JP2009199669A - Photodetector, optical pickup, and optical recording and reproduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetector that is improved in low-noise operating characteristics. <P>SOLUTION: A disclosed photodetector 1 is used in an optical pickup for generating a signal from a light beam being emitted from a semiconductor laser and reflected on an optical disk. The photodetector includes a plurality of photodiodes PD1<SB>A</SB>, PD1<SB>B</SB>, PD1<SB>C</SB>and PD1<SB>D</SB>, a signal adder 13, and a plurality of current detectors 12A-12D. The photodiode PD1<SB>A</SB>, PD1<SB>B</SB>, PD1<SB>C</SB>, PD1<SB>D</SB>receives reflected light from the optical disk, and outputs respective light receiving currents I<SB>A</SB>, I<SB>B</SB>, I<SB>C</SB>, I<SB>D</SB>. The signal adder 13 adds the light receiving currents I<SB>A</SB>, I<SB>B</SB>, I<SB>C</SB>, I<SB>D</SB>. Respective current detectors 12A-12D are provided corresponding to photodiodes PD1<SB>A</SB>, PD1<SB>B</SB>, PD1<SB>C</SB>, PD1<SB>D</SB>, so as to detect respective light receiving currents I<SB>A</SB>, I<SB>B</SB>, I<SB>C</SB>, I<SB>D</SB>of the respective photodiodes PD1<SB>A</SB>, PD1<SB>B</SB>, PD1<SB>C</SB>, PD1<SB>D</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used in an optical pickup for recording or reproducing information on an optical disk such as a CD (Compact Disk), a DVD (Digital Versatile Disk), or a Blu-ray Disc (registered trademark), and is reflected by the optical disk. Photodetector (OEIC: Optical Electrical Integrated) having a light receiver (photoelectric element) that receives a light beam and an electronic circuit that processes both an optical signal and an electrical signal output from the light receiver. Circuit), an optical pickup provided with the optical detection device, and an optical recording / reproducing apparatus equipped with the optical pickup.

  In an optical pickup equipped with a conventional light detection device, the center of the light spot is placed in a photodetector that receives a light beam collected by an objective lens in order to reduce noise contained in light reflected from an optical disk. A set of light receivers including a predetermined number of inner light receivers that receive the light and a predetermined number of outer light receivers that are provided so as to surround the outer side of the inner light receiver and that receive the periphery of the light spot. Some have a body. This optical pickup includes an I-V amplifier (current-voltage conversion amplifier) that converts a current signal generated according to the amount of light received by each light receiver into a calculation signal provided in the subsequent stage of the photodetector and then converts it to a voltage signal. (For example, refer to Patent Document 1). Hereinafter, this technique is referred to as a first conventional example.

  Further, in the conventional photodetector, in order to reduce the amplifier noise of the reproduction signal detection system without complicating the optical system, the light beam is received by a light receiving element having a plurality of light receiving elements or a plurality of divided light receiving regions. In some cases, after receiving light, each received light signal is converted from current to voltage. This photodetector includes switching means for switching whether a part or all of a plurality of received light signals are added before current-voltage conversion, or whether each received light signal is directly converted into current-voltage without adding current. (For example, refer to Patent Document 2). Hereinafter, this technique is referred to as a second conventional example.

Japanese Patent Laid-Open No. 11-162003 JP 2006-59428 A

  In the first conventional example described above, the structure of the light receiver is divided by a physical and manufacturing process method to generate RF signals and servo signals for each light receiving section (channel) at the same time. Not assigned to RF signal. As a result, there is a problem that S / N deteriorates and the advantage of current addition cannot be fully utilized. Further, the first conventional example described above has a problem that it is necessary to change the structure of the light receiver in a physical and process manner.

On the other hand, in the second conventional example described above, switching is performed between whether or not a part or all of a plurality of light reception signals are subjected to current addition before current-voltage conversion, or each light reception signal is subjected to current-voltage conversion without adding current. Therefore, there is a problem that it is not possible to simultaneously obtain the RF signal for current addition and the servo signal of each light receiving unit (channel).
From the above, the first and second conventional examples described above have a problem that the low noise operation characteristics are not particularly good.

  The present invention has been made in view of the above-described circumstances, and an example of an object is to solve the above-described problems, and a photodetecting device and an optical pickup that can solve these problems And an optical recording / reproducing apparatus.

  In order to solve the above-described problem, a light detection device according to a first aspect of the present invention is a light detection device used for an optical pickup that generates a signal from a light beam emitted from a light source and reflected by an optical recording medium. A plurality of photodiodes that receive reflected light from the optical recording medium and output a light receiving current; a signal adder that adds the light receiving currents of the plurality of photodiodes; and a plurality of photodiodes. And a plurality of current detectors for detecting the light receiving currents of the corresponding photodiodes.

According to a thirteenth aspect of the present invention, an optical pickup includes the photodetection device according to any one of the first to twelfth aspects.
An optical recording / reproducing apparatus according to the invention described in claim 14 is characterized in that the optical pickup according to claim 13 is mounted.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 1 according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing an example of the arrangement of the light receiving surfaces of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D constituting the four-divided light receiver (four quadrant light receiver) 11 shown in FIG. . The photodetector 1 according to the first embodiment has a configuration that should be called a current addition type. The light detection device 1 includes a four-divided light receiver (four-quadrant light receiver) 11, current detectors 12 </ b> A, 12 </ b> B, 12 </ b> C and 12 </ b> D, and a signal adder 13.

The four-divided light receiver 11 has four light receiving areas A, B, C, and D. Four light receiving regions A, B, C and D is composed of a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, respectively. The quadrant light receiver 11 is an anode common type in which the anodes of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D are connected in common and grounded. The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive a light beam (main beam) reflected by an optical disk 2 (see FIG. 3) described later, and receive light currents I _A , I _B , I _{C respectively.} And _ID are output.

Current detector 12A, 12B, 12C and 12D are provided corresponding to the photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D. The current detectors 12A, 12B, 12C and 12D detect the light receiving currents I _A , I _B , I _C and I _D output from the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D , respectively. receiving current I _a, I _B, I _C and I _D for each linearly varying voltage signals V _a, V _B, and outputs a V _C and V _D to. These voltage signals V _A , V _B , V _C and V _D are supplied to a signal processing circuit 7 (see FIG. 3) which will be described later.

