JPH01282922A - Transmission type photoelectric switch - Google Patents

Abstract

PURPOSE:To apply self-diagnosis for a transmission type photoelectric switch by providing a photodetection circuit and its signal processing circuit to a projector side. CONSTITUTION:When an object passes by, a light radiated from a projection circuit 12 is shut by the object, and when the object does not reside between a projector 10 and a photodetector 30, the light from the projector 10 is received by the photodetector 30 to detect the presence of the object. Then the photodetection circuit 13 in the projector 10 receives a reflection light in the object when the object passes by and an amplifier 14 detects the light. If the output of a detection circuit 15 is decreased due to the deterioration in a light projection element of the projection circuit 12, the output of a window comparator 16 is increased and the output of an integration circuit 18 is gradually increased. When the output exceeds a threshold value of a Schmitt circuit 19, an output is obtained from an output circuit 20 to recognize the deterioration in the projection level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a transmission type photoelectric switch, and more particularly to a transmission type photoelectric switch characterized by a self-diagnosis function of an optical system.

[Prior art]

Conventional transmission type photoelectric switches are always shown in Figure 3 (a), (bl
As shown in FIG. 1, light from a light projector 1 is applied to a light receiver 2, and an object 3 between the light projectors and the receiver is detected by the light blocking state in between. In addition, as shown in Fig. 3, the output from the emitter 1 is sent to the receiver 2 when no object is detected.
If the received light level falls below a predetermined value, it is detected that the object is in an unstable state where the object cannot be stably detected due to factors such as deterioration of the light emitting/receiving element or fogging of the lens of the light emitting/receiving device. , a so-called self-diagnosis function is provided.

[Problem to be solved by the invention]

However, as shown in FIG. 3(C), when the object 3 passes continuously between the emitter and receiver 1.2 and a transmission type photoelectric switch is used to detect the interruption, the light emitter 1. The self-diagnosis function could not be operated because the irradiated light was blocked by the object 3. Therefore, if the light intensity from the projector 1 becomes weak for some reason, unstable output due to self-diagnosis cannot be output to the outside. Another problem is that in order to perform self-diagnosis, it is necessary to ensure that no object exists between the light emitting and receiving parts.

The present invention has been made in view of the problems of the conventional transmission type photoelectric switch, and is aimed at ensuring that light is emitted from the projector even when the light from the projector is always blocked by an object. The technical challenge is to make it possible to detect

[Structure and effects of the invention]

(Means for Solving the Problems) The present invention includes a light projector having a light projecting circuit that includes a light projecting element and drives the light projecting element, and a light receiving element provided at a position facing the projector to detect the level of received light. A transmission type photoelectric switch that detects an object between the emitter and the receiver by cutting off the output of the light receiving circuit, the light emitter having a light receiving circuit that obtains a signal from the light emitting circuit. a second light receiving circuit including a light receiving element that receives light, a window comparator that discriminates a predetermined range of the light receiving output obtained from the second light receiving circuit, and a fault that detects an unstable operating state based on the output of the window comparator. The device is characterized in that it has a stable operation detection means.

(Function) According to the present invention having such characteristics, the light from the projector is irradiated onto the receiver placed at the opposite position, and the object is detected by the intermittent light, and when the object passes, the light inside the projector is detected. The reflected light is also given to a light-receiving circuit including a light-receiving element located at. The reflected light level is then amplified, and a received light signal within a predetermined level range is detected by a window comparator and provided as an input signal to an integrating circuit.

Therefore, if the received light level of the light receiving circuit in the emitter decreases and the received light level remains within the range determined by the window comparator, the integrated output will increase, and if the output exceeds a predetermined level, an unstable operating state will be output. That will happen.

(Effects of the Invention) Therefore, according to the present invention, the attenuation of the light emitting output can be detected even in a transmission type photoelectric switch in which a detection object is always present between the emitter and the receiver and detects the state when the detection object is absent. It is possible to detect a lack of light intensity.In addition, since the reflected light is used to determine the light incident state, there is no need to create a state where there is no object to detect in order to operate the self-diagnosis function.
This also has the effect of making self-diagnosis easier.

[Explanation of Examples]

FIG. 1 is a block diagram showing the configuration of a transmission type photoelectric switch according to an embodiment of the present invention. The light projector 10 also has an oscillation circuit 11 in this embodiment, and a light projecting circuit 12 having a light projecting element is intermittently driven to irradiate the object detection area.

