JP2001297468A - Correction circuit for optical signal and optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that neither noise generated in a photodiode, nor noise due to the fluctuation of a constant voltage source for the photodiode can be efficiently removed in a conventional optical pickup. SOLUTION: Every two pairs of photodiode 2a-2h composing a photodetector 2 are provided on one semiconductor substrate 1, respectively. Reflected light from an optical disk is made incident on a photodetecting part consisting of the photodiodes 2a-2d. Reflected light from the optical disk is not made incident on the photodetecting part consisting of the photodiodes 2e-2h. Then, the noise due to the fluctuation of the constant voltage source to which each photodetector is connected or the noise generated in each photodetector are efficiently removed by constituting an optical pickup so as to obtain a signal by differentially amplifying each output of the paired photodiodes with differential amplifiers 6A-6D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a DVD (Digital)
Video Disc / Digital Versatile Disc) and CD (Compac
The present invention relates to an optical pickup used for recording and reproducing data on and from an optical disk such as an optical disk, and more particularly, to an optical signal correction circuit and an optical pickup suitable for reproducing a high-quality signal.

[0002]

2. Description of the Related Art For recording and reproducing data on and from an optical disk such as a DVD and a CD, for example, the "Nikkei Electronics"
1997 4-21 (No. 687) "(1997)
The optical pickup described on pages 135 to 140 of Nikkei BP, Inc. is used. Hereinafter, this optical pickup will be described with reference to FIGS.

[0003] Data taken out of a recording medium by an optical pickup includes RF (Radio Fr.) as an information source.
There are a tracking error signal used for controlling the movement of the optical pickup, a tracking error signal used for controlling the movement of the optical pickup, and a focus error signal. In this case, a phase difference tracking signal method (DPD; Differential Phase Detec
The following describes an example of detection of an RF signal when using (Option).

FIG. 31 is a block diagram showing a configuration example of a conventional optical pickup, FIG. 32 is a block diagram showing a configuration example of a photodetector in FIG. 31, and FIG. 33 is an IV conversion in FIG. FIG. 4 is an explanatory diagram showing an output example of a container.

In FIG. 31, reference numerals 2a to 2d denote photodiodes for converting incident light into electric signals, reference numeral 20n denotes a photodetector for detecting an RF signal, and reference numerals 3a to 3d denote photodetectors for detecting RF signals. Diode 2a
-IV converter for converting the current value from .about.2d to a voltage value (described as "IV" in the figure), 4 is an adder (IV converter 3a to 3D for detection of an RF signal of the DPD method) 5 is a constant voltage source for applying a reverse bias to the photodiodes 2a to 2d.

[0006] As shown in FIG.
The photodetector 20n composed of a to 2d is formed on the semiconductor substrate 1p. FIG. 31 shows a configuration of a portion mounted on an optical pickup in a circuit for reading out a signal of the optical disk detected by each of the photodiodes 2a to 2d.

As shown in FIG. 31, since the photodiodes 2a to 2d have a common cathode, the anodes of the photodiodes 2a to 2d are connected to the inputs of the IV converters 3a to 3d, respectively. , The common cathodes of the photodiodes 2a to 2d are connected to a constant voltage source 5, and the voltage of the constant voltage source 5 is set such that the photodiodes 2a to 2d are reverse-biased.

When the anodes of the photodiodes 2a to 2d are common, the cathodes of the photodiodes 2a to 2d are connected to the inputs of the IV converters 3a to 3d, respectively, contrary to the configuration shown in FIG. , And a common anode of the photodiodes 2 a to 2 d is connected to the constant voltage source 5. Also in this case, the voltage of the constant voltage source 5 is set so that the photodiodes 2a to 2d are reverse biased.

Next, the operation of detecting an RF signal in the optical pickup shown in FIG. 31 will be described. When the light reflected from the optical disk enters the photodiodes 2a to 2d, the magnitude of the current flowing from the cathodes of the photodiodes 2a to 2d to the anode of the photodiodes 2a to 2d changes according to the amount of incident light.

The anodes of the photodiodes 2a to 2d are connected to the inputs of the IV converters 3a to 3d, and the photodiodes 2a to 2d are connected to the IV converters 3a to 3d.
The output voltage changes according to the magnitude of the current flowing through d. Since the output of each of the IV converters 3a to 3d is connected to the input of the adder 4, each of the IV converters 3a to 3d is connected.
The change in the output voltage of 3d is added by the adder 4 and output. Some of the adders 4 are also amplified and output at the same time.

Hereinafter, although not shown, the output of the adder 4 is
After being input to the analog front end of the main board by a wiring such as a flexible cable, and subjected to amplification and waveform shaping, the data is binarized by a comparator into digital data, and decoding and other processing are performed. It should be noted that some optical pickups have only the IV converters 3a to 3d mounted thereon and perform addition on the main substrate side.

In the optical pickup shown in FIG. 31, a high-frequency superimposing circuit or a digital circuit (for example, “Nikkei Electronics 1998 1-2”) for countermeasures against noise due to fluctuations in the constant voltage source 5 and return light of a laser diode used in a light generator.
6 (no. 708) "(1998, published by Nikkei BP), page 126) and noise generated in the photodiodes 2a to 2d (parasitic capacitance and electromagnetic induction). Cannot be removed, and the outputs of the IV converters 3a to 3d are shown in FIG.
Noise is superimposed as shown in FIG.

In FIG. 33A, random noise among noises superimposed on a signal is converted into an IV converter 3a.
Since the time generated at the outputs of the .about.3d is different, the form is averaged by the adder 4 and becomes smaller. However, the pattern noise is added as it is by the adder 4 and output as shown in FIG. I will.

Such noise greatly increases the jitter at which the timing at which the signal changes from “1” to “0” and from “0” to “1” when the signal is binarized on the main board. As a result, there has been a problem that a reading error of a signal recorded on the optical disk is increased.

This is the case when the light reflected from the optical disk is small, when the size of the photodiode serving as a photodetector is reduced, and when the readout circuit is broadened to read out the optical disk at high speed. Is especially problematic. In recent years, CD-ROM and DVD-R
Since the formats of optical disks such as OM and DVD-RAM are diversified, the optical recording and reproducing circuit of the optical pickup also needs a plurality of light generators and a photodetector corresponding to each light generator. It is desired to further reduce the size of the photodiode.

