JPH06215377A - Optical disk recording device - Google Patents

Abstract

PURPOSE:To obtain an optical disk recording device without generating a teardrop-like bit shape by using a light beam having comparatively low output (small light quantity). CONSTITUTION:A supplied binary continuous signal S1 is converted to a pulse signal S4 divided into the period (unit) of a clock signal CK by means of a waveform forming circuit 1 and supplied to an optical pickup 9. Thus, the waveform of the optical output of the laser light L1 as a writing light outputted from the optical pickup 9 becomes a waveform corresponding to the pulse signal S4. Consequently, by driving the optical pickup 9 based on the pulse signal S4, the generation of the teardrop-like bit shape is prevented even when the laser light of comparatively low output is used without using the pulse of a high output, narrow width having the duty ratio less than 50%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording apparatus suitable for application to, for example, a write-once optical disk recording / reproducing apparatus.

[0002]

2. Description of the Related Art For example, a write-once type optical disc is known in which an arbitrary information signal can be written on a disc coated with an organic recording material by using a light beam such as a laser beam.

When an information signal is written on such a write-once type optical disc, the source bit is based on, for example, 2-7 modulated (2 to 7 consecutive "0" values) channel bits. Written.

FIG. 3A shows a portion of an example of such a channel bit. The bit string of the channel bits is “0011” corresponding to each clock unit (cycle) of the channel clock (see FIG. 3B) which is a clock signal.
It is configured as "1000001111OO".

Two techniques are known for writing this channel bit as an information signal on a write-once optical disc.

One of the techniques is a thin pulse with a duty of 50% or less with respect to the clock period (see FIG. 3C).
This is a technique for recording with a relatively high output light beam corresponding to (hereinafter, referred to as narrow pulse technique).

FIG. 3D shows the shape of pits formed on the write-once optical disc by the technique using the narrow pulse.

Another technique is a technique for recording with a relatively low output light beam corresponding to a binary continuous signal (see FIG. 3E) corresponding to a channel bit (hereinafter, referred to as a continuous signal technique).

FIG. 3F shows the shape of pits formed on the write-once optical disc by the technique based on this continuous signal.

[0010]

However, as can be seen from FIG. 3D, the pits formed by using the above-mentioned narrow pulse technique can form uniform pits in which heat accumulation on the write-once optical disc is avoided. Although it has an advantage, since it is necessary to generate a high-power light beam, for example, the rated value of the laser diode as the light beam generating means may be exceeded. Moreover, such a light beam generating means is expensive.

On the other hand, in the technique using continuous signals,
Since the light beam generating means for generating a light beam having a relatively low output may be used, it is easy to select the light beam generating means. However, as can be seen from FIG. 3F, the formed pit has a teardrop shape, There is a problem that the so-called teardrop shape tends to occur and crosstalk with adjacent tracks is likely to occur. In addition, in order to avoid the occurrence of this teardrop shape, slimming processing for continuous signals (a type of write compensation processing) that considers the thermal time constant
However, there is a problem that in many cases the improvement is not so great despite the fact that the circuit configuration becomes considerably complicated. In addition, in the technique using the continuous signal, the light beam generation time by the light beam generation means becomes relatively long, so that there is a problem that the replacement life of the light beam generation means, for example, a laser diode is shortened as a result.

The present invention has been made in consideration of the above problems, and provides an optical disk recording apparatus in which a tear drop type pit shape is not generated by using a light beam of relatively low output (low light amount). With the goal.

[0013]

The present invention is described in, for example, FIG.
As shown in FIG. 2, a light beam generating means 9 for generating a light beam for writing a pit of a predetermined length on the optical disc 11 as a continuous signal, a binary continuous signal S1 and a clock signal CK are supplied. The signal processing means 1 for driving the beam generating means 9 is provided, and the signal processing means 1 divides the binary continuous signal S1 into clock signal CK units to obtain a pulse signal S4.
And is supplied to the light beam generating means 9.

[0014]

According to the present invention, the supplied binary continuous signal S1
Is converted into a pulse signal S4 divided into clock signals CK and supplied to the light beam generating means 9.
Therefore, the light output waveform of the light beam L1 output from the light beam generator 9 has a waveform corresponding to the pulse signal S4. Therefore, it is possible to prevent the teardrop-shaped pit shape from occurring even if a light beam having a relatively low output (light amount) is used. In addition, since the light beam generation time is shortened, the replacement life of the light beam generation means 9 is extended.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical disk recording apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of the main part of the optical disk recording apparatus according to this embodiment. The optical disk recording apparatus according to the example of FIG. 1 has a waveform shaping circuit 1 as signal processing means.

