JPH05223922A - Photoelectric conversion circuit for distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a photoelectric conversion circuit for a distance measuring apparatus which has a PSD and can select and detect only signal light which has been modulated into specific frequency. CONSTITUTION:A photoelectric conversion circuit for a distance measuring apparatus comprises a PSD 20 for receiving signal light modulated at specific frequency to convert into photoelectric conversion current, a differential amplifier 60 having a non-inverting input terminal 70 and an inverting input terminal 80 wherein the output is directly fed back to the inverting input terminal 80, and switching means 30, 40 for changing over connection of a first electrode 201 of the PSD 20 to the non-inverting input terminal 70 of the differential amplifier 60 and connection to it with first and second electrodes 201, 202 connected. A resonator 50 for resonating against predetermined frequency is provided between the non-inverting input terminal 70 of the differential amplifier 60 and the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device applied to an automatic focusing device and a distance measuring device using light in a camera or the like, and more particularly to a semiconductor position detector (hereinafter referred to as PSD (P
osition Sensitive Device)) is used to select and detect only the signal light modulated to a specific frequency.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional photoelectric conversion circuit for a distance measuring device, in which 20 is a first
And a second electrode 201, 202, which is a semiconductor position detector (PSD) that receives light including signal light modulated at a predetermined frequency and converts it into photoelectric conversion current, and 10 is the P
Power supply for applying reverse bias voltage to SD20, 600 is the first
Operational amplifier, 601 is a second operational amplifier, 800, 801
Are the inverting input terminals of the first and second operational amplifiers, 70
Reference numerals 0 and 701 denote non-inverting input terminals of the first and second operational amplifiers, 900 and 901 denote output terminals of the first and second operational amplifiers, and 1 denotes an output terminal 900 of the first operational amplifier 600 and an inverting input terminal 800. A resistor for converting a current into a voltage, which is connected between the two, and 2 is an output terminal 90 of the second operational amplifier 601.
A resistor connected between 1 and the inverting input terminal 801 for converting a current into a voltage. FIG. 6 is a diagram showing the PSD 20. In the diagram, 201 is the first anode,
202 is a second anode and 203 is a cathode.

The basic operation of the photoelectric conversion circuit for a distance measuring device constructed as above will be described. In this device, a signal light source that is amplitude-modulated at a predetermined frequency is used, and a signal light having a constant frequency is emitted from the light source. The light including the signal light modulated at the predetermined frequency is P
The light enters the SD 20, is photoelectrically converted by the PSD 20, becomes a photoelectric conversion current, is converted from a current by the resistors 1 and 2 into a voltage, is amplified by each differential amplifier 600, 601, and is output as a voltage value.

The resistors 1 and 2 are differential amplifiers 600 and 6, respectively.
01 inverting input terminals 800 and 801 and outputs 900 and 90
It is connected to each one and negative feedback is applied. Therefore, when no spot light is incident, that is, in the standby state, the inverting input terminals 700 and 701 and the non-inverting input terminals 800 and 801 have the same potential, and the differential amplifiers 600 and 601 can be said to be in a balanced and stable state.

When spot light enters the PSD 20 reverse-biased by the DC power source 10, the PSD 2
The photoelectric conversion current is converted into a photoelectric conversion current at 0, and the photoelectric conversion current having a value corresponding to the distance from the electrical center position of the PSD 20 to the position of the center of gravity of the incident spot light is divided into the first anode 201 and the second anode 202. And output.

When the PSD 20 is irradiated with the spot light in this manner, photoelectric conversion currents are output from the first anode 201 and the second anode 202 of the PSD 20, respectively, but are output from the first anode 201. The photocurrent is converted from a current to a voltage by the resistor 1, and the output terminal 900
Is obtained as a voltage value. Similarly, the second anode 202
The photocurrent output from the device is converted from a current to a voltage by the resistor 2 and is obtained as a voltage value at the output terminal 901. By taking the ratio of the voltage values of the output terminals 900 and 901 obtained in this way, it is possible to perform distance measurement and automatic focusing by confirming the light receiving position on the PSD 20.

