JP2613655B2 - Photoelectric switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an FA for detecting the presence or absence of a detected object by receiving light reflected by a detected object of a light beam projected on a detection area. The present invention relates to a photoelectric switch.

[Related Art] Conventionally, an FA that detects the presence or absence of a detected object by receiving light reflected by the detected object of a light beam projected on a detection area.
The photoelectric switch is configured using a triangulation method in order to reduce the influence of the reflectance of the surface of the detected object and the influence of the reflected light from the background. For example, FIG. 7, light emitted from the light emitting element 1 is projected to the detection area as a light beam by the light projecting lens 2, and the reflected light of the light beam from the detected object X is reflected by the light projecting lens 2. The light is condensed (forming an elongated condensed spot S) by a light receiving lens 3 composed of an anamorphic lens arranged laterally at a predetermined distance DE, and is collected when the detected object X moves in the optical axis direction. Light spot S
The light is received by a position detecting element comprising a light receiving element 4 formed by a pair of wedge-shaped photodiodes 4a and 4b divided so that the moving direction of the light receiving element 4 crosses the dividing line obliquely. There has been proposed a triangulation type photoelectric switch (Japanese Patent Application No. 62-41006) in which the presence or absence of an object is determined based on the output and the output circuit is controlled. FIG. 6 shows the condensed spots S ₁ , S ₂ , and S ₃ when the distance to the detected object X is R ₁ , R ₂ , and R ₃ .

Figure 7 shows an arrangement example of the determination control unit 5, divided photodiode 4a, a position detection signal outputted from each 4b I _A, I _B is the light receiving circuit 11a, the voltage signal V _A by 11b, after being converted into V _B, respectively logarithmic amplification circuit 12a, 12b
The logarithmically amplified signals lnV _A and lnV _B
Is subtracted by the subtraction circuit 13, so that the distance signal ln (V _A / V _B ) corresponding to the distance R is used as the distance measurement output. The comparison circuit 14 calculates the distance signal ln (V _A / V _B )
The object detection signal Vx is output by comparing with a reference voltage Vs set in advance by a distance setting volume VR to determine whether the detected object X has entered the detection area DE (for example, the distance signal ln
(When the voltage (V _A / V _B ) falls below the reference voltage Vs, the object detection signal Vx is output).

This object detection signal Vx is determined by the signal processing circuit 15 as to whether it is a normal signal, and is output via the output circuit 16. The light emitting element 1 is driven by a drive circuit 17 and emits light in synchronization with a clock signal generated by an oscillation circuit 18. On the other hand, the signal processing circuit 15 samples the object detection signal Vx based on the clock signal and determines whether or not the signal is a normal signal. Each of the light receiving circuits 11a and 11b is provided with a band pass filter circuit that passes only a pulse signal of a specific frequency and cuts a DC component. In the above example, ln
(V _A / V _B) although the distance signal by calculating the, V _A / V _{B,
(V A -V B) / (} V A + V B), and _{ln (V A -V B) /} (V A + V B) distance signal by calculating, present in the detected object X is in the detection area The determination control means 5 may be formed so as to determine whether to perform the determination.

On the other hand, there are photoelectric switches which simplify the configuration of the optical system and do not require optical axis adjustment as shown in FIGS. 8 to 11, and include a light emitting element 1, a light receiving element 4, and a signal processing means. Integrated circuit and floodlight lens 2
In some cases, the lens block 6 in which the light receiving lens 3 is integrated is directly disposed on the same circuit board 7 to simplify the assembly and adjustment of the optical axis and to reduce the size. The device for attaching the lens block 6 to the circuit board 7 is attached by inserting the protrusions 2h, 3h of each lens 2, 3 into the hole 7a of the circuit board 7 and melting the tip. . Here, both lenses 2 and 3 of lens block 6
Has an entrance lens surface and an exit lens surface that are orthogonal to each other, and the two lens surfaces are connected by a prism. In FIG. 8, 23 is a case, 24 is a front cover, 25 is a support plate, 26 is a name plate, 27a is a range setting knob, 27b is an operation mode setting knob, 28 is an O-ring, 29 is packing, 30
Is a cap and 31 is a cord.

