JP2009252257A - Optical pickup and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the correction work of a monitor signal. <P>SOLUTION: The optical pickup 1 includes: two or more laser units for emitting laser beams different in wavelength; an objective lens 18; a dichroic beam splitter 3 disposed in the middle of its optical path to split a part of the laser beam for monitoring emission power; and a light receiving element 4 for receiving a laser split beam to generate a photoelectric signal. Even when the light receiving element 4 photoelectrically converts any of laser split beams, the dichroic beam splitter 3 splits it to a laser split beam of intensity to generate a photoelectrical signal of the same value. Thus, monitor signals of equal signal levels are generated for monitoring emission power. Only by correcting the signal level of any one of the monitor signals, the correction is reflected on the other monitor signals. Thus, the correction work of the monitor signals is simplified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup and an optical disc apparatus, and is suitable for application to an optical disc apparatus capable of recording and reproducing information on two types of optical discs, for example, a DVD (Digital Versatile Disk) system and a CD (Compact Disk) system. It is.

  The two types of optical disks of the DVD system and the CD system have different wavelengths of laser light used for recording and reproducing information.

  For this reason, the conventional optical disc apparatus corresponds to the DVD optical disc and the CD optical disc with respect to the optical pickup, and emits laser beams having different wavelengths, respectively, and a DVD laser source and a CD laser source. Was provided.

  Incidentally, in the following description, the laser light source for the DVD system is also referred to as a DVD laser light source, and the laser light source for the CD system is also referred to as a CD laser light source.

  In the following description, when it is not necessary to distinguish between the DVD laser light source and the CD laser light source, they are collectively referred to as a laser light source.

  In the following description, laser light emitted from a DVD laser light source is also called DVD laser light, and laser light emitted from a CD laser light source is also called CD laser light.

  In the following description, when it is not necessary to distinguish between the laser beam for DVD and the laser beam for CD, these are also collectively referred to as a laser beam.

  Then, the optical disk device collects the DVD laser light emitted from the DVD laser light source by the objective lens and irradiates the recording surface of the optical disk at the time of recording information on the DVD optical disk. Information is recorded on an optical disk.

  Also, the optical disc apparatus collects the DVD laser light emitted from the DVD laser light source by the objective lens and irradiates the recording surface of the optical disc at the time of reproducing information from the DVD optical disc. The reflected laser beam obtained by reflecting the DVD laser beam on the surface is received by the reproducing light receiving element.

  The optical disc apparatus reproduces information from the optical disc as a reproduction signal by generating a reproduction signal based on the reflected laser beam received by the reproduction light receiving element.

  Further, the optical disk apparatus records and reproduces information with respect to the above-described DVD optical disk except that a CD laser light source is used instead of the DVD laser light source when recording and reproducing information on the CD optical disk. It operates in the same way.

As a result, the optical disc apparatus can record information on a CD type optical disc and reproduce the information (see, for example, Patent Document 1).
JP 2006-73116 A

  By the way, in the optical disk apparatus having such a configuration, a part of the DVD laser light emitted from the DVD laser light source is split in the optical path from the DVD laser light source and CD laser light source to the objective lens. In addition, a beam splitter that splits a part of the CD laser emitted from the CD laser light source is provided.

  In addition, the optical pickup includes a power monitoring circuit for monitoring the light emission powers of the DVD laser light and the CD laser light emitted from the DVD laser light source and the CD laser light source at the time of recording and reproducing information with respect to the optical disk. Is also provided.

  Incidentally, in the following description, a part of the DVD laser beam dispersed by the beam splitter is also called a DVD laser spectrum, and a part of the CD laser beam dispersed by the beam splitter is called a CD laser spectrum. Call.

  In the following description, when it is not necessary to distinguish between the laser spectrum for DVD and the laser spectrum for CD, these are collectively referred to simply as laser spectroscopy. The power monitoring circuit is also called a front monitor circuit.

  The front monitor circuit is a light receiving element for monitoring the DVD laser spectrum or the CD laser spectrum separated from the DVD laser light or CD laser light by the beam splitter (hereinafter also referred to as a monitor light receiving element). By receiving light and performing photoelectric conversion, a photoelectric signal having a current value is generated.

  Further, the front monitor circuit performs a predetermined process such as a current / voltage conversion process and a voltage amplification process on the photoelectric signal, thereby generating a monitor signal corresponding to the amount of light of the received laser spectrum, and Send to APC (Automatic Power Control) circuit.

  The APC circuit then emits the DVD laser light and CD laser light emitted from the DVD laser light source and CD laser light source and irradiated onto the recording surface of the optical disk based on the monitor signal given from the front monitor circuit. Are controlled so as to be the light emission power at the time of recording and reproducing information individually defined in the DVD system and the CD system.

  Here, for the monitor light receiving element, the ratio (hereinafter referred to as “light receiving”) of the received light amount [W] of the laser spectrum and the current value [A] of the photoelectric signal obtained by photoelectrically converting the received laser spectrum. The sensitivity [also called A / W] differs depending on the wavelength of the laser spectrum to be received.

  That is, for example, when the DVD laser spectrum received by the monitor light receiving element and the CD laser spectrum have the same amount of light, the front monitor circuit determines the current value according to the DVD laser spectrum or the CD laser spectrum [ As a result, monitor signals having different signal levels (that is, voltage values [V]) are generated and sent to the APC circuit.

  Further, the light receiving sensitivity of the monitor light receiving element varies depending on the manufacturing accuracy and the like.

  For this reason, when a plurality of front monitor circuits are compared, for example, monitor signals having the same wavelength and the same light quantity may be received by the monitor light receiving element, and monitor signals having different signal levels may be generated.

  When the monitor signal having a signal level different from the original signal level corresponding to the received light amount of the laser spectrum is given from the front monitor circuit, the APC circuit sets the emission power of the laser beam based on the monitor signal. It will be controlled differently from power.

  Therefore, the front monitor circuit is provided with a variable resistor for correcting the signal level (that is, the voltage value) of the monitor signal in consideration of variations in the light receiving sensitivity of the monitor light receiving element. It can be adjusted from the outside.

  However, in the front monitor circuit having such a configuration, as described above, the light receiving sensitivity of the monitoring light receiving element is different for each wavelength of the received laser spectrum.