In the current detectors 12A, 12B, 12C and 12D described above, the linearity when the received light currents I _A , I _B , I _C and I _D are converted into the corresponding voltage signals V _A , V _B , V _C and V _D. The characteristic is a basic characteristic required for the photodetection device (OEIC) 1. That is, changes in the light receiving currents I _A , I _B , I _C, and I _D are information necessary for focusing and tracking control (servo control) of the optical pickup 2, and corresponding voltage signals V _A , V _B , V _C And that information needs to be maintained after conversion to V _D. Therefore, each voltage signal V _A , V _B , V _C and V _D changes linearly with respect to the corresponding received light currents I _A , I _B , I _C and I _D, so that the signal processing circuit 7 can accurately Servo signal processing can be performed, and the optical recording / reproducing apparatus is established as an optical recording / reproducing apparatus.

The signal adder 13 adds the light receiving currents I _A , I _B , I _C and I _D output from the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D , respectively, to obtain an RF current signal I _RF . The RF current signal I _RF is converted into an RF voltage signal V _RF and output. That is, the signal adder 13 also functions as an IV amplifier (current / voltage conversion amplifier).

  In addition to the above components, the photodetector 1 is actually emitted from two sub-receivers that receive two sub-beams and each sub-receiver in order to obtain a tracking error signal TE described later. A circuit for processing the received light current. However, since these components are not directly related to the features of the present invention, the description thereof is omitted.

  Next, the configuration of the optical pickup 2 provided with the photodetecting device 1 shown in FIG. 1 and the optical recording / reproducing apparatus equipped with the optical pickup 2 will be described with reference to FIG. The optical recording / reproducing apparatus is an optical reproducing apparatus that reads and reproduces information recorded on an optical recording medium, an optical recording apparatus that records information to be recorded on an optical recording medium, or an apparatus having both functions. In the first embodiment, a case of an optical disk recording / reproducing apparatus (hereinafter referred to as “optical disk apparatus”) using the optical disk 3 as an optical recording medium will be described as an example.

  This optical disk apparatus is roughly composed of an optical pickup 2, a controller 4, a laser driver 5, a diffraction unit driver 6, a signal processing circuit 7, an equalizer 8, and a pickup driver (PU driver) 9. ing. The optical pickup 2 includes the above-described optical detection device (OEIC) 1, a semiconductor laser 21 as a light source, a diffraction unit 22, a half mirror 23, an objective lens 24, and a condenser lens 25. The optical pickup 2 includes an actuator that performs focusing and tracking adjustment, although not shown.

  The controller 4 controls the entire optical disk device. For example, the controller 4 generates a connection mode designation signal MC according to a predetermined algorithm, setting, etc., and supplies it to the signal processing circuit 7. Further, the controller 4 generates a laser drive signal LDD corresponding to the laser drive signal LDD for reading information from the optical disc 3 or the information signal WD related to information to be recorded on the optical disc 3 supplied from the outside, and the laser driver 5 is supplied. The laser driver 5 drives the semiconductor laser 21 based on the laser drive signal LDD.

  The light beam emitted from the semiconductor laser 21 enters the diffraction unit 22 that functions as a multi-beam generating element. The diffraction unit 22 includes a diffraction element made of, for example, a liquid crystal polymer (LCP). The controller 4 supplies the diffraction unit drive signal DUD to the diffraction unit driver 6. The diffraction unit 22 is driven by the diffraction unit driver 6, splits and generates a light beam emitted from the semiconductor laser 21 into three light beams, and supplies the light beam to the half mirror 23.

  An actuator (not shown) is coupled to the diffraction unit 22. When this actuator is driven by the diffraction unit driver 6, beam adjustments such as generation of three light beams and beam position adjustment are performed. The half mirror 23 guides the main beam and the two sub beams divided and generated by the diffraction unit 22 to the objective lens 24. The objective lens 24 collects these beams and irradiates the information recording surface of the optical disc 3.

Specifically, the beam spot of the main beam is irradiated so as to be positioned on the recording track of the optical disc 3. At this time, the three reflected light beams reflected by the optical disk 3 are guided to the light detection device 1 through the objective lens 24, the half mirror 23, and the condenser lens 25. The photodetector 1 performs the above-described processing, generates an RF voltage signal V _RF , voltage signals V _A , V _B , V _C, V _{D and the} like, and supplies them to the signal processing circuit 7.

Based on the RF voltage signal V _RF , the voltage signals V _A , V _B , V _C, and V _D supplied from the light detection device 1, the signal processing circuit 7 performs a focus error signal FE, a tracking error signal TE, A beam adjustment signal BA, a read signal RS, and the like are generated. The signal processing circuit 7 supplies the read signal RS to an external circuit (not shown) that performs processing such as reproduction and storage of the read signal RS, and supplies a beam adjustment signal BA to the controller 4. Further, the signal processing circuit 7 supplies a focus error signal FE and a tracking error signal TE to the equalizer 8.

  Under the control of the controller 4, the equalizer 8 generates a drive signal for an actuator (not shown) included in the optical pickup 2 and supplies the drive signal to the PU driver 9. The PU driver 9 drives an actuator (not shown) included in the optical pickup 2 based on the supplied drive signal. Thereby, focusing and tracking control (servo control) of the optical pickup 2 is performed.

  In addition, you may comprise so that the photodetection apparatus may fulfill | perform all or one part of the signal processing circuit 7. FIG. Some functions include, for example, a function that generates a focus error signal FE, a tracking error signal TE, and the like.

  Next, the noise level in the current addition type photodetector 1 having the above configuration is compared with the noise level in the conventional photodetector 31 shown in FIG. 4, parts corresponding to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. The photodetection device 31 has a configuration to be called a voltage addition type. This photodetector 31 has a four-divided photodetector (four quadrant photodetector) 11 as well as the photodetector 1 shown in FIG. 1, and IV amplifiers (current-voltage conversion amplifiers) 32A, 32B, 32C, and 32D. And a signal adder 33.

