JP4598350B2 - I / V conversion circuit, optical head, and recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording / reproducing apparatus for recording / reproducing various information on / from an optical recording medium, an optical head provided in various optical devices such as the recording / reproducing apparatus, and an I / V conversion circuit provided in the optical head.
[0002]
[Prior art]
An optical head incorporated in a CD player or a CD-ROM player is a light receiving element for irradiating a CD or CD-ROM as an optical recording medium with a light beam from a light source and reflecting the reflected beam from the optical recording medium. The detection signal is output by detecting at.
When the CD player or CD-ROM player has only a reproduction function, the level of the detection signal detected by the optical head is controlled by controlling the emission power of the light beam emitted to the optical recording medium to be constant. Is affected by variations in characteristics of the optical head including the light source and variations in reflectance of the optical recording medium. The influence is, for example, about ± 3 to ± 6 dB as the level fluctuation of the detection signal.
[0003]
On the other hand, the following signals are detected by an optical head incorporated in a CD-R or CD-RW drive. That is, an RF signal, a focus error signal, a tracking error signal, and an ATIP signal.
The RF signal includes an RF signal for reproduction (referred to as an RRF signal) used for detecting data of the optical recording medium at the time of reproduction, and light emitted from a light source by detecting a recording state with respect to the optical recording medium at the time of recording. There are two types of recording RF signals (referred to as WRF signals) used to control the beam output power.
8 is a waveform diagram of the WRF signal, FIG. 12A is a waveform diagram of the output power of the light beam, and FIG. 12B is a waveform diagram of the WRF signal corresponding to (A).
As shown in FIG. 8 and FIG. 12, the WRF signal has a peak level (corresponding to B in FIG. 12B) when the light beam has an emission power for recording a pit (corresponding to data 1). As the time passes, the reflectance decreases due to the change in the pigment in the pit portion, so that a flat pit level (corresponding to C in FIG. 12B) is obtained. Then, in a portion where no pit is formed between pits (corresponding to data 0), the emission power of the light beam is lowered to the same read level as that of the RRF signal (corresponding to A in FIG. 12B). The Control of the emission power of the light beam at the time of recording is performed based on the monitor signal detected by sampling the pit level. This control is called Running OPC processing.
[0004]
By the way, as the speed of CD-R and CD-RW drive devices increases, the light beam emission power at the time of recording increases with respect to the light beam emission power at the time of reproduction. The difference in signal level is widening. The light beam during reproduction is constant regardless of the number of rotations. For example, as shown in FIG. 9, it can be seen that the emission power (vertical axis) of the light beam increases with respect to the multiple of the rotational speed of the CD-R (horizontal axis).
[0005]
The detection signal detected by the light receiving element of the optical head is converted from a current signal to a voltage signal and amplified by an I / V conversion circuit. If this amplification factor is optimally set during reproduction, recording is performed. Sometimes the amplified voltage signal is saturated. Therefore, the I / V conversion circuit is configured to switch the amplification factor between reproduction and recording in order to avoid saturation of the voltage signal.
FIG. 10 is a circuit diagram showing an example of a conventional I / V conversion circuit.
As shown in FIG. 10, the I / V conversion circuit 10 I / V converts and amplifies each of the detection signals (current signals) from the light receiving elements 1002A to 1002H constituting the light detection means to detect the detection signal A. Or a plurality of amplifying means 1004 for outputting as G, and a summing amplifying means 1010 for outputting as RF signals by adding and amplifying the voltage signals output from the amplifying means 1004 of the light receiving elements 1002A to 1002D. Has been.
Each of the amplifying means 1004 is configured to be switched between a high amplification factor for reproduction and a low amplification factor for recording in accordance with the control signal SW.
According to such a configuration, detection signals A to G and RF signal amplification factors for generating servo control signals used for the purpose of servo control such as tracking error signals, focus error signals, and ATIP signals can be obtained. The degree of freedom of setting can be increased.
[0006]
Also, as shown in FIG. 11, the summing and amplifying means is composed of a recording-time adding and amplifying means 1010A and 1010B independently, so that a WRF signal at the time of recording and an RRF at the time of reproduction are obtained. There is also an I / V conversion circuit 10A that further increases the degree of freedom in setting the amplification factor of the WRF signal and the RRF signal by allowing the signals to be set independently.
[0007]
[Problems to be solved by the invention]
In such conventional I / V conversion circuits 10 and 10A, each detection signal is set by setting a high amplification factor so as to obtain a signal level as high as possible within a range in which the pit level and the read level at the time of recording are not saturated. The signal quality is improved.
Therefore, as shown in FIGS. 13A and 13B, the detection signals A to D are often saturated at the peak level. Therefore, the settling time to the sampling point at the pit level is important. It is.
However, not only the saturation recovery in the amplifier circuit corresponding to each light receiving element but also the noise generated by delaying the recovery due to saturation of the addition amplifier circuit is mixed into each detection signal of the I / V conversion circuit. There is a risk of adverse effects. The noise is mixed into each detection signal in the I / V conversion circuit or in a wiring portion including a flexible substrate for transmitting a signal from the I / V conversion circuit to a subsequent circuit.
[0008]
Also in the configuration of FIG. 11, as shown in FIGS. 13C and 13D, even when the WRF signal is not saturated at the time of recording, the amplification factor of the reproduction amplifying means 1010B has a high value. Since the RRF signal is set, the RRF signal is saturated, and noise generated thereby may adversely affect each detection signal of the I / V conversion circuit.
Since these noises are generated at the boundary between the pits and the non-pits (the boundary between data 1 and data 0), they are mixed into the sampling points of each detection signal, and thereby the signal quality required for servo control is reduced. It will cause deterioration.