It should be noted that DVDs and CDs are
Conventional techniques for reducing the error rate of data to be reproduced when reproducing data from an optical disc such as, for example, "Nikkei Electronics 1997 1-6"
(No. 679) New Year Special Issue ”(1997, Nikkei B
Techniques such as “bit / byte / bit composite (slice method)” and “Viterbi composite circuit” described on pages 127 to 134 of P. P.) are disclosed. The noise problem cannot be solved.

[0017]

The problems to be solved in the prior art are the noise generated by the photodiode, the noise caused by the fluctuation of the constant voltage source for the photodiode, and the use in the light generator. It is a point that it is not possible to remove noise from a high-frequency superimposing circuit or a digital circuit as a measure against the return light of the laser diode (entering the wiring due to parasitic capacitance or electromagnetic induction).

An object of the present invention is to solve these problems of the prior art, to reduce the reflected light from an optical disk, to reduce the output and power of a laser diode used in a light generator, and to detect light. It is an object of the present invention to provide an optical signal correction circuit and an optical pickup which can reduce the size of a photodiode used in an optical disc and speed up reading of an optical disk.

[0019]

In order to achieve the above object, an optical signal correction circuit and an optical pickup according to the present invention are provided with a photodiode on which light reflected from an optical disk is incident, and a filter for shifting the position or shielding light. For example, a photodetector having a pair of photodiodes on which reflected light from an optical disc is not incident is provided on the same semiconductor substrate or in the same semiconductor package, and the respective outputs of the pair of photodiodes are differentially amplified. A signal is obtained, and from the output of the photodiode where the reflected light from the optical disk is incident, the noise due to the fluctuation of the constant voltage source to which each photodiode is connected, and the high frequency for the return light of the laser diode used for the light generator Eliminate noise entering wiring from superimposing circuits and digital circuits, and noise generated by each photodiode. .

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a first example of the configuration of the optical pickup of the present invention according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of the photodetector in FIG. 1, and FIG. 1 is a block diagram showing a configuration example of an optical system of an optical pickup in FIG.
It is explanatory drawing which shows the example of an output of a -V converter and a differential amplifier.

Hereinafter, an example will be described in which a plurality of light generators are provided to support recording media (optical disks) of different formats such as DVDs and CDs, and an RF signal is detected when the DPD method is used for tracking servo. explain.
Note that description of a photodetector, a circuit, and the like unrelated to the detection of the RF signal is omitted.

In FIG. 3, 101a and 101b are light generators made of laser diodes, 102 is a light detector made of photodiodes, 103a and 103b are beam splitters, 10 is an imaging lens, and 11 is an optical disk.

The laser light emitted from the light generator 101a passes through an optical system (not shown) such as a collimator lens and a polarizing plate, reaches a beam splitter 103a, and is fixed to transmitted light and reflected light by the beam splitter 103a. Divided by percentage. Of these, the transmitted light further reaches the beam splitter 103b, where it is again divided into a transmitted light and a reflected light at a fixed rate. Then, the transmitted light passes through the imaging lens 10.
Thus, an image is formed on the optical disk 11.

The reflected light from the optical disk 11 returns along the same optical path to the beam splitter 103b, and is split by the beam splitter 103b into transmitted light and reflected light at a fixed rate. The reflected light passes through an optical system such as an imaging lens (not shown) and enters the photodetector 102.

The laser light emitted from the light generator 101b passes through an optical system (not shown) such as a collimator lens and a polarizing plate, and reaches the beam splitter 103a, where the laser light is transmitted and reflected by the beam splitter 103a. Divided by the ratio of The reflected light thereafter reaches the optical disc 11 along the same optical path as the laser light from the light generator 101a, and the reflected light from the optical disc 11 passes through an optical system such as an imaging lens (not shown). The light enters the detector 102.

As shown in FIG. 2, a plurality of photodiodes 2a to 2
h, and the tracking servo has D
An RF signal when the PD method is used is detected. here,
The photodetector 102 is divided into two of the photodiodes 2a to 2h, a photodetection unit including the photodiodes 2a to 2d and a photodetection unit including the photodiodes 2e to 2h, and includes the photodiodes 2a to 2d. The light detection unit is arranged at a position where the reflected light from the optical disk 11 in FIG. 3 is incident, and the light detection unit including the photodiodes 2e to 2h is arranged at a position where the reflected light from the optical disk 11 is not incident.

The configuration of the optical pickup in FIG. 1 using the photodetector 2 having such a configuration and the optical system of FIG. 3 will be described. As shown in FIG. 1, each of the photodiodes 2a to 2h in the photodetector 2 forms one pair of the photodiode 2a and the photodiode 2e, and similarly, the photodiodes 2b and 2f and the photodiodes 2c and 2c.
g, and the photodiodes 2d and 2h form a pair.

That is, each of the photodiodes 2a to 2h
Are provided corresponding to the above, the output current values from the photodiodes 2a to 2h of the photodetector 2 are converted into voltage values, and then the IV converters 3a to 3h are provided.
The output from h is photodiodes 2a and 2e, photodiodes 2b and 2f, photodiodes 2c and 2g,
The respective combinations of the photodiodes 2d and 2h are input to the differential amplifiers 6A to 6D,
-6D are differentially amplified.

The anodes of the photodiodes 2a to 2h are connected to the inputs of the IV converters 3a to 3h, and the cathodes of the photodiodes 2a to 2h are common and are connected to the constant voltage source 5. . The voltage of the constant voltage source 5 is set so that the photodiodes 2a to 2h are reverse biased.

If the photodiodes 2a to 2h have a common anode, the cathode of each of the photodiodes 2a to 2h may have an IV
The common anodes of the photodiodes 2 a to 2 h are connected to the constant voltage source 5. Also in this case, the voltage of the constant voltage source 5 is set so that the photodiodes 2a to 2h are reverse biased.

Next, the operation of detecting an RF signal in such a configuration will be described. Since the light emitted from the laser diodes of the light generators 101a and 101b in FIG. 3 and reflected on the optical disk 11 enters the photodiodes 2a to 2d, the magnitude of the current flowing from the cathode to the anode according to the amount of incident light Changes.

