JPS6270709A - Reflection type photoelectric switch - Google Patents

Abstract

PURPOSE:To make it possible to alter a detection area to a large extent by widening a range-finding range, by changing the optical relative position of a position detecting means. CONSTITUTION:A one-dimensional position detecting element of a position detecting means 4 is constituted so that the optical relative position to a light emitting optical system 13 and a light receiving optical system 13' is changed by making the position of said detecting element freely movable to the direction shown by an arrow (m). When a detection area is desired to be set in front of a detection distance 1a, the detecting means 4 is placed at the position shown by a solid line. When a detection distance is 1b and the detection area is desired to be set in front of said distance 1b, the detecting means 4 is slid to the direc tion shown by the arrow (m) to be placed at the position shown by a dotted line. By this method,the detecting means 4 having the same length is used with out elongating the effective length 1p of the one-dimensional position detecting element to make it possible to widen a range finding possible range without lowering range finding accuracy. Further, the detection area can be altered to a large extent without lowering detection capacity.

Description

Detailed Description of the Invention [Technical Field 1] The present invention is directed to a method in which a light receiving means receives reflected light from an object to be detected of a potential beam projected from a light projecting means to a detection area, and detects the light based on the output of the light receiving means. This invention relates to a reflective photoelectric switch that detects the presence or absence of an object to be detected within an area.

[Background Art 1 Conventionally, this type of reflective photoelectric switch uses a light receiving means to receive the reflected light from the object to be detected of the light projected onto the detection area from the light projecting means, and to determine the magnitude of the amount of reflected light from the object to be detected. Some reflective photoelectric switches are designed to determine the presence or absence of a detected object by There was a 171J problem in which a distance measurement error occurs in different cases, resulting in malfunction (detection ffl changes). Therefore, the inventors filed a patent application filed in 1973 to create a reflective photoelectric switch that prevents such a one-back operation.
There is a triangulation system that has been filed as No. 8-14163. In other words, this reflective photoelectric switch is as shown in Fig. 5 and Fig. 6.
1. :, the light projecting means 1 for projecting the light beam P toward the light projecting device 1 includes an oscillation circuit 10 that generates a clock pulse for setting the light projecting timing, a drive circuit 11 that drives the light emitting element 12 for projecting light, and a convex lens. The light emitted from the light emitting element 12 is shaped into a light beam P by the light projecting optical means 13, and the light is projected onto the detection area. A predetermined distance α from the light projecting means 1. A light-receiving optical system 2, which is disposed laterally and collects the reflected light R of the light beam P by the detected object X, is formed of a convex lens.

A condensing spot S is arranged on the condensing surface of the light receiving optical system 2.
The position detecting means 4 that outputs the position signal I A, I corresponding to the position (moving in the direction ■ corresponding to the distance C) is formed of, for example, a one-dimensional position detecting element (PSD). This output signal is a contradictory signal.

Based on the output of this position detection means 4, it is determined whether or not the detected object X exists within a predetermined detection area, and an output circuit 6
The discrimination control stage 5 includes a light receiving circuit 21a that amplifies the position signals (contradictory current signals 1x, Io) outputted from the position detecting means 4 and converts them into voltage signals VAYVQ; 21b, and light receiving circuits 21a, 21b
Logarithmic amplifier circuits 22a and 22b that logarithmically amplify the output, and logarithmic amplifier circuit 22a.

22b The subtraction circuit 23 calculates the difference between the output QnVA+αnV1, and compares the output α''VA/V of the subtraction circuit 23 with the base'$ main voltage s set by the distance setting volume VR. As shown in Fig. 8, when the output αIIVA/V is less than the reference voltage Vs (when the detected object Malfunctions are prevented by checking the ratio flil path 24 and the comparison circuit 24 output based on the oscillation circuit 1 output (determining the level in synchronization with the clock pulse). When an object detection signal is output from the signal processing circuit 25, the output circuit 6 is driven.

In addition, in FIGS. 7(a), 7(b), and 7(c), the distance to the detected object X is α7. The positions of the condensed spots S on the position detection means 4 in the case of α are shown respectively. Mako, instead of the above-mentioned one-dimensional position detection element, 2
Position detection T=
It goes without saying that it may also be used as stage i.