The present invention has been made in view of such a situation, and optimizes the level of a detection signal output from an I / V conversion circuit without being affected by noise both during recording and during reproduction. It is an object of the present invention to provide an I / V conversion circuit, an optical head, and a recording / reproducing apparatus that can perform recording.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an I / V conversion circuit according to the present invention achieves the above-described object, a light source that emits a light beam, an objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium, and the irradiation In an I / V conversion circuit provided in an optical head comprising: a light detection means including a plurality of light receiving elements that receive a reflected light beam of the light beam reflected on the optical recording medium through the objective lens; An amplifying unit provided for each of a plurality of current signals input from each of a plurality of light receiving elements, converting each of the plurality of current signals into a voltage signal, and a voltage signal output from the plurality of amplifying units Selected from Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The addition amplification means is configured such that the amplification factor of the addition amplification means can be switched between a reproduction amplification factor and a recording amplification factor, and a voltage signal output from the addition amplification means is an RF signal. Amplification of addition amplification means rate Switching light Performed in conjunction with recording and playback of information on the recording medium, The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying means and the adding amplifying means is set so as not to reach a saturation state both at the time and at the time of reproduction in which a laser beam of reproduction power is irradiated. It is characterized by that.
[0010]
The optical head of the present invention includes a light source that emits a light beam, an objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium, and the optical recording of the irradiated light beam. Photodetection means including a plurality of light receiving elements that receive a reflected light beam from the medium through the objective lens, and an I / V conversion circuit that converts current signals input from the plurality of light receiving elements into voltage signals The I / V conversion circuit is provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converts each of the plurality of current signals into a voltage signal. And amplifying means for outputting and selected from the voltage signals outputted from the plurality of amplifying means Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The addition amplification means is configured such that the amplification factor of the addition amplification means can be switched between a reproduction amplification factor and a recording amplification factor, and a voltage signal output from the addition amplification means is an RF signal. Amplification of addition amplification means rate Switching light Performed in conjunction with recording and playback of information on the recording medium, The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying means and the adding amplifying means is set so as not to reach a saturation state both at the time and at the time of reproduction in which a laser beam of reproduction power is irradiated. It is characterized by that.
[0011]
Further, the recording / reproducing apparatus of the present invention irradiates the optical recording medium rotated and driven by the driving means while holding the optical recording medium, and the reflected light from the optical recording medium. An optical head for detecting the light source, the optical head emitting a light beam, an objective lens for condensing the light beam emitted from the light source and irradiating the optical recording medium, and the irradiated Light detection means including a plurality of light receiving elements for receiving a reflected light beam of the light beam on the optical recording medium through the objective lens, and converting a current signal input from the plurality of light receiving elements into a voltage signal The I / V conversion circuit converting circuit is provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and each of the plurality of current signals is a voltage signal. Convert to And amplifying means for, selected from among the voltage signal output from said plurality of amplifying means Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The addition amplification means is configured such that the amplification factor of the addition amplification means can be switched between a reproduction amplification factor and a recording amplification factor, and a voltage signal output from the addition amplification means is an RF signal. Amplification of addition amplification means rate Switching light Performed in conjunction with recording and playback of information on the recording medium, The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying means and the adding amplifying means is set so as not to reach a saturation state both at the time and at the time of reproduction in which a laser beam of reproduction power is irradiated. It is characterized by that.
[0012]
Therefore, according to the present invention, the voltage signal output from each amplification unit and the voltage signal output from the addition amplification unit do not saturate in any state during recording and reproduction with respect to the optical disc. In addition, the recording gain, reproduction gain, recording gain, and reproduction gain can be optimized. Further, by preventing the voltage signal output from the addition amplification means during recording and reproduction from reaching a saturated state, noise generated by the saturated state can be suppressed.
[0013]
The I / V conversion circuit of the present invention includes a light source that emits a light beam, an objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium, and In the I / V conversion circuit provided in the optical head provided with the light detection means including a plurality of light receiving elements for receiving the reflected light beam on the optical recording medium through the objective lens, the plurality of light receiving elements Provided for each of a plurality of current signals input from each of the plurality of current signals, and amplifying means for converting each of the plurality of current signals into a voltage signal and outputting the voltage signal, and selecting from among the voltage signals output from the plurality of amplifying means Was Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The summing amplification means has an amplification factor of the summing amplification means. For gain for recording The addition amplification means is configured to be switchable between an operation state in which the amplification operation by the addition amplification means is performed and a non-operation state in which the amplification operation is stopped, and is output from the addition amplification means At the time of recording The voltage signal is an RF signal, The RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit, Amplification of said summing amplification means Rate and operating state of the summing amplifier Switching light Performed in conjunction with recording and playback of information on the recording medium, The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. It is set so that the voltage signal output from the amplification means and the addition amplification means does not reach a saturation state at any time of reproduction in which a power laser beam is irradiated. It is characterized by that.
[0014]
The optical head of the present invention includes a light source that emits a light beam, an objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium, and the optical recording of the irradiated light beam. Photodetection means including a plurality of light receiving elements that receive a reflected light beam from the medium through the objective lens, and an I / V conversion circuit that converts current signals input from the plurality of light receiving elements into voltage signals The I / V conversion circuit is provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converts each of the plurality of current signals into a voltage signal. And amplifying means for outputting and selected from the voltage signals outputted from the plurality of amplifying means Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The summing amplification means has an amplification factor of the summing amplification means. For gain for recording The addition amplification means is configured to be switchable between an operation state in which the amplification operation by the addition amplification means is performed and a non-operation state in which the amplification operation is stopped, and is output from the addition amplification means At the time of recording The voltage signal is an RF signal, The RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit, Amplification of said summing amplification means And the operating state and non-operating state of the summing amplification means Switching light Performed in conjunction with recording and playback of information on the recording medium, The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. It is set so that the voltage signal output from the amplification means and the addition amplification means does not reach a saturation state at any time of reproduction in which a power laser beam is irradiated. It is characterized by that.
