JPS63175230A - Optical medium recorder - Google Patents

Abstract

PURPOSE:To improve the dependent properties of the optimum recording power onto the ambient temperatures and the recording frequencies, by driving a light source with a larger and/or smaller current than the normal recording and/or non-recording current for an optional fixed period from the rise and/or the fall of an input signal. CONSTITUTION:A laser is turned on at a writing level at a time point I. In this case, the rise of a medium temperature has the larger gradient than usual since the power is larger than usual at the point I. Then the laser is turned on by the normal recording power at a time point II since the medium temperature rises and exceeds a temperature T0 that is needed for recording. A writing task is through at a time point III and the level of power is lowered than the normal level in order to quicken the drop the medium temperature. In this section specific time is set so that the servo control of a recording device is not affected at all even though the recording power is substantially equal to zero. Therefore the maximum temperature has the large rise and fall gradients at each point of the recording layer of a medium which moves relatively to an illuminated laser spot. Thus it is possible to improve the dependent properties of the optimum power onto the ambient temperatures and the recording frequencies.

Description

DETAILED DESCRIPTION OF THE INVENTION [Second Industrial Application Fields] The present invention relates to an optical medium recording device that writes information onto a medium using light.

[Conventional technology]

Conventionally, recording is performed on media such as optical disks, magneto-optical disks, optical cards, and magneto-optical cards, in other words, media in which digital data is written by moving a light beam relative to the medium (hereinafter simply referred to as an optical medium). A laser (semiconductor laser) is driven in binary lighting (bright/dark) by a digital data signal to irradiate a laser spot onto the medium, and the laser spot and the medium are moved relative to each other to write digital data. There is.

Specifically, a laser diode is driven by applying a rectangular waveform pulse current with a pulse width corresponding to the data to be recorded.

Note that the low level of the laser power is controlled so as not to be completely zero, but in devices using this type of optical medium, a constant plate is used to obtain servo signals for tracking, focusing, etc. This is because a higher level laser beam is required. Here, the output of the laser diode (laser power) is proportional to the difference between the drive current and the dark value current. By the way, the power (wavefocal value) of a laser spot irradiated onto a relatively moving optical medium (either the optical medium moves or the laser beam moves) is determined by the length of the recording unit (recording pit) and the direction of movement of the recording unit. It is known that if the medium is a rotating disk, it will affect the circumferential dimension of the disk, so it is necessary to record the desired length on the medium corresponding to the input signal. In order to accurately form bits, the optimal laser driving current, that is, the intensity of the pulse wave, is determined to irradiate the medium with the optimal laser power depending on various conditions such as the type of medium, the speed of movement of the medium, and the ambient temperature used. (current value) was set in advance and applied to the laser diode.

In conventional technology, even if the laser power irradiated onto the medium changes sharply as shown in Figure 3 (1), at each point on the recording layer of the medium that moves relative to the irradiated laser spot. Since the maximum temperature has a thermal time constant due to the heat capacity of the medium, etc., there is a delay in the rise and fall as shown in FIG. 3 (2). Here, the principle of magneto-optical recording will be explained as an example of optical media recording (thermal recording) in which information is written by heating the medium with light.

First, an optical medium is irradiated with a pulsed laser beam as shown in FIG. 3(1). The maximum temperature at each point on the recording layer of the medium that moves relative to the irradiated laser spot has an upper limit as shown in FIG. 3(2). At the point where the medium's recordable temperature T0 is exceeded, the magnetization direction in the perpendicularly magnetized film, which is the recording layer, becomes easily changeable, and the perpendicular magnetization direction is reversed by the action of an externally applied magnetic field, causing the recording layer to change. As the temperature decreases, the direction of magnetization becomes fixed, and the direction of magnetization becomes fixed (Figure 3)
Binary recording is performed as shown in FIG. In FIG. 3, the hatched portion is perpendicular to the other portions (the direction of illumination is different from that of the other portions), and this will be hereinafter referred to as [1].

If the ambient temperature changes here, the maximum temperature at each point on the recording layer of the medium that moves relative to the irradiated laser spot shifts in the vertical direction as shown in Figure 4 (1), so the maximum temperature The length of [1] of the two plant numbers determined from the intersection of the profile and the recordable temperature T0 is shown in Figure 4 (
2). In other words, when recording with the same laser power, the length of recording (1) increases as the ambient temperature increases, and conversely decreases as the ambient temperature decreases. That is, the optimum recording power depends on the ambient temperature. In other words, in order to record with the same recording length at any ambient temperature, the laser power irradiated to the medium during recording, that is, the laser drive current, must be adjusted by two cycles in accordance with the fluctuations in ambient temperature.

