JPH0870152A - Semiconductor laser driver device - Google Patents

Abstract

PURPOSE: To positively record data by making flat the frequency characteristics within the frequency band of a write data pattern. CONSTITUTION: At the time of reproduction the control voltage from a CPU 1 is applied to a high-frequency oscillation circuit 8 and a high frequency is superposed on current for recording and the current is supplied to a semiconductor laser LD1. At the time of recording, no control voltage is applied from the CPU l to the high-frequency oscillation circuit 8 and the circuit 8 is turned off. Then, by setting series resonance frequency outside the frequency band of write data pattern on recording, current for recording can be supplied to the semiconductor laser LD1 without being affected by the series resonance frequency of the LC (a coil 13 and capacitors C2, C4-C6, and C8) of the high-frequency oscillation circuit 8 and the series resonance frequency due to an LC filter at a reproduction side, thus positively recording data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser driving device having a high frequency oscillation circuit for reducing noise emitted from a semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, in an optical information recording / reproducing apparatus having a semiconductor laser driving device, a semiconductor laser (Las
A high frequency oscillation circuit is provided in order to reduce the noise of the laser light emitted by the laser diode (LD). This high-frequency oscillator circuit is intended to reduce noise of laser light emitted by the semiconductor laser by superposing a high-frequency current on a direct current applied to the semiconductor laser. Therefore, in the optical information recording / reproducing device having the semiconductor laser driving device, it is necessary to electrically connect the semiconductor laser and the high frequency oscillation circuit.

For example, Japanese Unexamined Patent Publication (Kokai) No. 63-44782 discloses a semiconductor laser driving device in which an oscillation circuit for high frequency superimposition and an electric negative feedback circuit are packaged in a single package. A circuit for preventing unnecessary radiation associated with is provided.

That is, in the semiconductor laser driving device disclosed in Japanese Patent Laid-Open No. 63-44782, as shown in FIG.
The gallium-arsenic integrated circuit 101 for high frequency superimposition and the silicon integrated circuit 102 for electrical negative feedback are wired on a printed circuit board to form a hybrid integrated circuit housed in a shield case 103.

Voltages of positive and negative 5 V are supplied to the high frequency superimposing gallium arsenide integrated circuit 101 and the electrically negative feedback silicon integrated circuit 102 through feedthrough capacitors 104 and 105. The output of the gallium arsenide integrated circuit 101 for high frequency superposition is supplied to the semiconductor laser 108 via the load coil 106 and the coupling capacitor 107.

[0006] The silicon integrated circuit 10 for electrical negative feedback described above.
The anode of a PIN photodiode 109 provided outside the shield case 103 is connected to the input part 2 of the above, and the cathode of the semiconductor laser 108 is connected to the output part of the silicon integrated circuit 102 for negative electrical feedback. There is. Further, a gain adjusting volume 110 of a feedback system is connected to the electrically negative feedback silicon integrated circuit 102.

Further, the semiconductor laser 108 has an LC filter 111 composed of a coil (L) and a capacitor (C).
Also, it can be driven from the outside through the feedthrough capacitor 112. The built-in PIN photodiode 113 can also be connected to the outside through the feedthrough capacitor 114.

Therefore, in the conventional example shown in FIG. 5, a high frequency current is superposed on a direct current applied to the semiconductor laser 108 by the high frequency superimposing gallium arsenide integrated circuit 101, so that the laser emitted from the semiconductor laser 108 is irradiated. The noise of light is reduced and the LC filter 111 prevents leakage of unnecessary radiation due to the high frequency current.

However, in the above-mentioned conventional example, when the semiconductor laser 108 is subjected to high-speed modulation, if the LC filter 111 is connected to the line of the current applied to the semiconductor laser 108, the semiconductor laser output during recording is increased. The upper limit of the modulation speed and the rising and falling speeds of the recording pulse are limited.

Therefore, a device shown in FIG. 6 can be considered as a means for solving such a drawback. That is, as shown in FIG. 6, the semiconductor laser 121 is a light source of an optical head (not shown) and is driven in a reproduction mode, a recording mode, and an erasing mode, which will be described later. The semiconductor laser 121 includes an oscillator circuit for high frequency superposition (hereinafter abbreviated as high frequency oscillator circuit) 122 and an unnecessary radiation prevention circuit 1.
It is housed in a shield case 124 together with 23 and the like.