[0015]
Further, the recording / reproducing apparatus of the present invention irradiates the optical recording medium rotated and driven by the driving means while holding the optical recording medium, and the reflected light from the optical recording medium. An optical head for detecting the light source, the optical head emitting a light beam, an objective lens for condensing the light beam emitted from the light source and irradiating the optical recording medium, and the irradiated Light detection means including a plurality of light receiving elements for receiving a reflected light beam of the light beam on the optical recording medium through the objective lens, and converting a current signal input from the plurality of light receiving elements into a voltage signal The I / V conversion circuit converting circuit is provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and each of the plurality of current signals is a voltage signal. Convert to And amplifying means for, amplifying means for converting each of the plurality of current signal into a voltage signal, selected from among the voltage signal output from said plurality of amplifying means Four Each of the amplifying means is configured such that the amplification factor of the amplifying means can be switched between a reproduction amplification factor and a recording amplification factor, and The summing amplification means has an amplification factor of the summing amplification means. For gain for recording The addition amplification means is configured to be switchable between an operation state in which the amplification operation by the addition amplification means is performed and a non-operation state in which the amplification operation is stopped, and is output from the addition amplification means At the time of recording The voltage signal is an RF signal, The RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit, Amplification of said summing amplification means And the operating state and non-operating state of the summing amplification means Switching light Performed in conjunction with recording and playback of information on the recording medium, The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. It is set so that the voltage signal output from the amplification means and the addition amplification means does not reach a saturation state at any time of reproduction in which a power laser beam is irradiated. It is characterized by that.
[0016]
Therefore, according to the present invention, the voltage signal output from each amplification unit and the voltage signal output from the addition amplification unit do not saturate in any state during recording and reproduction with respect to the optical disc. In addition, the recording gain, reproduction gain, recording gain, and reproduction gain can be optimized. Further, by preventing the voltage signal output from the addition amplification means during recording and reproduction from reaching a saturated state, noise generated by the saturated state can be suppressed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an I / V conversion circuit, an optical head, and a recording / reproducing apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 2 is a block diagram showing a configuration of an optical disc recording / reproducing apparatus incorporating the I / V conversion circuit and the optical head in the first embodiment of the present invention. The optical disk recording / reproducing apparatus shown in FIG. 2 is an example of a recording / reproducing apparatus in which an optical head described below can be mounted.
[0018]
In FIG. 2, the recording / reproducing apparatus 101 includes a spindle motor 103 as driving means for rotationally driving an optical disk 102 as an optical recording medium, an optical head 104, and a feed motor 105 as driving means. Here, the spindle motor 103 is driven and controlled by the system controller 107 and the servo controller 109, and is rotated at a predetermined rotational speed.
[0019]
The signal modulation / demodulation unit and the ECC block 108 perform signal modulation, demodulation, and addition of ECC (error correction code). The optical head 104 irradiates the signal recording surface of the rotating optical disk 102 with light according to the signal modulation and the instruction of the ECC block 108. Recording and reproduction with respect to the optical disc 102 are performed by such light irradiation.
The optical head 104 detects various light beams as described later based on the reflected light beam from the signal recording surface of the optical disc 102 and supplies signals corresponding to the respective light beams to the preamplifier unit 120.
[0020]
The preamplifier unit 120 is a servo control signal based on a detection signal corresponding to each light beam, that is, a focus error signal, a tracking error signal, an RF signal, and the monitor signal (hereinafter referred to as R-OPC signal) necessary for the Running OPC process. In other words, an ATIP signal necessary for controlling the rotation of the optical disc during recording can be generated. The processing of these signals will be described later.
Depending on the type of recording medium to be reproduced, predetermined processing such as demodulation and error correction processing based on these signals is performed by the servo control unit 109, the signal modulation and ECC block 108, and the like.
Thereby, the demodulated recording signal is sent to the external computer 130 or the like via the interface 111 if it is for data storage of a computer, for example. Thus, the external computer 130 or the like can receive a signal recorded on the optical disc 102 as a reproduction signal.
Further, the preamplifier unit 120 is in a recording mode for recording information on the optical disk 102 and a control signal SW (FIG. 1) indicating that it is in a reproduction mode for reproducing information recorded on the optical disk 102. ) To the I / V conversion circuit 20 (FIG. 1).
[0021]
For audio / visual use, the digital / analog conversion is performed by the D / A conversion unit of the D / A / A / D converter 112 and supplied to the audio / visual processing unit 113. Audio / video signal processing is performed by the audio / visual processing unit 113 and transmitted to an external imaging / projection device via the audio / visual signal input / output unit 114.
The optical head 104 is connected to a feed motor 105 for moving to a predetermined recording track on the optical disk 102, for example. Control of the spindle motor 103, control of the feed motor 105, and control of the focusing direction and tracking direction of the biaxial actuator that holds the objective lens of the optical head 104 are performed by the servo control unit 109, respectively.
That is, the servo control unit 109 controls the spindle motor 103 based on the ATIP signal, and controls the biaxial actuator based on the focus error signal and the tracking error signal.
