JPH02148775A - Optical sensor - Google Patents

Abstract

PURPOSE:To reduce connecting positions, to improve reliability and to decrease its cost by providing a light emitting element, a photodetector connected in series with the element, and a resistor connected in parallel with the photodetector. CONSTITUTION:Since a current from a light emitting diode 11 flows in series with a resistor 15 and a resistor 22 in a state that a light from the diode 11 docs not enter a photo-transistor 12, it becomes relatively small, and the voltage V1 of a terminal A becomes V1=[(V00-VF)/(R15+R22)]XR22, where VCC is the voltage of a DC power source 21, VF is the forward drop voltage of the diode 11, R15 is the resistance value of the resistor 15, and R22 is the resistance value of the resistor R22. When the light of the diode 11 enters the phototransistor 12, the phototransistor 12 can be sufficiently saturated by suitably selecting the resistance values of the resistors 15, 22. The voltage V2 of the terminal A in this case becomes V2=VCC-VF-Fsat, where Fsat is the collector-emitter saturated voltage of the phototransistor 12.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an optical sensor.

[Conventional technology]

Conventionally, in the configuration of a photointerrupter, lead wires are provided separately for an LED on a light emitting side and a phototransistor on a light receiving side.

[Problem to be solved by the invention]

Therefore, four or at least three lead wires must be drawn out.

[Means to solve the problem]

According to the present invention, an optical sensor comprising a light-emitting element, a light-receiving element connected in series with the light-emitting element, and a resistor connected in parallel with the light-receiving element is obtained.

〔Example〕

Next, the present invention will be described in more detail with reference to the drawings showing one embodiment of the present invention.

Referring to FIG. 1, in one embodiment of the invention, a light emitting diode 11 and a phototransistor 12 are connected in series. Furthermore, a resistor 15 is connected in parallel between the collector and emitter of the phototransistor 12. The light emitted from the light emitting diode 11 enters the entrance hole 14 from the exit hole 13 of the case 10 of the optical sensor, and hits the phototransistor 12 .

FIG. 2 shows an example of a detection circuit using the optical sensor of this embodiment, in which the positive terminal of the DC power supply 21 is connected to the terminal 16 of the sensor, the negative terminal is connected to the ground, and the sensor terminal 18 is connected to the ground. A resistor 22 is connected.

In this circuit, when the light emitted from the light emitting diode 11 does not hit the phototransistor 12, the current of the light emitting diode flows through the resistor 15 and the resistor 22 in series, so it becomes a relatively small current, and the current at the terminal A is voltage v
1 is as follows: VCC: Voltage VP of DC power supply 21; Forward drop voltage R1 of binary photodiode 11;: Resistance value of resistor 15; R22: Resistance value of resistor 22.

Also, the light emitted from the light emitting diode is transmitted to the phototransistor 1.
2, by appropriately selecting the resistance values of the resistor 15 and the resistor 22, the phototransistor 12
It can be set so that it is fully saturated, and the voltage V2 of terminal A at that time is V 2 = V CC - V
p −V matVaat: Phototransistor 1
The collector-emitter saturation voltage is 2.

FIG. 3 shows the positional relationship between the output voltage and the shutter that blocks light in the circuit example of FIG. 2, and shows the output V1 when the light is not blocked and the output V2 when the light is blocked.

Although this embodiment uses a light emitting diode and a phototransistor, similar results can be obtained by using other light emitting sources such as lamps or photosensitive elements such as CDS.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to configure the optical sensor with two lead wires, reducing the number of connection points such as connectors and soldering, which is effective in improving reliability and reducing costs. There is.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an optical sensor according to an embodiment of the present invention, Figure 2 is a circuit diagram of an example of a detection circuit according to this embodiment, and Figure 3 shows the output voltage characteristics of the detection circuit shown in Figure 2. FIG. 10... Case, 11... Light emitting diode, 12.
... Phototransistor, 13... Output hole, 14...
・Incidence hole, 15...Resistance, 16.18...Terminal, 2
0...DC power supply, 22...Resistor. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] An optical sensor comprising: a light-emitting element; a light-receiving element connected in series with the light-emitting element; and a resistor connected in parallel with the light-receiving element.