KR100618841B1 - Optical disc recorder and method for compensating optical power - Google Patents

Abstract

It is an object of the present invention to provide an optical disc recording apparatus and an optical output power correction method for removing the influence of transient response characteristics of a power monitor in a simple manner.

Drive means for supplying a driving current to the semiconductor laser, monitoring means for sampling and monitoring the output power of the semiconductor laser, and values obtained from the monitoring means and a preset value to obtain a desired recording laser output. And a drive current control means for controlling the drive current, and the influence of the transient response characteristic of the power monitor is eliminated by a set value variable means for varying a preset value according to a recording condition when pulse driving the semiconductor laser. An optical disc recording apparatus and an optical output power correction method are provided.

Description

Optical disc recorder and method for compensating optical power

1 is a configuration diagram of an optical disk recording apparatus according to the present embodiment.

2 is a configuration diagram of a drive current control block according to the present embodiment.

3 is a flowchart showing the correction of the optical output power according to the present embodiment.

It is a figure explaining the symbol of arithmetic expression.

5 is a diagram showing the transient response characteristics when the optical output power is small.

6 is a diagram illustrating the transient response characteristics when the pulse width is long.

Fig. 7 is a diagram showing the relationship between recording power, mark portion, and space portion.

8 is a diagram illustrating a power monitor signal when there is a transient response.

[Description of the code]

One… Optical disc

2… Optical pickup

3... APC

4… RF amplifier

5... Servo circuit

6... Signal processing circuit

7... CPU

8… driver

9... Memory

11,15... amplifier

12... LD driver

13... Semiconductor laser

14... Front monitor diode

16... Sample hold circuit

17... H level comparison circuit

18... L level comparison circuit,

The present invention relates to an optical disk recording apparatus for recording information on an optical disk and an optical output power correction method for correcting optical output power when recording information on an optical disk.

Recently, with the development of information-related technology, a large amount of information is exchanged through communication lines such as the Internet. In order to store and manage such a large amount of information, an optical disk having a small and large recording capacity has attracted attention as a recording medium. In an optical disc recording apparatus for recording information on such an optical disc, the output power of the semiconductor laser for recording the information on the optical disc is detected by a power monitor and the output power of the semiconductor laser is detected in order to satisfy the recording quality required for reading the information. The laser output power was controlled by detecting the difference between the target value and the target value and controlling the drive current having a constant relationship with the output power of the semiconductor laser (see Patent Document 1, for example). However, if there is a problem in the transient response characteristic of this power monitor, there is a problem in that the power of the mark portion or the space portion forming the information of the optical disc changes during recording.

In the case of using the CD-R as the optical disc, the above problem will be described in detail. In the recording operation using the CD-R, as shown in FIG. The portion is recorded by increasing the optical power of the semiconductor laser with respect to the mark portion and decreasing the optical power of the semiconductor laser with respect to the space portion.

At this time, the optical power of the mark portion and the space portion sample-holds the power monitor signal as shown in FIG. 8, compares the value obtained from this sample hold with the target value, and controls the optical power to the target value by the APC. However, if the power monitor signal has a transient response, the correct monitor signal originally expected cannot be obtained, and as a result, the desired optical power cannot be generated. In particular, as shown in Figs. 5 and 6, this may not be a problem when the optical power is small or the pulse width is sufficiently large, but this problem becomes remarkable when the original power monitor signal is large and the width of the space portion is narrow. In the case of high-speed recording, the effect is large because the sample hold timing is relatively faster and a large optical output power is required.

In such a case, in the conventional method, the variation of the optical output power in the space portion is particularly large, and as a result, this affects the servo circuit and the like, resulting in a decrease in recording quality. Furthermore, it is known that the above-described transient response problem is caused by the deterioration of the frequency characteristic of the power monitor or the influence of the diffusion current of the device.

