JPH0636501Y2 - Recordable optical disk recording / reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a recording / reproducing apparatus for a recordable optical disc, and
Laser light mainly emitted from a single semiconductor laser onto an optical disc capable of recording information in which an area in which address information is recorded and a recording area following the area in which this address information is recorded are alternately arranged. The present invention relates to a recording / reproducing apparatus for a recordable optical disc which irradiates with light and continuously records and / or reproduces information while reading the address information recorded on the optical disc. Then, it is possible to prevent an unnecessary response to a recording signal and other noises, and to quickly switch the amount of light generated by the semiconductor laser, which is a recording / reproducing light source, when the mode is switched between the recording mode and the reproducing mode. The present invention intends to provide a new recordable optical disc recording / reproducing apparatus capable of performing the above-mentioned operation.

BACKGROUND ART A semiconductor laser is used as a light source in a recording / reproducing apparatus for a recordable optical disc, regardless of whether it is a one-time recording type called DRAW or a rewritable type by magneto-optical recording. ing. As shown in FIG. 4, the semiconductor laser has a temperature-dependent current / output characteristic, and the optical output varies depending on the temperature. Therefore, the semiconductor laser used as a light source in the optical disk device cannot be driven by a simple method of supplying a constant direct current to it, and generally, a PIN diode for light detection is arranged close to the semiconductor laser, and the PIN diode is used. The semiconductor laser is driven by a semiconductor laser drive circuit that keeps the optical output level constant in accordance with the level of the optical output detected by. FIG. 5 shows an example of a semiconductor laser drive circuit of a conventional recording / reproducing apparatus for a recordable optical disc.

In the figure, LD is a semiconductor laser (laser diode)
, Its anode is grounded and its cathode is capacitor C1
And a recording signal input terminal via a resistor R1. Also, the cathode of the semiconductor laser LD is connected to PN via the resistor R2.
It is connected to the collector of the P-type drive transistor Q. The emitter of the transistor Q is connected to the negative power supply terminal that receives the negative voltage -Va.

PD is a PIN diode, which is housed in the same package as the semiconductor laser LD and detects the optical output of the semiconductor laser LD, and operates by receiving a reverse bias. Its cathode is grounded and its anode is connected to the minus power supply terminal via a resistor R3. A minus voltage −Vb is applied to the minus power supply terminal. A1 is an operational amplifier that amplifies the terminal voltage of the resistor R3. Its inverting input terminal is connected to the connection point between the resistor R3 and the minus power supply terminal via the resistor R4, and the non-inverting input terminal is connected via the resistor R5. It is connected to the connection point between R3 and the PIN diode PD and is also grounded via a resistor R6. R7 is a resistor for negative feedback connected between the output terminal and the inverting input terminal of the operational amplifier A1.

Then, when the photocurrent Ip corresponding to the light output of the semiconductor laser LD flows through the PIN diode PD, a voltage drop occurs due to the resistor R3, and the voltage drop is amplified by the operational amplifier A1. Therefore, the output terminal of the operational amplifier A1 is The level corresponds to the optical output of the semiconductor laser LD.

A2 is an operational amplifier that amplifies the output voltage of the operational amplifier A1, receives the output voltage of the operational amplifier A1 at the inverting input terminal via the resistor R8, the non-inverting input terminal is grounded via the resistor R9, and Between the inverting input terminal and the output terminal, a resistor R10 and a capacitor C2 that are connected in parallel with each other and configure a low pass filter LPF are connected. The output terminal of the operational amplifier A2 is connected to the base of the drive transistor Q via a resistor R11. The emitter of the transistor Q is connected to a negative power supply terminal to which a negative voltage -Va is applied, and the collector is a semiconductor laser via a resistor R2.
It is connected to the LD cathode as described above.