[Problem to be Solved by the Invention] However, in the above-mentioned conventional example, both lenses 2,
The lens sides 2d, 2e, 3d,
There was a problem that a distance measurement error and a dead zone were generated due to unnecessary light reflection by 3e. For example, of the light emitted from the light emitting element 1, light passing through the incident lens surface 2a, the prism surface 2c, and the exit lens surface 2b is projected as the main beam light P, but is reflected by the lens side surfaces 2d to 2g. , Twelfth
As shown in the figure, four sub-beams P ₁ ′ to P ₄ ′ are projected. When the reflected light of the detected object X of the sub-beam light P ₁ ′ reflected on the lens side surface 2 d of the sub-light beams P ₁ ′ to P ₄ ′ is received by the light receiving lens 3, for example,
As shown in FIG. 13, two condensed spots S and S 'are formed on the position detecting element, and the actual distance (R ₃ ) to the detected object X is equal to the distance between the two condensed spots S and S'. It will be erroneously determined distance corresponding to the center of gravity position of the light energy (distance between R ₁ and R _3).

Similarly, in the light receiving lens 3, the lens side surface 3d
~ 3g reflection, diffused light will cause flare,
The flare light is irradiated onto the position detecting element with a light distribution. This flare light increases as the detected object X approaches, and the relationship between the distance R and the distance measurement signal lnV _A / V _B is as shown in FIG. Here, at a short distance equal to or less than R ₀ , the problem is that the distance signal ln (V _A / V _B ) rises due to the flare light. Such a distance signal lnV _A /
V _B makes it impossible to judge the distance less than R ₀ and the distance R
There is a problem that an erroneous determination may be made even in the case of ₁₀ or less.

The present invention has been made in view of the above points, and an object of the present invention is to provide a photoelectric switch capable of preventing a distance measurement error or a dead zone caused by light reflected from a light projecting side of a light receiving lens. To provide.

[Means for Solving the Problems] The photoelectric switch of the present invention projects light emitted from a light emitting element as a light beam to a detection area by a light projecting lens, and receives reflected light of the light beam from a detected object. The light is condensed by the lens, and the movement of the condensed spot when the detected object moves in the optical axis direction is detected by the position detecting element, and the judgment control means detects the movement of the object based on the output of the position detecting element. A triangulation-type photoelectric switch in which an output circuit is controlled by determining the presence / absence of a light emitting element, a position detecting element, and a signal processing means, and a light emitting lens and a light receiving lens are integrated with a circuit board. In a photoelectric switch, a lens block is disposed, and an entrance lens surface and an exit lens surface have a lens surface orthogonal to each other, and both lenses are connected by a prism to form both lenses. Also floodlight,
An unnecessary light reflection preventing prism for preventing reflection of unnecessary light is integrally formed on a lens side surface perpendicular to a surface including a light receiving axis.

[Operation] The present invention is configured as described above, and is a triangulation type photoelectric switch, in which a light emitting element, a position detecting element, and a circuit board on which signal processing means are mounted, in which a light projecting lens and a light receiving lens are integrated. In a photoelectric switch having an integrated lens block and an entrance lens surface and an exit lens surface having a lens surface orthogonal to each other and connecting both lenses with a prism to form both lenses, at least light is projected. A prism for preventing unnecessary light reflection is formed integrally on the side of the lens perpendicular to the plane containing the light receiving axis. Distance measurement due to light reflected by the lens side of the light projecting and light receiving lens An object of the present invention is to provide a photoelectric switch capable of preventing occurrence of an error or a dead zone.

[Embodiment] FIG. 1 shows an embodiment of the present invention. As in the prior art, an integrated circuit 8 integrating a light emitting element 1, a light receiving element 4 and signal processing means, a light projecting lens 1 and A lens block 6 integrated with a light receiving lens 3 is directly disposed on the same circuit board 7, and an entrance lens surface and an exit lens surface are orthogonal to each other, and the two lens surfaces are connected by a prism to form both lenses 2, 3. In the photoelectric switch, the light emitting lens 2 and the light receiving lens 3
Unnecessary light reflection preventing prism P for preventing reflection of unnecessary light on a lens side surface perpendicular to a plane including at least the light projecting and light receiving axes.
Are integrally formed.

