JPH11134692A - Optical disk recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the output power of a laser by making the central part of recording pulses converted into a pulse string non-pulses when a recording pulse width is a pre-determined length to subject one part of the monitoring output of a constant laser power to a sample-and-hold. SOLUTION: When high levels of recording signals are continued for a period equal to or longer than a prescribed period, a pulse control part 13 makes the central part other than the front edge pulse and the rear edge pulse of the pulse string non-pulses and outputs a flag indicating that the making of pulses non-pulses is executed to a timing generating part 11. The part 11 receives this flag and generates sampling pulses whose period is shorter than a period when pulses being in monitoring signals are converted into the non- pulse part by clocks a front clock and a rear clock to output them to a sample- and-hold part 8. Then, the input signal of the sample-and-hold part 8 is subjected to sample-and-hold by these sampling pulses. Thus, the operating speed of the part 8 is suppressed low.

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 capable of controlling a recording laser power applied to an optical disk, and more particularly to an optical disk recording apparatus capable of detecting and controlling a laser power at a relatively low speed and at low cost. is there.

[0002]

2. Description of the Related Art An optical disk recording apparatus capable of recording information on a write-once optical disk or a rewritable optical disk irradiates a laser beam during recording to form pits (marks) by utilizing various changes in a recording film. , Record the data. For example, in a write-once optical disk using an organic dye for a recording film, data is recorded by changing the optical constant of the dye and the groove shape of the substrate by increasing the temperature during irradiation with a recording laser. Also, in order to suppress the influence of the temperature gradient on the recording film and prevent tear-shaped pits from being formed due to heat diffusion, multi-pulse recording is performed in which a recording pulse of a recording signal is converted into a pulse train for recording. Conventionally, such an optical disc recording apparatus is provided with an APC (Automatic) so that the laser beam power during recording is constant.
A Power Control circuit is provided.

FIG. 3 is a schematic configuration diagram of an example of a conventional APC circuit. In the figure, 1 is an optical disk, 2 is a spindle motor, 3 is an optical pickup, 4 is an LD (Laser Diode), 5 is a photodiode, 6 is a prism mirror, 7 is an amplifier, and 8 is a sample hold (S / S).
H: Sample / Hold) section, 9 a comparison section, 10 an LD driver, 11 a timing signal generation section, and 12 a multi-pulse generation section.

The optical disk 1 is a write-once optical disk having an organic dye as a recording film, and is rotated at a constant linear velocity by a spindle motor 2. The optical pickup 3 incorporates a laser diode 4 and a monitoring photodiode 5.

At the time of recording, a laser beam emitted from the laser diode 4 is irradiated on the optical disc 1. By heating the recording film of the optical disk 1 at the portion irradiated with the laser beam, the optical constant of the recording film changes and the groove shape of the substrate changes, so that information is recorded as a pit row.

A recording pulse of a recording signal applied to the optical disk 1 is converted into a pulse train by a multi-pulse generating unit 12, and then the laser diode 4 is transmitted through an LD driver 10.
Supplied to A part of the laser beam emitted from the laser diode 4 is reflected by the prism mirror 6 and supplied to the photodiode 5 for monitoring the laser beam power. After the output of the photodiode 5 is amplified by the amplifier 7, the low level of the recording signal, that is, the intensity of the laser beam corresponding to the bias state of the laser power is sampled as a monitor output by the sample and hold unit 8,
It is held.

The timing signal generating section 11 generates a timing signal necessary for operating the sample and hold section 8 at a timing corresponding to the low level period as described above. The hold signal of the level according to the bias power of the laser power is compared with the reference level by the comparator 9, and an error signal corresponding to the difference is fed back to the LD driver 10. Thereby, the laser diode 4
Is kept constant.

