JPH0536733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a reflective photoelectric switch that determines whether a detected object exists within a preset detection area and controls an output circuit.

[Background technology]

1 and 2 show a basic example of this type of reflective photoelectric switch. In the figures, 1 indicates a light projecting means for projecting a light beam P made of pulse modulated light onto an object to be detected X. The light emitting device is composed of an oscillation circuit 10 that generates a synchronizing signal for setting the light emitting timing, a drive circuit 11, a light emitting element 12 such as a light emitting diode or a laser diode, and a condenser lens that forms a light beam P. It is formed by an optical system 13. 2 is a predetermined distance l ₀ from the light projecting means 1
The light receiving means 1 and 2 are arranged in a triangular manner with respect to the object X to be detected.

This light receiving means 2 includes a light receiving optical system 3 consisting of a convex lens for condensing the light reflected by the detected object X.
and a position detecting means 4 which is disposed on the condensing surface of the light receiving optical system 3 and outputs a position signal corresponding to the position of the condensing spot S. This position detecting means 4 is composed of a convex lens Formed by two light-receiving elements 20a and 20b arranged in the light-condensing plane of the light-receiving optical system 3, which are arranged in series in the moving direction (arrow M) of the light-converging spot S when the distance l changes. has been done. However, a position detecting element (so-called PSD) may be used as the position detecting means 4. In the basic example, phototransistors, photodiodes, solar cells, and CdS are used as the light receiving elements 20a and 20b.
etc. are used.

5 is a discrimination control means, and based on the output of the position detection means 4, the detected object
It is designed to control the output circuit 6 by determining whether or not it is present in the output circuit. This discrimination control means 5
are the output currents I _A from the light receiving elements 20a and 20b,
Photodetector circuit 2 that amplifies and converts I _B to signal voltages V _A and V _B
1a, 21b and logarithmic amplifier circuits 22a, 22b
and a subtraction circuit 23 that subtracts the logarithmic amplifier circuit 22b output lnV _B from the logarithmic amplifier circuit 22a output lnV _A ,
The subtraction circuit 23 output ln (V _A /V _B ) is compared with the operating level V _S set by the detection area setting volume VR, and the subtraction circuit 23 output ln (V _A /V _B ) is below the operating level V _S Comparison circuit 2 outputs H level when
4 and the emission timing of the light beam P from the light emission element 12 (synchronization signal output from the oscillation circuit 10)
The signal processing circuit 25 is configured to reliably determine whether or not the detected object X exists within the detection area DE by sampling the output of the comparison circuit 24 in synchronization with the signal processing circuit 25.
The output controls an output circuit 6 consisting of a relay for load control, a semiconductor switch element for load control, etc. Note that the light receiving circuits 21a, 2
1b includes a bandpass filter circuit that passes only a pulsed optical signal, cuts a DC optical signal, or passes only a specific frequency.

Now, as shown in Fig. 3a, the detected object
b and c, the positions of the light-converging spots S with respect to the light-receiving elements 20a and 20b arranged in the light-converging plane are as shown in FIG. 3b, respectively.
When the position of the detected object X changes in the projection direction of the light beam P, the condensing spot S moves in the direction of the arrow M, and the ratio of the amount of light incident on the light receiving elements 20a and 20b changes. 20a, 20b
The output currents I _A and I _B become position signals corresponding to the position of the condensing spot S.

In the discrimination control means 5, the light receiving circuits 21a and 21b form voltages V _A and V _B proportional to the currents I _A and I _B , and the logarithmic amplifier circuits 22 a and 22 b generate logarithmically amplified voltages lnV _A and lnV _B. By subtracting in the subtraction circuit 23, the light receiving element 20a,
Logarithm value ln (V _A /
V _B ) will be output. This subtraction circuit 2
3 output ln (V _A /V _B ) changes according to the distance l from the reflective photoelectric switch Y to the detected object X, and the subtraction circuit 23 output ln (V _A /V _B ) with respect to the distance l is:
The result is as shown in FIG.

Therefore, by appropriately setting the operating level V _S with the detection area setting volume VR of the comparator circuit 24, an accurate detection area DE can be easily set.
When the output ln (V _A /V _B ) of the subtraction circuit 23 becomes equal to or higher than the operating level V _S , the output of the comparison circuit 24 becomes H level, and the output circuit 6 is activated via the signal processing circuit 25 .

In this case, the discrimination control means 5 controls the light receiving element 20
The level ratio of the outputs a and 20b is calculated, and when the level ratio is a preset operating level V _S , the output circuit 6 is activated, which is related to the level of the reflected light R from the detected object X. Since the detection area DE is set without any problem, it is possible to prevent malfunctions due to objects with high light reflectance existing behind the detection area DE, and the detection area DE is set regardless of the light reflectance of the detected object X. can be set, and furthermore, it is not affected by dirt on the optical systems 13 and 3 for projecting and receiving light.

