JPH0627867B2 - Reflective photoelectric switch - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reflective photoelectric switch used for automatic door opening / closing control and the like.

[Conventional technology]

A sensor using a pyroelectric element has been conventionally used as a human body detection sensor in opening / closing control of an automatic door. This detects the intrusion of the human body by detecting the temperature change when the human body enters the detection area.

On the other hand, Japanese Unexamined Patent Publication No. 52-135779 and Japanese Unexamined Patent Publication No. 61-
Japanese Patent No. 233386 discloses a reflection method in which a plurality of light beams are projected from a light emitting element and the reflected light is detected by a photodiode or a semiconductor light position detection element to detect an object or a human body in a certain detection area. Is disclosed.

[Problems to be Solved by the Invention]

The former pyroelectric method is a moving object detection method that detects a temperature change within a predetermined time in a detection area, and can detect an object (human body) in a certain wide range, but has the following problems. First, the human body invades the detection area,
Therefore, if it remains stationary for a predetermined time or longer, it becomes impossible to detect it. Secondly, unlike a human body having a heat source, when an object having the same ambient temperature as a trolley enters the detection area, it cannot be detected. Third, if a mat that absorbs sunlight is installed in the detection area, it will have heat, so
If the wind blows there, the temperature of the mat changes within a predetermined time, which causes malfunction.

Further, the latter sensor in the reflection direction can solve the above-mentioned problems of the pyroelectric method, but has the following problems. First, in Japanese Unexamined Patent Publication No. 52-135779, since an intrusion of an object is detected due to a decrease in the level of light received by the light receiving element when the object intrudes, the supply voltage to the sensor is reduced or the light emitting element or If the characteristics of the light-receiving element deteriorate, the light-receiving level of the light-receiving element changes even if an object does not enter, resulting in erroneous detection. There was something to detect.

On the other hand, in Japanese Unexamined Patent Publication No. 61-233386, a plurality of light emitting elements are turned on in a time division manner, and the incident position of the reflected light is detected by one semiconductor position detector at each time division timing. , It is necessary to calculate the incident position at each time division timing. Therefore, not only is the position calculation circuit required to operate at high speed, but after the time-division lighting and position calculation of a plurality of light-emitting elements are all completed, the presence or absence of an object can be determined again from the results of these position calculations. It had to be judged by a computer.

Therefore, the present invention can detect even when the human body is stationary, and can detect even when something other than the human body has entered, and there is a change in temperature due to sunlight irradiation. It is an object of the present invention to provide a reflection type photoelectric switch which has a simple structure and operates stably without malfunctioning even when it is turned on.

[Means for Solving the Problems]

A reflection type photoelectric switch according to the present invention includes a light projecting unit that projects a beam of light in two slits on a predetermined reference object, and a reflected light beam of the beam of light with respect to the projecting unit in a slit direction of the beam of light. Converging means for condensing into two slit-shaped spots at a position separated by a predetermined distance in the direction orthogonal to the first and second light receiving portions adjacent to each other in the direction orthogonal to the slit direction, and orthogonal to the slit direction. The three photodetectors, which are independent of each other in the direction, are provided, and the photocurrents I _{A1 ′} I from the first, second, third, and fourth photodetectors are independent of each other. _{B1 '} I
_{A2 ′} I _B2 is obtained, and a light receiving element arranged at the focusing position of two slit-shaped spots, and a photocurrent I _{A1 ′} I
_When the light receiving element receives the reflected light flux from the reference object, the light receiving element includes a detection means for detecting that the detection object has entered the front side of the reference object based on the change of _{B1 ′} I _{A2 ′} I _B2 . The photocurrent is I _A1 ≈I _{B1 ′} I _A2 ≈I _B2
So that the photocurrent is I _A1
> I _B1 and I _A2 > I _B2 , it is determined that the detection target object has entered.

Here, the light projecting means may be configured to include two light sources and a cylindrical lens having an axis in a direction orthogonal to the arrangement direction of these light sources, and a plurality of light emitting elements are arranged in parallel directions. You may make it have two groups of light sources comprised by this.

[Action]

According to the present invention, the beam light is projected in a slit shape (strip shape) and is condensed on the light receiving element as a slit spot. Here, the output photocurrents of the pair of light receiving portions (first and second light receiving portions, third and fourth light receiving portions) that are adjacent to each other are set to be substantially the same between the pairs during steady operation. When an object enters the front surface, the output photocurrents of the light receiving portions of the pair are not substantially the same, so that the intrusion of a human body or the like into this area is detected by the change of the photocurrent of the light receiving element. Therefore,
An object having the same temperature as the ambient temperature, such as a trolley, can be detected in the same manner as a human body, and is not erroneously detected even when the temperature of the reference object changes due to sunlight irradiation.

