JPH0449526A - Optical information recorder - Google Patents

Abstract

PURPOSE:To accurately form a pit on a recording medium by providing a section of making power of a laser beam from a laser beam generating means to the recording medium smaller than write power and larger than bias power just prior to pit formation. CONSTITUTION:At the time of write, a blank length just prior to a pit to be formed is detected out of a write data by a blank length detecting circuit 14, and each section to be irradiated by the laser beam with bias power Pb, 2nd bias power Pb' and the write power Pw respectively is calculated by a pulse interval discriminating circuit 15 is accordance with the blank length detected by the circuit 14. A ROM 16 is registered previously with data corresponding to each power of the laser beam, and a data from the ROM 16 is selected by a selector circuit 17 by a time length according to each section calculated by the discriminating circuit 15, and is outputted to a D/A converter circuit 18. The data from the selector circuit 17 is D/A-converted by the converter circuit 18, and an output voltage of the converter circuit 18 is converted into a current by a voltage/current (V/I) converter circuit 19 to conduct a semiconductor laser 20 as to be a forward current I, so that the recording medium 11 is irradiated with the laser beam by the laser 20 via an optical head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording device for recording information on a recording medium such as an optical disk or a magneto-optical disk.

[Conventional technology]

Conventionally, in an optical information recording device that records information on a recording medium such as an optical disk, a laser beam from a semiconductor laser or the like is intensity-modulated in a pickup according to the recording data, and an optical lens forms a minute spot on the moving recording medium. The laser beam is focused upward, and the thermal energy of this laser beam locally alters the laser beam irradiated portion of the recording medium to form recording marks (pits), thereby recording data. In this case, as shown in FIG. 4, the recording medium is irradiated with a laser beam at a writing power Pw for a time corresponding to the length of the pit PT to be formed, and at other times, the laser beam is irradiated with a reading power Pr or a writing power Pw. The blank BK between each pit PT is irradiated with a predetermined bias power Pb1 that can guarantee the rise time to the power Pw according to specifications. The recording medium hardly generates heat even if it is irradiated with a laser beam of bias power Pb1.

In addition, in optical information recording devices, the linear velocity is different between the inner and outer circumferential sides of a recording medium such as an optical disk that rotates at a constant number of rotations, and recording is performed under the same conditions (constant writing power Pw, bias power Pb). When data is recorded on the inner circumferential side and the outer circumferential side of the medium, the conditions for forming pits are different due to the difference in the amount of heat caused by laser beam irradiation. Therefore, in order to compensate for this, the writing power PV and bias power pb□ are increased in areas where the linear velocity on the recording medium is high, and the writing power Pv and bias power Pb are increased in areas where the linear velocity on the recording medium is slow.
An optical information recording device designed to lower b1 was published in Japanese Patent Application Publication No. 5
It is described in Japanese Patent No. 6-87239. This optical information recording device basically irradiates the recording medium with a laser beam at a writing power Pw for a time corresponding to the length of the pit to be formed (when considering a certain linear velocity section). However, at other times, the device irradiates the recording medium with a laser beam using bias power Pb.

FIG. 5 shows an example of the output characteristics of a semiconductor laser.

This is the forward current flowing through the semiconductor laser and the emission power P
When the forward current (2) exceeds the threshold (2), it enters the laser emission region and a light emission power approximately proportional to the forward current is obtained.

Normally, if the semiconductor laser is made to emit light with the power in the light emitting region from a state where the forward current I is below the threshold value,
There are problems such as the rise time being extremely slow, so
The write power Pw, the bias power Pb, and the read power Pr are set to be higher than the threshold IL. In addition, the writing power Pw is set to an optimum value, taking into account the characteristics of the recording medium, the optical efficiency of the pickup, the power consumption, etc., at a power Pm or more that allows the laser beam irradiation part of the recording medium to reach the amount of heat that can form pits. The bias power pb and the read power Pr are set to optimal values in consideration of the characteristics of the recording medium, the optical efficiency of the pickup, the power consumption, etc., with a threshold value of 1 or more and the power P++ or less. In particular, bias power Pb1
is set close to the lower limit value (2) at which the laser beam irradiated portion of the recording medium does not heat up, from the viewpoint of minimizing power consumption without causing any problems with the rise of the write power Pw.

[Problems to be Solved by the Invention] In the above-mentioned optical information recording device, the length of pits on the recording medium and the length of blanks between pits are 1' or 0.
' can take various values depending on the number of consecutive times, but when the blank length changes, the relationship between the position at which laser light irradiation is started to form each pit and the starting end of each pit changes. That is, as the blank becomes longer, the influence of the heat generated when forming the previous pit of the blank on the formation of the next pit becomes smaller, and the distance from the laser beam irradiation start position to the starting end of the pit becomes longer. However, since the laser beam is irradiated onto the recording medium at a writing power Pv for a time corresponding to the length of the pit to be formed, the longer the blank length immediately before the pit to be formed, the more heat the laser beam irradiation part will write. The amount of heat that can form a pit is reached with a delay from the start of laser beam irradiation, and the starting end of the pit shifts backward. FIG. 4 shows an example. Each pit P to be formed
The length of T is the same, and the length of each blank BK is T□.

