JP2000208012A - Object detection sensor - Google Patents

Abstract

(57) [Problem] To provide a conventional reflection-type object detection sensor using an object position detection technology based on a triangulation method, only convergent light or parallel light can be used as light to be used. Therefore, if there is a hole in the detected object, it is erroneously detected that there is no object. An object is irradiated with a plurality of light beams 16 and 17 from different directions, and the presence or absence of the object in a detection target area is determined based on a light amount level ratio of these scattered lights.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection sensor for optically detecting an object, and more particularly to a new reflection type object detection sensor based on a new principle.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a conventional reflection type object detection sensor and peripheral parts disclosed in Japanese Patent Application Laid-Open No. 59-139520. In the figure, 70 is a light emitting element, 71 is a light projecting lens, 72 is a light receiving element, 73 is a light receiving lens, 74 is a detected object at a point a, and 75 is a point b
Is a detected object at point c, and 76 is a detected object at point c.

Next, the operation will be described. Light emitting element 70
Is transmitted through the light projecting lens 71 and then reflected / scattered by the detected objects 74, 75, and 76, and a part of the scattered light is transmitted through the light receiving lens 73 and irradiated on the light receiving element 72. . Then, based on the light receiving position on the light receiving element 72, the distance to the detected objects 74, 75, 76 is calculated based on the principle of the triangulation method, and the detected objects 74, 75, 76 are detected (position detection). .

In this conventional object detection sensor, a position sensing device (PSD) or a two-segment photodiode (two-segment PD) is used as the light receiving element 72, and two light receiving signals obtained from these devices are used. , And a detection signal is output when the light amount level ratio exceeds a predetermined threshold value.

Therefore, even if there is an object other than the detected objects 74, 75, and 76 in the detectable area of the object detection sensor, the detection signal can be output by excluding the detected object. In addition, since the detection principle does not depend on the reflectivity of the object, detection is reliably performed even if the reflectivity is low within the detectable area, and no matter how high the reflectivity is outside the detectable area. False detection can be prevented.

[0006]

Since the conventional object detection sensor is configured as described above, the S / N of the detection position is determined.
In order to secure the ratio (accuracy), the detected objects 74, 75,
Since the parallel light and the convergent light are used so that the scattered light from the spot 76 is generated like a spot, the following problem occurs.

When parallel light or convergent light is used to increase the S / N ratio of the detection position, the light to be detected by the objects 74, 7
Since the irradiation area to the irradiation areas 5 and 76 is naturally small, the surface area of the detection objects 74, 75 and 76 in the irradiation area is easily affected. If the through holes 76 are provided, the light amount level ratio of the received light signal fluctuates greatly, and as a result, the detected objects 74, 75, 7
Despite the presence of 6, there is an erroneous determination that there is no object.

Therefore, the present invention has been made to solve the above-described problems, and it is possible to prevent erroneous detection of an object that is not the object to be detected outside the detection target area, and to reduce the surface shape of the object to be detected. An object of the present invention is to obtain an object detection sensor which is hardly affected.

[0009]

An object detection sensor according to the present invention receives light from a predetermined light receiving direction, and outputs a light receiving signal including light amount level information of the received light. Irradiates light with a part overlapping with 2
At least two or more light sources, control means for causing the two or more light sources to emit light in a time-division manner, and a light-receiving signal for each light source being output from the light-receiving means, And determining means for determining the presence or absence of the detection signal and outputting a detection signal.

In the object detection sensor according to the present invention, the judging means determines whether or not the object is present based on whether or not the light amount level ratio of the light receiving signal is within a range of the light amount level ratio of the light receiving signal according to the detection range of the object. Is to judge.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of an object detection sensor according to Embodiment 1 of the present invention. In the figure, 1 is a first light emitting diode (light source), 2 is a first driving circuit for supplying a light emitting current to the first light emitting diode 1, 3 is a second light emitting diode (light source), 4 is a second light emitting diode 3
A second driving circuit for supplying a light-emitting current to the light-receiving element, a photodiode (light-receiving means) for receiving light from a predetermined light-receiving direction and outputting a light-receiving signal having a level corresponding to the light level of the amount of received light, and 6 a light-receiving signal. , A sample-and-hold circuit 7 that samples and holds the amplified light receiving signal, 8 outputs a light emission control signal to the first drive circuit 2 and the second drive circuit 4, Control circuit (control means, determination means) for determining the presence or absence of an object based on the received light signal, 9
Are output display diodes that light up in response to object detection, 10
Is a detection state display diode that lights up when in a normal detection state, 11 is a switch for switching between the setting mode and the execution mode, 12 is an open collector transistor that outputs a detection signal when the control circuit 8 determines that an object is present, and 13 is Output terminal for outputting a detection signal.

