JPH0227216A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To enable expansion of a detection distance range without a burden on a signal processing circuit system while permitting the alteration of a distance measuring property as desired by making a width of a position detector on the side corresponding to a long range point larger than that on the side corresponding to short range point. CONSTITUTION:A light receiving means 6 is provided at a specified distance on a side of a projecting means 3 to condense reflected light from an object to be detected of a light beam. An imaging surface of the light receiving means 6 is provided with a position detector which comprises photodiodes 8a-8c so divided that a division line thereof is slant to a direction of a condensed light spot moves when the object to be detected moves in a direction of projection. A decision control means judges whether the object to be detected exists in a specified detection area or not from outputs of the diodes 8a-8c to control an output circuit. Then, the light receiving means 6 is made up of a light receiving lens system 5 which enlarges the condensed light spot in a direction perpendicular to the direction of the condensed light spot moves to change an incidence of the division line of the diodes 8a-8c gradually while a width of the position detector on the side corresponding to a long range point is made larger than that on the side corresponding to a short range point.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a photoelectric switch for FA.

[Background Art] Conventionally, as shown in Japanese Patent Application No. 62-41006, a photoelectric switch using this type of triangulation method has been developed by combining a pair of wedge-shaped light receiving elements and a light receiving optical system using an anamorphic lens. There was one that measured the distance to the detected object.

That is, FIGS. 3 to 5 show conventional examples thereof, in which a light projecting means 3 for projecting a light beam onto an object to be detected X;
A light receiving means 6 is arranged at a predetermined distance DL to the side of the light projecting means 3 and collects the reflected light from the detected object X of the light beam.
and photodiodes 8a and 8b arranged on the image forming plane of the light receiving means 6 and divided so that the moving direction M of the condensed spot S when the detected object X moves in the light projection direction is diagonal to the dividing line. a position detection element, and a determination control means for determining whether or not the detected object X exists within a predetermined detection area based on the output of each divided photodiode 8a, 8b of the position detection element, and controlling the output circuit 16. 10, the light-receiving lens 5 of the light-receiving means 6 is an anamorphic lens that stretches the focused spot S in a direction perpendicular to the moving direction M of the focused spot S (a direction perpendicular to the plane containing the light emitting/receiving axis). was formed.

Note that the anamorphic lens is a lens that has a different curvature and focal length depending on the cross-sectional direction of the lens, and the length of the elongated line-shaped focused spot S is slightly longer than the width of the divided photodiodes 8a and 8b. It is set to be longer. In FIG. 4, condensed spots S + , S z , and S s indicate the imaging positions where the detected object X exists at distances MR, , R2, and R, respectively. Here, since an anamorphic lens is used as the light receiving lens 5 constituting the light receiving means 6, a line-shaped focused spot S is always formed on the photodiodes 8a and 8b, and this focused spot S is As shown in FIG. 4, in response to the movement of the detection object
S2. S3) It is designed to move in the M direction.

Now, when the detected object X moves in a direction crossing the optical axis, as shown in Fig. 5 b) to (c), although the overall illuminance level changes, the direction of the line length of the focused spot S changes. Since the illuminance distribution of 8 is approximately constant, both photodiodes 8
Device detection signal I A, I @ consisting of a, 8b
The ratio (IA/1.) does not change, so that a correct distance signal (for example, 1 nVA/V) is always obtained, and the judgment control means 10 does not perform erroneous judgment control. Malfunctions will not occur when X moves across the optical axis. Furthermore, the fifth
Figures (a) and (b) show a state in which a part of the light beam is reflected by the detected object X, and Figure 5 (c) shows a state in which the entire light beam is reflected by the detected object X. A condensed spot S is shown.

FIG. 6 is a diagram showing an example of the configuration of the determination control means 10,
Position detection signals IA, 1. output from the divided photodiodes 8a and 8b, respectively. The output is from the light receiving circuit 11a, l.
After being converted into voltage signals VA and V@ by lb, they are logarithmically amplified by logarithmic amplifier circuits 12a and 12b, respectively, and the logarithmically amplified signals 1nV, , 1nV are sent to subtraction circuit 1.
3, a distance signal 1n (VA/Vs) corresponding to the distance fiR can be obtained. In the comparison circuit 14, this distance signal 1n (VA/Vs
) and the reference voltage Vs set in advance with the distance setting volume VR to determine whether the detected object X has entered the detection area DE, and output the object detection signal V (for example, the distance signal 1n When (VA/Va) becomes lower than the reference voltage Vs, an object detection signal (2) is output.

