JP2001307345A - Disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disk reproducing device which can perform tracking control and focus control with high precision. SOLUTION: The disk reproducing device is quipped with photodetecting elements E, F, A and B which output analog output signals varying with the quantity of light made incident in return light from a disk 2 and PDM signal generating circuits 15TE, 15TF, 15FA, and 15FB which are provided corresponding to the respective photodetecting elements and composed of delta-sigma modulating circuits respectively and convert the analog output signals of the photodetecting elements into 1-bit signal; and a light beam is focused on a target track of the disk by driving an objective lens 4 according to tracking error signals and focus error signal generated by applying prescribed arithmetic operations to the outputs of the PDM signal generating circuits respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk reproducing apparatus for reading information recorded on a disk, and more particularly to a disk reproducing apparatus for controlling focus and tracking of an objective lens of a pickup. .

[0002]

2. Description of the Related Art FIG.
This will be described below with reference to FIG.

[0003] A part of the reflected light irradiated on a disk (not shown) enters a tracking light detector 100T and a focusing light detector 100F. These photodetectors 10
OT and 100F are provided in a pickup (not shown), and are constituted by photodiodes E and F and A and B, and their outputs are current signals. The current signal is supplied to IV converters 101TE, 101TF, 101TF provided on the main circuit board of the main unit so that AD conversion can be performed in a subsequent stage.
FA, 101FB, and converted into a voltage signal by the converter.

An IV converter is generally constituted by an operational amplifier (operational amplifier) not shown, and a current signal and an output signal of the operational amplifier are inputted to one input terminal of the operational amplifier via a resistor (not shown). Along with
A reference voltage (not shown) is input to the other input terminal. In the case of a single power supply, the reference voltage is 1 of the power supply voltage.
/ 2 is generally used. Therefore, IV
The converter operates using three supply voltages, a supply voltage, a ground voltage, and a reference voltage.

[0005] The signals converted into voltage signals are supplied to anti-aliasing filters 102TE, 102TF, 102F.
A and 102FB, where high-frequency components are cut by a low-pass filter having a steep cutoff characteristic in high frequencies so that aliasing does not occur in successive approximation type AD converters 104T and 104F at the subsequent stage. The cut signal is input to multiplexers 103T and 103F,
Two signals are alternately output to the successive approximation A / D converters 104T and 104F as one series of signals in time series.

As the AD converter, a successive approximation type AD converter is generally used. This is because a multi-series analog signal can be digitized in time series using a multiplexer. This successive approximation type AD converter compares a comparison voltage of a DA converter corresponding to a weight of a balance with a voltage of an input analog signal and digitizes the same. The supply voltage to the circuit to be compared is only the power supply voltage and the ground voltage, and no reference voltage is applied. In other words, a reference voltage may be supplied to a successive approximation type AD converter for a certain type of DA converter, or a reference voltage may be supplied to a successive approximation type AD converter for a very special purpose. The reference voltage is not supplied to the portion of the comparison type AD converter which performs pure AD conversion.

The signals from the photodetectors 100T and 100F are digitized as described above and then input to the phase compensation circuits 105T and 105F, respectively.
Here, a difference signal between the two signals shifted in time series is obtained (a tracking error signal and a focus error signal), and the tracking error signal and the focus error signal are phase-compensated by a DSP (digital signal processor). , A tracking drive signal and a focus drive signal are generated.

The above-mentioned tracking drive signal and focus drive signal are converted into PWM signal generation circuits 106T and 106T.
The signals are converted into PWM signals by F, and drive signals are respectively generated in the tracking drive circuit 107T and the focus drive circuit 107F based on the PWM signals. Then, tracking control and focus control are performed by these drive signals.

The anti-aliasing filters 102TE, 102TF, 102FA,
And the circuits from 102FB to the tracking drive circuits 107T and 107F are incorporated in one LSI chip together with other circuits (for example, signal processing circuits). On the other hand, the IV converter 101TE, 101TF, 10
1FA and 101FB are not provided in this LSI chip. These are the IV converters 101TE, 101T
The reason is that the signals handled by F, 101FA, and 101FB are minute signals and are not affected by noise from a circuit that handles large power such as a signal processing circuit. That is, the IV converters 101TE, 101TF, 101FA,
And 101FB and successive approximation type AD converters 104T and 1
04F is arranged on the same main circuit board,
They are not provided in the same LSI chip. Further, as described above, one operates with three supply voltages and the other operates with two supply voltages.

[0010]

However, in order to accurately read a signal recorded on a disk, focus control and tracking control must be performed accurately. In order to implement this, it is necessary not to increase the cost and to prevent an increase in power consumption.

In the above prior art, an optical signal for generating a focus error signal and a tracking error signal is photoelectrically converted by a photodetector, further converted into a current voltage by an IV converter, and then successively compared. Then, the focus error signal and the tracking error signal are generated by obtaining the difference signal.

As described above, products that process focus error signals and tracking error signals with digital signals instead of analog signals are increasing. This is because the tracking servo and the focus servo can be improved in accuracy and cost can be reduced. When generating the focus error signal and the tracking error signal into a digital signal, the successive approximation type A
It is common to use a D converter.

That is, as described above, by using a multiplexer, a multi-sequence signal can be processed by one AD converter. In the above conventional example, two series of signals are processed by one successive approximation type A / D converter, but there are also four series, that is, products in which all sequences of tracking and focus signals are processed by one successive approximation type A / D converter. Can be seen.

Although there is a double integration method as an AD conversion method, the disk reproducing technique is not satisfactory in terms of high-speed processing and accuracy, and the successive approximation type is far superior to the double integration method. Therefore, there is no product that does not use a successive approximation type AD converter among products that digitize and process a tracking error signal or a focus error signal.

Although not purely technical, successive approximation type A
There are other reasons why only D converters are used. that is,
This means that LSI manufacturers are conservative. At present, LSI manufacturers have established a digitizing technology using a successive approximation type AD converter corresponding to a tracking servo and a focus servo, and do not want to dare to take risks. That is, there is a stereotype throughout the industry that the digitization of the tracking error signal and the focus error signal uses a successive approximation type AD converter.

At present, it has been described that the LSI maker has established a digitization technique using a successive approximation type AD converter corresponding to a tracking servo and a focus servo, but it is only possible to digitize.
It does not mean that the technology to create a truly accurate AD converter has been established.

However, the successive approximation type A
This does not mean that the D converter itself is an AD converter with low accuracy. On the contrary, many successive approximation type AD converters manufactured by specialized manufacturers have high accuracy.

As is well known, the successive approximation type AD converter performs a data comparison operation in bit units from the most significant bit (MSB) to the least significant bit (LSB). In other words, the accuracy of the successive approximation AD converter is determined by the accuracy of the weight applied to the balance. DA converters that produce weights, especially
The value of the resistor for weighting determines the accuracy. Specialized manufacturers make various efforts, such as by performing laser trimming, etc., to create the resistors with high precision. Therefore, successive approximation type A manufactured by a specialized manufacturer
On the other hand, D converters are very costly because of their high accuracy.

However, the signal processing L for disc reproduction is used.
In the SI, various processing circuits are incorporated in the LSI, and the successive approximation type AD converter as described above is one of them. Such an LSI is formed by CMOS. As a practical problem, a process for improving accuracy such as laser trimming of the resistor corresponding to the weight is practically impossible from the viewpoint of cost and the like. Therefore, a signal processing LSI for disc reproduction
The accuracy of the successive approximation type AD converter provided therein is not high. In other words, the successive approximation type AD converter provided in the signal processing LSI has a large differential error.
It can be said that it is a D converter. Therefore, more accurate tracking servo and focus servo could not be performed.