  For this reason, in the conventional optical disk apparatus, the resistance value of the variable resistance of the front monitor circuit both when the DVD laser light is emitted from the DVD laser light source and when the CD laser light is emitted from the CD laser light source. Therefore, there is a problem that the signal level of the monitor signal needs to be corrected to adjust the signal level of the monitor signal.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose an optical pickup and an optical disc apparatus capable of simplifying the work of correcting the signal level of the monitor signal.

  In order to solve such a problem, in the present invention, in an optical pickup, at least two or more laser light sources that emit laser beams having different wavelengths and laser beams having different wavelengths emitted from the two or more laser light sources are condensed. A part of the laser beams having different wavelengths emitted from the two or more laser light sources, respectively, are arranged in the middle of the optical path between the condensing lens, the two or more laser light sources, and the condensing lens. A spectral element that performs spectroscopy for monitoring the emission power of the laser beam, and a laser spectrum that is split from each laser beam having a different wavelength by the spectral element, and generates a photoelectric signal by photoelectrically converting the received laser spectrum A light receiving element, and a part of laser light having different wavelengths emitted from two or more laser light sources by a spectroscopic element, It is converted photoelectrically optical element receives either different laser spectral wavelengths and so that the spectral laser spectroscopy amount such as to produce a photoelectric signal of the same value.

  Therefore, in the present invention, the received laser spectrum can be photoelectrically converted to generate a photoelectric signal having the same current value regardless of which of the laser spectra having different wavelengths is received by the light receiving element. Based on the signal, a power monitoring signal having the same signal level can be generated for monitoring the emission power of the laser beam. As a result, in this description, only the signal level of any one of the power monitoring signals generated based on laser spectroscopy having different wavelengths is corrected, and the correction of the signal level is reflected in the other power monitoring signals. be able to.

  According to the present invention, in an optical pickup, at least two or more laser light sources that emit laser beams having different wavelengths, and a condensing lens that collects laser beams having different wavelengths emitted from the two or more laser light sources, Monitoring the emission power of the laser light using a part of the laser light with different wavelengths emitted from the two or more laser light sources as laser spectroscopy, arranged in the middle of the optical path between the two or more laser light sources and the condenser lens And a light receiving element for receiving a laser spectrum split from each laser beam having a different wavelength by the spectral element and generating a photoelectric signal by photoelectrically converting the received laser spectrum. In this way, a part of the laser beams having different wavelengths emitted from two or more laser light sources are separated from the laser beams having different wavelengths by the light receiving element. Regardless of the spectroscopic light received and photoelectrically converted, the light receiving element receives any of the laser spectroscopic light with different wavelengths by splitting the light into a laser spectroscopic light amount that generates a photoelectric signal having the same value. Even when the received laser spectrum can be photoelectrically converted to generate a photoelectric signal having the same current value, a signal level for monitoring the emission power of the laser beam can be generated based on the generated photoelectric signal. It is possible to generate equal power monitoring signals, and as a result, by correcting the signal level of any one of the power monitoring signals generated based on laser spectroscopy with different wavelengths, It is possible to realize an optical pickup and an optical disc apparatus that can reflect the correction of the signal level and thus can simplify the correction work of the power monitoring signal.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) Configuration of Optical Disc Device In FIG. 1, reference numeral 10 denotes an optical disc device according to the present invention as a whole. Such an optical disc apparatus 10 is configured with a control unit 11 as the center, and can record information on each of two types of optical discs 19 of a DVD system and a CD system, and can reproduce information recorded on the optical disc 19. ing.

  In the following description, a DVD optical disk is also called a DVD, and a CD optical disk is also called a CD.

  In the following description, when it is not necessary to distinguish these DVDs and CDs, these DVDs and CDs are collectively referred to simply as optical disks.

  The optical disk apparatus 10 is assumed to be mounted on, for example, a notebook computer apparatus.

  The control unit 11 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) in which various programs are stored, a RAM (Random Access Memory) used as a work memory of the CPU, and the like. The optical disk device 10 is controlled in an integrated manner.

  As a result, the control unit 11 rotates the spindle motor 14 via the drive unit 12 to rotate the optical disk 19 placed on a turntable (not shown) at a desired speed.

  In this state, the control unit 11 sends information to be recorded to the signal processing unit 13 when recording information on the optical disc 19.

  The signal processing unit 13 generates a recording signal by performing predetermined encoding processing and modulation processing on the information, and sends the recording signal to the optical pickup 1.

  The optical pickup 1 emits laser light for information recording based on the recording signal given from the signal processing unit 13, and condenses the laser light through the objective lens 18 to irradiate the recording surface of the optical disk 19. To do.

  Thus, the optical pickup 1 can record information on the recording surface of the optical disk 19.

  By the way, the optical pickup 1 receives the reflected laser beam obtained by reflecting the laser beam on the recording surface of the optical disc 19 at this time, generates a received light signal corresponding to the received light result, and sends it to the signal processing unit 13.

  In this case, the signal processing unit 13 generates a focus error signal and a tracking error signal based on the received light signal, and sends them to the drive unit 12 via the control unit 11.

  Then, the drive unit 12 drives and controls the biaxial actuator 16 of the optical pickup 1 based on the focus error signal, so that the objective lens holder 17 on which the objective lens 18 is mounted is in the focus direction in which the objective lens holder 17 approaches or is separated from the optical disc 19. Move.

  Thus, the drive unit 12 can focus the laser beam on a desired track on the recording surface of the optical disc 19 by performing focus control to move the objective lens 18 in the focus direction.

  Further, the drive unit 12 finely moves the objective lens 18 in the tracking direction toward the inner peripheral side or the outer peripheral side of the optical disc 19 by drivingly controlling the biaxial actuator 16 of the optical pickup 1 based on the tracking error signal.

  In this way, the drive unit 12 can cause the focus of the laser light to follow a desired track on the recording surface of the optical disc 19 by performing tracking control for finely moving the objective lens 18 in the tracking direction.

  On the other hand, when reproducing information from the optical disk 19, the control unit 11 causes the optical pickup 1 to emit laser light for information reproduction and condenses the laser light through the objective lens 18 to record the information on the recording surface of the optical disk 19. To irradiate.

