JPH06281749A - Optical sensor for detecting object - Google Patents

Abstract

PURPOSE:To positively detect a person arriving at a reception position. CONSTITUTION:Light pulses from light emitting elements 11 and 12 are projected at approximately 30 deg. toward the front alternately, reflected light is received by a photodetector 16 between the light emitting elements 11 and 12, the light reception output Is compared with a threshold by a comparator 24, and then signals equal to or above the threshold are output as pulses. The output of the comparator 24 corresponding to the reflection light of the light pulses of the light emitting elements 11 and 12 is separated and then one of separated output is delayed by the phase difference between both pulses and is supplied to an AND circuit 27. On the other hand, the other is directly supplied to the AND circuit 27. Output from the AND circuit 27 indicates that a person arrived at a monitoring position 13. A detection range R1 of the monitoring position 13 is approximately 1/5 of the case where one light emitting element is used, thus preventing the person near the monitoring position 13 from being detected by mistake.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, to detect the arrival of a person before an unmanned reception, and projects light in a direction to be monitored so that the reflected light having a predetermined level or more is emitted. The present invention relates to an optical object detection sensor that detects an object in the direction to be monitored when receiving light.

[0002]

2. Description of the Related Art A conventional optical object or detection sensor projects light from one light emitting element in a direction to be monitored, receives the reflected light by a light receiving element, and converts it into an electric signal. When the electric signal exceeds a predetermined level, it is determined that an object exists in the direction to be monitored.

[0003]

In the conventional sensor, a light emitting element is arranged at a position about 70 cm above the ground, and a human body having a width of 30 cm as an object is separated from the light emitting element by about 75 cm in the direction to be monitored. The curve 10 of FIG. 3 shows the result of measuring the output of the light receiving element when it was moved horizontally at right angles to the direction to be performed. In FIG. 3, the horizontal axis represents the moving distance of the human body (object) and the vertical axis represents the output of the light receiving element. From the figure, when the output of the light receiving element is 1.2 V or more, the human body (object) is detected within a range of about 50 cm. Due to such a wide detection range, when used as a sensor for unmanned reception, for example, even if a person who does not actually come to the reception is near or above the detection range, reflected light from a part of the person There was a problem of making a wrong decision with the person who came to accept. In other words, the conventional one has a low resolution and thus has a low detection accuracy.

[0004]

According to the present invention, first,
A second light emitting element is provided, and the light projecting directions of these first and second light emitting elements are directed substantially to the positions to be monitored.
Slightly outwardly facing each other. One light receiving element is provided between the first and second light emitting elements, and by this light receiving element,
Each reflected light with respect to the projected light of the first and second light emitting elements is received. The first and second light emitting elements are alternately driven by the driving means, and the first and second light emitting elements are output from the output electric signal of the light receiving element.
The first and second reflected signals corresponding to the reflected light of the projected light of the second light emitting element are separated by the separating means, and the separated first and
A state in which both the second reflection signals are equal to or higher than a predetermined level is detected by the determination unit, and it is estimated that the detection output indicates that an object exists in the direction (position) to be monitored.

[0005]

FIG. 1 shows an embodiment of the present invention. In the present invention, first and second light emitting elements 11 and 12 are provided.
The first and second light emitting elements 11 and 12 are adapted to project light in the direction of the position (monitoring position) 13 to be monitored, and the respective directions of the projected light 14 and 15 are slightly outward. . A light emitting diode, a semiconductor laser, or the like is used as the first and second light emitting elements 11 and 12, and a directivity can be sharpened by using a lens such as a light projecting lens if necessary.

A light receiving element 16 is provided in the center of the first and second light emitting elements 11 and 12. The light receiving element 16 is a projection light 14,
The reflected light of 15 is received and converted into an electric signal, and a photodiode, a phototransistor or the like is used. The angle formed by the directions of the projected lights 14 and 15 is the monitoring position 13.
Both of the reflected lights from are detected by the light receiving element 16 at a predetermined level or higher. The first and second light emitting elements 11,
12 are alternately emitted. For example, a clock having a period T shown in FIG. 2a is generated from the clock generator 17, and the clock is divided in half by the pulse generator 18 and the phase is shifted by the period T in FIGS. 2b and 2c. It is assumed that there are two trains of pulses shown in FIG.
21 is supplied as a drive pulse to the first and second light emitting elements 11 and 12 by a period T to drive and emit light in a pulse manner in a period 2T. Frequency 250
An infrared light pulse with a duty ratio of 0.04 is emitted at Hz.

The electric signal from the light receiving element 16 is amplified by the amplifier 22 as needed, and the state that both the projection lights 14 and 15 are at a predetermined level is detected by the determination means 23 that the object is present at the monitoring position 13. In this example, the output of the amplifier 22 is compared with the threshold value by the comparator 24, the output of a predetermined level or more is output as a pulse, and the output of the comparator 24 is synchronized with the drive pulse by the distributor 25 and the projection light 14, 15 and a corresponding reflected light electric signal are separated, one of which is delayed by the delay device 26 for a time T, and its delayed output and the distributor 2
The other output of 5 is supplied to the AND circuit 27.

