JP2002092902A - Optical recording and reproducing circuit for optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording and reproducing circuit for an optical pickup which deals with optical disks of a plurality of different formats and whose number of components are reduced and circuit configuration is simplified. SOLUTION: A laser beam emitted from a light generator 101 is divided into transmitted light and reflected light at a constant ratio by a beam splitter 103, and the transmitted light is imaged on an optical disk 11 by an imaging lens 10. The reflected light returns to the beam splitter 103 through the same optical path. The reflected light from the optical disk 11 which reaches the beam splitter 103 is divided here into transmitted light and reflected light at a fixed ratio, and the reflected light is made incident on a photodetector 102. In the photodetector 102, photodiodes are disposed for a plurality of laser diodes of the light generator 101 correspondingly to different incident positions of the reflected light from the optical disk 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing circuit of an optical pickup, and more particularly to an optical recording / reproducing circuit of an optical pickup which changes a combination of photodiodes according to a format of an optical disk to be reproduced.

[0002]

2. Description of the Related Art An optical disk has a larger recording capacity than a floppy disk and has higher portability than a hard disk. Therefore, the optical disk has been used in a wide range, and many inventions relating to the optical disk have been devised. A reproduction circuit is one of them.

In an optical recording / reproducing circuit of an optical pickup, the outputs of a photodetector composed of a plurality of photodiodes are individually subjected to IV conversion and amplification, and then the outputs of the photodiodes are calculated in accordance with the signal detection method. And RF
(Radio Frequency) signal, tracking error signal,
Detect a focus error signal. For this reason, the circuit configuration after the photodiode and the IV converter is arranged and configured to satisfy the respective signal detection methods.

[0004]

However, in the optical recording / reproducing circuit of the optical pickup, if the format of the optical disc to be reproduced is different, the configuration of the optical system and the required detection accuracy do not correspond to each other. There was a problem that it could not be read.

As a method that can be considered to solve the above-mentioned problem, it is conceivable to change the signal detection method depending on the configuration of the optical system, required detection accuracy, and the like. Is complicated, and there is a problem that the size of the apparatus and the cost are increased.

Accordingly, the present invention has been made in view of the above problems, and changes the signal detection method depending on the configuration of the optical system, the required detection accuracy, and the like. By changing the combination of photodiodes used for the calculation and the circuit configuration after the IV converter, the number of components and the circuit configuration are simplified,
An object of the present invention is to provide an optical recording / reproducing circuit of an optical pickup corresponding to optical disks of a plurality of different formats.

[0007]

In order to achieve the above object, according to the present invention, there is provided a light detecting device comprising a plurality of light generators for handling a plurality of optical disks of different formats and a plurality of photodiodes. A plurality of IV converters for converting a current generated by the photodetector into a voltage;
A photodetector, comprising: an amplifier for amplifying the output of the -V converter; and a plurality of adder / subtracters for adding, subtracting, and adding / subtracting the output of the amplifier to obtain an RF signal, a tracking error signal, and a focus error signal. The positions where the reflected light from the optical disk is incident on the optical disk differ among a plurality of light generators, and a set of photodetectors is arranged for each incident position of the reflected light from the optical disk, and the output of each photodiode is differentially detected. For at least one of an amplified RF signal, a tracking error signal, and a focus error signal, a combination of a photodiode used for signal calculation according to a format of an optical disc to be reproduced and a circuit configuration after an IV converter are described. It is characterized by changing.

Therefore, the invention according to the first aspect of the present invention changes the combination of photodiodes used for signal calculation and the circuit configuration after the IV converter in accordance with the format of the optical disk to be reproduced, thereby reducing the number of parts and the number of components. It is possible to support optical disks of a plurality of different formats with a simplified circuit configuration.

According to a second aspect of the present invention, in the optical recording / reproducing circuit of the optical pickup according to the first aspect,
In accordance with the change of the combination of photodiodes according to the format of the optical disc to be reproduced,
/ V conversion efficiency is changed.

Therefore, according to the second aspect of the present invention, the I / V converter I / V converter operates in conjunction with the change of the combination of the photodiodes according to the format of the optical disk to be reproduced.
By changing the V conversion efficiency, it is possible to eliminate a difference in dynamic range of a signal caused by a change in sensitivity due to a wavelength of incident light of a photodiode and a change in reflectance of an optical disk for each format.

According to a third aspect of the present invention, in the optical recording / reproducing circuit of the optical pickup according to the first aspect,
The amplification factor of the amplifier is changed in conjunction with the change of the combination of the photodiodes according to the format of the optical disc to be reproduced.

Therefore, according to the third aspect of the present invention, the wavelength of the incident light of the photodiode is changed by changing the amplification factor of the amplifier in conjunction with the change of the combination of the photodiodes according to the format of the optical disk to be reproduced. It is possible to eliminate a difference in dynamic range of a signal generated due to a change in sensitivity due to the above or a change in reflectivity of an optical disk for each format.

According to a fourth aspect of the present invention, in the optical recording / reproducing circuit of the optical pickup according to any one of the first to third aspects, at least one of a photodetector and an IV converter or later is provided. It is characterized in that one or more functions are formed on the same semiconductor substrate or in the same semiconductor package.

Therefore, according to the invention of claim 4, at least one or more functions after the photodetector and the IV converter are formed on the same semiconductor substrate or in the same semiconductor package, so that the circuit The mounting area can be reduced.