  At this time, the optical pickup 1 receives the reflected laser beam obtained by reflecting the laser beam on the recording surface of the optical disc 19, generates a light reception signal corresponding to the light reception result, and sends it to the signal processing unit 13.

  The signal processing unit 13 generates a reproduction RF signal based on the received light signal, and performs predetermined demodulation processing, decoding processing, and the like on this signal so that information recorded on the recording surface of the optical disc 19 can be reproduced. Has been made.

  By the way, the signal processing unit 13 generates a focus error signal and a tracking error signal based on the detection signal even when reproducing information, and sends them to the drive unit 12 via the control unit 11.

  As a result, the drive unit 12 performs focus control and tracking control of the objective lens 18 in the same manner as described above even during reproduction of information.

  Incidentally, the control unit 11 appropriately moves the optical pickup 1 in the tracking direction along the moving axis 20 by driving the sled motor 15 through the drive unit 12 when recording and reproducing information. Take control.

  As described above, the optical disc apparatus 10 records information on the optical disc 19 and reproduces information from the optical disc 19 by focusing the laser beam on a desired track of the optical disc 19. Has been made.

(2) Configuration of Optical Pickup The optical pickup 1 includes a DVD laser unit formed by integrating a DVD laser light source and a light receiving element, a CD laser light source, and a light receiver. A CD type laser unit formed so as to be integrated with the element is provided.

  In the following description, a DVD laser unit is also called a DVD laser unit, and a CD laser unit is also called a CD laser unit.

  In the following description, when it is not necessary to distinguish the laser unit for DVD system and the laser unit for CD system, these are collectively referred to simply as a laser unit.

  In the following description, laser light emitted from a DVD laser unit at the time of recording and reproducing information on a DVD is also called DVD laser light, and reflected laser light received by the DVD laser unit is reflected on the DVD. Also called laser light.

  Further, in the following description, the laser beam emitted from the CD laser unit at the time of recording and reproducing information on the CD is also called a CD laser beam, and the reflected laser beam received by the CD laser unit is reflected on the CD. Also called laser light.

  In the following description, when it is not necessary to distinguish between the laser beam for DVD and the laser beam for CD, these are collectively referred to simply as laser beam, and the reflected laser beam for DVD and the reflected laser beam for CD are particularly When it is not necessary to distinguish between them, they are collectively referred to simply as reflected laser light.

  Further, the optical pickup 1 splits a part of the DVD laser light emitted from the DVD laser unit in the middle of the optical path from the DVD laser unit and the CD laser unit to the objective lens 18, and also for the CD. A plate-type dichroic beam splitter that splits a part of the laser beam for CD emitted from the laser unit is provided.

  The processing of the optical pickup 1 when a DVD 19a as an optical disk 19 is placed on a turntable (not shown), information is recorded on the DVD 19a, and information recorded on the DVD 19a is reproduced will be described with reference to FIG.

  When recording information on the DVD 19a, the optical pickup 1 captures a recording signal supplied from the signal processing unit 13 into a laser driver (not shown). The laser driver generates a drive signal by amplifying the recording signal or the like, and sends the drive signal to the DVD laser unit 2a.

  Here, the DVD laser unit 2a is formed by integrating a laser diode 5a as a DVD laser light source, a photodiode 6a as a light receiving element, and a holographic optical element 7a.

  The DVD laser unit 2a takes in the drive signal given from the laser driver into the laser diode 5a.

  The laser diode 5a emits a DVD laser beam L1 having a wavelength of 660 [nm] having a predetermined light quantity for recording based on the drive signal, passes through the collimator lens 8a, and converts it into parallel light, thereby producing a dichroic beam. The light enters the splitter 3.

  The dichroic beam splitter 3 is a spectroscopic element that separates a part of incident laser light and splits the laser light so as to transmit part of the laser light.

  In the dichroic beam splitter 3, an antireflection film made of a dielectric multilayer film or a metal thin film is deposited on the surface 3a of the plate glass, and a wavelength selective film is deposited on the back surface 3b.

  As a result, the dichroic beam splitter 3 has a spectral ratio (that is, a ratio between the transmittance and the reflectance of the laser light) for each of the DVD laser light and the CD laser light having different wavelengths depending on the film characteristics of the antireflection film and the wavelength selective film. ) Is selected.

  At this time, the dichroic beam splitter 3 transmits a part of the incident DVD laser light L1 and splits the DVD laser light L1 so as to reflect a part thereof.

  Incidentally, in the following description, a part of the DVD laser light dispersed by transmission from the DVD laser light is also called DVD transmission laser spectroscopy, and the DVD laser dispersed by reflection from the DVD laser light. A part of the light is also called reflection laser spectroscopy for DVD.

  The transmitted laser spectrum L1a for DVD obtained by transmitting a part of the DVD laser light L1 through the dichroic beam splitter 3 is reflected by the rising mirror 9 and enters the objective lens 18.

  The objective lens 18 condenses the DVD transmission laser spectrum L1a and irradiates the recording layer of the DVD 19a. At this time, a recording mark corresponding to the modulation pattern of the DVD transmission laser spectrum L1a is formed on the recording layer of the DVD 19a at the irradiation position of the DVD transmission laser spectrum L1a.

  On the other hand, the reflected laser spectrum L1b for DVD obtained by reflecting a part of the DVD laser light L1 by the dichroic beam splitter 3 is a light receiving circuit provided in a power monitoring circuit for monitoring the light emission power of the laser light described later. Incident on element 4.

  Incidentally, in the following description, the power monitoring circuit is also referred to as a front monitor circuit, and the light receiving element 4 provided in the front monitor circuit is also referred to as a monitoring light receiving element.

  Further, the optical pickup 1 takes a reproduction light amount signal given from the control unit 11 into a laser driver (not shown) when reproducing information from the DVD 19a. The laser driver generates a drive signal having a constant signal level by, for example, amplifying the reproduction light quantity signal, and sends the drive signal to the DVD laser unit 2a.

  The DVD laser unit 2a takes in the drive signal given from the laser driver into the laser diode 5a.

  Then, the laser diode 5a emits a DVD laser beam L1 having a reproduction light amount based on the drive signal, and makes it incident on the dichroic beam splitter 3 through the collimator lens 8a as in the above recording.