One end of R12 is a resistor connected to the inverting input terminal of the operational amplifier A2, and the other end receives the optical output switching voltage −Vpsw. The optical output switching voltage -Vpsw is for switching the optical output level of the semiconductor laser LD, and lowers the optical output level when the recordable optical disc recording / reproducing apparatus is in the reproducing mode, and the optical output level when it is in the recording mode. Since it is necessary to raise the level, a negative optical output switching voltage −Vpsw is applied to the inverting input terminal of the operational amplifier A2, and the drive current I1d of the semiconductor laser LD is switched by switching the level, thereby changing the level of the semiconductor laser LD. The light output level is switched.

The operation of this semiconductor laser drive circuit will be described below. When a negative optical output switching voltage -Vpsw of a certain level is applied to the inverting input terminal of the operational amplifier A2, the output voltage of the operational amplifier A2 becomes positive and the transistor Q is turned on. Then, the drive current I1d flows through the semiconductor laser LD, and when the drive current I1d exceeds the threshold current Ith of the semiconductor laser LD, the semiconductor laser LD emits light. The optical output of the semiconductor laser LD is detected by the PIN diode PD, converted into a voltage by the resistor R3 and the operation amplifier A1, and applied to the inverting input terminal of the operational amplifier A2. Then, this semiconductor laser drive circuit
The optical output of the semiconductor laser LD is negatively fed back to the operational amplifier A2 that drives the semiconductor laser LD via the drive transistor Q, and a closed loop light amount control system referred to in automatic control engineering is configured. Therefore, when the optical output of the semiconductor laser LD is too weak, the output voltage of the operational amplifier A2 is increased, so that the drive current I1d of the semiconductor laser LD is increased.
Is increased and the optical output of the semiconductor laser LD is intensified, and when the optical output is too high, the output voltage of the operational amplifier A2 is decreased, so the drive current of the semiconductor laser LD is decreased, and in turn the semiconductor laser LD is increased. The light output of the LD is weakened. Therefore, the optical output of the semiconductor laser LD is kept constant.

Then, the optical output level of the semiconductor laser LD can be switched by switching the level of the optical output switching voltage −Vpsw. Specifically, the optical output level can be increased by lowering the level of the optical output switching voltage −Vpsw. Therefore, in the playback mode, the optical output switching voltage-
The level of Vpsw may be raised, and in the recording mode, the level of the optical output switching voltage −Vpsw may be lowered.

Also, in the recording mode, the recording signal Srec changes the semiconductor laser LD
Drive current I1d of the semiconductor laser LD applied to the cathode of
Are modulated by the recording signal Srec. Therefore, the optical output of the semiconductor laser LD is modulated by the recording signal Srec.

By the way, such a semiconductor laser drive circuit is set so that the frequency band of the light quantity control system becomes low, and
The low-pass filter LPF composed of R10 and the capacitor C2 is provided to lower the frequency band. For example, the capacitance of the capacitor C2 is increased to increase the time constant of the low-pass filter LPF to narrow the frequency band. be able to. This is done firstly to prevent the light amount control system of the semiconductor laser drive circuit from responding to the recording signal Srec. That is, since the optical output of the semiconductor laser LD is modulated by the recording signal Srec in the recording mode, the detection signal of the PIN diode PD naturally changes according to the recording signal Srec. Therefore, the above low-pass filter
The LPF is provided to lower the frequency band of the light quantity control system, in other words, the response is lowered, and the drive current I1d supplied from the drive transistor Q and used for modulation by the recording signal Srec is changed by the recording signal Srec. To prevent it.

The second reason is that a part of the laser light projected from the semiconductor laser LD is fed back to the semiconductor laser LD or the PIN diode PD to generate a drive current I1 of the semiconductor laser LD.
This is to prevent the fluctuation of d. This is because the laser light projected from the semiconductor laser LD is a beam splitter, part of which constitutes the pickup of the optical disk device.
It is reflected by an optical element such as a collimator lens and is returned to the semiconductor laser LD to change its optical output or enter the PIN diode PD. As a result, the PIN diode P
The D detection signal also fluctuates, which causes a fluctuation in the drive current I1d of the semiconductor laser LD. Especially in the case of a non-polarized optical system, a considerable amount of the return light reflected by the optical disk is a semiconductor laser.
Since it returns to the LD, it is necessary to prevent it from being affected by the returning light.