Furthermore, when the frequency of the recording signal (laser drive current) is high and the laser power changes as shown in Figure 5 (1), the duration of one pulse becomes as short as the thermal time constant of the recording layer, and the medium Since the temperature change of the recording layer cannot follow the pulse change, the phase xI for the irradiated laser spot
The maximum temperature at each point on the recording layer of a medium that moves mechanically (in the case of a magneto-optical disk, it moves due to the rotation of the medium or disk) reaches a steady temperature in both high temperature areas (peaks) and low temperature areas (troughs). First, the difference (amplitude) between peaks and valleys becomes smaller, as shown in FIG. 5(2). Therefore, when the recording time signal becomes high in frequency, there is a problem that an accurate pit length cannot be obtained with the optimum recording power at a low frequency. That is, it is the recording frequency dependence of the optimum irradiation laser power.

Second, the present invention aims to improve the above-mentioned problems, that is, the dependence of optimum recording power on ambient temperature and recording frequency.

(Means for solving problem IXI) In order to improve the above problems, that is, the dependence of optimal recording power on ambient temperature and recording frequency, in this study, a correction current is added to the laser drive current during recording. By emphasizing the rise and fall of the laser power irradiated to the medium, the delay in tracking temperature changes in the recording layer is minimized.In other words, the light source is controlled to generate two values of recording current and non-recording current according to the digital input signal. In an optical media recording device that controls and irradiates light onto a medium and records digital input signal C according to the upper limit of the medium temperature of the irradiation section, the light source is controlled to Therefore, the device is driven with a current larger and/or smaller than the normal recording current and/or non-recording current for an arbitrary fixed period.

[Effect]

In the present invention, since the rise and/or fall of the laser power is emphasized, for example, in FIG. 1 (1), the rise and fall of the laser power is emphasized, so that As for the maximum temperature, the delay in rise and fall is modified as shown in FIG. 1 (2). That is, regarding FIG. 1(1), the laser is turned on at a writing level at time r, but the power at this time is stronger than usual. Therefore, the slope of the rise in medium temperature is larger than usual. At time (3), the medium temperature is sufficiently high and exceeds the temperature T0 necessary for recording, so the light is turned on with the normal recording power. Writing ends at time ■, but in order to speed up the drop in medium temperature, lower the power than normal. This interval can be solved by making it sufficiently short (for example, about 50 nsec) that even if the power becomes almost zero, it will not affect the servo control of the recording device at all.

Through the above process, each point of the medium (in the case of an optical disk, magneto-optical disk, optical card, or magneto-optical card, due to rotation of the medium or movement of the disk) that moves relative to the irradiated laser spot As for the maximum temperature at each point on the track (that is, at each point on the track), the rising and falling slopes become larger as shown in FIG.

〔Example〕

Although the Vt period of the correction current can be set to an appropriate time depending on the rise and/or fall, in the following embodiments, the rise and fall are corrected for ease of explanation. Moreover, a case will be explained in which both the rising and falling correction times are exactly the length of one pit of the recording signal.

Of course, the circuit configuration is the same even when the correction time is not equal to I bits of the signal.

FIG. 6 is a block diagram of an embodiment of the semiconductor laser drive current generating circuit of the optical medium recording device of the present invention. The recording pulse current generating circuit 1 generates a normal recording pulse current as shown in FIG. 6(b) from a digital recording signal having a signal waveform as shown in FIG. 6(a). Pulse edge detection circuit 2.4
detect the rising edge and falling edge of record No. 13, respectively, and generate trigger signals as shown in FIGS. 6(c) and 6(e), respectively. The correction pulse current generating circuits 3 and 5 receive the trigger signal and generate correction pulse currents on the plus side and minus side, respectively, each having a length of one bit, as shown in FIG. 6(d) and <r>. Recording pulse current (Fig. 6 (
a) and the correction pulse current (FIGS. 6(d) and (f)) are added together to form a current waveform shown in FIG. 6(g), which drives the laser diode.

In FIG. 6, the waveform of the correction current is rectangular, but any waveform may be used as long as the waveform of the correction current emphasizes rising and falling edges, such as a sawtooth waveform.

FIG. 7 shows a second embodiment, in which the correction current is a sawtooth wave. The recording pulse current generating circuit 1 generates a normal recording pulse of 1 liter in the same way as the circuit 1 in FIG. 6.The differentiating circuit 6 differentiates the recording signal and generates a trigger signal as shown in FIG. The correction pulse current generating circuit 7 generates a sawtooth correction pulse current having a length of 1 bit as shown in FIG. 7(d) based on the trigger signal.

The recording pulse current (FIG. 7(b)) and the correction pulse current (FIG. 7(d)) are added together to form a current waveform shown in FIG. 7(e), which drives the laser diode.