FIG. 4 is a timing chart showing the sample and hold timing in the APC circuit of the conventional optical disk recording apparatus shown in FIG. (A) is a recording signal, which is input to the multi-pulse generator 12 and the timing signal generator 11. (A ′) is a recording signal in which a recording pulse is converted into a pulse train by the multi-pulse generator 12, and the LD driver 10 and the timing generator 11
Is input to (B) is an inverted signal of the recording signal (A). (C) is a monitor signal detected by the monitoring photodiode 5 and input to the sample and hold unit 8. As the monitor signal (C), the recording signal (A) is given to the laser diode 4 and a part of the emitted light is
And is output from the photodiode 5 and is temporally delayed from the recording signal (A).

The timing signal generator 11 receives the recording signal (A) and inverts the recording signal (A) to generate a signal (B). Further, a signal (D) is created by delaying the recording signal (A) by, for example, 1T from the monitor signal (C), and a signal (E) is created by inverting the signal (D). The inversion signal (B) of the recording signal (A) and the inversion signal (E) of the signal obtained by delaying the recording signal (A) are generated at the low level of the monitor signal (C), that is, the pulse train. This is for detecting the bias level of the recording signal (A ′) converted into the above. When detecting the recording power level of the monitor signal (C), it is not necessary to invert the signal (A) and the signal (D).

The timing signal generator 11 includes an AND circuit, which performs an AND operation on the signal (B) and the signal (E) to generate a timing pulse (F). The timing pulse (F) has a pulse width shorter than the width between recording pulses of the recording signal (A) (width at the time of bias level). Further, when detecting the recording power level of the recording signal (A ′) obtained by converting the recording pulse of the monitor signal (C) into a pulse train,
As shown in FIG. 4 (G), it is necessary to generate a timing pulse shorter than each pulse width of the recording pulse of the monitor signal (C) and located within the pulse width.

Therefore, when sampling and holding the entire period corresponding to the low level of the recording signal, ie, the bias level of the laser power, the pulse interval of the recording signal (A) is 3T (114 ns), 4T of the DVD recording signal.
(152 ns), it is necessary to reduce the width of the timing pulse (F) to 3T, 4T or less,
Unless the sampling speed of the sample and hold circuit is increased, accurate values (output levels) cannot be held,
Therefore, there is a problem that the power of the laser beam output from the laser diode 4 becomes unstable.

When detecting a high level of a recording signal, that is, a recording power level of a recording signal (A ') obtained by converting a recording pulse into a pulse train, a timing pulse (G) signal for detecting the recording power is used. The pulse width of
There is a problem that it is necessary to make the pulse width shorter than each pulse width of the pulse train, and the sampling speed of the sample-and-hold circuit must be higher than when sampling and holding the bias level of the recording signal.

[0013]

As described above, the conventional A
In the PC circuit, the recording pulse width of the recording signal or the interval between the recording pulses is shortened, and the operation speed required for the sample-and-hold unit 8 is increased with the pulse train of the recording pulses. In particular, write-once digital versatile discs (DVD-R: Digital Versatile)
In the case of disc-recordable, etc., when the data clock cycle is T (about 38 ns), the 8-16 modulated recording signal has a width from 3T to 11T, and when a short pit interval such as 3T or 4T continues, A high-speed sample and hold circuit is required. Further, the recording power level is detected and A
When PC is to be performed, a very high-speed sample and hold circuit is required because each pulse width of a signal obtained by converting a recording pulse into a pulse train is about 25 ns.

Therefore, the components constituting the sample-and-hold circuit become expensive and the circuit itself becomes complicated. Also, as the operation speed of the sample-and-hold circuit increases, the period of the timing pulse also becomes shorter, and the pulse noise resulting therefrom also has a greater effect on other circuits. The diode may be destroyed.

The present invention has been made in view of the above circumstances, and uses a relatively inexpensive and simple configuration to stably sample and hold a part of a monitor output of a laser power to reduce the output power of a laser diode. It is an object of the present invention to provide a controllable optical disk recording device.

