JPH0530697U - Ambient light countermeasure circuit - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a light beam type safety device, and particularly an object thereof is to provide a disturbance light countermeasure circuit for preventing the influence of disturbance light such as a satellite light. A light receiving signal detected by a light receiving element in the light receiving circuit 5 is output to a switch unit 8 via a capacitor 6 and an amplifier circuit 7. While the switch unit 8 is off based on the output of the synchronization signal, the switch unit is off. 9 is turned on to prevent output of a signal affected by unwanted ambient light to the amplifier circuit 7, and the switch unit 8 is turned on based on the synchronization signal only when the actual detection signal is output. By turning off 9, the output which is not affected by the ambient light is supplied to the control circuit.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an ambient light countermeasure circuit for preventing the influence of ambient light in a light beam safety device.

[0002]

[Prior Art]

 In recent years, light beam safety devices have been used in a wide range of industrial fields such as press machines and garbage trucks. This light beam safety device consists of a light emitting part, a light receiving part, and a control circuit, and when a human body or an object interrupts the optical axis created between the light emitting part and the light receiving part, the control circuit judges this and the machine immediately. It is a device to stop.

Such a light beam type safety device is configured, for example, as shown in FIG. The light receiving circuit 1 constituting the light receiving unit receives the light emitted from the light emitting unit (not shown), and outputs a light receiving signal based on the received light to the amplifier circuit 3 via the capacitor 2. The received light signal amplified to a constant level by the amplifier circuit 3 is output to a control circuit (not shown) via the switch unit 4. The switch section 4 is controlled to open and close by a synchronizing signal output in synchronization with the light emission of the light projecting section. If a light shield exists on the optical axis when the light emitting element emits light, the switch section 4 is turned on. Even in the state, since the light receiving signal is not output from the light receiving circuit 1, the detection signal is not output to the control circuit. Therefore, at this time, the control circuit judges that it is dangerous and stops the machine. On the other hand, if there is no obstacle on the optical axis, a light reception signal is output to the control circuit via the switch unit 4 in the ON state, and the machine continues to drive.

[0004]

[Problems of conventional technology]

 However, there are cases where various types of light emitters are provided around the machine in which the above-mentioned light beam safety device is installed. For example, this is a case where a so-called patrol light or the like is provided to call attention to the abnormal state of the machine or the drive of the machine. When such a light emitter is arranged around the light beam safety device, the light of a patrol light or the like enters the light receiving element as ambient light and adversely affects the operation of the safety device.

For example, when the light emitted from the satellite enters the light receiving element, the light receiving signal output from the light receiving circuit 1 shown in FIG. 3 is a pulse signal which is an actual light receiving signal as shown in (1) of FIG. In addition to a, a signal including a sinusoidal waveform signal b corresponding to the above-mentioned light of the satellite light is obtained. Then, the signal of (1) in the figure is amplified by the amplifier circuit 3 and output to the switch section 4. However, since the amplifier circuit 3 amplifies only the signal of a predetermined level or more, the amplifier circuit as shown in (2) of FIG. The pulse signal output from 3 is a pulse signal in which the low level signal in FIG. Therefore, even if the switch unit 4 is turned on by the timing when the synchronizing signal is output, for example, there is no pulse signal of the portion c shown in (2) of the figure, and the light receiving circuit 1 outputs the light receiving signal. Nevertheless, the received signal is deleted and the control circuit stops the machine.

The above-mentioned problems similarly occur when the camera flash or strobe flash is hit around the light beam safety device. Incidentally, in order to prevent the influence of the above-mentioned disturbance light, conventional measures have been taken such as providing a filter on the light-receiving element and shielding the circumference of the light-receiving element to prevent the incidence of disturbance light. However, the amount of light emitted from a light emitter such as a patrite is large, and since it includes a wide range of wavelength components, ambient light cannot be effectively eliminated.

