JP3786348B2 - High frequency superposition module for optical pickup - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup high-frequency superposition module provided in an information recording / reproducing apparatus using an optical recording medium such as a DVD, MD, CD, or the like.
[0002]
[Prior art]
During the reproducing operation by the optical pickup, laser noise is induced by the return light noise. In order to prevent the generation of this laser noise, Japanese Patent Publication No. 59-9086 discloses that a high-frequency current is superimposed on a direct current that drives a laser diode, and the multi-mode driving is performed. FIG. 5A is a block diagram showing a conventional circuit configuration of a high frequency superposition module that drives by superposing this high frequency current.
[0003]
In FIG. 5A, 1 is a laser diode, and 2 is a high-frequency superposition module for driving them. The high frequency superposition module 2 includes a power supply terminal 4 for supplying a direct current to the laser diode 1 through a filter 3, an oscillation circuit 5 for supplying a high frequency current to the laser diode 1, and a direct current power supply for the oscillation circuit 5 A terminal 6; a filter 7 that prevents the oscillated high frequency from returning to the power supply terminal 6; and an impedance matching circuit 8 that performs impedance matching between the oscillation circuit and the circuit on the laser diode 1 side to prevent reflection. is doing.
[0004]
The oscillation circuit 5 constitutes an oscillation circuit using the LC resonance phenomenon, oscillates at a frequency of several hundred MHz, and drives the laser diode 1 by superimposing a high frequency current on a direct current from the power supply terminal 4. As a result, the optical output generated by the laser diode 1 has an output in which peaks exist at a plurality of wavelengths at a constant wavelength interval, and the envelope of the peak forms a mountain shape. That is, the longitudinal mode of the laser beam is multi- pleted and the mode popping noise is prevented.
[0005]
[Problems to be solved by the invention]
It is necessary to provide a plurality of laser diodes having different wavelengths of output laser light, such as for DVD and CD, in one optical pickup. In the case of having such a plurality of laser diodes, a case where two laser diodes are arranged, and a laser diode for DVD 1A and a CD for CD via an adhesive layer 10 on one substrate 9 as shown in FIG. As shown in FIG. 5C, the laser diode 1B and the laser diode 1A for DVD and the laser diode 1B for CD are integrally formed on one substrate 11 and attached to the substrate 9. There is a thing. As shown in FIGS. 5B and 5C, a structure in which two laser diodes are provided on one substrate is effective for downsizing and also guides orthogonal laser beams in the same direction. There is an advantage that no element is required.
[0006]
In particular, as shown in FIG. 5C, when two laser diodes 1A and 1B are formed on one substrate 11, the distance between these laser diodes 1A and 1B can be set narrowly and accurately. For this reason, as shown in FIG. 5B, there is an advantage that means for position adjustment or the like becomes unnecessary as compared with the case of adhesion.
[0007]
In the case of arranging two laser diodes so that the output laser beams are orthogonal to each other and in the case of the arrangement of the laser diodes shown in FIG. 5B, each laser diode is manufactured independently. In such cases, for a laser diode 1B for CD, by utilizing the self-excited oscillation, wherein at when the oscillation circuit 5 is not necessarily required results, as shown in FIG. 5 (C), on the same substrate 9 When forming the two laser diodes 1A and 1B, the laser diode 1B for CD needs to superimpose the high frequency current generated by the oscillation circuit 5 on the direct current and supply the laser diode 1B to the laser diode 1B due to the material and the like. . In this case, if an oscillation circuit corresponding to the laser diode is provided for each laser diode, the number of components is increased, resulting in an increase in cost and difficulty in miniaturization.
[0008]
SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a high-frequency superposition module for an optical pickup that includes a plurality of laser diodes for an optical pickup and superimposes a high-frequency current on a direct current to flow through the laser diode. It aims at providing what can aim at cost reduction.
[0009]
[Means for Solving the Problems]
The high-frequency superposition module for optical pickup according to claim 1 includes a plurality of laser diodes for optical pickup that output laser beams of different wavelengths,
One oscillation circuit is shared as a high-frequency current supply source for the plurality of laser diodes ,
The inductor that constitutes the oscillation circuit and at least a part of the inductor that is connected to each laser diode and prevents the return of the high frequency to the power source side are inductively coupled to apply a high frequency to the laser diode. It is characterized by.
[0010]
The high-frequency superposition module for optical pickup according to claim 2 includes a plurality of laser diodes for optical pickup that output laser beams of different wavelengths,
One oscillation circuit is shared as a high-frequency current supply source for the plurality of laser diodes,
A laser diode by inductively coupling an inductor for preventing a high frequency return to the power supply side of the oscillation circuit and at least a part of the inductor connected to each laser diode to prevent a high frequency return to the power supply side It is characterized in that it is configured to apply high frequency to .