I-V amplifier 32A, 32B, 32C and 32D are provided corresponding to the photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D. The I-V amplifiers 32A, 32B, 32C and 32D respectively apply the received light currents I _A , I _B , I _C and I _D output from the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D to the voltage signal V Convert to _A , V _B , V _C and V _D and output. The signal adder 33 adds the voltage signals V _A , V _B , V _C and V _D and outputs the result as an RF voltage signal V _RF .

Here, the noise levels of the outputs of the respective IV amplifiers 32A, 32B, 32C and 32D are all set to N, the gain of the signal adder 33 is set to 4, and the noise level of the output of the photodetector 31 is set to NRF1. In this case, the noise level NRF1 is the product of the mean square value of the noise levels of the outputs of the four IV amplifiers 32A, 32B, 32C, and 32D and the gain of the signal adder 33. expressed.
NRF1 = 4 × √ {(N / 4) ² + (N / 4) ² + (N / 4) ² + (N / 4) ² }
= 2N (1)

Hereinafter, the reason why the noise level NRF1 is expressed by the equation (1) will be described. For example, the noise level N of the I-V amplifier 32A is {N × (1/4)} at the positive input terminal of the signal adder 33 due to resistance division of the addition resistor. Since this noise level {N × (1/4)} is added for four channels of the IV amplifiers 32A, 32B, 32C and 32D, the noise level NRF1 (+) at the positive input terminal of the signal adder 33 is These are the root mean square and are expressed by equation (2).
NRF1 (+) = √ {(N / 4) ² + (N / 4) ² + (N / 4) ² + (N / 4) ² }
= N / 2 (2)
In the signal adder 33, the noise level NRF1 (+) at the positive input terminal is amplified by the gain of the signal adder 33 (in this case, gain 4). From the above, the noise NRF1 output from the signal adder 33 is expressed by the above equation (1).

On the other hand, in the photodetector 1 according to the first embodiment shown in FIG. 1, the noise level of the output as the IV amplifier of the signal adder 13 is N, and the noise level of the output of the photodetector 1 is set to N. In the case of NRF2, since the noise level NRF2 is equal to the noise level N of the output as the IV amplifier of the signal adder 13, it is expressed by Expression (3).
NRF2 = N (3)

Equation (4) is derived from Equation (1) and Equation (3).
NRF2 = (1/2) · NRF1 (4)
From the above, the noise level NRF2 of the output of the photodetection device 1 of the current addition type is ½ of the noise level NRF1 of the output of the conventional photodetection device 31 of the voltage addition type, that is, at least −. Noise reduction of 6 dB is possible.

As described above, the photodetector 1 according to the first embodiment of the present invention provides the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetecting device 1 includes photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D , current detectors 12A, 12B, 12C and 12D, and a signal adder 13.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. Current detector 12A, 12B, 12C and 12D are received photocurrent I _A, I _B, detects the I _C and I _D, the corresponding light-receiving current I _A, I _B, respectively linearly to I _C and I _D The changing voltage signals V _A , V _B , V _C and V _D are output. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the first embodiment of the present invention, servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the first embodiment of the present invention, it is possible to convert all the received light currents I _A , I _B , I _C and I _D into the RF voltage signal V _RF . Furthermore, according to the first embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Embodiment 2. FIG.
FIG. 5 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 41 according to Embodiment 2 of the present invention. In FIG. 5, parts corresponding to those in FIG. 1 are given the same reference numerals, and explanation thereof is omitted. In the photodetector 41 shown in FIG. 5, instead of the current detectors 12A, 12B, 12C and 12D shown in FIG. 1, voltage detectors 42A, 42B, 42C and 42D and detection resistors Ra, Rb, Rc and Rd are provided. Newly provided. In other words, the current detector 12A is constituted by the voltage detector 42A and the detection resistor Ra, and the current detector 12B is constituted by the voltage detector 42B and the detection resistor Rb. Similarly, the current detector 12C includes a voltage detector 42C and a detection resistor Rc, and the current detector 12D includes a voltage detector 42D and a detection resistor Rd. That is, the photodetection device 41 according to the second embodiment has a configuration that should be called a current addition type, similarly to the photodetection device 1 according to the first embodiment. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus in which the optical pickup 2 is mounted, a light detection device 41 is newly provided in place of the light detection device 1.

Voltage detector 42A~42D and detection resistor Ra, Rb, Rc and Rd are provided corresponding to the photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D. The input impedance of the voltage detectors 42A, 42B, 42C and 42D needs to be high impedance. The first input terminals of the voltage detectors 42A, 42B, 42C and 42D are connected to the negative input terminal of the signal adder 13, respectively. Each detection resistor Ra, Rb, Rc and Rd is a voltage detector 42A corresponding to the negative input terminal of the signal adder 13 and the corresponding cathodes of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D. , 42B, 42C, and 42D, which are inserted between the connection points of the respective second input terminals, that is, the current paths of the respective photodiodes PD1 _A , PD1 _B , PD1 _C, and PD1 _D before the current addition. Yes.

The voltage detectors 42A, 42B, 42C and 42D are respectively connected to the corresponding detection resistors Ra, Rb by the received light currents I _A , I _B , I _C and I _D flowing through the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D. , Rc and Rd are input to detect and amplify voltage drops generated at both ends, and voltage signals V _A , V _B , V _C and V _D which change linearly with respect to the voltage drops are output. These voltage signals V _A , V _B , V _C and V _D are supplied to the signal processing circuit 7 shown in FIG. The noise level in the current addition type photodetecting device 41 having the above-described configuration is the same as that of the photodetecting device 1 according to the above-described first embodiment, and thus the description thereof is omitted.

In the current detectors 42A, 42B, 42C and 42D described above, the voltage signal V corresponding to the voltage drop caused by the detection resistors Ra, Rb, Rc and Rd corresponding to the light receiving currents I _A , I _B , I _C and _ID. The linearity when outputting as _A , V _B , V _C and V _D is a basic characteristic required for the photodetection device (OEIC) 1. That is, the change in voltage drop caused by the detection resistors Ra, Rb, Rc, and Rd corresponding to the light receiving currents I _A , I _B , I _C, and I _D is necessary for focusing and tracking control (servo control) of the optical pickup 2. This is information, and the information needs to be maintained in the output voltage signals V _A , V _B , V _C and V _D. Therefore, each voltage signal V _A , V _B , V _C and V _D corresponds to the voltage drop caused by the corresponding detection currents I _A , I _B , I _C and I _D and the corresponding detection resistors Ra, Rb, Rc and Rd. By changing linearly, the signal processing circuit 7 can perform accurate servo signal processing, and the optical recording / reproducing apparatus is established as an optical recording / reproducing apparatus.