For example, if the output of amplifier 22 is as shown in FIG. 2d, the output of comparator 24 is as shown in FIG. 2e.
Inputs above the threshold will be pulsed and inputs below the threshold will not be pulsed. The output of the comparator 24 corresponding to each reflected light of the projected light 14 and 15 is separated by the distributor 25 as shown in FIGS. 2f and 2g, while the one corresponding to the projected light 14 is delayed by the delay device 26 in the figure. Figure 2
As shown in FIG. 2h, it is delayed by the time T, and the AND circuit 27 takes the logical product of the delayed output and the output of the comparator 24 corresponding to the projected light 15, and as shown in FIG.
An output is generated at the output terminal 28 when both the reflected lights of 4 and 15 are both above a predetermined level. This output is, for example, the display 29
It is displayed on the monitor that there is an object at the monitoring position, or is supplied to an alarm device and is audibly notified.

FIG. 3 shows the result of an experiment conducted on the embodiment shown in FIG. 1 under the same conditions as those of the conventional detection sensor shown in FIG. The distance between the first and second light emitting elements 11 and 12 is 5
cm, and the angle θ formed by the projection directions of the projection lights 14 and 15 was about 30 °. That is, the curve 10 is the light reception output characteristic of the reflected light with respect to the projection light 14 of the first light emitting element 11, and the curve 3
0 is the light reception output characteristic of the reflected light with respect to the projection light 15 of the second light emitting element 12. If the threshold value of the comparator 24 is 1.2 V as in the previous case, the curves 10 and 30 are both above a predetermined level, that is, the range R ₁ of the monitoring position 13 where the output from the AND circuit 27 is obtained is about 10 cm. , Conventionally about 5
It is about one-fifth as compared with the case of 0 cm.

Therefore, for example, when applied to a reception monitoring device, the left and right sides in front of the reception, in this example, around 75 cm
Only when there is a human center at 0 cm, it is detected that a person has come to the reception, but when it is out of this range, it is not detected that a person has come to the reception. Therefore, there is no possibility of detecting that a person has come near the left and right of the monitoring position 13 or has passed the vicinity thereof, that is, a person who is not the person who has come to the reception has come to the reception. First and second light emitting elements 11 and 12, light receiving element 16
In the case of a monitoring range of 50 cm at a monitoring position 13 of 100 cm further ahead, the angle formed by the projection direction θ = 2 tan ⁻¹ (25 /
100) ≈28 °. Therefore, it is preferable to set θ to about 24 ° to 34 °.

In FIG. 1, the output of the amplifier 22 is connected to the distributor 2
After separating by 5, the signals may be supplied to the AND circuit 27 without being passed through the delay device 26 and without being passed through the delay device 26 by detecting the predetermined level or more in each comparison. The first and second light emitting elements 11 and 12 may be driven alternately, and need not necessarily be shifted by a half cycle. Although the first and second light emitting elements 11 and 12 are arranged in the horizontal direction in the above description,
The third and fourth light emitting elements are also arranged in the vertical direction with the light receiving element 16 interposed therebetween, and these third and fourth light emitting elements are arranged in the first and second directions.
The light-emitting elements 11 and 12 are driven in a pulsed manner to emit light in a pulsed manner, and from the output of the comparator 24, those corresponding to the reflected light of the respective projected lights of the third and fourth light-emitting elements are separated, and both of them are combined. By detecting the state of the predetermined level, it is possible to detect the object in the two-dimensional range at the monitoring position 13, instead of the one-dimensional range. It should be noted that the output of the comparator 24 is taken out from the output terminal 31 as shown by the dotted line in FIG. 1, so that the range of the monitoring position 13 is R ₂ (about 90% in the example of FIG. 3).
cm) and can be widened than before.

The present invention is not limited to the above-described monitoring of desk reception, but also detection of an object in an industrial robot,
It is applicable to optical detection of objects in various other fields.

[0013]

As described above, according to the present invention, by using the two light emitting elements, the monitoring position range can be narrowed, that is, the resolution can be increased as compared with the prior art, and accordingly the detection accuracy ( The detection reliability is high. Moreover, since the light receiving element and the processing system for the output thereof are one system, the hardware configuration becomes simpler than the case where these are provided for each of the first and second light emitting elements and similarly detected. Further, since the first and second light emitting elements do not emit light at the same time, the reflected light of the projection lights 14 and 15 can be correctly detected without interference.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing signals of respective parts for explaining the operation of FIG.

FIG. 3 is a diagram showing received light output characteristics corresponding to projected light of each light emitting element when an object is moved in a direction perpendicular to the front.

Claims (1)

[Claims] 1. A first and a second light emitting element for projecting light toward a position to be monitored and slightly outwardly from each other, and a first and a second light emitting element provided between these first and second light emitting elements. One light receiving element that receives the reflected light from the object of the projected light of the second light emitting element and converts it into an electric signal, a driving means that alternately emits the first and second light emitting elements, and the light receiving element Separating means for separating the first and second reflected signals corresponding to the reflected lights of the respective lights of the first and second light emitting elements from the electric signal, and the separated first and second reflected signals are both predetermined. An optical object detection sensor, comprising means for detecting a state of being above a level as an object.