According to a fifth aspect of the present invention, in the optical recording / reproducing circuit of the optical pickup according to any one of the first to fourth aspects, at least one light generator is integrated in the same package. It is characterized by the following.

Therefore, according to the fifth aspect of the present invention, it is possible to reduce the circuit mounting area by integrating at least one light generator in the same package.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording detection circuit of an optical pickup according to an embodiment of the present invention uses a push-pull method and a DPD (Differential Phase) method for detecting a tracking error signal.
Detection) method will be described.

FIG. 1 is a diagram showing a configuration of an optical system in an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention. Hereinafter, the function of each device constituting the optical system according to the present embodiment will be described with reference to FIG.

The optical system in the optical recording / reproducing circuit of the optical pickup according to the present embodiment includes a light generator 101, a photodetector 102, a beam splitter 103, an imaging lens 10, and an optical disk 11.

The imaging lens 10 is a lens that forms an image of light at a predetermined position. The optical disk 11 is a recording medium that uses laser light for reading and writing data, and specifically includes a CD and a DVD.

The light generator 101 mounts a plurality of laser diodes close to each other so that each emitted light enters the field of view of the imaging lens 10. 102 is a photodetector, 103 is a beam splitter.

The laser beam emitted from the light generator 101 in FIG. 1 reaches the beam splitter 103 through an optical system, such as a collimator lens and a polarizing plate, which are omitted here.
The laser light emitted from the light generator 101 is divided by the beam splitter 103 into transmitted light and reflected light at a certain ratio. The transmitted light forms an image on the optical disk 11 by the imaging lens 10.

The reflected light returns to the same optical path up to the beam splitter 103. In the reflected light from the optical disk 11 that has reached the beam splitter 103, the transmitted light and the reflected light are divided at a certain ratio. The reflected light is the photodetector 1
02. In the photodetector 102, photodiodes are arranged corresponding to different incident positions for each of the plurality of laser diodes of the light generator 101 of the reflected light from the optical disk 11.

FIG. 2 is a diagram showing a configuration of a light generator 101 included in an optical recording / reproducing circuit of an optical pickup according to one embodiment of the present invention. (A) is a top view of the light generator 101, and (A) is a cross-sectional view taken along aa 'plane in the top view.

The light generator 101 has at least the semiconductor substrate 1 and laser diodes 9A and 9B. FIG. 2 is for the following description and does not limit the configuration of the effective light generator in the present invention. The photodiodes and electrodes for controlling the output of the laser diodes 9A and 9B are not shown. .

FIG. 3 is a diagram showing a configuration including the photodetector 2 in the optical recording / reproducing circuit of the optical pickup according to one embodiment of the present invention. The photodetector 2 is formed on the semiconductor substrate 1 and has photodiodes 21A to 21D and 22A to 22D.
Having.

Here, the photodiodes 21A to 21D
Are arranged so as to receive the light emitted from the laser diode 9A and reflected by the optical disk and not to receive the light emitted from the laser diode 9B and reflected by the optical disk. The set of photodiodes 22A to 22D is arranged so as to receive the light emitted from the laser diode 9B and reflected by the optical disk and not to receive the light emitted from the laser diode 9A and reflected by the optical disk.

FIG. 3 is also for the following description, and does not limit the arrangement of photodiodes effective in the present invention. Also, the photodiodes 21A to 21D, 22
Each of the sets A to 22D is arranged so as not to receive the light emitted from the laser diode 9B and reflected by the optical disk and the light emitted from the laser diode 9A and reflected by the optical disk, but to prevent the light from being incident thereon. A means (for example, a filter) for blocking light having the wavelength of the desired laser diodes 9A and 9B may be provided.

FIG. 4 is a diagram showing a first configuration of an optical recording / reproducing circuit of an optical pickup using a light generator 101 and a photodetector 2 in an optical system according to an embodiment of the present invention.
The optical recording / reproducing circuit includes at least adders 4A and 4B, differential amplifiers 6A to 6D and 61, a switch 7, photodiodes 21A to 21D and 22A to 22D, and IV converters 31A to 31D and 32A to 32D. 32D, and the switch 7 includes input terminals IN1, IN2 and an output terminal OUT.
1, OUT2.

In the configuration shown in FIG.
1A to 21D receive the light reflected from the optical disk 11 after being emitted from the laser diode 9A, and do not receive the light reflected from the optical disk 11 after being emitted from the laser diode 9B.

The photodiodes 22A to 22D receive the light emitted from the laser diode 9B and reflected on the optical disk 11, and do not receive the light emitted from the laser diode 9A and reflected on the optical disk 11.

The photodiodes 31A to 31D and the differential amplifiers 6A to 6D differentially amplify the output of the photodiode on which the reflected light from the optical disk 11 is incident and the output of the photodiode on which the reflected light from the optical disk 11 is not incident. The noise contained in the output of the photodiode on which the light reflected from the optical disk 11 is incident is reduced.

The differential amplifier 61 generates a tracking error signal, and the low voltage source 5
A reverse bias is applied to 21D and 22A to 22D.

The switch 7 outputs the output of the differential amplifier 61 which performs addition by the adders 4A and 4B to the photodiodes 21A to 21A.
Switching is performed between the case where the tracking error signal is created from the output of 21D and the case where the tracking error signal is created from the outputs of the photodiodes 22A to 22D.

