JPH0354739A - Recording method for optical information recording member - Google Patents

Abstract

PURPOSE:To always form a recording mark in a prescribed shape by changing power between a recording pulse and a preceding pulse corresponding to an interval between the recording pulse, which is generated for forming the recording mark on an optical information recording member, and the pulse preceding to the recording pulse based on an information signal. CONSTITUTION:The power of a semiconductor laser is changed in a waveform 5b to a code signal 3s corresponding to a data signal. In accordance with time intervals D1-D4 among recording pulses W1-W4, an erasing power level Pe among the intervals is changed by steps like Pe1-Pe4. Namely, when an interval D between the recording pulses, the erasing power is set high and when the interval D between the recording pulses get smaller, the erasing power is gradually set to low values. Thus, by changing the erasing power level Pe, a demodulated code signal 15b can be equipped with the same cycle as the initial code signal 3s, namely, a signal without time error can be realized. Thus, recording can be achieved with small distortion in the shape of the recording mark.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording member for optically recording information.
The present invention relates to a recording method and a recording device for performing good recording.

BACKGROUND ART Techniques for recording and reproducing information using laser light are already well known and have been applied to document files and data files, and methods with rewriting functions are currently being actively developed.

One of these methods is a so-called phase-change flower-shaped optical disk that utilizes reversible state changes between amorphous crystals or between crystals. The recording thin film used for this purpose has the characteristic that it takes an amorphous state or a crystalline state depending on heating and cooling conditions using laser light, and that the two states change reversibly. The amorphous state and the crystalline state have different complex refractive indices consisting of a refractive index n and an extinction coefficient k, and the resulting difference in transmittance or reflectance is used to record signals. In order to realize these, recording power Pw and erasing power P
There is a method of irradiating a recording medium with a laser beam modulated between two power levels of e (Pw>Pe) (for example, Japanese Patent Laid-Open No. 145530/1982). That is, when a recording material is irradiated with a laser beam whose intensity is modulated according to a signal, even if the irradiated part was in an amorphous or crystalline state before, the part irradiated with the recording power Pw becomes an amorphous state and is erased. The part irradiated with power Pe becomes crystalline. As a result, a recording mask (amorphous state) corresponding to the information signal is formed on the recording medium, making it possible to overwrite with one spot.

There is a system shown in FIG. 2 as an apparatus for recording signals on an optical information recording member (hereinafter referred to as an optical disk). The whole consists of an optical disc 1, an optical system A for condensing laser light onto the optical disc 1, an information recording section B for modulating the laser light, and an information recording section B for reproducing information from the optical disc and controlling a light spot. It is controlled by the playback control section C for the purpose. A data signal 2S to be recorded on the optical disk is guided to the information recording section B, converted into a constant code signal by the encoder 3, and modulated by the semiconductor laser 5 via the drive circuit 4.

In optical system A, light from a semiconductor laser 5, which is a light source for recording and reproducing, is converted into parallel light by a collimator lens 6, transmitted through a polarizing beam splitter 7 and a quarter-wave plate 8, and then collimated by an objective lens 9. The light is focused on the recording thin film 10 on the optical disk l to a spot diameter of approximately 1 μm, which is the wavelength limit. Further, the reflected light from the recording thin film 10 passes through the objective lens 9 and the quarter-wave plate 8 again, is reflected by the deflection beam splitter 7, and is received by the photodetector 11. The signal photoelectrically converted by the photodetector is amplified by the preamplifier l2 of the reproduction control section C.

The playback control section C includes a focus/tracking control section 13
The low frequency component of the signal from the pre-amplifier 12 is used to convert it into a control signal to drive the voice coil 14 supporting the objective lens 9, thereby performing focusing and tracking of the spot on the optical disc. On the other hand, the demodulation circuit 15 reproduces the optical disc by reconstructing the code signal from the mark formed on the optical disc A into data using the high frequency component of the signal from the hybrid amplifier 12.

Problems to be Solved by the Invention Recording is performed on an optical disk by irradiation with a laser beam whose intensity is modulated in accordance with a code signal.

However, as the recording density increases, the effects of heat conduction become more noticeable, and various distortions occur in the recorded marks. This phenomenon will be explained using FIG. 2 and the recording/reproducing signal zero timing chart of FIG. The code signal 3s output from the encoder 3 in response to the data signal 2S passes through a semiconductor laser drive circuit and becomes a current that is modulated between two levels in response to the code signal, resulting in a current value corresponding to each current value. A power output 5S is generated from the semiconductor laser.