  The reflected laser spectrum L1b for DVD obtained by reflecting a part of the DVD laser light L1 by the dichroic beam splitter 3 is incident on the light receiving element 4 for monitoring. On the other hand, the DVD transmission laser spectrum L1a obtained by transmitting a part of the DVD laser light L1 through the dichroic beam splitter 3 is reflected by the rising mirror 9 and enters the objective lens 18.

  The objective lens 18 condenses the DVD transmission laser spectrum L1a and irradiates the recording layer of the DVD 19a. At this time, the reflected laser beam obtained by reflecting the DVD transmission laser spectrum L1a on the recording layer of the DVD 19a (hereinafter also referred to as the DVD reflection laser beam L1c) is converted into parallel light by the objective lens 18 and is After being reflected by the upper mirror 9, it sequentially passes through the dichroic beam splitter 3 and the collimator lens 8a and reaches the DVD laser unit 2a.

  The DVD laser unit 2a bends the DVD reflected laser beam L1c by a holographic optical element (HOE) and receives it by the photodiode 6a.

  When the photodiode 6a receives the reflected laser beam L1c for DVD, the photodiode 6a generates a light reception signal corresponding to the light reception result and sends it to the signal processing unit 13.

  The signal processing unit 13 generates a focus error signal and a tracking error signal by performing predetermined arithmetic processing based on the received light signal, and sends them to the drive unit 12 via the control unit 11.

  Next, the processing of the optical pickup 1 when a CD 19b as an optical disc 19 is placed on a turntable (not shown), information is recorded on the CD 19b, and information recorded on the CD 19b is reproduced will be described with reference to FIG. To do.

  The optical pickup 1 takes in a recording signal given from the signal processing unit 13 to a laser driver (not shown) when recording information on the CD 19b. The laser driver generates a drive signal by amplifying the recording signal or the like, and sends the drive signal to the CD laser unit 2b.

  Here, the laser unit 2b for CD is formed by integrating a laser diode 5b as a laser beam source for CD system, a photodiode 6b as a light receiving element, and a holographic optical element 7b.

  The CD laser unit 2b takes in the drive signal given from the laser driver into the laser diode 5b.

  Based on the drive signal, the laser diode 5b emits a CD laser beam L2 having a wavelength of 780 [nm] having a predetermined light quantity for recording, passes through the collimator lens 8b, and converts it into parallel light, thereby producing a dichroic beam. The light enters the splitter 3.

  At this time, the dichroic beam splitter 3 transmits a part of the incident CD laser light L2 and splits the CD laser light L2 so as to reflect a part thereof.

  Incidentally, in the following description, a part of the CD laser light dispersed by transmission from the CD laser light is also called CD transmission laser spectroscopy, and the CD laser dispersed by reflection from the CD laser light. A part of the light is also referred to as reflection laser spectroscopy for CD.

  The reflected laser spectrum L2a for CD obtained by reflecting a part of the laser beam L2 for CD by the dichroic beam splitter 3 is reflected by the rising mirror 9 and enters the objective lens 18.

  The objective lens 18 collects the reflected laser spectrum L2a for CD and irradiates the recording layer of the CD 19b. At this time, a recording mark corresponding to the modulation pattern of the reflection laser spectrum for CD L2a is formed on the recording layer of the CD 19b at the irradiation position of the reflection laser spectrum for CD L2a.

  On the other hand, the CD transmission laser spectrum L2b obtained by transmitting a part of the CD laser light L2 through the dichroic beam splitter 3 is incident on the monitor light receiving element 4 provided in the front monitor circuit.

  Further, the optical pickup 1 takes a reproduction light amount signal given from the control unit 11 into a laser driver (not shown) when reproducing information from the CD 19b. The laser driver generates a drive signal having a constant signal level by amplifying the reproduction light quantity signal and sends the drive signal to the CD laser unit 2b.

  The CD laser unit 2b takes in the drive signal given from the laser driver into the laser diode 5b. Then, the laser diode 5b emits a CD laser beam L2 having a reproduction light amount based on the drive signal and makes it incident on the dichroic beam splitter 3 through the collimator lens 8b as in the above-described recording.

  A transmitted laser spectrum L2b for CD obtained by transmitting a part of the CD laser light L2 through the dichroic beam splitter 3 is incident on the monitor light receiving element 4. On the other hand, the reflected laser spectrum L2a for CD obtained by reflecting a part of the laser beam for CD by the dichroic beam splitter 3 is reflected by the rising mirror 9 and enters the objective lens 18.

  The objective lens 18 collects the reflected laser spectrum L2a for CD and irradiates the recording layer of the CD 19b. At this time, reflected laser light (hereinafter also referred to as “CD reflected laser light L2c”) obtained by reflecting the reflected laser spectrum L2a for CD on the recording layer of the CD 19b is converted into parallel light by the objective lens 18 to rise. After being reflected by the mirror 9, it is reflected by the dichroic beam splitter 3, passes through the collimator lens 8b, and reaches the CD laser unit 2b.

  The CD laser unit 2b bends the reflected laser beam L2c for CD by the holographic optical element 7b and receives it by the photodiode 6b.

  When the photodiode 6b receives the reflected laser light for CD L2c, the photodiode 6b generates a light reception signal corresponding to the light reception result and sends it to the signal processing unit 13.

  The signal processing unit 13 generates a focus error signal and a tracking error signal by performing predetermined arithmetic processing based on the received light signal, and sends them to the drive unit 12 via the control unit 11.

  In this way, the optical pickup 1 can record information on the DVD 19a and the CD 19b, and can reproduce information recorded on the DVD 19a and the CD 19b. Further, the optical pickup 1 splits the DVD laser light L1 and the CD laser light L2 emitted from the DVD laser unit 2a and the CD laser unit 2b, and causes a part of them to enter the monitor light receiving element 4. I have to.

  Incidentally, in the following description, when it is not necessary to particularly distinguish the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD received by the monitor light receiving element 4 of the front monitor circuit, these are simply put together to simply perform laser spectroscopy. Also called.

(3) Configuration of Front Monitor Circuit Next, the circuit configuration of the front monitor circuit will be described with reference to FIG.