On the other hand, the photodiodes 2e to 2h
Does not receive the reflected light from the optical disk 11,
There is no change in the magnitude of the current flowing from the cathode to the anode in response to the reflected light from the optical disk 11, but the light generators 101a and 101b that enter the wiring due to noise due to fluctuations in the constant voltage source 5, parasitic capacitance and electromagnetic induction. The noise from the high-frequency superimposing circuit or digital circuit as a countermeasure for the return light of the laser diode, and the current generated by the noise generated by the photodiodes 2e to 2h themselves,
Flows in the same manner as in a to 2d.

The anodes of the photodiodes 2a to 2h are connected to the inputs of the IV converters 3a to 3h, respectively, and are connected to the photodiodes 2a to 2h in the IV converters 3a to 3h. The output voltage changes according to the magnitude of the flowing current. For example, the IV converters 3a to
In 3d, as shown in FIG. 4A, the output voltage changes in response to the reflected light from the optical disk 11 and noise, and in the IV converters 3e to 3h, as shown in FIG. As described above, the output voltage changes in response to only the noise.

The outputs of the IV converters 3a to 3h are connected to the inputs of the differential amplifiers 6A to 6D. Here, the outputs of the IV converters 3a to 3d are connected to the non-inverting inputs, and the outputs of the IV converters 3e to 3h are connected to the inverting inputs. Converter 3
The reflected light from the optical disk 11 of each output of a to 3d is amplified and output as it is, but the noise is I-
The noise is canceled by the noise of each output of the V converters 3e to 3h. As a result, as shown in FIG. 4C, only the reflected light from the optical disk 11 on which no noise is superimposed is output from the outputs of the differential amplifiers 6A to 6D.

Note that, depending on the configuration of the subsequent stage, the differential amplifier 6
In A to 6D, the outputs of the IV converters 3a to 3d may be connected to inverting inputs, and the outputs of the IV converters 3e to 3h may be connected to non-inverting inputs. In this case, the polarity of the output signal is inverted.

The outputs of the differential amplifiers 6A to 6D shown in FIG. 4C are connected to an adder 4, and the adder 4 adds the outputs of the differential amplifiers 6A to 6D and outputs the sum. In addition, in the detection of the RF signal of the DPD method, all the outputs of the IV converters 6A to 6D are added. The adder 4 may be configured to perform amplification at the same time.

Hereinafter, although not shown, the output of the adder 4 is input to the analog front end of the main board through a wiring such as a flexible cable, and is subjected to amplification and waveform shaping. Then, processing such as decoding is performed.

It should be noted that, on the optical pickup side, up to the IV converters 3a to 3h or up to the differential amplifiers 6A to 6D may be mounted on the circuit, and the addition processing by the adder 4 may be performed on the main board side. good. Further, the differential amplifiers 6A to 6D and the adder 4 may be integrated. Further, in FIG. 2, the photodiodes 2a to 2d and the photodiodes 2e to 2h are formed on the same semiconductor substrate, but they may be formed on separate semiconductor substrates and mounted in the same semiconductor package. good.

Next, with reference to FIGS. 5 to 29, various other examples of the configuration of the photodetector and the optical pickup will be described.

FIG. 5 is a block diagram showing another example of the configuration of the photodetector in FIG. 1. FIG. 6 is an explanatory diagram showing an example of characteristics of a filter used in the photodetector in FIG. In FIG. 5, 1a is a semiconductor substrate, 20 is a semiconductor substrate 1a.
A photodetector for detecting the RF signal formed thereon, 2
Reference numerals a to 2h denote photodiodes constituting the photodetector 2a.

In this example, of the photodiodes 2a to 2h, the photodiodes 2a to 2d are arranged at positions where the reflected light from the optical disk 11 in FIG.
Further, the photodiodes 2e to 2h are
In order to prevent the reflected light from entering, a means for blocking light or a means for blocking light of the wavelength of the laser diode of the light generators 101a and 101b in FIG. 3 (filter 200) Is attached.

As means for blocking the light of the wavelength of the laser diodes of the light generators 101a and 101b, for example, as shown in FIGS.
A filter 200 having such characteristics as to block both light having the wavelengths of the laser diodes a and 101b is used.

The light shielding means, the light generator 101a,
The means (filter 200) for blocking the light of the wavelength of the laser diode 101b is formed, for example, by a semiconductor process or by bonding. When such a light shielding means or filter is used, a photodetector can be configured as shown in FIG.

FIG. 7 is a block diagram showing another example of the configuration of the photodetector in FIG. In this example, the photodetector 20a is set so that the reflected light from the optical disc 11 in FIG.
The arrangement of the photodiodes 2e to 2h provided with a light shielding means and a filter for blocking the light of the wavelength of the light generator at the upper part of FIG. 5 is changed so that the reflected light from the optical disk 11 enters. In the vicinity of the photodiodes 2a to 2d.

That is, the photodiode 2e is placed near the paired photodiode 2a, the photodiode 2f is placed near the paired photodiode 2b, the photodiode 2g is placed near the paired photodiode 2c, and The photodiodes 2h are arranged near the paired photodiodes 2d, respectively, so that the magnitude of noise in each pair is extremely equal. Thereby, the effect of noise removal in the differential amplifiers 6A to 6D in FIG. 1 can be further improved.

This is also true of the IV converters 3a to 3h in FIG. 1. In FIG. 1, the IV converter 3a connected to the output of the photodiode 2a and the output of the photodiode 2e are connected to the output of the photodiode 2a. I / V converter 3e
And a pair of an IV converter 3b connected to the output of the photodiode 2b and an IV converter 3f connected to the output of the photodiode 2f, and a photodiode 2c
A pair of an IV converter 3c connected to the output of the photodiode and an IV converter 3g connected to the output of the photodiode 2g, and an IV converter 3d connected to the output of the photodiode 2d
And a pair of IV converters 3h connected to the output of the photodiode 2h are arranged close to each other, and the magnitudes of noise in the respective pairs are extremely equal to each other. The effect of noise removal can be improved.

Next, another configuration of the optical pickup according to the present invention will be described. FIG. 8 is a block diagram showing a second example of the configuration of the optical pickup of the present invention according to the present invention. The configuration of the optical pickup of this example is the same as the configuration and operation of the optical pickup in FIG. 1 except for the adder 4a. This adder 4a differs from the adder 4 of FIG. 1 in that its output is differential.