The laser control unit 121 controls the laser light source in the optical head 104. In particular, in this example, the laser control unit 121 performs an operation of controlling the emission power of the laser light source during recording and during reproduction. In recording, the output power of the laser light source is controlled based on the R-OPC signal generated from the WRF signal.
[0022]
FIG. 3 is a block diagram showing the optical system of the optical head according to the first embodiment of the present invention.
In FIG. 3, an optical head 104 includes a laser light source 1, a grating element 2, a collimator lens 3, a beam splitter 4, an objective lens 5, light detection means 6, and an I / V conversion circuit 20 described later. The component is mounted on a holder (not shown).
Various known methods can be used for tracking error detection and focus error detection. In this example, the tracking error signal is detected by the DPP (Differential Push-Pull) method, and the focus error signal is detected. Is detected by the astigmatism (Astigma) method.
[0023]
In the optical head 104, the light beam emitted from the laser light source 1 passes through the grating element 2, is separated into one main beam and two side beams, passes through the collimator lens 3 and the beam splitter 4, and is supplied to the objective lens. The reflected light beam irradiated onto the optical disk 102 through 5 and reflected by the optical disk 102 is separated by the beam splitter 4 through the objective lens 5 and guided to the light detection means 6.
[0024]
FIG. 4 is a plan view showing the configuration of the light detection means.
As shown in FIG. 4, the light detection means 6 includes a single substrate 62 and three detectors 6402, 6404, 6406 that are linearly spaced on one surface of the substrate 62. It has.
The central detector 6402 receives the main beam, is formed in a rectangular shape that is divided into four in a square shape, and includes four light receiving elements 64A to 64D.
A detection unit 6404 adjacent to one side of the detection unit 6402 receives one of the two side beams, has a rectangular shape divided into two, and is a light receiving element on the side close to the detection unit 6402 64F and a light receiving element 64E far from the detection unit 6402.
A detection unit 6406 adjacent to the other side of the detection unit 6402 receives the other of the two side beams, has a rectangular shape divided into two, and has a light receiving element 64G close to the detection unit 6402. The light receiving element 64H is located far from the detection unit 6402.
The light receiving elements 64A to 64H are configured to output a current signal corresponding to the amount of received light as a detection signal. The current signals output from the light receiving elements 64A to 64H are current signals A to H, respectively. To do.
[0025]
FIG. 1 is a circuit diagram showing a configuration of an I / V conversion circuit according to the first embodiment.
As shown in FIG. 1, the I / V conversion circuit 20 includes eight amplifying units 22A to 22H and one addition amplifying unit 24.
The photodetecting means 6 and the I / V conversion circuit 20 may constitute a so-called PDIC (photo detector IC) in which these are integrally provided, or are separated from each other. Also good.
Each of the amplifying means 22A to 22H is configured to current-voltage convert and amplify each of the detection signals A to H output from the light receiving elements 64A to 64H.
[0026]
Since each of the amplifying means 22A to 22H has the same configuration, the amplifying means 22A will be described.
The amplifying unit 22A includes an amplifier 2202, two feedback resistors 2204 and 2206 that determine an amplification factor, and a switch unit 2208 that selectively connects the two feedback resistors 2204 and 2206 to the amplifier 2202. ing.
The switch means 2208 is configured to perform a switching operation in conjunction with the state of the control signal SW input from the preamplifier 120, that is, the recording mode or the reproduction mode.
When the feedback resistor 2204 is selected by the switch unit 2208, the amplification factor of the amplification unit 22A becomes the recording amplification factor Aw, and when the feedback resistor 2206 is selected, the amplification factor of the amplification unit 22A is the reproduction factor. Is configured to have a high amplification factor Ar.
Accordingly, each of the amplifying means 22A to 22H amplifies the detection signals A to H output from the light receiving elements 64A to 64H by current-voltage conversion. The detection signals A to H amplified by the amplifying means are input to the preamplifier 120, and the processing described later is performed.
[0027]
The summing amplifier 24 includes an amplifier 2402, two feedback resistors 22404 and 2406 for determining an amplification factor, switch means 2408 for selectively connecting the two feedback resistors 2404 and 2406 to the amplifier 2402, and the detection signal. The four input resistors 2410 for inputting each of A to D are provided.
The switch means 2408 is configured to perform a switching operation in conjunction with the state of the control signal SW input from the preamplifier 120, that is, the recording mode or the reproduction mode.
When the feedback resistor 2404 is selected by the switch unit 2408, the gain of the summing amplifier 24 becomes the recording gain Asw. When the feedback resistor 2406 is selected, the gain of the amplifier 24 is It is configured to have a high amplification factor Asr.
Thereby, the adding and amplifying means 24 adds and amplifies the four detection signals A to D output from the amplifying means 22A to 22D, and inputs them to the preamplifier 120 as RF signals.
[0028]
FIG. 5 is an explanatory diagram showing an outline of the flow of signal processing performed by the preamplifier unit 120 for each detection signal and RF signal output from the I / V conversion circuit 20 in the first embodiment.
At the time of reproduction, the RF signal (A + B + C + D) output from the summing amplifier 24 is equalized as an RRF signal by the equalizer 120A, binarized by the comparator 120B, and output as a demodulated signal.
At the time of recording, the RF signal (A + B + C + D) output from the summing amplifier 24 is input to the peak hold and bottom hold circuit 120C as a WRF signal, and the level at the pit level is sampled, thereby causing R-OPC. A signal is generated and output to the laser controller 121. Thereby, the emission power of the laser light source 1 at the time of recording is controlled.