FIG. 2A is a schematic diagram showing a relative positional relationship between two light emitting diodes 1 and 3 and a photodiode 5 of the object detection sensor according to Embodiment 1 of the present invention.
In the figure, 14 is a light projecting lens, 15 is a light receiving lens, 1
Reference numeral 6 denotes diffused light of the first light emitting diode 1 irradiated through the light projecting lens 14, 17 denotes diffused light of the second light emitting diode 3 irradiated through the light projecting lens 14, and 18 denotes a light receiving direction of the photodiode 5. It is. FIG. 2B is a characteristic diagram showing detection characteristics of the photodiode 5 according to the first embodiment of the present invention. In the figure, the horizontal axis is the distance to the detected object, the vertical axis is the received light level, 19 is the received light characteristic curve of the first light emitting diode 1, and 20 is the received light characteristic curve of the second light emitting diode 3.

The received light amount characteristic curves 19 and 20 indicate the amount of overlap between the diffused light 16 of the first light emitting diode 1 and the light receiving direction 18 and the amount of overlap between the diffused light 17 of the second light emitting diode 3 and the light receiving direction 18. The reason for not being proportional is that the light intensities of the light emitting diodes 1 and 3 are the strongest in the optical axis, and the light intensity decreases toward the periphery.

FIG. 3 is an explanatory diagram for explaining a change in the reflection state of the object according to the distance to the detected object according to the first embodiment of the present invention. 2, (a) is a reflection situation at a point a closest to the photodiode 5 in FIG. 2, (b) is a reflection situation at a point b, and (c) is a reflection situation at a point c farthest from the photodiode 5 in FIG. Reference numerals 21, 22, 23 denote light receiving spots at each point where the scattered light is received by the photodiode 5, reference numerals 24, 25, 26 denote first light emitting spots projected by the first light emitting diode 1 at each point, 2
Reference numerals 7, 28 and 29 denote second light-emitting spots projected by the second light-emitting diode 3 at each point.

FIG. 4 shows light receiving spots 21 and 2 at each of the points a, b and c according to the first embodiment of the present invention.
It is explanatory drawing which shows the light projection light intensity in 2 and 23. In the figure, 30, 31, and 32 indicate the light intensity of the first light emitting diode 1 at each point, and 33, 34, and 35 indicate the light intensity of the second light emitting diode 3 at each point.

Then, as in the example at these three points, each of the light projecting spots 24, 25, 26, 27, 28,
The brightest center position 29 moves relative to the light receiving spots 21, 22, 23 in accordance with the distance, and the intensity decreases in inverse proportion to the square of the distance. As a result, the detection characteristics of the light emitting diodes 1 and 3 are as shown in FIG.

FIG. 5 is a timing chart showing the operation of the control circuit 8 and the sample-hold circuit 7 according to the first embodiment of the present invention. In the figure, LED 1 is a light emission control signal to the first drive circuit 2, LED 2 is a light emission control signal to the second drive circuit 4, AMP is a light reception signal after amplification,
AMPLE & HOLD is a light reception signal after sample-hold, DATA1 is light reception signal data based on the diffused light 16 of the first light emitting diode 1, and DATA2 is light reception signal data based on the diffused light 17 of the second light emitting diode 3. As shown in the figure, in the first embodiment, the control circuit 8 alternately outputs a light emission control signal to each of the driving circuits 2 and 4, and the sample-and-hold circuit 7 synchronizes with the light emission control signal and amplifies the light emission control signal. Sample and hold the received light signal.

FIG. 6 is a flowchart showing the operation of the control circuit 8 according to Embodiment 1 of the present invention for judging the presence or absence of an object. In the figure, ST1 is DATA1 and DATA2.
Is a process start determination step for determining whether or not both are equal to or higher than a predetermined determinable reference level K. ST2 turns off the output display diode 9 and the detection state display diode 10 and outputs a detection signal output from the output terminal 13. This is a no-processing step to stop. ST3 is a detection lighting step for lighting the detection state display diode 10,
Numeral 4 is a light amount level ratio calculating step for calculating the light amount level ratio D of the light receiving signal based on the following equation 1. ST5 determines whether the light amount level ratio D of the light receiving signal is larger than a predetermined threshold value Dref. It is a detection determination step,
6 turns on the output display diode 9 and outputs 1
3 is a detection processing step for outputting a detection signal from
ST7 is a detection end processing step of turning off the output display diode 9 and stopping the output of the detection signal from the output terminal 13.