FIG. 6 is a diagram showing a connection pattern of the switch 7 of the optical recording / reproducing circuit of the optical pickup according to one embodiment of the present invention. Hereinafter, the generation of the tracking error signal by the switch 7 will be described with reference to FIGS.

When a tracking error signal is generated from the outputs of the photodiodes 21A to 21D as shown in FIG. 6A, the input terminal IN1 is connected to the output terminal OUT1, and the input terminal IN2 is connected to the output terminal OUT2. You.

When a tracking error signal is created from the outputs of the photodiodes 22A to 22D as shown in FIG. 6A, the input terminal IN2 is connected to the output terminal OUT.
1. The input terminal IN1 is connected to the output terminal OUT2.

When the tracking error signal is generated by the photodiodes 21A to 21D, the push-pull method is used. When the tracking error signal is received by the photodiodes 22A to 22D, the DPD method is used.

In FIG. 4, photodiodes 21A to 21D,
The anodes of 22A to 22D are respectively connected to the IV converter 31.
The cathodes of the photodiodes 21A to 21D and 22A to 22D are connected to the inputs of A to 31D and 32A to 32D. Here, the voltage of the constant voltage source 5 is set so that the photodiodes 21A to 21D and 22A to 22D are reverse biased.

The outputs of the IV converters 31A to 31D are supplied to the non-inverting inputs of the differential amplifiers 6A to 6D and the IV converter 32A.
Outputs of .about.32D are connected to inverting inputs of differential amplifiers 6A to 6D.

The output of the differential amplifier 6A is
A, and the output of the differential amplifier 6D is
Connected to B input. The output of the differential amplifier 6B is connected to one input terminal IN1 of the switch 7, the output of the differential amplifier 6C is connected to the other input terminal IN2 of the switch 7,
The output terminal OUT1 of the switch 7 is connected to the input of the adder 4A.
The output terminal OUT2 is connected to the input of the adder 4B. Further, the output of the adder 4A is connected to the non-inverting input of the differential amplifier 61, and the output of the adder 4B is connected to the inverting input of the differential amplifier 61.

Next, the operation of detecting the tracking error signal in the circuit of FIG. 4 will be described. When a signal recorded on an optical disk corresponding to the laser diode 9A is reproduced, light emitted from the laser diode 9A of the light generator 101 and reflected by the optical disk enters the photodiodes 21A to 21D. The magnitude of the current flowing from the cathode to the anode changes accordingly.

On the other hand, since the reflected light from the optical disk does not enter the photodiodes 22A to 22D, the magnitude of the current flowing from the cathode to the anode does not change in response to the reflected light from the optical disk. , Noise from a high-frequency superimposing circuit or a digital circuit as a measure against return light of the laser diode of the light generator 101 that enters the wiring due to parasitic capacitance or electromagnetic induction, and current due to noise generated by the photodiode itself is the photodiode 21A. Flows in the same way as ~ 21D.

FIG. 5 is a diagram showing an output voltage from an IV converter of an optical recording / reproducing circuit of an optical pickup according to one embodiment of the present invention. Hereinafter, changes in the output voltage by the IV converter according to the present embodiment will be described with reference to FIG.

Photodiodes 21A to 21D, 22A
To 22D change in the IV converters 31A to 31A
1D and 32A to 32D perform IV conversion, and the IV converters 31A to 31D correspond to changes in the magnitudes of currents flowing through the photodiodes 21A to 21D and 22A to 22D.
D, the output voltages of 32A to 32D change.

In the IV converters 31A to 31D, the output voltage changes in accordance with the reflected light from the optical disk 11 and the noise (FIG. 5A), and the IV converters 32A to 32D respond to the noise. As a result, the output voltage changes (FIG. 5A).

Also, the IV converters 31A to 31D, 32
Outputs of A to 32D are connected to inputs of differential amplifiers 6A to 6D. In the differential amplifiers 6A to 6D, an IV converter 31A is used.
To 31D and the outputs of the IV converters 32A to 32D, respectively.
The reflected light from the optical disc 11 of each output of A to 31D is amplified and output as it is, but the noise is I-31D.
Since the output noise of each of the V converters 32A to 32D is offset, only the reflected light from the optical disk 11 on which no noise is superimposed is output at the output (FIG. 5).
(C)).

Here, the photodiodes 21A to 21D
In the case where light is received by the method, a tracking error signal is generated by a push-pull method. In the push-pull method, a tracking error signal is generated from the output difference between the photodiodes divided into two right and left along the track direction. In this case, the photodiodes 21A and 21B and the photodiode 21 are used.
The output difference between C and 21D may be obtained.

When generating a tracking error signal from the outputs of the photodiodes 21A to 21D, the switch 72 is used.
Since the input terminal IN1 is connected to the output terminal OUT1 and the input terminal IN2 is connected to the output terminal OUT2, the output of the differential amplifier 6B is connected to the input of the adder 4A and the differential amplifier 6C
Is connected to the input of the adder 4B.

Therefore, in the adder 4A, the differential amplifier 6A,
6B, and the adder 4B adds the differential amplifier 6C,
6D output, and then the differential amplifier 61
Then, the output of the adder 4A and the output of the adder 4B are differentially amplified.

