JPH0630155B2 - Optical disk recorder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called DRAW type optical disc recording apparatus using a disc capable of writing data.

Background art and its problems So-called DR using a disc that can write data
In the AW type optical disc recording apparatus, as shown in FIG. 1, a spiral recording track T is formed on the rotation plane of the disc (1).
In the recording track T, an address data portion (2A) and a data writing portion (2S) for information data such as a video signal are sequentially and alternately provided at a predetermined interval in the rotation direction. Has been. Address data section (2A)
In the disk manufacturing process, predetermined address data D _A has already been formed on the disk plate surface, and only the data writing section (2S) is an unrecorded section. Therefore, the user's favorite information is recorded (written) in the data writing unit (2S).

In the DRAW method, data is written by controlling the power of the laser beam applied to the disc (1). Normally, the data is written to the disc (1) when the laser power is above a predetermined laser power, for example 14mW (average value). Since the data can be written, when reproducing (reading) the information data D _S and reading the address data D _A , the laser power is a fraction of the laser power at the time of writing, for example, 1/4 of the laser power (thus 3 m).
W).

Since the data writing is performed while searching the address data D _A formed on the recording track T, when the data D _S is sequentially written to the data writing section (2S) corresponding to a predetermined address. Must sequentially read the address data D _A and write the data D _S as shown in FIGS. 2A and 2B. Therefore, this read,
It is necessary to control the laser power P _L applied to the disc (1) in accordance with the write mode to the above-mentioned predetermined value, and the corresponding laser power P _L is controlled to be constant during the selection of each mode. There is a need to.

Therefore, the optical disc recording apparatus of this kind is provided with an automatic power control circuit (10) as shown in FIG.

In FIG. 3, (4) is a semiconductor laser portion provided in the optical head, LD is a laser diode, PD is a light receiving diode for monitoring the diode LD,
In this example, it is a pin diode. Laser diode L
D is excited by the output of the driver (5), and the laser power of the laser diode LD is controlled by the magnitude of the output.

Since the current i _p flowing through the pin diode PD corresponds to the power of the laser diode LD, this current i _p
The voltage _p is converted by the current / voltage converter (6), and the converted voltage V _p is converted into the reference voltage V by the voltage comparator (7).
_It is compared with _REF and the driver is output by the comparison output.
(5) is controlled. Therefore, by such a closed loop, the laser power of the laser diode LD is obtained as a constant laser power corresponding to the reference voltage V _REF . That is, this closed loop acts as a dynamic power control (APC) circuit (10).

Then, as described above, the reference voltage V is set in each mode so that the laser power set in each of the reading and writing modes (the periods T _R and T _{W in} FIG. 2) can be obtained.
_REF is switched.

Selection circuit of the reference voltage V _REF (11) has a reference voltage setting volume V _R to be used in the reference voltage setting volume V _W and reading mode used to write mode as shown in FIG., These change-over switch (14 ) Selected.
Which reference voltage is selected is determined by the mode switching pulse P _RW (Fig. 2C) supplied to the terminal (15).

In the data writing mode, the driver output is modulated by the digital signal S _V such as the video signal supplied to the terminal 16 so that the laser power is controlled and the data corresponding to the digital signal S _V is written.

Now, in such an optical disk recording device (3), in order to prevent the laser power from changing due to disturbance during the read and write modes, a voltage comparator is used.
A loop filter (15) is provided between the driver (5) and the driver (7).

The loop filter (15) is composed of a CR time constant circuit, and its time constant τ is about 5 msec (200 Hz).

However, when the loop filter (15) having such a relatively large time constant τ is interposed in the APC circuit (10), the rise and fall of the APC loop is delayed at the time of switching between the read mode and the write mode. If the rising and falling characteristics of P _L are deteriorated as shown by the broken line in FIG. 2B, and especially the rising characteristics in the write mode are deteriorated as shown,
Data cannot be written until the laser power P _L has completely risen to the specified value.

Therefore, as shown in FIG. 3, the switch (17) is provided in series with the charging / discharging capacitor C provided in the loop filter (15), and the switching pulse P _SW (second Figure D) by much less than the loop time constant in the read mode switching start time and a write mode from the start of the change over time for a predetermined duration T _X switch (17) off to loop time constant τ a normal operation mode period The time constant is switched so that

However, even in such a case, for example, when the write mode is switched, the capacitor C is not yet charged with a sufficient voltage, so that the laser power P _L is disturbed as shown in FIG. 2E immediately after the period T _X has elapsed. I will end up. When this transient occurs, data may be written in this transient portion. The written data has nothing to do with the input information. Similarly, when the read mode is switched, the capacitor C has the reference voltage V in the read mode.
_The same transient occurs because it cannot fully discharge to _REF .

SUMMARY OF THE INVENTION Therefore, in the present invention, A which occurs immediately after the switching of the loop time constant is performed.
By eliminating the disturbance of the PC loop, it is possible to prevent writing of meaningless data at least at the time of switching the write mode, and to immediately write the input information.
We propose a DRAW type optical disc recording device.