As described above, the output from the adder 4a is set to be differential, and the differential signal is transmitted from the optical pickup to the analog front end of the main board. Since noise can be removed when the signal is converted into a single-ended signal by the analog front end of the main board, the noise can be further reduced as compared with the configuration of FIG.

Next, another configuration of the optical system of the optical pickup according to the present invention will be described. FIG. 9 is a block diagram showing another configuration example of the optical system of the optical pickup according to the present invention.

In FIG. 9, reference numeral 101c denotes a plurality of laser diodes, each of which emits light to form an imaging lens 1 which will be described later.
A light generator mounted close to and within the field of view of 0, 1
02a is a photodetector, 103 is a beam splitter, 10a
Is an imaging lens, and 11a is an optical disk.

In such a configuration, the light generator 101
The laser beam emitted from the beam splitter 1 passes through an optical system (not shown) such as a collimator lens and a polarizing plate.
03, and the beam splitter 103 separates the light into transmitted light and reflected light at a fixed rate.

The transmitted light forms an image on the optical disk 11a by the imaging lens 10a. The optical disk 1
The reflected light from 1a returns to the same optical path to the beam splitter 103, where the reflected light is divided into a transmitted light and a reflected light at a fixed ratio, and the reflected light is reflected by an optical system such as an imaging lens (not shown). Through the photodetector 10
2a.

In the optical detector 102a, the optical disk 11a
A photodiode is arranged corresponding to a different incident position for each of the plurality of laser diodes of the light generator 101c of the reflected light from the light source.

FIG. 10 is a block diagram showing a configuration example of the light generator in FIG. In FIG. 10, 1c is a semiconductor substrate, 7A and 7B are laser diodes, and 8 is a mirror. As shown in FIG.
The laser beams from A and 7B are reflected upward by a mirror 8 at right angles and emitted to the outside.

FIG. 10 is for use in the following description and does not limit the configuration in which the present invention is effective. Therefore, the photodiodes for controlling the output of the laser diodes 7A and 7B are not shown.

FIG. 11 is a block diagram showing a first configuration example of the photodetector in FIG. In FIG. 11, 1d
Denotes a semiconductor substrate, 20b denotes a photodetector formed on the semiconductor substrate 1d and detects an RF signal when the DPD method is used for tracking servo, and 2a to 2p denote photodetectors.
b is a photodiode constituting b.

In this example, the photodiode 2a
Photodetector 21 and photodiode 2 comprising a set of
Each of the photodetectors 22 composed of a set of i to 2p is shown in FIG.
Are arranged to receive light emitted from the separate laser diodes 7A and 7B of the light generator 101c shown in FIG. 10 and reflected by the optical disk 11a.

Further, among them, the photodiode 2a
2d and photodiodes 2i to 2l are
The photodiodes 2e to 2h and the photodiodes 2m to 2p are arranged at positions where the reflected light from the optical disk 11a does not enter.

Here, for the following description, the light detecting unit 21 composed of the photodiodes 2a to 2d detects the light emitted from the laser diode 7A and the photodiode 2A.
The light detector 22 composed of i to 21 is a laser diode 7B
It is assumed that the light emitted from the light source is arranged to be incident.

In FIG. 11, the photodiodes 2a to 2a
2p are all formed on the same semiconductor substrate 1d,
Photodetector 2 composed of each set of photodiodes 2a to 2p
It is also possible to form them on separate semiconductor substrates for every 1 and 22 and mount them in the same semiconductor package.

FIG. 12 is a block diagram showing an example of the configuration of an optical pickup using the photodetector of FIG. 11 in the optical system of FIG. In the optical pickup shown in FIG. 12, the photodiodes 2a to 2p commonly reverse-biased by the constant voltage source 5 are, for example, a pair of the photodiode 2a and the photodiode 2e. 2b, 2f, photodiodes 2c, 2
g, photodiodes 2d and 2h, photodiode 2
i, 2m, photodiodes 2j, 2n, photodiodes 2k, 2o, and photodiodes 21 and 2p form a pair.

The output (current value) of the pair of the photodiode 2a and the photodiode 2e is converted into a voltage value by the IV converters 3a and 3e, and
The signal A is differentially amplified, and the noise in the output from the photodiode 2a is removed. Similarly, photodiodes 2b and 2f, photodiodes 2c and 2g, photodiodes 2d and 2h, photodiodes 2i and 2
m, photodiodes 2j and 2n, photodiode 2
k, 2o, and the output of each pair of the photodiodes 21 and 2p, the photodiode 2b, the photodiode 2c, the photodiode 2d, the photodiode 2i, the photodiode 2j, and the photodiode 2
Noise in each of k and the photodiode 21 is removed, and the noise is added by the adders 4A and 4B, respectively.

As described above, the operation of the optical pickup of this embodiment is the same as the operation of the optical pickup in FIG.
In FIG. 12, the light generator 101 shown in FIG.
13C, the outputs of the systems of the number of laser diodes are output.
As shown by, the circuit scale can be reduced by outputting one system.

FIG. 13 is a block diagram showing another example of the configuration of an optical pickup using the photodetector of FIG. 11 in the optical system of FIG. In FIG. 13, the currents flowing through the photodiodes 2a to 2h and the currents flowing through the photodiodes 2i to 2p are combined and combined at the inputs of the IV converters 3a to 3h, respectively. In comparison, the circuit specifications after the IV converters 3a to 3h are halved.

FIG. 14 is a block diagram showing a second configuration example of the photodetector in FIG. Photodetector 20c of this example
In FIG. 11, the photodetector 20b in FIG. 11 controls the presence / absence of reflected light from the optical disk 11a in the respective arrangements of the photodiodes 2a to 2p, whereas the reflected light from the optical disk 11a is Means for blocking the reflected light from the optical disk 11a or means for blocking both the light of the wavelength of the laser diode 7A and the light of the wavelength of the laser diode 7B, above the photodiodes 2e to 2h and 2m to 2p for preventing For example, in FIG.
By attaching filters having the characteristics shown in (a) to (c), the presence / absence of reflected light from the optical disk 11a is controlled and used as a photodetector in the optical pickup shown in FIGS. Can be

FIG. 15 is an explanatory diagram showing a characteristic example of a filter used in the photodetector in FIG. FIG. 15 (a)
By providing filters having the characteristics shown in FIGS. 14C to 14C above the photodiodes 2e to 2h and 2m to 2p in FIG.
The reflected light from the optical disk 11a in FIG.