Recording power Pw and erasing power Pe are set according to the code signal.
The recording thin film 10 is irradiated with an optical output 5S modulated between 0 and 0 from the semiconductor laser 5, and recording is performed. Recording thin film 10
The recording mark 16 formed on the top is distorted in shape due to the influence of heat conduction of the irradiation part, etc., as shown in 10a. In particular, there was a tendency for the shape of the next recorded mark to be significantly different depending on whether the interval between the previous recorded mark and the recorded mark was short or long. Therefore, when the signal is reproduced, distortion as shown in 12s occurs, and the demodulated code signal 15 in the demodulation process is
As shown in a, a time error 17 occurs between the original code signal 3s and the original code signal 3s. When this value exceeds a certain level, the original signal cannot be reproduced, resulting in a reading error.

In order to cope with this, methods have been proposed such as changing the recording power depending on the mark interval or changing the recording start timing, but in both cases, not only the density of the marks but also the length of the previous and subsequent marks are taken into account. An accurate mark shape could not be obtained unless it was modulated by inserting it into the image.

That is, in order to realize these, correction taking into account the combination of each recording pattern is essential, and complicated circuit processing is required.

In view of the above, it is an object of the present invention to provide a recording method and apparatus that can always form recording marks of a predetermined shape by improving the laser beam irradiation conditions.

Means for Solving the Problems When a signal is recorded using a laser beam or the like on an optical information recording member having a recording material having two optically distinguishable states, the optical information recording is performed in accordance with the information signal. The power between the previous recording pulse and the immediately preceding pulse is changed depending on the interval between a recording pulse for forming a recording mark on the member and the pulse immediately before the recording pulse.

By changing the power between the previous recording pulse and the immediately preceding pulse according to the interval between the action recording pulse and the immediately preceding pulse,
Temperature changes at the starting and ending ends of the recording mark can be made constant. As a result, it is possible to suppress distortion of the shape of the mark formed on the recording medium, and it is possible to reduce reading errors during demodulation.

EXAMPLE Hereinafter, a recording method for an optical information recording member according to an example of the present invention will be described with reference to the drawings.

Note that the optical system and reproducing system have the same configuration as shown in FIG. 2, but the configuration of the information recording section is changed.

First, the concept of the recording method of the present invention will be explained using FIG. Code signal 3S corresponding to data signal 2S
On the other hand, the power of the semiconductor laser is modulated with a waveform as shown in 5b. Time interval D1 between recording pulses W1 to W4
~D4, the erase power level Pe during that time is Pe
1 to Pe4. That is, when the interval D between recording pulses is large, the erasing power is set high, and as the interval D between recording pulses becomes smaller, the erasing power is set to a lower value. The shape of the recording mark formed on the recording medium by the optical output 5b is shown in 10b. In this way, by changing the erasing power level Pe, the positions of the start and end portions of the recording marks can be kept constant, and the demodulated code signal 1 demodulated from the reproduced signal 12b
5b has the same period as the initial code signal 3S, that is, a signal without time error can be reproduced. This is because when the distance between recording marks is small, the temperature increase due to the residual heat effect that occurs between the recording marks can be corrected by lowering the erasing power level.

FIG. 4 is a block diagram of the information recording section, and FIG. 5 is a timing chart of signals. The data signal 2S is sent to the encoder 1
8 into a code signal 20s. Here, we will introduce the 2-7R conversion code commonly used for optical discs.
Encoder 1 that modulates the LL code using a pulse edge recording method
8 was used. The encoder 18 generates a gate signal 19s indicating the operating state of encoding, a code signal 20s, and timing signals 21s to 26 synchronized with each code signal pattern at the same time.
It provides the function to generate s. That is, the timing signals 21s to 26s have inversion periods of 1.5T, 2T, 2.5T, 3T, 3.5T, and 4T of the 2-7 RLL code, respectively.
It operates only during the corresponding period. Each timing signal and the code signal 27s inverted by the inverter 27 are ANDed.
It is input to circuits 28-3l.

At a current value above a certain level, the semiconductor laser 5
Shows the characteristic that the output power increases in proportion to the increase in current value. In FIG. 4, six current sources 32 to 37 are arranged to drive the semiconductor laser, current source 32 is used for reproducing power, current source 33 is used for recording power, and current sources 34 to 3 are used for recording power.
7 generates a current corresponding to erase power. Further, currents switched by switching devices 38 to 43 are applied to the output ends of each of the current sources 32 to 37, respectively. At the output end, each current is combined and applied to the semiconductor laser 5.

In the reproduction current source 34, a switch 38 is operated by a gate signal 19s indicating the operating state of the encoder. That is, if the data signal 2S is not input to the encoder 18, the current source 3
Only the current of 4 is output from the output terminal 44s.