Here, when the output of the differential amplifier 6A is traced back, the output of the photodiode 21A and the differential amplifier 6B
Is the output of the photodiode 21B,
Since the output of the differential amplifier 6C is the output of the photodiode 21C when following the element, and the output of the differential amplifier 6D is the output of the photodiode 21D when the element is followed, the output of the adder 4A is the sum of the photodiodes 21A and 21B. , Adder 4
The output of B is the sum of photodiodes 21C and 21D, and the output of differential amplifier 61 is photodiode 21A,
The output difference between 21B and photodiodes 21C and 21D is obtained, and a tracking error signal is obtained.

On the other hand, when reproducing a signal recorded on the optical disk 11 corresponding to the laser diode 9B,
Since the light emitted from the laser diode 9B of the light generator 101 and reflected by the optical disk 11 enters the photodiodes 22A to 22D, the magnitude of the current flowing from the cathode to the anode changes according to the amount of incident light.

On the other hand, since the reflected light from the optical disk 11 does not enter the photodiodes 21A to 21D, the magnitude of the current flowing from the cathode to the anode does not change in response to the reflected light from the optical disk 11, but the constant voltage source 5 Noise from the high frequency superposition circuit or digital circuit of the laser diode of the light generator 101 as a measure against the return light of the laser diode entering the wiring due to parasitic capacitance or electromagnetic induction, and
The current due to the noise generated by the photodiode itself flows similarly to the photodiodes 22A to 22D.

Then, the photodiodes 22A to 22A
D, 21A to 21D are subjected to IV conversion by IV converters 32A to 32D and 31A to 31D, and photodiodes 22A to 22D and 21A to 21D.
Converter 3 corresponding to the change in the magnitude of the current flowing through
The output voltages of 2A to 32D and 31A to 31D change.

In the IV converters 32A to 32D, the output voltage changes according to the reflected light from the optical disk 11 and the noise (FIG. 5A), and the IV converters 31A to 31D correspond to the noise. As a result, the output voltage changes (FIG. 5A).

Then, the IV converters 32A to 32D, 3
Outputs of 1A to 31D are connected to inputs of differential amplifiers 6A to 6D. In the differential amplifiers 6A to 6D, the IV converter 32
Since differential amplification is performed between the outputs of A to 32D and the outputs of the IV converters 31A to 31D, respectively, the IV converter 3
The reflected light from the optical disk 11 of each output of 2A to 32D is amplified and output as it is.

On the other hand, noise is reduced by the IV converters 31A to 31A.
Since the noise of each output of D is canceled out, only the reflected light from the optical disk 11 on which no noise is superimposed is output to the outputs of the differential amplifiers 6A to 6D (FIG. 5D: I).
-V converters 32A-32D output differential amplifiers 6A-6
The polarity of the output is inverted because it is connected to the inverting input of D).

Here, the photodiodes 22A to 22D
In the case where light is received by the tracking error signal, a tracking error signal is generated by the DPD method. In the DPD method, a tracking error signal is generated from a diagonal difference signal of a photodiode divided into four (one of which is along the track direction). In this case, the output difference between the photodiodes 22A and 22C and the photodiodes 22B and 22D is generated. Should be obtained.

When generating a tracking error signal from the outputs of the photodiodes 22A to 22D, the switch 72 is used.
Since the input terminal IN2 is connected to the output terminal OUT1 and the input terminal IN1 is connected to the output terminal OUT2, the output of the differential amplifier 6B is connected to the input of the adder 4B and the differential amplifier 6C
Is connected to the input of the adder 4A.

Therefore, in the adder 4A, the differential amplifier 6A,
6C, and the adder 4B adds the differential amplifier 6B,
6D output, and then the differential amplifier 61
Differentially amplifies the output of the adder 4A and the output of the adder 4B.

Here, the output of the differential amplifier 6A traces back to the output of the photodiode 22A, the output of the differential amplifier 6C traces the trace of the output of the photodiode 22C, and the output of the differential amplifier 6B traces the trace. And photodiode 2
Since the output of the differential amplifier 2B and the output of the differential amplifier 6D follow the output of the photodiode 22D, the output of the adder 4A is the sum of the photodiodes 22A and 22C and the adder 4B
Is the sum of the photodiodes 22B and 22D,
The outputs of the differential amplifier 61 are the photodiodes 22A and 22A.
An output difference between C and the photodiodes 22B and 22D is obtained, and a tracking error signal is obtained.

Although not shown hereafter, the output of the differential amplifier 61 is input to the analog front end of the main board through wiring such as a flexible cable, and is amplified and received by the photodiodes 21A to 21D.
Waveform shaping including unification of polarities in the case of receiving light at A to 22D is performed, and then binarized into digital data to perform tracking servo processing.

Here, in FIG.
Although the cathodes of A to 21D and 22A to 22D are commonly used, the anodes may be commonly used. In this case, the photodiodes 21A to 21D are opposite to those of FIG.
The cathodes of 21D, 22A to 22D are connected to the inputs of IV converters 31A to 31D, 32A to 32D, respectively, and the photodiodes 21A to 21D, 22A to 22D
Are connected to a constant voltage source 5. Also in this case, the voltage of the constant voltage source 5 is equal to the photodiodes 21A to 21D,
2A to 22D are reverse biased.

The polarity of the inputs of the differential amplifiers 6A to 6D and 61 is not limited to the configuration shown in FIG. Further, in some cases, the adder 4
The amplification may be performed simultaneously with the addition in A and 4B.