T2. When T is T1<T2<T, the laser beam is irradiated with the writing power Pw from the beginning to the end of the pit PT to be formed, and the laser beam is irradiated with the bias power Pb to other parts. , depending on the length of the blank BK immediately before the starting end of the pit PT that is actually formed, Ta2. Ta2. Tα.

It becomes shorter by (Ta2 x Ta2<Tα,).

In addition, if the laser beam is set to a power that constantly generates heat above the writing power Pm, for example, a read power, the laser beam irradiation part will maintain the amount of heat that can form a pit for a certain period of time even after the end of the pit to be formed. The end of the formed pit will shift backward.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information recording device that can improve the above drawbacks and accurately form pits on a recording medium.

[Means to solve the problem]

In order to achieve the above object, the present invention changes a laser beam irradiated from a laser beam generating means to a recording medium from a predetermined bias power to a writing power corresponding to a recording pulse, and uses the thermal energy of the laser beam of this writing power to In an optical information recording device that forms pits by locally changing the characteristics of a recording medium, the power of the laser beam from the laser beam generating means to the recording medium is set to be lower than the writing power immediately before forming the pits. Providing a section where the power is larger than the bias power, and making the section longer when the blank length immediately before the pit to be formed is long,
When the blank length immediately before the pit to be formed is short, a laser beam control means is provided to shorten the section.

[For production]

The laser light control means sets a section in which the power of the laser light from the laser light generation means to the recording medium is set to a power smaller than the writing power and larger than the bias power immediately before the formation of the pit, so as to create a blank immediately before the pit to be formed. When the blank length is long, the section is lengthened, and when the blank length immediately before the pit to be formed is short, the section is shortened.

〔Example〕

FIG. 1 shows the periphery of an optical head according to an embodiment of the present invention.

This embodiment is an example of an optical information recording device that records information on a recording medium consisting of an optical disk or a magneto-optical disk, and the recording medium 11 is rotated at a predetermined speed by a motor. During writing, the laser generation/control circuit 13 generates a laser beam and modulates its intensity according to the write data, as will be described later, and the optical head 12 focuses the recording medium 11.

While tracking is performed, a laser beam from the laser generation/control circuit 13 is irradiated as a minute spot to form pits in accordance with the written data.

During reproduction, the laser generation/control circuit 13 generates a laser beam with reproduction power, and the optical head 12 focuses and tracks the recording medium 11 while irradiating the laser beam from the laser generation/control circuit 13 as a minute spot. Then, the reflected light is received by a light receiving section and read data is output.

The laser generation/control circuit 13 generates and modulates the intensity of laser light as shown in FIG. In other words, laser generation
The control circuit 13 sets the power of the laser light to the writing power Pw when irradiating the beam to be formed on the recording medium 11, and controls the area (T□-Ta1) after the end of the pit PT to be formed on the recording medium 11, (T2-Ta2)
, ("I"3 - T p3), the power of the laser beam is set to bias power Pb, and immediately before the pit PT to be formed, an interval Tβ1, corresponding to the length of the blank BK immediately before this pit PT, is set. The power of the laser beam is set to the second bias power Pb' by Tβz+Tβ.

Here, the write power Pw is set to the optimum value above the power Pm, taking into consideration the characteristics of the recording medium, optical efficiency of the pickup, power consumption, etc., and the bias power pb and the read power Pr are above the threshold IL and below Pm. characteristics of the recording medium, optical efficiency of the pickup.

The bias power pb is set to an optimal value in consideration of power consumption, etc., and the bias power pb is set close to the threshold value. The second bias power Pb' is set to pb<pb''<Pa so that the laser beam imparts heat to the recording medium 11, but does not reach the amount of heat that allows the laser beam irradiation section to form pits. In the embodiment, the moving speed of the laser beam with respect to the recording medium 11,
The length of the blank immediately before the pit that should be formed, taking into account the influence of the heat generated by the laser beam between the pits on the next pit formation, which is determined by the heat conduction of the medium 1, the implantation power Pv, the bias power Pb, etc. The optimum second bias power pb' and sections Tβ1, Tβ2, and Tβ3 are determined depending on the situation, and pits are accurately formed from the start end to the end as shown in FIG. Note that the bias power Pb' of 2 may be the same as the readout power Pr in order to simplify the circuit, and by setting Tβ, , Ta2, and Tβ, optimally, the pits can be formed accurately from the start to the end. can do.