[0007]

Since the conventional photoelectric conversion circuit for a distance measuring device is constructed as described above, the PSD converts all the received light energy into a current, and the photocurrent is converted into the resistance 1 or There is a problem in that light of various frequencies such as sunlight and artificial light is detected because the resistance 2 converts current into voltage.

On the other hand, in an auto-focusing device such as a camera or a distance measuring device, a signal light of a specific frequency that has been subjected to a predetermined modulation is emitted from a light source, and the signal light reflected by an object is received and detected. , Automatic focusing and distance measurement are performed, but the photoelectric conversion circuit for the conventional distance measuring device is as described above.
Since unnecessary light other than the signal of the specific frequency is also received, there is a problem that only the desired signal light component cannot be extracted.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a photoelectric conversion circuit for a distance measuring device which can select and detect only signal light modulated to a specific frequency. And

[0010]

A photoelectric conversion circuit for a distance measuring device according to the present invention has first and second electrodes, receives light including signal light modulated at a predetermined frequency, and photoelectrically converts the light. A semiconductor position detector for converting into a converted current; a differential amplifier having a non-inverting input terminal and an inverting input terminal, the output of which is directly fed back to the inverting input terminal; Switching means for switching between connecting one electrode to the non-inverting input terminal of the differential amplifier or connecting it to the first and second electrodes in a connected state, and electrically for the predetermined frequency. A resonator that resonates with is provided between the non-inverting input terminal of the differential amplifier and the ground.

Further, a photoelectric conversion circuit for a distance measuring device according to the present invention has first and second electrodes, receives light including signal light modulated at a predetermined frequency, and converts it into a photoelectric conversion current. A semiconductor position detector, a differential amplifier having a grounded non-inverting input terminal, and an inverting input terminal; and connecting the first electrode of the semiconductor position detector to the inverting input terminal of the differential amplifier, A switching means for switching whether the first and second electrodes are connected to each other, and a resonator electrically resonating with respect to the predetermined frequency is provided between the output of the differential amplifier and the inverting input terminal. It was installed in.

[0012]

According to the present invention, a semiconductor position detector having first and second electrodes for receiving light including signal light modulated at a predetermined frequency and converting it into photoelectric conversion current, and a non-inverting input. A differential amplifier having a terminal and an inverting input terminal, the output of which is directly fed back to the inverting input terminal, and a first electrode of the semiconductor position detector is connected to a non-inverting input terminal of the differential amplifier. Or a switching means for switching between connecting the first and second electrodes in a connected state, and a resonator electrically resonating with respect to the predetermined frequency is a non-inverting input terminal of the differential amplifier. Since it is provided between the signal light and the ground, only the signal light modulated to a specific frequency can be selected and detected.

Further, in the present invention, the first and second
A semiconductor position detector for receiving light including signal light modulated at a predetermined frequency and converting it into a photoelectric conversion current, a grounded non-inverting input terminal, and a difference having an inverting input terminal. A dynamic amplifier and switching means for switching between connecting the first electrode of the semiconductor position detector to the inverting input terminal of the differential amplifier, or connecting the first and second electrodes to the inverting input terminal in a connected state, Since the resonator electrically resonating with respect to the predetermined frequency is provided between the output of the differential amplifier and the inverting input terminal, it is modulated to a specific frequency without being affected by the delay time of the differential amplifier. A detection output in which only the signal light is selected can be obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a block configuration of a photoelectric conversion circuit for a distance measuring device according to an embodiment of the present invention.
Reference numeral 0 denotes a PSD having first and second electrodes 201 and 202, which receives light including signal light modulated at a predetermined frequency and converts it into a photoelectric conversion current, and 10 applies a reverse bias to the PSD 20. Power source, 60 is a non-inverting input terminal 70,
An inverting input terminal 80, the output 90 of which is directly fed back to the inverting input terminal 80;
0 is a switch for switching between connecting the first electrode 201 of the PSD 20 to the non-inverting input terminal 70 of the differential amplifier 60 or connecting the first and second electrodes 201 and 202 in the connected state, and 50 is A parallel resonator provided between the non-inverting input terminal 70 of the differential amplifier 60 and the ground, electrically resonating with respect to the predetermined frequency, and converting only the photoelectric conversion current resonated by this resonance phenomenon into a voltage. is there. 1
Reference numeral 00 is a distance measurement detecting means having the switches 30, 40, the parallel resonator 50, and the differential amplifier 60.