  The front monitor circuit 20 includes a monitor light receiving element 4, a monitor signal generation unit 21, and a variable resistor 24 for signal level correction.

  In practice, the front monitor circuit 20 is provided with a photodiode as the light-receiving element 4 for monitoring, the anode of the photodiode is grounded, and the cathode is connected to the inverting input terminal of the operational amplifier 22.

  The non-inverting input terminal of the operational amplifier 22 is connected to the reference voltage input terminal via the resistor 26, and the reference voltage supplied from the reference voltage input terminal is applied.

  Further, the operational amplifier 22 has an output terminal connected to one end of the variable resistor 24 and also connected to an inverting input terminal via a current / voltage conversion resistor 23.

  The operational amplifier 22 constitutes a current / voltage conversion circuit 30 together with the current / voltage conversion resistor 23 and the resistor 26.

  The other end of the variable resistor 24 is connected to the inverting input terminal of the operational amplifier 25 via the resistor 27.

  Further, the non-inverting input terminal of the operational amplifier 25 is connected to the reference voltage input terminal via the resistor 28, and the reference voltage supplied from the reference voltage input terminal is applied.

  Furthermore, the output terminal of the operational amplifier 25 is connected to the APC circuit and also connected to the inverting input terminal via the feedback resistor 29. The operational amplifier 25 constitutes a voltage amplification circuit 31 together with the resistor 27, the resistor 28, and the feedback resistor 29.

  In the front monitor circuit 20 having such a configuration, when the photodiode serving as the monitoring light receiving element 4 receives the laser spectrum, it photoelectrically converts the received laser spectrum to generate a photoelectric signal having a current value corresponding to the light quantity of the laser spectrum. Generate.

  The current / voltage conversion circuit 30 generates a power monitoring signal (hereinafter also referred to as a monitor signal) having a voltage value corresponding to the current value of the photoelectric signal generated by the photodiode, and the monitor signal is variable. The voltage is supplied to the voltage amplification circuit 31 via the resistor 24.

  Incidentally, the monitor signal generated by the current / voltage conversion circuit 30 is expressed by equation (1), where I is the current value of the photoelectric signal and Riv is the resistance value of the current / voltage conversion resistor 23.

  -I × Riv (1)

  The voltage value represented by

  The voltage amplification circuit 31 amplifies the signal level (that is, voltage value) of the monitor signal generated by the current / voltage conversion circuit 30 to a desired signal level (that is, desired voltage value), and then sends it to the APC circuit. To do.

  Incidentally, in the voltage amplification circuit 31, when the resistance value of the resistor 27 is Rs and the resistance value of the feedback resistor 29 is Rf, the expression (2)

  Rf / Rs (2)

  The monitor signal is amplified with the amplification degree represented by

  Incidentally, the light receiving sensitivity of the monitor light receiving element 4 varies. However, in the front monitor circuit 20, the current / voltage conversion rate in the current / voltage conversion circuit 30 (that is, the resistance value of the current / voltage conversion resistor 23) is fixed.

  In the front monitor circuit 20, the monitor signal amplification factor in the voltage amplifier circuit 31 is also fixed. Therefore, in the front monitor circuit 20, the resistance value of the variable resistor 24 can be adjusted from the outside.

  Then, in the front monitor circuit 20, for example, when the optical pickup is manufactured, the resistance value of the variable resistor 24 is appropriately adjusted from the outside, whereby the variation in the signal level of the monitor signal due to the variation in the light receiving sensitivity of the light receiving element 4 for monitoring. Can be corrected.

(4) Spectral Characteristics of Dichroic Beam Splitter As described above, the front monitor circuit 20 is obtained by receiving the laser spectrum (that is, the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD) with the monitor light receiving element 4. Based on the photoelectric signal, a monitor signal having a signal level corresponding to the light amount of the laser spectrum is generated.

  The light receiving sensitivity of the monitor light receiving element 4 (that is, the ratio between the light intensity of the laser spectrum and the current value of the photoelectric signal obtained by photoelectric conversion of the laser spectrum) is the laser spectrum received by the monitor light receiving element 4. It depends on the wavelength.

  For this reason, even if the front monitor circuit 20 receives the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD with the same light amount by the monitor light receiving element 4, for example, the signal level at the time of receiving these signals. Different monitor signals are generated.

  That is, in the front monitor circuit 20, not only the light receiving sensitivity of the monitor light receiving element 4 but also the light amount [W] of the laser spectrum received by the monitor light receiving element 4 and the monitor signal generated based on the laser spectrum. The ratio to the signal level (hereinafter also referred to as front monitor sensitivity [V / W]) varies depending on the wavelength of laser spectroscopy received by the monitor light receiving element 4.

  Therefore, the front monitor sensitivity when the reflected laser spectrum L1b for DVD is received by the front monitor circuit 20 is S1 [mV / μW], and the front monitor sensitivity when the transmitted laser spectrum L2b for CD is received is S2 [mV / μW].

  Further, the gain after correction of the signal level of the monitor signal (hereinafter also referred to as a DVD monitor signal) generated based on the reflection laser spectrum L1b for DVD in the front monitor circuit 20 (that is, voltage gain, This is also referred to as a front monitor gain) is α [dB].

  Further, the front monitor gain after correcting the signal level of the monitor signal (hereinafter also referred to as a CD monitor signal) generated based on the CD transmission laser spectrum L2b in the front monitor circuit 20 is set to β [dB].

  Further, the light quantity of the DVD laser light L1 received by the dichroic beam splitter 3 is Po1 [μW], and the light quantity of the CD laser light L2 received by the dichroic beam splitter 3 is Po2 [μW].

  Furthermore, the spectral ratio (transmittance [%]: reflectance [%]) of the DVD laser light L1 in the dichroic beam splitter 3 is T1: R1, and the spectral ratio of the CD laser light L2 in the dichroic beam splitter 3 is T2: Let R2.

  If the signal level [mV] of the DVD monitor signal that is output when the front monitor circuit 20 receives the reflected laser spectrum L1b for DVD is Fpd1, the signal level of the DVD monitor signal is expressed by equation (3).

