JP2649923B2 - Optical information recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical information recording apparatus, and more particularly, to optical information recording in which fluctuations in pit diameter due to conduction heat of recording irradiation light can be corrected in advance. Related to the device.

(Prior art) Information is recorded by forming pits on an optical information recording medium,
2. Description of the Related Art As a reproducing apparatus (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 a laser drive circuit.
Excited by the signal current modulated by 11. The modulated light output from the semiconductor laser 3a by the excitation is
The light is converged on the recording medium 1 through the collimator lens 3b, the beam splitter 3d, and the objective lens 3c, and forms pits 1a to record information. As a pit type method, 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 detected by a photodiode 3f through an objective lens 3c, 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 in a place where information is 1 as shown in FIG.

The laser drive circuit in such an optical disk device flows a current that emits a constant weak light at the time of reproduction, and flows a strong pulse-shaped current at the time of recording. For example, it is described in JP-A-59-79440. Are well known.

(Problems to be Solved by the Invention) In the optical disk device as described above, 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 is too large, adjacent pits will fuse together, 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 the pits decreases, the effect of heat conduction affects not only the pits in the format but also 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 is diffused isotropically from the center of the spot, but when the medium is moving like an optical disk, more heat is transferred to the rear as shown in FIG. leak. Therefore, when the pit interval becomes short, the influence of the diffusion heat flowing backward affects the pit to be recorded next.

5A and 5B are diagrams showing the heat distribution during recording and the state of the pits formed. FIG. 5A shows the recording laser light amount corresponding to the data, and FIG. 5B shows the temperature distribution on the recording film. In contrast to the heat distribution 1c when the distance from the previous pit is long like d1, the distance is
The peak temperature of the heat distribution 1d in the case of as short as d2 is relatively increased due to the influence of the immediately preceding recording pulse. Since a pit is formed at 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. Would.

As is clear from the above description, in the prior 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 correct such pit diameter distortion,
An object of the present invention is to provide an optical information recording apparatus in which pits are always formed with a uniform size even when the recording density is high. Another object of the present invention is to provide an optical information recording apparatus capable of correcting in advance the variation in the pit diameter due to the conduction heat of a recording pulse.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical information recording medium which irradiates a converged laser beam to form a recording unit to record information. Recording information generating apparatus, the recording pulse generating means for generating a plurality of recording laser pulses by dividing the pulse of the recording information signal to form the recording portion corresponding to the pulse width of the recording information signal; It is characterized in that a means is provided for changing the recording laser light amounts of the plurality of recording laser pulses so that the second and subsequent recording laser light amounts of the recording laser pulses are smaller than the first recording laser pulse.

(Operation) As is clear from the above description, the influence 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.

That is, the pulse interval is detected as shown in FIG. 6, and only when the pulse interval is as short as d2, a small recording light amount 1p is irradiated. Then, as shown in FIG. 6 (b), the heat distribution on the recording surface does not cause the peak temperature 1f to rise too much even if the pulse interval is short, and the pit 1g to be formed has the correct size.

(Example) 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
Semiconductor laser 3a, collimating lens 3b, and objective lens
3c.

The recording signal 4s is input from the input terminal 4 and is input to a D flip-flop 5a (hereinafter abbreviated as D-FF), while 2
Input to the two NAND gates 5c and 5d. Reference numeral 10 denotes a clock input terminal. The Q output of D-FF5a is the second D-FF5b and
Input to NAND gate 5d. The Q output of the D-FF 5a is input to the NAND gate 5c. And Q output of D-FF5b is NA
Connected to ND gate 5c.

Here, the D-FFs 5a and 5b and the NAND gates 5c and 5d constitute means for detecting the interval between recording pulses of the recording signal 4s.

The recording signal 4s is input to the first laser drive circuit 7 and the AND gates 6a and 6b. Another input terminal of AND gate 6a is NA
The output terminal is connected to the output of the ND 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 this embodiment, the correction is applied to the case where the recording pulse is continuous and to the case where the correction is made at the time of one clock interval.

First, the case where the recording pulse interval is one clock is detected by the D-FFs 5a and 5b and the NAND gate 5c. FIG. 7 is a time chart showing the relationship between these signals. FIG. 3A shows a clock and FIG. 3B shows a recording signal 4s.
As is apparent from the figure (b), the recording pulses 4P and 4Q are 1 pulse.
The recording pulse is a recording pulse at a clock interval, and the recording pulse 4R is an example of a continuous recording pulse.