A binary continuous signal S1 is supplied to one input of an AND circuit 2 constituting the waveform shaping circuit 1 through an input terminal 3. In the binary continuous signal S1, a source bit supplied through a host computer (not shown) is
It is a so-called run length limited signal that is converted into channel bits by 2-7 modulation (two or more consecutive "0" values are contained and 7 or less).

The other input of the AND circuit 2 is supplied with the signal S3 from the output of the OR circuit 4. A clock signal CK which is a channel clock is directly supplied to one input of the OR circuit 4 through an input terminal 5. The cycle T of the clock signal CK is T = 230 ns in this embodiment. The duty ratio R of the clock signal CK, that is, the ratio of the cycle T of the clock signal CK to its high level period is 50%. The other input of the OR circuit 4 is supplied with the signal S2 obtained by delaying the clock signal CK through the delay circuit 6 by the delay time τ. The delay time τ is τ = 65 ns in this embodiment.

The delay time τ of the delay circuit 6 is determined according to the output signal S7 from the system controller 7.

The output signal S4 of the AND circuit 2, that is,
An output signal S4 of the waveform shaping circuit 1 is converted from a voltage signal S4 to a current signal S5 through a laser diode driver 8 and supplied to a laser diode (not shown) as a light beam generating means which constitutes an optical pickup 9. . Therefore, the waveforms of the voltage signal S4 and the current signal S5 are similar waveforms.

A laser beam L1 which is a writing light beam output from the optical pickup 9 is supplied to an optical disk 11 which is rotated by a spindle motor 10 in a CLV system or a CAV system. The optical output of the writing laser beam L1 is less than about 30 mW.

Here, the optical disk 11 is, for example, a write-once optical disk in which an arbitrary information signal can be written by using a light beam such as a laser beam on a disk coated with an organic recording material. . Other optical disks may be used.

Therefore, the laser beam L1 writes a pit string having a predetermined length based on the signal S5 (signal S4) on the optical disk 11.

On the other hand, when the optical disc 11 is irradiated with a laser beam which is a light beam for reading, the laser beam L2 which is a reflected beam from the optical disc 11 is a well-known four-division means which is a light receiving means constituting the optical pickup 9. A reproduction signal S6 which is an RF signal detected by the diode and based on the detected light
Are supplied to the system controller 7. The system controller 7 includes an input / output interface, an A / D conversion circuit, a CPU, a ROM, a RAM, and the like. The signal S7 for changing the delay time τ of the delay circuit 6 based on the reproduction signal S6 is sent to the delay circuit 6. Supply.

It is to be noted that the servo intensity of the well-known focus tracking slide based on the laser light L2 which is the reflected light from the optical disc 11 and the laser light L1 which is the incident light, which is the so-called front monitor output light intensity A.
PC control and the like are performed under the control of a CPU (not shown).

Next, the operation of the above embodiment will be described with reference to the waveform chart shown in FIG.

The clock signal CK having the period T (see FIG. 2A) supplied through the input terminal 5 is converted into the signal S2 delayed by the delay time τ by the delay circuit 6 (see FIG. 2B). The optimum value of the delay time τ, that is, the delay time τ = 63 ns in this embodiment can be determined as follows.

That is, the optimum value of the delay time τ is the characteristics of the optical disk 11, the light quantity of the laser light L1 and the optical disk 1.
1 and the relative speed of the laser beam L1 and the like, and the optimum value is different for each optical disk recording device. Therefore, first, the test writing area of the optical disk 11 (not shown, for example On the inner circumference side, writing is performed by the writing laser beam L1 with a delay time τ = 0 to form a pit. Next, the system controller 7 calculates the asymmetry of the reproduction signal S6 formed based on the laser light L2 that is the light reflected from the pit by the laser light for reading, and calculates the calculated asymmetry and the asymmetry of a predetermined constant value. The system controller 7 will be compared. This (delay time τ =
The asymmetry value at time 0) does not match the predetermined constant value.

Therefore, next, the delay time τ is calculated based on the signal S7 output from the system controller 7.
The value is gradually increased from = 0, the asymmetry is calculated each time, and the delay time τ at which the asymmetry becomes a predetermined constant value may be determined as the optimum delay time. In this way, the system controller 7 can be used to automatically determine the optimum delay time. The predetermined constant value of the asymmetry may be set, for example, by measuring in advance a value that minimizes the data error of the read data and setting the value.