However, as described above, when the frequency band of the semiconductor laser drive circuit is lowered, it becomes impossible to quickly perform the mode switching from the recording mode to the reproducing mode and from the reproducing mode to the recording mode. There's a problem. This is because the level of the optical output of the semiconductor laser LD must be switched when switching the mode, but as described above, the switching is performed by connecting the resistance to the inverting input terminal of the operational amplifier A2.
This is done by changing the level of the optical output switching voltage −Vpsw applied via R12. Since the frequency band of the light quantity control system is set to the low band as described above, the semiconductor laser LD is naturally used after switching the level of the optical output switching voltage -Vpsw.
It takes a long time before the level of the optical output of is switched to a predetermined value. And, this cannot be ignored in a recordable optical disk device. In general, an optical disc on which information is to be recorded is provided with a plurality of fan-shaped recording areas and recording areas such as addresses located between adjacent recording areas.
Then, the address and the like are recorded in advance in the address and the like recording area, and the information such as the address and the like recorded therein is read out and then the information is recorded at the designated address in the recording area.

Therefore, when recording on an optical disc that rotates at a high speed, it is necessary to frequently repeat the mode switching from the reproduction mode to the recording mode and from the recording mode to the reproduction mode, and the optical output of the semiconductor laser LD is changed according to the mode switching. The inability to quickly switch the level of 1 results in the necessity of narrowing the width of each recording area of the disc rotating at high speed.

SUMMARY OF THE INVENTION Therefore, the present invention can prevent unnecessary response to a recording signal and other noises and can quickly switch the amount of light generated by a semiconductor laser when switching between a recording mode and a reproducing mode. Another object of the present invention is to provide a recording / reproducing apparatus for a new recordable optical disc that can be used in the above.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical disc capable of recording information in which an area in which address information is recorded and a recording area following the area in which the address information is recorded are alternately arranged. A recording / reproducing apparatus for a recordable optical disc, which irradiates a laser beam emitted from a single semiconductor laser to continuously record and / or reproduce the address information recorded on the optical disc. A photodiode for receiving a laser beam emitted from the semiconductor laser, a first capacitor, and a capacitor having a capacitance sufficiently larger than that of the capacitor and connected in parallel to the first capacitor. A low-pass filter having a second capacitor, a resistor connected in parallel to the first and second capacitors, and the first capacitor On the other hand, the semiconductor laser has a switch circuit arranged between the first capacitor and the second capacitor to open the connection of the second capacitor, and the semiconductor laser is output based on the output signal from the photodiode. A semiconductor laser drive circuit that drives the semiconductor laser so that the amount of emitted laser light is constant, a recording circuit that supplies a drive signal based on a recording signal to the semiconductor laser, and recording and reproduction modes. An output level setting unit that supplies a signal for setting the output level of the amount of light emitted from the semiconductor laser to the semiconductor laser drive circuit, and the semiconductor laser from the output level setting unit based on each mode of recording and reproduction. The output level setting section is controlled so as to selectively switch the signal supplied to the drive circuit, and each mode between recording and reproduction is controlled. A controller for controlling to open the switch circuit when de switching, and characterized in that it comprises a.

Embodiment Hereinafter, a recording / reproducing apparatus for a recordable optical disc according to the present invention will be described in detail according to an embodiment shown in the accompanying drawings.

1 to 3 are for explaining an example of an embodiment of a recording / reproducing apparatus for a recordable optical disc according to the present invention, and FIG. 1 shows a circuit configuration thereof.

In the figure, reference numeral 1 is a system controller (controller) for controlling the entire optical disk apparatus, which is composed of a microcomputer. When an operation key or the like is operated on the operation unit of the optical disk device 2, the signal 2 indicates the operation content to the system controller 1. Reference numeral 3 denotes a data reading circuit for reading information recorded on the optical disk through a pickup (not shown). The reading by the data reading circuit 3 is necessary for reading data to be reproduced by a reproducing unit 4 such as a display or a printer and for recording. There is reading of data such as the address. The latter reading is performed in the reproduction mode during the operation of recording information on the optical disc.

