JPS6017254B2 - Photoelectric detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a photoelectric detection device.

The conventional photoelectric detection device of this type shown in FIG. Due to the response speed of the light receiving element, as shown in FIG. Comparing the received light signal shown in FIG. 2B which passes through the level discrimination circuit 6 via There was a problem. That is, as shown in FIG. 2c, the output of the level discrimination circuit 6 falls earlier by Δt than the falling edge of the modulated light signal to, so the next-stage flip-flop FF is set by the output of the level discrimination circuit 6. There was a problem when there were cases where this was not possible. The present invention has been made in view of the above-mentioned problems, and its purpose is to be able to reliably set flip-flops for signal processing, and to use the flip-flops to control the output of a level discrimination circuit. An object of the present invention is to provide a photoelectric detection device capable of enlarging a waveform. The present invention will be explained below with reference to Examples.

FIG. 3 shows a circuit according to an embodiment of the present invention, in which the light receiver 2 includes a light receiving circuit 3 consisting of a light receiving element such as a phototransistor, and an intensifier 5 which inputs the output of this light receiving circuit 3 and increases the intensity. and a level discrimination circuit 6 which discriminates the level of the intensified reception signal outputted from this intensifier 5 and shapes the waveform into a pulse signal of a predetermined level, and is set by the output of this level discrimination circuit 6, and the output is set for a certain period of time. A flip-flop FF that stretches, an integrating circuit 7 that inputs and integrates the output of the flip-flop FF, and a waveform shaping circuit 8 that shapes the integrated output of the integrating circuit 7 to a predetermined level and operates the output circuit 9 at the next stage. The output circuit 9 is composed of the output circuit 9 described above.

On the other hand, the light emitter 2 oscillates and outputs a pulse signal of a predetermined frequency, and the oscillation pulse signal causes the flip-flop F
an oscillation circuit 4 that resets F and drives a light-emitting circuit 10 made up of light-emitting elements; and a light-emitting circuit 10 that emits modulated light that is modulated by the oscillation pulse signal of the oscillation circuit 4.
It is composed of. The light-receiving circuit 3 and the light-emitting circuit 1 are placed opposite each other if they are of a projecting type, and are placed side by side if they are of a reflective type. By the way, the level discrimination circuit 6, which is the main component of the photoelectric detection device of the present invention, has a feedback circuit that lowers the reference voltage to a lower second level L when a received light signal that exceeds the reference voltage set at a higher first level L is input. It forms a loop and is composed of a specific circuit as shown in FIG. 4, for example. That is, when the level of the modulated light projected in response to the oscillation pulse of the oscillation circuit 4 shown in FIG. 5a is detected with the reference voltage of the first level L when the received light signal is as shown in FIG. 5b, the received,
Due to the positional relationship of the light emitting elements, etc., the fall of the output of the level discrimination circuit 6 falls within the duty of the corresponding oscillation pulse as shown in Figure 5c, and it becomes impossible to set the output of the level discrimination circuit 6. , it becomes impossible to extend the output pulse for a certain period of time, but as soon as the output of the amplifier OP that constitutes the level discrimination circuit 6 is generated, the transistor Tr is turned on and the resistor R3 of the voltage divider circuit for creating the reference voltage is turned on. Short-circuited by transistor Tr, resistor R,,
Since the low reference voltage divided by R2 is set, the detection level becomes L2, so the output of the level discrimination circuit 6 exceeds the duty of the oscillation pulse in FIG. 5a, as shown in FIG. 5d, and therefore The output of the flip-flop FF is held until it is reset by the next oscillation pulse, and the output is extended for a certain period of time. Of course, a reset-priority type FF is used as the chip FF. The present invention is configured as described above, and since the reference voltage for setting the detection level of the level discrimination circuit is lowered when the received light signal is input, the signal output from the level discrimination circuit is lower than the falling edge of the corresponding oscillation pulse. By having a delayed part, even the small signal shown in Figure 2 can be set reliably without lowering the reference level, and the output can be stretched for a certain period of time using a flip-flop, making it possible to set the signal without lowering the reference level. 4) The level of the received light signal is large due to a difference in the setting of the separation distance of the photoreceiver, and 4) Malfunction due to the output of the level discrimination circuit falling within the duty of the corresponding oscillation pulse due to the response speed of the phototransistor. Furthermore, since there is no need to lower the reference level, there is no need to lower the reference level, so there is also an effect that there is no influence from outside light noise.

[Brief explanation of drawings]

Figure 1 is a circuit block diagram of the main parts of the subordinate example, Figure 2a
, b, c are time charts for explaining the operation of the same as above, FIG. 3 is a circuit block diagram of an embodiment of the present invention, FIG. 4 is a circuit diagram of the main parts of the same as above, and FIGS. This is a time chart for explaining the operation. 1 is a light emitter, 2 is a light receiver, 3 is a light receiving circuit, 4 is an oscillation circuit, 6 is a bell discrimination circuit, 9 is an output circuit, 1 is a light emitting circuit, and FF is a flip-flop. It is. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 Emit modulated light from the light emitting circuit of the emitter that is pulse-modulated by the oscillation pulse output of the oscillator circuit, receive this modulated light by the light receiving circuit on the receiver side, and discriminate the level of this received light signal by the level discrimination circuit. The output of the level discrimination circuit is used as a set signal and the oscillation pulse output of the oscillation circuit is inputted as a reset signal.The output of the level discrimination circuit is extended for a certain period of time by a reset-priority flip-flop, and this extended signal is used to receive the modulated light. A photoelectric detection device that detects the interruption or entrance of light and activates an output circuit includes a switch means that is turned on by the detection output of a level discrimination circuit, and a first reference voltage for setting a detection level when the switch means is turned off. 1. A photoelectric detection device characterized in that the photoelectric detection device is provided with a reference voltage generating means which is switched to a second reference voltage lower than the reference voltage when the switch means is turned on and is applied to the level discrimination circuit.