JPS60205833A - Optical disk recorder - Google Patents

Abstract

PURPOSE:To avoid a useless data writing action by charging a capacitor of a filter set to a loop which controls the laser power irradiated on a disk by means of a high-speed charging means when a data write mode is switched. CONSTITUTION:An optical disk is irradiated by a laser diode LD, and this irradiated light is monitored by a photodetecting diode PD. This monitor output is compared with the reference voltage VREF, and the laser power of the LD is controlled via a loop filter 15 and a driver 5. The voltage VREF is switched by a mode switch pulse PRW supplied to a terminal 15. The filter 15 includes a resistance R, a time constant circuit 21 of a capacitor C, a high-speed charging means 22 and a changeover switch S23. The capacitor C is charged via the means 22 when the data writing mode is switched, and the loop time constant is reduced at the mode switching time point. This can avoid a useless data writing action and ensures accurate writing and reading actions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a so-called DR/V type optical disc recording device using a data writable disc.

Background technology and its problems So-called D using a disk on which data can be written
In a RAW type optical disk recording device, as shown in FIG. 1, a vibrator-shaped recording track T is formed on the rotating plane of the disk (1), and this recording track T has predetermined intervals in the rotation direction. is held and the address data part (2
8) and data writing sections (2S) for information data such as video signals are sequentially and alternately provided. In the address data section (2^), predetermined address data DA is already formed on the disk surface during disk manufacturing, and the data writing section (2S) is the only final recording section. Therefore, the user's preferred information is recorded in this data writing section (2S) (
written).

In the DRAW method, data is written by controlling the power of the laser beam irradiated to the disk (11), which generally involves a predetermined laser buff-1 (for example, 141).
(average value) or more, data can be written to the disk (11).When the information data DS is reproduced (continued) and the address data DA is continuously produced, the laser power is a fraction of the laser power at the time of writing. For example, the laser power is reduced to about 1/4 (therefore, about 311 IW).

Data writing is performed while searching the address data DA formed on the recording track T, so when sequentially writing data DS to the data writing section (2S) corresponding to a predetermined address, As shown in FIGS. 2A and 2H, it is necessary to sequentially repeat reading address data DA and writing data Ds. Therefore, this readout,
It is necessary to control the laser power PL irradiated to the disk (1) according to the write mode to the predetermined value described above, and it is also necessary to control the value of the corresponding laser power PL to be constant while selecting each mode. There is.

Therefore, this type of optical disc recording apparatus is provided with an automatic power control circuit αψ as shown in FIG.

In FIG. 3, (4) is a semiconductor laser section provided in the optical head, where LD is a laser diode, and PD is a light receiving diode for monitoring the diode LD, which is a bin diode in this example. The laser diode LD 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 tp flowing through the bin diode PD corresponds to the power of the laser diode LD, this current l
P is converted into a voltage by a current/voltage converter (6), and this converted voltage Vp is compared with a reference voltage VRIEF by a voltage comparator (7), and the driver (5) is controlled by the comparison output.

Therefore, due to such a closed loop, the laser power of the laser diode LD becomes a constant laser power corresponding to the reference voltage VREp. That is, this closed loop acts as an automatic power control (APC) circuit aω.

Then, the reference voltage VR is adjusted in each mode so that the respective set laser powers are obtained in the read and write modes (periods TR and Tυ in FIG. 2) as described above.
EF is switched.

As shown in the figure, the reference voltage VREP selection circuit (11) has a reference voltage setting volume Vw used in the write mode and a reference voltage setting volume vR used in the read mode.
These are selected by the changeover switch (14). The terminal (15) determines which reference voltage to select.
This is done by the mode switching pulse PRW (FIG. 2C) supplied to the switch.

In the data write mode, the laser power is controlled by modulating the driver output with a digital signal Sv such as a video signal supplied to the terminal (16), and data corresponding to the digital signal SV is written.

Now, in such an optical disc recording device (3), in order to prevent the laser power from fluctuating due to disturbance during the reading and writing modes, the voltage comparator (7) and the driver (5)' are connected to each other. A loop filter (15) is provided in between.

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

However, if such a relatively large time constant loop filter (15) is interposed in the APC circuit (φ), the rise and fall of the APC loop will be delayed when switching between read and write modes, and the laser power PL will be delayed. If the rise and rise characteristics of the laser are degraded as shown by the broken line in Figure 2B, and especially the rise characteristics in the write mode are degraded as shown, the data will not be available until the laser power PL has completely risen to the specified value. I can no longer write -C.

Therefore, as shown in Figure 3, the loop filter (15)
A charging/discharging capacitor C (!: A switch (17)' is provided in series, and the switching pulse Psw (D in Fig. 2) obtained from the pulse forming circuit (18) determines the read mode switching start point and the write mode. The switch (17) is turned off for a predetermined period TX from the start of switching, and the time constant is changed so that the loop time constant τ is much smaller than the loop time constant during the normal operation mode.