In addition to the problem relating to the accuracy of the successive approximation type AD converter, the above conventional example has the following problems.

In the case of tracking, the processing of the signals relating to the photodiodes E and F cannot be performed simultaneously, and in the case of focusing, the processing of the signals relating to the photodiodes A and B must be performed simultaneously. There is a problem that it cannot be performed.

The above multiplexers 103T and 103F
As a result, the signals are separated in time series, so that one signal becomes a difference signal having a value shifted by one step from the other signal. The difference between the tracking error signal and the focus error signal which should be generated at the same time should be taken, but this cannot be done due to the presence of the multiplexers 103T and 103F. In order to cope with this, it is conceivable to provide a successive approximation type AD converter for each stream. However, the advantage of the successive approximation type AD converter that can process multi-sequence signals cannot be utilized, and the cost is greatly increased.

Further, in the above-mentioned prior art, phase distortion of group delay occurs due to the anti-aliasing filter.
That is, the frequency and the time delay do not have a linear relationship, thereby causing phase distortion and deteriorating the servo characteristics. To overcome this problem, if you do oversampling,
Similarly, it is costly.

Further, the IV converters 101TE, 101
The TF, 101FA, and 101FB require three supply voltages, while the successive approximation AD converters 104T and 104F require two supply voltages. In other words, when the power supply fluctuates, between the two (the IV converter and the AD converter)
An offset occurs between the converters), and a highly accurate error signal cannot be obtained. As a result, highly accurate control cannot be performed.

At present, many discs having a high recording density have been proposed, and in view of the demand for higher recording density in the future, it is urgently necessary to improve servo characteristics.

[0026]

In order to solve the above-mentioned problems, a plurality of disk reproducing devices according to the present invention are provided for tracking and focusing, respectively, and are provided in accordance with the amount of incident light among the return light from the disk. And a plurality of light-receiving elements which are provided corresponding to the respective light-receiving elements and which are each constituted by a delta-sigma modulation circuit and convert the analog output signal of each of the light-receiving elements into a 1-bit signal. An objective lens is driven based on a tracking error signal and a focus error signal generated by performing a predetermined operation on the output of the AD converter, and a light beam is projected on a target track of the disk. And an objective lens drive control means for focusing the object.

According to the above invention, the objective lens is driven by the objective lens drive control means based on the tracking error signal and the focus error signal, and the light beam is focused on the target track of the disk. At this time, the return light from the disk is guided to the light receiving element via the objective lens, where an analog output signal that changes according to the amount of incident light is output.

Conventionally, the plurality of analog output signals have been sent to a single successive approximation type A / D converter via a multiplexer and converted into digital signals. In the successive approximation type AD converter, it is necessary to increase the accuracy of the resistance value for weighting in order to increase the conversion accuracy.
For this purpose, laser trimming or the like is performed. Therefore, the successive approximation type A / D converter is very costly because the accuracy is increased.

On the other hand, according to the present invention, since the AD converter is constituted by the delta-sigma modulation circuit, the above-mentioned conventional measures for improving the accuracy are not required, so that the cost is increased. Can be reliably avoided.

Conventionally, a plurality of analog output signals are sent to a single successive approximation type A / D converter via a multiplexer, where they are converted into digital signals in a time series. For this reason, it has not been possible to simultaneously process a plurality of analog output signals. The inability to perform simultaneous processing on a plurality of analog output signals reduces the accuracy of the tracking error signal and the focus error signal. To cope with this, it is conceivable to provide a successive approximation type AD converter for each light receiving element. However, it is originally assumed that the processing of a plurality of analog output signals is performed by a single successive approximation type A / D converter via a multiplexer. Therefore, it is not possible to provide a successive approximation type A / D converter for each light receiving element. This violates the above premise. In addition, if the number of successive approximation type AD converters is increased, the cost will increase accordingly.

Therefore, according to the above invention, an AD converter constituted by a delta-sigma modulation circuit is provided for each light receiving element. Therefore, since the AD converter can be realized with a simple configuration, it does not increase the cost,
Simultaneous processing can be performed on a plurality of analog output signals, and the accuracy of the tracking error signal and the focus error signal can be increased.

This is effective when the AD converter is provided on the same LSI chip as the tracking and focus processing circuits. When the AD converter is provided on the same LSI chip as the tracking and focus processing circuits, if the AD converter is constituted by a successive approximation type AD converter, laser trimming of a resistor or the like is performed to increase the accuracy. However, such processing is practically impossible from the viewpoint of cost and the like. Therefore, the accuracy of the successive approximation type AD converter in the LSI cannot be said to be high.
That is, it can be said that the successive approximation AD converter provided in the signal processing LSI is an AD converter having a large differential error. Therefore, more accurate tracking servo and focus servo could not be performed.

On the other hand, according to the present invention, since the AD converter is constituted by the delta-sigma modulation circuit, the above-described processing for improving the accuracy is unnecessary.
Even if the AD converter is integrated with various other processing circuits, the AD converter has a small differential error. Therefore, it is possible to perform more accurate tracking servo and focus servo based on the 1-bit signal output from the AD converter.

Conventionally, an anti-aliasing filter has been provided so that aliasing does not occur in the successive approximation type AD converter at the subsequent stage.
Since the converter is configured, such an anti-aliasing filter is not required. As a result, it is possible to overcome a problem inherent to the anti-aliasing filter, in which phase distortion due to group delay is generated and servo characteristics are deteriorated, without increasing costs.

The disc reproducing apparatus further includes a decimation filter which receives a 1-bit signal from the AD converter and outputs a PCM signal having a low sampling frequency, and the decimation filter includes a high-frequency noise of the 1-bit signal. And a low-pass filter for removing
PCM conversion means for converting a bit signal into a PCM signal;
It is preferable to include a thinning means for thinning the PCM signal.

In this case, when the one-bit signal output from the AD converter is input to the decimation filter, the high-frequency noise of the one-bit signal is removed by the low-pass filter. The output signal of this low-pass filter is PC
It is converted into a PCM signal by the M conversion means. And
The PCM signal is thinned out by thinning means. This decimation outputs a PCM signal with a low sampling frequency from the decimation filter. The reason for performing this thinning is that when a predetermined phase compensation process is performed on a PCM signal with a high sampling frequency, too much hardware is required. The thinning means reduces such a demand for hard work.

There is no time lag between the plurality of PCM signals obtained as described above, and a predetermined operation is performed on these PCM signals to obtain a tracking error signal and a focus error signal with high accuracy. The drive of the objective lens is controlled based on this.

In the above-mentioned disk reproducing apparatus, an analog amplifier is provided for each of the light-receiving elements, is constituted by an operational amplifier, and performs a current-voltage conversion on an analog output signal of each of the light-receiving elements input to its inverting input terminal. A current-voltage conversion circuit for outputting to the converter, wherein the AD converter includes:
An integrator circuit configured by an operational amplifier for integrating the output of the current-voltage conversion circuit input to its inverting input terminal; and an integrator circuit configured by an operational amplifier to output the integrator circuit input to its inverting input terminal. A quantization circuit for performing quantization,
A delay unit that delays the output of the quantization circuit and outputs the one-bit signal as the one-bit signal, and feeds back the one-bit signal to the inverting input terminal of the operational amplifier of the integration circuit. It is preferable that a common reference voltage is input to each non-inverting input terminal.

In this case, when the power supply voltage fluctuates due to a change in the environment, the reference voltage fluctuates accordingly. However, even in such a case, since the common reference voltage is input to the non-inverting input terminals of the three operational amplifiers, no offset occurs between the operational amplifiers. Therefore, a highly accurate tracking error signal and a focus error signal can be generated.