The light projector 10 is also provided with a light receiving circuit 13 including a light receiving element that receives reflected light from the light projecting element. The output of the light receiving circuit 13 is given to a detection circuit 15 via an amplifier circuit 14. The detection circuit 15 converts an intermittently driven oscillation signal into a continuous signal, and its output is given to a window comparator 16. The window comparator 16 receives the first signal from the level setter 17. Second threshold Vref
l+Vref2 is set, and an output is given to the integrating circuit 18 when it falls within the range of these dark values.

Integrating circuit 18 integrates the signal and provides its output to Schmitt circuit 19. Schmitt circuit 1
A predetermined threshold value V ref3 is set at 9, the integrated signal is discriminated by this dark value, and its output is provided to the output circuit 20 and the display circuit 21. The output circuit 20 outputs an unstable state, and its output can be directly outputted to the outside as an unstable output, or can be outputted to the outside via the delay circuit 22. Here, the integrating circuit 18.
The Schmitt circuit 19 constitutes an unstable operation detection means for detecting an unstable operation state based on the output of the window comparator 16.

Now, as shown in FIG. 3(d), a light receiver 30 is provided at a position facing the light projector 10. The light receiver 30 is provided with a light receiving circuit 31 having a light receiving element at a position facing the light projecting element of the light projecting circuit 12 . The output of the light receiving circuit 31 is given to a detection circuit 33 via an amplifier circuit 32. The detection circuit 33 converts the light reception output of the optical signal projected intermittently into a continuous signal, and the output is given to the comparison circuit 34. A certain darkness value level is set in the comparison circuit 34, and when this level is exceeded, the output circuit 35
And an object detection output is given to the display circuit 36.

Next, the operation of this embodiment will be explained with reference to time charts. FIG. 2(a) is a diagram showing the presence or absence of an object between the light emitter and receiver, and when an object passes, the light emitter circuit 12
If there is no object between the emitter and receiver 10 and 30, the light emitted from the emitter 10 will be directly transmitted to the receiver 30, so a light reception signal can be obtained from the light receiving circuit 31 on the receiver 30 side. object is detected. Further, when an object passes, the light receiving circuit 13 in the projector 10 receives reflected light, and the signal is amplified and detected by the amplifier 14. Therefore, as shown in FIG. 2 (bl), a detection signal is obtained while the object passes.
During Vref2, a signal as shown in FIG. 2 (C1) is obtained from the window comparator 16. This signal is then applied to the integrating circuit 18, and an output as shown in FIG. As shown after time 1g in Fig. 2 (bl), when the detection output obtained by the detection circuit 15 decreases due to deterioration of the light emitting element of the light emitting circuit 12 or clouding of the focusing lens attached to the front surface of the light emitting element, Figure 2 (
As shown in C), the output of the window comparator 16 increases. Since the output is given to the integrating circuit 18, the integrated output gradually increases as shown after time t2 in FIG. 2(d). When the object passes continuously as shown in Figure 3 (d+), the detection output hardly changes and the integral output increases due to the output from the window comparator 16.Then, the output of the integrating circuit 18 increases and the Schmitt If the threshold value Vref3 set in the circuit 19 is exceeded, an output indicating deterioration of the light projection level is obtained from the output circuit 20 as shown in FIG. Similar outputs can be obtained.Therefore, in the present invention, by providing a light receiving circuit and its signal processing circuit on the projector side, the object can be used not only when the object passes intermittently, but also when the object passes continuously and under normal conditions. Now, even a transmission type photoelectric switch used in an environment where the light receiver is hardly irradiated with light can be made into a photoelectric switch having a self-diagnosis function.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of a transmission type photoelectric switch according to the present invention, Fig. 2 is a time chart showing its operation, and Fig. 3 is a diagram showing the relationship between the light emitter/receiver and the detection object passing between them. be. L, LO----- Floodlight 2, 20...--
Photoreceiver 3---Detection object 11--Oscillating circuit 12--Emitting circuit 13.31...-Receiving circuit 15゜33--Detecting circuit 16----
・Window comparator 17---Level setter 18---Integrator circuit 20------
- Output circuit patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Yoshiki Okamoto (and one other person) Figure 2 Figure 3 (a) (b) (C) ((1)

Claims (1)

[Claims] (1) A light projector having a light projecting circuit including a light projecting element and driving the light projecting element, and a light receiving circuit including a light receiving element provided at a position facing the light projecting device and obtaining a signal for detecting the level of the received light. A transmission type photoelectric switch that detects an object between the light emitter and the receiver by blocking the output of the light receiving circuit, the light transmitting device including a light receiving element that receives reflected light from the light projecting circuit. a second light receiving circuit; a window comparator that discriminates a predetermined range of light receiving output obtained from the second light receiving circuit; and unstable operation detection means that detects an unstable operating state based on the output of the window comparator. A transmission type photoelectric switch characterized by having the following.