JPS62179216A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To attain the response in the unit of microseconds and to miniaturize the circuit by setting a prescribed time by a counter and discriminating a signal incident before the set time elapses after a light reception signal is incident as a noise signal. CONSTITUTION:A pulse modulation light projected by a lighting means A is received by a photodetection means B to generate photodetection signals 1, 1'... the signals 1, 1'... are signals with a prescribed period and a photodetection signal 2 is a noise signal. When the photodetection signal 1 is inputted to a count means C, the state so far is reset and a pulse signal 3 is outputted after a preset time elapses. When the next photodetection signal 1' is inputted while the pulse signal 3 is outputted, a discrimination means D discriminates a signal as the signal incident at a prescribed period and gives an output signal 4 to a signal processing means E. When the noise signal 2 is inputted to the count means C before a prescribed time elapses after the incidence of the photodetection signal 1, the count means C resets the state so far the same as the processing of the photodetection signal 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used in various industries to perform position detection, shape inspection, etc. in place of human eyes. The present invention relates to a photoelectric switch that can distinguish between light incident signals of other photoelectric switches and prevent malfunctions caused by noise light caused by light incident signals of other photoelectric switches and continuous noise light.

[Conventional technology]

b) In a synchronous photoelectric switch, a light emitter emits pulse-modulated light, and the emitter and receiver are electrically connected with a cable or the like to transmit a synchronization signal, thereby eliminating light noise. We are trying to In other words, this technology introduces a synchronization signal synchronized with this pulse modulated light from the light emitting side to the light receiving side, and gates the light receiving side using this synchronization signal to extract only the pulse modulated light that has been emitted and removes other noise light. is adopted.

Also, as an asynchronous type technology that does not require electrical connection, an incoming light signal is integrated by an integrating circuit made up of elements such as resistors and capacitors, and output is output when the integrated output reaches a predetermined level. There is a technique that attempts to detect only continuously incident pulse modulated light by configuring it to generate a signal.

[Problem that the invention seeks to solve]

In the technology such as (a) above, an electrical connection is required between the light projecting section and the light receiving section in order to synchronize the light projecting section and the light receiving section. However, depending on problems such as the shape of the equipment and the installation environment, it is often impossible to install electrical wiring between the light projecting part and the light receiving part, and therefore there is a problem in that the conditions of use are limited.

In addition, although the technique (b) does not require an electrical connection between the light emitter and the light receiver, a relatively large time constant is required to stably generate an output signal. The response speed becomes slow, and there is no way to prevent noise light from continuously arriving, and it is impossible to arrange photoelectric switches side by side. In addition to the performance problems mentioned above, photoelectric switches are currently being used as the eyes of various industrial machines such as robots, so there is a need to make them as small as possible, which requires the use of capacitors and resistive elements with large time constants. It is difficult to create an integrated circuit if this method is used.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric switch that solves problems that cannot be solved with conventional photoelectric switches.

[Means for solving problems]

In order to achieve this object, the present invention will be explained with reference to FIG. 1, a conceptual diagram of the present invention, and FIG. 2, a timing chart showing the concept of the present invention. Light emitting means AIJ
...is generated. Light receiving means (11, (11'...
is a signal with a predetermined period, and the light reception signal (2) is a noise signal.

When the counting means C receives the light reception signal (1), it resets the previous state and outputs the pulse signal (3) after a predetermined time (set by the number of lock pulses).

When the next light reception signal (1)° is input while this pulse signal (3) is being output, the judgment means determines that it is a signal that comes in at a predetermined period, and outputs it to the signal processing means. Supply signal (4). Next, after receiving the light reception signal (1),
When the noise signal (2) is input to the counting means C before the predetermined time has elapsed, the counting means C resets the previous state in the same way as when it processed the light reception signal (1). In other words,
Since the pulse signal (3), which is the output signal of the counting means C, is reset before it is output, the pulse signal (3)
is not output. Next, when a light reception signal (1)" received at a predetermined period is input, the counting means C similarly resets the previous state and outputs a pulse signal (3)" after a predetermined period of time has elapsed. Judgment means is pulse signal (3)
If there is a signal that enters during the output of ``, this signal is determined to be a light reception signal of a predetermined period.

As described above, the present invention outputs a pulse signal after a predetermined period of time has elapsed after resetting the counting means C each time using a light reception signal, and the determination means uses this pulse signal to determine the signal received in a predetermined period.

〔Example〕

One embodiment of the present invention will be explained with reference to the circuit diagram in FIG. 3 and the timing chart in FIG. 4.

The photoelectric switch of this embodiment includes a light emitting means A, a light receiving means B,
It consists of a counting means C1, a determining means, and a signal processing means E.

The light emitting means A is composed of a pulse oscillator 1 that generates pulses of a constant period and a light emitting element 2 that emits pulse modulated light in accordance with the output pulses of the pulse oscillator 1.

The light receiving means B is a circuit that photoelectrically converts an incident light signal, amplifies the converted electric signal, binarizes it into a high level and a low level, and shapes the waveform to create a binarized signal.

Here, the pulse signal of the binary signal s is converted into the binary signal bl
, b2.

The counting means C includes an oscillation circuit 3 that generates a reference clock pulse a, and a synchronous monomulti-bibreak 4 that is composed of two stages of D-type flip-flops for detecting a received light signal based on the reference clock pulse a. Also based on the reference clock pulse a, synchronous monomultipipe rake 4
The signal C detected in is used as a reset input, the reference clock pulse a is counted by a predetermined number of clock pulses, and the signal d,
It consists of a counter 5 that outputs e. Here, the base number of counter 5 is not limited only to the example,
It is set appropriately according to the device.