D = DATA1 / DATA2 (1)

FIG. 7 is a light intensity level ratio characteristic diagram of a light receiving signal for explaining a threshold setting state according to the first embodiment of the present invention. In the figure, the horizontal axis is the distance to the detected object, the vertical axis is the light intensity level ratio D of the received light signal, 36 is the light intensity level ratio characteristic curve of the received light signal, 37 is the boundary position of the detection target area, 38
Is the light amount level ratio D of the received light signal at the boundary position 37.
Is a threshold value Dref having the same magnitude as By setting the threshold value Dref in this way, the presence or absence of an object in the detection target area can be determined.

FIGS. 8 and 9 show a first embodiment of the present invention.
FIG. 11 is an explanatory diagram showing an application example (one example) in which an object detection sensor according to the present invention is applied to a distribution system. In the figure, 39 is a conveyor, 40 is a detected object conveyed by the conveyor 39, 41 is an object detection sensor, 42 is a white wall located behind the detection target area, and 43 is a light receiving spot 22 of the detected object 40. The through hole 44 located is a threshold setting plate. Then, as shown in the figure, for example, when the conveyor 39 is located between the point a and the point e in FIG. 7, a threshold setting plate 44 is temporarily provided at the position of the point e to set the threshold Dref.

As described above, the threshold value Dref is set to the light amount level ratio D of the light receiving signal at the point e (boundary position 37 of the detection target area).
, The white wall 4 with high reflectivity behind
Even if 2 exists, it is not erroneously detected as the detected object 40. Further, since the first light emitting diode 1 and the second light emitting diode 3 irradiate the diffused light 16 and 17, the light receiving spot 22 can be secured large, and the detection object 40 has the through hole 43, which is used for receiving light. Even if it is located in the spot 22, there is no erroneous determination that the detected object 40 does not exist.

As described above, according to the first embodiment, the photodiode (light receiving means) 5 which receives light from a predetermined light receiving direction and outputs a light receiving signal including light amount level information of the received light. A first light emitting diode (light source) 1 for irradiating light so that the light irradiation direction overlaps the light receiving direction
A second light emitting diode (light source) 3 for irradiating light in a section different from the first light emitting diode 1 so as to overlap the light receiving direction, and the two light emitting diodes 1 and 3
Are emitted one by one in a time-division manner.
A control circuit (control means, control means, (Determination means) 8, and the presence / absence of an object to be detected and its detection based on the light amount level ratio of the scattered light of the first light emitting diode 1 and the scattered light of the second light emitting diode 3 arranged at different positions. The distance (relative position) to the object is determined.

Because of this detection principle, the diameter of each spot on the detected object is ensured to be large, and is hardly affected by the surface shape of the detected object. Therefore, for example, even if a through-hole or the like is formed in the detected object and the light amount level of the received light greatly changes, the light amount level ratio of the received light signal, which is their ratio, hardly fluctuates. This has the effect of preventing erroneous determination that there is no object despite the presence of the detected object.

Furthermore, since the spot diameter on the detected object is large, even if the optical axes of the first light emitting diode 1, the second light emitting diode 3, and the photodiode 5 are slightly shifted, the first light emitting diode 1, the light emitting diode 1, The photodiode 5 can receive the scattered light of the light of the second light emitting diode 3 due to the object to be detected, without the need for fine optical axis adjustment as in the case of using parallel light or convergent light as in the related art. There are effects that can be used.

Embodiment 2 FIG. FIG. 10 is a schematic diagram showing a relative positional relationship between three light emitting diodes and a photodiode 5 of the object detection sensor according to Embodiment 2 of the present invention. In the figure, 45 is a first light emitting diode (light source),
46 is a first light projecting lens, 47 is diffused light of the first light emitting diode 45 irradiated through the first light projecting lens 46, 48
Is a second light emitting diode (light source), 49 is a second light emitting lens, 50 is diffused light of the second light emitting diode 48 irradiated through the second light emitting lens 49, 51 is a third light emitting diode (light source), Reference numeral 52 denotes a third light projecting lens, and 53 denotes diffused light of the third light emitting diode 51 irradiated through the third light projecting lens 52.