The high frequency oscillating circuit 122 is driven only during reproduction, and has a function of reducing noise of laser light emitted from the semiconductor laser 121 during reproduction.
The semiconductor laser 121 is provided with a feedthrough capacitor 125 and a coil 126, which form an unnecessary radiation prevention circuit 123,
It is driven by a reproducing semiconductor laser drive circuit (hereinafter abbreviated as an R LD driver) 127. The drive mode at this time is the reproduction mode. In addition, the semiconductor laser 121
Is a semiconductor laser drive circuit for recording (hereinafter, referred to as a semiconductor laser drive circuit) via a feedthrough capacitor 128 and a switching diode 129.
It is driven by an LD driver 130 for W). The drive mode at this time is the recording mode.

Further, one end of the coil 126 and the cathode of the switching diode 129 are connected to the anode of the semiconductor laser 121, and the semiconductor laser 1 is also connected.
The cathode of 21 is connected to the reference potential point (GND) through the shield case 124.

Further, the high frequency oscillation circuit 122 is connected to a power source for the high frequency oscillation circuit 122, for example, +5 V, through a coil 131 and a feedthrough capacitor 132 which constitute the unnecessary radiation prevention circuit 123. The high frequency oscillation circuit 122 includes a transistor 140, coils 141 and 142, and capacitors 143-147, as shown in FIG.
It is composed of resistors 148 and 149.

The high frequency oscillation circuit 122 superimposes a high frequency current on the semiconductor laser 121 via a coupling capacitor 147. Further, the high frequency oscillation circuit 122 includes a coil 133 and a feedthrough capacitor 13 which form the unnecessary radiation prevention circuit 123.
CPU (Central Processing Unit;
It is connected to the CPU) 135, and the on / off of its driving is controlled by the control voltage from the CPU 135.

The feedthrough capacitors 125 and 12 are also provided.
The reference numerals 8, 132, and 134 penetrate the shield case 124 and are fixed. In addition, the high frequency current is transmitted to the coils 126, 131 and 133 and the feedthrough capacitors 125 and 1.
The LC filter composed of 32 and 134 prevents radiation to the outside of the shield case 124. Due to such superposition of the high-frequency current, the semiconductor laser 121 is not affected by the optical system of the optical head and emits light stably and at a low noise level.

The recording semiconductor laser drive circuit 1 is also provided.
A switch 136 is connected between the intermediate connection point of 30 and the feedthrough capacitor 128 and the reference potential point, and ON / OFF of the switch 136 is controlled by a control signal from the CPU 135. Further, the reproducing semiconductor laser driving circuit 127 and the recording semiconductor laser driving circuit 130 are respectively controlled by the reproducing control circuit 137 and the recording control circuit 138 controlled by the CPU 135. Further, the recording control circuit 138 includes
An information signal for recording is given from the CPU 135, and a modulation signal is added.

Accordingly, FIG. 6 configured as described above.
Since the high frequency superimposed current is not superposed at the time of recording in the semiconductor laser driving device shown in FIG. 6, it is not necessary to insert an LC filter for preventing unnecessary radiation in the recording current line, and high-speed modulation can be given to the semiconductor laser 121. it can.

[0018]

However, in general, in the semiconductor laser driving device shown in FIG. 6, when the frequency characteristic of the current applied to the semiconductor laser 121 during recording is changed, the coils 141, 14 of the high frequency oscillation circuit 122 are changed.
2 and series resonance frequency f due to the capacitor 147
1 ', f2' and the coil 12 of the LC filter on the reproducing side
6, series resonance frequency f3 'by feedthrough capacitor 125
At, a valley of gain occurs due to a decrease in impedance as shown in FIG.

Therefore, the frequency band of the write data pattern at the time of recording in the semiconductor laser driving device shown in FIG. 6 is set to flow 'to fhigh'. Here, as shown in FIG. 8, the series resonance frequency f1 ′ of the above-mentioned gain valley,
When f2 'and f3' are in the frequency band of flow 'to fhigh', that is, when they overlap with the frequency band of flow data'flow 'to fhigh' of the write data pattern, the recording current waveform supplied to the semiconductor laser 121 is It gets disturbed. For this reason, the semiconductor laser 121 does not emit laser light for accurate recording, and as a result, the semiconductor laser drive device shown in FIG. 6 has a problem that normal recording operation may not be performed. .