[0016]

According to a first aspect of the present invention, there is provided an optical disk recording apparatus for monitoring a semiconductor laser and an output of a laser beam emitted from the semiconductor laser. Output detecting means, sample and hold means for sampling and holding a level of a monitor signal from the output detecting means, and a signal level sampled and held by the sample and hold means and a predetermined reference level. Comparing means for comparing the current and the recording signal, a semiconductor laser driving means for controlling a current supplied to the semiconductor laser according to the difference and the recording signal detected by the comparing means, and a recording pulse of the recording signal. Multi-pulse generating means for converting the recording pulse into a pulse train in accordance with the width, and the width of the recording pulse being a predetermined length A pulse control unit that makes a central portion of the recording pulse converted into a pulse train by the multi-pulse generating unit a non-pulse portion; and a pulse width of the recording pulse is a predetermined length. And a timing signal generating means for instructing a timing for sampling and holding.

According to a second aspect of the present invention, in the optical disk recording apparatus according to the first aspect, the pulse control means detects a specific level period of the recording signal, and detects the specific level of the detected recording signal. Determining whether or not the period of the recording signal is a predetermined period, and supplying a flag to the sample and hold means when determining that the specific level of the recording signal is the predetermined period. It is.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical disk recording apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a main part of an optical disc recording apparatus according to one embodiment of the present invention. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, reference numeral 13 denotes a pulse control unit. FIG. 2 is a timing chart showing the timing of the sample hold in FIG.

In FIG. 1, a recording signal is obtained by modulating data to be recorded, for example, by 8-16 modulation, and is a binary signal in which a recording pulse width and an interval between recording pulses are restricted from 3T to 11T. is there. In addition, a predetermined synchronization signal is added at regular intervals between the recording data. The synchronization signal uses a data pattern that has a pit length that does not exist in the rule of 8-16 modulation so as to be clearly distinguished from data. In particular,
This is a pattern having a recording pulse width of 14T. Here, T is the data clock cycle, which is about 38 ns.

The recording signal is converted into a pulse train in a multi-pulse generator 12 in order to suppress the influence of the temperature distribution on the recording film on the optical disk and to prevent the formation of tear-shaped pits due to the diffusion of heat. 13 to the LD driver 10. Multi-pulse generator 1
In 2, the period (recording pulse) corresponding to the pit of the recording signal is converted into a pulse train composed of a plurality of pulses. Further, in order to sharpen the leading edge of the pit, the widths of the first pulse and the subsequent pulses are changed. For example, when one recording pulse is composed of four pulse trains, the width of the first pulse is set wider than the width of the subsequent three pulses. As described above, by changing the laser output period of the pulse train in a short time based on the recording signal and increasing the recording power of the laser, pits with sharp edges can be formed.

The pulse control section 13 keeps only the leading edge and the trailing edge of a recording signal having a period corresponding to a pit of the recording signal for a predetermined period, for example, a period of 10 T or more. Is converted to a non-pulse part which is not a pulse train.

The LD driver 10 generates two levels of power, a recording power for forming pits and a bias power for not forming pits. The two power levels are
Although each power level may be generated, in this embodiment, L for generating bias power is used.
When the D drive current is always generated and the recording power is generated, a current obtained by subtracting the bias power current from the current required for the recording power is added to the bias power current.

The laser diode 4 driven by the LD driver 10 emits a laser beam based on two levels of laser power according to a recording signal. A part of the laser beam is made incident on a power monitoring photodiode (PD) 5 by a prism mirror 6 on the way. The remaining laser beam passes through the prism mirror 6 and is focused on the optical disc 1 at a position where recording is required. The optical disk 1 is, for example, a write-once DVD disk (hereinafter, referred to as “DVD-R”) using a dye for a recording film.

