JP2674042B2 - Optical information recording method and apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for recording information on an optical information recording carrier. 2. Description of the Related Art A recording method called a perforation method or a modification method that forms a signal pit as a signal mark on an optical information recording carrier, and a phase change method that forms a signal bit that does not substantially change in shape as a signal mark. Alternatively, there is a magneto-optical method. The following description applies to both signal bits and signal bits, but for the sake of simplicity, only signal bits will be described. As the optical information recording method, there are a method based on the time length of the signal bit and a method based on the time length of the signal bit itself being constant. Here, the time length is the transit time when the signal bit or the signal bit on the rotating optical information record carrier is viewed from the stationary system. The former has the advantage that the recording density is higher than the latter, but has the drawback that information is easily broken. That is, the fluctuation of the laser light intensity at the time of signal recording, the fluctuation of the time longer than the temperature at which the signal bit is formed in the tracking and focusing conditions, and the fluctuation of the time length of the signal bit, This is because the time length changes. On the other hand, in the method of recording information with the time length between signal bits, the recorded information is not damaged even if the time length of the signal bit itself slightly changes. Therefore, conventionally, a method of recording information according to a time length between signal bits has been mainly used. FIG. 4 shows a conventional example. The horizontal axis is time. FIG. 4a is a clock signal having a minimum time length between signal bits,
It serves as a reference for reading and writing signals. FIG. 4b shows an information signal written on the optical information record carrier. Corresponding to this signal, laser light was irradiated with a constant intensity on the same track as shown in FIG. 4c. That is, the intensity of the laser beam was constant when the rotation of the optical information recording carrier was constant, and was stronger toward the outer periphery when the angular velocity was constant. DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Even in a method of recording information in a time length between signal bits, high density recording of information is a problem. In order to increase the density, it is necessary to shorten the time length of the signal bits themselves, and also the time length between the signal bits. In this case, when the laser light intensity is constant as shown in FIG. 4c, the reproduced signal has a pulse signal width or a signal interval clogged in the shape of the signal at a position where the signal interval is clogged as shown in FIG. 4d. Then, distortion such as sticking to the adjacent signal occurs.
This is affected by the accumulation of thermal energy by the laser light applied to the optical information record carrier before a certain signal bit is formed. That is, when the laser light intensity is constant, the shorter the time length between signal bits, the higher the temperature of the recording medium of the optical information record carrier becomes, which is higher than the optimum temperature for signal bit formation. In extreme cases, the recording medium will be destroyed. In view of the problems of the conventional optical information recording method described above, the present invention is an optical information recording that suppresses fluctuations in the time length of signal bits when performing information recording with the time length between signal bits. It is an object to provide a method and a device. Means for Solving the Problems In order to solve the above problems, the present invention provides a laser beam intensity at the time of forming the next signal mark at least as the time length with the signal mark formed immediately before becomes longer. The time length of the signal mark itself is kept constant by making the temperature rise of the recording medium of the optical information record carrier constant when the signal mark is formed. When forming a signal mark, the signal to be formed by adjusting the laser light intensity forming the signal mark according to the time length of the signal mark formed at least immediately before the signal mark. The influence of the preheating effect by the laser light irradiated before the mark is eliminated, and the time length of the signal mark can be kept constant. as a result,
Since there is no abnormality in the signal mark shape etc. and it is always stable,
Waveform distortion of the reproduced signal does not occur. Further, since the time length between signal marks can be shortened as compared with the related art, high density can be achieved. Practical Example FIG. 1 shows an embodiment of the optical information recording method of the present invention. The horizontal axis is time. FIG. 1A shows a clock signal, which is a constant frequency signal corresponding to the minimum time length between signal marks (which will be described below using signal bits but the same applies to signal pits). An information signal is generated in synchronization with this clock signal as shown in FIG. This pulse signal corresponds to the signal bit formed on the optical information recording medium. The present invention compares the interval of at least the immediately preceding pulse of this information signal, and the longer the interval, the stronger the laser light intensity at the time of forming the signal bit as shown in FIG. 1c. However, in FIG. 1, the intervals between the immediately preceding pulse and the immediately preceding two preceding pulses are compared.