Further, even when the reflectance of the reference object changes or the amount of light emitted from the light emitting element changes, false detection will not occur. Furthermore, the determination can be made only by the ratio of the output photocurrents from the pair of light receiving portions, and there is no need to perform high-speed position calculation.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a reflective photoelectric switch according to an embodiment of the present invention. As shown in the figure, the power source unit 10 of the light sources L ₁ and L ₂ is formed by the resistors R ₁ and R ₂ and the capacitor C,
This is connected to the anode terminals of the light sources L ₁ and L ₂ . Transistors Q ₁ and Q ₂ are connected to the cathode terminals of the light sources L ₁ and L ₂ , and the light sources L ₁ and L ₂ are connected at timings T ₁ and T _2.
1 and L ₂ can be alternately pulsed. The luminous fluxes of the light sources L ₁ and L ₂ are condensed by the light projecting lens 1 on the floor (or the ground) 3 which is the reference object.
Further, this condensed light flux is made by the cylindrical lens 2.
A light beam is spread at a predetermined angle θ in a direction perpendicular to the paper surface of FIG. In other words, the floor (or the ground) 3, which is the reference object, is alternately irradiated with two slit lights at timings T ₁ and T ₂ . As a method for forming the slit light for irradiation, instead of using the cylindrical lens 3, the light sources L ₁ and L ₂ may be configured by arranging a plurality of light emitting diodes in two rows in a direction perpendicular to the paper surface.

2 and 3 show a method of arranging such light sources L ₁ and L ₂ . That is, in FIG. ₂ , the cylindrical lens 2 is combined with the _two light sources L ₁ and L ₂ , and the beam light is projected onto the reference object 3 in a slit-shaped region indicated by hatching in the drawing. There is. On the other hand, in the example shown in FIG. 3, a plurality (two groups) of light sources L ₁ and L ₂ are formed by arranging a plurality of light emitting elements in each row. And, a cylindrical lens is not provided. In this case, the spots are arranged on the reference object as shown by hatching, and it is possible to project the beam light having a substantially slit shape. The fins form substantially two linear light sources, and the light projecting lens 1 can project slit light onto an object. Actually, since the irradiation intensity can be increased by using the linear light source method as shown in FIG. 3, it is possible to stably detect the intruding object.

The light beam reflected by the floor (or the ground) 3 which is the reference object is received by the light receiving lens 4 at a position separated from the light projecting lens 1 by a distance B in the direction orthogonal to the slit direction of the slit-shaped beam light. The light is condensed in a slit shape on the light receiving element 5 having four independent light receiving portions. Here, as shown in FIG. 1, the four light receiving portions are provided adjacent to each other in the direction orthogonal to the slit direction. In the state where the two slit lights irradiating the floor (or the ground) 3 which is the reference object are not blocked by the dolly or the human body which is the detection object, the four light receiving parts (first part) of the light receiving element 5 are provided. , Second, third and fourth light receiving portions) I _{A1 '} I _B1' I _A2 and I _B2 , respectively,
The light-receiving element 5 is moved and adjusted in the arrow direction shown in FIG. 1 so that the conditions of I _A1 ≈I _B1 and I _A2 ≈I _B2 are satisfied.

That is, as shown by the solid line in FIG. 1, one of the two light fluxes reflected by the reference object 3 has a first light receiving portion whose photocurrent is I _A1 and I _B1 . Is incident on the other light flux, and the other light flux has a photocurrent of I _A2.
The light is incident between the third light receiving portion that becomes I _B2 and the fourth light receiving portion that becomes I _B2 . As a result, even when the light amount of the reflected light flux changes due to changes in the light emission amounts of the light sources L ₁ and L ₂ and the surface reflectance of the reference object 3, the above I _A1 ≈I _B1 and I _A2
The relationship of ≈I _B2 is maintained.

Therefore, when a thin mat or the like is placed on the floor 3 which is the reference object, the amount of reflected light changes, but the state of the photocurrent does not change because I _A1 ≈I _B1 and I _A2 ≈I _B2. . Therefore, even if the floor surface becomes dirty or a thin mat is laid and the amount of reflected light changes, the automatic door does not open and close and malfunction does not occur.