The output 5aQ of the D-FF 5a is a signal obtained by delaying the recording signal 4s by one clock cycle T (FIG. 3 (c)).
The output 5bQ of 5b is a signal delayed by two clock periods and 2T ((d) in the figure). The output 5cs of the NAND gate 5c is shown in the figure (e).
As shown in the figure, the recording pulses 4P and 4Q whose pulse interval is one clock cycle T are detected.

Similarly, the NAND gates 5d of the D-FFs 5a and 5b detect the case where the recording pulse is continuous, and as shown in FIG. 3F, the output 5ds is "L" at the continuous recording pulse 4R. 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 a 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. The transistors 7d and 7f and the current source 7e constitute a current switch, and operate so as to sink the drive current 7i from the laser diode 3a when the input signal 4s is at the “H” level. resistance
The reference level of the switch is given by 7g and the current source 7h. Terminal 7K is a positive power supply and 7j is a negative power supply.

The recording signal 4s is directly connected to the first laser driving circuit 7, while the recording signal 4s is connected to the second laser driving circuit 8.
An AND signal 6as of 4s and the detection signal 5ds of the continuous pulse is input from the AND gate 6a. This signal is 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. 7 (h).

The third laser drive circuit 9 has a recording signal 4s,
An AND signal 6bs of the detection signal 5ds of the continuous pulse and the signal 5cs for detecting the case where the pulse interval is one clock cycle is AN.
Input from D gate 6b. This signal 6bs is shown in FIG.
In this case, the operation of the third laser drive circuit 9 is stopped when the pulse of the recording signal is continuous and when the pulse interval is one clock cycle.

The drive current of the laser diode 3a is divided into three drive circuits 7
Since the sum of the drive currents 7i, 8i, and 9i drawn into .about.9 is as shown in FIG. 7 (i).

That is, when the pulse interval is two clocks or more, a pulse current of 7i + 8i + 9i flows, but the third laser drive circuit 9 does not operate for the recording pulses 4P and 4Q whose pulse interval is one clock cycle. Only the pulse current of 7i + 8i flows. Further, for the continuous pulse 4R, the third laser driving circuit 9 and the second laser driving circuit 8
Because both do not work, only the current of 7i flows.

Therefore, when the pulse interval is short, the recording current flowing through the laser diode 3a becomes relatively small.
The amount of recording irradiation light also decreases, and as shown in FIG. 6, the amount of heat propagated by the recording light irradiated immediately before can be corrected. 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. FIGS. 6 (a), (b) and (c) show the recording laser light amount (or the laser diode 3a) corresponding to the data, respectively, as in FIGS. 5 (a), (b) and (c). Drive current), the temperature distribution on the recording film, and the pit diameter.

In this embodiment, the case is shown where the drive currents 7i, 8i, 9i flowing through the laser diode 3a from the three laser drive circuits 7, 8, 9 are equal, but these values may be different depending on the characteristics of the medium. For example, as shown in FIG. 7 (j), 7i: 8i:
9i = 4: 2: 1 may be set, and it is possible to form more accurate pits by making the variable according to the type of medium.

Next, a second embodiment of the present invention will be described. Ninth
The figure is a block diagram of the second embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or equivalent. FIG. 10 is an operation explanatory diagram of the above embodiment.

In this embodiment, the recording data 4s shown in FIG.
Is not directly used as a recording signal, and the recording pulse width τ _p is
As shown in FIG. 1 (i), the length of the data period T is set to half,
This is a case where the correction is applied only to the recording pulses P1, P2, and P3 in which the recording pulse interval is minimum. The operation of the second embodiment will be described below in detail with reference to FIGS. 9 and 10. The recording data 4s is transmitted by the D-FF circuit 5a for one clock cycle T.
And the signal 5aQ shown in FIG. 10 (c). The AND of the signal 5aQ and a signal obtained by inverting the logic of the recording data 4s by the inverter 15 is output from the AND gate 12. This AND signal 12s is shown in FIG. 10 (d) 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 state of the JK-FF circuit 11 changes in synchronization with the fall of the 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. . Accordingly, a signal as shown in FIG. 10 (e) is obtained, and this signal 11Q acts as a control signal for stopping the operation of the second laser drive circuit 8.

Now, a thin recording pulse signal having a width τ _p corresponding to the recording data 4s is obtained by forming a logical product of the signal data 4s and the clock signal CLK by the AND gate 13, and as shown in FIG. 10 (f). Becomes This recording pulse signal 13s is directly input to the first laser drive circuit 7, and the recording current 7i shown in FIG. 10 (g) flows through the laser diode 3a. On the other hand, to the second laser drive circuit 8, a signal in which the recording pulse signal 4s is gated by the Q output signal 11Q of the JK-FF11 is added, and if the recording signal is continuous, the recording pulse is not output. Has become. Therefore, the second
The current passed through the laser diode 3a by the laser drive circuit 8 is as shown in FIG.