Therefore, the present invention has been made in view of the above problems, and a semiconductor laser drive capable of performing a reliable recording operation by improving the frequency characteristic of the current applied to the semiconductor laser during recording. The purpose is to provide a device.

[0021]

In order to achieve the above object, a semiconductor laser driving device of the present invention comprises a semiconductor laser for supplying a recording laser beam and a reproducing laser beam for irradiating an optical recording medium, and the above recording. A recording line for supplying a recording drive signal for irradiating the semiconductor laser beam to the semiconductor laser, and a reproducing line for supplying a reproduction drive signal for irradiating the reproducing laser beam to the semiconductor laser,
A high frequency superposed oscillation means for superimposing a high frequency signal on the reproduction drive signal to reduce laser noise of the reproduction laser light supplied from the semiconductor laser; and a high frequency superposed oscillation means provided on the reproduction line. A semiconductor laser driving device comprising an unnecessary radiation preventing means for preventing unnecessary radiation accompanying driving, and a shield means for accommodating the semiconductor laser and the high frequency superposed oscillation means, wherein the unnecessary radiation preventing seen from the recording line. And a band in which the impedance of the means and the high-frequency superposed oscillating means decreases is set outside the band of the recording drive signal.

[0022]

In the semiconductor laser driving device of the present invention, the recording laser light and the reproducing laser light for irradiating the optical recording medium are supplied by the semiconductor laser, and the recording drive signal for irradiating the recording laser light is recorded. And a reproducing drive signal for irradiating the reproducing laser beam is supplied to the semiconductor laser through the reproducing line. Further, the high frequency superposing and oscillating means superimposes a high frequency signal on the reproducing drive signal, and the laser noise of the reproducing laser light supplied from the semiconductor laser is reduced. Further, the unnecessary radiation accompanying the driving of the high frequency superposed oscillation means is provided in the reproduction line and is prevented by the unnecessary radiation prevention means, and the semiconductor laser and the high frequency superposed oscillation means are housed by the shield means. Then, the band in which the impedances of the unwanted radiation prevention means and the high frequency superposed oscillation means are reduced when viewed from the recording line is set outside the band of the recording drive signal.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a semiconductor laser driving device according to the first embodiment of the present invention.

In this semiconductor laser driving device, CP
U1 is connected to the base of the transistor Q1 via the feedthrough capacitor C1 and the coil L1, and is also connected to one end of the capacitor C2.
The other end of 2 is connected to the reference potential point (GN
D).

Further, the CPU 1 is connected to a reproducing semiconductor laser drive circuit (R LD driver) 4 via a reproducing control circuit (R control circuit) 3, and the reproducing semiconductor laser drive circuit 4 is penetrated. The capacitor C3 is connected to one end of a capacitor C4 via a coil L2, and is connected to the anode of the semiconductor laser LD1 and the cathode of the switching diode D1. Further, the cathode of the semiconductor laser LD1 is connected via the shield case 2. And is connected to the reference potential point.

Further, the other end of the capacitor C4 is connected in parallel to one end of the coil L4, one end of the capacitor C5, one end of the resistor R1 and the collector of the transistor Q1 via the coil L3. Furthermore, the capacitor C
The other end of 5 is connected in parallel to one end of the capacitor C6, the emitter of the transistor Q1 and one end of the resistor R2. Further, the other end of the capacitor C6 and the resistor R2
The other end of is connected to the reference potential point via the shield case 2.

Further, the CPU 1 is connected to a recording semiconductor laser drive circuit (W LD driver) 6 via a recording control circuit (W control circuit) 5, and the recording semiconductor laser drive circuit 6 is further penetrated. It is connected to the anode of the switching diode D1 via the capacitor C7 and is also connected to one end of the switch 7.

Further, a control signal line is connected from the CPU 1 to the control end of the switch 7, and the other end of the switch 7 is connected to the reference potential point. A recording information signal line is connected from the CPU 1 to the recording control circuit 5.

