JPH08124201A - Optical pickup - Google Patents

Abstract

PURPOSE: To obtain an inexpensive optical pickup in which leakage of electromagnetic wave can be prevented without causing deterioration of assembling performance due to increase of the number of components. CONSTITUTION: A high frequency superposition circuit 23 is mounted on an FPC 24 containing a wiring pattern 25 for connecting a laser control circuit 22 with the high frequency superposition circuit 23, and a ground shield 26 for connecting the ground of the laser control circuit 22 with that of the high frequency superposition circuit 23. The FPC 24 is then folded to surround the high frequency superposition circuit 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup having a high frequency superimposing unit used in an information recording device such as an optical disc and a magneto-optical disc.

[0002]

2. Description of the Related Art Generally, an optical pickup in an optical disk device narrows a light beam from a semiconductor laser to an optical diffraction limit with an objective lens and forms a minute spot of about 1 μm on an information recording medium such as an optical disk or a magneto-optical disk. ,
The reflected light is guided to the detection optical system, photoelectrically converted by the detection optical system, and then detected and calculated by the detection circuit to obtain the information.

Recently, a laser light source is required to output a very large laser beam in order to increase the speed with an increase in the amount of information and when recording and erasing data in a rewritable optical disk device. In addition to achieving higher output, there is also a demand for optimizing a laser spot in order to increase the capacity and density of an optical disc.

By the way, in the optical disk device, so-called return light is generated in which the reflected light reflected by the optical disk returns to the laser light source due to its constitution. Particularly, in a high output laser light source, noise due to this return light is a problem. Therefore, it is required to reduce the noise of the laser light source. In order to prevent this, pulsed light emission of a laser light source at high frequency (high frequency superposition) is generally performed. Since this high frequency superimposition is performed at several hundred MHz and the degree of modulation is several hundred percent, the high frequency component is generated as an electromagnetic wave from the current flowing through the high frequency generation circuit that superimposes the high frequency component on the direct current, and unnecessary radiation to the outside occurs. Will occur. For this reason, EMI (electromagnetic interference) occurs,
It adversely affects other electric circuits. Further, in the detection circuit for detecting and calculating the photoelectrically converted signal, since a high-speed and weak signal is detected, there is a problem that it is easily affected by noise from the outside and is most easily affected by the electromagnetic interference described above. there were.

As a means for solving such a problem, there is, for example, one described in Japanese Patent Laid-Open No. 3-227585, in which the shield plate is mounted on the mounting frame in the high-frequency superimposing circuit and then the shield plate is mounted. The high frequency superposition circuit is covered with a shield plate by being screwed to the mounting frame to shield electromagnetic waves generated from the high frequency superposition circuit. Therefore, the detection circuit is not affected by noise.

[0006]

However, in such a conventional optical pickup, since the shield plate is fixed to the mounting frame with screws, electrical contact is not sufficient and the number of parts is small. However, there is a problem in that the assembling property deteriorates and the cost of the optical pickup increases as a result.

Therefore, it is an object of the present invention to provide an inexpensive optical pickup capable of preventing leakage of electromagnetic waves while preventing the assembling property from being deteriorated due to an increase in the number of parts. And It is an object of the present invention to provide an inexpensive optical pickup capable of blocking the electromagnetic waves generated from the high frequency superposition circuit while preventing the number of parts from increasing and the assembling performance to deteriorate. .

[0008]

To achieve the above object, the invention according to claim 1 includes a semiconductor laser, a high frequency superimposing circuit for emitting the semiconductor laser at a high frequency, and a drive circuit for driving the high frequency superimposing circuit. A flexible printed wiring board connecting the driving circuit and the high frequency superimposing circuit, and a laser beam output from a semiconductor laser is condensed by an objective lens to form a spot on an information recording medium. In an optical pickup configured to read at least by a detection means, a high-frequency superimposing circuit is mounted at a predetermined location of the flexible printed wiring board, and a wiring pattern for connecting a driving circuit and the high-frequency superimposing circuit to the inside of the board, and a driving circuit. A shield part for connecting the ground of the circuit and the ground of the high frequency superposition circuit, and By bending the table printed wiring board is characterized in that surrounds the high-frequency superposition circuit by the flexible printed wiring board.

