JPH05205289A - Optical pickup - Google Patents

Abstract

PURPOSE:To provide a downsized optical pickup for optically recording, reproducing or erasing data in which the number of operational amplifiers is reduced and noise is suppressed. CONSTITUTION:PD1a-PD1h are light receiving elements, each split into eight sections, and which detect laser light reflected on an optical disc. Adders/ amplifiers IC1, IC2, IC3, IC4 add and amplify output currents from the PD1b and PD1h, PD1d and PD1f, PD1a and PD1g, and PD1c and PD1e, respectively. Adders/amplifiers IC5, IC6, IC7 and IC8 add and amplify output signals from adders/amplifiers IC1 and IC2, IC3 and IC4, IC1 and IC3, and IC2 and IC4, respectively. Output signals from the adders/amplifiers IC5 and IC6 are fed to a phase comparator A to produce a focus control signal. Output signals from the adders/ amplifiers IC7 and IC8 are fed to a phase comparator B to produce a tracking control signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for optically recording, reproducing and erasing a signal by projecting a light spot on a disc on which information is recorded.

[0002]

2. Description of the Related Art In recent years, an optical pickup has been used as a device for optically recording, reproducing and erasing information on a disc.

A conventional optical pickup will be described below. FIG. 5 shows an example of a conventional optical pickup. In FIG. 5, PD1a to PD1h are the respective dividing elements of the eight-division light receiving element, which detect the laser light reflected from the optical disc. PD1a is the first element on the left side with respect to the traveling direction of the track, and PD1b
Is the second element on the left side, PD1c is the third element on the left side, P
D1d is the fourth element on the left side. PD1e is the first element on the right side with respect to the traveling direction of the track.
Is the second element on the right side, PD1g is the third element on the right side, P
D1h is the fourth element on the right side.

In recent years, the focus control signal is a sum signal of the light amount signals of the light receiving elements PD1a, PD1c, PD1e, and PD1g, and the light receiving elements PD1b, PD1d, and PD1f.
And PD1h are extracted by phase comparison with the sum signal of the light amount signals of PD1h, and the tracking control signal is obtained as the light receiving element PD1.
a, PD1b, PD1g, and PD1h, the sum signals of the respective light amount signals, and the light receiving elements PD1c, PD1d, PD1e, and PD.
A total phase difference method has been proposed in which each light quantity signal of 1f is extracted by phase comparison with the sum signal.

In this case, the output currents from the light receiving elements PD1a to PD1h are respectively voltage-converted and amplified by the corresponding operational amplifiers IC1 to IC8. The adding amplifier IC9 is the operational amplifiers IC2, IC4, IC6, IC.
The output signals of 8 are added, and the addition amplifier IC10 adds the output signals of the operational amplifiers IC1, IC3, IC5 and IC7. The addition amplifier IC11 is the operational amplifier IC3,
The output signals of IC4, IC7, and IC8 are added, and the addition amplifier IC12 is added to the operational amplifiers IC1, IC2, IC5.
The output signals of IC6 are added.

As a result, the output signal of the summing amplifier IC9 is the light receiving elements PD1b, PD1d, PD1f and PD.
Each output signal of 1h is added and amplified,
The output signal of the adding amplifier IC10 is the output signal of each of the light receiving elements PD1a, PD1c, PD1e, and PD1g added and amplified.
The output signals of C9 and IC10 are input to the phase comparator A to obtain a focus control signal. In addition, the addition amplifier IC
The output signal of 11 is the light receiving elements PD1c, PD1d and P
The output signals of D1e and PD1f are added and amplified, and the output signal of the addition amplifier IC12 is the light receiving elements PD1a, PD1b, PD1g, and PD1h.
The output signals of the addition amplifiers IC11 and IC12 are input to the phase comparator B to obtain the tracking control signal.

[0007]

However, the conventional optical pickup has a problem in that the number of operational amplifiers is large and the configuration is complicated, which increases noise.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a small-sized optical pickup which requires a small number of operational amplifiers and therefore has low noise.

[0009]

In order to achieve this object, an optical pickup according to the present invention comprises an 8-split light-receiving element and each of the split-elements of the 8-split light-receiving element on the left side 1 with respect to the direction of travel of a disk track. A first summing amplifier that adds and amplifies the output signal of the second element and an output signal of the third element on the right side, and a second summing amplifier that adds and amplifies the output signal of the second element on the left side and the output signal of the fourth element on the right side. A summing amplifier, a third summing amplifier that sums and amplifies the output signal of the third element on the left side and the output signal of the first element on the right side, and an output signal of the fourth element on the left side and an output signal of the second element on the right side. A fourth summing amplifier for summing and amplifying, and a fifth summing and amplifying output signal of the first summing amplifier and output signal of the third summing amplifier.
Adder amplifier, a sixth adder amplifier for adding the output signal of the second adder amplifier and the output signal of the fourth adder amplifier, an output signal of the first adder amplifier, and the second adder amplifier Of the output signal of the third addition amplifier and an eighth addition amplifier that adds and amplifies the output signal of the third addition amplifier and the output signal of the fourth addition amplifier. A structure for obtaining a focus control signal from the output signal of the amplifier and the output signal of the sixth summing amplifier and a tracking control signal from the output signal of the seventh summing amplifier and the output signal of the eighth summing amplifier ing.