The received light signal data based on the diffused light 47 of the first light emitting diode 45 is DATA1, and the received light signal data based on the diffused light 50 of the second light emitting diode 48 is D.
When the ATA2 and the light receiving signal data based on the diffused light 53 of the third light emitting diode 51 are DATA3, the control circuit 8
Is DATA1 and DAT in the section from point a to point b.
A2 is used to perform a division operation to determine the presence or absence of an object, and the section from point b to point c is DATA2 and DA
A division operation is performed based on TA3 to determine the presence or absence of an object. Other configurations and operations are the same as those in the first embodiment, and a description thereof will be omitted.

As described above, three or more light emitting diodes 4
5, 48, and 51 are used to cover the detection area of the moving object, thereby maintaining the slope of the light amount level ratio D of the light receiving signals of the light emitting diodes (45 and 48, 48 and 51) of each set. Wide detection target area (point a
From the point c) to the object can be detected, and S / N
A wide area can be detected while maintaining the ratio.

Embodiment 3 FIG. 11 is a schematic diagram showing a relative positional relationship between two light emitting diodes and a photodiode of the object detection sensor according to Embodiment 3 of the present invention. In the figure, 54 is a first light emitting diode, 55 is a second light emitting diode, 56 is a photodiode, and 57 and 5.
8, 59, and 60 are first light-emitting spots projected by the first light-emitting diode 54 at points a, b, c, and e, respectively, and 61, 62, 63, and 64 are each point a,
In b, c, and e, the second light emitting spots projected by the second light emitting diode 55, and 65, 66, 67, and 68 are light receiving spots at points a, b, c, and e, respectively. Other configurations and operations are the same as those in the first embodiment, and a description thereof will be omitted.

Thus, the two light emitting diodes 54,
It is possible to detect the presence or absence of an object in the detection target area without arranging the 55 and the photodiode 56 on a straight line.

At the point c in FIG. 11, the light receiving level based on the diffused light of the first light emitting diode 54 becomes "0". Even in such a case, the light receiving level is detected in the processing start determining step ST1. Since the area is determined to be outside the target area, normal operation can be performed.

Embodiment 4 FIG. FIG. 12 is a flowchart showing an object presence / absence determination operation of the control circuit according to Embodiment 4 of the present invention. In the figure, ST8 is a detection determining step for determining whether or not the light amount level ratio D of the received light signal is smaller than the near threshold value Dref1 and larger than the far threshold value Dref2. ST10 is a second detection determination step for determining whether or not Dref1 or more. ST10 turns off the output display diode 9, stops the detection signal output from the output terminal 13, and further activates a warning alarm. This is a processing step.

FIG. 13 is an explanatory diagram showing an application example (an example) in which the object detection sensor 41 according to the fourth embodiment of the present invention is applied to a physical distribution system. And, as shown in FIG.
For example, the conveyor 39 arranges the threshold value setting plate 44 at the position of the point a in FIG. 7 to set the neighborhood threshold value Dref1, and sets the light amount level ratio Dback of the received light signal of the white wall 42 to “1.
A value multiplied by “1” is set as the far threshold Dref2. Other configurations and operations are the same as those in the first embodiment, and a description thereof will be omitted.

By setting the distant threshold value Dref2 on the basis of the light amount level ratio D of the received light signal of the white wall 42 as the background, the background located outside the detection target area in the installation environment is erroneously recognized as the detected object 40. This can be reliably prevented.

Since the near threshold value Dref1 is set together with the far threshold value Dref2, the person 69 is located between the object detection sensor 41 and the conveyor 39 as shown in FIG.
Even if such an object enters, the detected object 40 is erroneously detected.
And a warning can be issued in the second detection end processing step ST10, without impairing the detection capability of the detected object 40 on the conveyor 39, and causing a problem in optical detection. Obstacles on the route can be effectively distinguished, and the detection state can be maintained.

As described above, according to the fourth embodiment, the control circuit 8 determines that the light amount level ratio D of the received light signal is within the range (Dr) of the light amount level ratio of the received signal according to the detection range of the object.
ef1 to Dref2), the object 4
0, the presence or absence of the object 40 in the detection target area is determined.
And the object (person 69) outside the detection target area can be distinguished, and the detection signal can be output based only on the object 40 within the detection target area.