To achieve the above object, the invention according to claim 2 is characterized in that, in the invention according to claim 1, the shielding portion is made of an amorphous material. In order to achieve the above object, the invention according to claim 3 is the invention according to claim 1 or 2, wherein when the flexible printed wiring board is bent, solder land portions are provided on opposing board portions around the high frequency superposition circuit. Is provided, and the solder land portion is soldered.

In order to achieve the above object, the invention described in claim 4 is output from a semiconductor laser, a high frequency superimposing circuit for emitting the semiconductor laser at a high frequency, a drive circuit for driving the high frequency superimposing circuit, and a semiconductor laser. An objective lens for condensing laser light to form a spot on an information recording medium, an optical system having a light receiving element for photoelectrically converting reflected light from the information recording medium, and the light receiving element. A detection circuit for reading information on at least a recording medium based on a signal photoelectrically converted by, and an optical pickup including the detection circuit at a predetermined position of a flexible printed wiring board, and inside the board, Connect the wiring pattern that connects the detection circuit and the light receiving element to the ground of the detection circuit and the frame on which the flexible wiring board is mounted. A shielding unit, the provided detection circuit by bending the flexible printed wiring board is to wherein the surrounding by the flexible printed wiring board.

[0011]

According to the first aspect of the present invention, the high-frequency superimposing circuit is mounted at a predetermined position of the flexible printed wiring board, and the wiring pattern for connecting the drive circuit and the high-frequency superimposing circuit to the inside of the board and the drive circuit. And a shield connecting the ground and the ground of the high-frequency superposition circuit,
The high frequency superposition circuit is surrounded by the flexible printed wiring board by bending the flexible printed wiring board.

Therefore, the electromagnetic wave generated from the high frequency superposed circuit is blocked by the shielding portion of the flexible printed wiring board, does not leak to the outside, and the surrounding electric circuits are not adversely affected. Also, since the high frequency superposition circuit is mounted on the flexible printed wiring board and integrated, the number of parts is reduced (substantially one part for preventing leakage) and good assembling. Therefore, an inexpensive optical pickup can be obtained.

According to the second aspect of the invention, since the shielding portion is made of amorphous (amorphous metal), electromagnetic waves can be shielded more efficiently. According to the third aspect of the present invention, when the flexible printed wiring board is bent, solder land portions are provided on opposing board portions around the high frequency superposition circuit, and the solder land portions are soldered. Therefore, the high frequency superposition circuit is sealed by the flexible printed wiring board, and electromagnetic waves are blocked at a higher level.

According to a fourth aspect of the present invention, the detection circuit is mounted at a predetermined position on the flexible printed wiring board, and a wiring pattern for connecting the detection circuit and the light receiving element and a ground of the detection circuit are provided inside the board. And a shielding portion for connecting a frame to which the flexible printed wiring board is attached, and by bending the flexible printed wiring board, the detection circuit is surrounded by the flexible printed wiring board.

Therefore, the electromagnetic wave generated from the high frequency superposition circuit is not blocked by the shielding portion of the flexible printed wiring board and adversely affects the detection circuit. Further, since the detection circuit is mounted on the flexible printed wiring board and integrated, the number of parts is reduced (substantially only one part is provided to block electromagnetic waves) and the assembling property is good. Therefore, an inexpensive optical pickup can be obtained.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views showing an embodiment of an optical pickup according to the invention described in claim 1 or 2. FIG. 1 shows a schematic diagram of an optical pickup in an optical disc apparatus. First, the optical pickup apparatus will be described.

In FIG. 1, 1 is a semiconductor laser,
Laser light output from the semiconductor laser 1 is converted into parallel light by a coupling lens 2 and then transmitted through a beam splitter 3 and is spotted by an objective lens 4 on an information recording medium 5 such as a magneto-optical disk to a spot of about 1 μm. Is formed. The light reflected from the recording medium 5 is transmitted through the objective lens 4 again, converted into parallel light, reflected by the beam splitter 3 and converted into converged light by the condenser lens 6, and then the knife edge prism 7 Part of the light is blocked by. Then, the light which is not shielded goes straight and is incident on the focus detection light receiving element 8, and focus detection is performed by the so-called knife edge method.