FIG. 8 shows a third embodiment of the present invention. In this embodiment, the correction pulse current generating circuits 8 and 9 are the same as the circuit shown in FIG. 6, except that the duration of the correction current can be adjusted within one bit. Figure 8(a)-(
g) shows current waveforms at various points in the circuit of FIG.

FIG. 9 shows a fourth embodiment of the present invention. In this embodiment, the correction N'a by the sawtooth wave correction pulse current generation circuit 10 is
The duration of the circuit (FIG. 9(d)) is adjustable within a time period of less than one bit and is otherwise the same as the circuit of FIG. 7 for generating a sawtooth wave correction current.

Although four embodiments have been described above, the characteristics of each embodiment will be described below.

Compared to the first embodiment shown in FIG. 6, the third embodiment shown in FIG. 8 allows fine adjustment of the correction time, so that the correction time can be optimized.

The second embodiment shown in FIG. 7 has a greater effect of emphasizing the distortion than the first embodiment shown in FIG. The fourth embodiment shown in FIG. 9 allows optimization of the correction time compared to the second embodiment shown in FIG.

In addition, in the embodiment, correction by pulse (first and third embodiments)
was determined by the edge detection circuit 2.4, but of course the differential circuit 6
can also be used. In addition, although the correction using the tooth wave (in the second and fourth embodiments) was performed using the differentiating circuit 6, it is of course possible to use the edge detection circuit 2.4.

Furthermore, other edge detection means can also be used. Further, in the embodiment, a case is shown in which both the rising edge and the falling edge are corrected, but it goes without saying that either one of them may be corrected.

Furthermore, the correction period is not limited to 1 bit or less. However, in terms of circuit configuration, by setting it to 1 bit as in the embodiment, it becomes FJT jF-.

〔Effect of the invention〕

As described above, according to the present invention, in the maximum temperature profile of the recording layer, the temperature rise or fall at the rising and/or falling portions becomes sharper, and therefore the ambient temperature dependence of the optimum recording power and the recording frequency Dependency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the pulse waveform of laser power and the maximum temperature at each point of the recording layer according to an embodiment of the present invention, and FIG.
The figure is a waveform diagram of the conventional laser drive voltage Ql+i, Figure 3 is a diagram showing the relationship between the laser output waveform, the maximum temperature at each point of the recording layer, and the recording bit, and Figure 4 is a diagram showing the relationship between the laser output waveform and the maximum temperature at each point of the recording layer and recording bits. , a diagram showing that the maximum temperature moves in parallel and the recording bit length changes, FIG. 5 is a diagram showing the relationship between the laser output waveform and the maximum temperature of the recording layer when the recording peripheral wave number is not sharp, and FIG. FIG. 7, FIG. 8, and FIG. 9 are block diagrams explaining the embodiment and current waveforms of each part. [Explanation of symbols of main parts] 1−−−−−−−−−−−−・−−1−−−−−−−−
-～----Recording pulse current generation circuit 2.4------
−−−−・−・−・Pulse edge detection circuit 3.5,・
8.9-1---Correction pulse current generating circuit Applicant Nippon Kogaku Kogyo Co., Ltd. Agent Patent attorney Takashi Watanabe Male N1 Day Figure 5 Figure 6 Figure 7 Figure 3

Claims (7)

[Claims] (1) Optical media recording device that controls a light source with binary values of recording current and non-recording current according to a digital input signal, irradiates the medium with light, and records the digital input signal by increasing the temperature of the medium in the irradiation section. An optical medium recording device characterized in that the light source is driven with a current larger than a normal recording current for an arbitrary fixed period from the rise of an input signal. (2) Optical media recording device that controls a light source with binary values of recording current and non-recording current according to a digital input signal, irradiates the medium with light, and records the digital input signal by increasing the temperature of the medium in the irradiation section. An optical medium recording device characterized in that the light source is driven with a current smaller than a normal non-recording current for an arbitrary fixed period from the fall of an input signal. (3) Optical media recording device that controls a light source with binary values of recording current and non-recording current according to a digital input signal, irradiates the medium with light, and records the digital input signal by increasing the temperature of the medium in the irradiation section. The light source is driven with a current larger than the normal recording current for an arbitrary fixed period from the rising edge of the input signal, and is driven with a smaller current than the normal non-recording current for an arbitrary fixed period from the falling edge of the recording signal. An optical medium recording device characterized by: (4) The optical medium recording device according to claim 3, wherein the arbitrary fixed period is different at a rising time and a falling time. (5) The optical medium recording device according to claim 3, wherein the arbitrary fixed period is equal at a rising time and a falling time. (6) The optical medium recording device according to claim 5, wherein the arbitrary fixed period is one bit. (7) The optical medium recording device according to claim 4 or 5, wherein the arbitrary fixed period has a maximum length of 1 bit.