A recording circuit 5 receives the data input from the data input unit 6 through the system controller 1 and sends a recording signal Srec for modulating laser light generated by a semiconductor laser described later to a semiconductor laser drive circuit described later. Reference numeral 7 denotes a light quantity switching voltage generating circuit, which generates a negative light output switching voltage -Vpsw based on a command from the system controller 1. Specifically, a small absolute value (high level) optical output switching voltage −Vpsw is generated in the playback mode, and a large absolute value (low level) optical output switching voltage −Vpsw is generated in the recording mode. Occur.

Reference numeral 8 denotes a semiconductor laser drive circuit, which is provided with a capacitor C3 (second capacitor) and a switch circuit SW, which is different from the semiconductor laser drive circuit of the conventional recordable optical disk recording / reproducing apparatus shown in FIG. It is different in that it is common in other points. Therefore, in the semiconductor laser drive circuit 8, the same parts as those of the circuit shown in FIG. 5 are designated by the same reference numerals as those shown in FIG. 5, and the description of the common part is omitted in the explanation of the circuit configuration. To do.

The capacitor C2 that is also present in the semiconductor laser drive circuit shown in FIG. 5 corresponds to the first capacitor referred to in the utility model registration claim of this specification, and the capacitor C3 is referred to in the utility model registration claim. The second capacitor C3 has one end connected to the output terminal of the operational amplifier A2 and the other end connected to the common terminal of the switch circuit SW. The normally closed terminal of the switch circuit SW is connected to the inverting input terminal of the operational amplifier A2, and the normally open terminal is grounded. The switch circuit SW is switched by the time constant switching signal Stc from the system controller 1. And the first capacitor
While C2 has a relatively small capacitance, the capacitance of the second capacitor C3 is set to a value that is, for example, 100 times as large as that of the first capacitor C2, and normally, the capacitance of the capacitor C3 is changed via the switch circuit SW. Is connected in parallel with the capacitor C2, the low-pass filter LPF provided between the output terminal and the inverting input terminal of the operational amplifier A2
Has a large time constant.

Then, when the switch circuit SW is switched to the state in which the common terminal and the normally open terminal are connected by the time constant switching signal Stc, the second capacitor C3 is disconnected from the inverting input terminal of the operational amplifier A2 and is grounded. Become. Therefore, at this time, the second capacitor C3 having a large capacitance does not constitute the low-pass filter LPF, and the time constant of the low-pass filter LPF becomes small. Also, the second
One end of the capacitor C3 is an operational amplifier A2
Is always connected to the output terminal of, and the other end is grounded via the switch circuit SW, so that necessary charging / discharging is performed at that time.

The time constant of the low-pass filter LPF generally determines the frequency characteristic of the light quantity control system of the semiconductor laser drive circuit 8, and when the time constant of the low-pass filter LPF is large, that is, the second
When the capacitor C3 of 4 forms a part of the low-pass filter LPF, the frequency characteristic becomes as shown by the solid line in FIG. On the contrary, when the time constant is small, that is, when the second capacitor C3 is separated from the low pass filter LPF, the frequency identification becomes as shown by the broken line in FIG. In this figure, the horizontal axis represents frequency and the vertical axis represents system gain.

FIG. 3 is a timing chart for explaining the operation of the semiconductor laser drive circuit 8, and the operation of the semiconductor laser drive circuit will be described according to this.

(1) In the reproduction mode, the negative optical output switching voltage -Vpsw is at a high level (small absolute value), and therefore the drive current I1d of the semiconductor laser LD is at a low reproduction level. Of course, in the reproduction mode, since the recording signal Srec is not generated, the drive current I1d is not modulated by the recording signal Srec. Further, the time constant switching signal Stc for switching the switch circuit SW is kept "low", so the capacitor C3
Is a part of the low-pass filter LPF, and the frequency characteristic of the light quantity adjusting system is the characteristic shown by the solid line in FIG.

