JPS58156873A - Method for detecting object by reflective type sensor - Google Patents

Abstract

PURPOSE:To detect the presence of an object accurately under no influence of disturbing light and to eliminate malfunction, by flashing the light emitting element of a sensor and checking output signals of the photodetecting element in a turned-on and a turned-off state. CONSTITUTION:A switching element 7 is connected in series to the light emitting element 4 of the photoelectric sensor 3 and a signal of 1 or 0 is supplied to its input terminal (a) to flash and off the element 4. Then, the output of the element 4 in the turn-on state and that in the turn-off state are checked to detect the presence of a form 2. In this case, an element 5 sends out a photodetection signal by the lighting of the element 4; the presence of the form 2 is judged when the element 5 generates the photodetection signal during the turn-on operation of the element 3 and generates no signal during the turn-off operation, and the absence of the form is judged when the element 5 generats no signal during the turn-on operation of the element 4 and generates the signal during the turn-off operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the presence or absence of an object using a reflective photoelectric sensor, which method can reliably determine the presence or absence of an object to be detected without being affected by ambient light. This is what we are trying to provide.

When detecting the presence or absence of an object using a non-conforming photoelectric sensor, the influence of ambient light is always a problem, and the light-receiving element receives ambient light and detects the object even though the object is not actually there. An important technical issue is how to prevent it from being determined that something is present.

The conventional and common methods are to provide various types of light shielding plates and covers to prevent disturbance light from being projected onto the light receiving element, or to prevent unexpected disturbance light from occurring and causing malfunction of the light receiving element. There are also cases where it is not possible to effectively arrange a light shielding plate or the like. In such cases, conventionally, a light receiving element for detecting ambient light is separately provided in addition to the light receiving element of the reflective photoelectric sensor, and the output of this light receiving element for detecting ambient light is checked when detecting an object, thereby detecting the disturbance caused by the ambient light. This prevented sensor malfunction. However, if such a method is adopted, a light receiving element for disturbance light detection + Ii J41 and its output detection circuit are required separately, resulting in a total power consumption of 17 kl-
Since it is physically impossible to place the IE element at the same position as the light-receiving element of the reflective sensor, either one of the light-receiving elements When ambient light is projected only onto the element,
The problem remains that it is impossible to prevent malfunctions caused by this.

This invention was made to solve the problems of the conventional method, and involves blinking the light-emitting element of the reflective sensor when detecting an object, and changing the light-receiving element r when the light is turned on and when the light is turned off. By looking at the output signals of -, it is possible to accurately detect the presence or absence of an object.

In other words, the detection method of the present invention involves blinking the light emitting element of the sensor during an object detection operation, causing the light receiving element to emit a light reception signal when the light emitting element is turned on, and causing the light receiving element to emit a light reception signal when the light emitting element is turned off. It is determined that there is an object to be detected on the condition that the light-receiving element does not emit a light-receiving signal, and the light-receiving element does not emit a light-receiving signal when the light-emitting element is turned on, or the light-receiving element does not emit a light-receiving signal when the light-emitting element is turned off. The feature -3= is that it is determined that there is no object to be detected on the condition that the light emitting element emits light, and the light receiving element By looking at the output, it is possible to reliably detect the presence or absence of an object to be detected, regardless of the presence or absence of disturbance light. According to this method, there is no need to separately provide a sensor for detecting ambient light, and the object can be detected without being affected by any ambient light. Since the blinking time of the light-emitting element and the response time of the light-receiving element are on the order of milliseconds, the time delay caused by checking the output signal of the light-receiving element over time does not pose a problem in ordinary devices.

Hereinafter, further explanation will be given based on the embodiments shown in the drawings.

Figures 1 to 6 are diagrams showing the output status of a reflective photoelectric sensor depending on the presence or absence of a detection target and the presence or absence of disturbance light, Figure 7 is a diagram showing the signal detection circuit of the photoelectric sensor, and Figure 8 is a diagram showing the object. This is a flowchart showing an object detection routine, for example, in the case where a reflective photoelectric sensor is used to detect paper empty in an automatic paper feeder.

In Figures 1 to 6, 1 is a paper storage box, 2 is paper stored in this, 3 is a non-conforming photoelectric sensor that constitutes a paper empty switch, 4 is its light emitting element, and 5 is its light receiving element. , A indicates the projection light projected from the light emitting element, and B indicates the disturbance light. The numbers 1 and 0 shown near the input terminal a connected to the light emitting element 4 indicate the state of human power applied to the light emitting element 4. 1 indicates the state in which the light emitting element 4 is turned on, and 0 indicates the state in which the light emitting element 4 is lit. A state in which the light emitting element 4 is turned off is shown. In addition, the numbers 1 and 0 shown near the output terminal 1 connected to the light receiving element 5 indicate the output state of the light receiving element 5, and 1 indicates that the light receiving element 5 is outputting a light receiving signal. , 0 indicates that the light-receiving element 5 is not outputting a light-receiving signal.