FIG. 10 is a diagram showing a second configuration of an optical recording / reproducing circuit of an optical pickup using a light generator 101 and a photodetector 2 in an optical system according to an embodiment of the present invention. The configuration shown in FIG. 7 differs from the first configuration shown in FIG. 4 in that the output of the photodiode is IV-converted and the signal used for the operation is switched after differential amplification, but before the IV conversion. In this case, the signal is switched.

In this embodiment, the optical recording / reproducing circuit of the optical pickup comprises at least adders 4A and 4B, differential amplifiers 6A to 6D and 61, switches 71 and 72, and photodiodes 21A to 21D and 22A to 22D. And I
-V converters 31A to 31D and 32A to 32D, and switches 71 and 72 are connected to input terminals IN1 and IN1, respectively.
IN2 and output terminals OUT1 and OUT2.

In FIG. 7, the photodiodes 21A to 21D
Is the optical disk 11 emitted from the laser diode 9A.
The light reflected by the optical disk 11 is received, and the light emitted from the laser diode 9B and reflected by the optical disk 11 is not received.

The photodiodes 22A to 22D receive light emitted from the laser diode 9B and reflected on the optical disk, and do not receive light emitted from the laser diode 9A and reflected on the optical disk.

The differential amplifiers 6A to 6D differentially amplify the output of the photodiode on which the reflected light from the optical disk enters and the output of the photodiode on which the reflected light from the optical disk does not enter, and the reflected light from the optical disk enters. The noise contained in the output of the photodiode is reduced.

The differential amplifier 61 generates a tracking error signal, and the low voltage source 5
A reverse bias is applied to 21D and 22A to 22D.

The switches 71 and 72 are connected to an IV converter when generating a tracking error signal from the outputs of the photodiodes 21A to 21D and when generating a tracking error signal from the outputs of the photodiodes 22A to 22D. Change the output of the photodiode.

The connection of the signal lines of the switches 71 and 72 is shown in FIG.
When the tracking error signal is created from the outputs of the photodiodes 21A to 21D as shown in FIG.
Are connected to the output terminal OUT1, and the input terminal IN2 is connected to the output terminal OUT2.
To create a tracking error signal from the output of D, the input terminal IN1 is connected to the output terminal OUT2, and the input terminal IN1 is connected to the output terminal OUT2.

The tracking error signal is generated by the push-pull method when light is received by the photodiodes 21A to 21D as in the first configuration.
When light is received at 2A to 22D, the DPD method is used.

In FIG. 7, the photodiodes 21A to 21D,
The common cathodes of 22A to 22D are connected to the constant voltage source 5. The anodes of the photodiodes 21A and 21D are I
The anodes of the photodiodes 22A and 22D are connected to the inputs of the -V converters 31A and 31D.
A, 32D connected to inputs.

The anodes of the photodiodes 21B and 21C are connected to the input terminal IN1 and the input terminal IN2 of the switch 71, respectively.
The anodes of the photodiodes 22B and 22C are connected to the input terminal IN1 and the input terminal IN2 of the switch 72. Further, the output terminal OUT1 and the output terminal OUT2 of the switch 71 are connected to the IV converters 31B and 31C,
Output terminal OUT1 and output terminal OUT2 of switch 72 are connected to IV converters 32B and 32C.

Here, the voltage of the constant voltage source 5 is set so that the photodiodes 21A to 21D and 22A to 22D are reverse biased. The outputs of the IV converters 31A to 31D are connected to the non-inverting inputs of the differential amplifiers 6A to 6D, and the outputs of the IV converters 32A to 32D are connected to the non-inverting inputs of the differential amplifiers 6A to 6D. .

The outputs of the differential amplifiers 6A and 6B are connected to an adder 4A.
And the outputs of the differential amplifiers 6C and 6D are connected to the input of the adder 4B. Further, the output of the adder 4A is connected to the non-inverting input of the differential amplifier 61, and the output of the adder 4B is connected to the inverting input of the differential amplifier 61.

Next, the operation of detecting the tracking error signal in the circuit of FIG. 7 will be described. When a signal recorded on the optical disk 11 corresponding to the laser diode 9A is reproduced, light emitted from the laser diode 9A of the light generator 101 and reflected by the optical disk 11 enters the photodiodes 21A to 21D. The magnitude of the current flowing from the cathode to the anode changes according to the amount of light.

On the other hand, since the reflected light from the optical disk 11 does not enter the photodiodes 22A to 22D, the magnitude of the current flowing from the cathode to the anode does not change in accordance with the reflected light from the optical disk 11, but the constant voltage source 5 Noise from the high frequency superposition circuit or digital circuit of the laser diode of the light generator 101 as a measure against the return light of the laser diode entering the wiring due to parasitic capacitance or electromagnetic induction, and
The current due to the noise generated by the photodiode itself flows similarly to the photodiodes 21A to 21D.

The photodiodes 21A, 22A,
The change in the current flowing through 21D and 22D is determined by the IV converter 31.
IV conversion is performed by A, 32A, 31D, and 32D, and the change in the current flowing through the photodiodes 21B and 22B is input to the input terminals IN1 of the switches 71 and 72, and
Is output from the output terminal OUT1 and the IV converters 31B and 32B perform IV conversion.

Further, the photodiodes 21C and 22C
Changes in the current flowing through the input terminals I and I of the switches 71 and 72
The voltage is input to N2, output from the output terminal OUT2 as shown in FIG. 6, is subjected to IV conversion by the IV converters 31C and 32C, and corresponds to the change in the magnitude of the current flowing through the respective connected photodiodes. And the IV converters 31A to 31
D, the output voltages of 32A to 32D change.