FIG. 2 shows the means for blocking various kinds of unnecessary light and the measurement results of the ghost ratio G. In this embodiment, the prism P having the shape of (u) in this embodiment is painted black on the side surface of the lens. , A remarkable effect of suppressing reflected light (the ghost ratio G is small) is obtained. Also,
In the case of forming a prism on the side surface of the lens, the prism formed with a pedestal (a) and (b) has a more suppressed effect of reflected light than the prism formed only (g) and (h). The result is that the greater the vertex angle of the prism is farther than the side surface of the lens, the greater the effect of suppressing reflection can be obtained. Here, the ghost ratio G is obtained by dividing the amount of received light at a distance of 5 mm (or 10 mm) by the amount of received light at a distance of 100 mm.

In order to reduce the ghost ratio G by suppressing the reflected light, it is most effective to apply black paint to the lens side surface 2e. However, as in the present invention, a prism for preventing unnecessary light reflection is provided on the lens side surface 2e. If P is integrally formed, the two lenses 2 and 3 can be integrally formed at the time of molding, so that the manufacturing process can be simplified and the cost can be reduced. Also, it is conceivable to attach a black seal instead of black painting,
Since a problem occurs in the adhesion, the reflection suppressing effect is hardly obtained.

FIG. 4 shows another embodiment, in which a light receiving element 4c for flare compensation is provided outside the moving range of the converging spot S corresponding to the case where the detected object X moves within the distance measuring range. , and the have less occurrence of errors in distance measurement and the dead zone due to flare light by correcting the distance signal lV _a / V _B in the conventional example by the light receiving element 4c output.

That is, the pair of the position detection signal I _A output from the light receiving element 4, the (I _B in this embodiment) one of the I _B, the light receiving element 4
_{'and, ln (V A / V B} ' signal I _B obtained by adding the c output I _C) a distance signal (however, V _B 'is I _B' value converted I-V a) by a distance signal The short distance portion of ln (V _A / V _B ′) is corrected as shown by the one-dot chain line b in FIG. 3, so that the occurrence of the distance measurement error and the dead zone caused by the flare can be eliminated.

[Effects of the Invention] The present invention is configured as described above, and is a triangulation-type photoelectric switch, in which a light-emitting element, a position detection element, and a light-receiving lens are mounted on a circuit board on which signal processing means are mounted. In a photoelectric switch comprising an integrated lens block, an entrance lens surface and an exit lens surface having a lens surface orthogonal to each other, and both lenses connected by a prism to form both lenses, at least A prism for preventing unnecessary light reflection is formed integrally on the side of the lens perpendicular to the plane including the light projecting and receiving axes, which is caused by light reflected by the lens side of the light projecting and light receiving lens. It is possible to prevent distance measurement errors and the generation of dead zones.
Since the light receiving lens can be integrally provided on the side surface of the lens at the time of molding the lens, there is an effect that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of an essential part of one embodiment of the present invention, FIGS. 2 and 3 are operation explanatory views of the same embodiment, FIG. 4 is a schematic configuration diagram of another embodiment, and FIG. FIG. 6 is a schematic diagram illustrating the operation of the photoelectric switch, FIG. 7 is a block circuit diagram of the same, FIG. 8 is an exploded perspective view of a conventional example, and FIGS. 9 and 10 (a) and (b). ) Is a cross-sectional view of the main part of the above, FIG. 11 is a perspective view of the main part of the same, and FIGS. 12 to 14 are operation explanatory diagrams showing the problems of the above. 1 is a light emitting element, 2 is a light projecting lens, 3 is a light receiving lens, 4 is a light receiving element, 4a and 4b are photodiodes, 5 is a discrimination control means, 6 is a lens block, 7 is a circuit board, and P is unnecessary reflected light blocking. Prism.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 31/0232 H01L 31/02 D

Claims (1)

(57) [Claims] The light emitted from the light emitting element is projected by a light projecting lens as a light beam to a detection area, and the reflected light of the light beam from the object to be detected is condensed by a light receiving lens. The movement of the condensed spot when the object moves in the optical axis direction is detected by the position detection element, and the determination control means determines the presence or absence of the object based on the output of the position detection element and controls the output circuit. In a triangulation photoelectric switch, a light emitting element, a position detecting element and a signal processing means are mounted on a circuit board, and a lens block in which a light projecting lens and a light receiving lens are integrated is disposed. In a photoelectric switch having a lens surface perpendicular to the exit lens surface and connecting both lenses by a prism to form both lenses, a lens side surface perpendicular to a surface including at least the light projecting and light receiving axes Photoelectric switch, characterized in that formed integrally unwanted light reflection blocking prism to prevent the reflection of unnecessary light.