  Fpd1 = R1, Po1, S1, α (3)

By multiplying the light quantity of the DVD laser beam L1 by the reflectance of the dichroic beam splitter 3 and multiplying the light quantity of the DVD reflected laser spectrum L1b by the front monitor sensitivity and the front monitor gain. Can be sought.

  If the signal level [mV] of the CD monitor signal output when the front monitor circuit 20 receives the CD transmission laser spectrum L2b is Fpd2, the signal level of the CD monitor signal is expressed by equation (4).

  Fpd2 = T2, Po2, S2, β (4)

By multiplying the light amount of the CD laser beam L2 by the transmittance of the dichroic beam splitter 3 and multiplying the light amount of the CD transmitted laser spectrum L2a by the front monitor sensitivity and the front monitor gain, Can be sought.

  Here, in order to eliminate the wavelength dependence of the front monitor sensitivity in the front monitor circuit 20, the equation (5) is used.

Fpd1 = Fpd2
R1, Po1, S1, α = T2, Po2, S2, β (5)

In the front monitor circuit 20, it is necessary to make the signal level of the DVD monitor signal equal to the signal level of the CD monitor signal.

  However, the front monitor circuit 20 described above is provided with only one variable resistor 24 for correcting the signal level of the DVD monitor signal and the signal level of the CD monitor signal.

  Therefore, the front monitor circuit 20 needs to adjust the resistance value of one variable resistor 24 so that the signal level of the DVD monitor signal is equal to the signal level of the CD monitor signal.

  That is, in the front monitor circuit 20, the expression (6)

    α = β (6)

By adjusting the resistance value of one variable resistor 24 as expressed by the equation (1) and correcting the signal level of one of the DVD monitor signal and the CD monitor signal, the other signal level can also be corrected. There is a need.

  Therefore, in the front monitor circuit 20, when the signal level of the DVD monitor signal is equal to the signal level of the CD monitor signal, it does not depend on the correction of the monitor signal using the variable resistor 24. 7) Formula

  R1, Po1, S1 = T2, Po2, S2 (7)

In the dichroic beam splitter 3, it is necessary to appropriately select the spectral ratio of the DVD laser light L1 and the spectral ratio of the CD laser light L2.

  Accordingly, in the dichroic beam splitter 3, the ratio between the reflectance for separating the reflected laser spectrum L1b for DVD from the laser beam L1 for DVD and the transmittance for separating the transmitted laser spectrum L2b for CD from the laser beam L2 for CD. (8) expanded from (7)

  R1 / T2 = (Po2 · S2) / (Po1 · S1) (8)

As shown, the spectrum is equal to the ratio of the multiplication result of the light amount of the CD laser light L2 and the corresponding front monitor sensitivity to the multiplication result of the light amount of the DVD laser light L1 and the corresponding front monitor sensitivity. In order to obtain the characteristics, the spectral ratio of the DVD laser light L1 and the spectral ratio of the CD laser light L2 are selected.

  The dichroic beam splitter 3 is a DVD laser beam L1 and a CD laser beam that are appropriately selected so as to obtain spectral characteristics satisfying the expression (8) without causing any trouble in recording and reproducing information on the DVD 19a and CD 19b. An antireflection film is formed on the surface 3a according to the spectral ratio of each of L2.

  In the above equations (3) to (8), the case where S1 and S2 are expressed as the front monitor sensitivity has been described. However, since the front monitor sensitivity depends only on the light reception sensitivity of the light receiving element 4 for monitoring, The light receiving sensitivity of the monitor light receiving element 4 may be used instead of the sensitivity.

  That is, the spectral characteristic of the dichroic beam splitter 3 is that the current value of the photoelectric signal output from the monitor light receiving element 4 receives the reflected laser spectrum L1b for DVD as the laser spectrum and the transmitted laser spectrum L2b for CD. In some cases, the spectral ratio of the DVD laser light L1 and the spectral ratio of the CD laser light L2 may be selected so as to be the same.

  Therefore, even when the light receiving sensitivity when the reflected laser spectrum L1b for DVD is received is S1, and the light receiving sensitivity when the transmitted laser spectrum L2b for CD is received is S2, the spectral characteristics of the dichroic beam splitter 3 are as follows. Similarly, it can be expressed by equation (8).

  As described above, the dichroic beam splitter 3 obtains the spectral characteristics satisfying the expression (8), so that the monitor light receiving element 4 can perform the reflection laser spectrum L1b for DVD and the transmission laser spectrum L2b for CD as laser spectrum. The photoelectric signal having the same current value can be generated regardless of whether the light is received.

  Accordingly, in the front monitor circuit 20, a signal processing path (that is, the current / voltage conversion circuit 30, the variable resistor 24, and the voltage amplification circuit 31) that performs processing after the photoelectric conversion processing by the monitoring light receiving element 4 is connected to one signal processing system. It can be a road.

  Further, when the signal level of the monitor signal is corrected, the front monitor circuit 20 only corrects the signal level of one of the monitor laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD, The correction content of laser spectroscopy can be reflected as it is.

  In the above configuration, when the DVD laser unit 2a emits the DVD laser light L1, the optical disc apparatus 10 uses the dichroic beam splitter 3 to split a part of the DVD laser light L1 as the DVD reflection laser spectrum L1b. Then, the monitor light receiving element 4 of the front monitor circuit 20 receives the reflected laser spectrum L1b for DVD.

  Further, when the CD laser unit 2b emits the CD laser beam L2, the optical disc apparatus 10 splits a part of the CD laser beam L2 from the CD laser beam L2 as the CD transmission laser beam L2b by the dichroic beam splitter 3, and the front monitor. The monitoring light-receiving element 4 of the circuit 20 receives the CD transmission laser spectrum L2b.

  At this time, the optical disk apparatus 10 uses the dichroic beam splitter 3 to convert the DVD laser light L1 and the CD laser light L2, and the monitor light receiving element 4 selects either the DVD reflection laser spectrum L1b or the CD transmission laser spectrum L2b. Even if the light is received, the light is split into a reflected laser spectrum L1b for DVD and a transmitted laser spectrum L2b for CD having such a light quantity as to generate photoelectric signals having the same current value.