Further, since the AD converter can be constituted by a very simple circuit as described above, the area is smaller than that of a case where the AD converter is constituted by a successive approximation AD converter. From this, LS
The cost of manufacturing I can be kept low, and power consumption can be reduced.

In the above disk reproducing apparatus, the above AD
The converter is composed of an operational amplifier, performs current-voltage conversion on the analog output signal of each of the light receiving elements input to its inverting input terminal, integrates the converted voltage signal, and an operational amplifier. A quantization circuit configured to quantize the output of the integration circuit input to the inverting input terminal thereof;
A delay device that outputs a bit signal, a delay capacitor, and a switched capacitor that is provided between the inverting input terminal of the operational amplifier of the integration circuit and feeds back the 1-bit signal to the integration circuit; It is preferable that a common reference voltage is input to each non-inverting input terminal of the two operational amplifiers.

In this case, the number of operational amplifiers can be reduced because the operational amplifier of the integrating circuit is shared between the integration function and the current-voltage conversion function. When the power supply voltage changes due to a change in environment, the reference voltage also changes accordingly. However, even in such a case, since the common reference voltage is input to the non-inverting input terminals of the two operational amplifiers, no offset occurs between the operational amplifiers. Therefore, a highly accurate tracking error signal and a focus error signal can be generated.

In addition, the adoption of the switched capacitor allows the LSI to cope with variations during the manufacture of the LSI in relation to the capacitor used in the feedback section of the operational amplifier of the integration circuit. In other words, when compared with the case where feedback is performed via a resistor, a capacitor for a resistor becomes a capacitor for a capacitor, and even if there is a variation in the manufacturing of the capacitor, the two are the same, and it is possible to cancel this variation. .

The following is a specific configuration. That is, a disc reproducing apparatus irradiates a disc with a light beam and detects a return light thereof, an information signal photodetector, a tracking photodetector, and a pickup including a focusing photodetector, and the respective photodetectors , An information signal current-voltage converter, a tracking current-voltage converter, and a focus current-voltage converter for current-voltage conversion, and signal processing of the output signal of the information signal current-voltage converter. An information signal processing circuit, a tracking AD converter for inputting output signals of the tracking current-voltage converter and the focus current-voltage converter, and performing AD conversion on the information signals; a focusing AD converter; and the tracking AD conversion The input signal of the focusing device and the AD converter for focusing is input, and the track for moving the objective lens provided in the pickup is moved. Ring control circuit, and a focus control circuit, the information signal processing circuit, AD converter for tracking, AD converter for focus, tracking control circuit, and the focus control circuit in one LS
The AD converter is provided on an I chip, and is configured by a delta-sigma modulation circuit.

Another disc reproducing apparatus includes a pickup for converting information recorded on a track of a disc into an optical signal and reading the signal by finely moving an objective lens to focus a laser beam on the track of the disc; A focus control photodetector that is provided in the pickup, receives the reflected light of the laser beam irradiated on the disc, and outputs an original signal serving as a focus control signal; and an output signal of the photodetector. Is input to an inverting input terminal, and an inverting amplifier circuit having a first operational amplifier in which a common reference voltage is input to a non-inverting input terminal; and an output signal of the inverting amplifier circuit is input to an inverting input terminal.
The second common reference voltage is input to the non-inverting input terminal.
An integrating circuit having an operational amplifier; a quantizer for quantizing an output signal of the integrating circuit and outputting a quantized signal; and a delay for delaying the quantized signal and feeding it back to an inverting input terminal of the second operational amplifier. A focus control of an objective lens provided in the pickup based on the quantized signal.

Still another disk reproducing apparatus includes a pickup for converting information recorded on the track of the disk into an optical signal and reading the signal by finely moving an objective lens so that the laser beam follows the track of the disk;
A tracking control photodetector that is provided in the pickup, receives the reflected light of the laser beam irradiated on the disc, and outputs an original signal serving as a tracking control signal, and an output signal of the photodetector Is input to an inverting input terminal, and an inverting amplifier circuit having a first operational amplifier in which a common reference voltage is input to a non-inverting input terminal; and an output signal of the inverting amplifier circuit is input to an inverting input terminal.
A second reference input of the common reference voltage to a non-inverting input terminal;
An integrating circuit having an operational amplifier; a quantizer for quantizing an output signal of the integrating circuit and outputting a quantized signal; and a delay for delaying the quantized signal and feeding it back to an inverting input terminal of the second operational amplifier. And performing tracking control of an objective lens provided in the pickup based on the quantized signal.

Another disc reproducing apparatus irradiates a disc with a light beam and detects reflected light thereof, and includes a pickup including a tracking photodetector and a focusing photodetector, the pickup photodetector, and a focusing photodetector. An integrating circuit having an operational amplifier to which an output signal of the photodetector is input to an inverting input terminal; a quantizer for quantizing an output signal of the integrating circuit to output a quantized signal; and a delay circuit for delaying the quantized signal. A delay unit that feeds back to an inverting input terminal of the operational amplifier, and reference voltage generating means that inputs a common reference voltage to a non-inverting input terminal of the operational amplifier and the quantizer. The tracking control and the focus control of the objective lens provided in the pickup are performed based on.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

The disk reproducing apparatus of the present invention detects the reflected light from the disk with the photodetector, converts the output signal from the photodetector into an IV signal, digitizes the analog voltage signal, and performs focus control and tracking. Each control is performed. In order to perform this digitization, a PCM (Pulse Code Modulation) signal has been conventionally generated by a successive approximation AD converter, but this is converted to a PDM (Pulse Density) signal by a △ Σ modulator or the like.
Modulation) signal.

The disc reproducing apparatus according to the present embodiment will be described below with reference to FIGS. 1 and 2.
Reference numeral 1 denotes a light source, and a laser beam is emitted from the light source 1 toward the disk 2. The disk 2 is a disk such as a compact disk (CD), for example. Then, rotation control by CLV control or the like is performed by a spindle motor (not shown).

The laser beam is split by the first diffraction grating 3 into a main beam and two sub beams. This is what is called a three-beam system. These three beams are focused on a target track on the disk 2 by the objective lens. The light path of the reflected light from the disk 2 is changed by the second diffraction grating 10 and reaches the photodetectors 12 corresponding to the respective beams. A current signal from an RF signal photodetector (one component of the photodetector 12, not shown) is sent to an IV converter 13RF, where it is converted to a voltage signal. The voltage signal is subjected to equalizing processing and waveform shaping in an RF processing circuit 18 and sent to a signal processing circuit 19, where predetermined signal processing is performed. This signal processing circuit 19 requires a large current consumption, which becomes a noise generating source. An IV converter for capturing a small signal is provided on an LSI chip including the signal processing circuit (a portion surrounded by a chain line in FIG. 1). Is silicon
Not possible unless on-insulator processing is performed.

As shown in FIG. 1, the photodetectors include a tracking photodetector 12T and a focusing photodetector 12F in addition to the RF signal.

The laser beam is focused on the target track on the disk 2 and follows the target track because the focus control and the tracking control are performed. That is, the focus coil 5 and the tracking coil 6 are driven by the focus drive circuit 8 and the tracking drive circuit 9, and the objective lens 4 is minutely moved via the actuator 7, whereby the above control is performed.

The drive signals of the focus drive circuit 8 and the tracking drive circuit 9 are formed based on the output signals of the tracking photodetector 12T and the focus photodetector 12F. That is, the focus control and the tracking control are controlled by forming a servo loop.