As described above, the photodetector 41 according to the second embodiment of the present invention is the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 41 includes photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D , voltage detectors 42A, 42B, 42C and 42D, detection resistors Ra, Rb, Rc and Rd, a signal adder 13, have.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The voltage detectors 42A, 42B, 42C, and 42D receive and detect and amplify voltage drops generated across the corresponding detection resistors Ra, Rb, Rc, and Rd, and voltage signals V _A , V _B , V _C, and V _D is output. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the second embodiment of the present invention, the servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the second embodiment of the present invention, all the received light currents I _A , I _B , I _C and I _D can be converted into the RF voltage signal V _RF . Furthermore, according to the second embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Embodiment 3 FIG.
FIG. 6 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 51 according to Embodiment 3 of the present invention. In FIG. 6, parts corresponding to those in FIG. In the photodetector 51 shown in FIG. 6, non-inverting amplifiers 52A, 52B, 52C and 52D are newly provided in place of the voltage detectors 42A, 42B, 42C and 42D shown in FIG. The light detection device 51 according to the third embodiment has a configuration that should be called a current addition type, like the light detection devices 1 and 41 described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus in which the optical pickup 2 is mounted, a light detection device 51 is newly provided in place of the light detection device 1.

The non-inverting amplifiers 52A, 52B, 52C and 52D are provided corresponding to the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D. Each positive input terminal of the noninverting amplifier 52A, 52B, 52C and 52D are corresponding photodiodes PD1 _A, PD1 _B, PD1 _C and PD1 detection resistor Ra and the corresponding respective cathodes of _D, Rb, and Rc and Rd Connected to each connection point. A reference voltage V _ref is applied to each negative input terminal of the non-inverting amplifiers 52A, 52B, 52C and 52D.

The non-inverting amplifiers 52A, 52B, 52C and 52D respectively detect the detection resistors Ra corresponding to the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D with respect to the reference voltage V _ref applied to each negative side input terminal. , Rb, Rc, and Rd are input and amplified, and voltage signals V _A , V _B , V _C, and V _D that change linearly with respect to the voltages are output. The voltage signals V _A , V _B , V _C and V _D are on the negative side with respect to the reference voltage V _ref . These voltage signals V _A , V _B , V _C and V _D are supplied to the signal processing circuit 7 shown in FIG. The noise level in the current addition type photodetecting device 51 having the above-described configuration is the same as that of the photodetecting device 1 according to the first embodiment, and a description thereof will be omitted.

As described above, the photodetector 51 according to the third embodiment of the present invention is an optical pickup 2 that reproduces a signal from a light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 51 comprises a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, a non-inverting amplifier 52A, 52B, and 52C and 52D, the detection resistor Ra, Rb, and Rc and Rd, and the signal adder 13 have.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The non-inverting amplifiers 52A, 52B, 52C and 52D are connected to the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D and the corresponding detection resistors Ra, Rb, Rc and Rd for each reference voltage V _ref . Is input and amplified to output voltage signals V _A , V _B , V _C and V _D. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to Embodiment 3 of the present invention, servo signals for the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the third embodiment of the present invention, it is possible to convert all the received light currents I _A , I _B , I _C and I _D into the RF voltage signal V _RF . Furthermore, according to the third embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Embodiment 4 FIG.
FIG. 7 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 61 according to Embodiment 4 of the present invention. In FIG. 7, parts corresponding to those in FIG. 6 are given the same reference numerals, and explanation thereof is omitted. In the photodetector 61 shown in FIG. 7, inverting amplifiers 62A, 62B, 62C, and 62D are newly provided at the output terminals of the non-inverting amplifiers 52A, 52B, 52C, and 52D shown in FIG. The light detection device 61 according to the fourth embodiment has a configuration that should be called a current addition type, like the light detection devices 1, 41, and 51 described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus equipped with the optical pickup 2, a photodetecting device 61 is newly provided in place of the photodetecting device 1.

Inverting amplifier 62A, 62B, 62C and 62D are provided corresponding to the photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, a non-inverting amplifier 52A, 52B, 52C and 52D and the detection resistor Ra, Rb, Rc and Rd It has been. The respective output terminals of the corresponding non-inverting amplifiers 52A, 52B, 52C and 52D are connected to the input resistors Ri constituting the inverting amplifiers 62A, 62B, 62C and 62D, respectively.

The inverting amplifiers 62A, 62B, 62C, and 62D invert and amplify the output voltages of the corresponding non-inverting amplifiers 52A, 52B, 52C, and 52D with the amplification degree (Rf / Ri) determined by the feedback resistor Rf and the input resistor Ri. Signals V _A , V _B , V _C and V _D are output. The voltage signals V _A , V _B , V _C and V _D are on the positive side with respect to the reference voltage V _ref . These voltage signals V _A , V _B , V _C and V _D are supplied to the signal processing circuit 7 shown in FIG. The noise level in the current addition type photodetecting device 61 having the above-described configuration is the same as that of the photodetecting device 1 according to the first embodiment, and a description thereof will be omitted.