[0011]
In this way, if the configuration is such that the high-frequency current generated by one oscillation circuit flows through a plurality of laser diodes, only one oscillation circuit is required, the number of components is reduced, the configuration is simplified, and the size and cost are reduced. Reduction can be achieved.
[0012]
In addition, since the inductor that prevents the return to the oscillation circuit or the generated high-frequency power supply and the inductor connected in series with the laser diode are inductively coupled, a high frequency is applied to the laser diode. In addition to being able to reduce, the configuration is simplified, and the size and cost can be reduced.
[0013]
The high-frequency superposition module for an optical pickup according to claim 3 is characterized in that in claim 1 or 2 ,
The plurality of laser diodes have a structure in which the laser diodes are integrally formed on the same substrate.
[0014]
Thus, by applying the configuration of the oscillation circuit to a substrate in which a plurality of laser diodes are formed, it is possible to further reduce the number of constituent members as a whole, and to further reduce the size and cost.
[0015]
A high-frequency superposition module for an optical pickup according to claim 4 is any one of claims 1 to 4,
The high frequency output from the oscillation circuit is applied to at least a part of the laser diodes via a capacitor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an embodiment of a high-frequency superposition module for an optical pickup according to the present invention, and FIG. 2 is a circuit diagram showing a reference example thereof . In FIG. 1, 1A is a laser diode for optical pickup, and 13 is a high frequency superposition module for driving them. The high frequency superposition module 13 is an oscillation for supplying a high frequency current in common to the power supply terminals 4A and 4B for supplying a direct current to the laser diodes 1A and 1B via the filters 3A and 3B, respectively. Impedance for electrically coupling the circuit 5, the DC power supply terminal 6 of the oscillation circuit 5, the filter 7 for preventing the oscillated high frequency from returning to the power supply terminal 6 side, and the circuit on the laser diode 1 side And a matching circuit 12.
[0017]
As shown in FIG. 2, the filters 3A and 3B connected to the laser diodes 1A and 1B are constituted by inductors. The filter 7 connected to the oscillation circuit 5 includes an inductor L1 and a capacitor C1. The oscillation circuit 5 includes an active element including a transistor Q and passive elements including capacitors C2 to C4, an inductor L2, and resistors R1 to R3. The oscillation circuit 5 utilizes a resonance phenomenon composed of an inductor L2 and capacitors C2 to C4. The impedance matching circuit 12 includes capacitors C5 and C6 for applying the output of the oscillation circuit 5 to the laser diode 1A, and capacitors C7 and C8 for applying the output of the oscillation circuit 5 to the laser diode 1B.
[0018]
In this configuration, when an optical pickup is used for DVD, a DC current is supplied from the DC power supply terminal 4A to the laser diode 1A, and at the same time, power is supplied from the power supply terminal 6 to the oscillation circuit 5 to oscillate. The oscillation circuit 5 oscillates at a high frequency of several hundred MHz and supplies a high-frequency current to the laser diode 1A via an impedance matching circuit including capacitors C5 and C6. As a result, the longitudinal modes of the laser light generated by the laser diode 1A are multiplied and laser noise is prevented. In this case, a high-frequency current is also supplied to the CD laser diode 1B via the capacitors C7 and C8, but no light is emitted because no DC current is supplied from the DC power supply terminal 4B.
[0019]
When an optical pickup is used for CD, a direct current is supplied from the DC power supply terminal 4B to the laser diode 1B, and at the same time, power is supplied from the power supply terminal 6 to the oscillation circuit 5 to oscillate. The output high-frequency current of the oscillation circuit 5 is supplied to the CD laser diode 1B via the capacitors C7 and C8, and the generation of laser noise is prevented.
[0020]
Thus, by sharing the oscillation circuit 5 for the DVD and CD laser diodes 1A and 1B, only one oscillation circuit is required, the number of parts is reduced, the configuration is simplified, and the size and cost are reduced. I can plan.
[0021]
In particular, as shown in FIG. 5C, the configuration in which a plurality of laser diodes 1A and 1B are formed on one substrate 11 can reduce the number of components. By adding the number of 5, it is possible to further reduce the number of parts, reduce the size, and reduce the cost.
[0022]
FIG. 3 is a circuit diagram showing an embodiment of the present invention. This embodiment also uses a resonance phenomenon comprising an inductor L2 and capacitors C2 to C4. In this oscillation circuit, the inductor L2 constituting the oscillation circuit 5 and the inductors 3A and 3B connected in series to the laser diodes 1A and 1B are coupled by inductive coupling (M), and a high-frequency current is supplied to the laser diodes 1A and 1B. To supply.
