JP6967955B2 - Distance setting type photoelectric sensor - Google Patents

Description

The present invention relates to a distance setting type photoelectric sensor that determines the presence or absence of an object based on a distance based on the principle of triangular distance measurement.

In a conventional photoelectric sensor, the number of peaks is detected by obtaining the distribution of the amount of light received by the light receiving element, and the presence or absence of glossy reflected light is determined (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2007-221491

In a photoelectric sensor (hereinafter referred to as a distance setting type photoelectric sensor) that determines the presence or absence of an object based on the distance to the detector 10 by the principle of triangular distance measurement, for example, as shown in FIG. 6, the light received by the detector 10 is received. The presence or absence of the detector 10 is determined based on the light receiving position (the position of the center of gravity of the light receiving distribution) on the element 22. In the distance setting type photoelectric sensor, when the set distance is B (the position of the distance b), the detector 10 is present when the distance to the detector 10 is closer to the distance setting type photoelectric sensor than the distance b. Judgment is made, and it is determined that there is no detector 10 when the distance c is farther from the distance setting type photoelectric sensor than the distance b. In the distance setting type photoelectric sensor shown in FIG. 6, reference numeral 11 indicates a light emitting element, reference numeral 12 indicates a light projecting lens, and reference numeral 21 indicates a light receiving lens.

The relationship between the distance to the detector 10 and the light receiving position of the reflected light on the light receiving element 22 shown in FIG. 6 is established when the light reflected by the detector 10 is diffuse reflected light. Therefore, when the reflected light by the detector 10 is glossy reflected light, the above relationship does not hold.

For example, when the detection body 10 is a blank sheet or the like and the light reflected by the detection body 10 has only diffuse reflection light, the set distance B ≈ detection range D as shown in FIG. 7A.
On the other hand, when the detector 10 is a SUS plate or the like and the reflected light by the detector 10 has glossy reflected light in addition to diffuse reflected light, the set distance B ≠ detection range D'as shown in FIG. 7B. The detectable range (detection range D') may be narrower than the set distance B. In this case, the distance setting type photoelectric sensor may erroneously determine that the detector 10 is within the set distance B but there is no object due to the glossy reflected light.

FIG. 8 is a diagram showing a case where the light reflected by the detector 10 has diffuse reflected light 101 and glossy reflected light 102a and 102b in the conventional distance setting type photoelectric sensor, and FIG. 8A shows the case where the detector 10 is not tilted. A case is shown, and FIG. 8B is a diagram showing a case where the detector 10 is tilted.
In FIG. 8, the glossy reflected light 102a is the reflected light of the central portion of the light that hits the detection body 10 from the light emitting element 11. Further, the glossy reflected light 102b is the reflected light of the peripheral portion of the light that hits the detection body 10 from the light emitting element 11. Further, the light in the central portion of the light that hits the detector 10 is stronger than the light in the peripheral portion. Therefore, the glossy reflected light 102a has a stronger intensity than the glossy reflected light 102b.

As shown in FIG. 8B, when the detector 10 has an inclination θ, the glossy reflected light 102b is incident on the light receiving element 22 at a position deviated from the light receiving position of the diffuse reflected light 101. Further, the glossy reflected light 102b has a weaker intensity than the glossy reflected light 102a, but the glossy reflected light 102b is very strong light with respect to the diffuse reflected light 101. Therefore, when the glossy reflected light 102b deviates from the light receiving position of the diffuse reflected light 101 and is incident on the Far side of the light receiving element 22, the distance setting type photoelectric sensor does not have the detector 10 where it should be originally determined that the detector 10 is present. Will be misjudged.
When the light reflected by the detector 10 has only the diffuse reflected light 101, as shown in FIG. 9, the position of the distance b does not change even when the detector 10 has the inclination θ (distance b = distance b'). ..

In the distance setting type photoelectric sensor, the operation on the side closer to the set distance B is particularly important in determining the presence or absence of the detector 10. This is because, for example, when detecting an object flowing on a conveyor, the side farther than the set distance is the background, and the side closer to the set distance is the detector 10. The background can be dealt with by providing a non-glossy wall or the like, but since the detector 10 is made of various materials and may have a glossy component, it is important to operate on the near side. Therefore, when the reflected light by the detector 10 includes the glossy reflected light, it is required to reduce the influence thereof and widen the detection range D'.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a distance setting type photoelectric sensor capable of reducing the influence of glossy reflected light even if the reflected light by the detector includes glossy reflected light. There is.