[0007]

[The purpose of the device]

 The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a light beam safety device in which the influence of ambient light such as a satellite light is prevented.

[0008]

[Key points of the device]

 According to the present invention, a light receiving circuit for receiving light from a light emitting element and outputting a light receiving signal based on the received light, an amplifier circuit for amplifying a light receiving signal output from the light receiving circuit to a constant level, and The light receiving signal amplified by the amplifier circuit is output in synchronization with the light emission of the light emitting element, and the first switch section is controlled to open and close based on the synchronizing signal, and the light receiving signal output from the light receiving circuit is the synchronization signal. It is achieved by providing a disturbance light countermeasure circuit characterized in that it has a second switch portion which leads to a constant level during non-output.

[0009]

【Example】

 An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system block diagram in which the light beam type safety device of this embodiment is used. In the figure, this system relates to a light beam type safety device used in a machine installed in a factory, for example, a press machine. In the figure, the light receiving circuit 5 is provided in a light receiving section (not shown) and receives light emitted from a light projecting section (not shown). The light receiving circuit 5 includes a large number of light receiving elements and a circuit that outputs a detection signal when the light receiving elements receive light. Each of the light receiving elements forms an optical axis with the corresponding light emitting element provided in the light projecting section, and when each light receiving element detects the light of the light emitting element, the light receiving circuit 5 passes through the capacitor 6 and the amplifier circuit 7 The detection signal is output to. Here, the capacitor 6 is a capacitor for stabilizing the operation and removes a low frequency signal. However, there is no function to exclude even sinusoidal waves corresponding to ambient light such as a satellite light.

The amplifier circuit 7 amplifies the detection signal output from the light receiving circuit 5 via the capacitor 6 to a predetermined level, and outputs the amplified detection signal to a control circuit (not shown) via the switch section 8. The switch unit 8 is a so-called non-contact switch that is turned on / off by inputting / not inputting a synchronizing signal, and is turned on when the synchronizing signal is supplied and is off when the synchronizing signal is not supplied. The synchronization signal is a signal synchronized with the timing at which the light emitting element arranged in the light projecting portion emits light.

A switch unit 9 is connected between the connection point between the capacitor 6 and the amplifier circuit 7 and the ground, and a synchronization signal is output to the switch unit 9 via an inverter 10. Since the synchronization signal output to the switch unit 9 is output via the inverter 10, the switch unit 9 is turned on while the synchronization signal is not output and the synchronization signal is output, contrary to the switch unit 8. It turns off when it is on. Therefore, the detection signal output to the amplifier circuit 5 is guided to a constant level through the switch unit 9 while the synchronization signal is not output, and is output to the amplification circuit 7 only when the synchronization signal is output.

The operation of the light beam safety device having the above configuration will be described below. It is assumed that a patrol light is provided near the light beam safety device of this embodiment. First, when the light receiving elements in the light receiving circuit 5 sequentially detect the light of the corresponding light emitting elements, this detection signal is output from the light receiving circuit 5 to the capacitor 6. When the detection signal at this time is A, the detection signal A is in the signal state shown in (1) of FIG. The part of the sine wave b shown in the figure is caused by the light emission of the above-mentioned light incident on the light receiving element. In the case of the light, the light detected by the light receiving element is also periodic because it rotates at a constant cycle. The sine wave with a constant cycle is repeatedly obtained by repeating the dynamics. Further, a large number of pulse signals a having a shape of a sine wave b shown in the figure are signals output when the light of the light emitting elements which are sequentially turned on are detected by the corresponding light receiving elements. However, not all the pulse signals a are signals corresponding to the detection signals of the light receiving element, and other signals output from the light receiving circuit 5 are also included.