[Patent Document 1]

Japanese Patent Laid-Open No. 8-007320 (pages 2 to 5, Fig. 1)

Accordingly, an object of the present invention is to provide an optical disk recording apparatus and an optical output power correction method for removing the influence of the transient response characteristics of a power monitor in a simple manner.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention proposes the following means.

The invention according to claim 1 is an optical disk recording apparatus for recording information using a semiconductor laser on an optical disk, comprising: driving means for supplying a driving current to the semiconductor laser, monitoring means for sampling and monitoring output power of the semiconductor laser; And a drive current control means for controlling the drive current based on a value obtained from the monitoring means and a value set in advance in order to obtain a desired recording laser output, and according to a recording condition when the semiconductor laser is pulse driven. There is proposed an optical disc recording apparatus having a set value varying means for varying a set value set in the above.

The invention according to claim 6 is an optical output power correction method of an optical disk recording apparatus for recording information on a optical disk using a semiconductor laser, the method comprising: supplying and driving old coins to the semiconductor laser, and output power of the semiconductor laser; Sampling and monitoring; controlling the drive current based on a monitored value and a preset value to obtain a desired recording laser output; and pre-according to recording conditions when pulse driving the semiconductor laser. There is proposed an optical output power correction method characterized by having a step of varying a set value set in the following.

According to the present invention, the driving current control means controls the driving current of the semiconductor laser based on the output power of the semiconductor laser monitored by the monitoring means and the preset setting value, and recording when the setting value varying means pulses the semiconductor laser. Since the preset value is set in accordance with the conditions, the recording laser output power can be optimally controlled even if the sampling timing is increased or the recording pulse width is shortened, for example, by increasing the recording speed.

The invention according to claim 2 has another detecting means for detecting the output power of the semiconductor laser with respect to the optical disk control device according to claim 1, wherein the pulse width of the recording pulse when pulse driving the semiconductor laser is a predetermined pulse width. Narrower and when the desired laser output is detected by the detection means, the setting value varying means changes the preset value to a setting value corresponding to a monitor value obtained from the monitoring means. Proposing a device.

According to the present invention, since the setting value varying means changes the preset setting value to a setting value corresponding to the monitor value when the pulse width of the recording pulse is narrower than the predetermined pulse width and the desired laser output is obtained. Even though the desired laser output is obtained, malfunction of the control means caused by the transient response characteristic of the monitoring means can be prevented. Further, as other detection means, the laser output power may be monitored when a DC value (constant current) corresponding to each drive current of pulse driving is applied, or a detector may be used in which the transient response characteristic is not a problem. The output power may be detected or another method may be used.

The invention according to claim 3 proposes an optical disc recording apparatus, wherein the setting value varying means changes the preset value to a setting value determined by an arithmetic expression for the optical disc recording apparatus according to claim 1. .

According to the present invention, the set value varying means varies a preset set value so as to cancel the transient response characteristic of the monitoring means by an arithmetic formula obtained from experimental data or the like.

The invention according to claim 4 has a data table in which the sampling timing and the recording power are associated with the optical disc recording apparatus according to claim 1, wherein the setting value varying means is set based on the corresponding sampling timing and recording power at the time of recording. There is proposed an optical disk recording apparatus characterized by varying values.

According to the present invention, since it has a data table in which the sampling timing and the recording power are related, knowing the sampling timing and the recording power at the time of recording, the set value can be appropriately controlled accordingly.

The invention according to claim 5 has a data table in which the recording speed and the recording power are related to the optical disc recording apparatus according to claim 1, wherein the setting value varying means varies the setting value based on the recording speed at the time of recording. An optical disc recording apparatus is proposed.

The timing of the sample hold and the recording power depend on the recording speed. Therefore, according to the present invention, since it has a data table which associates the recording speed with the recording power, knowing the recording speed at the time of recording, the set value can be appropriately controlled accordingly.

Hereinafter, an optical disc recording apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS.

As shown in FIG. 1, an optical disc recording apparatus according to an embodiment of the present invention includes an optical disc 1, an optical pickup 2, an APC (Auto Power Control) 3, an RF amplifier 4, and a servo circuit 5 And a signal processing circuit 6, a CPU (Central Processing Unit) 7, a driver 8, and a storage unit 9 are provided.