Further, the other end of the resistor R1, the other end of the coil L4, and the capacitor C whose one end is connected to the reference voltage point.
The other end of 8 has a coil L5 and a feedthrough capacitor C9.
Is connected to a voltage source (+ 5V). Also,
The shield case 2 is connected to the reference potential point.

Further, the transistor Q1 and the resistors R1 and R
2, the capacitors C2, C4, C5, C6, C8 and the coils L3, L4 constitute a high frequency oscillation circuit 8, and the CPU 1
By controlling the base voltage of the transistor Q1 by the control voltage from the high frequency oscillation circuit 8
ON / OFF control.

Further, the feedthrough capacitors C1, C3, C
7, C9 are fixed by penetrating the shield case 2. The high frequency current from the high frequency oscillation circuit 8 is applied to the coils L1, L2 and L5 and the feedthrough capacitor C1.
The unnecessary radiation prevention circuit 9 of the LC filter composed of C3 and C9 prevents the radiation to the outside of the shield case 2.

At this time, the semiconductor laser L at the time of recording
The frequency characteristic of the recording current supplied to D1 has three troughs at the series resonance frequencies f1, f2, and f3. Of these, the series resonance frequencies f1 and f2 are series resonance frequencies due to the LC of the high frequency oscillation circuit 8, and the series resonance frequency f3 is a series resonance frequency due to the coil L2 and the capacitor C3 which are LC filters on the reproducing side. is there.

Here, the series resonance frequency f1 is equal to the coil L
3 and L4, and the series resonance frequency of the capacitor C4, which is expressed by the following equation. f1 = 1 / [2π {(L3 + L4) C4} ^1/2 ] (1) Further, the series resonance frequency f2 is equal to the coil L4 and the capacitor C.
It is a series resonance frequency of 4, C5 and C6 and is represented by the following equation.

F2 = 1 / {2π (L4 · C0) ^1/2 } (2) where C0 # C4 · C5 · C6 / (C5 · C6 + C4 ·
C5 + C4 / C5 / C6) Further, the series resonance frequency f3 is L on the reproducing side as described above.
It is a series resonance frequency due to the coil L2, which is a C filter, and the capacitor C3, and is expressed by the following equation.

F3 = 1 / {2π (L2 · C3) ^1/2 } (3) Therefore, when the frequency band of the write data pattern at the time of recording in the semiconductor laser driving device of the first embodiment is set to flow to fhigh, the series resonance frequencies f1, f2, and f3 become the write data pattern as shown in FIG. It is configured to be outside the frequency band from low to high. That is, the series resonance frequencies f1, f2, f3
Is set out of the frequency band from flow to fhigh of the write data pattern by the above equations (1), (2) and (3).

The series resonance frequencies f1, f2, f
The setting of 3 may be automatically changed by the setting means 10 during the operation of the semiconductor laser driving device.
In the semiconductor laser driving device of the first embodiment having the above-described structure, the high frequency oscillation circuit 8 is used during reproduction.
A control voltage is applied from the CPU 1 to the semiconductor laser LD1 with a high frequency superimposed on the recording current.

On the other hand, during recording, the high frequency oscillation circuit 8
The control voltage from the CPU 1 is not applied to the high frequency oscillation circuit 8 and the high frequency oscillation circuit 8 is turned off. Then, by setting the series resonance frequencies f1, f2, and f3 outside the frequency band from low to fhigh of the write data pattern at the time of recording, the series resonance frequency f of the LC of the high frequency oscillation circuit 8 is set.
The recording current is supplied to the semiconductor laser LD1 without being affected by the series resonance frequency f3 of the LC filters 1 and f2 and the reproducing side LC filter.

As described above, according to the semiconductor laser driving device of the first embodiment, the recording operation can be surely performed by flattening the characteristics in the frequency band of the write data pattern.

Next, a second embodiment according to the present invention will be described. FIG. 3 is a circuit diagram showing the configuration of the semiconductor laser driving device of the second embodiment according to the present invention.

In this semiconductor laser driving device, CP
U11 is connected to the base of the transistor Q11 via the feedthrough capacitor C11 and the coil L11, and is connected to one end of the capacitor C13 and further to the capacitor C1.
4 is connected to one end.