By the way, in such a basic example, the detected object (ΔP), the light beam P hits the detected object
There was a problem in that malfunctions occurred depending on whether or not the area was completely irradiated (the P ₁ to P ₃ portions were irradiated). That is, as shown in FIG. 5a, when the light beam P is completely irradiated onto the object to be detected
The spot diameter of is x ₁ −x ₃ , and its center position is x ₂
Therefore, position signals I _A and I _B based on the center position x ₂ of the condensing spot S are output as position information corresponding to the distance l ₂ of the detected object X.

Similarly, the distance to the detected object X is l ₁ , l ₃
When the light beam P is completely irradiated on the detected object X, the center position of the converging spot S in that case is
Position signals I _A and I _B based on x ₁ and x ₃ are detected object X
is output as position information corresponding to the distances l ₁ and l ₃ . In this case, the center position x of the condensing spot S is
x=(l ₀ ×f)/l. However, f is the focal length of the light receiving optical system 3.

However, now, for example, a detected object X moving in the Z direction so as to block the light beam P is shown in FIG.
When the detection object X is located at a position such as , and only the _P1 portion of the light beam P is irradiated on the detected object The center position of Spot S is approximately
x ₁ . In this case, _position signals I _A and I _B based on the center position of the condensing spot S are output as position information of the detected object X, and this position information is Therefore, there is a problem in that the position of the detected object X is judged to be closer than the actual position.

Furthermore, when the detected object X moves to a position as shown in _FIG . The center position of S is approximately x ₃ , and the position signal I _A , based on the center position x ₃ of the focal spot S,
There was a problem in that I _B was output as the position information of the detected object X, and the detected object X was recognized as being at a distance l ₃ and was judged to be farther than its actual position. In other words, malfunctions occur when the detected object X enters and exits the light beam P.

By the way, the deviation Δx (x ₁ - x ₂ , x ₃ - x ₂ ) of the center position of the light condensing spot S is Δx = (ΔP x f)/2l, and the center position x of the light converging spot S is As shown, x=(l ₀ ×f)/l, and if (Δx/x)=(ΔP/2l ₀ ) is made small, the above malfunction can be reduced, but the difference between the light emitting means 1 and the light receiving means 2 is There are various restrictions on increasing the distance l ₀ between the two and decreasing the beam diameter ΔP, and this is not a fundamental solution.

[Purpose of the invention]

The present invention has been provided in view of the above-mentioned points, and is provided in the case where the object to be detected moves so as to block the light beam projected from the light projecting means, and the light beam has a beam diameter. The purpose is to prevent malfunctions.

[Disclosure of the invention]

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 6 and 7 show an embodiment of the present invention, which has a light projecting means 1 similar to the basic example described above, and light receiving means arranged on both sides of the light projecting means 1 at a predetermined interval _l0 . 2 ₁ and 2 ₂ are arranged. Light receiving means 2 arranged symmetrically with respect to the optical axis of the light projecting means 1
The light-receiving optical systems 3 ₁ and 3 ₂ of ₁ and 2 ₂ are designed to respectively collect the reflected light of the light beam P from the detected object X, and the light-receiving optical systems 3 ₁ and 3 ₂ Position detecting means 4 ₁ and 4 ₂ for outputting position signals corresponding to the position of the condensing spot S are arranged on the surface, respectively.

The position detecting means 4 ₁ and 4 ₂ are formed by respectively arranging a pair of light receiving elements 20 _1A , 20 _1B , 20 _2A and 20 _2B in the M direction. In the embodiment, the distances between the light receiving means 2 ₁ , 2 ₂ and the light projecting means 1 are the same, but they may be set at different intervals. In this case, the distances between the light receiving elements 20 _1A , 20 _1B , 20 _2A , 20 ₂
It may be corrected by changing the dimension of _B or by calculation by the discrimination control means 5, which will be described later. In addition, the light receiving optical system 3
₁ and 3 ₂ may intersect with the light beam P of the light projecting means 1. Furthermore, in the embodiment, the light receiving optical systems 3 ₁ and 3 ₂ , the light projecting optical system 13, and the light receiving optical system 3 Although the elements 20 _1A , 20 _1B , 20 _2A , and 20 _2B are parallel to each other, they do not necessarily have to be parallel.

The outputs of the position detection means 4 ₁ , 4 ₂ are outputted to the output circuit 6 by determining whether or not the detected object X exists within the predetermined detection area DE based on the output of the discrimination control means 5 similar to the above-mentioned basic example. Since both position detection means 4 output reciprocal position signals when a part of the light beam P is irradiated onto the detected object It is possible to correct an abnormal position signal when the detected object X is irradiated, and it is possible to prevent malfunctions when the detected object X is not completely irradiated with the light beam P.

That is, in Example 1, the light receiving element 20
The sum of the signal currents I _2A and I _1A output from the light receiving elements 2A and 20 _1A is input to the light receiving circuit 21a as a position signal I _A , and the sum of _the signal currents I _2B and I 1B output from the light receiving elements 20 _2B and 20 _1B is input to the light receiving circuit _21a . The sum is inputted to the light receiving circuit 21b as a position signal I _B , and the position signals I _A ,
Voltages V _A and V _B proportional to I _B are formed, and voltages lnV _A and logarithmically amplified by logarithmic amplifier circuits 22a and 22b,
lnV _B is subtracted by the subtraction circuit 23, and the subtraction circuit 23
The output circuit 6 is controlled by determining the distance l to the detected object X based on the output ln (V _A /V _B ).