Next, the operation will be described. The photocurrents output from the first anode 201 and the second anode 202 of the PSD 20 are switched to two states by the changeover switches 30 and 40 and extracted. First, set the switch 30 to O
N (closed), the switch 40 is turned off (open), the photocurrent from the first anode 201 is extracted, and the parallel resonator 50
The signal voltage from the first anode 201 is taken out via.

Next, the switch 30 is turned off (open),
The switch 40 is turned on (closed), and the first anode 201
And the second anode 202 are connected to each other, and a photocurrent is taken out and input to the non-inverting input terminal 70 of the differential amplifier 60 through the parallel resonator 50.
By inputting to the non-inverting input terminal 70 of 0, the total signal voltage from the first anode 201 and the second anode 202 is taken out.

Here, when the signal voltage from the first anode 201 is V ₁ and the signal voltage from the second anode 202 is V ₂ , it can be expressed by the following equation. V ₀₁ = V ₁ ...... (1) V ₀₂ = V ₁ + V ₂ ...... (2) V ₀₂ −V ₀₁ = V ₂ ...... (3)

Here, the output voltage of the differential amplifier 60 is V ₀₁
And V ₀₂ , switch 30 = ON and switch 40 =
Set the output voltage when OFF to V ₀₁ , switch 30 = OF
The output voltage when F and the switch 40 = ON is V ₀₂ . If the processing shown in the above equation (3) is added, V
₂ can be obtained and distance can be measured from the ratio of V ₁ and V ₂ .

Here, the impedance of the parallel resonator 50 becomes high resistance (several kΩ to several hundred kΩ) with respect to the current of a specific frequency, and the voltage drops. For currents other than the specific frequency, the resistance is low (tens of Ω to several hundreds Ω) and no voltage drop occurs. In this way, the current is converted into the voltage, and only the signal voltage can be taken out.

As described above, in this embodiment, the semiconductor position detector having the first and second electrodes and receiving the light including the signal light modulated at the predetermined frequency and converting the light into the photoelectric conversion current, A differential amplifier having a non-inverting input terminal and an inverting input terminal, the output of which is directly fed back to the inverting input terminal, and a first electrode of the semiconductor position detector connected to the non-inverting input of the differential amplifier. Switching means for switching between connecting to the terminal or connecting the first and second electrodes in a connected state, and a resonator electrically resonating with respect to the predetermined frequency is connected to the differential amplifier. Since it is connected between the inverting input terminal and the ground, only the signal light modulated to a specific frequency can be selected and detected, and a highly accurate photoelectric conversion circuit can be obtained. Also, using one operational amplifier, PS
Since the two anode currents from D can be impedance-converted, the Q characteristic of the parallel resonator can be improved, and the power consumption in the operational amplifier can be reduced as compared with the conventional one having two operational amplifiers.

In the above embodiment, the first anode 201 of the PSD 20 and the other end of the switch 40 (second anode 20
The photoelectric conversion circuit for the distance measuring device, which is configured by inserting the parallel resonator 50 between the parallel resonator 50 and the terminal (which is not connected to the second terminal), has been described as an example. Since it is used as an impedance converter to improve the Q characteristic of 50, and its output 90 is negatively fed back, the output voltage is output with a delay with respect to the input. Further, since the first anode 201 of the PSD 20 is connected to the non-inverting input terminal 70, the first anode 201 of the PSD 20 is
The voltages across the anode 201 and the second anode 202 are not at the same potential, so the shunt ratios of the PSD 20 are not equal.