This object detection signal Vx is determined by the signal processing circuit 15 as to whether it is a normal signal or not, and is outputted via the output circuit 16. Note that the light projecting 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 second clock signal and determines whether it is a normal signal or not. Further, the light receiving circuits 11a and llb are provided with a bandpass filter circuit that passes only a pulse signal of a specific frequency and cuts a DC component. In addition, in the above example, t'n(VA/V,) is calculated and used as a distance signal, but VA/V, , (V, -Vs)/(v
A+va), 1n((Vx V-)/(V-+V-)
) is calculated as a distance signal, and the determination control means 1 determines whether or not the detected object X exists within the detection area.
0 may also be formed.

[Invention tries to solve! Il! ] In the above-mentioned conventional example, since the position detection element is formed using photodiodes 8a and 8b with low internal resistance, the S/N of the position detection signal becomes high and the detection distance can be set long. Photodiode 8m, 8b
Since the sensor is divided into wedge shapes, the detection distance range can be widened.

Furthermore, since the light receiving lens 5 is formed of an anamorphic lens and the condensed spot is elongated, it is possible to prevent malfunctions when the detected object X moves in a direction crossing the optical axis. However, in the conventional example described above, the distance measurement characteristic curve is as shown in FIG. 7, and there is a problem that the detection distance range is not sufficiently wide. Therefore, it would be possible to increase the length of the position detection element, but as the length of the element increases, the parasitic capacitance increases and the S/N of the position detection signal decreases. On the other hand, when the detection distance range is widened, the dynamic range of the light reception signal at the far and near points becomes wider, and in the signal processing circuit, the light reception signal at the near point is more likely to be saturated, resulting in distance measurement errors. There is a problem that this error easily occurs, and preventing such a distance measurement error from occurring requires a burden on the signal processing circuit system.

The present invention has been made in view of the above-mentioned points, and its purpose is to widen the detection distance range without placing a burden on the signal processing circuit system, and to arbitrarily adjust the distance measurement characteristics. The purpose is to provide a photoelectric switch that can be set.

[Means for Solving the Problems] The photoelectric switch of the present invention includes a light projecting means for projecting a light beam onto an object to be detected, and a light projecting means arranged at a predetermined distance to the side of the light projecting means to project a light beam onto the detected object. a light receiving means for condensing light reflected by the light receiving means, and a photodetector disposed on the imaging plane of the light receiving means and divided so that the direction of movement of the condensed spot when the object to be detected moves in the direction of light projection is diagonal to the dividing line. A photoelectric sensor comprising a position detection element made of a diode, and a determination control means that determines whether a detected object exists within a predetermined detection area based on the output of each divided photodiode of the position detection element and controls an output circuit. In the switch, the light receiving means is formed by a lens system that stretches the focused spot in a direction orthogonal to the moving direction of the focused spot, and temporarily changes the inclination of the dividing line of the photodiode, and also adjusts the distance of the position detection element to a distant point. The width on the side is wider than the width on the side corresponding to the near point.

[Function] The present invention is configured as described above, and when the object to be detected, which is arranged on the image forming plane of the light receiving means, moves in the light projection direction, the direction of movement of the focused spot is arranged obliquely to the dividing line. In a triangulation type photoelectric switch, the photoelectric switch is equipped with a position detection element consisting of a photodiode divided into two parts, and the light receiving means is formed by a lens system that extends the focused spot in a direction perpendicular to the moving direction of the focused spot. In addition to temporarily changing the slope of the dividing line, the width of the position detection element on the side corresponding to the far point is made wider than the width on the side corresponding to the near point, thereby increasing the detection distance range without putting a burden on the signal processing circuit system. It is now possible to widen the range, and to set the distance measurement characteristics arbitrarily.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which the moving direction of the condensed spot S is divided when the detected object X, which is placed on the imaging plane of the light receiving means 6, moves in the light projection direction. A lens system (e.g., an anamorphic lens) that is equipped with a position detection element consisting of photodiodes 8a to 8C divided obliquely to the line and stretches the focused spot S in a direction perpendicular to the moving direction M of the focused spot S. In a triangulation type photoelectric switch similar to the conventional example in which the light receiving means 6 is formed with
The width la of the position detection element on the side corresponding to a long distance point (the side close to the light emitting element 1) is made wider than the width 1b on the side corresponding to a short distance point (!I (side far from the light emitting element 1)). .Here,
In the embodiment, each of the photodiodes 8a to 8c formed in a wedge shape is connected to the photodiodes 8a and 8c on both sides.
c output is connected to provide the position detection signal IA, and the central photodiode 8b output is collected as the position detection signals I and l, and the light receiving surface of the position detection element is substantially aligned in the moving direction of the focused spot S. It is divided into two parts by diagonal dividing lines. In addition, in the embodiment, the inclination of the dividing line is temporarily changed by an appropriate polygonal line, and the detection range at short distances is expanded while suppressing the increase in the distance signal 11n (VA/■,) corresponding to a long distance point. However, it goes without saying that the dividing line may be changed with a smooth curve.