The tracking detector 12T has two photodiodes E and F, and the above-described two sub-beams enter each element. Photodiode E
And F, a current signal is output according to the amount of incident light, and input to the IV converters 13TE and 13TF, respectively. The IV converters 13TE and 13TF convert the current signal into a voltage signal and output it to the PDM signal generation circuits 14TE and 14TF.

PDM signal generation circuits 14TE and 14TF
Are provided corresponding to the photodiodes E and F. That is, the PDM signal generation circuit is provided for each photodiode. PDM signal generation circuits 14TE and 1
In 4TF, the above voltage signal is converted into a PDM signal (sampling frequency 256fs, 1fs = 44.1kHz) and output to the decimation filters 15TE and 15TF, respectively.

The decimation filters 15TE and 15
The TF is formed by a DSP (Digital Signal Processor) and includes PDM signal generation circuits 14TE and 14T.
LPF that removes high-frequency noise that has been noise-shaped by F
(Low-pass filter), PCM conversion means for converting a 1-bit signal into a PCM signal, and thinning means (all not shown) for thinning out the PCM signal.
Therefore, the decimation filters 15TE and 15TF
Is a PCM signal having a low sampling frequency, and is sent to the subsequent phase compensation circuit 16T. The reason for performing this thinning is that if the phase compensation circuit performs a predetermined process with a PCM signal having a high sampling frequency, too much hardware work will be required.

Phase compensation circuit 1 formed by DSP
In 6T, a difference signal between two input PCM signals is obtained. This difference signal is generated by two PCMs with no time lag.
This is a difference signal between the signals, and is a highly accurate signal. This is called a tracking error signal, and is controlled so that this difference signal becomes zero. Phase compensation is performed so that the servo loop does not oscillate. The signal subjected to this phase compensation is a tracking drive signal.

The tracking drive signal is input to the PWM signal generation circuit 17T, converted into a PWM signal, and sent to the tracking drive circuit 9 described above. The above is the tracking servo circuit in which the loop is formed.

Next, focus control will be described.
A part of the main beam is obtained, for example, by the Foucault method or the like, so that two separate focusing beams are obtained, and the same processing as the tracking control described above is performed. The focusing detector 12F has two photodiodes A and B, and the two focusing beams enter respective elements. In the photodiodes A and B, a current signal is output according to the amount of incident light, and is input to the IV converters 13FA and 13FB, respectively. IV converter 13FA
And 13FB, the current signal is converted to a voltage signal and PD
The signals are output to the M signal generation circuits 14FA and 14FB, respectively.

PDM signal generation circuits 14FA and 14FB
Are provided corresponding to the photodiodes A and B. That is, the PDM signal generation circuit is provided for each photodiode. PDM signal generation circuits 14FA, 14
In the FB, the voltage signal is converted to a PDM signal (sampling frequency 256 fs, 1 fs = 44.1 kHz) and output to the decimation filters 15FA and 15FB, respectively.

The decimation filters 15FA and 15
The FB is formed by a DSP, an LPF that removes high-frequency noise that has been noise-shaped by the PDM signal generation circuits 14FA and 14FB, a PCM conversion unit that converts a 1-bit signal into a PCM signal, and a thinning-out unit for the PCM signal. And thinning means (both not shown). Therefore, the decimation filters 15FA and 15FA
The output signal from the FB is a PC with a low sampling frequency.
The signal becomes an M signal and is sent to the subsequent phase compensation circuit 16F. The reason for performing this thinning is that if the phase compensation circuit performs a predetermined process with a PCM signal having a high sampling frequency, too much hardware work will be required.

Phase compensation circuit 1 formed by DSP
At 6F, a difference signal between the two input PCM signals is obtained. This difference signal is composed of two Ps without time lag.
This is a difference signal of the CM signal and a highly accurate signal. This is called a focus error signal, and is controlled so that this difference signal becomes zero. Phase compensation is performed so that the servo loop does not oscillate. The signal subjected to the phase compensation is the focus drive signal.

The focus drive signal is input to the PWM signal generation circuit 17F, converted into a PWM signal, and sent to the focus drive circuit 8 described above. The above is the focus servo circuit in which a loop is formed.

Next, in the tracking control system, the output of the photodetector 12T is supplied to the IV converters 13TE and 13TF,
And PDM signal generation circuits 14TE and 14TF,
How it is converted into a PDM signal will be described below with reference to FIG.

Although FIG. 2 shows the tracking control system, it is omitted in the focus control system because the same processing is performed in the focus control system. That is, in the focus control system, the output of the photodetector 12F is converted into a PDM signal via the IV converters 13FA and 13FB and the PDM signal generation circuits 14FA and 14FB. Is the same as The basic operation concept is the same, except that the constants of the capacitor and the resistance are changed between the tracking control system and the focus control system.

The photodiode E of the photodetector 12T
In F, the output current changes according to the amount of received light (incident). In other words, the greater the amount of received (incident) light, the more
The output current increases. When the amount of light received is constant, the output current is constant even if the voltage changes. Therefore, the photodiodes EF may be equivalently considered as constant current sources.

The IV converters 13TE and 13TF are mainly composed of an operational amplifier 30 and a resistor 31, as shown in FIG. The output signals (output current) of the photodiodes EF in the photodetector 12T and the output signal of the operational amplifier 30 are fed back to the inverting input terminal of the operational amplifier 30 via the resistor 31. In this case, the resistor 3
The current-to-voltage conversion gain is determined by the resistance value of 1.
On the other hand, the reference voltage Vref is input to the non-inverting input terminal. Generally, in the case of a single power supply, half of the power supply voltage is the reference voltage Vref. For example, when the power supply voltage is 5 volts, the reference voltage Vref is 2.5 volts. And
This reference voltage Vref is obtained from a power supply voltage to a ground voltage by a voltage dividing resistor (not shown).

In this way, the IV converter 13TE · 1
The output of the 3TF is obtained by adding or subtracting the product of the output current of the photodetector 12T and the resistance value of the resistor 31 to or from the reference voltage Vref. Whether the addition or the subtraction is performed depends on the direction of the output current from the photodetector 12.

Since the operational amplifier has an imaginary short characteristic, the input voltage of the inverting input terminal of the operational amplifier 30 does not change even if the input current changes. Further, when the photodiodes EF (current sources) are subjected to IV conversion, there is no influence from the capacitor characteristics of the PN junction in the photodiodes EF. For example, when switching from a pickup called X to a pickup called Y, the type of the photodiode of the photodetector is often different. In such a case, even if the above-mentioned capacitor characteristics are changed, this effect is not affected. I will not receive it.

As described above, in the method of performing the IV conversion while obtaining the current-voltage conversion gain using the operational amplifier 30, the output current of the photodiodes EF is passed through the resistor without using the operational amplifier 30, and the current is simply applied to the voltage. After that, it is a better method than the method of amplifying the voltage. Output signals of the IV converters 13TE and 13TF (output signals of the operational amplifier 30) are input to the resistor 32 and converted into current signals. In this case, the PDM signal generation circuit 14TE
From the viewpoint of 14TF, the resistor 32 functions as a voltage-current converter.

PDM signal generation circuits 14TE and 14TF
Is an integrator comprising an operational amplifier 33 serving as an input unit and a feedback unit for feeding back the output of the operational amplifier 33 via a capacitor 34, and a comparator 35 (quantizer) for quantizing the output of the integrator. ), A D flip-flop 36 that delays the output of the comparator 35 by one step (delayed by one hour) and outputs it as a 1-bit signal, and outputs the output (1 bit signal) of the D flip-flop 36 via a resistor 37. And a feedback unit that feeds back to the input unit.

