JPS6199229A - Reflection type photoelectric switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a reflective photoelectric switch.

[Background of the invention]

FIG. 3 shows the configuration of a conventional reflective photoelectric switch.

In FIG. 3, a photoelectric switch 1 includes a light projecting element 2, a light projecting part 4 including a lens 3, a light receiving part 7 including a light receiving lens 5 and a light receiving element 6, and a light projecting part 4 including a light receiving lens 5 and a light receiving element 6. and a control circuit 8 that controls the light receiving section 7 and processes detection signals.

In such a photoelectric switch 1, the light receiving optical system receives the maximum amount of reflected light from the detection object 10 located at the maximum detectable distance (nominal maximum detection distance) on the optical axis 11 of the light projector 40. It is generally designed so that That is, the direction of the optical axis 12 and the light receiving lens 5 of the light receiving section 7 are selected so that the image of the detection object 10 is focused on the light receiving surface of the light receiving element 6.

In the conventional reflective photoelectric switch 1 designed as described above, when the detection distance on the optical axis 11 is changed and the change in the amount of light received by the light receiving element 6 is measured, the characteristics shown in FIG. 4 are obtained. This is because the first effect is that the amount of light received changes in inverse proportion to the square of the detection distance on the optical axis 12 of the light receiving section, and the second effect is that the amount of light received changes as the image of the detection object 1o deviates from the light receiving surface. This is due to a combined effect with the second effect. As mentioned above, the light receiving section 7 is designed so that the amount of light received is maximum at the nominal maximum detection distance. Therefore, when the detection object is at a close position as shown by 1σ, for example, the reflected light from it is 13 deviates from the optical axis 12 of the light-receiving part, and the image of the detection object 10' is formed at a position shifted from the original position of the light-receiving element 6, as shown by 6'. 6's output level decreases. In other words, as can be seen from curve 23 in Figure 4, in the range where the first effect is dominant, the amount of light received increases as the detection distance decreases, but as the detection distance further decreases, the second effect becomes dominant. When the detection distance reaches a certain range, the amount of received light decreases as the detection distance decreases, and below a certain detection distance, the amount of received light becomes less than the detection level 22, forming a dead zone 21. In this case, the second effect becomes even more remarkable when the projected beam is focused narrowly for the purpose of detecting minute objects.

In conventional reflective light chamber switches, when changing the detection distance, the width of the dead zone 210 described above is changed to achieve the optimum detection characteristics.
The positional relationship between the light emitting optical system and the light receiving optical system has been adjusted using a mechanical method, but this method complicates the internal structure due to the adjustment mechanism, making it difficult to downsize and increasing costs. There was a problem.

[Purpose of the invention]

The present invention solves the above-mentioned problems of the prior art, and provides a reflector that makes it possible to change the dead zone when changing the detection distance at low cost and easily by adding simple external parts without complicating the internal structure. The present invention aims to provide a shaped light chamber switch.

[Structure and effects of the invention]

In order to achieve the above-mentioned object, the reflective light chamber switch of the present invention is provided with a removable optical component 9 for changing the focal length of the optical path between the light emitting part and the light receiving part. Maximum sensitivity can be obtained at different sensing distances when optical components are installed and removed, and when changing the sensing distance, optimal sensing characteristics can be obtained at the dead band width corresponding to each sensing distance. It is something that becomes.

In the present invention, for example, a prism or a lens can be used as the optical component, and this may be attached to the light projecting section, the light receiving section, or both so as to be able to project an image.