Next, when a dolly (or a human body) 6 shown by a chain double-dashed line in FIG. 1 as an object to be detected enters the irradiation area of the two slit lights, the reflected light flux passes through the optical path of the dotted line and the light receiving lens 4
The light is collected by and is incident on the light receiving element 5. At this time, the state of photocurrent changes from the state of I _A1 ≈I _B1 , I _A2 ≈I _{B2 to} the state of I _A1 > I _B1 and I _A2 > I _B2 . Therefore, the signal processing circuit can execute the automatic door opening / closing control by detecting the amount of change.

FIG. 4 shows an embodiment of the signal processing circuit used in the above embodiment.

The photocurrents I _{A1 ′} I _{B1 ′} I _A2 and I _B2 are current-voltage converted by the operational amplifiers U _{1 to} U ₄ , and then only the AC component is amplified. Further, it is inverted and amplified by the operational amplifiers U _{5 to} U ₈ , and I _A1 -I by the differential amplifier U ₉ ′ U _10.
B1, operation of _I A2 _{-I B2} is performed. This differential operation output is transferred to the sample and hold circuits S _{1 to} S ₄ , and the sample and hold circuit S ₁ sets the state immediately before the light source L ₁ is pulsed to the sampling time SH1.
Sample and hold with. Then, the sample and hall circuit S ₂ samples and holds the state in which the light source L ₁ is pulsed at the sampling time SH2. Similarly, the sampling and holding circuit S ₃ samples and holds the pulse lighting state immediately before the light source L ₂ is pulsed, or the sampling and holding circuit S ₄ samples and holds the pulse lighting state at sampling times SH3 and SH4, respectively.

The differential amplifier U ₁₁ calculates the output difference between the two sample and hold circuits S ₁ and S ₂ , and the differential amplifier U ₁₂ calculates the output difference between the sample and hold circuits S ₃ and S ₄ . The sample-and-hold circuits S ₁ , S ₂ , S ₃ and S ₄ and the differential amplifiers U ₁₁ and U ₁₂ select the signal component (I _A1 -I _B1) from among the photocurrents on which the disturbance light component is superimposed.
And _I A2 _{-I B2)} can be withdrawn only.

This output signal is input to active filters U ₁₃ and U ₁₄ , where high frequency components are removed. That is, due to the noise generated from the light receiving element 5 and each operational amplifier,
The voltage value of the calculation output fluctuates. This is because the signal currents I _{A1 ′} I _{B1 ′} I _A2 and I _B2 obtained from the light receiving element 5 are obtained.
This is because the weaker the value of, the larger the gain of amplification has to be, resulting in a larger voltage fluctuation. Therefore, by performing averaging of the calculated values to stabilize them, it is possible to make a reliable determination without malfunction. The averaged signal outputs I _A1 -I _B1 and I _A2 -I _B2 are comparator C
₁ and C ₂ are compared with the judgment reference voltages V _ref1 and V _ref2 . The outputs of the comparators C ₁ and C ₂ are I _A1 ≤I
_{When B1} and I _A2 ≤I _B2 , the LOW state is set, and I
_{When A1} > I _B1 and I _A2 > I _B2 , the state becomes HIGH. This judgment output is sent to the AND gate and the lower gate, and output signals OUT1 and OUT2 can be obtained respectively.

When the output signal OUT1 is used for automatic door opening / closing control,
The door will open only when both of the two slit lights are blocked. On the other hand, when the output signal OUT2 is used, the door will open if either one of the two slit lights is blocked. Therefore, it is advantageous to use the signal OUT1 in order to prevent malfunction.

FIG. 5 is a timing chart for explaining the operation of the embodiment of the present invention shown in FIGS. 1 and 4.

The light source L ₁ repeats pulse lighting at a constant cycle of T ₁ shown in FIG. The operation outputs I _A1 -I _{B1 of the} differential amplifier U ₉ shown in FIG. 4 change in synchronism with the timing T ₁ , and the states immediately before the pulse lighting and at the time of the pulse lighting are sampled by the sampling times SH1 and SH2. Differential amplifier U ₁₁
Thus, only the signal component of I _A1 -I _B1 is extracted. The light source L ₂ repeats the pulse lighting at the fixed cycle of the timing T ₂ shown in FIG. 5, similarly to the timing T ₁ . The timings T ₁ and T _{2 control} the light sources L ₁ and L _{2 so} that the light sources L ₁ and L ₂ alternately repeat the pulse lighting, so that the light sources L ₁ and L ₂ do not light simultaneously. Thereafter, similarly, only the change component of I _A2 −I _B2 is sampled at the sampling times SH3 and SH4, and only the signal component is extracted.