  Therefore, the optical disk device 10 receives the received DVD reflected laser spectrum L1b and CD transmitted laser beam regardless of whether the monitor light receiving element 4 receives the reflected laser spectrum L1b for DVD or the transmitted laser spectrum L2b for CD. The spectral L2b can be photoelectrically converted to generate a photoelectric signal having the same current value.

  As a result, the optical disk apparatus 10 generates a monitor signal having the same signal level in the front monitor circuit 20 based on the photoelectric signal corresponding to any received light of the reflection laser spectrum L1b for DVD and the transmission laser spectrum L2b for CD. be able to.

  Therefore, when the optical signal apparatus 10 corrects the signal level of the monitor signal in consideration of the variation in the light receiving sensitivity of the monitor light receiving element 4, the front monitor circuit 20 uses the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD. By correcting the signal level of any one of the originally generated monitor signals, the correction of the signal level can be reflected in other monitor signals.

  In other words, the optical disk apparatus 10 can correct the signal level of the monitor signal that has to be performed multiple times as many times as the number of types of optical disks 19 that can be used for recording and reproduction. Therefore, the optical disk apparatus 10 can reduce the amount of monitor signal correction work performed at the time of manufacture in the factory, product inspection, product repair, and the like, thereby improving workability.

  According to the above configuration, in the optical disc apparatus 10, the DVD laser light L1 and the CD laser light L2 are obtained by the dichroic beam splitter 3, and the monitor light receiving element 4 is the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD. Regardless of which light is received, the light is split into the reflected laser spectrum L1b for DVD and the transmitted laser spectrum L2b for CD with such a light quantity as to generate photoelectric signals having the same current value. As a result, the optical disk device 10 has the same signal level based on the photoelectric signal having the same current value, regardless of whether the monitor light receiving element 4 receives the reflected laser spectrum L1b for DVD or the transmitted laser spectrum L2b for CD. The monitor signal can be generated, and as a result, the correction of the signal level can be reflected in the other monitor signals only by correcting the signal level of any one of the monitor signals. Therefore, the optical disc apparatus 10 can simplify the monitor signal correction operation.

  Further, the optical disk device 10 corrects the signal level of any one of the monitor signals and reflects the correction of the signal level on the other monitor signals, so that the front monitor circuit 20 is based on the photoelectric signal. Only one signal processing path for generating the monitor signal is provided. Therefore, the optical disc apparatus 10 can simplify the configuration of the front monitor circuit 20.

  Further, the optical disc apparatus 10 is provided with one variable resistor 24 for correcting the signal level of the monitor signal with respect to the front monitor circuit 20. Therefore, the optical disc apparatus 10 can further simplify the circuit configuration of the front monitor circuit 20.

(5) Other embodiment (5-1) Other embodiment 1
In the above-described embodiment, the case where the front monitor circuit 20 having one signal processing path and one variable resistor 24 is provided for the optical disc apparatus 10 has been described.

  However, the present invention is not limited to this, and the optical disk apparatus is provided with a front monitor circuit having two or more signal processing paths and two or more variable resistors that are currently popular in the market, and any one signal processing path is provided. And only one corresponding variable resistor may be used.

  According to such a configuration, two or more signal processing paths and two or more variable resistors that are widely used in the market can be provided without particularly preparing the front monitor circuit 20 having one signal processing path and one variable resistor 24. The optical pickup and the optical disc apparatus of the present invention can be easily realized by diverting the front monitor circuit having the same.

(5-2) Other Embodiment 2
In the embodiment described above, the case where the antireflection film is formed on the dichroic beam splitter 3 so as to satisfy the above-described expression (8) has been described.

  However, the present invention is not limited to this. For the dichroic beam splitter 3, in consideration of the production yield, the equation (9)

  R1 / T2≈ (Po2 · S2) / (Po1 · S1) (9)

An antireflection film may be formed to satisfy the above.

(5-3) Other Embodiment 3
Further, in the embodiment described above, the case where the optical pickup according to the present invention is applied to the optical pickup 1 in the optical disc apparatus 10 provided in the notebook computer described above with reference to FIGS. 1 to 4 has been described.

  However, the present invention is not limited to this, an optical disk device provided in a desktop computer, an optical disk device externally attached to a computer, etc., an optical disk device capable of recording and / or reproducing information with respect to two or more types of optical disks, The present invention can be widely applied to optical pickups provided in optical disk apparatuses having various configurations such as a recording apparatus capable of recording information on an optical disk and a reproducing apparatus capable of reproducing information from the optical disk.

(5-4) Other Embodiment 4
Further, in the embodiment described above, the case where the optical disk apparatus according to the present invention is applied to the optical disk apparatus 10 provided in the notebook type computer described above with reference to FIGS. 1 to 4 has been described.

  However, the present invention is not limited to this, an optical disk device provided in a desktop computer, an optical disk device externally attached to a computer, etc., an optical disk device capable of recording and / or reproducing information with respect to two or more types of optical disks, The present invention can be widely applied to optical disk apparatuses having various configurations such as a recording apparatus capable of recording information on an optical disk and a reproducing apparatus capable of reproducing information from the optical disk.

(5-5) Other Embodiment 5
Further, in the above-described embodiment, lasers provided in the DVD laser unit 2a and the CD laser unit 2b described above with reference to FIGS. 1 to 4 as at least two laser light sources that emit laser beams having different wavelengths, respectively. The diodes 5a and 5b are applied.

  However, the present invention is not limited to this, and includes two or more laser light sources formed on one semiconductor substrate such as a monolithic integrated type two-wavelength laser, a DVD system, a CD system, and a Blu-ray disc (wavelength 405 nm) system. In addition to these three types of laser light sources, and in addition to these three types of laser light sources corresponding to the DVD, CD, and Blu-ray disc methods, there are various other types such as two types of laser light sources arbitrarily combined. The laser light source can be widely applied.

(5-6) Other Embodiment 6
Further, in the above-described embodiment, the objective lens 18 described above with reference to FIGS. 1 to 4 is applied as a condensing lens that condenses laser beams having different wavelengths emitted from two or more laser light sources.

  However, the present invention is not limited to this, and various other condensing lenses can be widely applied as long as laser beams having different wavelengths emitted from two or more laser light sources can be condensed.