On the optical disc 1, when a recording laser for forming pits is focused, the temperature of the recording film rises, the optical constant of the recording film changes, and the groove shape of the substrate changes. Pits are recorded. When the bias power is applied to the laser diode 4, the above-mentioned change does not occur, so that no pit is formed. In this way, pits corresponding to the recording signal are recorded. A current corresponding to the laser power is generated in the photodiode 5 by a part of the laser beam supplied to the monitoring photodiode 5. This current is converted into a voltage by the amplifier 7 and amplified.

The output level of the monitoring photodiode 5 amplified by the amplifier 7 is adjusted by the sample and hold unit 8.
Supplied to The sample hold section 8 is supplied with a sample pulse from the timing signal generation section 11. With this sample pulse, the output level of the photodiode 5 is sampled and held by the sample and hold unit 8.

The output of the sample-and-hold unit 8 is supplied to a comparator 9
Is input to In the comparing unit 9, a reference set voltage is supplied as a reference value for setting the recording power. The reference setting voltage is set so that a current such that the laser beam power at the recording level becomes appropriate is supplied to the laser diode 4. The comparison unit 9 amplifies and integrates the difference between the reference set voltage and the voltage held by the sample and hold unit 8. The integration is for controlling the operation response characteristics of the APC. Generally, the laser temperature change is not so sharp, so that the response characteristics can be limited as necessary.

An error voltage output between the reference set voltage and the voltage held by the sample hold unit 8 obtained by the comparison unit 9 is supplied to the LD driver 10. LD driver 1
0 controls the drive current for generating the recording power of the laser diode 4 according to the supplied error voltage.

If the sample-and-hold unit 8 constantly samples and holds the output of the photodiode 5 according to the recording power of the laser diode 4, a very high operation speed is required for the sample-and-hold circuit. The noise generation due to is also increased. The recording pulse of the recording signal is formed into a pulse train by the multi-pulse generator 12, and each pulse width is only about 25 ns. For example, in order to sample and hold the intermediate point, an acquisition time (acquisition time) of half the period, that is, within 13 ns, must be achieved, which is difficult to realize.

Therefore, in the optical disk recording device of the present embodiment, as described above, the pulse control unit 13
The high level of the recording signal is for a predetermined period, for example,
When 10T or more is continued, the central portion of the pulse train excluding the leading edge and trailing edge pulses is set as a non-pulse portion. And
Only during the non-pulse section, the timing signal generator 11 generates a sample pulse. Therefore, the sample and hold section 8 can sample and hold the monitor output from the photodiode 5 corresponding to the recording power, so that the acquisition time can be made relatively long, and the circuit configuration can be made simple and inexpensive. is there. Further, the influence of pulse noise on other circuits can be reduced.

Further, in the optical disk recording apparatus according to the present embodiment, since the leading edge and the trailing edge of the recording signal for a predetermined period are left as pulses, the influence of the temperature gradient on the recording film is suppressed, and the diffusion of heat is prevented. A tear-shaped pit can be prevented from being formed.

That is, the multi-pulse generating unit 12
From the input recording signal shown in FIG. 2A, a pulse train is generated in a period corresponding to a pit as shown in FIG.
When the period corresponding to the pit of the recording signal in FIG. 2A is a predetermined period, that is, 10 T or more in the present embodiment, the pulse control unit 13 performs the operation as shown in FIG. It operates so as to generate a signal obtained by converting a pulse train at the center other than the leading edge and the trailing edge into a non-pulse part. At this time, when the period corresponding to the pit of the recording signal in FIG. 2A continues for 10 T or more, the pulse control unit 13 sets the timing signal generation unit 11 with a flag indicating that non-pulsing has been performed. Is output. This flag is output after being delayed by a delay circuit (not shown) so as to be temporally coincident with a signal monitored by a sample and hold unit 8 described later.

The recording signal output from the pulse controller 13 drives the laser diode 4 inside the optical pickup 3 via the LD driver 10 to emit recording laser light. A part of this recording laser light is reflected by the prism 6 and generates a current in the photodetector 5 for monitoring in accordance with the laser power. This current is converted into a voltage by the amplifier 7 and amplified, and then monitored by the sample and hold circuit 8. This monitor output signal is shown in FIG. The monitor output signal is driven via the LD driver 10,
A state in which there is a delay before detection is also shown.

