JPS63187426A - Photodetector for pickup - Google Patents

Abstract

PURPOSE:To attain the adjustment of the variance among pickups by building in a six-split photodiode and a variable amplifier circuit/signal processing circuit section amplifying an output signal of each photodiode and applying signal processing to the result into a package of a DIP8 terminal so as to facilitate the handling in the manufacture and assembling or the like. CONSTITUTION:The photodiode PD and the amplifier circuit/signal processing circuit section SC are built in the DIP8 terminal package including five output terminals leading out single or combined signals of the photodiode, two high and low power terminals and an adjusting terminal connected to the amplification factor variable means of the amplifier circuit. Thus, the output signal of the photodiode PD is subject to amplification and signal processing in one package, a desired signal is extracted with less effect of noise and the stray capacitance such as wire capacitance is decreased to improve the response speed and compactness and light weight are attained as the pickup. Moreover, the package is an existing DIP8-pin terminal package the handling at manufacture and assembling is facilitated and the dispersion among pickups is adjusted simply.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a light receiving element for optical pickup used in compact discs, video discs, etc.

<Summary of the invention> A 6-segment photodiode and a method for amplifying and amplifying these output signals.
By integrating the signal processing amplifier circuit and signal processing circuit into one package with 8 DIP terminals, it is possible to improve noise resistance, response speed, and make it more compact. Variations in the pickup can also be adjusted using the adjustment terminal.

<Prior Art> Optical pickup units of compact discs, video discs, etc. are generally equipped with a photodiode divided into six parts into one chip as a light-receiving element. Direct current light emitted by a semiconductor laser mounted on the optical pickup section is reflected on the optical disk surface according to its pit state, becoming modulated light containing signal components, which is detected by a six-divided photodiode. The output current of the photodiode is amplified by an amplifier circuit, and then separated by a signal processing circuit into an RF multiplied signal (video and audio signals) and a control signal for controlling the positional relationship between the optical disk surface and the optical pickup section, and then used. ing.

Conventionally, the above-mentioned optical pickup section was generally not equipped with an amplification circuit for the output current of the photodiode or a signal processing circuit.
The output current of the photodiode was transmitted via lead wires to an amplifier circuit installed outside the optical big amplifier section.

<Problems to be solved by the invention> However, since the output current of a photodiode is small, ranging from several microamperes to several tens of microamperes, increasing the length of the lead wires may cause noise and increase the wiring capacitance.
There was a drawback that the response speed decreased. Furthermore, when amplifier circuit components and signal processing circuit components are mounted on the optical pickup section, these components increase the weight and size of the pickup section.

The present invention solves these conventional drawbacks and
By incorporating it into the P8 terminal package, it is easy to handle during manufacturing, assembly, etc., and one of the 8 terminals
An object of the present invention is to provide a light-receiving element for optical pickup which can also adjust variations between pickups by using one as a control terminal.

Means for solving the above problems〉 A 6-divided photodiode made of one chip or multiple chips and an amplifier circuit/signal processing circuit section that amplifies and processes the output signal of each of these photodiodes are built into a package with 8 DIP terminals. do. Five of the eight terminals are output terminals for deriving individual or combined photodiode signals;
The terminals are two high and low power supply terminals. The amplifier circuit does not have amplification degree variable means, and the remaining one of the eight terminals
The terminal is connected to this amplification degree variable means and serves as an adjustment terminal for adjusting variations between pickups.

Effects> According to the above structure, the output signal of the photodiode is amplified and processed within one package, so the desired signal can be extracted with less influence of noise, and stray capacitance such as wiring capacitance can be reduced. It is possible to improve the response speed, and it is also possible to make the pickup more compact and lightweight.
Furthermore, the package is an existing DIP 8-pin terminal, which facilitates handling during manufacturing, assembly, etc., and also allows for easy adjustment of variations between pickups.

<Example> The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of a circuit configuration. The PD is a 6-divided photodiode section having light-receiving pattern areas divided into 6 sections A to F, and is formed on one chip together with an amplifier circuit and a signal processing circuit section SC, which will be described later. As for the package structure, it is constructed as a DIP 8-terminal element in which an ethip in which a 6-divided photodiode section PD and an amplifier circuit/signal processing circuit section SC are all housed in one package.

The photodiode part PD&i has a light receiving pattern as shown in Fig. 2. The patterns A to C formed clockwise in the center are used for RF multiplication signals and focus control signals, and the E and F patterns at both ends are used for tracking control. is generating a signal.