On the other hand, the light reflected by the knife edge prism 7 has its polarization plane rotated by 45 ° by the λ / 2 plate 9, and is then separated by the polarization beam splitter 10 into P-polarized light and S-polarized light. After the P-polarized light passes through the polarization beam splitter 10,
It is incident on the track detection / information signal detection light receiving element 11, and S
The polarized light enters the information signal detecting element 12. Track detection is performed by the so-called push-pull method, and information signal (magneto-optical signal) is detected by the difference signal between the light receiving elements 11 and 12.

Each of the light receiving elements 8, 11 and 12 photoelectrically changes each input signal, and the photoelectrically converted signal is input to the detection circuit 13, and the detection circuit 13 amplifies and weakens the weak input signal. A calculation for reading is performed. By the way, because of the characteristics of the beam splitter 3, it is impossible to reflect 100% of the reflected light from the recording medium 5 and guide it to the optical system on the side of the condenser lens 6, so that the transmitted light is returned to the semiconductor laser 1 as return light. Becomes incident. This return light disturbs the oscillation mode of the semiconductor laser 1, causing noise in the detection signal,
It may not be possible to accurately reproduce and write information.

As a countermeasure against this, it is common practice to superimpose a high-frequency current on the semiconductor laser drive current, drive the semiconductor laser 1 at high speed pulses, and cause the semiconductor laser 1 to emit light in a multi-mode. A high frequency superposition unit 14 is provided as the device. However, when high-frequency superimposing as described above is performed, the frequency generated from the high-frequency superimposing unit 14 is several hundred MHz, so that unnecessary radiation noise occurs and other electric circuits such as the detection circuit 13 are generated. It will have an adverse effect. In particular, since the detection circuit 13 detects a weak signal at high speed, it is easily affected by noise from the outside, and is most easily affected by the above-mentioned electromagnetic interference.

Therefore, in this embodiment, an optical pickup which is prevented from being affected by electromagnetic waves is provided at a low cost. The configuration will be specifically described below. In the embodiment, the condensing lens 6, the knife edge prism 7, the focus detecting element 8, the λ / 2 plate 9, the polarization beam splitter 10, the light receiving elements 11 and 12, and the detecting circuit 13 constitute the detecting means. Is.

2 to 4, 21 is a fixing member,
The fixing member 21 is provided with a semiconductor laser 1, a detection circuit 13, and a semiconductor laser control circuit 22 as a drive circuit. A high frequency superposition circuit 23 is connected to the semiconductor laser 1, and the semiconductor superposition circuit 23 superposes a high frequency signal on the semiconductor laser 1. This semiconductor superposition circuit 23 is a flexible printed wiring board made of polyimide or the like (hereinafter,
(It is also called FPC) 24, and this FPC2
Inside of 4, a wiring pattern 25 made of copper foil and a ground shield 26 as a shielding portion are provided.

The wiring pattern 25 connects the laser control circuit 22 and the high frequency superposition circuit 23, and the high frequency superposition circuit 23 is driven by the laser control circuit 22 via the wiring pattern 25. Further, the ground shield 26 is arranged outside the wiring pattern 25 as shown in FIG. 4, and the ground of the laser control circuit 22 and the high frequency superimposing circuit.
23 grounds are connected. This high frequency superposition circuit 23 is surrounded by the FPC 24, and the superposition circuit 23 is
It is shielded by the ground shield 26 of C24. The superposition circuit 22, the laser control circuit 23 and the FPC 24 described above constitute the high frequency superposition unit 14 shown in FIG.

Next, the operation will be described. FPC of this embodiment
Before being attached to the fixing member 21, 24 is open as shown in FIG. From this state, after the superposing circuit 23 is connected to the back surface of the semiconductor laser 1 by soldering together with the FPC 24, the FPC 24 is bent along the bending line AA, and the wiring pattern 25 and the ground shield 26 are connected to the semiconductor laser control circuit 22.