[0010]

With this structure, it is possible to reduce the number of necessary operational amplifiers and prevent an increase in noise.

[0011]

【Example】

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of an optical pickup according to the first embodiment of the present invention. PD1a ~
The PD 1h is a light receiving element of 8 divisions, which detects the laser light reflected from the optical disk. PD1a
Is the first element on the left side with respect to the traveling direction of the track, PD1b is the second element on the left side, PD1c is the third element on the left side, and PD1d is the fourth element on the left side. PD1
e is the first element on the right side with respect to the traveling direction of the track, PD1f is the second element on the right side, PD1g is the third element on the right side, and PD1h is the fourth element on the right side. A summing amplifier IC1 sums and amplifies the output signals of the light receiving elements PD1b and PD1h, and a summing amplifier IC2 measures the light receiving elements PD.
The output signals of 1d and PD1f are added and amplified to add amplifier I
C3 adds and amplifies the output signals of the light receiving elements PD1a and PD1g, and the addition amplifier IC4 outputs the light receiving elements PD1c and PD1c.
The output signal of PD1e is added and amplified. Summing amplifier IC5
Is a summing amplification of the output signals of the summing amplifiers IC1 and IC2, and a summing amplifier IC6 is a summing amplifier IC3, IC4.
Is added and amplified, the addition amplifier IC7 adds and amplifies the output signals of the addition amplifiers IC1 and IC3, and the addition amplifier IC8 adds and amplifies the output signals of the addition amplifiers IC2 and IC4.

As a result, the output signal of the amplifier IC5 is the light receiving elements PD1b, PD1d, PD1f and PD.
Each output signal of 1h is added and amplified,
The output signal of the summing amplifier IC6 is the light receiving element P.
The output signals of D1a, PD1c, PD1e, and PD1g are added together and amplified.
The output signals of IC5 and IC6 can be input to the phase comparator A to obtain a focus control signal. The output signal of the summing amplifier IC7 is the light receiving elements PD1c and PD1.
The output signals of d, PD1e, and PD1f are added and amplified, and the output signal of the addition amplifier IC8 is the light receiving elements PD1a, PD1b, PD1g, and PD.
Each output signal of 1h is added and amplified,
The output signals of the summing amplifiers IC7 and IC8 can be input to the phase comparator B to obtain a tracking control signal.

Moreover, the required number of amplifiers is 12 as in the conventional example.
It is possible to reduce the number of points from eight to eight, so that a small optical pickup with low noise can be realized.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a second embodiment of the present invention. The difference from FIG. 1 is the addition amplifier IC.
The point is that the capacitors C1 to C4 are inserted between the inputs a, d, f, g of 1 to IC4 and the reference potential. In this case, the phases of the signals input to the inputs a and b of the addition amplifier IC1, the phases of the signals input to the inputs c and d of the addition amplifier IC2, and the signals input to the inputs e and f of the addition amplifier IC3. And the phase of the signals input to the inputs g and h of the summing amplifier IC4 can be adjusted for each summing amplifier IC, and the dynamic range of the focus control signal and the tracking control signal can be improved. is there. A similar effect can be obtained by using resistors instead of the capacitors C1 to C4.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows a third embodiment of the present invention. Differences from FIG. 1 are as follows. The wirings w1, w2, w3, and w4 are made of aluminum wiring that connects semiconductors to each other when the light receiving element is manufactured.
The wiring w1 is formed on the DB, and the wiring w1 has a light receiving element PD1b.
And the light receiving element PD1h are connected, and the wiring w2 is connected to the light receiving element PD1h.
1d and the light receiving element PD1f are connected, the wiring w3 connects the light receiving element PD1a and the light receiving element PD1g, and the wiring w4 connects the light receiving element PD1c and the light receiving element PD1e. Wiring w
1, w3 and wirings w2, w4 are formed in different layers and are insulated from each other.

The output currents from the wirings w1 and w2 are additively amplified by the adding amplifier IC1, and the output currents from the wirings w3 and w4 are additively amplified by the adding amplifier IC2.
Also, the output current from the wirings w1 and w3 is the summing amplifier IC.
3, the output currents from the wirings w2 and w4 are added and amplified by the addition amplifier IC4. As a result, the output signals of the addition amplifiers IC1 and IC2 are input to the phase comparator A to obtain the focus control signal, and the addition amplifier I
The output signals of C7 and IC8 can be input to the phase comparator B to obtain a tracking control signal.