The timing signal generator 11 receives the flag output from the pulse controller 13 indicating that the non-pulsing operation has been performed. When the flag is detected, the timing signal generator 11 generates a signal as shown in FIG. A sample pulse (E) for sampling and holding the monitor output signal is generated. For example, the sample pulse is generated so as to be shorter by one clock (1T) before and after the period converted into a non-pulse part in the monitor signal.

The input signal of the sample hold unit 8 is sampled and held by the sample pulse generated as described above. Therefore, a relatively wide 10
Since the sample and hold can be performed over almost the entire high level of the recording signal having a period of T or more, the operation speed required of the sample and hold unit 8 is compared with the case where the recording levels of all the recording signals are sampled and held. It can be kept extremely low.

In the present embodiment, the period of the recording signal to be sampled and held is set to 10T or longer. However, the sample and hold may be performed for other periods or longer. Further, the recording signal to be sampled and held is left for each pulse of the leading edge and the trailing edge of the pulse train, but a plurality of pulses may be left.

It should be noted that the above-described sample hold unit 8, comparison unit 9, timing signal generation unit 11, pulse control unit 13
The multi-pulse generation unit 12 may be configured by a suitable part of a hardware circuit, or may be realized by software for controlling a CPU.

[0037]

As is apparent from the above description, according to the optical disk recording apparatus of the present invention, the recording pulse width of the recording signal is reduced in the optical disk recording apparatus that records pits or marks by converting the recording pulses into a pulse train. With respect to a recording pulse having a predetermined period, only the leading edge and the trailing edge are left as pulses, and the remaining central part is converted into a non-pulse part. And only for the non-pulse part,
Since the output level of the monitoring photodiode that detects the output power of the laser diode is sampled and held, the power of the laser beam output from the laser diode can be stabilized even for a pulse train recording signal with a short pulse interval. Can be controlled.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an optical disk recording device according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the timing of sample hold in FIG.

FIG. 3 is a schematic configuration diagram of an example of a conventional APC circuit.

4 is a diagram showing an AP of the conventional optical disc recording apparatus in FIG.
6 is a timing chart showing the timing of sample hold in the C circuit.

[Explanation of symbols]

 Reference Signs List 1 optical disk 2 spindle motor 3 optical pickup 4 laser diode 5 photo diode 6 prism mirror 7 amplifier 8 sample hold unit 9 comparison unit 10 LD driver 11 timing signal generation unit 12 multi-pulse generation unit 13 pulse control unit

Claims (2)

[Claims] A semiconductor laser; an output detection means for monitoring an output of a laser beam emitted from the semiconductor laser; a sample and hold means for sampling and holding a level of a monitor signal from the output detection means; Comparing means for comparing a signal level sampled and held by the sample and hold means with a predetermined reference level to detect a difference; and the semiconductor according to the difference and the recording signal detected by the comparing means. A semiconductor laser driving unit that controls a current supplied to a laser; a multi-pulse generating unit that converts the recording pulse into a pulse train in accordance with a recording pulse width of the recording signal; and a width of the recording pulse that is a predetermined length. If so, a pulse that makes the central part of the recording pulse converted into a pulse train by the multi-pulse generating means a non-pulse part An optical disc, comprising: a control means; and a timing signal generating means for instructing the sample and hold means to sample and hold when the width of the recording pulse is a predetermined length. Recording device. 2. The optical disk recording apparatus according to claim 1, wherein the pulse control means detects a period of the specific level of the recording signal, and the detected period of the specific level of the recording signal is a predetermined period. An optical disc recording apparatus characterized in that it is determined whether or not there is, and when it is determined that the specific level of the recording signal is within a predetermined period, a flag is supplied to the timing generating means.