Further, in FIG. 14, the photodiode 2e is located near the paired photodiode 2a, the photodiode 2f is located near the photodiode 2b, the photodiode 2g is located near the photodiode 2c, 2h to photodiode 2d
Near the photodiode 2m.
The photodiode 2n is arranged near the photodiode 2j, the photodiode 2o is arranged near the photodiode 2k, and the photodiode 2p is arranged near the photodiode 21 in the vicinity of i. The magnitude of the noise is set to be very equal. Thereby, the differential amplifiers 6A to 6H in FIG.
The effect of the noise removal in is increased.

FIG. 16 is a block diagram showing a third example of the configuration of the photodetector in FIG. 9. FIG. 17 is an explanatory diagram showing an example of characteristics of a filter used in the photodetector in FIG.
FIG. 18 is an explanatory diagram illustrating a characteristic example of another filter used for the photodetector in FIG.

The photodetector 20d of the present embodiment transmits light of the wavelength of the laser diode 7A in FIG. 10 but transmits light of the wavelength of the laser diode 7B above the photodiodes 2a to 2d in the photodetector 20b of FIG. For example, a filter having characteristics as shown in FIGS. 17A to 17C is provided and a photodiode 2 is provided.
Means for transmitting light of the wavelength of the laser diode 7B but blocking light of the wavelength of the laser diode 7A, for example, a filter having characteristics as shown in FIGS. It is used as a photodetector in the optical pickup shown in FIGS. 12 and 13.

With such a configuration, the photodetector 20d of the present example has a photodetector 21b and a photodiode 2i to 2d, which are a set of photodiodes 2a to 2h, as compared with the photodetector 20b in FIG. Since the photodetectors 22b composed of 2p pairs can be arranged close to each other, it is possible to reduce the influence of the field of view of the lens.

FIG. 19 is a block diagram showing a fourth configuration example of the photodetector in FIG. Photodetector 20e of this example
Means for blocking the reflected light from the optical disk 11a above each of the photodiodes 2e to 2h and 2m to 2p in the photodetector 20b of FIG. 11 for preventing the reflected light from the optical disk 11a of FIG. Or
Means for blocking both light having the wavelength of the laser diode 7A and light having the wavelength of the laser diode 7B in FIG. 10, for example,
A filter having characteristics as shown in FIGS. 15A to 15C is provided, and light having a wavelength of the laser diode 7A is transmitted above the photodiodes 2a to 2d.
Means for blocking light of the wavelength of the laser diode 7B, for example, a filter having characteristics as shown in FIGS. 17A to 17C are provided, and the wavelength of the laser diode 7B is provided above the photodiodes 2i to 21. A means for transmitting light but blocking light of the wavelength of the laser diode 7A, for example, a filter having characteristics as shown in FIGS. 18 (a) to 18 (c) is provided. Used as a photodetector in a pickup.

With such a configuration, the photodetector 20e of this example has both the advantages of the photodetector 20c in FIG. 14 and the advantages of the photodetector 20d in FIG.

FIG. 20 is a block diagram showing a fifth configuration example of the photodetector in FIG. In FIG. 20, 1h
Is a semiconductor substrate, and 20f is a semiconductor substrate formed on the semiconductor substrate 1h.
Photodetectors for detecting F signals, 2a to 2d, 2i to
Reference numerals 21 and 2q to 2t denote photodiodes constituting the photodetector 2.

In the photodetector 20f of the present embodiment, the photodetector comprising the photodiodes 2a to 2d and the photodiode 2
The light detectors i to 21 are arranged at positions where light emitted from different laser diodes and reflected by the optical disk enters. Then, the photodiodes 2q to 2t
Is located at a position where the light reflected by the optical disk does not enter.

For the following description, the photodiode 2a
2d are arranged so that the light emitted from the laser diode 7A in FIG. 10 is incident, and the photodiodes 2i to 21 are arranged such that the light emitted from the laser diode 7B is incident.

In the example of FIG. 20, the photodiodes 2a to 2d, 2i to 21 and 2q to 2t are all formed on the same semiconductor substrate 1h. It may be formed on the top and mounted in the same semiconductor package.

FIG. 21 is a block diagram showing a configuration example of an optical pickup using the photodetector of FIG. 20 in the optical system of FIG. In FIG. 21, 3a to 3d, 3e to 3
h, 3i to 3l are IV converters, 6A to 6H are differential amplifiers, 4A and 4B are adders, and 5 is an inverse to photodiodes 2a to 2d, 2i to 21 and 2q to 2t of photodetector 20f. It is a constant voltage source for applying a bias.

The operation of the optical pickup of the present embodiment is based on the fact that the I-inputs connected to the respective inverting inputs of the respective differential amplifiers 6A to 6H.
V converters 3e to 3h include differential amplifier 6A and differential amplifier 6
E, differential amplifier 6B and differential amplifier 6F, differential amplifier 6C
The operation is the same as that of the optical pickup of FIG. 1 except that the operation is common to the differential amplifier 6G and the differential amplifier 6D and the differential amplifier 6H.

In the optical pickup of this embodiment, the outputs of the systems of the number of laser diodes of the light generator are output. One signal is output by combining the signals in the preceding stage. The circuit scale can be reduced.

FIG. 22 is a block diagram showing a sixth configuration example of the photodetector in FIG. The photodetector 20g shown in FIG. 22 is different from the photodetector 20f in FIG.
The optical disc 1 is placed above the photodiodes 2q to 2t for preventing the reflected light from the optical disc 11a from entering.
Means for blocking the reflected light from 1 or means for blocking both the light of the wavelength of the laser diode 7A and the light of the wavelength of the laser diode 7B in FIG. 10, for example, FIG.
By attaching a filter having the characteristics shown in (c) to (d) in FIG. 22, the photodiodes 2q to 2t are connected to the photodiodes 2a to 2d or the photodiodes 2i to 2l which have a greater influence of noise (in FIG. Disposed near the photodiodes 2a to 2d),
It is used as a photodetector in the optical pickup of FIG.

In the photodetector 20g of this embodiment, the noises of the photodiodes 2a to 2d and the photodiodes 2q to 2t (in this case), which have a large influence of noise on the signal, are extremely equal to each other. The effect of noise removal by the dynamic amplifier is increased.

