JPH04326024A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To enable the picking up of an electric signal alone selectively as obtained by photoelectric conversion of light energy with a specified frequency in a photoelectric conversion device. CONSTITUTION:A parallel resonator 11 which performs a frequency selection and a current-voltage conversion of a photoelectric conversion current with a photoelectric conversion element 1 is provided with a voltage limiter circuit 12 in parallel. Thus, a voltage alone by light with a specified frequency can be picked up selectively by the setting of a resonance frequency of the parallel resonator 11. Thus, also allows the limiting of a voltage generated by the parallel resonator 11 to a moderate level thereby enabling the prevention of malfunction, breakage of a circuit element and the like otherwise caused by the voltage generated by the parallel resonator 11 as it becomes excessive.

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 automatic focusing devices using light in cameras, distance measuring devices, remote control devices, communication devices, and the like.

0002

2. Description of the Related Art FIG. 11 is a wiring diagram of a conventional photoelectric conversion device, in which the cathode of a photoelectric conversion element 1 consisting of a photodiode is connected to the positive terminal of a DC voltage source 2, and the negative terminal of this DC voltage source 2 is connected to the positive terminal of a DC voltage source 2. A resistor 3 for current/voltage conversion is connected between the anode of the photoelectric conversion element 1 and the ground, and an amplifier 5 is connected between the anode of the photoelectric conversion element 1 and the output terminal 4.
is provided.

The photoelectric conversion current generated when the photoelectric conversion element 1 receives light flows to the ground through the photoelectric conversion element 1 and the resistor 3, and is converted into a current and a voltage by the voltage drop across the resistor 3. The voltage drop across the resistor 3 is amplified by the amplifier 5 and appears at the output terminal 4 as an output voltage.

At this time, since the photoelectric conversion element 1 is reverse biased by the DC voltage source 2, the depletion layer of the photoelectric conversion element 1 expands and the junction capacitance becomes smaller, resulting in better response and frequency characteristics. will improve.

[0005]

However, in the case of the conventional photoelectric conversion device described above, the photoelectric conversion element 1 converts all the received light energy into electric current, and the photoelectric conversion element 1
Since the photoelectric conversion current is converted into current and voltage by the resistor 3, light of various frequencies such as sunlight and artificial illumination light can be detected.

On the other hand, automatic focusing devices such as cameras, distance measuring devices, etc. emit signal light of a specific frequency that has been modulated in a predetermined manner from a light source, and then receive and detect the signal light reflected by an object. , automatic focusing, distance measurement, etc. are performed, but as mentioned above, conventional photoelectric conversion devices receive unnecessary light as well as signals of specific frequencies, making it difficult to extract only the desired signal light component. The problem was that it couldn't be done.

[0007] This invention was made to solve the above-mentioned problems, and its purpose is to make it possible to selectively extract only electrical signals obtained by photoelectrically converting optical energy of a specific frequency. do.

[0008]

[Means for Solving the Problems] A photoelectric conversion device according to the present invention includes a photoelectric conversion element that receives light and generates a photoelectric conversion current, and a parallel resonance device that performs frequency selection and current/voltage conversion of the photoelectric conversion current. and a voltage limiting circuit connected in parallel to the parallel resonator.

[0009]

[Operation] In this invention, a voltage limiting circuit is provided in parallel with the parallel resonator that performs frequency selection of photoelectric conversion current and current/voltage conversion by the photoelectric conversion element. Even when receiving light accompanied by miscellaneous external light, only the voltage due to light at a specific frequency is selectively extracted by setting the resonant frequency of the parallel resonator, and the voltage generated by the parallel resonator is limited to an appropriate level. This makes it possible to prevent malfunctions and damage to circuit elements due to excessive voltage generated by the parallel resonators.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a wiring diagram of a first embodiment of a photoelectric conversion device according to the present invention.