[0029]
At the time of recording, the gain signal of the sum signal (A + D) of the detection signals A and D and the sum signal (B + C) of the detection signals B and C are respectively controlled by the AGC circuits 120D and 120E, and the difference between these two sum signals is And output as an ATIP signal. The ATIP signal is a wobbling detection signal having a fixed period formed by a pre-groove formed in an unrecorded CD-R, and is input to the servo control unit 109.
The servo control unit 109 controls the rotation of the spindle motor 103 so that the ATIP signal has a predetermined cycle.
During recording and reproduction, a difference signal (A + C) − (B + D) between the sum signal of the detection signals A and C and the sum signal of the detection signals B and D is input to the servo control unit 109 as a focus error signal. The This is due to the astigmatism method.
At the time of recording and reproduction, “the difference signal (main push-pull signal) between the sum signal of the detection signals A and D and the sum signal of the detection signals B and C” is (A + D) − (B + C), When the difference signal (side push-pull signal) between the sum signal of the detection signals E and G and the sum signal of the detection signals F and H is (E + G) − (F + H), (A + D) − (B + C) -K ((E + G)-(F + H)) is input to the servo control unit 109 as a tracking error signal. This is due to the DPP method.
[0030]
According to the first embodiment configured as described above, the amplification means 22A is configured to be switched between the recording amplification factor Aw and the reproduction amplification factor Ar, and addition amplification. The means 24 is configured to be switched between a recording amplification factor Asw and a reproduction amplification factor Asr. Accordingly, the recording amplification factor Aw and the reproduction amplification are performed so that the detection signals A to H and the RF signal (A + B + C + D) are not saturated in any state during recording and reproduction with respect to the optical disc. The rate Ar, the recording gain Asw, and the reproduction gain Asr can be optimized.
In addition, since neither the WRF signal output at the time of recording or the RRF signal output at the time of reproduction from the summing amplifier 24 reaches the saturation state, noise generated by the saturation state is detected by each detection signal of the I / V conversion circuit. Therefore, it is advantageous in improving the signal quality required for servo control.
Further, the conventional I / V conversion circuit 10A shown in FIG. 11 is configured to have two addition amplification means, that is, a recording addition amplification means 1010A and a reproduction addition amplification means 1010B. Since the summing and amplifying means 24 is sufficient, the number of parts and the number of wiring patterns can be reduced, which is advantageous for simplification, miniaturization, cost reduction, and power consumption reduction of the I / V conversion circuit. Further, when the I / V conversion circuit according to the present invention is configured as a PDIC integrated with the light receiving element of the light detection means, it is advantageous in reducing the size, cost and power consumption of the PDIC. .
[0031]
Here, a specific example is given and demonstrated about the amplification factor of each said amplification means and addition amplification means.
A CD-R disc is used as the optical disc.
Guide grooves are pre-formed on the CD-R disc. Data is recorded in a non-groove portion, that is, a groove portion where the return light level is lowered by diffraction by a radial contrast with respect to the land, that is, a groove.
Land output is I _LAND , Groove output I _GROOVE Then, the radial contrast RC is expressed by the formula (1). Note that * is an operation symbol for multiplication.
RC = (I _LAND -I _GROOVE ) / (2 * (I _LAND + I _GROOVE )) (1)
However, RC> 0.2 is specified.
Of the recorded signal, the upper side of 11T, which is the maximum output, is I _TOP I in the formula (1) _LAND Indicates the same value.
Also, 11T and 3T peak-to-peak ₁₁ , I ₃ Called
I ₃ / I _TOP = 0.3-0.7
I ₁₁ /ITOP≧0.6
It is prescribed.
[0032]
Here, the output of each detection signal is determined by setting the reproduction gain as GH, the emission power of the laser light source during reproduction as Pr, the gain during recording as GL, and the emission power of the laser light source as recording as Pw. become that way.
At the time of reproduction, it is necessary to obtain a detection signal having a necessary level from a state where the focus and tracking servos are not applied to a state where they are applied. Therefore, as a condition that the focus error signal is not saturated,
GH * 2 * I _TOP * Pr <Vmax (2)
At the time of recording, in order to obtain an R-OPC signal, it is necessary that each detection signal does not saturate at the pit level (C in FIG. 12B). Therefore, as a condition that each detection signal is not saturated,
GL * K * (I _TOP -I ₁₁ * Pw <Vmax (3)
K is a margin that allows for a difference in the output level of the light receiving element, such as 1.5.
Temporarily I ₁₁ / I _TOP = 0.7, the equation (3) becomes GL * 1.5 * 0.3I _TOP * Rewritten as Pw, and when the output power at the time of recording at 24 × speed is Pw = 43 mW and the output power Pr at the time of reproduction is 1 mW, GH: GL = 1: (1 / 9.7).
If the detection signal RF output from the addition amplification means is, for example, RF = (A + B + C + D) / 4, the saturation condition can be considered in the same way, and in order to obtain the same detection signal at the time of both recording and reproduction, GH : GL = 1: (1 / 9.7) is preferable.
[0033]
However, as another consideration, at the time of 8 × recording, the RF signal amplification circuit in the subsequent stage of the I / V conversion circuit is designed so as not to contradict the recording / reproduction level. : Designed so that there is no problem with GL = 1: 1. Therefore, it is only necessary to lower GL on the I / V conversion circuit side for further speedup from here.
For example, GH: GL = 1: (1 / 2.2) at 24 × speed and GH: GL = 1: (1 / 2.2.9) at 32 × speed.
Accordingly, when the amplification factor of each detection signal is switched between recording and reproduction as described above, GH: GL = 1: (1 / 2.9) is obtained at 32 × speed, so GH: GL = 1 :( Compared with 1 / 9.7), the ratio of the level during reproduction to the level during recording of the RF signal is 9.7 / 2.9 = 3.3, which is three times or more.
