparatus and pits formed. FIG. 6 is a diagram showing the relationship between the temperature of a recording film obtained when recording is performed using the recording apparatus of the first embodiment of the present invention and the pits formed. FIG. 7 is a waveform chart showing the operation of the embodiment of FIG. FIG. 8 is a circuit diagram showing a specific example of a laser drive circuit. FIG. 9 is a block diagram of a second embodiment of the present invention. FIG. 10 is a waveform chart showing the operation. FIG. 11 is a block diagram of a third embodiment of the present invention. FIG. 12 is a waveform chart showing the operation. DESCRIPTION OF SYMBOLS 1 ... optical disk, 2 ... spindle motor, 3 ... optical head, 3a ... laser diode, 5a, 5b ... D-FF circuit, 5c ... NAND gate, 6a ... AND gate G, 7 ...
A first laser driving circuit, 8... A second laser driving circuit, 9
... Third laser drive circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-39138 (JP, A) JP-A-58-158041 (JP, A) JP-A-57-44233 (JP, A) JP-A-58-58 212628 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/0045

Claims (1)

(57) [Claims] In an optical information recording apparatus for recording information by forming a recording section by irradiating a converged laser beam to an optical information recording medium, a pulse detecting means for detecting a pulse interval of a recording information signal, In order to form the recording section corresponding to the pulse width of the recording information signal, a pulse of the recording information signal is divided to generate a plurality of independent recording laser pulses each smaller than the pulse width of the recording information signal. A recording pulse generation unit, and, when a pulse interval between the immediately preceding recording information signal and the recording information signal is equal to or less than a predetermined width, the recording laser light amount of the plurality of recording laser pulses is determined by the pulse interval according to a detection output of the pulse detection unit. Means for changing the recording laser light amount of the plurality of recording laser pulses so as to reduce the width of the recording laser pulse when the width is equal to or more than the width. Recording apparatus. 2. The means for changing the recording laser light amount is such that the second and subsequent recording laser light amounts of the plurality of recording laser pulses are smaller than the first recording laser pulse.
2. The optical information recording apparatus according to claim 1, wherein a recording laser light amount of the plurality of recording laser pulses is changed.