In the embodiment, for example, the repetition frequency in the pulse lighting operation of the light sources L ₁ and L ₂ is 1 [kHz],
The pulse width may be set to 30 [μsec], and the cutoff frequencies of the active filters U ₁₃ and U ₁₄ may be set to 10 [Hz]. As a result, the ripple (variation width) of the output voltage after averaging can be suppressed to about 1/10 of the ripple before averaging, and stable determination can be executed.

In the present invention, the output photocurrent I _A1 of the pair of light receiving portions is
And I _B1 and I _A2 and I _B2 are only determined to be the same or different from each other, so that the light sources L ₁ and L ₂ can be driven at high speed.
Even if the time-division pulse is turned on, stable determination can be executed by a simple circuit.

〔The invention's effect〕

As described above in detail, in the present invention, the beam light is projected on the slit (belt), and the intrusion of the human body or the like into this area is detected by the change of the photocurrent of the light receiving element. Therefore,
It can detect even when the human body is stationary, and can detect when something other than the human body has entered, and it also malfunctions when there is a temperature change due to sunlight irradiation. There is nothing to do.

By applying the reflection type photoelectric switch of the present invention to the opening / closing control of the automatic door, it becomes possible to detect a dolly or the like, which is impossible with the conventional pyroelectric system.

In addition, it is possible to prevent erroneous detection that occurs in the conventional reflection method. That is, even if the light emitting element or the light receiving element is deteriorated, or the reference object such as the floor is contaminated with dirt or the mat is placed, no malfunction occurs.

Further, even if the signal processing circuit is simplified and high-speed time division lighting is performed, stable operation can be guaranteed.

[Brief description of drawings]

FIG. 1 is a diagram showing an entire configuration of a reflection type photoelectric switch according to an embodiment of the present invention, FIGS. 2 and 3 are perspective views showing an example of arrangement of a light source, and FIG. 4 is related to the embodiment. A circuit diagram of the signal processing circuit and FIG. 5 are timing charts showing the operation of the signal processing circuit. 1 ... Projection lens, 2 ... Cylindrical lens, 3 ...
... reference object (floor), 4 ...... light receiving lens, 5 ...... light receiving element, 6 ...... sense target _(truck), L 1, _{L 2} ...... source.

Claims (5)

[Claims] 1. A light projecting means for projecting a light beam in the form of two slits on a predetermined reference object; and a reflected light beam of the light beam orthogonal to the slit direction of the light beam with respect to the light projecting means. Focusing means for focusing light into two slit-shaped spots at a position separated by a predetermined distance in the direction in which the first and second directions are adjacent to each other in the direction orthogonal to the slit direction.
And a second light receiving portion and four independent light receiving portions each including a third light receiving portion and a fourth light receiving portion which are adjacent to each other in a direction orthogonal to the slit direction, and each of the first, second and third light receiving portions. And the photocurrent I _{A1 ′} from the fourth light receiving unit, respectively.
I _{B1 ′} I _{A2 ′} I _B2 is obtained so as to obtain I _{B1 ′} I _{A2 ′} I _{B2, and} a change in the photocurrent I _{A1 ′} I _{B1 ′} I _{A2 ′} I _B2. A detection unit that detects that a detection target has entered the front side of the reference target, and the photocurrent is I _A1 ≈ when the light receiving element receives the reflected light flux from the reference target. I _{B1 ′} I _A2 ≈I
_B2 , the detection means determines that the detection target has entered when the photocurrent is I _A1 > I _B1 and I _A2 > I _B2. Type photoelectric switch. 2. The reflection type photoelectric switch according to claim 1, wherein the light projecting means includes two light sources and a cylindrical lens having an axis in a direction orthogonal to a direction in which the light sources are arranged. 3. The reflection type photoelectric switch according to claim 2, wherein the light projecting means includes a drive circuit for driving the two light sources in a time division manner. 4. The reflection type photoelectric switch according to claim 1, wherein the light projecting means has two groups of light sources configured by arranging a plurality of light emitting elements in directions parallel to each other. 5. The reflection type photoelectric switch according to claim 4, wherein the light projecting means includes a drive circuit for driving the two groups of the light sources in a time division manner.