(5-7) Other Embodiment 7
Further, in the above-described embodiment, a part of the laser beams having different wavelengths emitted from the two or more laser light sources are arranged in the middle of the optical path between the two or more laser light sources and the condenser lens, respectively. The dichroic beam splitter 3 described above with reference to FIGS. 1 to 4 is applied as a spectroscopic element that performs spectroscopy for monitoring the emission power of the laser light.

  However, the present invention is not limited to this, and other various types such as a prism type or wedge substrate type beam splitter, an optical element other than the beam splitter, a spectroscopic element formed by combining a plurality of optical elements, and the like. The spectroscopic element can be widely applied.

  That is, as shown in FIG. 5, a prism type beam splitter 32 may be provided for the optical pickup 33. Even in such a configuration, the same effect as that of the above-described embodiment can be obtained by forming the reflection film and / or the transmission film so as to satisfy the above-described expression (8) for the beam splitter 32.

(5-8) Other embodiment 8
Furthermore, in the above-described embodiment, as a light receiving element that receives a laser spectrum split from each laser beam having a different wavelength by the spectroscopic element and generates a photoelectric signal by photoelectrically converting the received laser spectrum, FIG. The photodiode described above with reference to FIGS. 1 to 4 was applied.

  However, the present invention is not limited to this, and various other light receiving elements such as phototransistors can be widely applied.

(5-9) Other Embodiment 9
Further, in the above-described embodiment, the front monitor circuit described above with reference to FIGS. 1 to 4 is used as a monitoring signal generation unit that generates a power monitoring signal used for monitoring the light emission power based on the photoelectric signal generated by the light receiving element. Twenty current / voltage conversion circuits 30 are applied.

  However, the present invention is not limited to this, and a current having two signal processing paths as described above can be generated as long as the power monitoring signal used for monitoring the emission power can be generated based on the photoelectric signal generated by the light receiving element. A wide variety of other monitor signal generation units such as a voltage / voltage conversion circuit can be used.

(5-10) Other Embodiment 10
Furthermore, in the above-described embodiment, the variable resistor 24 described above with reference to FIGS. 1 to 4 is applied as a correction unit for correcting the signal level of the power monitoring signal generated by the monitoring signal generation unit.

  However, the present invention is not limited to this, and various other configuration correction units can be widely applied as long as the signal level of the power monitoring signal generated by the monitoring signal generation unit can be corrected.

(5-11) Other Embodiment 11
Further, in the above-described embodiment, the APC circuit described above with reference to FIGS. 1 to 4 is applied as a power control unit that controls the light emission power of the laser light emitted from the laser light source based on the photoelectric signal generated by the light receiving element. I tried to do it.

  However, the present invention is not limited to this, and the power control unit having various other configurations can be widely applied as long as the emission power of the laser beam emitted from the laser light source can be controlled based on the photoelectric signal generated by the light receiving element. can do.

  The present invention can be used for an optical pickup and an optical disk apparatus that are compatible with the DVD system and the CD system.

1 is a block diagram showing an embodiment of the overall configuration of an optical disc apparatus according to the present invention. It is an optical block diagram which shows the structure (1) of an optical pick-up. It is an optical block diagram which shows the structure (2) of an optical pick-up. It is a block diagram which shows the circuit structure of a front monitor circuit. It is an optical block diagram which shows the structure of the optical pick-up by other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical pick-up, 2a ... Laser unit for DVD, 2b ... Laser unit for CD, 3 ... Dichroic beam splitter, 4 ... Light receiving element for monitor, 10 ... Optical disk device, 19 ... Optical disk, 20 ... ... front monitor circuit, 24 ... variable resistance, 30 ... current / voltage conversion circuit.

Claims (5)

At least two laser light sources each emitting laser light having different wavelengths;
A condenser lens for condensing the laser beams having different wavelengths emitted from the two or more laser light sources;
A part of the laser beams having different wavelengths emitted from the two or more laser light sources are arranged in the middle of the optical path between the two or more laser light sources and the condensing lens, respectively, to emit light of the laser light. A spectroscopic element that performs spectroscopy for power monitoring;
A light receiving element that receives the laser spectrum split from each of the laser beams having different wavelengths by the spectral element and generates a photoelectric signal by photoelectrically converting the received laser spectrum;
The spectroscopic element is
Even if a part of the laser beams having different wavelengths emitted from the two or more laser light sources is photoelectrically converted by receiving any of the laser spectra having different wavelengths, the photoelectric signals having the same value can be obtained. An optical pickup that splits the laser spectrum with a light amount that generates a signal. Based on the photoelectric signal generated by the light receiving element, a monitoring signal generating unit that generates a power monitoring signal used for monitoring the light emission power;
The optical pickup according to claim 1, further comprising: a correction unit configured to correct a signal level of the power monitoring signal generated by the monitoring signal generation unit. The monitoring signal generator is
Only one signal processing path for generating the power monitoring signal based on the photoelectric signal is generated, and any of the laser spectra having different wavelengths is photoelectrically converted by the light receiving element to generate the photoelectric signal. The optical pickup according to claim 2, wherein the power monitoring signal is generated based on the photoelectric signal so that the generated photoelectric signal is taken into the one signal processing path. The correction unit is
The optical pickup according to claim 3, comprising one variable resistor whose resistance value can be adjusted from the outside. At least two or more laser light sources that emit laser beams having different wavelengths, a condensing lens that condenses the laser beams having different wavelengths emitted from the two or more laser light sources, the two or more laser light sources, and the above Spectroscopy that is arranged in the middle of the optical path with the condenser lens and that separates a part of the laser beams having different wavelengths emitted from the two or more laser light sources as a laser spectrum for monitoring the emission power of the laser light. An optical pickup having an element and a light receiving element that receives the laser spectrum separated from each of the laser beams having different wavelengths by the spectral element and generates a photoelectric signal by photoelectrically converting the received laser spectrum When,
A power control unit for controlling the light emission power of the laser beam emitted from the laser light source based on the photoelectric signal generated by the light receiving element;
The spectral element of the optical pickup is:
Even if a part of the laser beams having different wavelengths emitted from the two or more laser light sources is photoelectrically converted by receiving any of the laser spectra having different wavelengths, the photoelectric signals having the same value can be obtained. An optical disk device for performing spectroscopy on the laser spectroscopy with a light amount that generates a signal.

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