Here, in this conventional example, the discrimination control means 5 detects the position of the condensed spot S by the position detection means 4 and discriminates whether or not the detected object X exists within the detection area. Therefore, the detection operation can be performed regardless of the level of the reflected light R, even if there is an object with high reflectance behind the detected object X or the reflectance of the detected object X changes. It is designed to prevent malfunctions (no distance measurement errors). By the way, in such a conventional example, the detection area can be electrically changed by changing the reference voltage Vs using the distance setting volume VR, but it is possible to widen the distance measurement range without reducing the distance measurement accuracy. There was a problem in that the detection area could not be changed significantly. That is, the distance measurement accuracy in this type of reflective photoelectric switch using the triangulation method as the distance measurement method is determined by the ratio L/M of the movement amount M of the condensed spot S on the position detection means 4 and the measurable range L/M. The smaller the ratio L/M, the higher the distance measurement accuracy. Here, when trying to widen the measurable range without lowering the distance measurement accuracy, it is possible to move the focused spot S by using a one-dimensional position detection element with a long effective length IJp of the light receiving part as the position detection means 4. It is conceivable to increase iM, but increasing the effective length αp will increase the quantum noise of the one-dimensional 1d detection element that is the position detection means 4 (especially the condensing tube 7) when S becomes weak light. This has the disadvantage of slowing down the response speed and making it impossible to expand the measurable range, that is, the range in which the detection distance can be changed, without reducing the distance measurement accuracy. The problem was that it could not be changed to .

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to be able to widen the measurable range without reducing the distance measurement accuracy, and to widen the detection area. An object of the present invention is to provide a reflective photoelectric switch that can be changed significantly.

(Disclosure of the Invention) (Embodiment 1) FIG. 1 shows an embodiment of the present invention, in which a reflective photoelectric switch similar to the conventional example described above has a light emitting element 12 for projecting light.
, a detection area setting means is provided for setting the detection distance of the detection area by changing the relative positions of the light emitting optical system 13, the light receiving optical system 2, and the position detection means 4. In this case, the position of the one-dimensional position detecting element, which is the position detecting means 4, is movable in the direction of the arrow m, and the optical relative position of the position detecting means 4 with respect to the light projecting means 1 and the light receiving optical system 2 is changed. Area setting means is formed. Note that as the moving means for the position detector fi4 and the IVA constant movement stage, a general slide fixing means or a variable fixing means in which a plurality of fixing positions are set in advance may be used, and a detailed explanation of the configuration will be omitted. It is also input to the comparison circuit 24 of the discrimination control means 5, which is an essential component of the conventional example! Distance setting volume V R for changing the A quasi voltage Vs
is unchanged, and the reference voltage Vs is set to a predetermined fixed value (for example, V
Needless to say, it is set to s"O).

Now, the reference voltage S of the comparator circuit 24, which is a fixed value, is V
q: 0, and if you want to set the detection area on the 1111 side of the detection distance Qa, you can place the position detection means 4 at the position shown by the solid line in FIG. 1. In this case, The detection distance 9a is the distance B"C at which the device detection signals ■9 and Ill constituted by the position detection means 4 have the same value (IA/l8=1) when the detected object X exists at that position. Also, if the detected Mlj distance is Qb and you want to set the detection area in one direction, slide the position detection means 4 in the direction of the arrow The position detection means 4 may be placed at a certain position, and the optical relative position of the position detection means 4 with respect to the light emitting element 12 for light emission, the optical system i13 for light emission and the optical system 2 for light reception may be changed. The measurable range can be expanded (shifted) using his position detecting means 4 without increasing the effective length α1) of the one-dimensional position detecting element, which is the detecting means 4, as in the conventional example. It is possible to widen the measurable range without reducing distance accuracy, and it is now possible to significantly change the detection area without reducing detection ability.

In addition, as in this embodiment, the detection distance is 0. When setting a and ηb so that the position detection signals IA and 1B have the same value, the logarithmic amplifier circuits 22a and 22b and the subtraction circuit 23 of the discrimination control means 5 in the circuit example shown in FIG. For short, as shown in FIG. 2, the light receiving circuits 21a and 21b
The outputs ■6 and \lB may be directly compared in the comparison circuit 24, and it may be determined whether or not the detected object X exists within the detection area based on the magnitude of the comparison.In this case, the circuit configuration is simplified. This means that costs can be reduced.

In addition, in the case of this embodiment, since the center of the light receiving range of the position detecting means 4 is the detection distance, that is, the far point of the detection area, the adjustment range of the distance setting volume VR and the position detecting means 4 are different from each other, as in the conventional example. (The position of the position detector ￥4, and the adjustment of the distance setting volume VR so that the near-sighted point of the detection distance is set to operate safely even if the signal processing circuit is saturated) The position of the position detection means 4 can be changed to fi! without the need for adjustment work such as setting the adjustment range or making the distance scale of the distance setting volume VR correspond to the far point of the detection area. A desired detection area can be set simply by making four adjustments, which has the effect of simplifying assembly work.

(Example 2) Figure f:tS2 shows an example of a reflection type photoelectric switch similar to the conventional example described above, in which a rotatable plane mirror is provided in the optical path of the light receiving JIJ optical system 2. This forms a detection area setting means, and by rotating the plane mirror 3 about the rotation axis 3a, the light emitting cable 12 for light projection, the optical system 13 for light projection, and the optical system for light reception are set. The optical relative position of the position detection means 4 with respect to the system 2 is changed.