Note that it is also possible to make the distance measuring characteristic curve shown in FIG. 2 linear with respect to the detection distance R by changing the dividing line with a smooth curve.

In the present embodiment, the length of the position detection element consisting of the photodiodes 8a to 8C (the length in the moving direction M of the focused spot S) is 2 mm, and the width 1a on the side corresponding to the far point is 0.
4 mm, and the width 1b on the near point corresponding side is 0.38 mm, and the dividing line whose slope is changed temporarily is set to a width of about 10 μm so that the photodiodes 8a to 8c do not electrically interfere with each other.

Here, in the embodiment, the slope of the dividing line is changed temporarily, and the distance signal 1n (VA/Vs
), it is now possible to expand the detection range at short distances while suppressing the increase in

In addition, since the width la of the position detection element on the side corresponding to a far point is made wider than the width 1b on the side corresponding to a near point, it is possible to prevent a decrease in the amount of light received when the detected object X is far away. 7
It is possible to suppress an increase in the amount of light received when the liquid detection object X is located at a short distance, so that no burden is placed on the signal processing circuit system.

FIG. 2 shows the distance measurement characteristic curve of the example.
Comparing with the distance measurement characteristic curve of the conventional example shown in the figure, in the conventional example, the detection distance range is 10 to 30 mm, whereas
In the example, the detection distance range is 5 to 30 mm, and it can be seen that the detection distance range is wider on the short distance side.

[Effects of the Invention] The present invention is configured as described above, and when the object to be detected, which is placed on the imaging plane of the light receiving means, moves in the light projection direction, the direction of movement of the focused spot obliquely intersects the dividing line. In a triangulation type photoelectric switch, the photoelectric switch is equipped with a position detection element consisting of a photodiode divided into two parts, and the light receiving means is formed by a lens system that extends the focused spot in a direction orthogonal to the moving direction of the focused spot. The inclination of the dividing line is changed temporarily, and the width of the side of the position detection element corresponding to the far point is made wider than the width of the side corresponding to the near point. This has the advantage that the range can be widened and distance measurement characteristics can be set arbitrarily.

[Brief explanation of the drawing]

Fig. 1 is a front view of main parts of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the same operation as above, Fig. 3 is a schematic configuration diagram of a photoelectric switch according to the present invention, and Fig. 4 is a front view of main parts of a conventional example. Figure 5 is an explanatory diagram of the same operation as above, Figure 6 is a main block circuit diagram of the same as above, and Figure 7 is
The figure is an explanatory diagram of the same operation as above. 3 is a light projecting means, 5 is a light receiving lens, 6 is a light receiving means, 8a~
8C is a photodiode, 10 is a determination control means, 16 is an output circuit, and X is an object to be detected. Figure 1 Agent Patent Attorney Ishi 1) Voluntary writing of amendments in the 7th procedure) September 2, 1988 Patent Application No. 177321 of 1988 2 Name of the invention Photoelectric switch 3 Relationship with the case of the person making the amendment Patent Applicant Address 1048 Kadoma, Kadoma City, Osaka Name <58
3> Matsushita Electric Works Co., Ltd. Representative: Toshio Miyoshi 11, Agent postal code: 530 5, Date of amendment order: 6, Number of claims increased by amendment: None [1] Page 12, line 3 of the specification of the present application or rmm on the 4th and 5th lines
I will correct J to rcmJ. Agent Patent Attorney Ishi 1) Choshichi

Claims (1)

[Claims] (1) A light projecting means for projecting a light beam onto an object to be detected; a light receiving means disposed at a predetermined distance to the side of the light projecting means to collect light reflected from the light beam by the object to be detected; and a light receiving means a position detection element consisting of a photodiode arranged on the image forming plane of the image plane and divided so that when the object to be detected moves in the light projection direction, the condensed spot movement direction is diagonal to the division line; and each of the position detection elements. In a photoelectric switch that serves as a determination control means that determines whether a detected object is present in a predetermined detection area based on the output of a divided photodiode and controls an output circuit, the light receiving means is arranged in a direction in which a focused spot moves. It is formed by a lens system that stretches the focused spot in a direction perpendicular to A photoelectric switch characterized by being wide.