In the operational amplifier 33, the operational amplifier 30 (IV converters 13TE and 13T)
The output signal of the D flip-flop 3) is converted into a current signal via a resistor 32 and input.
The output (1 bit signal) of No. 6 is converted into a current signal via a resistor 37 and input, and the reference voltage Vref is input to a non-inverting input terminal.

As described above, the output of the photodetector 12T is converted from the D flip-flop 36 into a PDM signal (1 bit signal) and output. In the above description, a case has been described where the PDM signal generation circuits 14TE and 14TF are primary delta-sigma modulation circuits.
The present invention is not limited to this, and may be a second-order or higher-order delta-sigma modulation circuit. Which delta-sigma modulation circuit is employed depends on the required accuracy. This is determined by a balance between the number of integrators and the sampling frequency.

What is important here is that the IV converter 13TE
One power supply to each of the non-inverting input terminals of the operational amplifier 30 of 13TF, the operational amplifier 33 of the integrator in the PDM signal generation circuits 14TE and 14TF, and the comparator 35 of the quantizer (not shown). Is input. When the power supply voltage fluctuates due to a change in environment, the reference voltage Vref also fluctuates accordingly.
Even in this case, since the common reference voltage Vref is input to each of the non-inverting input terminals as described above, the components (the operational amplifier 30, the operational amplifier 33, and the comparator 35)
There is no offset between them.

The case of a single power supply has been described above. However, the present invention is not limited to this. If two power supplies are used, and one common power supply voltage and one reference voltage are applied, the offset can be reduced. This can be reliably avoided.

For example, if the zero-level signal is the photodetector 12T
Is entered. In this state, stray light from surroundings is cut off without irradiating the light beam, and the servo circuit is turned on.
Corresponding to the state. This is often used when checking the situation of occurrence of an offset on a servo circuit. In this state, basically, the D flip-flop 36 outputs a PDM signal having a duty ratio of 50%.

Thereafter, it is assumed that the environment changes and the power supply voltage fluctuates. Then, although the power supply of the pickup is different from the power supply of the main circuit board, the power supply voltage of the pickup also fluctuates in the same manner. However, the output of the photodetector 12T is
As described above, the photodetector 1 may be considered as a constant current source.
Even if the power supply voltage of 2T fluctuates, the current corresponding to the recording signal of the disk 2 remains unchanged from the IV converters 13TE and 13TF.
Is output to Then, as described above, the IV converter 1
A common reference voltage Vref obtained from one power supply by a voltage dividing resistor is input to each of the non-inverting input terminals of the 3TE / 13TF operational amplifier 30, the integrator operational amplifier 33, and the quantizer comparator 35. No offset occurs between P and P at a duty ratio of 50%.
The DM signal is output from the D flip-flop 36.

On the other hand, when the common reference voltage Vref is not applied to each of the non-inverting input terminals, the initial set values of the reference voltages supplied to the operational amplifier 30, the operational amplifier 33, and the comparator 35 are the same. However, when the environment changes, each reference voltage becomes different due to the variation of the element (voltage dividing resistor), and as a result, an offset occurs. As a result, the duty ratio of the PDM signal changes according to the generated offset, and the duty ratio of 50% collapses.

In the case of using the successive approximation type AD converter found in the prior art, this is not the case. I
In the V converter, the power supply voltage, the reference voltage, and the ground voltage
One voltage is used (even with two power supplies, there is a reference voltage). However, the reference voltage is not supplied to the successive approximation type A / D converter (some of the successive approximation type A / D converters supply the reference voltage. It is not for AD conversion, but for other purposes.) Therefore, when the power supply voltage fluctuates due to a change in the environment, the effect of canceling out each other between the fluctuations in the voltage applied to both does not work. Inevitably, an offset occurs between the two. And that becomes an error. If this error is the same in both the two systems (the tracking control system and the focus control system), there is no problem. However, the error naturally becomes different due to the variation of the elements, and it is not possible to perform highly accurate tracking control. On the other hand, according to the present embodiment, since there is no offset from the beginning, there is no need to worry about having two streams.

The above-described improvement is made by the IV converter 13TE · 1
This is caused by adopting the PDM signal generators 14TE and 14TF after the 3TF. That is, an integrator is provided in the first stage of the PDM signal generators 14TE and 14TF, and the operational amplifier 33 is used for the integrator. The IV converters 13TE and 13TF also use the operational amplifier 30, so that only one common reference voltage Vref is used.
Can be used, the occurrence of an offset therebetween can be reliably avoided, and highly accurate tracking control and focus control can be performed. Furthermore, what is important is that, besides the appropriate response to the above-mentioned environmental change, stable accuracy can be initially obtained.

Each component of the AD conversion by the delta-sigma modulation circuit does not excessively require the accuracy of the resistance corresponding to the weight of the above-described balance unlike the successive approximation type AD converter, and is usually used. With the respective elements generated by the LSI manufacturing technology, it is possible to obtain the same accuracy as a successive approximation type AD converter manufactured by a dedicated manufacturer of the successive approximation type AD converter. Therefore, the same L as other circuits such as a signal processing circuit is used.
On the SI chip, an AD converter with a small differential error and high accuracy can be provided.

Further, since it can be constituted by a very simple circuit, four delta-sigma modulation circuits corresponding to each circuit and decimation filters 15TE and 15TF
The area occupied by the LSI including the two successive approximation type A
The area is smaller than the area in the case of the D converter. Thus, the cost of manufacturing the LSI can be kept low, and the power consumption can be reduced.

Further, since the conventionally required anti-aliasing filter is not used, no phase shift data is obtained. Further, since four signals are processed simultaneously, it is not necessary to process data having different measurement times when taking the difference between the two signals. That is, not only the AD converter alone can be improved, but also the adverse effects of surrounding components can be removed.

Next, another disk reproducing apparatus according to this embodiment will be described with reference to FIG. The difference from the above-described disc reproducing apparatus is that the IV converters 13TE and 13
The operational amplifier of the TF and the operational amplifier at the first stage of the integration circuit of the delta-sigma modulation circuit (PDM signal generators 14TE and 14TF) are shared by the operational amplifier 40, and the feedback signal from the D flip-flop 43 is switched capacitor 44
, And that each processing circuit of the LSI is subjected to silicon-on-insulator processing. Of course, the operational amplifier 40 is provided on the LSI.

The output signal of the photodetector 12T is input to the operational amplifier 40, and after being directly integrated,
The PDM signal (1 bit signal) is output from the D flip-flop 43 after being quantized by the comparator 42 (quantizer). Also in this case, the common reference signal Vref is applied to each non-inverting input terminal of the operational amplifier 40 and the comparator 42.
Is entered.

As a result, the number of operational amplifiers to be used can be reduced by one as compared with the case described above. Also, by using the switched capacitor 44,
Due to the relationship with the capacitor 41 used in the feedback section of the operational amplifier 40 of the integrator, it is possible to cope with variations during LSI manufacturing. That is, from the capacitor 34 for the resistor 37 to the capacitor 41 for the capacitor 44
Thus, even if there is a variation in the manufacture of the capacitors, the two (the capacitor 44 and the capacitor 41) have the same variation, and this variation is canceled.