However, even if this is done, for example when switching the write mode, the capacitor C is not yet charged with sufficient voltage, so the laser power P immediately after the period Tx has elapsed.
L becomes disordered as shown in FIG. 2E. When this transient occurs, there is a risk that data will be written during this transient portion. The written data has nothing to do with the input information. Similarly, when the read mode is switched, a similar transient occurs because the capacitor C is not fully discharged to the reference voltage V, RiEF in the continuous read mode.

Purpose of the Invention Therefore, in this invention, the A
This is a DllAW optical disk recording device that eliminates disturbances in the PC disk, at least prevents writing of meaningless data when switching write modes, and also allows manual information to be written immediately. This is what we propose.

SUMMARY OF THE INVENTION Therefore, in the present invention, a loop filter is provided in an APC loop that controls the laser power irradiated to the disk (1) to predetermined values at the time of data reading and data writing, respectively, and a loop filter is set at a time constant of CR. It is composed of a circuit, a time constant switching switch provided on the capacitor C side, and a high-speed charging/discharging means, and at least when changing the data write mode, the capacitor C is charged via the high-speed charging/discharging means to switch modes. The loop time constant at a point in time is made small.

According to this, the loop time constant immediately after mode switching can be made sufficiently small, and since the capacitor C is completely charged, it is possible to completely absorb the transient that occurs immediately after the period Tx.

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

In this invention, the loop filter (15) is composed of a time constant circuit (21) of a resistor R and a capacitor C, a high-speed charging/discharging means (22), and a changeover switch (23), During write mode, resistor R
Through capacitor c7! lf is charged, and during the period Tx, the changeover switch (23) operates the time constant circuit (21) so that the capacitor C is charged and discharged via the high-speed charging and discharging capacitor (22)
). The changeover switch (23) is switched by a switching pulse PSW.

The high-speed charging/discharging means (22) uses a voltage follower circuit with low output impedance, in this example an operational amplifier. The output impedance of an operational amplifier is very low, on the order of several hundred ohms. On the other hand, resistor R is 100Ω
β+) IF antis are used.

In this configuration, the changeover switch (2
3) is switched as shown by the solid line, so the time constant τ at that time is approximately 0.5 m sec as mentioned above.
During the read and write modes, the laser power PL does not change even if a disturbance occurs. Therefore, data can be read accurately as well as data can be written accurately.

On the other hand, during the predetermined period Tx when switching the write mode, the changeover switch (23) is switched as shown by the broken line, and the operational amplifier (22) connected to the capacitor C at this time has an extremely low output impedance of several 100Ω. Therefore, the charging/discharging time constant due to this output impedance and capacitor C is approximately 1 when the value of capacitor C is 0.0033 μF.
The charging and discharging of the capacitor C is completed in an extremely short time.

Therefore, the rise and rise of the laser power PL become steep as shown in FIG. Even if the selector switch (23) is switched to the solid line side after the lapse of time, no potential fluctuation occurs at the connection point P. As a result, even immediately after the period 'rx has elapsed, both laser powers PL maintain the specified values set for the write mode and the read mode. That is, according to the configuration shown in FIG.
A transient in the laser power PL immediately after the period Tx has elapsed can be completely removed.

As described in detail, the present invention provides an APC that controls the laser power irradiated to the disk (1) to predetermined values during data reading and writing in a DRIV type optical disk recording device. installed in the loop,
The loop filter is composed of a CR time constant circuit (21), a time constant switching switch (23) provided on the capacitor C side, and a same-speed charging/discharging means (22), and the loop filter is configured with a CR time constant circuit (21), a time constant switching switch (23) provided on the capacitor C side, and a same-speed charging/discharging means (22). By charging and discharging the capacitor C via the fast charging/discharging means (22), the loop time constant at the time of mode switching is made extremely shorter than the time constant at other periods.

According to this, the loop time constant immediately after mode switching can be made sufficiently small, so that the rise and fall of the laser power PL can be made steep. Further, since the capacitor C is completely charged and discharged during the period Tx, no potential fluctuation occurs at the connection point P immediately after the period Tx has elapsed. Therefore, the transient that occurs immediately after the period Tx plane can be completely absorbed.

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

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the disc and the recording trunk, Fig. 2 is a waveform diagram to explain its operation, Fig. 3 is a system diagram showing an example of a conventional optical disc recording device, and Fig. 4 is a diagram showing the relationship between the disc and the recording trunk. The figure is a system diagram showing an example of an optical disc recording device according to the present invention. LD is a laser diode, PD is a bin diode, (5
) is the driver, (11) is the reference voltage VREF selection circuit, (15) is the loop filter, (2
1) is a time constant circuit, (22) is a same speed charging/discharging means, (23
) is a changeover switch. Same Hidemori Matsukuma 1i5. 'lS,',': et al. 1%. 9.,; Figure 1 Figure 2

Claims (1)

[Claims] In an optical disc recording device using a data writable disc, a loop filter is provided in an automatic power control loop that controls the radar power irradiated to the disc to predetermined values respectively when reading and writing data, 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, and at least when switching the data write mode, the above-mentioned capacitor is An optical disc recording device in which a loop time constant at the time of mode switching is reduced by charging.