As shown in FIGS. 1 and 2, when the paper storage box 1 is completely sealed by the cover 6 and there is no room for disturbance light to enter, the light receiving element 5 outputs the light while the light emitting element 4 remains lit. By looking at the signal, it is possible to reliably detect the presence or absence of the paper 2, but in reality, the paper storage box 1 must have an opening for sending out the paper 2, and the disturbance light B is transmitted through this opening. If the light enters the light receiving element 5, as shown in FIGS. 3 and 4, either the projected light A or the ambient light B is always received by the light receiving element 5, and the presence or absence of the paper 2 is detected. It becomes impossible to detect it.

However, if such disturbance light B exists, the light receiving element 5 will output a light reception signal even if the light emitting element 4 is turned off as shown in FIG. 6 if the paper 2 is not present. Furthermore, if a sheet of paper 2 is present, the disturbance light B is blocked by the sheet of paper 2 as shown in FIG. 5, and if the light emitting element 4 is turned off, the output of the light receiving element 5 is also extinguished.

Therefore, as shown in FIG. 7, a switching element 7 (the illustrated embodiment is an open collector type inverter) is connected in series with the light emitting element 4 of the photoelectric sensor 3, and a signal of 1 or 0 is applied to its input terminal a. The presence or absence of paper 2 is detected by blinking the light emitting element 4 and observing both the output of the light receiving element F5 when the light is turned on and the output of the light receiving element 5 when the light is turned off.

FIG. 8 is a flowchart 1 showing an example of this detection routine.
When the microprogram controlling the automatic paper feeder enters the paper empty detection routine, the first detection step 8 starts with detecting the output of the light receiving element 5 with the light emitting element 4 turned off. During this first detection step, the light-receiving element 5 outputs a light-receiving signal only in the state shown in FIG. to be transferred to

If the light-receiving element 5 does not output a light-receiving signal in the first detection step, the light-emitting element 4 is turned on, and after waiting for a time for a response, the second detection step 9 is entered. Light emitting element 4
In the second detection step in which the light is turned on, the light receiving element 5 does not output a light reception signal only in the case shown in FIG. 2, so it can be determined that the paper is empty also in this case. Since the paper in the state shown in FIG. 4 has already been rejected in the first detection step 8, if the light receiving element 5 outputs a light reception signal in the second detection step 9, the paper should be fed. Since paper 2 is present, the microprogram is moved to the next processing routine.

In the detection routine shown in FIG. 8, the output of the light receiving element 5 is first detected with the light emitting element 4 turned off, and then the output of the light receiving element 5 is detected with the light emitting element 4 turned on.
This procedure may be reversed, in which case the state shown in the second figure is first eliminated, and then the state shown in the sixth figure (and fourth figure) is eliminated. However, if you follow the procedure shown in Figure 8, it is better to turn on the light emitting element 4 once during the detection routine and wait for the sensor response time only when it turns on, so the detection time will be shorter. It only takes a long time, and compared to the case where the light emitting element 4 is constantly emitting light, there is an effect that the decrease in output due to changes in the light emitting element over time can be reduced.

As can be understood from the above description, according to the method of the present invention, it is possible to accurately detect the presence or absence of an object without being affected by ambient light, and a separate sensor for detecting ambient light is provided. Necessary, necessary or not (simply connecting the switching element to the light emitting element is sufficient, so there is no risk of increasing the cost of the device, and since the light receiving element of the sensor itself receives and mixes the disturbance light, the external disturbance It has an excellent feature that there is no possibility of malfunction occurring due to the position of light irradiation.

[BRIEF DESCRIPTION OF THE DRAWINGS] The figure shows an embodiment of the method of the present invention applied to a photoelectric sensor for paper empty detection. FIG. 7 is a diagram showing the output detection circuit of the photoelectric sensor, and FIG.
The figure is a flowchart showing the detection routine. In the figure, 1 is a paper storage box, 2 is paper, 3 is a reflective photoelectric sensor, 4 is a light emitting element, 5 is a light receiving element, 7 is a switching element, A is projected light, and B is disturbance light. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A method for detecting an object using a reflective photoelectric sensor, which includes blinking a light-emitting element during an object detection operation, causing the light-receiving element to emit a light reception signal when the light-emitting element is turned on, and It is determined that there is an object to be detected if the light-receiving element does not emit a light-receiving signal when the light is turned off, and if the light-receiving element does not emit a light-receiving signal when the light-emitting element is emitted, or the light-emitting element is turned off. A method for detecting an object using a reflective sensor, characterized in that it is determined that there is no object to be detected on the condition that a light receiving element emits a light reception signal when a light receiving element emits a light reception signal.