When the data signal 2s is manually input to the encoder l8, when the code output 19s is ゜゜H'゛, the switch 39 operates, and a current corresponding to the recording power is generated from the current `tA33 at the output terminal.

Conversely, when the code output 19s is "l L n", the timing signals 21s to 2 for each code signal pattern of the encoder are
Switches 40 to 43 corresponding to 6s operate. As a result, the semiconductor laser 5 generates an optical output 44s having erasing power according to the length of each code signal.

Note that the relationship between the code signal and the erasing power is such that the power is the lowest when the code signal inversion interval is the shortest inversion cycle, and the power is gradually increased as the signal inversion interval becomes longer. That is, the erasing power is the lowest when the inversion interval is 1.5T, gradually increases to 2, 2.5T, 3T, and 3.5T, and the highest is the erasing power when the inversion interval is 4T. By setting the erasing power according to each signal inversion interval (that is, the interval between recording pulses) as described above, the temperature reached and the cooling rate of each recording mark can be kept within a certain range. As a result, distortion of recorded marks can be reduced. In order to set the erase power in six levels in this manner, six current sources are required.

However, the distortion of the recorded marks is large when the interval between the recorded marks is short, as shown at 102 in FIG. 3, but the difference becomes small when the distance exceeds a certain value. Therefore, in this example, the fourth
As shown in the figure, individual values were set for 1.5T, 2T, and 2.5T, but the power values were set for 3T to 4T. In this way, the laser drive circuit can be simplified by reducing the number of erasing power levels depending on factors of recording mark deformation, such as the recording mark density, the sensitivity of the recording medium, and the relative speed between the recording medium and the laser beam.

In this embodiment, the case of pulse edge recording of the 2-7RLL code signal has been described, but other methods (for example, MFM
, EFM method) can also be handled by similarly setting the erasing power according to the type of code pattern. Furthermore, pulse position recording can be handled in the same way by setting the erasing power according to the pulse interval.

On the other hand, in a disk-based recording medium such as an optical disk, recording and reproduction are performed while keeping the rotational speed of the disk constant. Therefore, even if the same code signal is recorded, the relative speed is different between the inner and outer circumferences of the disk, so the interval between recording marks formed on the disk changes. To cope with this change, a sensor is installed in conjunction with the optical system to detect the recording position on the disc, and the recording position is constantly monitored. As another method, the recording position can be calculated from an address signal formed on the guide track of the optical disc. For each of these recording positions, the relationship between the code signal pattern and the erasing power is measured in advance, and based on the results, the values of the current sources 34 to 37 for each erasing power are controlled in accordance with the recording position signal. do.

With the above-described structure, it is possible to form marks with accurate shapes on the optical recording medium, and it is possible to achieve recording without causing errors during reproduction. In this example, a rewritable recording medium using phase change was explained. However, when this method is applied to a write-only medium (for example, perforated recording or phase change recording), the erasing power is It functions as a preheating light, and similarly produces the effect of recording marks.

Furthermore, it also has the effect of improving the symmetry of recorded marks in magneto-optical recording that combines light and magnetism. Among them, magneto-optical disks that are stackable with multiple magnetic layers (
JP-A No. 62-175948), the power modulation of the recording light is similar to that in phase change recording, and is particularly effective.

Effects of the Invention As described above, according to the light modulation method according to the present invention, recording with less distortion in the shape of recording marks can be achieved.

[Brief explanation of drawings]

Claims (4)

[Claims] (1) A method for recording a signal on an optical information recording member having two or more optically distinguishable states, the method comprising forming a recording mark on the optical information recording member in accordance with the information signal. A method for recording an optical information recording member, characterized in that the power between the recording pulse and the immediately preceding recording pulse is changed according to the time interval between the recording pulse and the immediately preceding recording pulse. (2) The power between the previous recording pulse and the recording pulse is
2. The method of recording an optical information recording member according to claim 1, wherein the recording pulse is set to be highest when the interval between the immediately preceding recording pulse and the recording pulse is long, and to be lowest when the interval is short. (3) A device for recording a signal on an optical information recording member having two or more optically distinguishable states, the device recording a signal on the optical information recording member using a semiconductor laser in accordance with the information signal. A recording device for an optical information recording member, comprising a current source that generates a peak power of a recording pulse to form a mark, and a plurality of current sources that generate power immediately before or after the recording pulse. . (4) Claim (3) characterized in that the plurality of current sources that generate power immediately before or after the recording pulse are switched to timing signals for each code pattern generated from an encoder that encodes the information signal. ) A recording device for an optical information recording member according to the above.