In the IV converters 31A to 31D, the output voltage changes according to the reflected light from the optical disk 11 and the noise (FIG. 5A), and the IV converters 32A to 32D correspond to the noise. As a result, the output voltage changes (FIG. 5A).

The IV converters 31A to 31D, 32
Outputs of A to 32D are connected to inputs of differential amplifiers 6A to 6D. In the differential amplifiers 6A to 6D, an IV converter 31A is used.
To 31D and the outputs of the IV converters 32A to 32D, differential amplification is performed.
The reflected light from the optical disk 11 of each output of D is amplified and output as it is, but the noise is offset by the noise of each output of the IV converters 32A to 32D. Optical disc 11 without superimposition
Only the reflected light from is output (FIG. 5 (c)).

Here, the photodiodes 21A to 21D
, The tracking error signal is generated by the push-pull method. In the push-pull method, a tracking error signal is generated from the output difference between the photodiodes divided into two right and left along the track direction. In this case, the photodiodes 21A and 21B and the photodiode 21 are used.
The output difference between C and 21D may be obtained.

When a tracking error signal is created from the outputs of the photodiodes 21A to 21D, the output of the differential amplifier 6A follows the output of the photodiode 21A, and the output of the differential amplifier 6B follows the original. The output of the differential amplifier 21C and the output of the differential amplifier 6C are the output of the photodiode 21C when traced back, and the output of the differential amplifier 6D is the output of the photodiode 21D when traced back.

For this reason, in the adder 4A for adding the output of the differential amplifier 6A and the output of the differential amplifier 6B, the output of the photodiode 21A and the output of the photodiode 21B are added, and the output of the adder 4A is differentiated from the output of the differential amplifier 6C. In the adder 4B for adding the output of the amplifier 6D, the output of the photodiode 21C and the output of the photodiode 21D are added. Next, in the differential amplifier 61, the output of the adder 4A and the output of the adder 4B are differentiated. Since the signal is amplified, the output of the differential amplifier 61 becomes the output difference between the photodiodes 21A and 21B and the photodiodes 21C and 21D, and a tracking error signal is obtained.

On the other hand, when reproducing a signal recorded on the optical disk 11 corresponding to the laser diode 9B,
Since the light emitted from the laser diode 9B of the light generator 101 and reflected by the optical disk 11 enters the photodiodes 22A to 22D, the magnitude of the current flowing from the cathode to the anode changes according to the amount of incident light.

On the other hand, since the reflected light from the optical disk 11 does not enter the photodiodes 21A to 21D, the magnitude of the current flowing from the cathode to the anode does not change in response to the reflected light from the optical disk 11, but the constant voltage source 5 Noise from the high frequency superposition circuit or digital circuit of the laser diode of the light generator 101 as a measure against the return light of the laser diode entering the wiring due to parasitic capacitance or electromagnetic induction, and
The current due to the noise generated by the photodiode itself flows similarly to the photodiodes 22A to 22D.

The photodiodes 21A, 22A,
The change in the current flowing through 21D and 22D is determined by the IV converter 31.
A, 32A, 31D, and 32D perform IV conversion, and a change in current flowing through the photodiodes 21B and 22B is input to the input terminals IN1 of the switches 71 and 72 and output to the output terminal OUT2 as shown in FIG. Output from I-
IV conversion is performed by V converters 31C and 32C.

Further, the photodiodes 21C and 22C
Changes in the current flowing through the input terminals I and I of the switches 71 and 72
The voltage is input to N2, output from the output terminal OUT1 as shown in FIG. 6, is subjected to IV conversion by the IV converters 31B and 32B, and corresponds to the change in the magnitude of the current flowing through the respective connected photodiodes. And the IV converters 31A to 31
D, the output voltages of 32A to 32D change.

In the IV converters 32A to 32D, the output voltage changes in response to the reflected light from the optical disk 11 and the noise (FIG. 5A), and the IV converters 31A to 31D respond to the noise. As a result, the output voltage changes (FIG. 5A).

The IV converters 32A to 32D, 31
Outputs of A to 31D are connected to inputs of differential amplifiers 6A to 6D. In the differential amplifiers 6A to 6D, the IV converter 32A is used.
32A to 32D and the outputs of the IV converters 31A to 31D, differential amplification is performed.
The reflected light from the optical disk 11 of each output of D is amplified and output as it is.

On the other hand, noise is generated by the IV converters 31A to 31A-3.
Since the noise of each output of 1D is canceled out, only the reflected light from the optical disk 11 on which no noise is superimposed is output to the outputs of the differential amplifiers 6A to 6D (FIG. 5).
(D)). Further, since the outputs of the IV converters 32A to 32D are connected to the inverting inputs of the differential amplifiers 6A to 6D, the polarities of the outputs are inverted.

Here, the photodiodes 22A to 22D
In the case where light is received by the tracking error signal, a tracking error signal is generated by the DPD method. In the DPD method, a tracking error signal is generated from a diagonal difference signal of a photodiode divided into four (one of which is along the track direction). In this case, the output difference between the photodiodes 22A and 22C and the photodiodes 22B and 22D is generated. Should be obtained.