FIG. 23 is a block diagram showing a seventh configuration example of the photodetector in FIG. The photodetector 20h in FIG. 23 transmits the light of the wavelength of the laser diode 7A in FIG. 10 but transmits the light of the wavelength of the laser diode 7B above the photodiodes 2a to 2d in the photodetector 20f of FIG. Means for blocking, eg, FIG.
A filter having the characteristics shown in (a) to (c) is attached, and light of the wavelength of the laser diode 7B is transmitted above the photodiodes 2i to 21, but light of the wavelength of the laser diode 7A is blocked. Means, eg, FIG.
A filter having characteristics as shown in FIGS. 8A to 8C is provided, and is used as a photodetector in the optical pickup shown in FIG.

In the photodetector 20h shown in FIG. 23, the photodiodes 2a to 2d and the photodiodes 2i to 2l
Can be arranged close to each other, so that it is less likely to be affected by the field of view of the lens.

FIG. 24 is a block diagram showing an eighth configuration example of the photodetector in FIG. The photodetector 20i in FIG. 24 differs from the photodetector 20g in FIG. 22 in that light having the wavelength of the laser diode 7A is transmitted above the photodiodes 2a to 2d, but light having the wavelength of the laser diode 7B is transmitted. Means for blocking, eg, FIG.
A filter having the characteristics shown in (a) to (c) is attached, and light of the wavelength of the laser diode 7B is transmitted above the photodiodes 2i to 21, but light of the wavelength of the laser diode 7A is blocked. Means, eg, FIG.
A filter having characteristics as shown in FIGS. 8A to 8C is provided, and is used as a photodetector in the optical pickup shown in FIG. The photodetector 20i of FIG. 24 having such a configuration has both the advantages of the photodetector 20g in FIG. 22 and the advantages of the photodetector 20h in FIG.

FIG. 25 is a block diagram showing a ninth configuration example of the photodetector in FIG. In FIG. 25, 1 l
Is a semiconductor substrate, 20j is a photodetector for detecting an RF signal formed on the semiconductor substrate 1l, 2a to 2d, 2i
Reference numerals 21 denote photodiodes constituting the photodetector 20j.

The light detectors composed of the photodiodes 2a to 2d and the light detectors composed of the photodiodes 2i to 2l are emitted from separate laser diodes, respectively.
And the photodiodes 2i to 2l receive the reflected light from the optical disc 11a when the photodiodes 2a to 2d enter the reflected light from the optical disc 11a. The photodiodes not used, and the photodiodes 2a to 2d also serve as photodiodes to which the reflected light from the optical disk 11a does not enter when the photodiodes 2i to 21 enter the reflected light from the optical disk 11a.

For the following description, the photodiode 2a
2d is the light emitted from the laser diode 7A in FIG. 10, and the photodiodes 2i to 2l are
It is assumed that the light emitted from the laser diode 7B is arranged so as to be incident thereon.

In FIG. 25, the photodiode 2a
2d and 2i to 2l are all formed on the same semiconductor substrate 11 but may be formed on a different semiconductor substrate for each set of photodiodes and mounted in the same semiconductor package.

FIG. 26 is a block diagram showing a configuration example of an optical pickup using the optical detector of FIG. 25 in the optical system of FIG. 26, 3a to 3d, 3i to 31 are IV converters, 6A to 6D are differential amplifiers, 4 is an adder,
5 is each photodiode 2a constituting the photodetector 20j.
To 2d and 2i to 2l.

The operation of the optical pickup having the configuration shown in FIG. 26 is such that the photodiodes 2i to 21 also function as photodiodes to which the reflected light from the optical disk does not enter when the photodiodes 2a to 2d enter the reflected light from the optical disk 11a. And the photodiodes 2a to 2
d denotes the photodiodes 2i to 2l and the optical disk 11a
The differential amplifiers 6A to 6D and the subsequent ones are required to be a single system by also functioning as a photodiode to which the reflected light from the optical disk does not enter when the reflected light from the optical disk enters. The polarity of the outputs of the differential amplifiers 6A to 6D is inverted between the case where the reflected light from the optical disk 11a of FIG. 9 is incident and the case where the reflected light from the optical disk 11a is incident on the photodiodes 2i to 21. After step 4, a means for inverting the polarity of the signal is inserted, and the photodiodes 2a through 2d
a when the reflected light from the
The operation is the same as the operation of the optical pickup of FIG. 1 except that the polarity of the signal when the reflected light from the optical disk 11a enters i to 2l needs to be unified.

The means for unifying the polarity of the signal may be either for the analog signal before binarization of the signal on the main board or for the digital signal after binarization.

FIG. 27 is a sectional view of the photodetector of FIG.
FIG. 3 is a block diagram illustrating a configuration example of FIG. The photodetector 20k in FIG. 27 transmits light of the wavelength of the laser diode 7A in FIG. 10 but blocks light of the wavelength of the laser diode 7B above the photodiodes 2a to 2d in the photodetector 20j in FIG. Means, for example, FIG.
(C), a filter having characteristics as shown in FIG. 7 (c) is attached, and light having a wavelength of the laser diode 7B is transmitted above the photodiodes 2i to 21.
Means for blocking light of wavelength A, for example, FIG.
A filter having a characteristic as shown in FIG. 26C is provided, and is used as a photodetector in the optical pickup shown in FIG.

By adopting such a configuration, FIG.
, The photodetectors 20k include the photodiodes 2a-2
d and the photodiodes 2i to 2l can be arranged close to each other, and the influence of the field of view of the lens can be reduced.

In recent years, the size of an optical pickup has been reduced,
For the purpose of cost reduction, etc., the functions of the components are integrated, and the photodetector, the IV converter, and even the adder are integrated on the same semiconductor substrate or the same semiconductor package. Further, in addition to these, a light generator integrated on the same semiconductor substrate or the same semiconductor package is used, and the integration can be similarly performed in each of the optical pickups described with reference to FIGS. This is possible and will be described below with reference to FIGS.

FIG. 28 is a block diagram showing a third example of the configuration according to the present invention of the optical pickup of the present invention. In the optical pickup of this example, the photodetector 201 and the IV
The converter 3, the adder 4, and the differential amplifier 6 are collected on the same semiconductor substrate 1n.