That is, it is necessary to set the amplification factor at the time of recording to three times or more with respect to the amplification factor at the time of reproduction of the addition amplification means.
[0034]
Next, a second embodiment will be described.
The second embodiment differs from the first embodiment in that only the generation of the WRF signal is performed in the I / V conversion circuit, and the RRF signal is performed in the subsequent stage of the I / V conversion circuit. The summing amplification means for generating is configured so as not to operate during reproduction.
FIG. 6 is a circuit diagram showing the configuration of the I / V conversion circuit of the second embodiment. FIG. 7 shows the detection signals and RF signals output from the I / V conversion circuit of the second embodiment. It is explanatory drawing which shows the outline of the flow of the signal processing performed by a preamplifier part.
In FIGS. 6 and 7, the same parts as those in FIGS. 1 and 5 showing the first embodiment will be described with the same reference numerals.
As shown in FIG. 6, the I / V conversion circuit 20 </ b> A includes eight amplification units 22 </ b> A to 22 </ b> H and one addition amplification unit 26.
The light detection means 6 and the I / V conversion circuit 20A may be configured as a PDIC or may be configured separately from each other, as in the first embodiment.
The configuration of the amplifying means 22A to 22H is the same as that of the first embodiment, and a description thereof will be omitted.
[0035]
The addition amplification means 26 includes an amplifier 2602 whose amplification factor is fixed to the recording amplification factor Asw, and four input resistors 2604 for inputting the detection signals A to D, respectively. The control signal SW input from the preamplifier 120 is switched between operation and non-operation in conjunction with the state of the control signal SW, that is, the recording mode or the reproduction mode.
Therefore, when the control signal SW indicates the recording state, the addition amplifying unit 26 adds the four detection signals A to D output from the amplifying units 22A to 22D and enters the operation state. Amplification is performed at the amplification factor Asw, and this is input to the preamplifier 120 as a WRF signal.
On the other hand, when the control signal SW indicates a reproduction state, the addition amplifying unit 26 performs an addition and amplification operation of the four detection signals A to D output from the amplifying units 22A to 22D by being inoperative. Since this is not performed, no output is performed.
[0036]
As shown in FIG. 7, the detection signals A to D output from the I / V conversion circuit 20A at the time of reproduction are added by an addition amplifier circuit (not shown) provided in the preamplifier unit 120, and the reproduction amplification factor Asr is obtained. Is equalized by the equalizer 120A as an RRF signal (A + B + C + D), binarized by the comparator 120B, and output as a demodulated signal.
At the time of recording, the RF signal (A + B + C + D) output from the addition amplifying means 26 is input as a WRF signal to the peak hold and bottom hold circuit 120C, whereby the level at the pit level is sampled, thereby R-OPC. A signal is generated and output to the laser controller 121. Thereby, the emission power of the laser light source 1 at the time of recording is controlled.
Servo control during recording and reproduction is performed in the same manner as in the first embodiment.
[0037]
According to the second embodiment configured as described above, the amplification means 22A is configured to be switched between a recording amplification factor Aw and a reproduction amplification factor Ar, and the addition. The amplifying means 26 is configured such that the gain of the addition amplifying means 26 is fixed to the recording gain Asw, and can be switched between an operating state and a non-operating state in which the amplifying operation is stopped by the control signal SW. ing.
Accordingly, as in the first embodiment, the recording is performed so that the detection signals A to H and the RF signal (A + B + C + D) do not saturate in any state during recording and reproduction with respect to the optical disc. The time amplification factor Aw, the reproduction gain Ar, the recording gain Asw, and the reproduction gain Asr can be optimized.
In addition, since the WRF signal output from the addition amplifier 24 during recording does not reach a saturated state, noise generated by the saturated state does not adversely affect each detection signal of the I / V conversion circuit. This is advantageous in improving the signal quality required for servo control.
Further, the conventional I / V conversion circuit 10A shown in FIG. 11 is configured to have two addition amplification means, that is, a recording addition amplification means 1010A and a reproduction addition amplification means 1010B. Since only the adding and amplifying means 26 is required, the number of parts and the number of wiring patterns can be reduced, which is advantageous for simplification, miniaturization, cost reduction, and power consumption reduction of the I / V conversion circuit. Further, when the I / V conversion circuit according to the present invention is configured as a PDIC integrated with the light receiving element of the light detection means, it is advantageous in reducing the size, cost and power consumption of the PDIC. .
[0038]
【The invention's effect】
As described above, according to the present invention, the level of the detection signal output from the I / V conversion circuit can be optimized without being affected by noise during both recording and reproduction.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating a configuration of an I / V conversion circuit according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of an optical disc recording / reproducing apparatus incorporating the I / V conversion circuit and the optical head in the first embodiment of the present invention.
FIG. 3 is a configuration diagram showing an optical system of the optical head according to the first embodiment of the invention.
FIG. 4 is a plan view showing a configuration of light detection means.
FIG. 5 is an explanatory diagram showing an outline of a flow of signal processing performed by a preamplifier unit for each detection signal and RF signal output from the I / V conversion circuit in the first embodiment.
FIG. 6 is a circuit diagram showing a configuration of an I / V conversion circuit according to a second embodiment.
FIG. 7 is an explanatory diagram showing an outline of a flow of signal processing performed by a preamplifier unit for each detection signal and RF signal output from the I / V conversion circuit in the second embodiment.
FIG. 8 is a waveform diagram of a WRF signal.
