JP4032868B2 - Light quantity detector and optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light amount detector that receives light and detects the amount of light, and an optical pickup device that includes a laser light source and a light amount detector that detects the light amount of the laser light source.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an optical pickup device that irradiates a laser beam on an optical disc, a signal is written by irradiating the optical disc with a laser beam output from a laser light source, or a signal is read by receiving reflected light. By the way, in order to form an image of a laser beam on an optical disc, to record a signal satisfactorily, and to reproduce it satisfactorily, it is necessary to irradiate the optical disc with an appropriate intensity of the laser beam. However, the laser light source has a problem in that the output fluctuates due to changes in the ambient temperature or the like, and the light intensity of the laser light applied to the optical disk changes. Therefore, means for controlling the output of the laser light by monitoring the laser light output from the laser light source with a light amount detection element and adjusting the amount of electric power flowing into the laser light source based on the monitoring result is taken.
[0003]
FIG. 4 shows a configuration of an optical system of a conventional optical pickup device that irradiates an optical disc with laser light.
A beam (diverged light) emitted from the semiconductor laser light source 1 passes through the collimator lens 2 to become parallel laser light, is reflected by the rising mirror 3, passes through the objective lens 4, and reaches the optical disk 5. A light amount detector 6 is disposed in the vicinity of the diverging light path of the laser light source 1, and a part of the diverging beam is incident to detect the light amount of the laser light. In the drawing, the laser light is shown as reaching the light quantity detector 6 directly, but the laser light may be indirectly guided by a mirror or the like.
[0004]
In the optical pickup device, the light amount of the laser light is detected by the light amount detector 6, and the intensity of the laser light can be known from the detection result. Based on the detection output of the light quantity detector 6, a control unit (not shown) adjusts the inflow current to the semiconductor laser light source 1 to control the output intensity of the laser light.
[0005]
The light quantity detector 6 will be described in detail with reference to FIG. FIG. 5 is a diagram illustrating a circuit configuration included in the light amount detector 6.
The light amount detector 6 includes a light amount detection element U1 for receiving light and detecting the light amount, and a photodiode is generally used for the light amount detection element U1.
In the light amount detection element U1, the power supply voltage Vcc is applied as a reverse bias voltage on the forward direction side, and the reverse direction side is connected to the inversion side terminal of the operational amplifier U2. The operational amplifier U2 is supplied with a reference voltage Vref at a non-inversion side terminal, and applies an output side reference potential. A negative feedback circuit 61 is provided between the output terminal and the inverting terminal of the operational amplifier U2. The negative feedback circuit 61 includes a negative feedback resistor including a fixed resistor R1 and a variable resistor VR1 connected in series, and a capacitor C1 connected in parallel thereto.
[0006]
In this circuit configuration, when the photodiode U1 receives a beam emitted from the semiconductor laser light source 1, a current flows into the operational amplifier U2 according to the received light amount. In the operational amplifier U2, the voltage is output as a voltage dropped from the output voltage set to the reference voltage Vref by the voltage converted by R1 + VR1. That is, this circuit functions as a current-voltage conversion circuit and an amplifier circuit.
Among the beams emitted from the semiconductor laser light source 1, a part of the beam that does not reach the objective lens 4 reaches the light quantity detection element U1, but the positional deviation of the light quantity detection element or the emission angle variation of the semiconductor laser light source, The emission angle deviation or the like varies depending on individual differences. For this reason, even if the amount of beam light reaching the objective lens 4 is the same, the amount of light reaching the light amount detection element U1 varies depending on the individual. In order to control this, the feedback resistor section is composed of the fixed resistor R1 and the variable resistor VR1 as described above, and copes with the variation by adjusting the resistance value of the variable resistor VR1. The capacitor C1 performs waveform trimming by phase compensation.
[0007]
[Problems to be solved by the invention]
By the way, in the negative feedback circuit, if the feedback amount differs, the frequency / phase characteristics also change. Therefore, if the change amount of VR1 is too large, the waveform of the phase compensation capacitor C1 set in advance is sufficiently trimmed. There is a problem that it becomes impossible. On the other hand, if the change amount of VR1 is limited to a small amount, it is not possible to sufficiently cope with the above-mentioned variation, and depending on the individual, adjustment becomes impossible and there is a problem that the product cannot be used.
[0008]
The present invention has been made against the background of the above circumstances, and an object thereof is to provide a light amount detector and an optical pickup device capable of appropriately adjusting light amount detection with respect to individual variations.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 of the light quantity detector of the present invention comprises a light quantity detection element and variable resistance means for adjusting an output value from the light quantity detector, and the variable resistance means is fixed. It comprises a resistor and a variable resistor, and the fixed resistor is replaceable from the outside, and the variable resistor is disposed in a space where the resistance value can be adjusted from the outside. And
[0010]
According to a second aspect of the present invention, the light quantity detector includes an amplifier that amplifies and outputs an input from the light quantity detection element according to the first aspect of the invention.