FIG. 29 is a block diagram showing a fourth example of the configuration of the optical pickup of the present invention according to the present invention. In the optical pickup of this embodiment, the laser diodes 7A,
7B, mirror 8, photodiodes 2a-2d, 2i-
A photodetector 20m composed of 2l, an IV converter 3, an adder 4, and a differential amplifier 6 are integrated on the same semiconductor substrate 1o, and a hologram optical element is used as shown in FIG. Thus, the optical path of the light emitted from the laser diodes 7A and 7B and the optical path of the light incident on the photodetector 20m are separated.

The photodetector 20m, the IV converter 3, the differential amplifier 6, and the adder 4 are formed on a semiconductor substrate 1o by a semiconductor process.
7B and the mirror 8 have a package configuration mounted on the semiconductor substrate 1o. The laser diodes 7A, 7A
The photodiode for output control of B is not shown.

FIG. 30 is a block diagram showing a configuration example of the optical system of the optical pickup in FIG. In FIG. 30, by using the hologram optical element 9,
The optical path until the laser beam emitted from the laser diode 7A is input to each photodiode of the photodetector 20m is shown.

That is, the laser light emitted from the laser diode 7A is reflected upward at right angles by the mirror 8 and enters the hologram optical element 9. The laser beam incident on the hologram optical element 9 passes through the hologram optical element 9, passes through an optical system (not shown) such as a collimator lens, a polarizing plate, and a mirror, and forms an image on an optical disk 11a by an imaging lens 10a. , The optical disk 11a
Reflected light returns from the same optical path and enters the hologram optical element 9 again.

The reflected light from the optical disk 11a incident on the hologram optical element 9 is deflected by the hologram optical element 9, and is deflected by the photodiodes 2a-2d of the photodetector 20m.
d. Note that the laser light emitted from the laser diode 7 </ b> B is reflected by the photodiodes 2 i to 2 of the photodetector 2.
The optical path up to input to 1 is described in the same manner.

As described above with reference to FIGS. 1 to 30, in the optical pickup of this embodiment, the photodiode on which the reflected light from the optical disk is incident and the position-shifting or light-blocking filter are provided. A photodetector having a pair of a photodiode on which reflected light from an optical disc is not incident is provided on the same semiconductor substrate or in the same semiconductor package, and a signal is obtained by differentially amplifying each output of the pair of photodiodes. The configuration includes an optical signal correction circuit.

As a result, it is possible to efficiently perform wiring from a high-frequency superimposing circuit or a digital circuit for preventing noise due to fluctuations in the constant voltage source to which each photodetector is connected and return light of a laser diode used in the photogenerator. Noise entering the
Noise and the like generated in each photodetector (photodiode) can be removed.

That is, since the effect of the differential amplification is large,
This is particularly effective when the reflected light from the optical disk is small, when the size of the photodiode serving as a photodetector is reduced, and when the readout circuit is broadened in order to speed up the reading of the optical disk. can get.

The present invention is not limited to the examples described with reference to FIGS. 1 to 30, but can be variously modified without departing from the gist thereof. For example, in the present example, R is calculated when the DPD method is used for the tracking servo.
Although the detection of the F signal is described as an example, the detection of a tracking error signal by subtracting the output from each photodiode and the detection of a focus error signal by adding and subtracting the output from each photodiode are also described. Applicable.

As for the integration, FIGS.
The optical pickup can be integrated not only in the above configuration but also in another configuration.

[0106]

According to the present invention, there is provided a high-frequency superimposing circuit for suppressing noise generated by a photodiode, noise caused by fluctuation of a constant voltage source for a photodiode, and return light of a laser diode used in a light generator. Noise from digital circuits (entering wiring due to parasitic capacitance or electromagnetic induction) can be efficiently removed, and the output of laser diodes used in light generators can be reduced by reducing reflected light from optical disks. -Low power consumption, miniaturization of a photodiode used for a photodetector, and high-speed reading of an optical disk are possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first example of a configuration according to the present invention of an optical pickup of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a photodetector in FIG.

FIG. 3 is a block diagram illustrating a configuration example of an optical system of the optical pickup in FIG. 1;

FIG. 4 is an explanatory diagram illustrating an output example of an IV converter and a differential amplifier in FIG. 1;

FIG. 5 is a block diagram showing another configuration example of the photodetector in FIG. 1;

FIG. 6 is an explanatory diagram showing an example of characteristics of a filter used for the photodetector in FIG.

FIG. 7 is a block diagram showing another configuration example of the photodetector in FIG.

FIG. 8 is a block diagram showing a second example of the configuration of the optical pickup of the present invention according to the present invention.

FIG. 9 is a block diagram showing another configuration example of the optical system of the optical pickup according to the present invention.

FIG. 10 is a block diagram illustrating a configuration example of a light generator in FIG. 9;

FIG. 11 is a block diagram illustrating a first configuration example of the photodetector in FIG. 9;

12 is a block diagram showing a configuration example of an optical pickup using the photodetector of FIG. 11 in the optical system of FIG. 9;

13 is a block diagram showing another configuration example of an optical pickup using the photodetector of FIG. 11 in the optical system of FIG. 9;

FIG. 14 is a block diagram showing a second configuration example of the photodetector in FIG.

15 is an explanatory diagram illustrating an example of characteristics of a filter used for the photodetector in FIG.

FIG. 16 is a block diagram showing a third configuration example of the photodetector in FIG. 9;

17 is an explanatory diagram illustrating a characteristic example of a filter used for the photodetector in FIG.

18 is an explanatory diagram illustrating a characteristic example of another filter used in the photodetector in FIG.

FIG. 19 is a block diagram showing a fourth configuration example of the photodetector in FIG. 9;

20 is a block diagram illustrating a fifth configuration example of the photodetector in FIG.

21 is a block diagram illustrating a configuration example of an optical pickup that uses the photodetector of FIG. 20 in the optical system of FIG. 9;

FIG. 22 is a block diagram illustrating a sixth configuration example of the photodetector in FIG. 9;

FIG. 23 is a block diagram showing a seventh configuration example of the photodetector in FIG. 9;

FIG. 24 is a block diagram showing an eighth configuration example of the photodetector in FIG. 9;

FIG. 25 is a block diagram showing a ninth configuration example of the photodetector in FIG. 9;

26 is a block diagram illustrating a configuration example of an optical pickup using the optical detector of FIG. 25 in the optical system of FIG. 9;

FIG. 27 is a block diagram showing a tenth configuration example of the photodetector in FIG. 9;

FIG. 28 is a block diagram showing a third example of the configuration of the optical pickup of the present invention according to the present invention.