The optical disc 1 is, for example, a CD-R, a CD-RW, a DVD-R, a DVD-RW, or the like as a recording medium capable of recording, reproducing and erasing information by a semiconductor laser. The optical pickup 2 is an optical component such as an objective lens, a polarizing beam splitter, a cylindrical lens driven by a laser light source such as a laser diode, not shown, a collimator lens, a focus actuator or a tracking actuator, and A, B, C, D A four-segment photo detector (PD) for dividing light into an electrical signal or a front monitor diode for monitoring laser output during recording and reproduction. The APC 3 is a control block for monitoring the current from the front monitor diode in the optical pickup 2 to control the emission power of the semiconductor laser to a desired value.

The RF amplifier 4 detects the reflected light from the optical disk 1, calculates the reflected light amount from the detected reflected light, generates an RF signal representing the total amount of reflected light to each region of the 4-split PD, and at the same time, for example, The tracking error signal TE, which is a signal which generates a focus error signal FE, which is a signal for detecting the focus shift of the irradiation laser of 1), by astigmatism and detects a track shift of the irradiation laser of the optical pickup 1; Create The servo circuit 5 generates the focus drive signal FODDR and the tracking drive signal TRDRV based on the FE, TE, and RF generated by the RF amplifier 4.

The signal processing circuit 6 inputs the EFM signal generated from the RF signal and processes the data, and has a PLL circuit not shown to control the rotation of the spindle motor. The CPU 7 controls the entire apparatus based on a control program stored in a ROM (Read Only Memory) or the like. In this embodiment, a process is performed in which the set value is varied so that the recording power is optimized by comparing the detected value of the front monitor diode with the set value.

The driver 8 inputs the focus drive signal FODRV generated by the RF amplifier 4, the tracking drive signal TRDRV, or the spindle control signal generated by the signal processing circuit 6, and amplifies them to a desired size. Supply to focus actuator, tracking actuator or spindle motor. The storage unit 9 is a rewritable storage device such as a RAM (Random Access Memory). In the present embodiment, the data table, the recording speed and the recording power relating to the set value of the driving current of the semiconductor laser, the sampling timing and the recording power, The associated data table is stored.

As shown in FIG. 2, the optical power control block APC 3 includes the amplifiers 11, 15, the LD driver 12, the semiconductor laser 13, the front monitor diode 14, and the sample hold circuit ( 16, the H level comparison circuit 17, the L level comparison circuit 18, the CPU 7, and the storage unit 9.

The amplifier 11 voltage-amplifies the difference value detected by the H level comparison circuit 17 and the L level comparison circuit 18 and supplies it to the LD driver 12. The LD driver 12 converts the voltage value input from the amplifier 11 into a current value, and then amplifies the LD driver 12 into a current having a magnitude necessary to obtain a desired laser output power and supplies it to the semiconductor laser 13.

The semiconductor laser 13 is a semiconductor element which emits laser light according to the supplied current value, and emits a laser, for example, at the junction surface of the P-type semiconductor and the N-type semiconductor. The front monitor diode 14 receives a portion of the laser light emitted by the semiconductor laser and outputs a current according to the power of the received light.

The amplifier 15 amplifies the voltage obtained by converting the current output from the front monitor diode 14 by a current voltage converter (not shown) and supplies it to the sample hold circuit 16. The sample hold circuit 16 inputs the write voltage input from the amplifier 15 and samples at a predetermined sampling timing. Moreover, the sampling timing is variable depending on the recording speed and the like. The sampled value is divided into H level and L level values and supplied to the H level comparison circuit 17 or the L level comparison circuit 18, respectively. The above-mentioned round turns the APC and operates so that the input from the sample hold circuit 16 of the comparison circuit matches the set value input from the CPU.

Next, the operation of the optical disk recording apparatus in this embodiment will be described with reference to FIG.