[0037]

As described above, according to the present invention, light receiving means for receiving light from a predetermined light receiving direction and outputting a light receiving signal including light amount level information of the received light, Two or more light sources for irradiating light so as to overlap with the light receiving direction in sections different from each other, and control means for causing the two or more light sources to emit light in a time division manner and outputting a light receiving signal for each light source from the light receiving means And determining means for determining the presence or absence of an object based on the light amount level ratio of the light receiving signal for each light source, and outputting a detection signal, wherein the light amount level ratio of the scattered light of each light source disposed at a different position is provided. The presence or absence of the detected object and the distance (relative position) to the detected object are determined based on the detected object.

Then, because of such a detection principle,
Even if the light emitted from the light source is used as diffused light,
/ N ratio (accuracy) can be ensured. Therefore, a large spot diameter on the object to be detected can be ensured by using the diffused light, so that the surface of the object to be detected is less affected by the shape of the object. In particular, through holes and the like are formed in the object to be detected. Even if the light intensity level of the received light greatly fluctuates, the light intensity level ratio of the received light signal, which is the ratio between them, hardly fluctuates, so that it is erroneously determined that there is no object despite the presence of the detected object. There is an effect that will not be done.

Also, since a large spot diameter on the detected object can be ensured, even if the optical axis of each light source or the light receiving means is slightly shifted, the scattered light of the light of each light source by the detected object is transmitted to the light receiving means. Light can be received and there is an effect that it can be used without fine adjustment of the optical axis as in the case of using parallel light or convergent light as in the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an object detection sensor according to Embodiment 1 of the present invention.

FIG. 2A is a schematic diagram showing a relative positional relationship between two light emitting diodes 1 and 3 and a photodiode 5 of the object detection sensor according to the first embodiment of the present invention, and shows detection characteristics of the photodiode 5; It is a characteristic figure (b).

FIG. 3 is an explanatory diagram for explaining a change in a reflection state of an object according to a distance to a detected object according to the first embodiment of the present invention;

FIG. 4 shows each of the points a,
It is explanatory drawing which shows the projection light intensity in the light receiving spot in b and c.

FIG. 5 is a timing chart showing an operation in the control circuit and the sample-hold circuit according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an object presence / absence determination operation of the control circuit according to the first embodiment of the present invention;

FIG. 7 is a light amount level ratio characteristic diagram of a light receiving signal for explaining a threshold value setting state according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an application example (one example) in which the object detection sensor according to the first embodiment of the present invention is applied to a physical distribution system.

FIG. 9 is an explanatory diagram showing an application example (one example) in which the object detection sensor according to the first embodiment of the present invention is applied to a physical distribution system.

FIG. 10 is a schematic diagram showing a relative positional relationship between three light emitting diodes and a photodiode of the object detection sensor according to Embodiment 2 of the present invention.

FIG. 11 is a schematic diagram showing a relative positional relationship between two light emitting diodes and a photodiode of an object detection sensor according to Embodiment 3 of the present invention.

FIG. 12 is a flowchart illustrating an object presence / absence determination operation of a control circuit according to Embodiment 4 of the present invention;

FIG. 13 is an explanatory diagram showing an application example (one example) in which the object detection sensor according to the fourth embodiment of the present invention is applied to a physical distribution system.

FIG. 14 is an explanatory diagram illustrating a state in which obstacles on an optical path are distinguished in the object detection sensor according to the fourth embodiment of the present invention.

FIG. 15 is a configuration diagram showing a conventional reflection-type object detection sensor and peripheral parts.

[Explanation of symbols]

 1, 45, 54 First light emitting diode (light source) 3, 48, 55 Second light emitting diode (light source) 5, 56 Photodiode (light receiving means) 8 Control circuit (control means, determination means) 51 Third light emitting diode (light source) )

Claims (2)

[Claims] 1. A light receiving means for receiving light from a predetermined light receiving direction and outputting a light receiving signal including light amount level information of the received light, and two light emitting units having a portion overlapping the light receiving direction. The light source described above, control means for causing the two or more light sources to emit light in a time-division manner, and a light receiving signal for each light source being output from the light receiving means, and an object based on a light amount level ratio of the light receiving signal for each light source. An object detection sensor, comprising: determination means for determining the presence or absence and outputting a detection signal. 2. The method according to claim 1, wherein the determining unit determines the presence or absence of the object based on whether or not the light amount level ratio of the light receiving signal is within a range of the light amount level ratio of the light receiving signal according to the detection range of the object. The object detection sensor according to claim 1.