(Operation of the Embodiment) _{Now ,} when _the detected _object The center position is _x2 , and the spot diameter of the condensing spot _S2 on the position detection means ₄₂ is _x1' - _x3 ',
Its center position is x ₂ ', and since the same position detection means 4 ₁ and 4 ₂ are arranged symmetrically with respect to the light beam P of the light projecting means 1, x ₁ = x ₁ ', , x ₂ = x ₂ ′, x ₃ =
x ₃ ′. Therefore, signal currents I _1A , I 1B , I _2A , _{I 2B} corresponding to the respective light receiving elements 20 _1A , 20 _1B , 20 _2A , 20 _2B of the position detection means 4 ₁ , 4 ₂ are output, and in this case, I _1A = I _2A , I _1B = I _2B , and the signal current
The ratio of the sum of I _1A and I _2A (2I _1A = I _A ) and the sum of signal currents I _1B and I _2B (2I _1B = I _B ), that is, V _A /V _B is,
I _1A /I _1B , the distance l to the detected object X is determined in exactly the same way as in the basic example, and the output circuit 6 is controlled.

On the other hand, when only the P ₁ portion of the light beam P is irradiated onto the detected object X, each position detection means 4 ₁ ,
The center positions of the condensing spots S ₁ and S ₂ on 4 ₂ are x ₁ ,
x ₃ ′, and the center positions x ₁ and x ₃ ′ are x ₁ =f/l(l+ΔP/2) x ₃ ′=f/l(l ₀ −ΔP/2). Here, by taking the sum I A of the signal currents I _1A and I _2A of the position detection means 4 ₁ and _{4 2} and the sum I _B of the signal currents I _1B and I _2B , x ₁ + x ₃ '=f/l ( l ₀ +P/2) + f/l(l ₀ −ΔP
/2) = 2 x (f/l) l ₀ = 2 x ₂₎ As is clear from the above equation, x ₁ + x ₃ '/2 is the detected object X. It shows the accurate distance l of the discrimination control means 5.
By calculating ln(I _A /I _B ), the position of the detected object X can be determined accurately. Similarly, even when the detected object X is irradiated with only the _P3 portion of the light beam P, the position of the detected object X can be accurately determined. ), and even when the light beam P has a constant beam diameter ΔP, the position of the detected object X can be accurately determined, and the position of the detected object Malfunctions can be prevented.

〔Effect of the invention〕

As described above, the present invention includes a light projecting means for projecting a light beam onto a moving object to be detected, and a light projecting means arranged at a predetermined interval on both sides of the light projecting means to emit a light beam from the object to be detected. First and second light-receiving optical systems that collect reflected light, and output position signals that correspond to the positions of the light-converging spots that are disposed on the light-converging surfaces of the first and second light-receiving optical systems, respectively. The first and second pair of light receiving elements and the outputs of the first light receiving element are I _1A , I _1B
Assuming that the outputs of the second light receiving element are I _2A and I _2B ,
Discrimination control means that calculates the outputs of both light receiving elements using the formula I _1A + I _2A / I _1B + I _2B , determines whether or not a detected object exists within a predetermined area based on this output, and controls an output circuit. Therefore, when the detected object blocks a part of the light beam, the abnormal position data can be corrected based on the reciprocal position signals output from the first and second pair of light receiving elements. This has the effect of preventing malfunctions even when the object to be detected moves so as to block the light beam projected from the light projecting means and the light beam has a beam diameter. It is something.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a basic example according to the present invention,
Figure 2 is the same block circuit diagram as above, Figures 3 to 5
FIG. 6 is a diagram showing the schematic structure and operation of an embodiment of the present invention, and FIG. 7 is a block circuit diagram of the same. 1 is a light projecting means, 3 ₁ , 3 ₂ is a light receiving optical system, 5 is a discrimination control means, 6 is an output circuit, 20 _1A , 20 _1B ,
20 _2A and 20 _2B are light receiving elements.

Claims (1)

[Scope of Claims] 1. A light projecting means for projecting a light beam onto a moving detected object, and a light projecting means disposed at a predetermined interval on both sides of the light projecting means to reflect the light beam by the detected object. first and second light-receiving optical systems that collect light;
A pair of first and second light receiving elements each disposed on the light collecting surface of the first and second light receiving optical systems and outputting a position signal corresponding to the position of the light collecting spot; Assuming that the outputs are I _1A and I _1B and the outputs of the second photodetector are I _2A and I _2B , the outputs of both photodetectors are calculated using the formula I _1A + I _2A /I _1B + I _2B , and the received signal is calculated based on this output. A reflective photoelectric switch comprising a discrimination control means for determining whether a detection object exists within a predetermined area and controlling an output circuit.