As described above, the photodetector 61 according to the fourth embodiment of the present invention is an optical pickup 2 that reproduces a signal from a light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 61 comprises a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, a non-inverting amplifier 52A, 52B, and 52C and 52D, the inverting amplifier 62A, 62B, and 62C and 62D, the detection resistor Ra, Rb , Rc and Rd, and a signal adder 13.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The non-inverting amplifiers 52A, 52B, 52C and 52D are connected to the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D and the corresponding detection resistors Ra, Rb, Rc and Rd for each reference voltage V _ref . The voltage at is input, amplified and output. The inverting amplifiers 62A, 62B, 62C, and 62D invert and amplify the output voltages of the corresponding non-inverting amplifiers 52A, 52B, 52C, and 52D with the amplification degree (Rf / Ri), and the voltage signals V _A , V _B , V _C And V _D are output. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the fourth embodiment of the present invention, servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the fourth embodiment of the present invention, it is possible to convert all the received currents I _A , I _B , I _C and I _D into the RF voltage signal V _RF . Furthermore, according to the fourth embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Embodiment 5 FIG.
FIG. 8 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 71 according to Embodiment 5 of the present invention. In FIG. 8, parts corresponding to those in FIG. In the photodetector 71 shown in FIG. 8, instead of the voltage detectors 42A, 42B, 42C and 42D shown in FIG. 5, gm amplifiers (transconductance amplifiers) 72A, 72B, 72C and 72D and IV amplifiers (currents) Voltage conversion amplifiers) 73A, 73B, 73C and 73D are newly provided. The light detection device 71 according to the fifth embodiment has a configuration that should be called a current addition type, like the light detection devices 1, 41, 51, and 61 described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus equipped with the optical pickup 2, a photodetection device 71 is newly provided in place of the photodetection device 1.

gm amplifier 72A, 72B, 72C and 72D, as well as I-V amplifier 73A, 73B, 73C and 73D, the photo diode PD1 _A, PD1 _B, PD1 _C and PD1 _D and detection resistor Ra, Rb, corresponding to the Rc and Rd Is provided. Each negative side input terminal of the gm amplifiers 72A, 72B, 72C and 72D is connected to a connection point between the negative side input terminal of the signal adder 13 and the corresponding detection resistors Ra, Rb, Rc and Rd. gm amplifier 72A, 72B, each positive input terminal of the 72C and 72D, the corresponding photodiode PD1 _A, PD1 _B, PD1 _C and PD1 detection resistor Ra and the corresponding respective cathodes of _D, Rb, connected to the Rc and Rd Each point is connected.

The input voltages at the negative input terminals of the gm amplifiers 72A, 72B, 72C and 72D are determined by the reference voltage V _R1 of the signal adder 13. However, the gm amplifiers 72A, 72B, 72C and 72D are not affected by the reference voltage V _R1 of the signal adder 13, and receive light current I _A flowing through the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D. , I _B , I _C, and I _D detect and amplify only the voltage drop generated at both ends of the corresponding detection resistors Ra, Rb, Rc, and Rd, and convert and output the current signal.

The IV amplifiers 73A, 73B, 73C, and 73D convert the current signals of the corresponding gm amplifiers 72A, 72B, 72C, and 72D into voltage signals V _A , V _B , V _C, and V _D and output them. The voltage signals V _A , V _B , V _C and V _D are on the positive side with respect to the reference voltage V _R2 . These voltage signals V _A , V _B , V _C and V _D are supplied to the signal processing circuit 7 shown in FIG. Note that the noise level in the current addition type photodetection device 71 having the above configuration is the same as that of the photodetection device 1 according to the first embodiment described above, and thus the description thereof is omitted.

As described above, the photodetector 71 according to the fifth embodiment of the present invention is used in the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 71 comprises a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, gm amplifier 72A, 72B, and 72C and 72D, I-V amplifier 73A, 73B, and 73C and 73D, the detection resistor Ra, Rb, Rc, and Rd, and a signal adder 13 are included.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The gm amplifiers 72A, 72B, 72C, and 72D detect and amplify only the voltage drops that occur across the corresponding detection resistors Ra, Rb, Rc, and Rd without being affected by the reference voltage V _R1 of the signal adder 13. Then, it is converted into a current signal and output.

The IV amplifiers 73A, 73B, 73C, and 73D convert the current signals of the corresponding gm amplifiers 72A, 72B, 72C, and 72D into voltage signals V _A , V _B , V _C, and V _D and output them. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the fifth embodiment of the present invention, the servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the fifth embodiment of the present invention, all the received light currents I _A , I _B , I _C and I _D can be converted into the RF voltage signal V _RF . Furthermore, according to the fifth embodiment of the present invention, it is not necessary to change the optical receiver physically and process like the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Further, according to the fifth embodiment of the present invention, the gm amplifiers 72A, 72B, 72C and 72D are not affected by the reference voltage V _R1 of the signal adder 13, and the corresponding detection resistors Ra, Rb, Rc and Only a voltage drop generated at both ends of Rd is detected and converted into a current signal. Therefore, the voltage value of the reference voltage V _R1 of the signal adder 13 can be set to a voltage value different from the voltage value of the reference voltage V _R2 of the IV amplifiers 73A, 73B, 73C, and 73D. In general, in the signal processing circuit 7 shown in FIG. 3, the RF voltage signal V _RF from the photodetection device (OEIC) is used for AC coupling, so the voltage value of the reference voltage V _R1 of the signal adder 13 is It is not necessary to match the voltage value of the reference voltage V _R2 of the IV amplifiers 73A, 73B, 73C and 73D.

In the fifth embodiment of the present invention, the reverse bias voltages of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D are determined by the reference voltage V _R1 of the signal adder 13. Therefore, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the parasitic capacitances of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D can be reduced. In this way, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the corresponding photodiode PD1 _A , due to the voltage drop that occurs across the detection resistors Ra, Rb, Rc, and Rd. It is possible to compensate for a decrease in each reverse bias voltage generated in PD1 _B , PD1 _C and PD1 _D. Furthermore, the design values of the detection resistors Ra, Rb, Rc, and Rd can be selected more widely.

Embodiment 6 FIG.
FIG. 9 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 81 according to Embodiment 6 of the present invention. 9, parts corresponding to those in FIG. 8 are given the same reference numerals, and descriptions thereof are omitted. In the photodetector 81 shown in FIG. 9, gm amplifiers (transconductance amplifiers) 82A, 82B, 82C and 82D are newly provided in place of the gm amplifiers 72A, 72B, 72C and 72D shown in FIG. The light detection device 81 according to the sixth embodiment has a configuration that should be called a current addition type, like the light detection devices 1, 41, 51, 61, and 71 described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus equipped with the optical pickup 2, a photodetection device 81 is newly provided in place of the photodetection device 1.

gm amplifier 82A, 82B, 82C and 82D, the photo diode PD1 _A, PD1 _B, PD1 _C and PD1 _D and detection resistor Ra, Rb, are provided corresponding to Rc and Rd. The positive input terminals of the gm amplifiers 82A, 82B, 82C, and 82D are connected to the connection points between the negative input terminal of the signal adder 13 and the corresponding detection resistors Ra, Rb, Rc, and Rd, respectively. gm amplifier 82A, 82B, each negative input terminal of the 82C and 82D, the corresponding photodiode PD1 _A, PD1 _B, PD1 _C and PD1 detection resistor Ra and the corresponding respective cathodes of _D, Rb, connected to the Rc and Rd Each point is connected. That is, in the sixth embodiment of the present invention, the polarities of the gm amplifiers 82A, 82B, 82C, and 82D are reversed as compared with the fifth embodiment of the present invention.