FIG. 29 is a block diagram showing a fourth example of the configuration of the optical pickup of the present invention according to the present invention.

30 is a block diagram illustrating a configuration example of an optical system of the optical pickup in FIG. 29.

FIG. 31 is a block diagram illustrating a configuration example of a conventional optical pickup.

32 is a block diagram illustrating a configuration example of a photodetector in FIG. 31.

FIG. 33 is an explanatory diagram showing an output example of the IV converter in FIG. 31;

[Explanation of symbols]

1, 1a-1p: semiconductor substrate, 2, 20, 20a-20
n: photodetector, 2a to 2t: photodiode, 3, 3
a to 3p: IV converter, 4, 4a, 4A, 4B: adder, 5: constant voltage source, 6A to 6H: differential amplifier, 7A, 7
B: laser diode, 8: mirror, 9: hologram optical element, 10, 10a, 10b: imaging lens, 11, 1
1a, 11b: optical disk, 21, 21a to 21c, 2
2, 22a to 22c: photodetector, 101a to 101c:
Light generator, 102, 102a: photo detector, 103, 10
3a, 103b: beam splitter, 200: filter.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D118 AA14 BA01 BB02 BF02 BF03 CA22 CA23 CC12 CD02 CD03 CD08 CD11 CF01 CF06 5D119 AA12 BA01 DA01 DA05 EA02 EA03 KA02 KA19 KA24 KA43 5F088 AA01 BA03 BB10 EA01 KA01 KA01 KA01 KA01

Claims (11)

[Claims] 1. A light detecting means comprising a pair of a first photodiode receiving reflected light from an optical disk and outputting a corresponding electric signal and a second photodiode receiving no reflected light from the optical disk; Differential amplification means for differentially amplifying electric signals output from the first and second photodiodes of the light detection means, and removing noise from the electric signal output from the light detection means. Optical signal correction circuit. 2. N (N ≧ 1) pairs of a first photodiode receiving reflected light from an optical disk and outputting a corresponding electric signal and a second photodiode receiving no reflected light from the optical disk. And N) for differentially amplifying electric signals output from each of the first and second photodiodes of the light detecting means and removing noise from the electric signal output from the light detecting means. An optical pickup comprising: a differential amplifying means. 3. A pair of M (M ≧ 1) pairs of a first photodiode receiving reflected light from an optical disk and outputting a corresponding electric signal and a second photodiode receiving no reflected light from the optical disk. N (N ≧
M) for differentially amplifying electric signals output from each of the light detecting means and the first and second photodiodes of the light detecting means to remove noise from the electric signal output from the light detecting means. .Times.N differential amplifying means, and a plurality of light generating means for irradiating the optical disc with light having different positions at which the light is reflected by the optical disc and incident on the N light detecting means. An optical pickup, wherein each of the N light detecting means is provided. 4. A pair of M (M ≧ 1) first photodiodes that receive reflected light from an optical disk and output corresponding electric signals and second photodiodes that do not receive reflected light from the optical disk. N (N ≧
2) light detecting means, and means for synthesizing output electric signals from the M-th first photodiode and output electric signals from the second photodiodes of each of the N light detecting means. M differential amplifiers for differentially amplifying the electric signal output from each of the first and second photodiodes of the combined light detecting means and removing noise from the electric signal output from the light detecting means. Amplifying means, and a plurality of light generating means for irradiating the optical disc with lights each having a different position reflected on the optical disc and entering the N light detecting means, wherein the N light beams are provided at different incident positions. An optical pickup provided with each of detection means. 5. N (N.gtoreq.N.gtoreq.N) light beams reflected from the optical disk are received at different incident positions, converted into corresponding electric signals by M (M.gtoreq.2) first photodiodes and output. 2) a first light detecting means, M second light detecting means provided with M second photodiodes to which reflected light from the optical disk is not incident, and N light receiving means
N light generating means for irradiating the optical disc with light received by each of the first light detecting means at each incident position, and M light emitting diodes of the second light detecting means. Output electric signal from the M-th second photodiode, and the above-described N
Means for generating a pair with the output electric signal from the Mth first photodiode of each of the first light detecting means, and M means for each of the N first light detecting means forming a pair. The output electric signal from each of the first first photodiode and the M-th second photodiode of the second light detection means is differentially amplified to generate noise from the output electric signal of the first light detection means. An optical pickup comprising: M × N differential amplifying means for eliminating the noise. 6. M light beams (M ≧ 1), each of which receives reflected light from an optical disc at different incident positions,
N (N ≧ 2) light detecting means for converting and outputting corresponding electric signals by the photodiodes, and N light for irradiating the optical disc with light received at each incident position by the light detecting means. Generating means, and an electric signal output from the M-th photodiode of the light detecting means for receiving light emitted from one of the N light generating means and reflected from the optical disk at a corresponding incident position, and Differentially amplifying an electric signal output from the M-th photodiode of the light detecting means which does not receive the light reflected from the optical disk at a different incident position and receives the light reflected from the optical disk An optical pickup comprising: N differential amplifying means for removing noise from an output electric signal of a detecting means. 7. The optical pickup according to claim 2, wherein the second photodiode is provided at a position where light reflected from the optical disk does not enter. . 8. The optical signal correction circuit according to claim 2, further comprising: a light-shielding means for interrupting the reflected light from said optical disk to said second photodiode. An optical pickup that features. 9. The optical pickup according to claim 2, wherein an output of said plurality of differential amplifying means is used to generate an RF signal by addition, a subtraction is used to generate a tracking error signal, and addition / subtraction is performed. 1. An optical pickup, comprising: an addition / subtraction means for performing at least one of the generation of a focus error signal by the method. 10. The optical pickup according to claim 2, wherein said light detecting means and said differential amplifying means are provided on one semiconductor substrate by a semiconductor process. Optical pickup. 11. The optical pickup according to claim 2, wherein said light detecting means and said differential amplifying means are formed on a single semiconductor substrate by a semiconductor process, and are provided from said optical disk. An optical pickup characterized in that a light generating means for irradiating the optical disk with reflected light is mounted on the semiconductor substrate.