As described above, the first disk reproducing apparatus of the present invention comprises: (1) an information signal photodetector, a tracking photodetector, and a focus, which irradiate a light beam to a disk and detect the return light thereof. A pickup including a photodetector for (2) an output signal of the information signal, an IV converter for tracking, an IV converter for tracking, and an IV converter for focusing, which input an output signal of each of the photodetectors and perform current-voltage conversion; 3) an information signal processing circuit that performs signal processing on an output signal of the information signal IV converter; and (4) a tracking signal that inputs the output signals of the tracking IV converter and the focus IV converter and performs AD conversion. An AD converter and an AD converter for focusing; and (5) an objective lens provided with the pickup, which receives output signals of the AD converter for tracking and the AD converter for focusing. A tracking control circuit for moving, and a focus control circuit, and the information signal processing circuit, the AD converter for tracking, the AD converter for focusing, the tracking control circuit, and the focus control circuit are provided on one LSI chip; Said A
The D converter is characterized by being constituted by a delta-sigma modulation circuit.

According to the first disk reproducing apparatus, the differential error is much smaller than that of a successive approximation type AD converter provided on a large-scale integrated circuit, that is, an LSI provided mixedly with various processing circuits. A with high accuracy
A D converter can be formed, which makes it possible to perform highly accurate tracking control and focus control. In addition, it is possible to eliminate adverse effects of peripheral circuit components of the successive approximation type AD converter, and to reduce cost and power consumption.

Here, the fact that the differential error is small in the above will be described. That is, unlike the successive approximation type AD converter, each component of the AD conversion by the delta-sigma modulation circuit does not excessively require the accuracy of the resistance corresponding to the weight of the above-described balance, and is not usually used. Successive approximation type AD by each element generated by LSI manufacturing technology
Accuracy comparable to that of successive approximation type AD converters manufactured by dedicated converter manufacturers can be obtained. Therefore, a highly accurate AD converter with a small differential error can be provided on the same LSI chip as another circuit such as a signal processing circuit.

The second disk reproducing apparatus according to the present invention comprises: (1) finely moving an objective lens to focus a laser beam on a track of a disk (focus control); And (2) a focus control light provided in the pickup, which receives the reflected light of the laser beam irradiated on the disc and outputs an original signal serving as a focus control signal. A detector,
(3) an inverting amplifier circuit having a first operational amplifier in which an output signal of the photodetector is input to an inverting input terminal and a reference voltage is input to a non-inverting input terminal; and (4) an output of the inverting amplifier circuit. A signal is input to the inverting input terminal, while the first
An integration circuit having a second operational amplifier whose reference voltage is the same as the reference voltage input to the non-inverting input terminal of the operational amplifier, and (5) quantizing the output signal of the integration circuit; A quantizer that outputs a quantized signal, and (6) a delay unit that delays the quantized signal and feeds it back to an inverting input terminal of the second operational amplifier is provided, and based on the quantized signal, It is characterized in that focus control of an objective lens provided in the pickup is performed.

According to the above-described second disk reproducing apparatus, one common reference voltage can be applied to the non-inverting input terminals of the first operational amplifier and the second operational amplifier. However, stable focus control can be performed without generating an offset.

The third disk reproducing apparatus according to the present invention comprises: (1) finely moving the objective lens so that the laser beam follows the track of the disk (tracking control), thereby converting the information recorded on the track of the disk into an optical signal. A pickup for converting and reading, and (2) tracking control light detection provided in the pickup, receiving the reflected light of the laser beam irradiated to the disc, and outputting an original signal serving as a signal for tracking control, respectively. And (3) a first circuit in which an output signal of the photodetector is input to an inverting input terminal and a reference voltage is input to a non-inverting input terminal.
An inverting amplifier circuit having an operational amplifier, (4) an output signal of the inverting amplifier circuit is input to an inverting input terminal, while a reference voltage of the same level as a reference voltage input to a non-inverting input terminal of the first operational amplifier is: An integration circuit having a second operational amplifier input to a non-inverting input terminal; (5) a quantizer for quantizing an output signal of the integration circuit and outputting a quantized signal; (6)
A delay unit that delays the quantized signal and feeds it back to an inverting input terminal of the second operational amplifier, and performs tracking control of an objective lens provided in the pickup based on the quantized signal. Features.

According to the third disk reproducing apparatus, one common reference voltage can be applied to the non-inverting input terminals of the first operational amplifier and the second operational amplifier. However, stable tracking control can be performed without generating an offset.

The fourth disk reproducing apparatus of the present invention comprises: (1) a tracking photodetector for irradiating a light beam to a disc and detecting a reflected light thereof, and a pickup including a focusing photodetector; An integration circuit having an operational amplifier in which an output signal of the tracking photodetector and the focus photodetector is input to an inverting input terminal; and (3) quantizing an output signal of the integration circuit and outputting a quantized signal. A quantizer, (4) a delay unit that delays the quantized signal and feeds it back to an inverting input terminal of the operational amplifier, and (5) inputs a reference voltage to a non-inverting input terminal of the operational amplifier and the quantizer. A reference voltage generating means for performing tracking control and focus control of an objective lens provided in the pickup based on the quantized signal.

According to the fourth disk reproducing apparatus, I
Since the operational amplifier of the V converter and the operational amplifier of the integrating circuit of the delta-sigma modulation circuit are shared, the cost can be reduced.

[0097]

As described above, a plurality of disc reproducing devices according to the present invention are provided for tracking and focusing respectively, and output analog output signals which change according to the amount of incident light among the return light from the disc. A light-receiving element for outputting, and provided corresponding to each light-receiving element,
A plurality of A / D converters each constituted by a delta-sigma modulation circuit for converting the analog output signal of each of the light receiving elements into a 1-bit signal, and each of the A / D converters is generated by performing a predetermined operation on the output of the A / D converter. Object lens drive control means for driving the objective lens based on the tracking error signal and the focus error signal to focus the light beam on the target track of the disk.

According to the above invention, the objective lens is driven by the objective lens drive control means based on the tracking error signal and the focus error signal, and the light beam is focused on the target track of the disk. The return light from the target track is guided to the light receiving element via the objective lens, where an analog output signal that changes according to the amount of incident light is output.

Conventionally, the plurality of analog output signals have been sent to a single successive approximation type A / D converter via a multiplexer and converted into digital signals. In the successive approximation type AD converter, it is necessary to increase the accuracy of the resistance value for weighting in order to increase the conversion accuracy.
For this purpose, laser trimming or the like is performed. Therefore, the successive approximation type A / D converter is very costly because the accuracy is increased.

On the other hand, according to the present invention, since the AD converter is constituted by the delta-sigma modulation circuit, the above-mentioned conventional measures for improving the accuracy are not required, so that the cost is increased. Can be reliably avoided.

Conventionally, a plurality of analog output signals are sent to a single successive approximation type A / D converter via a multiplexer, where they are converted into digital signals in a time series. For this reason, it has not been possible to simultaneously process a plurality of analog output signals. The inability to perform simultaneous processing on a plurality of analog output signals reduces the accuracy of the tracking error signal and the focus error signal. To cope with this, it is conceivable to provide a successive approximation type AD converter for each light receiving element. However, it is originally assumed that the processing of a plurality of analog output signals is performed by a single successive approximation type A / D converter via a multiplexer. Therefore, it is not possible to provide a successive approximation type A / D converter for each light receiving element. This violates the above premise. In addition, if the number of successive approximation type AD converters is increased, the cost will increase accordingly.

Therefore, according to the above invention, an AD converter constituted by a delta-sigma modulation circuit is provided for each light receiving element. Therefore, since the AD converter can be realized with a simple configuration, it does not increase the cost,
Simultaneous processing can be performed on a plurality of analog output signals, so that the accuracy of the tracking error signal and the focus error signal can be improved.