The delay time τ is the so-called DRAW (Direct
Rread After Write) method. That is, for example, while forming a pit in the trial writing area with the writing laser light L1, the light amount of the laser light L2 that is the reflected light of the laser light L1 is detected by the optical pickup 9 and the system controller 7 by sampling processing or the like. Thus, the shape of the formed pit is determined, and the delay time τ is adjusted by the system controller 7 according to the shape, and similarly, the optimum delay time τ is automatically determined in real time. (See, for example, Japanese Patent Application No. 1-214139).

The optimum delay time τ determined in this way is set in the delay circuit 6 by the system controller 7, and the signal S2 obtained at the output side of the delay circuit 6 is
As shown in FIG. 2B, the waveform is delayed by the delay time τ with respect to the clock signal CK.

Therefore, the signal S3 obtained at the output side of the OR circuit 4 has the signal waveform shown in FIG. 2C. The duty ratio R of the signal S3 is the ratio of the cycle T of the clock signal CK and the high level period Th (see FIG. 2C) of the signal S3. In this embodiment, R = Th / T = (τ + T / 2) / T
= (65 + 115) / 230 = 0.783, which is about 78%. The duty ratio R of the signal S3 is selected to be 50% or more and less than 100%. If it is less than 50%, the formed pits become discontinuous pits in channel clock units, and if it is 100%, the conventional technology (Fig. 3E).
(See)) itself.

On the other hand, since the other input of the AND circuit 2 is supplied with the binary continuous signal S1 (see FIG. 2E) whose channel bit state is shown in FIG. 2D (the same as FIG. 3A), the AND circuit is supplied. At the output of 2, the pulse signal S4 shown in FIG. 2F is obtained.

The pulse signal S4 is voltage-current converted by the driver 8 and supplied to the optical pickup 9 as a signal S5, so that the writing laser beam L1 which is on / off controlled in accordance with the signal S5 (S4) is an optical disk. 11 is supplied.

As described above, since the laser light L1 is set in advance so that the delay time τ is optimal, as shown in FIG. 2G, pits having an optimal shape that does not have a teardrop shape are formed. It is formed on the optical disc 11.

As described above, according to the above-described embodiment, the pulse signal S4 obtained by dividing the supplied binary continuous signal S1 by the waveform shaping circuit 1 into the cycle (unit) T of the clock signal CK.
And is supplied to the optical pickup 9. Therefore, the optical output waveform of the laser light L1 which is the writing light output from the optical pickup 9 is the pulse signal S.
The waveform corresponds to 4.

Therefore, the same comparison as the output by the continuous signal (see FIG. 3E) according to the prior art is made without using the high output narrow pulse having the duty ratio of less than 50% (see FIG. 3C) as described in the prior art. Low power laser light L
Even if 1 is used, the teardrop pit shape can be prevented from occurring. In addition, compared with the continuous signal (see FIG. 3E) according to the conventional technique, the continuous signal pulse signal S4 shortens the laser light generation time, and thus the replacement life (predicted life) of the laser diode is extended.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0039]

As described above, according to the present invention,
The supplied binary continuous signal is converted into a pulse signal divided into clock signal units and supplied to the light beam generating means. Therefore, the light output waveform of the light beam output from the light beam generating means has a waveform corresponding to the pulse signal. Therefore, it is possible to obtain an effect that it is possible to prevent the teardrop-shaped pit shape from occurring even when a light beam having a relatively low output is used. Further, since the light beam generation time is shortened, the effect that the replacement life of the light beam generation means is extended is also obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an embodiment of an optical disc recording apparatus according to the present invention.

FIG. 2 is a diagram for explaining the operation of the example in FIG.

FIG. 3 is a diagram provided for explaining an operation of a conventional technique.

[Explanation of symbols]

 1 waveform shaping circuit 6 delay circuit 9 optical pickup 11 optical disc S1 binary continuous signal S4 pulse signal CK clock signal

Claims (3)

[Claims] 1. A light beam generating means for generating a light beam for writing a pit of a predetermined length on an optical disc as a continuous signal, and a binary continuous signal and a clock signal are supplied to drive the light beam generating means. An optical disc having a signal processing means, wherein the signal processing means converts the binary continuous signal into pulse signals divided into the clock signal units and supplies the pulse signals to the light beam generating means. Recording device. 2. The duty of the pulse signal is 50% or more.
The optical disk recording device according to claim 1, wherein the optical disk recording ratio is less than 100%. 3. The optical disk device according to claim 1, wherein the optical disk is a write-once optical disk.