As a result, the reproduced signal of the signal recorded on the optical information recording medium has a waveform without distortion as shown in FIG. The reason will be described below. FIG. 2 shows the temperature reached and the signal bit of the recording medium when two consecutive signal bits are formed when the optical information recording carrier is rotated at a constant speed and a laser beam is irradiated onto the recording medium at a constant intensity. FIG. The unit is arbitrary. As shown in FIG. 2, the reached temperature of the recording medium rapidly increases as the distance between the signal bits decreases. This is due to the preheating effect due to the accumulation of thermal energy of the previously irradiated laser light. FIG. 3 is a diagram showing the relationship between the irradiation laser beam intensity and the distance between signal bits when the temperature reached by the recording medium reaches a temperature suitable for signal bit formation. The unit is arbitrary. It can be seen from FIG. 3 that as the distance between the signal bits becomes longer, the irradiation laser light intensity for forming the signal bits may be increased. When the optical information recording method of the present invention is used, a reproduced signal waveform having no distortion can be obtained more stably than in the past. In addition, since the reproduced waveform is less distorted even if the distance between the signal bits is reduced, the recording density can be increased. Next, a specific optical information recording device will be described.
FIG. 5 is a schematic view showing the first embodiment of the optical information recording apparatus of the present invention. This is the case where the optical information recording carrier is rotating at a constant linear velocity. In FIG. 5, the signal source 1 is a portion for generating a recording information signal. That is, the signal source 1 converts the information into an information signal a having a constant pulse width and supplies it to the signal bit time length detection circuit 2. The inter-signal bit time length detection circuit 2 supplies an information signal b corresponding to the time length of a signal bit to be formed and at least the immediately preceding signal bit to the laser light intensity setting circuit 3 at the same time in synchronization with the original signal a. To do. The laser light intensity setting circuit 3 sets the laser light intensity from the signal b representing the time length between signal bits, synchronizes the signal c corresponding to the laser light intensity with the original signal a, and sends only the signal c to the laser drive circuit 4. Supply. The laser drive circuit 4 supplies a current to the semiconductor laser 5 according to the input signal c. The reaction laser 5 irradiates light with an intensity according to the supplied current. The laser light emitted from the semiconductor laser 5 is collimated by the collimator lens 6 and condensed by the condenser lens 7 to form a minute spot on the recording medium of the optical information recording carrier 8. The optical information recording medium 8 has a disk shape and is rotated by a spindle motor 9. Condenser lens 7
Controls the position of focusing so that a minute spot is always formed on the recording medium of the optical information recording medium 8.
In addition, although an optical system and a circuit system for tracking and reproduction are actually required, the description is omitted because it is not directly related to the present invention. With respect to the present invention, conventionally, a pulse signal by a current from the signal source 1 was directly supplied to the laser drive circuit 4. As a method of detecting the time length between signal bits,
There is a method of counting the number of pulses of the clock signal in the time length between signal bits by using a clock signal which is a constant frequency signal corresponding to the minimum time length. If the laser light intensity corresponding to this count number is set in advance, the laser light intensity setting circuit optimizes the laser light intensity for signal bit formation. As a result, since the signal bit formed on the recording medium is always constant, a stable reproduction signal can be obtained. Further, since the distance between the signal bits can be shortened as compared with the case where the signal bits are formed under the constant laser light intensity, it is possible to increase the recording density. FIG. 6 is a schematic view showing a second embodiment of the optical information recording apparatus of the present invention. This is the case where the optical information recording carrier is rotating at a constant angular velocity. FIG. 6 is different from FIG. 5 in that an information reading function from the optical information record carrier 8 is added. That is, the reflected light from the optical information recording medium 8 is redirected by the polarization beam splitter 10 and condensed by the condenser lens 11 to be guided to the detector 12. The optical signal that has entered the detector 12 enters the circumferential position detection circuit 13 where the circumferential position where the signal bit is written is detected on the optical information record carrier. For example, it is calculated from the address recorded in advance on the optical information recording carrier 8. The resulting signal d is supplied to the laser light intensity setting circuit 3. Laser light intensity setting circuit 3