The other end of the capacitor C13 has a coil L1.
2 is connected to one end of the coil L12, and the other end of the coil L12 is connected to the reference potential point (GND) via the shield case 12.

Further, the CPU 11 is connected to a reproducing semiconductor laser drive circuit (R LD driver) 14 via a reproducing control circuit (R control circuit) 13, and this reproducing semiconductor laser drive circuit 14 is a feedthrough capacitor. C15,
Further, it is connected to one end of a capacitor C16 via a coil L13, and is also connected to the anode of the semiconductor laser LD11 and the cathode of the switching diode D11. The cathode of this semiconductor laser LD11 is connected via a shield case 12 to a reference potential point (GND). )It is connected to the.

Further, the other end of the capacitor C16 is
One end of the coil L14, one end of the resistor R11, and the collector of the transistor Q12 are connected in parallel. Further, the CPU 11 is a recording control circuit (W control circuit) 15
Is connected to a recording semiconductor laser drive circuit (W LD driver) 16 via a switch, and the recording semiconductor laser drive circuit 16 is connected to a switching diode D11 via a feedthrough capacitor C17 and the switch 1
7 is connected to one end.

Further, a control signal line is connected from the CPU 11 to the control end of the switch 17, and the other end of the switch 17 is connected to the reference potential point. Also, CP
A recording information signal line is connected from U11 to the recording control circuit 15.

The voltage source (+ 5V) is fed through the feedthrough capacitor C18 and the coil L15 to the coil L14.
, The other end of the resistor R11, the other end of the resistor R12, the collector of the transistor Q11, and the reference potential point via the capacitor C19.

Further, the other end of the resistor R12 is the base of the transistor Q12, one end of the resistor R13, and the capacitor C.
20 is connected to one end of each, and the transistor Q1
The emitter of 2 is a resistor R14, and the shield case 12
Is connected to the reference potential point via.

The emitter of the transistor Q11 is connected to the other end of the capacitor C20, one end of the capacitor C21, one end of the resistor R15, and the other end of the capacitor C14. Further, the other end of the resistor R13, the other end of the capacitor C21, and the other end of the resistor R15 are connected to the reference potential point via the shield case 12. Also,
The shield case 12 is connected to the reference potential point.

Further, the transistor Q11, the resistor R15,
The capacitors C13, C14, C21 and the coil L12 constitute a high frequency oscillation circuit, and the control voltage from the CPU 11 controls the base voltage of the transistor Q11 to control ON / OFF of the high frequency oscillation circuit. The output of the high-frequency oscillation circuit outputs a high-frequency current to the semiconductor laser LD by a high-frequency amplifier circuit including a transistor Q12, resistors R11, R12, R13, R14, capacitors C16, C20, and a coil L14.
Supply to 11.

Further, the feedthrough capacitors C11, C1
5, C17 and C18 are fixed by penetrating the shield case 12. The high-frequency current from the high-frequency amplifier circuit is radiated to the outside of the shield case 12 by the unnecessary radiation prevention circuit 18 of the LC filter including the coils L11, L13, L15 and the feedthrough capacitors C11, C15, C18. It is supposed not to be done.

At this time, the semiconductor laser L at the time of recording
The frequency characteristics of the recording current supplied to D11 have two valleys at the series resonance frequencies f11 and f12. Of these, the series resonance frequency f11 is a series resonance frequency due to the LC of the high-frequency oscillation circuit, and the series resonance frequency f12 is a series resonance frequency due to the coil L13 and the capacitor C15 which are LC filters on the reproducing side.

Here, the series resonance frequency f11 is determined by the coil L.
14, the series resonance frequency due to the capacitor C16,
It is expressed by the following equation. f11 = 1 / {2π (L14 · C16) ^1/2 } (4) Further, the series resonance frequency f12 is the series resonance frequency due to the coil L13 and the capacitor C15, which are the LC filter on the reproducing side, as described above. It is represented by a formula.