The distance setting type photoelectric sensor according to the present invention has a light projecting unit that emits light, an N-side light receiving surface capable of receiving diffuse reflected light by the detector when the detector is located closer than the set distance, and a light receiving surface on the N side. It has an F-side light receiving surface that can receive diffusely reflected light by the detector when the detector is located farther than the set distance, and a light receiving part that receives light and a light receiving position of the light received by the light receiving part. It is provided with a position determination unit for determining the presence / absence of a detector, an intensity determination unit for determining the light reception intensity of the light received by the light receiving unit, and a presence / absence determination unit for determining the presence / absence of a detector from the determination results of the position determination unit and the intensity determination unit. , The presence / absence determination unit determines that there is a detector when the position determination unit determines that the light receiving position is the N-side light receiving surface, and after determining that there is a detector, the position determination unit sets the light receiving position to F. When it is determined that the light receiving surface is on the side and the light receiving intensity is determined by the intensity determining unit, it is determined that there is a detector .

According to the present invention, since it is configured as described above, even when the reflected light by the detector includes the glossy reflected light, its influence can be reduced.

It is a figure which shows the structural example of the distance setting type photoelectric sensor which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the relationship between the light-receiving position on a light-receiving element and the distance to a detection body in Embodiment 1 of this invention. It is a figure which shows the structural example of the determination part in Embodiment 1 of this invention. It is a figure which shows the state transition of the determination in the presence / absence determination part in Embodiment 1 of this invention. 5A and 5B are diagrams showing the effect of the distance setting type photoelectric sensor according to the first embodiment of the present invention (when the reflected light by the detector has diffuse reflected light and glossy reflected light), and FIG. 5A is a diagram. It is a figure which shows the relationship between the set distance and the detection range in the conventional distance setting type photoelectric sensor, and FIG. 5B is a figure which shows the relationship between the set distance and the detection range in the distance setting type photoelectric sensor which concerns on Embodiment 1. .. It is a figure which shows the operation example of the conventional distance setting type photoelectric sensor. 7A and 7B are diagrams showing the relationship between the set distance and the detection range in the conventional distance setting type photoelectric sensor, and FIG. 7A is a diagram showing the case where the reflected light by the detector has only the diffuse reflected light. FIG. 7B is a diagram showing a case where the reflected light by the detector has diffuse reflected light and glossy reflected light. 8A and 8B are diagrams showing an example of a conventional distance setting type photoelectric sensor in which the reflected light by the detector has diffuse reflected light and glossy reflected light, and FIG. 8A shows a case where the detector is not tilted. 8B is a diagram showing a case where the detector is tilted. 9A and 9B are diagrams showing a case where the light reflected by the detector has only diffuse reflected light in the conventional distance setting type photoelectric sensor, and FIG. 9A shows a case where the detector is not tilted, and FIG. 9B is shown. Is a diagram showing the case where the detector is tilted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a distance setting type photoelectric sensor according to the first embodiment of the present invention.
The distance setting type photoelectric sensor uses the principle of triangular distance measurement to determine the presence or absence of the detector 10 in the detection region. Further, the distance setting type photoelectric sensor has a function of reducing the influence of the glossy reflected light by utilizing the fact that the glossy reflected light is very strong with respect to the diffuse reflected light. As shown in FIG. 1, the distance setting type photoelectric sensor includes a light emitting unit 1, a light receiving unit 2, and a determination unit 3. The light emitting unit 1 has a light emitting element 11 and a light emitting lens 12, and the light receiving unit 2 has a light receiving lens 21 and a light receiving element 22.

The light emitting element 11 emits light.
The light projecting lens 12 projects the light emitted by the light emitting element 11 to the outside. The projection lens 12 is arranged to face the detection region, and the light emitted by the light emitting element 11 is projected onto the detection region.

The light receiving lens 21 collects light. The light receiving lens 21 is arranged to face the detection area and collects light from the detection area.
The light receiving element 22 receives the light collected by the light receiving lens 21. The light receiving element 22 has an N side light receiving surface (Near side) and an F side light receiving surface (Far side), and is electrically separated by adjusting the distance. The method of electrically separating the N-side light-receiving surface and the F-side light-receiving surface of the light-receiving element 22 is described in, for example, Patent Document 2, and the description thereof will be omitted.
The N-side light receiving surface can receive diffusely reflected light by the detector 10 when the detector 10 is located closer than the set distance. Further, the F-side light receiving surface can receive the diffuse reflected light by the detector 10 when the detector 10 is located farther than the set distance. As the light receiving element 22, a multi-divided photodiode such as a two-divided photodiode or a position detection element can be used.
Patent No. 2933804

FIG. 2 shows the relationship between the light receiving position on the light receiving element 22 and the distance from the distance setting type photoelectric sensor to the detector 10. It is assumed that the reflected light has only diffuse reflected light.
As shown in FIG. 2, when the distance to the detector 10 is the distance b (set distance B), the reflected light by the detector 10 is the N-side light receiving surface (PD_Near) and the F-side light receiving surface (PD_Far). Light is received during. When the distance to the detector 10 is closer to the distance setting type photoelectric sensor than the distance b, the reflected light from the detector 10 is received by the N-side light receiving surface. When the distance to the detector 10 is a distance c farther from the distance setting type photoelectric sensor than the distance b, the reflected light by the detector 10 is received by the light receiving surface on the F side.