In this embodiment, the optical relative positions of the light emitting element 12 for projecting light, the optical system 13 for projecting light, the optical system 2 for light receiving and the position detecting means 4 are adjusted by adjusting the angle of the plane mirror (). It is now possible to arbitrarily set the detection distance of the detection area by changing the detection area, and as in Example 1 above, the detection area can be changed significantly without reducing the distance measurement accuracy. In addition, unlike in Example 1, there is no need to move the printed circuit board on which the circuit elements are mounted, so there is no need for flexible wiring, which simplifies the configuration and reduces costs. This makes it possible to improve reliability.

(Embodiment 3) FIG. 3 shows still another embodiment, in which the light receiving optical system 2 is made movable to form a detection area setting means, and the light emitting element 12 for light emitting, The relative optical positions of the optical system 13, the light-receiving optical system 2, and the position detection means 1 are changed, and the measurable range is widened without reducing the accuracy of the distance measurement, as in the previous embodiment. The detection area can be changed significantly, and assembly and adjustment are easy.

Now, when setting the detection area with the detection distance Qb,
The light receiving optical system 2 consisting of a convex lens may be arranged as shown by the solid line, and when setting the detection area of the detection distance αa, the light receiving optical system 2 may be slid to the position shown by the straight line. The detection area can be easily changed by simply sliding the light receiving optical system 2. By the way, the distance measurement accuracy using the triangulation method is
The better the separation distance Qo between the light emitting optical system 12 and the light receiving optical system 2 is, the higher the distance Qo becomes, but in this embodiment, when the detection distance is set long, the separation distance Qo increases.

This is advantageous because it naturally increases the distance measurement accuracy.

Although not illustrated as an example, the same detection area setting means as in the first to third embodiments can be formed even if the light emitting element 12 for light projection or the optical system 13 for light projection of the light projection means 1 is made movable. Needless to say, the operation is as in Example 1,
This is the same as in the third embodiment. In addition, the light projection optical system 13
The optical block consisting of the light-receiving optical system 2 and the circuit block including the light emitting cable 12 and the position detecting means 4 are connected with an optical fiber, and the detection head is made into a small-sized reflective photoelectric switch. In this case, the optical system side end of the 7r fiber can be regarded as the installation position of the light emitting cable 12 for light emitting and the position detecting means 4 for the optical fiber for light emitting and the optical fiber for receiving light in both parties. The relative positions of each end of the light emitting optical system 13 and the light receiving optical system 2 may be freely adjusted so that the detection area can be changed.

[Effect of the Invention 1] As described above, the present invention comprises a light projecting means for forming a light beam emitted from a light emitting element into a light beam by a light projecting optical system and projecting the light onto a detection area; a light-receiving optical system that is arranged laterally at a predetermined distance from the object to be detected and that collects the reflected light of the light beam from the object to be detected; 1 = 1 pin 2l in the position 7 of the focal spot moving within the focal plane? , if Xi signal, middle 1
A reflective photoelectric device equipped with a power detection means and an ell discrimination means that determines whether a detected object exists within a predetermined detection area based on the output of the position detection means and controls an output circuit. In the switch, the detection area can be detected by changing the optical relative positions of the light emitting element, the light emitting optical system, the light receiving optical system, and the position detection means! li
Since it is equipped with a detection area setting means for setting the distance, it is possible to widen the distance measurement range without reducing distance measurement accuracy, and the detection area can be changed significantly without reducing object detection ability. effective.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of the main parts of one embodiment of the present invention, FIG. 2 is a block circuit diagram of the main parts of another embodiment, FIG. 3 is a schematic block diagram of the main parts of another embodiment, and FIG. 4 5 is a schematic diagram of the main part of another embodiment, FIG. 5 is a schematic diagram of the main part of the conventional example, and FIG.
The figure is a block circuit diagram same as the above, and FIGS. 7 and 8 are operation explanatory diagrams same as the above. 1 is a light projecting means, 2 is a light receiving optical system, 4 is a position inspection means,
5 is a discrimination control means, 6 is an output circuit, 12 is a light emitting element for projecting light, and 13 is an optical system for projecting light. Agent Patent Attorney Ishi 1) Chief Figure 7 4

Claims (1)

[Claims] (1) A light projecting means that shapes the light emitted from the light projecting light emitting element into a light beam using a light projecting optical system and projects the light onto a detection area;
a light-receiving optical system disposed at a predetermined distance to the side of the light projecting means and condensing the reflected light of the light beam from the detected object; and a light-receiving optical system disposed on the converging surface of the light-receiving optical system at a distance to the detected object. a position detection means that outputs a position signal corresponding to the position of a condensed spot that moves within a condensing plane according to Changing the optical relative positions of a light emitting element for light emission, an optical system for light emission, an optical system for light reception, and a position detection means in a reflective photoelectric switch equipped with a discrimination control means for discriminating and controlling an output circuit. A reflective photoelectric switch characterized by being provided with a detection area setting means for setting a detection distance of a detection area.