FIG. 2 shows a specific configuration of the laser generation/control circuit 13. As shown in FIG.

During writing, the blank length detection circuit 14 detects the length of the blank immediately before the pit to be formed from the write data, and the pulse interval discrimination circuit 15 detects the length of the blank immediately before the pit to be formed.
Each section in which laser light is irradiated with bias power Pb, second bias power pb', and writing power Pw is calculated according to the length of the blank detected by.

Data corresponding to each power of the laser beam is registered in advance in the read-only memory (ROM) 16, and the select circuit 17 inputs the data from the ROM 16 to the time length corresponding to each section calculated by the pulse interval discrimination circuit 15. is selected and output to the D/A conversion circuit 18. A digital/analog (D/A) conversion circuit 18 converts the data from the select circuit 17 into D/A, and converts the data from the voltage/current (V/I) conversion circuit 1
9 converts the output voltage of the D/A conversion circuit 18 into a current and sends it to the semiconductor laser 20 as a forward current, so that the semiconductor laser 20 emits a laser beam with the power shown in FIG. 3 mentioned above to the optical head. 12 onto the recording medium 11. For example, data corresponding to bias power Pb, second bias power pb', and write power Pw for each blank length is stored in the ROM 16 at power 1.
Power 2. It is registered as power 3, and the select circuit 17 selects power 1 from the ROM 16 for a period corresponding to the length of the blank immediately before the pit to be formed during the section in which the semiconductor laser 20 is made to emit light with bias power pb. The semiconductor laser 20 is made to emit light with a bias power pb, and the power 2 from the ROM 16 is selected for a period of time in which the semiconductor laser 20 is made to emit light with a second bias power Pb' for a period corresponding to the length of the blank immediately before the pit to be formed. Then, the semiconductor laser 2o is made to emit light with the second bias power Pb', and in the section where the semiconductor laser 2o is made to emit light with the writing power Pw, the power 3 of the ROM 16 is applied for a time corresponding to the length of the blank immediately before the pit to be formed. is selected and the semiconductor laser 2o is made to emit light with the writing power Pw.

Also, at the time of reproduction, data corresponding to the reproduction power Pr is registered in the ROM 16 in advance as power 4, and the select circuit 17 selects power 4 from the ROM 16 to
By outputting to the conversion circuit 18, the semiconductor laser 20 is made to emit light with the reproduction power Pr.

〔Effect of the invention〕

As described above, according to the present invention, the laser beam irradiated from the laser beam generating means to the recording medium is changed from a predetermined bias power to a writing power in accordance with a recording pulse, and the thermal energy of the laser beam of this writing power is used to record the information. In an optical information recording device in which pits are formed by locally changing the characteristics of a medium, the power of the laser beam from the laser beam generating means to the recording medium is adjusted to be lower than the writing power and the bias is applied immediately before the formation of the pits. Laser light control means that provides a section in which the power is greater than the power, and lengthens the section when the blank length immediately before the pit to be formed is long, and shortens the section when the blank length immediately before the pit to be formed is short. Since the length of the blank between each pit on the recording medium is different, the amount of heat in the laser beam irradiation part reaches the amount of heat that can form a pit with a delay from the start of laser beam irradiation of the writing power, and the starting end of the pit is backward. The amount of heat in the laser beam irradiation part can be instantly raised to the temperature at which pits can be formed after the start of laser beam irradiation with writing power, and pits can be accurately formed on the recording medium. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the peripheral area of an optical head according to an embodiment of the present invention, FIG. 2 is a block diagram showing a laser generation/control circuit according to the same embodiment, and FIG. 3 is a diagram showing pits to be formed in the same embodiment. , a diagram showing the relationship between the power of the laser beam and the pits formed, FIG. 4 is a diagram showing the relationship between the pits to be formed in a conventional optical information recording device, and the pits formed by the power of the laser beam, and FIG. 5 is a diagram showing the relationship between the pits formed by the power of the laser beam. FIG. 2 is a characteristic curve diagram showing an example of output characteristics of a laser. 11... Recording medium, 12... Optical head, 13...
Laser generation/control circuit.

Claims (1)

[Claims] A laser beam irradiated from a laser beam generating means to a recording medium is changed from a predetermined bias power to a writing power in response to a recording pulse, and the characteristics of the recording medium are locally changed by the thermal energy of the laser beam of this writing power. In an optical information recording device in which pits are formed by using a laser beam, a section is provided in which the power of the laser beam from the laser beam generating means to the recording medium is set to a power smaller than the writing power and larger than the bias power immediately before forming the pits. The optical system is characterized by comprising a laser beam control means that lengthens the section when the length of the blank immediately before the pit to be formed is long, and shortens the section when the length of the blank immediately before the pit to be formed is short. Expression information recording device.