The determining means includes a NOR gate 6 which inputs the inverted signal of the binary signal S and the output signal d of the counter 5, an output signal f of the NOR gate 6 as a clock input, and an output signal e of the counter 5 which is cleared. It consists of a flip-flop 7 which takes as an input and outputs a signal g.

The signal processing means E consists of an integrating circuit 8 and an output circuit 9,
The integrating circuit 8 counts the pulse signal g a required number of times and issues a signal indicating that it is receiving light.
There is a digital type that uses an actance element, and a linear type that uses an actance element, but this circuit uses a digital type because of its miniaturization and one-chip configuration. An output circuit 9 provides the output of the integrating circuit 8 as a signal corresponding to the control equipment.

The embodiment having the above configuration performs the operation shown in the timing chart of FIG. 4.

Here, the pulse signals received at a predetermined period are converted into binary signals bl, b2 . b3. b4. b5..., and a pulse signal which is a noise signal received at a period other than a predetermined period will be described as a binary signal b3.

The synchronous mono multivibrator 4 detects the binary signal bl at the falling edge h of the binary signal bl, is reset by the next input clock pulse a, and outputs the detection signal cl. The counter 5 is forcibly reset by this detected signal c1.

The synchronous mono multi-bi break 4 is in a state of waiting for the next incoming signal.

The reset counter 5 receives the clock pulse a
is counted a predetermined number of times, and a pulse signal d1 is output. This means that the falling edge h of the binary signal b1
This means that the binarized signal of the next light reception signal was not input to the synchronous mono multi-by-break 4 after the detection of the pulse signal d1. and,
While this pulse signal d1 is being output, the binarized signal b
2 is input, the NOR gate 6 which receives the pulse signal d1 and the inverted signal of the binary signal b2 outputs the signal f1.

This signal f1 is used as a clock input, the pulse signal e2 is used as a clock input, and the D input is always maintained at a high level.
The type flip-flop 7 latches the rising edge i of the signal f1 and outputs a high level pulse signal g. This pulse signal g is brought to a low level at the falling edge j of the signal e2.

In other words, this means that the light reception signal was received after a predetermined period of time (in the present invention, the time is set based on the number of clock pulses) after the light reception signal was received. In other words, it was confirmed that the light reception signal was received at a predetermined period.

Next, when the binary signal b3 which is a noise signal is input, the synchronous mono multi-by-break 4 detects the binary signal b3 in the same way as when the binary signal b2 was input. The detected pulse signal c3 is supplied to the reset input terminal of the counter 5, and the counting state of the counter 5 is reset. Therefore, the pulse signal d2 that is scheduled to be output based on the binary signal b2 is not output.

Further, the output state of the counter 5 is reset by the pulse signal c4 that detects the binary signal b4 that is input at a predetermined period. That is, since the counter 5 resets the current state before the pulse signal d3 is output, the pulse signal d3 is not output. Therefore, the output of NOR gate 6 is not inverted and flip-flop 7 maintains its current state.

That is, if the binary signal b3 is input before the predetermined time has elapsed, the determining means ignores the binary signal b4 that is scheduled to be input next.

The integrator circuit 8 counts the output signal g obtained as described above a predetermined number of times and outputs the resultant signal g, thereby outputting a signal to the output circuit 9 that indicates that the light reception signal with a constant period is continuously received.
The output circuit 9 sends signals suitable for control means of various industrial equipment. In other words, photoelectric switches serve as the eyes of various industrial equipment.

In the above embodiment, the synchronous mono multi-by-break detects the falling edge of the binary signal that is sequentially received for each incident light signal, and after forcibly resetting the counter with this detection signal, it waits for a predetermined time. After the elapsed time, a pulse signal is output, and by using this pulse signal to gate the next incoming binary signal, light is constantly received at a predetermined period (
Extracts only the signal that is present. That is, since all the signals that have entered the light are discriminated based on the time set by the counter, it is possible to extract only the periodic light signals that have entered the light.

〔Effect of the invention〕

In the present invention as described above, a predetermined time is set using a counter, and after a certain received light signal is received, a signal that comes in before the set time elapses is determined to be a noise signal, and a predetermined time is determined. It operates as a filter that extracts only the signals that enter the light periodically, and because it does not use elements such as capacitors and resistors, it is possible to respond in microsecond units, and it is also possible to miniaturize circuits, especially in recent years. By using semiconductor technology, it is possible to convert the entire circuit into an IC or IC. This also enables mass production and reduces costs. Furthermore, since it is possible to use the pulse modulated light of the light emitting means and the clock pulse of the light receiving system asynchronously, there is no need for wiring for synchronization, making the installation of the photoelectric switch extremely easy and making it suitable for any equipment. It has become possible to adapt to

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the concept of the present invention, and FIG. 2 is a block diagram showing the concept of the present invention.
FIG. 3 is a timing chart showing the concept of the present invention. FIG. 3 is a circuit diagram showing an embodiment of the present invention. FIG. 4 is a timing chart showing operational waveforms of the embodiment of the present invention. A: Light emitting means, B: Light receiving means, C: Counting means,
D: Judgment means, E: Signal processing means, 3: Oscillation circuit, 4: Synchronous monomultipipe rake, 5: Counter, 6: NOR gate, 7: D-type flip-flop, 8: Integrating circuit, 9: Output circuit .

Claims (1)

[Scope of Claims] 1) Light receiving means that receives pulse modulated light and generates a light reception signal; Counting means that is reset by the light reception signal and outputs a pulse signal after a predetermined time has elapsed after the reset; and the counting means 1. A photoelectric switch comprising: a determining means for determining, based on the pulse signal outputted by the pulse signal, whether the next signal that enters the light is a signal that has entered at a predetermined period or a noise signal.