FIG. 9 is a diagram showing the relationship between the output power of a light beam (during recording) and the multiple of the rotational speed of the CD-R.
FIG. 10 is a circuit diagram showing an example of a conventional I / V conversion circuit.
FIG. 11 is a circuit diagram showing another example of a conventional I / V conversion circuit.
12A is a waveform diagram of output power, and FIG. 12B is a waveform diagram of a WRF signal.
13A is a waveform diagram of output power, FIG. 13B is a waveform diagram of each detection signal, FIG. 13C is a waveform diagram of a WRF signal, and FIG. 13D is a waveform diagram of an RRF signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser light source, 5 ... Objective lens, 6 ... Light detection means, 104 ... Optical head, 64A thru | or 64H ... Light receiving element, 20 ... I / V conversion circuit, 22A thru | or 22H ... Amplification means, 24, 26... Addition amplifying means, A to H.

Claims (30)

A light source that emits a light beam; an objective lens that condenses the light beam emitted from the light source and irradiates the optical recording medium; and In an I / V conversion circuit provided in an optical head provided with a light detection means including a plurality of light receiving elements that receive light through a lens,
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means is configured such that the amplification factor of the addition amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The voltage signal output from the summing amplifier is an RF signal,
The switching of the amplification factor of the amplifying unit and the addition amplifying unit is performed in conjunction with recording and reproduction of information on the optical recording medium,
The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying unit and the addition amplifying unit is set so as not to reach a saturation state both at the time of reproduction and at the time of reproduction irradiated with a laser beam of reproduction power. I / V conversion circuit.   2. The I / V conversion circuit according to claim 1, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means.   3. The I / V conversion circuit according to claim 2, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal.   The light detecting means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements disposed on the side closer to and far from the first light receiving part, and the addition amplification means 2. The I / V conversion circuit according to claim 1, wherein the plurality of voltage signals added in step 1 correspond to current signals output from each of the four light receiving elements constituting the first light receiving unit.   The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 2. The apparatus according to claim 1, wherein the information recorded on the optical recording medium is reproduced by setting the reproduction power smaller than the recording power. / V conversion circuit. A light source that emits a light beam; an objective lens that condenses the light beam emitted from the light source and irradiates the optical recording medium; and In an I / V conversion circuit provided in an optical head provided with a light detection means including a plurality of light receiving elements that receive light through a lens,
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means has an amplification factor of the addition amplification means fixed to a recording amplification factor ,
The addition amplification means is configured to be switchable between an operation state in which an amplification operation is performed by the addition amplification means and a non-operation state in which the amplification operation is stopped,
The voltage signal at the time of recording output from the addition amplification means is an RF signal, and the RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit,
Switching between the amplification factor of the addition amplification means and the operation state and non-operation state of the addition amplification means is performed in conjunction with recording and reproduction of information on the optical recording medium,
The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. The I / V is set so that the voltage signal output from the amplifying means and the adding amplifying means does not reach a saturation state at any time of reproduction with irradiation of a power laser beam. Conversion circuit. 7. The I / V conversion circuit according to claim 6, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means. 8. The I / V conversion circuit according to claim 7, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal. The light detecting means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements disposed on the side closer to and far from the first light receiving part, and the addition amplification means 7. The I / V conversion circuit according to claim 6 , wherein the plurality of voltage signals added by the step corresponds to a current signal output from each of the four light receiving elements constituting the first light receiving unit. The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 7. The apparatus according to claim 6, wherein the information recorded on the optical recording medium is reproduced by setting the reproduction power smaller than the recording power. / V conversion circuit. A light source that emits a light beam, an objective lens that condenses the light beam emitted from the light source and irradiates the optical recording medium, and a reflected light beam of the irradiated light beam on the optical recording medium is the objective. An optical head comprising: a light detection unit including a plurality of light receiving elements that receive light through a lens; and an I / V conversion circuit that converts a current signal input from the plurality of light receiving elements into a voltage signal. ,
The I / V conversion circuit is
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means is configured such that the amplification factor of the addition amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The voltage signal output from the summing amplifier is an RF signal,
The switching of the amplification factor of the amplifying unit and the addition amplifying unit is performed in conjunction with recording and reproduction of information on the optical recording medium,
The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying unit and the addition amplifying unit is set so as not to reach a saturation state both at the time of reproduction and at the time of reproduction irradiated with a laser beam of reproduction power. And optical head. 12. The optical head according to claim 11, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means. 13. The optical head I / V conversion circuit according to claim 12, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal. The light detecting means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements disposed on the side closer to and far from the first light receiving part, and the addition amplification means 12. The optical head according to claim 11 , wherein the plurality of voltage signals added by the step corresponds to a current signal output from each of the four light receiving elements constituting the first light receiving unit. The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 12. The light according to claim 11, wherein the information recorded on the optical recording medium is reproduced by setting the reproduction power smaller than the recording power. head. A light source that emits a light beam, an objective lens that condenses the light beam emitted from the light source and irradiates the optical recording medium, and a reflected light beam of the irradiated light beam on the optical recording medium is the objective. An optical head comprising: a light detection unit including a plurality of light receiving elements that receive light through a lens; and an I / V conversion circuit that converts a current signal input from the plurality of light receiving elements into a voltage signal. ,
The I / V conversion circuit is
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means has an amplification factor of the addition amplification means fixed to a recording amplification factor ,
The addition amplification means is configured to be switchable between an operation state in which an amplification operation is performed by the addition amplification means and a non-operation state in which the amplification operation is stopped,
The voltage signal at the time of recording output from the addition amplification means is an RF signal, and the RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit,