The input voltages at the positive input terminals of the gm amplifiers 82A, 82B, 82C and 82D are determined by the reference voltage V _R1 of the signal adder 13. However, the gm amplifiers 82A, 82B, 82C, and 82D are not affected by the reference voltage V _R1 of the signal adder 13, and receive light current I _A that flows through the corresponding photodiodes PD1 _A , PD1 _B , PD1 _C, and PD1 _D. , I _B , I _C, and I _D detect and amplify only the voltage drop generated at both ends of the corresponding detection resistors Ra, Rb, Rc, and Rd, and convert and output the current signal.

The IV amplifiers 73A, 73B, 73C, and 73D convert the current signals of the corresponding gm amplifiers 82A, 82B, 82C, and 82D into voltage signals V _A , V _B , V _C, and V _D and output them. The voltage signals V _A , V _B , V _C and V _D are on the negative side with respect to the reference voltage V _R2 . These voltage signals V _A , V _B , V _C and V _D are supplied to the signal processing circuit 7 shown in FIG. Note that the noise level in the current addition type photodetector 81 having the above-described configuration is the same as that of the photodetector 1 according to the first embodiment described above, and thus the description thereof is omitted.

As described above, the photodetector 81 according to the sixth embodiment of the present invention provides the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 81 comprises a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, gm amplifier 82A, 82B, and 82C and 82D, I-V amplifier 73A, 73B, and 73C and 73D, the detection resistor Ra, Rb, Rc, and Rd, and a signal adder 13 are included.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The gm amplifiers 82A, 82B, 82C, and 82D detect and amplify only the voltage drops that occur across the corresponding detection resistors Ra, Rb, Rc, and Rd without being affected by the reference voltage V _R1 of the signal adder 13. Then, it is converted into a current signal and output.

The IV amplifiers 73A, 73B, 73C, and 73D convert the current signals of the corresponding gm amplifiers 82A, 82B, 82C, and 82D into voltage signals V _A , V _B , V _C, and V _D and output them. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the sixth embodiment of the present invention, it is possible to generate servo signals for the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) simultaneously with the RF voltage signal V _RF . Further, according to the sixth embodiment of the present invention, it is possible to convert all the received currents I _A , I _B , I _C and I _D into the RF voltage signal V _RF . Furthermore, according to the sixth embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Further, according to the sixth embodiment of the present invention, the gm amplifiers 82A, 82B, 82C and 82D are not affected by the reference voltage V _R1 of the signal adder 13, and the corresponding detection resistors Ra, Rb, Rc and Only a voltage drop generated at both ends of Rd is detected and converted into a current signal. Therefore, the voltage value of the reference voltage V _R1 of the signal adder 13 can be set to a voltage value different from the voltage value of the reference voltage V _R2 of the IV amplifiers 73A, 73B, 73C, and 73D.

In the sixth embodiment of the present invention, the reverse bias voltages of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D are determined by the reference voltage V _R1 of the signal adder 13. Therefore, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the parasitic capacitances of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D can be reduced. In this way, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the corresponding photodiode PD1 _A , due to the voltage drop that occurs across the detection resistors Ra, Rb, Rc, and Rd. It is possible to compensate for a decrease in each reverse bias voltage generated in PD1 _B , PD1 _C and PD1 _D. Furthermore, the design values of the detection resistors Ra, Rb, Rc, and Rd can be selected more widely.

Embodiment 7 FIG.
FIG. 10 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 91 according to Embodiment 7 of the present invention. 10, parts corresponding to those in FIG. 8 are given the same reference numerals, and descriptions thereof are omitted. The detection resistors Ra, Rb, Rc and Rd corresponding to the cathodes of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _{D to which} the negative input terminals of the gm amplifiers 72A, 72B, 72C and 72D shown in FIG. 10, the negative input terminals of the gm amplifiers 72A, 72B, 72C and 72D are the positive input terminals of the signal adder 13 in the photodetector 91 shown in FIG. Are connected to each. That is, the reference voltage V _R1 is applied to each negative side input terminal of the gm amplifiers 72A, 72B, 72C, and 72D. The light detection device 91 according to the seventh embodiment has a configuration that should be called a current addition type, similarly to the light detection devices 1, 41, 51, 61, 71, and 81 described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus equipped with the optical pickup 2, a photodetection device 91 is newly provided in place of the photodetection device 1.

Hereinafter, the reason why the photodetection device 91 is configured as described above will be described. In the fifth embodiment described above, the parasitic capacitance (for example, due to wiring, transistors, etc.) at the negative input terminals of the gm amplifiers 72A, 72B, 72C, and 72D is the AC characteristic (particularly noise) of the RF voltage signal _VRF. ) May be worsened. Thus, in the seventh embodiment, the negative characteristics of the gm amplifiers 72A, 72B, 72C and 72D are connected to the positive input terminal of the signal adder 13, respectively, so that the AC characteristics of the RF voltage signal V _RF ( In particular, the risk factor of noise) is removed in advance. Since the positive side input terminal and the negative side input terminal of the signal adder 13 are at the same potential due to the principle of virtual ground (imaginary short), the operating principle of the photodetecting device 91 is the same as that of the fifth embodiment. This is substantially the same as the photodetection device 71. Therefore, the description regarding the operation principle of the photodetection device 91 is omitted.

As described above, the photodetector 91 according to the seventh embodiment of the present invention provides the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disc 3. It is used. The photodetector 91 comprises a photodiode PD1 _A, PD1 _B, PD1 _C and PD1 _D, gm amplifier 72A, 72B, and 72C and 72D, I-V amplifier 73A, 73B, and 73C and 73D, the detection resistor Ra, Rb, Rc, and Rd, and a signal adder 13 are included.

The photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. The gm amplifiers 72A, 72B, 72C, and 72D detect and amplify only the voltage drops that occur across the corresponding detection resistors Ra, Rb, Rc, and Rd without being affected by the reference voltage V _R1 of the signal adder 13. Then, it is converted into a current signal and output.

The IV amplifiers 73A, 73B, 73C, and 73D convert the current signals of the corresponding gm amplifiers 72A, 72B, 72C, and 72D into voltage signals V _A , V _B , V _C, and V _D and output them. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the seventh embodiment of the present invention, the servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the seventh embodiment of the present invention, all the received currents I _A , I _B , I _C and I _D can be converted into the RF voltage signal V _RF . Furthermore, according to the seventh embodiment of the present invention, it is not necessary to change the light receiver physically and in process as in the first conventional example. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

Further, according to the seventh embodiment of the present invention, the gm amplifiers 72A, 72B, 72C and 72D are not affected by the reference voltage V _R1 of the signal adder 13, and the corresponding detection resistors Ra, Rb, Rc and Only a voltage drop generated at both ends of Rd is detected and converted into a current signal. Therefore, the voltage value of the reference voltage V _R1 of the signal adder 13 can be set to a voltage value different from the voltage value of the reference voltage V _R2 of the IV amplifiers 73A, 73B, 73C, and 73D.

In the seventh embodiment of the present invention, the reverse bias voltages of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D are determined by the reference voltage V _R1 of the signal adder 13. Therefore, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the parasitic capacitances of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D can be reduced. In this way, by setting the reference voltage V _R1 of the signal adder 13 as high as possible, the corresponding photodiode PD1 _A , due to the voltage drop that occurs across the detection resistors Ra, Rb, Rc, and Rd. It is possible to compensate for a decrease in each reverse bias voltage generated in PD1 _B , PD1 _C and PD1 _D. Furthermore, the design values of the detection resistors Ra, Rb, Rc, and Rd can be selected more widely. In the seventh embodiment of the present invention, since the negative input terminals of the gm amplifiers 72A, 72B, 72C and 72D are connected to the positive input terminal of the signal adder 13, respectively, the RF voltage signal V _RF Deterioration of AC characteristics (particularly noise) can be reduced.

Embodiment 8 FIG.
FIG. 11 is a circuit diagram showing a schematic configuration of a photodetection device (OEIC) 101 according to Embodiment 8 of the present invention. FIG. 12 is a diagram showing an example of the arrangement of the light receiving surfaces of the photodiodes PD2 _A , PD2 _B , PD2 _C and PD2 _D constituting the four-divided light receiver (four quadrant light receiver) 102 shown in FIG. . In FIG. 11, parts corresponding to those in FIG. 1 are given the same reference numerals, and explanation thereof is omitted. In the photodetector 101 shown in FIG. 11, a cathode common type quadrant light receiver 102 is newly provided in place of the anode common type quadrant light receiver 11 shown in FIGS. 1 and 2.

The quadrant light receiver 102 has four light receiving areas A, B, C, and D. Four light receiving regions A, B, C and D is composed of a photodiode PD2 _A, PD2 _B, PD2 _C and PD2 _D, respectively. The quadrant photoreceiver 102 is a cathode common type in which the cathodes of the photodiodes PD2 _A , PD2 _B , PD2 _C and PD2 _D are connected in common and the power supply voltage V _CC is applied. The photodiodes PD2 _A , PD2 _B , PD2 _C and PD2 _D receive the light beam (main beam) reflected by the optical disc 2 (see FIG. 3) and receive light reception currents I _A , I _B , I _{C respectively.} And _ID are output.

  The photodetection device 101 according to the eighth embodiment has a configuration that should be called a current addition type, like the photodetection device 1 according to the first embodiment described above. Further, in the optical pickup 2 shown in FIG. 3 and the optical recording / reproducing apparatus in which the optical pickup 2 is mounted, a photodetecting device 101 is newly provided in place of the photodetecting device 1.

As described above, the photodetector 101 according to the eighth embodiment of the present invention is the optical pickup 2 that reproduces a signal from the light beam emitted from the semiconductor laser 21 that is a light source and reflected by the information recording surface of the optical disk 3. It is used. The photodetector 101 includes photodiodes PD2 _A , PD2 _B , PD2 _C and PD2 _D , current detectors 12A, 12B, 12C and 12D and a signal adder 13.

The photodiodes PD2 _A , PD2 _B , PD2 _C and PD2 _D receive the reflected light from the optical disc 3 and output received light currents I _A , I _B , I _C and I _D , respectively. Current detector 12A, 12B, 12C and 12D are received photocurrent I _A, I _B, detects the I _C and I _D, the corresponding light-receiving current I _A, I _B, respectively linearly to I _C and I _D The changing voltage signals V _A , V _B , V _C and V _D are output. The signal adder 13 adds the received light currents I _A , I _B , I _C and I _D to form an RF current signal I _RF, and converts the RF current signal I _RF into an RF voltage signal V _RF and outputs it. .

Therefore, according to the eighth embodiment of the present invention, the servo signals of the photodiodes PD1 _A , PD1 _B , PD1 _C and PD1 _D (channel) can be generated simultaneously with the RF voltage signal V _RF . Further, according to the eighth embodiment of the present invention, all the received currents I _A , I _B , I _C and I _D can be converted into the RF voltage signal V _RF . Furthermore, according to the eighth embodiment of the present invention, unlike the first conventional example described above, it is not necessary to change the light receiver physically and processically. As a result, the advantages of current addition can be fully exploited, and low noise operating characteristics can be improved.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention.
In addition, each of the above-described embodiments can divert each other's technology as long as there is no particular contradiction or problem in the purpose, configuration, or the like. For example, in the seventh embodiment, as shown in FIG. 10, the negative input terminals of the gm amplifiers 72A, 72B, 72C, and 72D are connected to the positive input terminal of the signal adder 13, respectively. In the sixth embodiment, the positive input terminals of the gm amplifiers 82A, 82B, 82C, and 82D shown in FIG. 9 may be connected to the positive input terminal of the signal adder 13, respectively.
In the second to seventh embodiments described above, an example using the anode common type four-divided light receiver 11 has been described. However, the present invention is not limited to this, and the cathode common type 4 is similar to the eighth embodiment described above. A split light receiver 102 may be used.