When a tracking error signal is generated from the outputs of the photodiodes 22A to 22D, the output of the differential amplifier 6A follows the output of the photodiode 22A, and the output of the differential amplifier 6B follows the original. The output of the differential amplifier 22C and the output of the differential amplifier 6C are the output of the photodiode 22B when traced back, and the output of the differential amplifier 6D is the output of the photodiode 22D when traced back.

For this reason, the adder 4A for adding the output of the differential amplifier 6A and the output of the differential amplifier 6B adds the output of the photodiode 22A and the output of the photodiode 22C, and performs a differential operation with the output of the differential amplifier 6C. In the adder 4B for adding the output of the amplifier 6D, the output of the photodiode 22B and the output of the photodiode 22D are added. Next, in the differential amplifier 61, the output of the adder 4A and the output of the adder 4B are differentiated. Since the signal is amplified, the output of the differential amplifier 61 becomes the output difference between the photodiodes 22A and 22C and the photodiodes 22B and 22D, and a tracking error signal is obtained.

Although not shown hereafter, the output of the differential amplifier 61 is input to the analog front end of the main board by wiring such as a flexible cable, and is amplified and received by the photodiodes 21A to 21D.
Waveform shaping including unification of polarities in the case of receiving light at A to 22D is performed, and then binarized into digital data to perform tracking servo processing.

FIG. 7 is a diagram showing a second configuration of an optical recording / reproducing circuit of an optical pickup using a light generator and a photodetector in an optical system according to an embodiment of the present invention. The polarities of the photodiodes 21A to 21D and 22A to 22D and the polarities of the inputs of the differential amplifiers 6A to 6D and 61 are not limited to those shown in FIG. 7 as in the first configuration. Further, depending on the case, the addition may be performed simultaneously with the addition by the adders 4A and 4B as in the first configuration.

As described above, the embodiment of the present invention has been described with an increased configuration. However, the position of the signal switching by the switch is not limited to the above. When the light emitting wavelength of the laser diode as a light source differs between a plurality of optical disks of different formats, generally, the sensitivity of the photodiode changes depending on the wavelength of the incident light, and the reflectivity of the optical disk may differ.

In the above case, a problem arises that the dynamic range of the obtained tracking error signal changes for each optical disk because the output magnitude of the photodiode changes for each optical disk.

In this case, when changing the combination of the photodiodes when changing the optical disk, one or both of the change of the I / V conversion efficiency of the IV converter and the change of the amplification factor of the amplifier are changed. Simultaneous operation makes it possible to unify the dynamic range of the finally obtained tracking error signal.

In recent years, in the optical pickup, the functions of the components have been integrated for the purpose of reducing the size and cost, and this has also been performed for the optical recording / reproducing circuit. In addition to the V converter and the adder integrated on the same semiconductor substrate or the same semiconductor package, in addition to these, the light generator integrated on the same semiconductor substrate or the same semiconductor package has begun to be used.

The optical recording / reproducing circuit of the optical pickup of the present invention can be similarly integrated.
FIG. 8 is a diagram showing a first configuration of an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention integrated on the same semiconductor substrate.

In the configuration of FIG. 8, the optical recording / reproducing circuit of the optical pickup comprises a semiconductor substrate 1, a photodetector 2,
It has a V converter, an adder 4, a differential amplifier 6, and photodiodes 21A to 21D.

FIG. 9 is a diagram showing an optical recording / reproducing circuit of an optical pickup in which a light generator, a photodetector, an IV converter, and an adder / subtractor are integrated in the same semiconductor package in one embodiment of the present invention. (A) is a top view and (A) is a cross-sectional view taken along the line bb 'of (A). Further, in the configuration of FIG. 9, the optical path between the light emitted from the light generator and the light incident on the light generator is separated by using a hologram optical element.

In the configuration shown in FIG. 9, the optical recording / reproducing circuit of the optical pickup comprises a semiconductor substrate 1, a photodetector 2,
V converter 3, adder 4, differential amplifier 6, mirror 8
, Laser diodes 9A and 9B, and photodiodes 21A to 21D and 22A to 22D.

The photodetector 2, the IV converter 3, the differential amplifier 6, and the adder 4 are formed on the semiconductor substrate 1 by a semiconductor process, and the laser diodes 9A and 9B and the mirror 8
Are mounted on the semiconductor substrate 1. The photodiodes for controlling the output of the laser diodes 9A and 9B are not shown.

FIG. 10 is a diagram showing a configuration of an optical recording / reproducing circuit of an optical pickup including a portion of an optical system according to an embodiment of the present invention. Hereinafter, an optical path until the laser light emitted from the laser diode 9A in the present embodiment enters the photodiodes 21A to 21D of the photodetector 2 will be described with reference to FIG.

The laser beams emitted from the laser diodes 9A and 9B are reflected upward at right angles by the mirror 8,
The light enters the hologram optical element 12.
The laser beam incident on the hologram optical element 12 passes through the hologram optical element 12, passes through an optical system such as a collimator lens, a polarizing plate, and a mirror, which are omitted here, and forms an image on an optical disk 11 by an imaging lens 10, and The reflected light returns along the same optical path and enters the hologram optical element 12 again.

Then, the reflected light from the optical disk 11 deflected by the hologram optical element 12 enters the photodiodes 21A to 21D of the photodetector 2. Note that the laser light emitted from the laser diode 9B is
The optical path up to the input to the photodiodes 22A to 22D is similarly described. The embodiment of the present invention is not limited to the configurations shown in FIGS. 8 and 9, but may be a configuration in which an optical recording / reproducing circuit is integrated in another configuration.