This is effective when the AD converter is provided on the same LSI chip as the tracking and focus processing circuits. When the AD converter is provided on the same LSI chip as the tracking and focus processing circuits, if the AD converter is constituted by a successive approximation type AD converter, laser trimming of a resistor or the like is performed to increase the accuracy. However, such processing is practically impossible from the viewpoint of cost and the like. Therefore, the accuracy of the successive approximation type AD converter in the LSI cannot be said to be high.
That is, it can be said that the successive approximation AD converter provided in the signal processing LSI is an AD converter having a large differential error. Therefore, more accurate tracking servo and focus servo could not be performed.

On the other hand, according to the above-mentioned invention, the processing for improving the accuracy as described above is not required, and even if the AD converter is integrated with various other processing circuits, the AD converter can be differentiated. The error is small. Therefore, it is possible to perform more accurate tracking servo and focus servo based on the 1-bit signal output from the AD converter.

Conventionally, an anti-aliasing filter is provided so that aliasing does not occur in the successive approximation type AD converter at the subsequent stage.
Since the converter is configured, such an anti-aliasing filter is not required. As a result, it is possible to overcome the problem inherent in the anti-aliasing filter that phase distortion due to group delay is generated and the servo characteristics are deteriorated without increasing the cost.

The disc reproducing apparatus further includes a decimation filter for receiving a 1-bit signal from the AD converter and outputting a PCM signal having a low sampling frequency, wherein the decimation filter includes a high-frequency noise of the 1-bit signal. And a low-pass filter for removing
PCM conversion means for converting a bit signal into a PCM signal;
It is preferable to include a thinning means for thinning the PCM signal.

In this case, when the one-bit signal output from the AD converter is input to the decimation filter, the high-frequency noise of the one-bit signal is removed by the low-pass filter. The output signal of this low-pass filter is PC
It is converted into a PCM signal by the M conversion means. And
The PCM signal is thinned out by thinning means. This decimation outputs a PCM signal with a low sampling frequency from the decimation filter. The reason for performing this thinning is that when a predetermined phase compensation process is performed on a PCM signal with a high sampling frequency, too much hardware is required. The thinning means reduces such a demand for hard work.

The plurality of PCM signals obtained as described above have no time lag, and a predetermined operation is performed on these PCM signals to obtain a tracking error signal and a focus error signal with high accuracy. Based on this, an effect that the objective lens can be driven and controlled with high accuracy is also exhibited.

In the above-mentioned disc reproducing apparatus, an analog amplifier is provided for each of the light-receiving elements, is constituted by an operational amplifier, and performs current-voltage conversion on an analog output signal of each of the light-receiving elements inputted to its inverting input terminal. A current-voltage conversion circuit for outputting to the converter, wherein the AD converter includes:
An integrator circuit configured by an operational amplifier for integrating the output of the current-voltage conversion circuit input to its inverting input terminal; and an integrator circuit configured by an operational amplifier to output the integrator circuit input to its inverting input terminal. A quantization circuit for performing quantization,
A delay unit that delays the output of the quantization circuit and outputs the one-bit signal as the one-bit signal, and feeds back the one-bit signal to the inverting input terminal of the operational amplifier of the integration circuit. It is preferable that a common reference voltage is input to each non-inverting input terminal.

In this case, when the power supply voltage fluctuates due to a change in the environment, the reference voltage fluctuates accordingly. However, even in such a case, since the common reference voltage is input to the non-inverting input terminals of the three operational amplifiers, no offset occurs between the operational amplifiers. Therefore, a highly accurate tracking error signal and a focus error signal can be generated.

Further, since the AD converter can be constituted by a very simple circuit as described above, the area is smaller than that of a case where the AD converter is constituted by a successive approximation type AD converter. From this, L
The cost of SI manufacturing can be kept low.
This also has the effect of enabling low power consumption.

In the above disk reproducing apparatus, the above AD
The converter is composed of an operational amplifier, performs current-voltage conversion on the analog output signal of each of the light receiving elements input to its inverting input terminal, integrates the converted voltage signal, and an operational amplifier. A quantization circuit configured to quantize the output of the integration circuit input to the inverting input terminal thereof;
A delay device that outputs a bit signal, a delay capacitor, and a switched capacitor that is provided between the inverting input terminal of the operational amplifier of the integration circuit and feeds back the 1-bit signal to the integration circuit; It is preferable that a common reference voltage is input to each non-inverting input terminal of the two operational amplifiers.

In this case, the number of operational amplifiers can be reduced because the operational amplifier of the integrating circuit is shared between the integration function and the current-voltage conversion function. When the power supply voltage changes due to a change in environment, the reference voltage also changes accordingly. However, even in such a case, since the common reference voltage is input to the non-inverting input terminals of the two operational amplifiers, no offset occurs between the operational amplifiers. Therefore, a highly accurate tracking error signal and a focus error signal can be generated.

In addition, the adoption of the switched capacitor makes it possible to cope with variations in LSI manufacturing in relation to the capacitor used for the feedback section of the operational amplifier of the integration circuit. In other words, when compared with the case where feedback is performed via a resistor, a capacitor for a resistor becomes a capacitor for a capacitor, and even if there is a variation in the manufacturing of the capacitor, the two are the same, and it is possible to cancel this variation. The effect is also achieved.

The following is a specific configuration. That is, a disc reproducing apparatus irradiates a disc with a light beam and detects a return light thereof, an information signal photodetector, a tracking photodetector, and a pickup including a focusing photodetector, and the respective photodetectors , An information signal current-voltage converter, a tracking current-voltage converter, and a focus current-voltage converter for current-voltage conversion, and signal processing of the output signal of the information signal current-voltage converter. An information signal processing circuit, a tracking AD converter for inputting output signals of the tracking current-voltage converter and the focus current-voltage converter, and performing AD conversion on the information signals; a focusing AD converter; and the tracking AD conversion The input signal of the focusing device and the AD converter for focusing is input, and the track for moving the objective lens provided in the pickup is moved. Ring control circuit, and a focus control circuit, the information signal processing circuit, AD converter for tracking, AD converter for focus, tracking control circuit, and the focus control circuit in one LS
The AD converter is provided on an I chip, and is configured by a delta-sigma modulation circuit.

Further, another disc reproducing apparatus includes a pickup for converting information recorded on a track of a disc into an optical signal and reading the signal by finely moving an objective lens to focus a laser beam on the track of the disc; A focus control photodetector that is provided in the pickup, receives the reflected light of the laser beam irradiated on the disc, and outputs an original signal serving as a focus control signal; and an output signal of the photodetector. Is input to an inverting input terminal, and an inverting amplifier circuit having a first operational amplifier in which a common reference voltage is input to a non-inverting input terminal; and an output signal of the inverting amplifier circuit is input to an inverting input terminal.
The second common reference voltage is input to the non-inverting input terminal.
An integrating circuit having an operational amplifier; a quantizer for quantizing an output signal of the integrating circuit and outputting a quantized signal; and a delay for delaying the quantized signal and feeding it back to an inverting input terminal of the second operational amplifier. A focus control of an objective lens provided in the pickup based on the quantized signal.

Still another disk reproducing apparatus includes a pickup for converting information recorded on a track of a disk into an optical signal and reading the signal by finely moving an objective lens so that a laser beam follows the track of the disk;
A tracking control photodetector that is provided in the pickup, receives the reflected light of the laser beam irradiated on the disc, and outputs an original signal serving as a tracking control signal, and an output signal of the photodetector Is input to an inverting input terminal, and an inverting amplifier circuit having a first operational amplifier in which a common reference voltage is input to a non-inverting input terminal; and an output signal of the inverting amplifier circuit is input to an inverting input terminal.
A second reference input of the common reference voltage to a non-inverting input terminal;
An integrating circuit having an operational amplifier; a quantizer for quantizing an output signal of the integrating circuit and outputting a quantized signal; and a delay for delaying the quantized signal and feeding it back to an inverting input terminal of the second operational amplifier. And performing tracking control of an objective lens provided in the pickup based on the quantized signal.