(2) When switching from playback mode to recording mode (time point
t1), a switching command to that effect is transmitted from the system controller 1 to the light amount switching voltage generation circuit 7, and the light amount switching voltage generation circuit 7 lowers the level of the optical output switching voltage -Vpsw being generated (absolute). Increase the value). Therefore, the semiconductor laser
Driving current I1 flowing through LD, resistor R2 and driving transistor Q
d is in a state of trying to rise from a low reproduction level to a recording level considerably higher than that.

By the way, when the reproduction mode is switched to the recording mode, the level of the optical output switching voltage −Vpsw is switched and the time constant switching signal Stc is sent from the system controller 1 to the switch circuit SW.
Is transmitted, and the common terminal of the switch circuit SW is connected to the normally open terminal. Therefore, the time constant of the low-pass filter LPF becomes a small value, the frequency characteristic of the light amount control system becomes the state shown by the broken line in FIG. 2, and the response becomes high,
The current from the reproducing level where the drive current I1d is low to the recording level rises extremely quickly. Then, after reaching the recording level, the time constant switching signal Stc falls. Let that time be t2. As a result, the frequency characteristic of the light quantity control system is as shown by the solid line in FIG. 2, and the response is low.

Then, immediately after that, the transmission of the recording signal Srec from the recording circuit 5 to the semiconductor laser driving circuit 8 is started. As a result, the recording level drive current I1d supplied from the light amount control system to the semiconductor laser LD is modulated by the recording signal Srec. Therefore, the laser light generated from the semiconductor laser LD is modulated by the recording signal Srec to become strong light or weak light.

By the way, when the amount of laser light generated from the semiconductor laser LD changes, the photocurrent Ip flowing through the PIN diode PD is naturally
Also changes according to the recording signal Srec and also due to the return of other return light, etc.
The LPF has a large time constant and the frequency characteristics are those shown by the solid line in Fig. 2. Since it cannot respond to noise with high frequency components, it is supplied from the light quantity control system affected by the recording signal Srec. The level of the drive current I1d (recording level) does not change.

(3) When the mode is switched from the recording mode to the reproduction mode (time point t3), the output of the recording signal Srec of the recording circuit 5 is stopped, the level of the optical output switching voltage −Vpsw is increased, and the drive current I1d is reproduced. Tries to be lowered. Then, since the time constant switching signal Stc is input at the same time as the mode switching, the time constant of the low-pass filter LPF is reduced, the frequency characteristic of the light quantity control system becomes the state shown by the broken line in FIG. 2, and the response is improved. . Therefore, the rate of decrease of the drive current I1d from the recording level to the reproduction level becomes very fast, and the drive current I1d quickly reaches the reproduction level.

(4) When the drive current I1d drops to the reproduction level, the time constant switching signal Stc then falls and the frequency characteristic of the light quantity control system returns to the characteristic shown by the solid line in FIG. Therefore,
It is also possible to prevent fluctuations in the drive current I1d due to noise generated during reproduction.

The above-mentioned operation is repeated during the recording operation. Then, each time the mode is switched from the reproduction mode to the recording mode and from the recording mode to the reproduction mode, the responsiveness of the light amount control system during the switching period is enhanced, so that the drive current I1d is switched when the mode is switched. Is done quickly. The responsiveness of the light amount control system is reduced except when the mode is switched, so that the drive current I1d can be prevented from fluctuating due to various noises generated during the recording mode or the reproducing mode.