Therefore, the drive signal output by the laser control circuit 22 is transmitted to the superposition circuit 23 by the wiring pattern 25, and the semiconductor laser 1 emits light. Further, the noise radiated from the superposition circuit 23 is absorbed by the ground shield 26 and cut off from the outside. As described above, in this embodiment, the high frequency superimposing circuit 23 is mounted on the FPC 24, and the wiring pattern 25 for connecting the laser control circuit 22 and the high frequency superimposing circuit 23 to the inside of the FPC 24, the ground of the laser control circuit 22 and the high frequency. Since the high frequency superposition circuit 23 is surrounded by the FPC 24 by providing the ground shield 26 for connecting the ground of the superposition circuit 23 and bending the FPC 24, as described above, the high frequency superposition circuit 23.
It is possible to prevent the electromagnetic waves generated from from leaking to the outside by blocking with the ground shield 26 of the FPC 24.
It is possible to prevent the surrounding electric circuits such as the detection circuit 13 from being adversely affected.

Further, since the high frequency superposition circuit 23 is mounted on the FPC 24 and integrated, the number of parts can be reduced (substantially one part for preventing leakage) and the assembling property. Can be improved, and an inexpensive optical pickup can be obtained. Although the ground shield 26 is made of copper foil in this embodiment, it may be made of amorphous metal instead of this. By doing so, electromagnetic waves can be blocked more efficiently than with copper foil.

Further, although the present embodiment is applied to a fixed optical pickup, the present invention is not limited to this, and as shown in FIGS. 6 and 7, the light of a separation optical system including a moving optical system and a fixed optical system is used. It may be applied to pickups. In the present embodiment, description will be given using the configuration of the optical pickup described above. In FIGS. 6 and 7, 41 is a turntable on which the information recording medium 5 is loaded, and the table 41 is rotationally driven by a spindle motor 42. Although the fixed optical system is not shown in detail, the semiconductor laser 1 attached to the fixed frame 43 and the coupling lens 2, the beam splitter 3, the condenser lens 6, the knife edge prism 7, the focus housed in the fixed frame 43 Detection element 8,
λ / 2 plate 9, polarization beam splitter 10, light receiving elements 11, 1
2. It is composed of a detection circuit 13. The moving optical system is a directory prism 45 housed in a moving frame 44.
And a seek motor, which is composed of an objective lens 4 and
By 46, it moves in the radial direction of the recording medium 5.

In this embodiment, the laser light output from the semiconductor laser 1 is converted into parallel light by the coupling lens 2 and transmitted through the beam splitter 3, and then guided by the directory lens 45 to the objective lens 4 for recording. A spot of about 1 μm is formed on the medium 5, and the light reflected from the recording medium 5 is transmitted through the objective lens 4 again and reflected by the beam splitter 3 by the directory lens 45. Is similar to that described in FIG. Then, when forming spots on the recording medium 5, the recording medium 5 is turned on by the turntable 41.
And the moving frame 44 is moved in the radial direction of the recording medium 5 by the seek motor 46 to read or erase information on the recording medium 5. In the present embodiment, even if the semiconductor laser 1 of such a separation optical system is provided with the high frequency superposition unit 14, the same effects as those described above can be obtained.

8 and 9 are views showing an embodiment of the optical pickup according to the invention described in claim 3. In this embodiment,
Since the other points are the same as the above-mentioned embodiment except that a soldering land portion is provided around the high-frequency superposition circuit, the other components are the same as those in the above-mentioned embodiment. explain. In FIGS. 8 and 9, 31 is an FPC in which the high frequency superposition circuit 23 is mounted, and the wiring pattern 25 and the ground shield 26 are incorporated.
When bent, the solder land portions 32 are provided on the opposing board portions around the high frequency superposition circuit 23.

In this embodiment, when the high frequency superposing circuit 23 is attached to the fixing member 21, the superposing circuit 23 together with the FPC 31 is connected to the back surface of the semiconductor laser 1 by soldering and then opened as shown in FIG. 9 (a). FPC31 in the bent state B-
The wiring pattern 25 and the ground shield 26 are bent via B, the semiconductor laser control circuit 22 is connected, and the solder land portions 32 are soldered to each other to seal the high frequency superposition circuit 23 by the FPC 24. In this way, the high frequency superposition circuit 23
If the FPC 31 is closed, the electromagnetic wave can be blocked at a higher level.