F12 = 1 / {2π (L13 · C15) ^1/2 } (5) Therefore, when the frequency band of the write data pattern at the time of recording in the semiconductor laser driving device of the second embodiment is set to flow to fhigh, the series resonance frequencies f11 and f12 are the frequency bands of the write data pattern as shown in FIG. It is configured so as to be out of the band from flow to fhigh. That is, the series resonance frequencies f11 and f12 are set outside the frequency band of the write data pattern from low to high by the equations (4) and (5).

In the semiconductor laser driving device of the second embodiment having the above-described structure, during reproduction, the control voltage from the CPU 11 is applied to the high frequency oscillation circuit, and the high frequency is superposed on the recording current. LD
11 is supplied.

On the other hand, at the time of recording, the control voltage from the CPU 11 is not applied to the high frequency oscillation circuit, and the high frequency oscillation circuit is turned off. Then, by setting the series resonance frequencies f11 and f12 outside the frequency band from flow frequency flow to fhigh of the write data pattern at the time of recording,
The recording current is applied to the semiconductor laser LD11 without being affected by the LC series resonance frequency f11 of the high-frequency oscillator circuit and the series resonance frequency f12 of the reproducing-side LC filter.
Is supplied to.

As described above, according to the semiconductor laser driving device of the second embodiment, the recording operation can be surely performed by flattening the characteristics in the frequency band of the write data pattern.

[0056]

As described above, according to the present invention, there is provided a semiconductor laser driving device capable of performing a reliable recording operation by improving the frequency characteristic of the current applied to the semiconductor laser during recording. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a semiconductor laser driving device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing frequency characteristics of a current applied to a semiconductor laser LD1 during recording in the semiconductor laser driving device of the first embodiment.

FIG. 3 is a circuit diagram showing a configuration of a semiconductor laser drive device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing frequency characteristics of a current applied to a semiconductor laser LD11 during recording in the semiconductor laser driving device of the second embodiment.

FIG. 5 is a diagram showing a configuration of a semiconductor laser driving device of a first conventional example.

FIG. 6 is a diagram showing a configuration of a semiconductor laser driving device of a second conventional example.

FIG. 7 is a detailed circuit diagram of a high frequency oscillation circuit 122 in a semiconductor laser driving device of a second conventional example.

FIG. 8 is a diagram showing frequency characteristics of a current applied to the semiconductor laser 121 during recording in the semiconductor laser driving device of the second conventional example.

[Explanation of symbols]

1, 11 ... CPU, 2, 12 ... Shield case, 3, 1
3 ... Reproduction control circuit (R control circuit), 4, 14 ... Reproduction semiconductor laser drive circuit (R LD driver), 5, 1
5 ... Recording control circuit (W control circuit), 6, 16 ... Recording semiconductor laser drive circuit (W LD driver), 7, 1
7 ... Switch, 8 ... High-frequency oscillation circuit, 9, 18 ... Unwanted radiation prevention circuit, LD1, LD11 ... Semiconductor laser, D1,
D11 ... Switching diode, R1, R2, R1
1, R12, R13, R14, R15 ... Resistors, C1, C
3, C7, C9, C11, C15, C17, 18 ... Feedthrough capacitors, C2, C4, C5, C6, C8, C13,
C14, C16, C19, C20, C21 ... Capacitors, L1, L2, L3, L4, L5, L11, L12,
L13, L14, L15 ... Coil, Q1, Q11, Q1
2 ... Transistor.

Claims (1)

[Claims] 1. A semiconductor laser for supplying a recording laser beam and a reproducing laser beam for irradiating an optical recording medium, and a recording laser for supplying a recording drive signal for irradiating the recording laser beam to the semiconductor laser. A line, a reproducing line for supplying a reproducing drive signal for irradiating the reproducing laser beam to the semiconductor laser, and a reproducing line for superimposing a high-frequency signal on the reproducing drive signal and supplying the reproducing laser signal from the semiconductor laser. Frequency superimposing oscillation means for reducing laser noise of the laser light for use, unnecessary radiation preventing means provided in the reproducing line for preventing unnecessary radiation accompanying the driving of the high frequency superimposing oscillation means, the semiconductor laser and the high frequency superimposing A shield means for accommodating the oscillating means; and a shield means for the unwanted radiation and the high-frequency superposed oscillating means viewed from the recording line. The band impedance is reduced semiconductor laser driving device and sets the band of the recording drive signal.