By preparing these optical components with various focal lengths and optical path change angles as so-called atanochimenets, the detection area width as a photoelectric switch can be varied in various ways without being limited by a dead zone. ] FIG. 1 shows an embodiment of the present invention, in which a reflective light chamber switch 1 includes a light projecting section 4 including a light projecting element 2 and a light projecting lens 3, and a light receiving lens 5 and a light receiving element 6. Light receiving section 7
A control circuit 8 controls the light emitting section 4 and the light receiving section 7 and performs detection signal processing, and an acnotiment prism 9 is removably attached to the front surface of the lens of the light receiving section 7. Be prepared. In Fig. 1, 11 is the optical axis of the light projector, 1
2 is the optical axis of the light receiving section, 10 is the detected object at the position of the nominal maximum detection distance when prism 9 is removed, 1σ is the detected object at a position closer to the light emitting section, and 13 is the object lO
It is struck by the rays reflected by ′.

As a characteristic of the photoelectric switch 1 without the prism 9 attached, the light receiving portion 7 is set so that the amount of light reflected from the detection object 1o located at the nominal maximum detection distance position on the optical axis 11 is maximized. An optical system 9 is designed, and when the prism 9 is attached to the front of the lens of the light receiving section 7, the detection distance (nominal maximum detection distance) that is close to the light emitting section 4 is determined.
It is designed so that an image of the detection object 10' located at the position is formed at or near the detection object 10 when viewed from the light receiving element 6.

FIG. 2 shows the results of measuring changes in the amount of light received by the light receiving element 6 by changing the detection distance on the optical axis 11 using the reflective light chamber switch of this embodiment.

In FIG. 2, 22 is a detection level threshold value in the control circuit 12, a curve 23 is a change in the amount of received light when the prism 9 is not attached, and a curve 24 is a change in the amount of received light when the prism 9 is attached. When the prism 9 is not attached, it is the same as the conventional example shown in Fig. 3, and the highest sensitivity is obtained with the detection object 10 located at the nominal maximum detection distance, and the dead zone in that case is 2.
1. On the other hand, when the prism 9 is attached, the dead zone becomes narrower as shown by 25, and the position where maximum sensitivity is obtained is also closer to the nominal value. This also provides the effect of reducing the influence of background objects (for example, the inner wall of the detection chamber, etc.) that are often located nearby when detection is performed at a position closer than the nominal value.

In the illustrated embodiment, a prism 9 is used as the optical member, but a prism cannot improve the image size or blurring, so if you want to improve these as well, use a lens instead of the prism. A system that uses a combination of a prism and a lens can be used.

Furthermore, although the light-receiving section 7 is shown as having a light-receiving lens 5, the light-receiving section without a light-receiving lens may be replaced with an external lens depending on the detection distance, or alternatively, an external lens may be attached to the light-receiving section without a light-receiving lens. Of course, it is also possible to apply the focusing optical path changing optical member such as a prism or lens to the light projecting section, or to apply it to both the light receiving section and the light projecting section.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of the present invention, and FIG.
The figure is a detection characteristic line diagram, FIG. 3 is a block diagram schematically showing a conventional example, and FIG. 4 is a detection characteristic line diagram thereof. Reflective type 4 photoelectric switch, 2: Light emitter, 3: Light emitter lens, 4: Light emitter, 5: Light receiver lens, 6: Light receiver, 7:
Light receiving section, 8: Control circuit, 9 Nigelism, 10. 10' Two detection objects. Patent applicant: Tatsuo Ito, agent of Tateishi Electric Co., Ltd., patent attorney
1 agent Patent attorney Tetsuya Ito Figure 1 Figure 2 Me Bare [Also, +-+ Kenjo ℃ 1,000 p3 E-1 Figure 3

Claims (1)

[Claims] 1. In a reflective photoelectric switch in which a light receiving section detects light reflected by an object detecting light from a light projecting section, an optical component that changes the focal length of the optical path between the light projecting section and the light receiving section. A reflective photoelectric switch characterized by a removable reflective switch. 2. The reflective photoelectric switch according to claim 1, wherein the optical component includes a prism. 3. A reflective photoelectric switch according to claim 1, wherein the optical component includes a lens. 4. The reflective photoelectric switch according to claim 1, wherein the optical member is attached to the light projecting section. 5. The reflective photoelectric switch according to claim 1, wherein the optical member is attached to the light receiving section.