[0011]
According to a third aspect of the present invention, there is provided the light amount detector according to the second aspect, wherein the variable resistance means is a negative feedback resistor provided in a negative feedback circuit of the amplifier.
[0012]
According to a fourth aspect of the present invention, there is provided the light quantity detector according to the third aspect, wherein the negative feedback circuit includes a capacitor.
[0013]
6. An optical pickup device according to claim 5, comprising a laser light source for generating laser light, and irradiating the optical disk with laser light emitted from the laser light source to read or / and write information on the optical disk. A pickup circuit comprising the light amount detector according to any one of claims 1 to 4 that receives a part of the laser light and detects a light amount, and a printed circuit board on an outer surface portion of the unitized optical pickup device. The variable resistance means of the light quantity detector is mounted on the outer surface printed circuit board.
[0014]
According to a sixth aspect of the present invention, in the invention of the fifth aspect, a capacitor included in a negative feedback circuit of the light amount detector is mounted on an outer printed circuit board.
[0015]
That is, according to the present invention, the variable resistance means for adjusting the output value can be arranged in a space operable from the outside, and if necessary, the resistance value of the variable resistor of the variable resistance means can be adjusted, The fixed resistor can be replaced with one having a different resistance value.
As a result, the changeable range of the variable resistor means can be increased, while the adjustment range of the variable resistor is suppressed to an appropriate range to ensure that the light quantity detector operates satisfactorily.
[0016]
In the present invention, the variable resistance means can be arranged in a space operable from the outside. For this reason, the variable resistance means can be arranged at an appropriate place without being restricted by the arrangement position of the light quantity detection element. In order to achieve the above, the variable resistance means is usually not arranged in the same space as the member such as the light quantity detection element, but is arranged in a different space through an appropriate wiring means (flexible printed wiring board etc.). To do. When the light quantity detector is provided in an optical pickup device or the like, for example, the arrangement of the light quantity detector is restricted by receiving a part of the laser light in relation to the optical component. Regardless of the position of the light amount detector, it can be arranged in a space where the fixed resistor can be replaced and the resistance value of the variable resistor can be adjusted, such as the outer surface of a unitized device.
[0017]
The variable resistance means may be any means as long as it can adjust the output value of the light quantity detector, and can be provided at an appropriate location in the circuit. A typical example is one used as a negative feedback resistor provided in a negative feedback circuit of an amplifier. In the negative feedback circuit, since the amplification factor in the amplifier changes by changing the value of the negative feedback resistor, the output value in the light amount detector can be adjusted.
In the negative feedback resistor, a phase compensation capacitor can be used to trim the output waveform. When the variable resistance means is arranged in an operable space, it is desirable to arrange this capacitor in the same space, and this capacitor can be replaced with one having a different capacity if desired. As a result, when the fixed resistor of the variable resistance means is replaced, the capacitor can be replaced and the output waveform can be sufficiently trimmed to improve the output waveform shaping accuracy.
[0018]
The light quantity detector of the present invention can be applied to an optical pickup device that performs only optical reproduction or optical recording / reproduction with respect to an optical disc. In an optical reproducing apparatus or an optical recording / reproducing apparatus provided with the optical pickup device, recording or / and reproducing on an optical disc can be performed accurately and without error by appropriately controlling the output of the laser light source.
[0019]
The light quantity detector of the present invention can be preferably applied to the optical pickup device as described above, but the application field is not limited to the optical pickup device as the present invention. In other words, the present invention can be applied to various fields where it is necessary to detect the amount of light in light having different wavelengths.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an optical component layout in an optical pickup device for an optical disk. In addition, in this embodiment, the same code | symbol is attached | subjected about the structure similar to the past, and description is abbreviate | omitted or simplified.
[0021]
The divergent light emitted from the semiconductor laser light source 1 passes through the collimator lens 2 and becomes parallel light as in the conventional apparatus. Further, the laser light is reflected by the rising mirror 3 and passes through the objective lens 4 and is irradiated onto an optical disk (not shown). In signal reproduction, reflected light reflected by the optical disk is received by a light receiving device (not shown) and processed. And the light quantity detector 6 of this invention is arrange | positioned so that a part of diverging light may enter into the space near the diverging light path 1a.
[0022]
The light quantity detector 6 has a circuit that converts the current signal output from the light quantity detection element U1 into a voltage signal, and amplifies and outputs the voltage signal to a level required by the control system in the subsequent stage. The circuit configuration is the same as that of the conventional apparatus shown in FIG. The output of the light amount detector 6 is output to a control unit (not shown) that controls the output of the laser light source 1, and the control unit, based on the output value from the light amount detector 6 obtained according to the light amount, The output of the laser light source 1 is controlled.