By the way, FIG. 2 is a wiring diagram of a photoelectric conversion device which is the background of the present invention, and instead of the resistor 3 in FIG. It is provided between the anode of No. 1 and ground, and constitutes a photoelectric conversion device.

[0012] When such a photoelectric conversion device is applied to an automatic focusing device of a camera, a distance measuring device, etc., the light source for the signal light may be one whose brightness increases or decreases at regular intervals, or one that turns on and off at regular intervals. By using a repeating device and making the period constant in this way, the intensity of brightness or the frequency of turning on and off becomes constant, and a signal light of a constant frequency is emitted from the light source.

At this time, the inductance of the coil 11a and the capacitance of the capacitor 11b are set so that the resonant frequency of the parallel resonator 11 is equal to the frequency of the signal light described above.

When the photoelectric conversion element 1 receives the signal light from the light source as well as various miscellaneous external lights containing various frequency components, a photoelectric conversion current by the photoelectric conversion element 1 flows through the parallel resonator 11. Since the resonant frequency of the parallel resonator 11 is set to the same value as the frequency of the signal light, the parallel resonator 11 has a high impedance with respect to the current component due to the signal light in the photoelectric conversion current, and current components other than the signal light The voltage drop across the parallel resonator 11 is extremely small with respect to current components other than the signal light, and no voltage is generated. A voltage is generated due to the voltage drop caused by 11, and is passed through the amplifier 5 to the output terminal 4.
An output voltage due to the current component of the signal light appears.

However, as mentioned above, the parallel resonator 1
1 has a high impedance for a current with the same frequency as its resonant frequency, and a low impedance for a current with a different frequency, and the impedance change at this time is determined by the Q of the parallel resonator 11. If it is large, the voltage between both ends of the parallel resonator 11 during resonance becomes a very large value, which may cause malfunction or damage to circuit elements.

Therefore, in the present invention, as shown in FIG. 1, a voltage limiting circuit 12 consisting of two diodes 12a and 12b whose anodes are connected to each other is connected in parallel to the parallel resonator 11.

In this way, by connecting the voltage limiting circuit 12 in parallel to the parallel resonator 11, the parallel resonator 11
In the case of FIG. 1, if the forward voltage of the diode is VF and the reverse breakdown voltage is BVR, the voltage limiting circuit 12 controls the parallel resonator 11. The generated voltage is VL (
=VF +BVR).

Therefore, since the voltage generated by the parallel resonator 11 can be appropriately limited by the voltage limiting circuit 12, it is possible to prevent malfunctions and damage to circuit elements due to excessive voltage generated by the parallel resonator 11. .

Next, FIGS. 3 to 10 are partial wiring diagrams of second to ninth embodiments of the present invention, which are modified examples of the voltage limiting circuit in FIG. 1.

In FIG. 3, a voltage limiting circuit 13 is constituted by two diodes 13a and 13b connected in parallel in opposite directions, and at this time, the voltage generated by the parallel resonator 11 is limited to VF. .

In FIG. 4, a voltage limiting circuit 14 is constituted by a resistor 14a and a diode 14b whose cathode is connected to the resistor 14a.If the voltage drop due to the resistor 14a is VR, then the voltage of the parallel resonator 11 is The generated voltage is VL1 (=VR +VF) or VL2 (=VR +
BVR).

Further, in FIG. 5, the voltage limiting circuit is composed of a resistor 15, and in FIG. 6, the voltage limiting circuit is composed of a diode 16. In the case of FIG. 5, the voltage generated by the parallel resonator 11 is V which is the voltage drop of the resistor 15
In the case of FIG. 6, the voltage generated by the parallel resonator 11 is limited to the forward voltage VF of the diode 16 or the reverse breakdown voltage BVR.

On the other hand, in FIG. 7, four diodes 17a, 17b, 17c, and 17d are provided, and diode 1
The voltage limiting circuit 17 is configured by connecting the anode of the diode 7a and the cathode of the diode 17b, connecting the anodes of the diodes 17b and 17c to each other, and connecting the cathode of the diode 17c and the anode of the diode 17d. The limiting circuit 17 limits the voltage generated by the parallel resonator 11 to VL (=2VF +2BVR).