Another disc reproducing apparatus irradiates a disc with a light beam and detects reflected light of the disc. The pickup includes a tracking photodetector and a focus photodetector, and the tracking photodetector and the focus photodetector. An integrating circuit having an operational amplifier to which an output signal of the photodetector is input to an inverting input terminal; a quantizer for quantizing an output signal of the integrating circuit to output a quantized signal; and a delay circuit for delaying the quantized signal. A delay unit that feeds back to an inverting input terminal of the operational amplifier, and reference voltage generating means that inputs a common reference voltage to a non-inverting input terminal of the operational amplifier and the quantizer. The tracking control and the focus control of the objective lens provided in the pickup are performed based on.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a disk reproducing apparatus according to the present invention.

FIG. 2 is a circuit diagram showing a specific configuration example of a main part of FIG. 1;

FIG. 3 is a circuit diagram showing another specific configuration example of a main part of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration example of a conventional disk reproducing apparatus.

[Explanation of symbols]

 2 Disc 4 Objective lens 8 Focus drive circuit 9 Tracking drive circuit 12T Tracking light detector 12F Focus light detector 13TE IV converter 13FA IV converter 14TE PDM signal generation circuit (AD converter) 14FA PDM signal generation circuit (AD Converter) 15TE decimation filter 15FA decimation filter 16T phase compensation circuit 16F phase compensation circuit 17T PWM signal generation circuit 17F PWM signal generation circuit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Yoshida 22-22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 5D118 AA14 AA29 BA01 BB02 CA11 CA13 CD02 CD03 CF03 5D119 AA28 BA01 EA02 EA03 KA02 KA17 KA43 5F038 DF12 EZ20

Claims (9)

[Claims] A plurality of light-receiving elements provided for tracking and focusing, respectively, for outputting an analog output signal that changes in accordance with the amount of incident light among the return light from the disk; A plurality of A / D converters, each of which is constituted by a delta-sigma modulation circuit and converts an analog output signal of each of the light receiving elements into a 1-bit signal; and performs a predetermined operation on the output of the A / D converter, respectively. A disc reproducing apparatus comprising: an objective lens drive control means for driving an objective lens based on a tracking error signal and a focus error signal generated by the above method to focus a light beam on a target track of the disc. 2. The disk reproducing apparatus according to claim 1, wherein said AD converter is provided on the same LSI chip as a tracking and focusing processing circuit. 3. A decimation filter for receiving a 1-bit signal from the AD converter and outputting a PCM signal having a low sampling frequency, wherein the decimation filter is a low-pass filter for removing high-frequency noise of the 1-bit signal. A filter, PCM conversion means for converting the 1-bit signal into a PCM signal,
3. The disk reproducing apparatus according to claim 1, further comprising a thinning means for thinning out a CM signal. 4. A current-to-voltage conversion is performed on an analog output signal of each of said light receiving elements, which is provided for each of said light receiving elements, is constituted by an operational amplifier, and is input to an inverting input terminal thereof.
A current-voltage conversion circuit that outputs the current-voltage conversion circuit to the AD converter; the AD converter includes an operational amplifier, and integrates an output of the current-voltage conversion circuit input to an inverting input terminal thereof; A quantization circuit configured by an amplifier and performing quantization on the output of the integration circuit input to the inverting input terminal thereof; and outputting the 1-bit signal by delaying the output of the quantization circuit. A delay unit that feeds back a 1-bit signal to the inverting input terminal of the operational amplifier of the integration circuit, wherein a common reference voltage is input to each non-inverting input terminal of the three operational amplifiers. The disk reproducing apparatus according to claim 1, 2 or 3, wherein 5. The analog-to-digital converter comprises an operational amplifier, performs current-to-voltage conversion on an analog output signal of each of the light receiving elements input to its inverting input terminal, and integrates the converted voltage signal. An integrator circuit, an operational amplifier, and a quantizer circuit for quantizing the output of the integrator circuit input to its inverting input terminal; and a delay of the output of the quantizer circuit as the 1-bit signal A delay device for outputting, a switched capacitor provided between the delay device and the inverting input terminal of the operational amplifier of the integration circuit, for feeding back the 1-bit signal to the integration circuit; 2. A common reference voltage is input to each non-inverting input terminal of an operational amplifier.
4. The disc reproducing device according to 2 or 3. 6. A pickup provided with an information signal photodetector, a tracking photodetector, and a focus photodetector for irradiating a disc with a light beam and detecting the return light thereof, and an output of each of the photodetectors. A current-voltage converter for information signals, a current-voltage converter for tracking, and a current-voltage converter for focusing for inputting a signal and performing current-voltage conversion; and an information signal for signal processing of an output signal of the current-voltage converter for information signals. A processing circuit, a tracking AD converter that inputs an output signal of the tracking current-voltage converter and the focus current-voltage converter and performs AD conversion, and a focusing AD converter; and the tracking AD converter. And focus AD
A tracking control circuit that receives an output signal of the converter and moves an objective lens provided in the pickup; and a focus control circuit. The tracking control circuit and the focus control circuit are provided on one LSI chip,
A disk reproducing apparatus wherein the AD converter is constituted by a delta-sigma modulation circuit. 7. A pickup for converting information recorded on a track of the disk into an optical signal and reading the signal by finely moving an objective lens so as to focus a laser beam on a track of the disk; A focus control photodetector that receives the reflected light of the laser beam irradiated on the disc and outputs an original signal serving as a focus control signal, and an output signal of the photodetector is input to an inverting input terminal. An inverting amplifier circuit having a first operational amplifier to which a common reference voltage is input to a non-inverting input terminal; an output signal of the inverting amplifier circuit being input to an inverting input terminal; An integrator circuit having a second operational amplifier input to the integrator; a quantizer that quantizes an output signal of the integrator circuit and outputs a quantized signal; A delay unit that delays the quantized signal and feeds it back to an inverting input terminal of the second operational amplifier, and performs focus control of an objective lens provided in the pickup based on the quantized signal. apparatus. 8. A pickup for converting information recorded on a track of the disk into an optical signal and reading the signal by finely moving an objective lens so that the laser beam follows the track of the disk; A tracking control photodetector that receives the reflected light irradiated with the laser beam and outputs an original signal serving as a tracking control signal, and an output signal of the photodetector is input to an inverting input terminal, An inverting amplifier circuit having a first operational amplifier having a common reference voltage input to a non-inverting input terminal; an output signal of the inverting amplifier circuit being input to an inverting input terminal; and the common reference voltage being applied to a non-inverting input terminal. An integrating circuit having a second operational amplifier input thereto, and a quantizer for quantizing an output signal of the integrating circuit and outputting a quantized signal And a delay unit that delays the quantized signal and feeds it back to an inverting input terminal of the second operational amplifier, and performs tracking control of an objective lens provided in the pickup based on the quantized signal. Disc playback device. 9. A pickup provided with a tracking photodetector for irradiating a disc with a light beam and detecting reflected light thereof, and a focusing photodetector; and a pickup comprising the tracking photodetector and the focusing photodetector. An integrating circuit having an operational amplifier whose output signal is input to an inverting input terminal; a quantizer that quantizes an output signal of the integrating circuit and outputs a quantized signal; and an operational amplifier that delays the quantized signal. And a reference voltage generating means for inputting a common reference voltage to the non-inverting input terminals of the operational amplifier and the quantizer, and the pickup based on the quantized signal. A disc reproducing apparatus for performing tracking control and focus control of an objective lens provided in the apparatus.