FIGS. 10 and 11 are views showing an embodiment of the optical pickup according to the invention described in claim 4. In this embodiment,
An example in which the detection circuit 13 side is devised so as not to be affected by electromagnetic waves is shown. Since the structure of the optical pickup is the same as that shown in FIG. 1, the same reference numerals are given to the same structures for description. Reference numeral 51 is a fixing member as a frame. The fixing member 51 includes a semiconductor laser 1 and a detection circuit.
13, semiconductor laser control circuit 22 and light receiving elements 8, 11,
Twelve are provided. A high frequency superposition circuit 23 is connected to the semiconductor laser 1, and the semiconductor superposition circuit 23 superposes a high frequency signal on the semiconductor laser 1. The semiconductor superposition circuit 23 of this embodiment is not shielded by FPC as in the above embodiments.

The detection circuit 13 is mounted on an FPC 52 made of polyimide or the like. Inside the FPC 52, a wiring pattern 53 made of copper foil and a ground shield 54 as a shielding portion are provided. Wiring pattern
Reference numeral 53 connects the detection circuit 13 and the respective light receiving elements 8, 11 and 12, and the signals photoelectrically converted by the respective light receiving elements 8, 11 and 12 are input to the detection circuit 13 via the wiring pattern 53, and the detection circuit
An operation for amplifying and reading a weak input signal is performed by 13. In this embodiment, when the condenser lens 6, the knife edge prism 7, the focus detecting element 8, the λ / 2 plate 9 and the polarization beam splitter 10 in FIG. 1 receive the reflected light from the information recording medium 5, An optical system having light receiving elements 8, 11 and 12 for photoelectrically converting the reflected light is constituted, and at least information on the recording medium 5 is detected by the detection circuit 13 based on the signals photoelectrically converted by the light receiving elements 8, 11 and 12. Constitutes a detection circuit for reading.

On the other hand, the ground shield 54 is a wiring pattern.
It is disposed outside 53 and connects the ground of the detection circuit 13 and the fixed member 51 (ground). The detection circuit 13 is surrounded by the FP 52, and the detection circuit 13 is an FPC.
It is shielded by the ground shield 54 of 52.
Next, the operation will be described.

The FPC 52 of this embodiment is in an open state as shown in FIG. 11A before being attached to the fixing member 51. In this state, the FPC 52 is fixed to the upper surface of the fixing member 51 by soldering, and then the FPC 52 is bent along the bending line C-C to connect the wiring pattern 53 to each of the light receiving elements 8, 11 and 12. Therefore, the signals photoelectrically converted by the light receiving elements 8, 11, 12 are input to the detection circuit 13. Further, noise radiated from the outside is absorbed by the ground shield 54 and is blocked from the outside.

As described above, in this embodiment, the detection circuit 13 is set to F
The wiring pattern 53 for connecting the detection circuit 13 and each of the light receiving elements 8, 11, 12 and the ground shield 54 for connecting the ground of the detection circuit 13 and the fixing member 51 are provided inside the FPC 52 while being mounted on the PC 52. , The detection circuit 13 is surrounded by the FPC 52 by bending the FPC 52, so that the electromagnetic wave generated from the high frequency superposition circuit 23 is generated by the FPC 52.
Can be blocked by 52 ground shields 54,
It is possible to prevent the detection circuit 13 from being adversely affected. Further, since the detection circuit 13 is mounted on the FPC 52 and integrated, it is possible to reduce the number of parts.
(Substantially one component for blocking electromagnetic waves),
The assembling property can be improved, and an inexpensive optical pickup can be obtained.

[0036]

According to the first aspect of the present invention, it is possible to prevent the electromagnetic waves generated from the high frequency superposition circuit from being leaked to the outside by blocking the electromagnetic waves generated by the high frequency superposition circuit by the shielding portion of the flexible printed wiring board. It is possible to prevent adverse effects. Also, since the high-frequency superposition circuit is mounted on the flexible printed wiring board and integrated, it is possible to reduce the number of parts (substantially one part for preventing leakage) and to improve the assemblability. It is possible to obtain a good optical pickup and obtain an inexpensive optical pickup.

According to the second aspect of the present invention, since the shielding portion is made of amorphous (amorphous metal), it is possible to shield the electromagnetic wave more efficiently. According to the third aspect of the present invention, when the flexible printed wiring board is bent, solder land portions are provided on the opposing board portions around the high frequency superposition circuit, and the solder land portions are soldered. The high-frequency superposition circuit can be sealed by the flexible printed wiring board, and electromagnetic waves can be blocked at a higher level.