Furthermore, in FIG. 8, a series circuit of three diodes 18a, 18b, 18c connected in the forward direction, and a series circuit of three diodes 18 similarly connected in the forward direction are shown.
A voltage limiting circuit 18 is constructed by connecting the series circuits d, 18e, and 18f in parallel in opposite directions, and at this time, the voltage generated by the parallel resonator 11 is limited to 3VF or 3BVR.

Further, as shown in FIG. 9, the voltage limiting circuit 19 may be configured by connecting the anodes of the diodes 18a and 18b and the cathodes of the diodes 18d and 18e in FIG. The voltage generated by the parallel resonator 11 is 3VF or 3 as in the case of FIG.
Limited to BVR.

Furthermore, in FIG. 10, an anti-parallel circuit of two diodes 20a and 20b connected in parallel in opposite directions, and two similar diodes 20c and 20d are shown.
A voltage limiting circuit 20 is constructed by connecting the anti-parallel circuit of
BVR +VR).

Therefore, in the second to ninth embodiments described above, the same effects as in the first embodiment can be obtained, and since each voltage limit value is different, the voltage limit value can be adjusted according to the level to be limited. Just select a voltage limiting circuit.

[0028] In the above embodiment, a case was explained in which a photodiode was used as a photoelectric conversion element, but the photoelectric conversion element is not limited to this, and may be a phototransistor, solar cell, or other device that generates superpower by light. That's fine.

Furthermore, FIGS. 1, 3, 6, 7, 8,
Although FIG. 9 shows an example of a combination of diodes, the number of diodes used and the number of connected stages may be appropriately selected depending on the set voltage to be limited.

[0030]

As described above, according to the present invention, since a voltage limiting circuit is provided in parallel to the parallel resonator that performs frequency selection of the photoelectric conversion current by the photoelectric conversion element and current/voltage conversion, the parallel resonator By setting the resonant frequency of the resonant frequency, it is possible to selectively extract only the voltage due to light of a specific frequency, and the voltage limiting circuit limits the voltage generated by the parallel resonator, thereby preventing the voltage generated by the parallel resonator from becoming excessive. This can prevent malfunctions and damage to circuit elements caused by
Suitable for automatic focusing devices, distance measuring devices, etc.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a first embodiment of a photoelectric conversion device of the present invention.

FIG. 2 is a wiring diagram of a photoelectric conversion device, which is the background of the present invention.

FIG. 3 is a partial wiring diagram of a second embodiment of the invention.

FIG. 4 is a partial wiring diagram of a third embodiment of the invention.

FIG. 5 is a partial wiring diagram of a fourth embodiment of the invention.

FIG. 6 is a partial wiring diagram of a fifth embodiment of the invention.

FIG. 7 is a partial wiring diagram of a sixth embodiment of the invention.

FIG. 8 is a partial wiring diagram of a seventh embodiment of the present invention.

FIG. 9 is a partial wiring diagram of an eighth embodiment of the invention.

FIG. 10 is a partial wiring diagram of a ninth embodiment of the present invention.

FIG. 11 is a wiring diagram of a conventional photoelectric conversion device.

[Explanation of symbols]

1 Photoelectric conversion element 11 Parallel resonator 12, 13, 14, 17, 18, 19, 20 Voltage limiting circuit 15 Resistor (voltage limiting circuit) 16 Diode (voltage limiting circuit)

Claims (1)

[Claims] 1. A photoelectric conversion element that receives light and generates a photoelectric conversion current, a parallel resonator that selects the frequency of the photoelectric conversion current and performs current/voltage conversion, and a parallel resonator that is connected in parallel to the parallel resonator. A photoelectric conversion device characterized by comprising a voltage limiting circuit.