Therefore, the photoelectric conversion circuit for the distance measuring device according to the second embodiment of the present invention in which the parallel resonator 50 is inserted between the inverting input terminal 80 and the output 90 of the differential amplifier 60 is shown. 2 shows. The non-inverting input terminal 70 of the differential amplifier 60 in this device is grounded and is always at ground potential. Also, the inverting input terminal 80 is always at the ground potential (characteristic of imaginary short circuit). That is, the differential amplifier 60 is P
First anode 201 and second anode 202 of SD20
PSD20 is to keep the voltage at both ends of the
The diversion ratios of are also equal and the accuracy can be improved. Also PSD2
The current from 0 does not pass through the differential amplifier 60, but the parallel resonator 5
Since it is output only through 0, there is no output delay time with respect to the input. Therefore, responsiveness is good,
It is suitable for signal light modulated at a high frequency.

As described above, the second embodiment has the first and second electrodes, the first and second electrodes, and receives the light including the signal light modulated at the predetermined frequency. A semiconductor position detector for converting into a photoelectric conversion current, a differential amplifier having a grounded non-inverting input terminal and an inverting input terminal, and a first electrode of the semiconductor position detector for inverting input of the differential amplifier. Switching means for switching between connecting to the terminal or connecting the first and second electrodes in a connected state, and a resonator electrically resonating with respect to the predetermined frequency is output from the differential amplifier. Since it is provided between the
For a distance measuring device that can improve the accuracy of 0, can obtain a detection output without being affected by the delay time of a differential amplifier, and has a good responsiveness to signal light modulated at a high frequency. A photoelectric conversion circuit can be obtained.

In each of the above-described embodiments, the output 90 of the differential amplifier 60 is configured to give negative feedback to the inverting input 80, whereby the input voltages of the inverting input 80 and the non-inverting input 70 are at the same potential. Since it works so that
The accuracy of the differential amplifier 60 in the standby state can be improved.

Further, in the above embodiment, as the operating power source of the differential amplifier, as shown in FIG.
00 and a minus-side power source 401 are required, but the differential amplifier 6 is required as in the third embodiment shown in FIG.
When the voltage source 300 is connected between one end of the resonator 50 on the side opposite to the non-inverting input terminal 70 of 0 and the ground, the differential amplifier 60 can be operated by a single power supply.

In the fourth embodiment shown in FIG. 4, the voltage source 3 is connected between the non-inverting input terminal 70 of the differential amplifier 60 and the ground.
00 is connected, and in this case as well, the differential amplifier 6
0 can be operated with a single power supply.

As described above, in the third and fourth embodiments, since the power source for operating the differential amplifier with a single power source is provided, the operating power source of the differential amplifier can be reduced.

Each of the switches 30 and 40 shown in FIGS. 1 to 4 in each of the above embodiments may be constituted by a semiconductor switch (for example, a transmission gate or an analog switch).

[0029]

As described above, according to the photoelectric conversion circuit for a distance measuring device of the present invention, it has the first and second electrodes,
It has a semiconductor position detector that receives light including signal light modulated at a predetermined frequency and converts it into photoelectric conversion current, a non-inverting input terminal, and an inverting input terminal, the output of which is to the inverting input terminal. Whether the differential amplifier that is directly fed back and whether the first electrode of the semiconductor position detector is connected to the non-inverting input terminal of the differential amplifier or whether it is connected to the first and second electrodes in a connected state A switching means for switching and a resonator electrically resonating with respect to the predetermined frequency are provided between the non-inverting input terminal of the differential amplifier and the ground, so that only the signal light modulated to a specific frequency is provided. It is possible to select and detect, and there is an effect that a highly accurate photoelectric conversion circuit can be obtained. Further, since two anode currents from the PSD can be impedance-converted by using one operational amplifier, it is possible to improve the Q characteristic of the parallel resonator and reduce the power consumption of the operational amplifier.