6-divided photodiode section PDi-1: each current-voltage amplifier Gz in the amplifier circuit/signal processing circuit section SC in FIG.
, connected to G2. G3. G4 is a summing amplifier, G
5. G6 is a subtraction amplifier. Then, due to the circuit configuration of these amplifier circuit/signal processing circuit section SC, the sum signal of PD (A) and PD (C) is output from the first terminal T0 (
VA+. ), PI] A) and P D (
The difference signal output (V(A+.)-(B+D)) between the sum signal of C) and the sum signal of PD(B) and PD[F]), the third
PD(B) and PDQ)) sum signal output (V
B+D), PD(A) and PDCE3 from the 4th terminal T4
) and PD (C) and PD□) (7) Sum signal output (vA+B
+C+D), PIXE) from the 7th terminal T7) and PD(
The difference signal output (V,, -,) of F) is derived. Fifth
The terminal T5 is a power supply terminal for Vcc voltage, and the sixth terminal T6 is a power supply terminal for ground (GND)1.The reference signal Vr applied to one terminal of the subtraction amplifier Gs and G6 is
ef is supplied from a constant voltage circuit VR built in the amplifier circuit/signal processing circuit section SC.

Further, the current-voltage amplifier Gs-G2 has an amplification degree variable means, and the eighth terminal T8 is connected to the amplification degree variable terminal.

According to the structure of the IP8 terminal element, the amplifier circuit/signal processing circuit section SC is housed in one package together with the 6-divided photodiode section PD, and the response speed is increased by the lead wire connecting these as in the conventional case. Moreover, since only one package element is mounted in the optical pickup, there is an advantage that the weight and size of the optical pickup can be reduced.

By the way, in compact discs, video discs, etc., the amount of light incident on the photodiode of the optical pickup section changes due to variations in the radiation intensity of the semiconductor radar and the characteristics of optical components in the optical pickup section. The amplification degree a of the current-voltage amplifiers Gl and G2 of the eighth element T8 is changed to adjust the dispersion between the optical pickups. The amplification degree can be changed by changing the value of the external resistor at the 8th terminal T8, or changing the supply voltage, etc. PD (A) and PD can be changed from the first terminal T1 through the circuit configuration.
(C) sum signal output (VA+.), p from second terminal T2
D (B) and PD) sum signal output (VB + D), PD (A), PD (B) and PD (C) from the third terminal T3
and PDQ)) sum signal output (VA+B+.+D), 6th
PD ■ signal output (V, ) from terminal T6, 7th terminal T
7 to derive the signal output (V, ) of PD (F'). The fourth terminal T4 is a Vcc voltage power supply terminal, and the fifth terminal T5 is a ground (GND) power supply terminal. Eighth terminal TsIi This terminal is prepared as an adjustment terminal as in the previous embodiment, and is connected to the variable amplification terminal of the current-voltage amplifier G1+02.

FIG. 4 is an example of a circuit configuration showing still another embodiment.

Here, buffers B, , B, are added to the one in FIG. Buffer B1 is connected between the operation control terminal of each current-voltage amplifier Gl (A1.G1) corresponding to PD (A) and PD (B) and the sixth terminal T6.
, each current-voltage amplifier Gt (
C), Gl (D) is connected between the operation control terminal and the seventh terminal T7.

Normally, the sixth terminal T6 derives the signal output (vF, ), and the seventh terminal T7 derives the signal output (V2). At this time, the signal output is weak and the buffers Bz, B
2, it does not affect the operation of the current-voltage amplifier G1. However, when a voltage higher than a predetermined level is applied from the sixth terminal T6 or the seventh terminal T7, the operation of the current-voltage amplifier G1 is substantially completely prohibited.

For example, when actually using a light-receiving element for optical pickup, it is necessary to perform so-called initial adjustment and alignment in which the entire main spot from the semiconductor laser is adjusted in advance to the center of the turns A to D of the photodiode. From this slant, the light receiving element for the optical pick amplifier, A,
It is required to independently extract output signals corresponding to the B, C, and D patterns. The structure shown in Fig. 4 is designed to deal with this problem, and by controlling the t terminal of the DIP8 terminal, the A
The corresponding amplifier operation can be selected, and the output signals A, B, C, and D can be derived using other terminals.

The above operations are summarized in the table below.

It goes without saying that the embodiments shown in FIGS. 3 and 4 can provide the same effects as the embodiment shown in FIG. 1.

<Effects of the Invention> As described above, according to the present invention, it is possible to provide a useful light-receiving element for a pickup that is small, lightweight, highly reliable, and allows for adjustment of variations in the pickup.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a pattern diagram of a 6-segment photodiode section, FIG. 3 is a circuit diagram showing another embodiment of the present invention, and FIG. FIG. 7 is a circuit configuration diagram showing still another embodiment of the present invention. PD...6-segment photodiode section, SC...
Amplification circuit/signal processing circuit section, G1 and G2... current-voltage amplifier, T1 to T8... terminals. Agent Patent attorney Itaru Sugiyama Mata (and 1 other person) Figure 1 n Figure 2

Claims (1)

[Claims] A 1.6-split type photodiode, an amplification circuit/signal processing circuit section for the photodiode, and the amplification circuit has amplification degree variable means. A pickup characterized in that it is built in a DIP 8-terminal package that includes five output terminals for deriving individual or combined signals, two high and low power supply terminals, and one adjustment terminal connected to the amplification degree variable means of the amplifier circuit. Light receiving element.