In this case, the number of operational amplifiers can be further reduced by 4 points as compared with the first embodiment, and further, by forming the wiring on the light receiving element substrate PDB at the time of manufacturing the light receiving element, it is possible to reduce variations in the wiring extension amount. Therefore, it is possible to configure a smaller optical pickup with lower noise.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram showing a portion of the light receiving element of the fourth embodiment of the present invention. The summing amplifier and the phase comparator are common to those in FIG. The difference from FIG. 3 is that only the wirings w1 and w3 are formed on the light receiving element substrate PDB, and the wirings w2 and w4 are formed on the FPC board FP1 on which the light receiving elements are mounted.
In this case, there is a merit that it is not necessary to cross the wiring three-dimensionally on the light receiving element substrate PDB.

Therefore, it is possible to greatly reduce the steps of aluminum wiring at the time of manufacturing the light receiving element, and further, the FPC board FP1.
Since there is no need to intersect even on the top, FP with a single-sided pattern
It is possible to manufacture with the C substrate FP1, which facilitates the manufacturing.

[0020]

As described above, according to the present invention, the output signal of the first element on the left side and the output signal of the third element on the right side are added to each divided element of the eight-division light receiving element with respect to the track traveling direction of the disk. A first summing amplifier for amplifying, a second summing amplifier for summing and amplifying the output signal of the second element on the left side and the output signal of the fourth element on the right side, an output signal of the third element on the left side, and a first signal for the right side. A third summing amplifier that sums and amplifies the output signal of the element, a fourth summing amplifier that sums and amplifies the output signal of the fourth element on the left side and the output signal of the second element on the right side, and the first summing amplifier A fifth summing amplifier that sums and amplifies the output signal and the output signal of the third summing amplifier;
A sixth summing amplifier for summing the output signal of the second summing amplifier and the output signal of the fourth summing amplifier; and the first summing amplifier.
A summing amplifier that amplifies the output signal of the summing amplifier and the output signal of the second summing amplifier, and amplifies the output signal of the third summing amplifier and the output signal of the fourth summing amplifier. An eighth addition amplifier, which obtains a focus control signal from the output signal of the fifth addition amplifier and the output signal of the sixth addition amplifier, and outputs the focus control signal from the seventh addition amplifier and the eighth addition amplifier. By the circuit configuration for obtaining the tracking control signal from the output signal of (1), the number of operational amplifiers is small, and thus a small optical pickup with low noise is realized.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of an optical pickup according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical pickup according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical pickup according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional optical pickup.

[Explanation of symbols]

 PD1a to PD1h 8-divided light receiving element IC1 to IC12 operational amplifier A, B phase comparator a to h each input to IC1 to IC4 C1 to C4 capacitors w1 to w4 wiring PDB light receiving element substrate FP1 FPC board

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yutaka Murakami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshiaki Ikeda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Kenichiro Urairi 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Tadamasa Shibata 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. An 8-split light-receiving element and an output signal of a first element on the left side and an output signal of a third element on the right side of the 8-split light-receiving element with respect to the track traveling direction of a disk are summed and amplified. A first summing amplifier, a second summing amplifier that sums and amplifies the output signal of the second element on the left side and the output signal of the fourth element on the right side, an output signal of the third element on the left side, and a first element on the right side Of the output signal of the second addition element, the fourth addition amplifier for addition amplification of the output signal of the fourth element on the left side and the output signal of the second element of the right side, and the output of the first addition amplifier. A fifth summing amplifier that sums and amplifies the signal and the output signal of the third summing amplifier;
A sixth summing amplifier for summing the output signal of the second summing amplifier and the output signal of the fourth summing amplifier; and the first summing amplifier.
A summing amplifier that amplifies the output signal of the summing amplifier and the output signal of the second summing amplifier, and amplifies the output signal of the third summing amplifier and the output signal of the fourth summing amplifier. An eighth addition amplifier, which obtains a focus control signal from the output signal of the fifth addition amplifier and the output signal of the sixth addition amplifier, and outputs the focus control signal from the seventh addition amplifier and the eighth addition amplifier. An optical pickup that obtains a tracking control signal from the output signal of. 2. A phase shifter for delaying at least one of the signals when the output signals of the light receiving elements are added and amplified.
The optical pickup described. 3. The optical pickup according to claim 2, wherein the phase shifter comprises a capacitor and a resistor. 4. The optical pickup according to claim 1, wherein when the output signals of the light receiving element are added and amplified, they are coupled by wiring on the light receiving element substrate without using a summing amplifier. 5. The optical pickup according to claim 4, wherein at least one portion of the wiring is on another substrate.