According to the fourth aspect of the invention, it is possible to prevent the detection circuit from being adversely affected by blocking the electromagnetic wave generated from the high frequency superposition circuit by the shielding portion of the flexible printed wiring board. Moreover, the detection circuit can be mounted on the flexible printed wiring board and integrated, so that the number of parts can be reduced (substantially only one part is provided for blocking electromagnetic waves), and assembly is also possible. It is possible to obtain a cheap optical pickup.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical pickup according to claim 1 or 2 and is a schematic diagram thereof.

FIG. 2 is a diagram showing a configuration of the high-frequency superimposing unit and its surroundings.

FIG. 3 is a configuration diagram of the high frequency superposition unit viewed from the direction A in FIG.

FIG. 4 is a development view of the FPC.

5 is a detailed view of a B part of the FPC in FIG.

FIG. 6 is a top view of an optical pickup having a separation optical system.

FIG. 7 is a schematic configuration diagram of the optical pickup.

FIG. 8 is a diagram showing an embodiment of the optical pickup according to claim 3 and is a diagram showing a configuration of a high-frequency superimposing unit and its periphery.

9A is a development view of the FPC, and FIG. 9B is a sectional view taken along the line DD of FIG. 9A.

FIG. 10 is a diagram showing an embodiment of the optical pickup according to claim 4, and is a configuration diagram of a detection circuit and its periphery.

11A is a development view of the FPC, and FIG. 11B is a perspective view in the E direction of FIG. 11A.

[Explanation of symbols]

 1 Semiconductor laser 2 Coupling lens 3 Beam splitter 4 Objective lens 5 Information recording medium 6 Condensing lens 7 Knife edge prism 8 Focus detection light receiving element 9 λ / 2 plate 10 Polarization beam splitter 11 Track detection / information signal detection light receiving element 12 Information Signal detection light receiving element 13 Detection circuit 14 High frequency superposition unit 22 Semiconductor laser control circuit (driving circuit) 23 High frequency superposition circuit 24, 31, 52 FPC 25, 53 Wiring pattern 26, 54 Ground shield (shielding part) 32 Solder land part 51 Fixed member (frame)

Claims (4)

[Claims] 1. A semiconductor laser, a high frequency superimposing circuit for emitting the semiconductor laser at a high frequency, a drive circuit for driving the high frequency superimposing circuit, and a flexible printed wiring board for connecting the drive circuit and the high frequency superimposing circuit. In the optical pickup, the laser light output from the semiconductor laser is condensed by an objective lens to form a spot on the information recording medium, and the reflected light is read by at least the detecting means. A high-frequency superimposing circuit is mounted at a predetermined position, and a wiring pattern for connecting the drive circuit and the high-frequency superimposing circuit, and a shield section for connecting the ground of the drive circuit and the high-frequency superimposing circuit are provided inside the substrate. By bending the flexible printed wiring board, a high frequency superposition circuit can be formed. An optical pickup characterized by being surrounded by a flexible printed wiring board. 2. The optical pickup according to claim 1, wherein the shield portion is made of an amorphous material. 3. When the flexible printed wiring board is bent, solder land portions are provided on opposing board portions around the high-frequency superposition circuit, and the solder land portions are soldered. Item 3. The optical pickup device according to item 1 or 2. 4. A semiconductor laser, a high frequency superimposing circuit for emitting the semiconductor laser at a high frequency, a drive circuit for driving the high frequency superimposing circuit, and a laser beam outputted from the semiconductor laser for condensing on an information recording medium. An objective lens that forms a spot, an optical system having a light receiving element that photoelectrically converts the reflected light from the information recording medium, and at least a recording medium based on the signal photoelectrically converted by the light receiving element. In an optical pickup comprising a detection circuit for reading the above information, the detection circuit is mounted at a predetermined location of a flexible printed wiring board, and inside the board, a wiring pattern for connecting the detection circuit and the light receiving element, The flexible printed wiring board is provided with a shield for connecting the ground of the detection circuit and the frame for mounting the flexible wiring board. An optical pickup characterized in that a detection circuit is surrounded by a flexible printed wiring board by bending the wiring board.