Next, the detection signal A output from the light receiving circuit 5 is output to the amplification circuit 7 and the switch unit 9 via the capacitor 6, and is synchronized with the light emission timing of the light emitting element as described above. Then, the synchronization signal is output, so the output timing of the synchronization signal output to the switch unit 9 via the inverter 10 is when the corresponding light emitting element is not emitting light. That is, the switch unit 9 is in the ON state while the output signal is not supplied from the corresponding light receiving element, and the output from the light receiving circuit 5 via the switch unit 9 is at a constant level during the period other than the time when the corresponding detection signal is output. Be led to. Therefore, the switch unit 9 is turned off only when the corresponding detection signal is output from the light receiving circuit 5, the detection signal is output to the amplifier circuit 7, and the signal that is not affected by the emission of the satellite light is output to the switch unit 8. The signal B in (2) of FIG. 2 is a diagram showing a signal supplied to the amplifier circuit 7 when the circuit of this embodiment is used.

A signal C in (3) of FIG. 2 is a diagram showing a signal state output from the amplifier circuit 7. That is, when the signal (2) in the figure is output to the amplifier circuit 5, the amplifier circuit 7 is not a signal affected by the satellite light, so the input level is a constant signal, and the detection signal input to the amplifier circuit 7 is Amplify without deleting. That is, the detection signal can be accurately amplified and output to the switch unit 8. Therefore, the switch section 8 can perform on / off control of the detection signal in accordance with the output of the synchronizing signal and perform accurate output to a control circuit (not shown). That is, the signal having the c portion as shown in the conventional example of (2) of FIG. 4 is not output, and if such a signal is included, there is some light shield on the optical axis, It is based on an accurate detection signal. Therefore, in this case, the control circuit can accurately execute the stop processing of the machine based on this signal.

As described above, according to the present embodiment, the synchronization signal output to the switch unit 8 is also output to the switch unit 9 via the inverter 10, so that signals other than the corresponding detection signals are switched. It leads to a constant level through the unit 9 and outputs only a necessary detection signal to the amplifier circuit 7. By processing in this way, the influence of ambient light due to the satellite is prevented.

Although the patrol light is described as the ambient light in the present embodiment, the present invention is not limited to the patrol light, and the same can be applied to other ambient light such as a camera flash and a strobe flash.

Further, in the present embodiment, the synchronization signal is output to the switch unit 9 through the inverter 10 and the switch unit 9 is turned on to guide the detection signal including the ambient light to a certain level. However, the present invention is not limited to the above configuration. Instead, the light receiving signal output from the light receiving circuit 5 may be brought to a constant level when the synchronizing signal is not output.

[0018]

[Effect of the device]

 As described in detail above, according to the present invention, since the unnecessary waveform due to the ambient light such as the patrol light included in the received light signal can be removed, it is possible to prevent the influence of the ambient light and output an accurate received light signal to the control circuit. You can

Further, since an accurate received light signal can be output to the control circuit, a reliable light beam safety device can be provided by using the disturbance light countermeasure circuit of the present invention.

[Brief description of drawings]

FIG. 1 is a system block diagram of an ambient light countermeasure circuit according to an embodiment.

FIG. 2 is a waveform diagram illustrating an operation of a disturbance light countermeasure circuit according to an embodiment.

FIG. 3 is a partial configuration diagram of a conventional light beam safety device.

FIG. 4 is a waveform diagram illustrating the operation of a conventional light beam safety device.

[Explanation of symbols]

 5 Light receiving circuit 6 Capacitor 7 Amplifying circuit 8, 9 Switch section 10 Inverter a Pulse signal b Sine wave

Claims (1)

[Scope of utility model registration request] 1. A light receiving circuit for receiving light from a light emitting element and outputting a light receiving signal based on the received light, an amplifier circuit for amplifying a light receiving signal output from the light receiving circuit to a constant level, and an amplifier circuit for amplifying the received light signal. A first switch section that is controlled to open and close based on a synchronization signal that outputs the received light receiving signal in synchronization with the light emission of the light emitting element, and a light receiving signal output from the light receiving circuit when the synchronization signal is not output. , A second switch section that leads to a certain level, and a disturbance light countermeasure circuit.