First, the semiconductor laser 13 emits DC light at a preset value and the input value of the LD driver 12 is monitored. Since DC light emission is not affected by the transient response at all, this value is taken as a reference value (step 101). Next, the semiconductor laser 13 is sequentially pulsed to the other two set values, and the input values of the LD driver 12 are respectively monitored (step 102). The linear relationship between the two monitor values is used to request a set value whose pulse emission monitor value matches the reference value acquired by DC light emission (step 103). This set value is stored in the recording unit 9 as a corrected set value (step 104). Further, this process is preferably performed for each device in the manufacturing line of the optical disc device.

In addition, when there are few unevenness by each individual, a new set value can be determined by the calculation formula required from the experimental value, thereby controlling the optical output power of the semiconductor laser. For example, if the output power set value of the semiconductor laser is Ym, the lower limit set value is Ys, the sampling timing is Th, and the sample value at this sampling timing is Yh, as shown in FIG.

[Equation 1]

Yh = (Ym-Ys) e ^{― th / t} + Ys

Therefore, in this relation, the correction magnification regarding the new set value becomes as shown in Equation 2.

[Equation 2]

Correction magnification = Yh / Ys = 1 + (Ym-Ys) e ^{― th / t} / Ys

The correction value for the target value of the optical output power is known to depend on the timing and recording power of the sample hold. Therefore, a data table relating the timing and recording power of the sample hold as shown in Table 1 and the correction value of the optical power at that time is stored in the storage unit 9 to detect the timing and recording power of the sample hold at the time of recording. The correction value of the optical power at that time may be obtained.

It is also known that the timing of the sample hold depends on the recording speed and the recording power also depends on the recording speed. Therefore, as shown in Table 2, a data table relating the recording speed and the optical power correction value may be stored in the storage unit 9 to detect the recording speed at the time of recording and to request the correction value of the optical power at that time.

Although the embodiments of the present invention have been described in detail with reference to the drawings, specific configurations are not limited to these embodiments, and design changes and the like within the scope of the present invention are included. For example, in the present embodiment, the CD-R has been described as an example of the optical disc. In addition, other types of optical discs may be used.

As described above, according to the present invention, the effect of the transient response characteristic of the power monitor can be eliminated by a simple method.

Claims (6)

An optical disc recording apparatus for recording information on an optical disc using a semiconductor laser, Drive means for supplying a drive current to the semiconductor laser; Monitoring means for sampling and monitoring the output power of the semiconductor laser; And a drive current control means for controlling the drive current based on a value obtained from the monitoring means and a value set in advance in order to obtain a desired recording laser output, And a set value varying means for varying a predetermined set value according to a recording condition when the semiconductor laser is pulse driven. And said set value varying means has a data table which associates said sampling timing with recording power, and varies setting values based on said sampling timing and recording power at the time of recording. The method of claim 1, further comprising other detecting means for detecting the output power of the semiconductor laser, When the pulse width of the recording pulse when pulse driving the semiconductor laser is smaller than a predetermined pulse width and the desired laser output is detected by the detection means, the setting value varying means monitors the preset value set in advance. And a setting value corresponding to a monitor value obtained from the means. An optical disc recording apparatus according to claim 1, wherein said setting value varying means changes said predetermined setting value to a setting value determined by an arithmetic expression. delete An optical disc recording apparatus according to claim 1, further comprising a data table in which a recording speed is associated with a recording power, and wherein said setting value varying means varies the setting value based on the recording speed at the time of recording. An optical output power correction method of an optical disk recording apparatus for recording information on an optical disk using a semiconductor laser, Driving by supplying a driving current to the semiconductor laser; Sampling and monitoring the output power of the semiconductor laser; Controlling the driving current based on a monitored value and a preset value to obtain a desired recording laser output; And a data table in which sampling timing and recording power are associated with each other, wherein a setting value is varied based on a corresponding sampling timing and recording power during recording when the semiconductor laser is pulsed.

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