Sets the basic laser beam intensity from the signal d, and further compares the time length of the signal bit to be formed with at least the immediately preceding signal bit from the signal b resulting from the inter-signal bit time length detection circuit 2. , The laser light intensity is corrected as it becomes longer, and the signal c synchronized with the original signal a is supplied to the laser drive path 4. The subsequent process is similar to that of the first embodiment. EFFECTS OF THE INVENTION The present invention increases the laser light intensity at the time of forming the next signal mark as the time length with the signal mark formed immediately before becomes longer. Therefore, when a certain signal mark is formed, The influence of the preheating effect by the laser beam applied for forming the signal mark before that is eliminated, and the shape of the signal mark can be always kept constant and stable. As a result, the reproduced signal has no distortion. Further, according to the present invention, the length between the signal marks can be made shorter than the time length between the signal marks as compared with the prior art, so that high density can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a signal and a laser light intensity change with time showing an optical information recording method of the present invention, and FIG. 2 is a constant rotation speed of an optical information recording carrier and irradiation. FIG. 3 is a diagram showing the relationship between the temperature reached by the recording medium and the distance between the signal bits when the laser light intensity is constant, and FIG. 3 shows the irradiation when the reached temperature of the recording medium is constant under the constant rotation speed of the optical information record carrier. FIG. 4 is a diagram showing the relationship between the laser light intensity and the distance between signal bits, FIG. 4 is an explanatory view showing the change over time of the signal and laser light intensity showing the conventional optical information recording method, and FIG. 5 is the optical information of the present invention. FIG. 6 is a schematic view showing a first embodiment of the recording apparatus, and FIG. 6 is a schematic view showing a second embodiment of the optical information recording apparatus of the present invention. 1 ... Signal source, 2 ... Signal bit time length detection circuit,
3 ... Laser light intensity setting circuit, 4 ... Laser drive circuit,
5 ... Semiconductor laser, 6 ... Collimator lens, 7, 11 ...
… Condenser lens, 8 …… Optical information record carrier, 9 …… Spindle motor, 10 …… Declination beam splitter, 12 …… Detector, 13 …… Circular position detection circuit.

Claims (1)

(57) [Claims] An optical information recording method of focusing laser light and irradiating the surface of a recording medium to form signal marks, and performing information recording by the time length between the signal marks, at least with the signal mark formed immediately before. An optical information recording method characterized in that the intensity of laser light when forming the next signal mark is increased as the time length becomes longer. 2. An optical information recording apparatus for rotating an optical information recording carrier at a constant linear velocity, focusing laser light and irradiating it on a recording medium surface to form signal marks, and recording information according to a time length between the signal marks. In addition, at least the inter-mark length detecting means for reading the information of the immediately preceding signal mark and detecting the time length between the signal marks to be recorded next from the information, and the detection result of this inter-mark length detecting means An optical information recording apparatus comprising a laser beam intensity control means for increasing the laser beam intensity at the time of forming the next signal mark at least as the time length of the signal mark formed immediately before becomes longer. 3. An optical information recording apparatus for rotating an optical information recording carrier at a constant angular velocity, focusing a laser beam and irradiating the laser beam on the surface of a recording medium to form signal marks, and recording information according to a time length between the signal marks. And an inter-mark length detecting means for reading at least the information of the immediately preceding signal mark and detecting the time length between the signal marks to be recorded next from the information, and a circumferential position or a degree of circumference for forming the signal mark. A circumferential position / circumferential velocity detecting means for detecting at least one of the above, and from the detection result of the inter-mark length detecting means, the signal mark formed at least immediately before on the same circumference is recorded next. As the time length with the signal mark becomes longer, the laser beam intensity at the time of forming the signal mark to be recorded next is increased, or the detection result of the circumferential position / peripheral velocity detection means is increased. As the time length between the signal mark formed immediately before and the signal mark to be recorded next becomes longer toward the outer periphery of the optical information recording carrier, the intensity of the laser beam when forming the signal mark to be recorded next becomes stronger. An optical information recording apparatus comprising a laser light intensity control means for setting at least one of the following. 4. 4. The optical information recording device according to claim 3, wherein the circumferential position / peripheral velocity detecting means is a circuit for reading address information recorded in advance on the optical information recording carrier.