[0023]
In this embodiment , the same laser noise reduction effect as described above can be obtained. Furthermore, in the present embodiment , the inductor L2 that causes a resonance phenomenon and the inductors 3A and 3B that prevent the return of the high frequency to the power supply side are inductively coupled to add high frequencies to the laser diodes 1A and 1B. Compared to the second reference example , some of the capacitors C5 and C7 of the impedance matching circuit 12 can be reduced, and the number of parts can be further reduced, the configuration can be simplified, the size can be reduced, and the cost can be reduced. is there. For one of the laser diodes 1A and 1B, a high frequency may be applied to the laser diode 1A or 1B by the capacitive coupling capacitance of the capacitor C5 or C7 as in the configuration of FIG.
[0024]
FIG. 4 is a circuit diagram showing another embodiment of the present invention. In this embodiment , the laser diode 1A and the oscillation circuit 5 are coupled by capacitors C5 and C6, and the oscillation circuit 5 and the laser diode 1B are: The inductor L1 constituting the filter 7 and the inductor 3B connected in series to the laser diode 1B are coupled by inductive coupling. Also in this configuration, a high frequency current is supplied to the laser diode 1B by the high frequency induced in the inductor 3B.
[0025]
In this embodiment , the same laser noise effect as described above can be obtained. Also, in this embodiment , compared to the reference example of FIG. 2, the capacitor C7 can be omitted, and there is an advantage that the number of parts can be reduced, the configuration can be simplified, the size can be reduced, and the cost can be reduced. In FIG. 4, the inductor L1 and the inductor 3A may also be inductively coupled.
[0026]
The present invention can be applied not only to DVD and CD laser diodes, but also to an optical pickup provided with a plurality of laser diodes including MD or other laser diodes.
[0027]
【The invention's effect】
According to claim 1, 2, 4, oscillation circuit 1 Tsudesumi, configured with the number of parts is reduced can be simplified, miniaturization and cost reduction can be achieved.
[0028]
In addition, since the inductor that prevents return to the oscillation circuit or the generated high frequency power supply and the inductor connected in series with the laser diode are inductively coupled, the high frequency is applied to the laser diode. In addition to being able to reduce, the configuration is simplified, and the size and cost can be reduced.
[0029]
According to the third aspect, by applying the configuration of the oscillation circuit to a substrate in which a plurality of laser diodes are formed, it is possible to further reduce the number of components as a whole, and to further reduce the size and cost. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a high-frequency superposition module according to the present invention.
FIG. 2 is a circuit diagram showing a reference example of the high-frequency superposition module of FIG. 1;
FIG. 3 is a block diagram showing an embodiment of a high frequency superposition module according to the present invention.
It is a block diagram showing another embodiment of a high frequency superimposing module according to the present invention; FIG.
5A is a block diagram showing an example of a conventional high-frequency superposition module, and FIGS. 5B and 5C are side views showing a conventional combination structure of a plurality of laser diodes, respectively.
[Explanation of symbols]
1A, 1B: Laser diode, 3A, 3B: Filter (inductor), 4A, 4B: DC power supply terminal, 5: Oscillator circuit, 6: Power supply terminal, 7: Filter, 9, 11: Substrate, 10: Adhesive part, 12 : Impedance matching circuit, 13: High frequency superposition module

Claims (4)

With a plurality of optical pickup laser diodes that output laser beams of different wavelengths,
One oscillation circuit is shared as a high-frequency current supply source for the plurality of laser diodes ,
The inductor that constitutes the oscillation circuit and at least a part of the inductor that is connected to each laser diode and prevents the return of the high frequency to the power source side are inductively coupled to apply a high frequency to the laser diode. A high-frequency superposition module for optical pickups. With a plurality of optical pickup laser diodes that output laser beams of different wavelengths,
One oscillation circuit is shared as a high-frequency current supply source for the plurality of laser diodes,
A laser diode by inductively coupling an inductor for preventing a high frequency return to the power supply side of the oscillation circuit and at least a part of the inductor connected to each laser diode to prevent a high frequency return to the power supply side A high frequency superposition module for an optical pickup, characterized in that a high frequency is applied to the optical pickup. In the high frequency superposition module for optical pickups according to claim 1 or 2 ,
The plurality of laser diodes have a structure in which each laser diode is integrally formed on the same substrate. In the high frequency superposition module for optical pickups according to any one of claims 1 to 3 ,
A high frequency superposition module for an optical pickup, characterized in that a high frequency as an output of the oscillation circuit is applied to at least a part of the laser diode via a capacitor.

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