The determination unit 3 determines the presence / absence of the detector 10 in the detection region based on the light reception result by the light receiving unit 2. As shown in FIG. 3, the determination unit 3 has a position determination unit 31, a strength determination unit 32, and a presence / absence determination unit 33. The determination unit 3 is realized by a processing circuit such as a system LSI, a CPU or the like that executes a program stored in a memory or the like.

The position determination unit 31 determines the light receiving position of the light received by the light receiving unit 2 (light receiving element 22). At this time, in the position determination unit 31, the difference value obtained by the difference between the signal I_Near indicating the light received on the N-side light receiving surface and the signal I_Far indicating the light received on the F-side light receiving surface is the threshold value A1 (first). It is determined whether it is larger than the threshold value (I_Near-I_Far> A1). The threshold value A1 is a threshold value for position determination, and is set to a level at which the distance setting type photoelectric sensor does not chatter due to circuit noise. Then, when the position determination unit 31 determines that the difference value is larger than the threshold value A1, it determines that the light receiving position is the N side light receiving surface. On the other hand, when the position determination unit 31 determines that the difference value is equal to or less than the threshold value A1, it determines that the light receiving position is the F side light receiving surface.

The intensity determination unit 32 determines the light receiving intensity of the light received by the light receiving unit 2 (light receiving element 22). At this time, in the intensity determination unit 32, the sum of the signal I_Near indicating the light received on the N-side light receiving surface and the signal I_Far indicating the light received on the F-side light receiving surface is the threshold value A2 (second). It is determined whether it is larger than the threshold value) (I_Near + I_Far> A2). The threshold value A2 is a threshold value for gloss detection, and is set to a level at which it can be determined whether or not the light is affected by the gloss reflected light. Then, when the intensity determination unit 32 determines that the added value is larger than the threshold value A2, it determines that the light receiving intensity is strong (the light includes glossy reflected light). On the other hand, when the intensity determination unit 32 determines that the added value is equal to or less than the threshold value A2, it determines that the light receiving intensity is weak (the light does not include the glossy reflected light).

The presence / absence determination unit 33 determines the presence / absence of the detection body 10 from the determination results of the position determination unit 31 and the strength determination unit 32. Here, the presence / absence determination unit 33 determines that the detector 10 is present when the position determination unit 31 determines that the light receiving position is the N-side light receiving surface. Further, after the presence / absence determination unit 33 determines that the detector 10 is present, the position determination unit 31 determines that the light receiving position is the F-side light receiving surface, and the intensity determination unit 32 determines that the light receiving intensity is strong. If so, it is determined that the detector 10 is present. Further, after the presence / absence determination unit 33 determines that the detection body 10 is present, the position determination unit 31 determines that the light receiving position is the F-side light receiving surface, and the intensity determination unit 32 determines that the light receiving intensity is weak. If so, it is determined that the detector 10 is absent. FIG. 4 shows a state transition diagram of the determination in the presence / absence determination unit 33.

Next, the effect of the distance setting type photoelectric sensor according to the first embodiment will be described with reference to FIG. Note that FIG. 5A is the same as FIG. 7B.
In the conventional distance setting type photoelectric sensor, as shown in FIG. 5A, there is a range (DX1) within the set distance B where there is a possibility of malfunction or erroneous detection due to glossy reflected light.

On the other hand, in the distance setting type photoelectric sensor according to the first embodiment, the intensity determination unit 32 determines the light reception intensity of the light received by the light receiving unit 2, and the presence / absence determination unit 33 considers the determination result to determine the detector body 10. Is determined. As a result, even if the position determination unit 31 determines that the light receiving position is the F side light receiving surface after the presence / absence determination unit 33 determines that the detector 10 is present, the intensity determination unit 32 determines that the light receiving intensity is strong. If it is determined, the presence / absence determination of the detector 10 is maintained. As a result, as shown in FIG. 5B, the range (DX1') that is within the set distance B but may malfunction or be erroneously detected due to the glossy reflected light can be narrowed with respect to the DX1 and the distance can be detected normally. Range (detection range D'') can be extended with respect to the detection range D'. For example, when the set distance B = 400 mm, the detection range D ″ in FIG. 5A is 250 mm, but the detection range D ″ in FIG. 5B can be 300 mm.