[0023]
In the light amount detector 6, as shown in FIG. 1, together with the optical components such as the semiconductor laser light source 1 except for the fixed resistor R1, the variable resistor VR1, and the phase compensation capacitor C1, which constitute the negative feedback circuit 61. Built in the unit 10.
On the other hand, the negative feedback circuit 61 is disposed so as to be exposed to the outer side surface 10a of the unit 10 through a flexible printed wiring board 62 as wiring means.
[0024]
In the optical pickup device, the values of VR1 and C1 are set so that the waveform is trimmed well by the phase compensation capacitor C1 in accordance with the variable width of the variable resistor VR1. Then, if necessary, the sensitivity of the light amount detector of the photodetector 6 is adjusted according to individual variations by manipulating the variable resistor VR1 exposed on the outer surface 10a, and the output of the laser light source 1 is appropriately set. adjust. If the specification falls within the variable width of the variable resistor VR1, the adjustment operation is terminated.
[0025]
On the other hand, when it is difficult to adjust the variable resistor VR1 so as to be within the variable width, the variable width of the variable resistor VR1 is changed again by replacing R1 provided on the outer surface 10a with one having a different resistance value. Adjust the sensitivity within the range, and finish the sensitivity adjustment within specifications. Further, after the fixed resistor R1 is replaced, the phase compensation capacitor C1 optimized by the fixed resistor R1 is replaced with a capacitor having a different capacity as necessary. In other words, the combination of the fixed resistor R1 and the phase compensation capacitor C1 is set to an optimum combination in advance, and the phase compensation capacitor C1 is changed when the combination becomes non-optimal by changing the fixed resistor R1. To do. The replacement work of these resistors and capacitors and the adjustment work of the variable resistor can be performed on the outer surface of the unit 10 and can be easily performed. The workability can be achieved by mounting these members on the outer surface. Has increased significantly.
[0026]
【The invention's effect】
As described above, according to the light quantity detector of the present invention, the light quantity detection element and the variable resistance means for adjusting the output value from the light quantity detector are provided, and the variable resistance means includes a fixed resistor and a variable resistor. The fixed resistor can be replaced from the outside, and the variable resistor is arranged in a space in which the resistance value can be adjusted from the outside. It can be enlarged and adjusted quickly, and the shaping accuracy of the output waveform can be increased depending on the circuit configuration.
In addition, according to the optical pickup device of the present invention, the above optical quantity detector is provided, and an excellent optical pickup performance is obtained by appropriately adjusting the output intensity of the laser light source according to the output of the appropriately adjusted quantity detector. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual front view of an optical pickup device of the present invention.
FIG. 2 is a side view of the same.
FIG. 3 is an enlarged side view of the same.
4A and 4B are a plan view and a front view showing an optical system layout of a conventional optical pickup device.
FIG. 5 is a diagram similarly showing a circuit of a light quantity detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor laser light source 2 Collimating lens 3 Raising mirror 4 Objective lens 5 Optical disk 6 Light quantity detector 60 Light quantity detection element 61 Negative feedback circuit 62 Flexible printed wiring board U1 Light quantity detection element U2 Operational amplifier VR1 Variable resistor R1 Fixed resistor C1 Phase Compensation capacitor E0 output voltage

Claims (6)

It comprises a light quantity detection element and variable resistance means for adjusting the output value from the light quantity detector. The variable resistance means comprises a fixed resistor and a variable resistor, and the fixed resistor can be replaced from the outside. And the variable resistor is disposed in a space in which a resistance value can be adjusted from the outside . 2. The light quantity detector according to claim 1, further comprising an amplifier that amplifies and outputs an input from the light quantity detection element. 3. The light quantity detector according to claim 2, wherein the variable resistance means is a negative feedback resistor provided in a negative feedback circuit of the amplifier. 4. The light quantity detector according to claim 3, wherein the negative feedback circuit includes a capacitor. An optical pickup device that includes a laser light source that generates laser light, irradiates the optical disk with laser light emitted from the laser light source, and reads or / and writes information on the optical disk. 5. The light amount detector according to claim 1, wherein the light amount detector according to any one of claims 1 to 4 that receives a part of the printed circuit board is disposed, and a part of a printed circuit board is disposed on an outer surface portion of a unitized optical pickup device. An optical pickup device, wherein the variable resistance means of the device is mounted on the outer printed circuit board.   6. The optical pickup device according to claim 5, wherein a capacitor included in a negative feedback circuit of the light amount detector is mounted on an outer printed circuit board.

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