In this embodiment, the ratio of the first and second laser drive currents is
7i: 8i = 2: 1, and finally the laser diode 3a
The recording current 3ai flowing through is as shown in FIG.
As can be seen from this waveform, the peak currents P1i, P2i, P3i of the recording current at which the recording pulse is closest are smaller than in the other cases, and the size of the formed pit is as shown in FIG. The size is constant regardless of the interval.

Next, a third embodiment of the present invention is shown in FIG. 11, and the operation thereof will be described with reference to FIG. In this embodiment, as in the second embodiment, the recording data is recorded with the period of the recording pulse narrowed to half.

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 a clock synchronized with recording data.
CLK1 input terminal, 20 is double frequency clock CLK2
Input terminal. 21-26 are D-FF circuits, 27-30 are AND
The gate. Other reference numerals indicate the same or equivalent components as those in FIG.

As shown in FIGS. 12 (a) and 12 (b), the rising edges of CLK1 and CLK2 are synchronized, and each of the D-FF circuits 21 to 26
Has been entered. The data is as shown in Fig. 12 (c).
Synchronized with the rising edge of CLK1, pulse width from T
Up to 3T. In the D-FF circuits 21 to 23, the data 4s is delayed by one clock cycle.
The output signal 22s of 22 is as shown in FIG. 12 (d). These delay signals and CLK1 are input to AND gates 27 to 30, and
The outputs of the gates 28 to 30 are further input to D-FF circuits 24 to 26, and the timing is adjusted by CLK2.

D-FF circuit 24 which becomes a drive signal of laser diode 3a
The output signals of 26 are as shown in FIGS. 12 (e), (f) and (g). Here, the control signal 24s of the first laser drive circuit 7 is a pulse train having a pulse width T / 2 with respect to the recording data as shown in FIG. 12 (e). The control signal 26s of the second laser drive circuit 8 is such that only the first pulse of the data is output as shown in FIG. Further, the control signal 25s of the third laser drive circuit 9 is output only for data having a pulse width T as shown in FIG.

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 flown to the laser diode 3a. As a result, an isolated pulse
P1 is a large current of 7i + 8i + 9i. In the case of a continuous pulse, only the leading pulses P2a and P3a have 7i
The current has a magnitude of + 8i, and a current having a magnitude of only 7i flows for the subsequent pulses P2b, P3b, and P3c. Here, the current 8i is a correction for the heat flowing out to the rear of the pit, and the current 9i is a correction for the heat flowing to the front of the pit.

FIG. 12 (i) shows pits formed by this embodiment.
It is the figure which showed the situation of 1a.

In the third embodiment, three laser drive 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 magnitude of the correction amount, and the like can be made different depending on the characteristics of the recording medium. Of course, devices obtained by the modifications are included in the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, variation in the pit diameter due to the conduction heat of the recording pulse can be corrected in advance, so that it is always uniform and desired regardless of the pit interval. There is an effect that a pit having a size of 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 block diagram of an optical disk device, FIG. 3 is a diagram showing a relationship between recording data and formed pits, and FIG. FIG. 5 is a diagram showing the temperature rise of the recording film upon irradiation, FIG. 5 is a diagram showing the relationship between the temperature of the recording film obtained by the conventional apparatus and the pits formed, and FIG. 6 is a first embodiment of the present invention. FIG. 7 is a diagram showing the relationship between the temperature of the recording film obtained when recording is performed using the recording apparatus of the example and the pits formed, FIG. 7 is a waveform diagram showing the operation of the embodiment of FIG. 1, and FIG. FIG. 9 is a block diagram of a second embodiment of the present invention, FIG. 10 is a waveform diagram showing the operation thereof, and FIG. 11 is a circuit diagram of the third embodiment of the present invention. FIG. 12 is a block diagram, and FIG. 12 is a waveform diagram showing the operation. 1 ... optical disk, 2 ... spindle motor, 3 ... optical head, 3a ... laser diode, 5a, 5b ... D-FF
Circuit, 5c NAND gate, 6a AND gate, 7 First laser drive circuit, 8 Second laser drive circuit, 9
... A third laser drive circuit,

Claims (1)

(57) [Claims] 1. An optical information recording apparatus for recording information by forming a recording section by irradiating a converged laser beam onto an optical information recording medium, said recording section corresponding to a pulse width of a recording information signal. Recording pulse generating means for generating a plurality of recording laser pulses by dividing the pulse of the recording information signal to form a first recording signal; Means for changing the recording laser light amount of the plurality of recording laser pulses so as to be smaller than the laser pulse.