Switching between the amplification factor of the addition amplification means and the operation state and non-operation state of the addition amplification means is performed in conjunction with recording and reproduction of information on the optical recording medium,
The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. An optical head characterized in that the voltage signal output from the amplifying means and the adding and amplifying means is set so as not to reach a saturation state at any time of reproduction with irradiation of a power laser beam . 17. The optical head according to claim 16, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means. 18. The optical head according to claim 17, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal. The light detecting means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements disposed on the side closer to and far from the first light receiving part, and the addition amplification means 17. The optical head according to claim 16 , wherein the plurality of voltage signals added by the step correspond to current signals output from each of the four light receiving elements constituting the first light receiving unit. The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 17. The light according to claim 16, wherein the information recorded on the optical recording medium is reproduced by setting the reproduction power smaller than the recording power. head. Driving means for holding and rotating the optical recording medium;
An optical head that irradiates light to the optical recording medium that is rotationally driven by the driving means and detects reflected light from the optical recording medium;
The optical head is
A light source that emits a light beam;
An objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium;
A light detection means including a plurality of light receiving elements for receiving the reflected light beam of the irradiated light beam on the optical recording medium through the objective lens;
An I / V conversion circuit that converts current signals input from the plurality of light receiving elements into voltage signals;
The I / V conversion circuit conversion circuit includes:
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means is configured to be switchable between an operation state in which an amplification operation is performed by the addition amplification means and a non-operation state in which the amplification operation is stopped,
The voltage signal output from the summing amplifier is an RF signal,
The switching of the amplification factor of the amplifying unit and the addition amplifying unit is performed in conjunction with recording and reproduction of information on the optical recording medium,
The reproduction amplification factor and the recording amplification factor of the amplification means, and the reproduction amplification factor and the recording amplification factor of the addition amplification means are recorded by irradiating the optical recording medium with a laser beam of recording power. The voltage signal output from the amplifying means and the adding amplifying means is set so as not to reach a saturation state both at the time and at the time of reproduction in which a laser beam of reproduction power is irradiated. A recording / reproducing apparatus. The recording / reproducing apparatus according to claim 21, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means. The recording / reproducing apparatus according to claim 22, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal. The light detection means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements arranged on the side closer to and far from the first light receiving part, and the addition amplification means 23. The recording / reproducing apparatus according to claim 21 , wherein the plurality of voltage signals added by the step corresponds to current signals output from each of the four light receiving elements constituting the first light receiving unit. The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 22. The recording according to claim 21, wherein the information recorded on the optical recording medium is reproduced by being set to a reproduction power smaller than the recording power. Playback device. Driving means for holding and rotating the optical recording medium;
An optical head that irradiates light to the optical recording medium that is rotationally driven by the driving means and detects reflected light from the optical recording medium;
The optical head is
A light source that emits a light beam;
An objective lens that collects the light beam emitted from the light source and irradiates the optical recording medium;
A light detection means including a plurality of light receiving elements for receiving the reflected light beam of the irradiated light beam on the optical recording medium through the objective lens;
An I / V conversion circuit that converts current signals input from the plurality of light receiving elements into voltage signals;
The I / V conversion circuit conversion circuit includes:
Amplifying means provided for each of a plurality of current signals input from each of the plurality of light receiving elements, and converting each of the plurality of current signals into a voltage signal;
A single summing amplifier for adding and outputting four voltage signals selected from the voltage signals output from the plurality of amplifiers;
Each of the amplification means is configured such that the amplification factor of the amplification means can be switched between a reproduction amplification factor and a recording amplification factor,
The addition amplification means has an amplification factor of the addition amplification means fixed to a recording amplification factor ,
The addition amplification means is configured to be switchable between an operation state in which an amplification operation is performed by the addition amplification means and a non-operation state in which the amplification operation is stopped,
The voltage signal at the time of recording output from the addition amplification means is an RF signal, and the RF signal at the time of reproduction is formed by adding the selected four voltage signals outside the I / V conversion circuit,
Switching between the amplification factor of the addition amplification means and the operation state and non-operation state of the addition amplification means is performed in conjunction with recording and reproduction of information on the optical recording medium,
The amplification factor for reproduction and the amplification factor for recording of the amplification means and the amplification factor for recording of the addition amplification means are those for recording when the optical recording medium is irradiated with a laser beam of recording power and for reproduction. A recording / reproducing apparatus, wherein the voltage signal output from the amplifying unit and the addition amplifying unit is set so as not to reach a saturation state at any time of reproduction with irradiation of a power laser beam. . 27. The recording / reproducing apparatus according to claim 26, wherein a servo control signal is generated based on a voltage signal output from each of the plurality of amplifying means. 28. The recording / reproducing apparatus according to claim 27, wherein the servo control signal includes at least one of a tracking error signal, a focus error signal, and an ATIP signal. The light detecting means includes a first light receiving portion and second and third light receiving portions provided at positions sandwiching the first light receiving portion, and the first light receiving portion is shaped like a square. The four light receiving elements are arranged, and each of the second and third light receiving parts is composed of the two light receiving elements disposed on the side closer to and far from the first light receiving part, and the addition amplification means 27. The recording / reproducing apparatus according to claim 26 , wherein the plurality of voltage signals added by the step corresponds to a current signal output from each of the four light receiving elements constituting the first light receiving unit. The optical head records information on the optical recording medium by setting the emission power of the light beam emitted from the light source to the recording power, and the emission power of the light beam emitted from the light source is 27. The recording according to claim 26, wherein the information recorded on the optical recording medium is reproduced by setting the reproduction power smaller than the recording power. Playback device.

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