Effect of the Invention As described above, the recording / reproducing apparatus for a recordable optical disk according to the present invention comprises the area in which the address information is recorded and the recording area following the area in which the address information is recorded, arranged alternately. Recording for irradiating an optical disk capable of recording information with laser light mainly emitted from a single semiconductor laser, and recording and / or reproducing information continuously after reading address information recorded on the optical disk. A possible optical disc recording / reproducing apparatus, which has a photodiode for receiving laser light emitted from the semiconductor laser, a first capacitor, and a capacitance sufficiently larger than the capacitance of the capacitor. A low pass filter having a second capacitor connected in parallel to one capacitor and a resistor connected in parallel to these first and second capacitors. A filter and a switch circuit arranged between the first capacitor and the second capacitor to open the connection of the second capacitor to the first capacitor, and an output from the photodiode. A semiconductor laser driving circuit that drives the semiconductor laser so that the amount of laser light emitted from the semiconductor laser based on a signal becomes constant; and a recording circuit that supplies a driving signal based on a recording signal to the semiconductor laser, An output level setting unit that supplies a signal for setting the output level of the light quantity emitted from the semiconductor laser in each of the recording and reproducing modes to the semiconductor laser drive circuit, and the above-mentioned based on each of the recording and reproducing modes. The output level setting unit is controlled so as to selectively switch the signal supplied from the output level setting unit to the semiconductor laser drive circuit. As well as, those that characterized in that it comprises a controller for controlling to open the switch circuit when switching modes between a recording reproduction.

Therefore, according to the recording / reproducing apparatus for a recordable optical disc of the present invention, it is possible to prevent an unnecessary response to a recording signal and other noises, and at the same time, to change the optical output at the time of mode switching between the recording mode and the reproducing mode. Switching can be performed quickly.

Therefore, the information recording area of the optical disc can be effectively utilized, and the conventional problem that the information recording area of the optical disc becomes narrow can be avoided.

[Brief description of drawings]

1 to 3 are for explaining an example of an embodiment of a recording / reproducing apparatus for a recordable optical disk according to the present invention. FIG. 1 is a circuit configuration diagram and FIG. 2 is a frequency characteristic diagram of a semiconductor laser drive circuit. FIG. 3 is a timing chart for explaining the operation of the semiconductor laser drive circuit, FIG. 4 is a characteristic diagram showing the temperature dependence of the drive current / optical output characteristic of the semiconductor laser, and FIG. 5 is a conventional recordable optical disc. It is a circuit diagram showing an example of a semiconductor laser drive circuit of the recording and reproducing apparatus. Explanation of code LD …… semiconductor laser, PD …… photodiode, SW …… switch circuit, C2 …… first capacitor, C3 …… second capacitor, R10 …… resistor, 1 …… controller, 5 …… Recording circuit, 7 ... Output level setting section (light quantity switching voltage generating section), 8 ... Semiconductor laser drive circuit.

Claims (1)

[Scope of utility model registration request] 1. A single semiconductor laser emits light to an optical disc capable of recording information in which an area in which address information is recorded and a recording area following the area in which the address information is recorded are alternately arranged. Is a recording / reproducing apparatus for a recordable optical disc which irradiates a laser beam to be recorded and which records and / or reproduces information continuously while reading the address information recorded on the optical disc, and is emitted from the semiconductor laser. A photodiode for receiving laser light, a first capacitor, a second capacitor having a capacitance sufficiently larger than the capacitance of the capacitor and connected in parallel to the first capacitor, and A low-pass filter having a resistor connected in parallel to the first and second capacitors, and a second capacitor for the first capacitor. A switch circuit arranged between the first capacitor and the second capacitor to open the connection of the laser light emitted from the semiconductor laser based on the output signal from the photodiode. A semiconductor laser drive circuit that drives the semiconductor laser so that the amount of light is constant, a recording circuit that supplies a drive signal based on a recording signal to the semiconductor laser, and a laser beam is emitted from the semiconductor laser in each of recording and reproducing modes. An output level setting section for supplying a signal for setting the output level of the light amount to the semiconductor laser driving circuit, and a signal for supplying the semiconductor laser driving circuit from the output level setting section based on each mode of recording and reproduction. The output level setting section is controlled so as to selectively switch signals, and the above A recording / reproducing apparatus for a recordable optical disc, comprising: a controller for controlling the switch circuit to open.