[0111]

As described above, according to the first aspect of the present invention, the combination of photodiodes used for signal calculation and the circuit configuration after the IV converter are changed according to the format of the optical disk to be reproduced. By
The number of components and the circuit configuration can be simplified, and it is possible to support optical disks of a plurality of different formats.

According to the second aspect of the present invention, the I / V of the IV converter is interlocked with the change of the combination of the photodiodes according to the format of the optical disk to be reproduced.
By changing the conversion efficiency, it is possible to eliminate a difference in dynamic range of a signal caused by a change in sensitivity due to a wavelength of incident light of a photodiode and a change in reflectance of an optical disk for each format.

According to the third aspect of the present invention, the wavelength of the light incident on the photodiode is changed by changing the amplification factor of the amplifier in conjunction with the change of the combination of the photodiodes according to the format of the optical disk to be reproduced. It is possible to eliminate a difference in dynamic range of a signal generated due to a change in sensitivity due to the above or a change in reflectivity of an optical disk for each format.

According to the fourth aspect of the present invention, at least one or more functions after the photodetector and the IV converter are formed on the same semiconductor substrate or in the same semiconductor package, so that a circuit The mounting area can be reduced.

According to the fifth aspect of the present invention, by integrating at least one light generator in the same package, it is possible to reduce the circuit mounting area.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical system part in an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing a configuration of a light generator included in an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention. FIG. 2A is a top view of the light generator, and FIG. 3 is a cross-sectional view taken along the line aa ′ in FIG.

FIG. 3 is a diagram showing a configuration including a photodetector in an optical recording / reproducing circuit of the optical pickup according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a first configuration of an optical recording / reproducing circuit of an optical pickup using a light generator and a photodetector in an optical system according to an embodiment of the present invention.

FIGS. 5A to 5D are diagrams showing output voltages by an IV converter of the optical recording / reproducing circuit of the optical pickup according to one embodiment of the present invention.

FIG. 6 is a diagram showing connection patterns of switches of an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention. FIG. 6A shows a configuration for creating a tracking error from outputs of photodiodes 21A to 21D. ,(I)
Is a configuration for creating a tracking error from the outputs of the photodiodes 22A to 22D.

FIG. 7 is a diagram illustrating a second configuration of an optical recording / reproducing circuit of an optical pickup using a light generator and a photodetector in an optical system according to an embodiment of the present invention.

FIG. 8 is a diagram showing a first configuration of an optical recording / reproducing circuit of an optical pickup according to an embodiment of the present invention, which is integrated on the same semiconductor substrate.

FIG. 9 is a diagram showing an optical recording / reproducing circuit of an optical pickup in which a light generator, a photodetector, an IV converter, and an adder / subtractor are integrated in the same semiconductor package in one embodiment of the present invention; ) Is a top view, and (a) is b- in the top view.
It is sectional drawing of b '.

FIG. 10 is a diagram showing a configuration of an optical recording / reproducing circuit of an optical pickup including a part of an optical system according to an embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate 2 photodetector 3 IV converter 4, 4A, 4B adder 5 constant voltage source 6, 6A to 6D, 61 differential amplifier 7 switch 8 mirror 9A, 9B laser diode 10 imaging lens 11 optical disk 12 Hologram optical element 21, 21A to 21D, 22, 22A to 22D Photodiode 31A to 31D, 32A to 32D IV converter 101 Light generator 102 Photodetector 103 Beam splitter IN1, IN2 Input terminal OUT1, OUT2 Output terminal

Claims (5)

[Claims] 1. A plurality of light generators for accommodating a plurality of optical disks of different formats, a photodetector comprising a plurality of photodiodes, and a plurality of I / Os for converting a current generated by the photodetector into a voltage. −
A V converter; an amplifier for amplifying the output of the IV converter; a plurality of adder / subtracters for adding, subtracting, and adding / subtracting the output of the amplifier to obtain an RF signal, a tracking error signal, and a focus error signal; Wherein the position at which the reflected light from the optical disc is incident on the photodetector is different among the plurality of light generators, and the photodetector is one for each incident position of the reflected light from the optical disc.
The output of each photodiode is differentially amplified, and at least one of the RF signal, the tracking error signal, and the focus error signal is signaled in accordance with the format of the optical disc to be reproduced. An optical recording / reproducing circuit for an optical pickup, wherein a combination of the photodiodes used in the calculation of (i) and a circuit configuration subsequent to the IV converter are changed. 2. The I / V conversion efficiency of the IV converter is changed in conjunction with a change in a combination of the photodiodes according to a format of the optical disk to be reproduced. Optical recording / reproducing circuit of optical pickup. 3. The optical recording / reproducing circuit of an optical pickup according to claim 1, wherein an amplification factor of said amplifier is changed in conjunction with a change of a combination of said photodiodes according to a format of said optical disc to be reproduced. . 4. The semiconductor device according to claim 1, wherein at least one or more functions after the photodetector and the IV converter are formed on the same semiconductor substrate or in the same semiconductor package. 2. An optical recording / reproducing circuit for an optical pickup according to claim 1. 5. The method according to claim 1, wherein at least one of said light generators is integrated in a same package.
An optical recording / reproducing circuit for an optical pickup according to any one of the preceding claims.