As described above, according to the first embodiment, the light emitting unit 1 that emits light, the light receiving unit 2 that has the N side light receiving surface and the F side light receiving surface and receives light, and the light receiving unit 2 From the determination results of the position determination unit 31 that determines the light receiving position of the light received by the light receiving unit 2, the intensity determination unit 32 that determines the light receiving intensity of the light received by the light receiving unit 2, and the position determination unit 31 and the intensity determination unit 32. Since the presence / absence determination unit 33 for determining the presence / absence of the detection body 10 is provided, even if the reflected light by the detection body 10 includes the glossy reflected light, the influence thereof can be reduced.

In the above, the case where the threshold value A2 used by the strength determination unit 32 is single is shown. However, the present invention is not limited to this, and a plurality of threshold values A2 used by the strength determination unit 32 may be provided. For example, the strength determination unit 32 may provide a plurality of threshold values A2 according to the set distance B. Further, the intensity determination unit 32 may be provided with a plurality of threshold values A2 according to the light amount level of the diffusely reflected light.

Further, in the above, the case where the threshold value A2 used by the strength determination unit 32 is a fixed value is shown. However, the present invention is not limited to this, and the threshold value A2 used by the strength determination unit 32 may be a variable value. For example, the strength determination unit 32 may change the threshold value A2 according to the set distance B. Further, the intensity determination unit 32 may change the threshold value A2 according to the light amount level of the diffusely reflected light.

In the present invention, within the scope of the invention, it is possible to modify any component of the embodiment or omit any component of the embodiment.

1 Light-emitting unit 2 Light-receiving unit 3 Judgment unit 10 Detector 11 Light-emitting element 12 Light-emitting lens 21 Light-receiving lens 22 Light-receiving element 31 Position determination unit 32 Strength determination unit 33 Presence / absence determination unit

Claims (7)

The floodlight section that casts light and
When the detector is located closer than the set distance, the N-side light receiving surface capable of receiving the diffuse reflected light by the detector and when the detector is located farther than the set distance, the diffuse reflected light by the detector is emitted. A light receiving part having an F side light receiving surface capable of receiving light and receiving light,
A position determination unit that determines the light receiving position of the light received by the light receiving unit, and a position determination unit.
An intensity determination unit that determines the light reception intensity of the light received by the light receiving unit,
It is provided with a presence / absence determination unit for determining the presence / absence of a detector from the determination result by the position determination unit and the strength determination unit.
The presence / absence determination unit determines that there is a detector when the position determination unit determines that the light receiving position is the N-side light receiving surface, determines that there is a detector, and then receives light from the position determination unit. position is determined to be the F-side light-receiving surface, and the intensity when the determining unit by the light-receiving intensity is determined to be strong, distance setting type photoelectric you characterized by determining a detector is present Sensor . The floodlight section that casts light and
When the detector is located closer than the set distance, the N-side light receiving surface capable of receiving the diffuse reflected light by the detector and when the detector is located farther than the set distance, the diffuse reflected light by the detector is emitted. A light receiving part having an F side light receiving surface capable of receiving light and receiving light,
A position determination unit that determines the light receiving position of the light received by the light receiving unit, and a position determination unit.
An intensity determination unit that determines the light reception intensity of the light received by the light receiving unit,
It is provided with a presence / absence determination unit for determining the presence / absence of a detector from the determination result by the position determination unit and the strength determination unit.
The presence / absence determination unit determines that there is a detector when the position determination unit determines that the light receiving position is the N-side light receiving surface, determines that there is a detector, and then receives light from the position determination unit. position is determined to be the F-side light-receiving surface, and the intensity when it is determined that the received light intensity is weak the determination unit is distance setting type photoelectric you wherein the determining that there is no detector Sensor . The position determination unit receives light when the difference value obtained by subtracting the signal indicating the light received on the F side light receiving surface from the signal indicating the light received on the N side light receiving surface is larger than the first threshold value. Claim 1 is characterized in that it is determined that the position is the N-side light receiving surface, and when the difference value is equal to or less than the first threshold value, it is determined that the light receiving position is the F side light receiving surface. Alternatively, the distance setting type photoelectric sensor according to claim 2. The intensity determination unit receives light intensity when the sum of the signal indicating the light received on the N-side light receiving surface and the signal indicating the light received on the F-side light receiving surface is larger than the second threshold value. The invention according to any one of claims 1 to 3 , wherein is determined to be strong, and when the added value is equal to or less than the second threshold value, it is determined that the light receiving intensity is weak. Distance setting type photoelectric sensor . The distance setting type photoelectric sensor according to claim 4 , wherein a plurality of the second threshold values are provided. The distance setting type photoelectric sensor according to claim 4 , wherein the second threshold value is a variable value. When the presence / absence determination unit determines that the detector is present, the position determination unit determines that the light receiving position is the F-side light receiving surface, and the intensity determination unit determines that the light receiving intensity is weak. , the distance setting type photoelectric sensor according to claim 1, wherein the determining that there is no detector.

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