Therefore, in the present invention, therefore, the APC loop for controlling the laser power applied to the disk (1) to a predetermined value at the time of data reading and at the time of writing, respectively,
The loop filter consists of a CR time constant circuit and a capacitor C
And a high-speed charging / discharging means, and the capacitor C is charged through the high-speed charging / discharging means at least when the data writing mode is switched so that the loop time constant at the time of switching the mode. Is designed to be small.

According to this, the loop time constant immediately after the mode switching can be made sufficiently small and the capacitor C is completely charged, so that the transient occurring immediately after the period T _X can be completely absorbed.

Embodiment Next, an example of the optical disc recording apparatus according to the present invention will be described in detail with reference to FIG.

In the present invention, the loop filter (15) has a time constant circuit (21) of a resistor R and a capacitor C, and a high-speed charging / discharging means (22).
And a changeover switch (23), the capacitor C is charged through the resistor R during the read and write modes except the period T _X , and the capacitor T is charged through the high-speed charging / discharging means (22) during the period T _X. Changeover switch (23) so that C is charged and discharged
Is connected to the time constant circuit (21). The changeover switch (23) is changed over by the switching pulse P _SW .

The high-speed charging / discharging means (22) is a voltage follower circuit having a small output impedance, which is an operational amplifier in this example.
The output impedance of the operational amplifier is very low, several hundreds
It is about Ω. On the other hand, the resistor R has a high resistance of about 100 KΩ.

In this configuration, the change-over switch (23) except the period T _X
Is switched as shown by the solid line, so the time constant τ at that time is
Is about 0.5 msec as described above, the laser power P _L does not fluctuate during the read and write modes even if disturbance occurs. Therefore, the data can be accurately read and the data can be accurately written.

On the other hand, the changeover switch (23) is changed over as shown by the broken line during the predetermined period T _X when the write mode is changed, and at this time, the output impedance of the operational amplifier (22) connected to the capacitor C is several hundred Ω. Since the output impedance and the charging / discharging time constant of the capacitor C are low, the charging / discharging time constant is about 10 μsec when the value of the capacitor C is 0.0033 μF, and the charging / discharging of the capacitor C is completed in an extremely short time.

Therefore, the rise and fall of the laser power P _L is the second
As shown in FIG. F, the capacitor becomes steep, and since the capacitor C has been charged / discharged within the period T _X for high-speed charging / discharging, the changeover switch (23) is switched to the solid line side after the period T _X. However, the potential fluctuation at the connection point P does not occur. As a result, even immediately after the lapse of the period T _X, the laser power P _L maintains the specified value set for the writing mode and the reading mode. That is, according to the configuration of FIG. 4, the transient of the laser power P _L immediately after the elapse of the period T _X can be completely removed.

As described above, according to the present invention, in the DRAW type optical disk recording apparatus, the APC loop for controlling the laser power applied to the disk (1) to a predetermined value at the time of data reading and at the time of writing, respectively. The loop filter provided in the above is composed of a CR time constant circuit (21), a time constant changeover switch (23) provided on the capacitor C side, and a high-speed charging / discharging means (22) to write data. By charging / discharging the capacitor C via the high-speed charging / discharging means (22) at the time of mode switching, the loop time constant at the time of mode switching is made extremely shorter than the time constant in other periods.

According to this, since it is possible to sufficiently reduce the loop time constant after mode switching straight, it can rise and fall of the laser power P _L suddenly崚. Further, since the capacitor C between the period T _X is fully charged and discharged, it does not occur at all potential fluctuation at the connection point P immediately after elapse of the period T _X. Therefore, the transient generated immediately after the period T _X can be completely absorbed.

From the above, according to the present invention, writing of meaningless data can be prevented, input information can be immediately written, and the address data D _A can be read correctly. It has a feature that can be done accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between a disc and recording tracks, FIG. 2 is a waveform diagram for explaining the operation thereof, FIG. 3 is a system diagram showing an example of a conventional optical disc recording device, and FIG. FIG. 1 is a system diagram showing an example of an optical disc recording device according to the invention. LD is a laser diode, PD is a pin diode, (5)
Is a driver, (10) is an APC circuit, (11) is a reference voltage V
_REF selection circuit, (15) is a loop filter, (21) is a time constant circuit, (22) is a high-speed charging / discharging means, and (23) is a changeover switch.

Claims (1)

[Claims] 1. An optical disc recording apparatus using a data writable disc, comprising an automatic power control loop for controlling a laser power applied to the disc to a predetermined value during data reading and during writing. A loop filter is provided, and this loop filter has a CR time constant circuit, a time constant switching switch provided on the capacitor side, and high-speed charging / discharging means. An optical disk recording apparatus, wherein a loop time constant at the time of switching the mode is reduced by charging the capacitor via a means.