It is a circuit diagram which shows schematic structure of the photon detection apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows an example of arrangement | positioning of the light-receiving surface of each photodiode which comprises the 4-part dividing light receiver shown in FIG. It is the schematic which shows the structure of the optical pick-up provided with the optical detection apparatus shown in FIG. 1, and the optical recording / reproducing apparatus carrying this optical pick-up. It is a circuit diagram which shows schematic structure of the conventional photon detection apparatus. It is a circuit diagram which shows schematic structure of the photon detection apparatus which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows schematic structure of the photon detection apparatus which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows schematic structure of the photodetector which concerns on Embodiment 4 of this invention. It is a circuit diagram which shows schematic structure of the photodetector which concerns on Embodiment 5 of this invention. It is a circuit diagram which shows schematic structure of the photon detection apparatus which concerns on Embodiment 6 of this invention. It is a circuit diagram which shows schematic structure of the photon detection apparatus which concerns on Embodiment 7 of this invention. It is a circuit diagram which shows schematic structure of the photodetector which concerns on Embodiment 8 of this invention. It is a figure which shows an example of arrangement | positioning of the light-receiving surface of each photodiode which comprises the 4-part dividing light receiver shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41,51,61,71,81,91,101 ... Optical detection apparatus (OEIC), 2 ... Optical pick-up, 3 ... Optical disk (optical recording medium), 4 ... Controller, 5 ... Laser driver, 6 ... Diffraction Unit driver, 7 ... Signal processing circuit, 8 ... Equalizer, 9 ... Pickup driver (PU driver), 11,102 ... 4-divided light receiver (4-quadrant light receiver), 12A, 12B, 12C, 12D ... Current detector , 13 ... Signal adder, 21 ... Semiconductor laser (light source), 22 ... Diffraction unit, 23 ... Half mirror, 24 ... Objective lens, 25 ... Condensing lens, 42A-42D ... Voltage detector, 52A, 52B, 52C, 52D: non-inverting amplifier, 62A, 62B, 62C, 62D: inverting amplifier, 72A, 72B, 72C, 72D, 82A, 82B, 82C, 82D ... gm increase Vessel (transconductance amplifier), 73A, 73B, 73C, 73D ... I-V amplifier (current-voltage conversion amplifier), A, B, C, D ... light receiving _{region, I A, I B, I} C, I D ... receiving current, I _RF ... RF current _{signal, PD1 A, PD1 B, PD1} C, PD1 D, PD2 A, PD2 B, PD2 C, PD2 D ... photodiode, R ₁ ... input resistor, Ra, Rb, Rc, Rd ... Detection resistor, Rf: feedback resistor, V _A , V _B , V _C , V _D ... voltage signal, V _R1 , V _R2 , V _ref ... reference voltage, V _RF ... RF voltage signal

Claims (14)

A photodetector for use in an optical pickup that generates a signal from a light beam emitted from a light source and reflected by an optical recording medium,
A plurality of photodiodes that receive reflected light from the optical recording medium and output a received light current;
A signal adder for adding the light receiving currents of the plurality of photodiodes;
A plurality of current detectors provided corresponding to the plurality of photodiodes and detecting the light reception currents of the corresponding photodiodes. The signal adder is
The photodetection device according to claim 1, wherein the photodetection device is a current-voltage conversion amplifier that converts the added light reception current into a voltage signal. The plurality of current detectors are:
The photodetection device according to claim 1, wherein the voltage signal that linearly changes with respect to the corresponding light receiving current is output. The plurality of current detectors are:
A plurality of detection resistors provided corresponding to the plurality of photodiodes and interposed between the corresponding photodiodes and the signal adder;
A plurality of voltage detectors provided corresponding to the plurality of photodiodes and detecting a voltage drop generated in the corresponding detection resistor due to a current flowing through the corresponding photodiode. 3. The light detection device according to 2. The plurality of voltage detectors are:
The light detection device according to claim 4, wherein the voltage signals that change linearly with respect to the corresponding voltage drop are output. The plurality of current detectors are:
A plurality of detection resistors provided corresponding to the plurality of photodiodes and interposed between the corresponding photodiodes and the signal adder;
And a plurality of non-inverting amplifiers that are provided corresponding to the plurality of photodiodes and amplify a voltage with respect to a reference voltage at a connection point between the corresponding photodiode and the detection resistor. Item 3. The light detection device according to Item 1 or 2. The photodetecting device according to claim 6, further comprising: a plurality of inverting amplifiers provided corresponding to the plurality of non-inverting amplifiers and inverting and amplifying output voltages of the corresponding non-inverting amplifiers. The plurality of current detectors are:
A plurality of detection resistors provided corresponding to the plurality of photodiodes and interposed between the corresponding photodiodes and the signal adder;
A plurality of gm amplifiers provided corresponding to the plurality of photodiodes, and converting a voltage drop generated in the corresponding detection resistor by a current flowing through the corresponding photodiode into a current signal;
The light according to claim 1, further comprising: a plurality of current-voltage conversion amplifiers provided corresponding to the plurality of gm amplifiers and converting the current signals of the corresponding gm amplifiers into voltage signals. Detection device. Each gm amplifier has a positive input terminal connected to a connection point between the corresponding photodiode and the detection resistor, and a negative input terminal connected to the detection resistor corresponding to the input terminal of the signal adder. The photodetection device according to claim 8, wherein the photodetection device is connected to a connection point. Each gm amplifier has a negative input terminal connected to a connection point between the corresponding photodiode and the detection resistor, and a positive input terminal connected to the detection resistor corresponding to the input terminal of the signal adder. The photodetection device according to claim 8, wherein the photodetection device is connected to a connection point. In each of the gm amplifiers, one of a positive input terminal and a negative input terminal is connected to a connection point between the corresponding photodiode and the corresponding detection resistor, and a reference voltage is applied to the other. The photodetection device according to claim 8, wherein Each photodiode is
The photodetecting device according to claim 1, wherein the common cathode connection or the common anode connection is used.   An optical pickup comprising the light detection device according to claim 1.   An optical recording / reproducing apparatus comprising the optical pickup according to claim 13.

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