Further, according to the photoelectric conversion circuit for a distance measuring device of the present invention, it has the first and second electrodes and receives the light containing the signal light modulated at the predetermined frequency to receive the photoelectric conversion current. A semiconductor position detector for conversion into a differential position, a differential amplifier having a grounded non-inverting input terminal and an inverting input terminal, and a first electrode of the semiconductor position detector connected to the inverting input terminal of the differential amplifier. Or a switching means for switching whether the first and second electrodes are connected to each other, and a resonator electrically resonating with respect to the predetermined frequency is connected to the output of the differential amplifier and the inverting input terminal. Since it is provided between them, the PSD accuracy can be improved, an output can be obtained without being affected by the delay time of the differential amplifier, and the responsivity to the signal light modulated at a high frequency is excellent. Get a photoelectric conversion circuit for rangefinder There is an effect that can.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a block configuration of a photoelectric conversion circuit for a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a block configuration of a photoelectric conversion circuit for a distance measuring device according to another embodiment of the present invention.

FIG. 3 is a block circuit diagram in which a bias voltage is provided when the photoelectric conversion circuit for the distance measuring device shown in FIG. 1 is operated by a single power source.

FIG. 4 is a block circuit diagram in which a bias voltage is provided when the photoelectric conversion circuit for the distance measuring device shown in FIG. 2 is operated by a single power source.

FIG. 5 is a block circuit diagram showing a block configuration of a conventional photoelectric conversion circuit photoelectric conversion circuit for a distance measuring device.

FIG. 6 is a circuit diagram showing an electrode side of a PSD.

FIG. 7 is an equivalent circuit diagram showing an equivalent circuit of a differential amplifier.

[Explanation of symbols]

 10 PSD Reverse Bias Power Supply 20 Semiconductor Position Detector (PSD) 30 First Switch 40 Second Switch 50 Parallel Resonator 60 Differential Operation Amplifier 70 Non-Inverted Input Terminal 80 Inverted Input Terminal 90 Output 100, 101 Distance-Detecting Means 201 PSD first anode 202 PSD second anode 203 PSD cathode 300 Power supply for differential operation amplifier level shift 400, 401 Operation power supply for differential operation amplifier

Claims (4)

[Claims] 1. A semiconductor position detector having first and second electrodes for receiving light including signal light modulated at a predetermined frequency and converting the light into photoelectric conversion current, a non-inverting input terminal, A differential amplifier having an inverting input terminal, the output of which is directly fed back to the inverting input terminal; and a first electrode of the semiconductor position detector connected to a non-inverting input terminal of the differential amplifier, Switching means for switching whether the first and second electrodes are connected or not, and electrically resonating with respect to the predetermined frequency provided between the non-inverting input terminal of the differential amplifier and the ground. A photoelectric conversion circuit for a distance measuring device, comprising: a resonator. 2. The distance measuring device according to claim 1, wherein a single power source for operating the differential amplifier is provided between one end of the resonator opposite to the non-inverting input terminal and the ground. Photoelectric conversion circuit for equipment. 3. A semiconductor position detector having first and second electrodes, which receives light including signal light modulated at a predetermined frequency and converts it into a photoelectric conversion current, and a grounded non-inverting input. A differential amplifier having a terminal and an inverting input terminal, and connecting the first electrode of the semiconductor position detector to the inverting input terminal of the differential amplifier, or connecting it to the first and second electrodes in a connected state A distance measuring device including switching means for switching between ON and OFF, and a resonator provided between the output terminal and the inverting input terminal of the differential amplifier and electrically resonating with respect to the predetermined frequency. Photoelectric conversion circuit for equipment. 4. A photoelectric conversion circuit for a distance measuring device according to claim 3, wherein a single power supply for operating said differential amplifier is provided between a non-inverting input terminal of said differential amplifier and ground. ..